Search

Welsh Anaesthetic Trainees Journal Club

Tag

goal-directed fluid therapy

Goal directed fluid therapy. What works?

Normal saline versus a balanced crystalloid for goal-directed perioperative fluid therapy in major abdominal surgery: a double-blind randomised controlled study

British Journal of Anaesthesia 2018;120(2):274-283

Presented by: Dr I Rees

Background

  • Normal saline 0.9% amongst most commonly used crystalloid for fluid therapy
  • However normal saline not ‘normal’
    • Sodium and chloride concentrations 154mmol/l
    • Risk of hyperchloraemic metabolic acidosis and reduced anion gap
    • Linked to increased risk of renal dysfunction, transfusion and mortality in patients undergoing abdominal surgery
  • Balanced crystalloids contain metabolisable anions (lactate or acetate)
    • Maintain electrolyte stability
    • Less associated with metabolic acidosis
    • Metabolised to bicarbonate
  • Recent study in same centre demonstrated patients undergoing cadaveric renal transplantation required significantly less catecholamine support if receiving balanced crystalloid, compared to the group receiving normal saline
  • Authors hypothesised that patients undergoing major surgery might require less vasopressor support if they received a balanced crystalloid, as opposed to normal saline perioperatively

Design & Setting

  • Single-centre (Department of Anaesthesiology of the Medical University of Vienna, Austria)
  • Prospective double-blinded randomised controlled study of patients undergoing elective major abdominal surgery
  • Patients and anaesthetists blinded
  • Ethics approved
  • Sample size calculated (based on previous transplantation study) – 120 patients per group (240 total) to give α 5% and 80% power

Subjects

Inclusion criteria:

  1. Adult, non-pregnant patients
  2. Undergoing elective major abdominal surgery (any general, gynaecological or urological procedure requiring laparotomy)

Exclusion criteria:

  1. LV ejection fraction <30%
  2. Renal dysfunction (GFR <30ml/min) and severe liver disease
  3. Chronic inflammatory diseases requiring long-term steroids
  4. Pre-operative sepsis or critical care patients
  5. Contraindications to oesophageal doppler
  6. Intraoperative epidural analgesia

Intervention

  • Patients randomised on day of surgery to receive either normal saline or a chloride-reduced acetate-buffered balanced crystalloid (Elomel Isoton)
  • No pre-operative fluid infusion
  • Blinded fluids given to anaesthetist before induction of anaesthesia
  • Standardised anaesthetic:
    • Standardised induction (propofol 2-3mg/kg, rocuronium 0.6mg/kg and fentanyl 2-3mcg/kg)
    • Standard monitoring including arterial line and CVP + depth of anaesthesia monitoring (Narcotrend), train-of-four ulnar montoring and oesophageal doppler (CardioQ)
    • Sevoflurane administration according to Narcotrend; FiO2and fentanyl boluses according to clinical requirement; Rocuronium to maintain one or two twitches on TOF
    • Ventilation to maintain end-tidal CO2 near 35mmHg (~4.6kPa) – tidal volume 8-10ml/kg (LBW), peak pressure <30mmHg (~40cmH2O) and PEEP of 5mmHg (~7cmH2O) or higher according to patient need.
    • Temperature >36oC using forced air warmer and hourly arterial blood gases
    • Fluid maintenance 2ml/kg/hr (IBW as per Robinson’s formula) increased to 5ml/kg/hr on exposure of viscera
  • Target MAP according to pre-operative blood pressure the day before surgery:
Pre-operative Blood Pressure (mmHg) Intraoperative Target MAP (mmHg)
Hypotensive SBP <120 60
Normotensive SBP 120-139 / DBP 80-89 70
Hypertensive SBP >140 / DBP >90 80
  • If MAP fell, standardised protocol followed:
    • SV responsiveness assessed using 250ml fluid challenge
    • If >10% increase in SV but MAP still below desired value, further 250ml boluses until SV increase <10% or target MAP achieved
    • If target MAP still not achieved and SV ‘unresponsive’, phenylephrine 0.1-0.2mcg bolus given (maximum 0.8mcg/hr)
    • If still insufficient, noradrenaline infusion started at 0.01-0.02 mcg/kg/min and titrated to desired MAP by increments of 0.05-0.1mcg/kg
    • If SV fell by >10% of the value following the last fluid challenge, a further 250ml was given
    • Noradrenaline titrated down or stopped if fluid challenges sufficient in maintaining MAP
  • Exit criteria: pH below 7.2, bicarbonate below 14mmol/l, base excess below -10mmol/l or response to catecholamines insufficient – fluid changed to balanced crystalloid and study was terminated.

Outcomes

Primary:

  1. Need for vasopressors

Secondary:

  1. Total dose of catecholamines
  2. Total perioperative fluid
  3. Unplanned intensive care admissions

Results

  • Terminated early for safety reasons (hyperchloraemic metabolic acidosis) after discussion with study safety board and local authority
  • Only 60 of the total planned 240 were studied (30 in each group)
  • More patients required vasopressors in the normal saline group than the balanced crystalloid (97% vs67% respectively,p=0.033)
  • Median weight and duration-adjusted dose of norepinephrine were 0.11(0.00-0.45)mcg/kg/min in the normal saline group compared with 0.00mcg/kg/min in the balanced crystalloid group (p=0.003)
  • No difference between groups in total perioperative fluid and unplanned intensive care admissions
  • Cox regression showed need for vasopressors related to high volume of administered fluid, normal saline resuscitation and lower MAP

Conclusions

  • Study suggests that patients undergoing major abdominal surgery with normal saline fluid therapy have a significantly larger vasopressor requirement than those receiving a more physiological crystalloid.
  • Hyperchloraemia with or without acidosis may be a direct trigger for unfavourable cardiovascular effects – leads to increased nitric oxide, as seen in rats

Strengths

  • Focused question asked
  • Hypothesis based on previous study
  • Prospective double-blinded RCT
  • Patient groups comparable
  • Appropriate inclusion and exclusion criteria
  • Extremely standardised protocol
  • Appropriate statistical analysis i.e. Mann-Whitney U Test for quantitative, non-parametric analysis of 2 unpaired groups

Weaknesses

  • Terminated due to patient safety
  • Underpowered (67%) for primary outcome due to low numbers – power 90% for secondary outcomes
  • Single-centre
  • Protocol resulted in large amounts of intraoperative fluid infusion (median 3427ml of normal saline and 3144 of the balanced crystalloid)
  • No mention of blood products
  • No epidural or intrathecal block
  • Is it an important clinical question?

Implications/Potential for impact

  • Is our practice likely to change following this study?
  • Inference that normal saline may cause detrimental cardiovascular effects due to hyperchloraemic acidosis (leading to increased nitric oxide, as seen in rats) is interesting
  • Vast majority of anaesthetists likely to use a balanced crystalloid e.g Hartmann’s solution, rather than normal saline for elective adult surgery (save for a few circumstances e.g. liver failure etc) as it is more ‘physiological’ – why cause further stress during the stress response?

Following this underpowered study that put patients in harm’s way, I will do as the authors suggest i.e. exactly what I’ve been doing this entire time.

February 2018

Written by Dr. C. Williams

Comparison of 4 cardiac risk calculators in predicting postoperative cardiac complications after non cardiac operations. Cohn S, Ros NF. The American Journal of Cardiology 2017 doi:10.1016/j.amjcard.2017.09.031

Identifying patients who are at high-risk of perioperative complications is something that we are still trying to refine. There are many risk calculators available to try to identify all kinds of risk – ranging from cardiovascular risk, risk of acute kidney injury, risk of post-operative cognitive dysfunction, risk of mortality and so on. Trying to work out which is the best risk calculator to use can seem like trying to negotiate your way through a minefield.

We know that cardiovascular complications after non cardiac surgery are an important cause of postoperative morbidity and mortality. One can use different risk calculators and get different estimates of the patients risk but which is the most reliable risk predictor? This is a question this paper tries to answer by looking at 4 different cardiac risk calculators.

Trying to identify high risk patients is not a new phenomenon – the first cardiac risk index was published by Goldman et al. in 1977. This was followed in 1999 by Lee at al publishing the revised cardiac risk index (RCRI). In 2013 Davies et al. improved prediction using a 5 factor reconstructed RCRI (R-RCRI). The 2014 ACC/AHA guidelines on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery recommended using the RCRI or two newer tools created from the National Surgical Quality Improvement Program (NSQIP) database – namely the myocardial infarction or cardiac arrest (MICA) calculator or the American College of Surgeons surgical risk calculator (ACS-SRC).

Essentially this paper found that all 4 risk calculators performed well at defining low and elevated risk groups but tended to slightly underestimate cardiac events. There are two salient points made:

  1. The definitions for outcomes and timeframes used to develop the risk calculators are different therefore a valid direct comparison of outcomes is not possible
  2. If the risk calculators are used in a manner different from the way derived they do not perform as well

Ultimately risk calculators give an estimate of risk – it is not a black/white answer as to whether that patient will develop that particular complication. What they are useful for is to facilitate shared decision making discussions with patients and enable them to make an informed decision regarding their treatment choice.

Postoperative ERAS interventions have the greatest impact on optimal recovery: Experience with implementation of EAS across multiple hospitals. Aarts M, Rotstein O, Pearsall E metal on behalf of the iERAS group. Annals of Surgery 2018 doi:10.1097/SLA.0000000000002632 

ERAS (Enhanced recovery after surgery) pathways use evidence-based practices to minimise perioperative stress and promote early recovery. These multimodal care pathways incorporate multiple interventions within the preoperative, intraoperative and postoperative course of the patient’s perioperative journey. Multiple papers have been published which demonstrate that ERAS benefits patients when compared to standard care and show a decreased rate of complications, accelerated recovery and earlier discharge from hospital.

But while ERAS has been shown to be effective at improving outcomes, it can be difficult to implement not least because it requires a sustained collaborative effort from members of a multidisciplinary team. This paper aims to determine which component of ERAS has the largest impact on recovery for patients undergoing colorectal surgery and also to look at the relative benefits of ERAS in laparoscopic versus open surgery.

Of the 2876 patients studied only 20.1% had care that was compliant with all phases of the pathway. The poorest compliance was for the postoperative interventions yet these were the interventions most strongly associated with an optimal recovery. Compliance with ERAS was associated with improved outcomes regardless of whether surgery was open or laparoscopic. However, the impact of ERAS compliance was significantly greater in patients having open surgery.

In addition to the ERAS components two other potentially modifiable factors were found to significantly impact on patient outcomes namely operative technique and preoperative haemoglobin levels.

Maybe it is time to go back and reassess how ERAS is implemented. My view as an anaesthetist is that it seems that more emphasis is placed on the preoperative and intraoperative parts of the pathway – the question is whether this is because that is what happens or because those are the parts of the pathway that anaesthetists are more involved with? There is plenty of emerging evidence that postoperative care is as important as other parts of the pathway and if the results of this study are valid then it would seem that postoperative interventions make the most difference to patient outcomes. Once again this paper adds to the increasing body of evidence that as anaesthetists it may have come to the time that we need to step up to the mark and pay more attention to postoperative care. After all, why take so much care making sure our patients are as pre-optimised as possible and given the best intraoperative care if we do not follow this through to the postoperative phase?

Preoperative geriatric assessment and tailored interventions in frail older patients with colorectal cancer: a randomised controlled trial. Ommundsen N, Wyller TB, Nesbakken A et al. Colorectal Disease 2018 doi:10.111/codi.13785

The role of comprehensive geriatric assessment for older patients undergoing surgery is much discussed in the literature at the moment. Geriatric assessment and input has already been shown to make a difference and improve functional status in hip fracture patients. This paper aimed to looks at whether a preoperative geriatric assessment can identify older patients at risk of developing postoperative complications after surgery for colorectal cancer. Patients over the age of 65 years scheduled for elective colorectal cancer surgery and fulfilling criteria for frailty were randomised to either a preoperative geriatric assessment and a tailored intervention (based on the assessment) or usual care.

The findings of this paper were that a geriatric assessment and tailored intervention made no difference to the rate of complications or to the secondary endpoints of median length of stay, discharge to own home, need for readmittance or reoperation within 30 days or 30 day and 3 month mortality.

In my opinion there are significant limitations to the data in this study – despite running for a long period of time (2011 – 2014) only 122 patients were recruited and consequently the study is probably underpowered (acknowledged by the authors). Also, the optimal time from intervention to surgery was hypothesised to be 3 weeks – which seems a short time period for an intervention to make a significant difference to outcome. Furthermore the authors go on to detail that the actual time for pre optimisation was a median of 6 days. Additional evidence is needed to be able to draw conclusions as to the effectiveness of geriatric assessment on patient outcomes particularly given that geriatric input has been shown to be efficient in other surgical settings.

Does goal-directed haemodynamic and fluid therapy improve peri-operative outcomes? A systematic review and meta-analysis. Chong MA, Wang Y, Berbenetz NM, McConchie I. European Journal of Anaesthesiology 2018;35:1-15 doi:10.1097/EJA.0000000000000778 

There is much debate about the effectiveness of perioperative goal-directed haemodynamic and fluid therapy. The seminal study by Shoemaker et al published in 1988 demonstrated that patients receiving preoperative haemodynamic optimisation titrated to goals of end organ blood flow had improved outcomes. Since then there have been multiple randomised controlled trials looking at this. In my personal experience many anaesthetists have quite polarised views on the efficacy of goal directed therapy.

The authors carried out a systematic review and meta analysis of 95 randomised controlled trials where goal directed therapy was studied defined as fluid and/or vasopressor therapy titrated to haemodynamic goals. The findings of this comprehensive review demonstrate that goal directed therapy modestly improves mortality in non-trauma and non pregnant adult surgical patients. The authors suggest that based on the articles included for analysis, the numbers suggest tat for every 1000 patients treated with goal directed therapy, 18 deaths would be prevented.

However, the quality of evidence was low to very low with much clinical heterogeneity among the goal-directed therapy devices and protocols. This is likely to be an area of continuing interest for perioperative research and further well designed and adequately powered trials are needed. Hopefully the OPTIMISE-II and FLO-ELA trials may answer some of the questions surrounding goal directed therapy.

Clinical guideline and recommendations on pre-operative exercise training in patients awaiting major non-cardiac surgery. New GA, Ayyash R, Danjoux GR. Anaesthesia 2018 doi:10.1111/anae.14177

Pre-operative exercise has been much debated over the past few years. There have been several systematic reviews on the effects of pre-operative exercise with sufficient clinical trial data to support pre-operative exercise training as being safe and efficacious. But how exactly can one translate the evidence from clinical trials into clinical practice. This paper aims to provide practical and evidence-based guidelines on how to deliver pre-operative exercise training to patients awaiting major, non cardiac surgery.

Chronic physical inactivity accelerates age-associated declines in maximal aerobic capacity and functional fitness which consequently places individuals at increased risk of complications when undergoing major or complex surgery.

There are ten key recommendations which cover patient selection for exercise training in surgical patients, integration of exercise training into multi-nodal prehabilitation programmes and advice on exercise prescription factors and follow-up. This guideline also touches on the fact that successful implementation of rehabilitations programmes may prove challenging. A range of institutionalised cultural and attitudinal barriers exist that could affect pre-operative initiatives to a varying degree. System-related barriers include lack of educational opportunities highlighting the benefits of exercise, insufficient infrastructure and concerns about the feasibility of delivery and cost effectiveness of potential programmes. Several barriers to implementation are highlighted – the main ones being resistance to change from patients and staff and lack of funding or support from management.

Although the authors acknowledge that further research is needed to identify the optimal exercise prescription, this is a much needed clinical guidelines. Hopefully it will result in perioperative teams being able to incorporate pre-operative exercise training for patients into their routine practice.

Association between handover of anesthesia care and adverse postoperative outcomes among patients undergoing major surgery. Jones PM, Cherry RA, Allen BN et al. The Journal of the American Medical Association 2018;319(2):143-153 doi:10.1001/jama.2017.20040

This article looked at over 313000 patients to look at whether handing over of care from one anaesthetist to another during surgery is associated with a worse outcome. Given the shift work that many anaesthetists (particularly trainees) now work, handing over of care during surgery cannot always be avoided. Handovers may be temporary (initial clinician hands over care to another clinician for a break and then returns) or complete (care is completely handed over to another clinician). Handover is a potentially vulnerable time for the patient because all information required must be transferred between clinicians in a busy environment with many distractions. If crucial details are missed the patient may be at risk of an adverse event. The alternative theory is that a rested clinician taking over care from a fatigued clinician may improve the quality of care and reduce adverse events.

Complete intraoperative handover of care compared with no handover of care was associated with a higher risk of all-cause death, hospital readmission and major postoperative complications over 30 days (44% versus 29%). Intraoperative handovers were also associated with an increase in intensive care admissions and a longer hospital stay.

This is a topic which raises many questions. The authors note that in Canada the number of complete handovers of care is increasing each year. Fatigue and the effects that it has on performance at work is also much debated at the moment.* Knowing that fatigue exacerbates many human limitations, some departments have implemented policies of restricted duty hours for medical staff. It is likely that these policies have an impact on the number of handovers of care.

Given the increase in adverse events observed in this study, the public health implications are concerning. The most prudent approach would be to minimise unnecessary anaesthetic handovers. However the factor of fatigue cannot be ignored. At some point fatigue will have a measurable and detrimental effect on clinicians and handovers in this case would be reasonable. But the question of how to determine when the risk of a fatigued clinician exceeds the potential risk of a complete handover is not one that can currently be answered.

(*July 2017A national survey of the effects of fatigue on trainees in anaesthesia in the UK.  McClelland L, Holland J, Lomas J-P, Redfern N, Plunkett E. Anaesthesia 2017 doi:10.1111/anae.13965)

January 2018

Written by Dr C. Williams

Sexual harassment in medicine – #MeToo. Jagsi R. New England Journal of Medicine 2017 doi:10.1056/NEJMp1715962

This is a short but highly interesting article looking at the phenomenon of sexual harassment in medicine. Currently it seems that not a week passes without the media filled with news of celebrities engaged in sexual misconduct. This article is written by a medical academic who has led a study of workplace sexual harassment in medicine. She describes the numerous incidents reported to her of sexual harassment in medicine and how victims often do not report incidents and the ones that do experience marginalisation, retaliation, stigmatisation and worse. Despite the #MeToo movement, reporting such behaviour is still not straightforward.

But what is sexual harassment. Working in an operating theatre still seems to be a male dominated environment and often an environment where lewd ‘locker-room’ humour dominates. But at what point does this humour cross the line into sexual harassment? One only has to have a few conversations with other healthcare professionals to start to hear stories, often told in jest, of incidences that clearly cross this line. I too have multiple stories which when looking at them objectively are clearly examples of unacceptable behaviour. I was relating one such experience to a colleague as a humorous story (which it was – although not so much at the time). I was asked to formally report the event……..but I didn’t, for several reasons, not least the concern that it would effectively be career suicide. This is also touched upon in the article.

This article concentrates on females being subjected to sexual harassment. But females aren’t the only ones affected. I have witnessed a male colleague being harassed by a bay of 80-plus year old female patients. If the situation had been reversed then I suspect there may have been a different attitude to the event by the female nursing witnesses.

The article mentions an interesting concept devised by academic astronomers. They recognised that mandatory reporting dissuades people so developed a rescue system, or a list of ‘astronomy allies’. These are senior female astronomers who wear prominent buttons at national society meetings and make themselves available to remove colleagues from problematic situations (www.astronomyallies.com). The aim is to provide ‘judgement-free’ help if someone believes it is needed. As the author points out, it raises questions about our society and how sexual harassment is viewed that such a system is required in a professional setting. Maybe such a system is needed in medicine. Much work is clearly still needed on this but the fact we are now openly talking about is a start.

Risk of epilepsy in surgical patients undergoing general or regional anaesthesia. Chang HC, Liao CC, Chang CC et al. Anaesthesia 2017 doi:10.1111/anae.14099

This study looks at the rates of new-onset epilepsy occurring in patients after surgery where they have had either a general or a neuraxial anaesthetic. It is well known that patients who have epilepsy, especially poorly-controlled epilepsy, are at risk, as are patients undergoing brain surgery, open-heart surgery or liver transplantation. But new-onset epilepsy is not something generally that many anaesthetists would consider although both stress and anaesthetic medication have been associated with epilepsy. Previous studies looking at this issue have had many limitations. This nationwide retrospective cohort study of patients in Taiwan sought to evaluate the one-year risk of epilepsy after surgery in patients receiving general or neuraxial anaesthesia.

The Taiwan National Health Insurance Research Database was used to identify patients. Over 200,000 patients were included in each group (general or neuraxial anaesthesia). During the one-year follow-up period the incidence of postoperative epilepsy after general anaesthesia was 0.41 per 1000 and after neuraxial anaesthesia 0.32 per 1000 persons. Compared with patients who had neuraxial anaesthesia, the risk of postoperative epilepsy significantly increased in patients with general anaesthesia when co-existing medical conditions and postoperative complications were included.

This study raises questions about the epileptogenic effects of various anaesthetic agents. But it has limitations. Information about blood biochemistry, lifestyle factors, genetic susceptibility, drug use and the anaesthetic agents used is not available on the database and these could have significant impact on the risk of developing seizures post-operatively. Further clinical studies are needed to be able to draw and firm conclusions.

Doppler-guided goal-directed fluid therapy does not affect intestinal cell damage but increases global gastrointestinal perfusion in colorectal surgery: a randomised controlled trial. Resigner KW, Willigers HM, Jansen J et al. Colorectal disease 2017;19(12):1081-1091 doi:10.1111/codi.13923

Fluid management for colorectal surgery has been much debated recently – should we aim for a restrictive fluid regimen or more liberal fluid treatment? It has been suggested that both restrictive and liberal fluid regimens induce hypo perfusion, the former due to local tissue oedema and the latter due to hypovolaemia. It is also now thought that fluid management in the first hours following surgery may be as important as intra-operative fluid management in improving tissue perfusion and oxygenation. Goal directed fluid therapy (GDFT) has been proposed as a way to reduce complicaations, mortality and length of hospital stay after major colorectal surgery. This study hypothesised that oesophageal doppler guided GDFT as opposed to standard fluid therapy decreased intestinal injury and improved gastrointestinal perfusion during surgery and in the first few hours after surgery.

Patients having elective colorectal cancer surgery with a primary anastomosis were enrolled either to have doppler guided GDFT or standard fluid therapy. All patients had an oesophageal doppler probe inserted and this was kept in situ for a maximum of six hours postoperatively or until the patient could no longer tolerate the probe.

Intestinal damage was determined by measuring intestinal fatty acid binding protein (I-FABP) plasma levels with increasing levels said to correlate with gut-hypoperfusion. Gastric tonometry measuring the intramuscosal carbon dioxide pressure was used to detect gastrointestinal hypoperfusion with the gastric tonometry catheter also left in place for six hours postoperatively.

Interestingly the amount of fluid given did not differ between the intervention and the control groups. The results also showed no difference between the I-FABP levels although the gastric tonometry results indicated better global gastrointestinal fluid perfusion in the intervention group. The clinical outcomes were not statistically analysed but there seems to be relatively little difference between the two groups, although the patients in the intervention group stayed a median of 11 days in hospital as compared to the control groups median of 8 day stay!

Unfortunately this study fails to shed any more light on the best way to manage fluid therapy during major colorectal surgery. Although the authors state that the gastric tonometry results indicated better global gastrointestinal perfusion it is not actually known whether gastric tonometry correlates with colonic perfusion. It is unlikely that these findings will affect current clinical practice anytime soon.

Sugammadex and oral contraceptives: is it time for a revision of the anaesthesia informed consent? Cora DM, Robards CB. Anesthesia & Analgesia 2017 doi:10.1213/ANE.0000000000002677 

This is an interesting letter to the editors raising concerns abut potential issues for women on oral contraceptives who receive sugammadex in the perioperative period. Sugammadex administration can cause certain drugs, including oral contraceptives, to becomes less effective due to lowering of the free plasma concentration. The letter goes on to point out that the drug information that comes with sugammadex states that ‘in vitro binding studies indicate that Bridion may bind to progestogen………the administration of Bridion is considered equivalent to missing dose(s) of oral contraceptives containing oestrogen or progestogen’. The makers of sugammadex recommend that is the patient is taking oral contraceptives and receives a dose of sugammadex then they should be advised to use an additional non-hormonal contraceptive method for the next 7 days.

Sugammadex is not the only drug administered in the perioperative period that could affect oral contraceptives. Many of the routinely used antibiotics can have a similar effect. Currently, there is little emphasis on discussion and counselling patients about these potential drug interactions. The authors suggest that a revision of the anaesthetic consent should contain a general statement to make patients aware that certain medications given during the anaesthetic may interfere with the effectiveness of oral contraceptives. Maybe this is needed but a good starting place would be raising awareness of the issue amongst anaesthetists – in my questioning of a cross-section of anaesthetic colleagues about this issue, no one was aware that sugammadex may interfere with oral contraceptives.

Surgery and discontinuation of angiotensin converting enzyme inhibitors: current perspectives. Bardic N, Povsic-Cevra Z. Current Opinion in Anesthesiology 2017 doi:10.1097/ACO.0000000000000553 

Angiotensin-converting enzyme inhibitor (ACEIs) have been used since the 1970s to treat hypertension with angiotensin II receptors blockers (ARBs) introduced in the 1990s. These medications, collectively known as renin-angiotensin system or RAS antagonists) are thought to work be four different mechanisms:

  1. Cardiovascular protection via reduction of ischaemia
  2. Improvement in cardiac function and short-term survival after myocardial infarction
  3. Antihypertensive effects
  4. Delay in nephropathic progression in diabetic patients

Their use in the perioperative period continues to be a subject of debate. Although the general consensus amongst many anaesthetists is that these drugs should be omitted during the perioperative period in the context intraoperative vasoplegia, previous studies and review articles fail to make any clear recommendations. Multiple studies suggest that patients who take ACEIs or ARBs to treat hypertension are at increased risk of developing severe prolonged hypotension intraoperatively, commonly immediately after induction of anaesthesia.

A large multicentre study published in 2017 (as part of the VISION study) compared patients given ACEIs or ARBs on the day of surgery versus withholding them for 24 hours preoperatively. Their findings suggest that withholding RAS antagonists before major non-cardiac surgery was associated with less risk for complications or death. However, the data from this study had various limitations and it is important to note that withdrawal of ACEIs after surgery is associated with a significant risk of fatal and nonfatal complications postoperatively.

Overall, this article gives a good summary of the recent evidence surrounding RAS antagonists during the perioperative period but still does not provide an answer to the question of whether these drugs should be withheld before surgery or not. It does makes some sensible suggestions as to how to manage these patients:

  • The decision to discontinue RAS antagonists should take into account the original indications for their use, the patient’s clinical status, variability in the patient’s blood pressure and the type of surgery
  • Special attention is needed in surgery with presumed larger blood loss or haemodynamic instability
  • If ACEIs or ARBs are discontinued, they should be restarted as soon as the patient’s condition allows.

Postoperative nausea and vomiting after unrestricted clear fluids before day surgery: a retrospective analysis. McCracken GC, Montgomery J. European Journal of Anaesthesiology 2017 doi:10.1097/EJA.0000000000000760 

Nil by mouth timing remains a contentious issue and a topic that continues to be discussed to great extent in the literature. Current European guidelines encourage the intake of oral fluids until up to two hours before induction of general anaesthesia. The reality is that many patients continue to be starved from the early hours of the morning before surgery and that it is difficult to give patients a true two hour cut-off time for clear fluids.

This study was carried out at Torbay Hospital Day Surgery Unit with a change in the day surgery policy permitting unrestricted clear oral fluids up until the time of transfer to theatre. The aim was to assess the incidence of postoperative nausea and vomiting (PONV) before and after the change to unrestricted pre-operative clear oral fluids.

A total of 11500 patients who received either sedation, general anaesthesia, regional anaesthesia or a combination were included. The results showed a reduction in PONV from 5.2% in patients who could not drink within 2 hours or surgery to 3.8% in patients who had unrestricted clear oral fluids. This suggests that the liberal consumption of clear fluids before the induction of day case anaesthesia reduces PONV.

During the time of the study there were no recorded adverse events of pulmonary aspiration of gastric content requiring patient admission. Since the conclusion of the study a further 10487 patients have undergone surgery on the ‘new’ day surgery pathway which continues to include liberal preoperative clear fluid consumption. During this time there was one episode of aspiration by a patient breathing via a supraglottic airway – the review of the case would suggest that possibly a supraglottic airway was not the most suitable choice for this patient!

This study does seem to present a strong argument that allowing clear oral fluids up until the time of transfer to theatre in day surgery patients is safe, reduces PONV, is not associated with increased episodes of aspiration and gives an improvement in patient satisfaction.

November 2017

Written by Dr C. Williams

Comparison of postoperative outcomes among patients treated by male and female surgeons: a population based matched cohort study. British Medical Journal 2017;359:j4366 doi:10.1136/bmj.j4366

This is a very interesting article published during a time when the argument about males vs females rages on. One only has to do a quick google search to see some of these arguments relating to the medical profession – from female medics have better outcomes to how the high number of female doctors are destroying the NHS.

This population based, retrospective, matched cohort study looked at patients who had surgery between 2007 and 2015. It looked at death rates, readmissions and complications based solely on the sex of the surgeon. The results suggest that patients treated by female surgeons were less likely to die within 30 days but there was no significant difference in readmission or complication rates. This difference in mortality was small and whether it makes any difference to long term survival is unclear. Interestingly no differences were found for patients who were operated on in emergency situations.

This study was done in Canada where, unlike the NHS, patients can freely choose their operating surgeon. The differences seen for elective surgery would suggest confounding factors play a role. The lack of difference in patients having emergency surgery would back this up. So, although an interesting study it would not suggest that one should pick a surgeon based on their sex alone.

Effect of various duration of smoking cessation on postoperative outcomes: A retrospective cohort analysis. Turn A, Koyuncu O, Egan C et al. European Journal of Anaesthesiology 2017 doi: 10.1097/EJA.0000000000000701 

There is now a solid evidence base that smoking is an independent risk factor for perioperative complications. Smokers are 1.4 times more likely to die after surgery than patients who have never smoked. Active smokers also have higher risks of respiratory, cardiovascular and neurological adverse events and are more likely to have problems with infections.

Preoperative smoking cessation would be expected to reduce postoperative smoking and it would be reasonable to expect that longer period of abstinence would correlate with stronger benefits. But the optimal period of preoperative smoking cessation remains controversial. Several randomised trials conclude that 3 to 8 weeks of preoperative cessation reduce wound complications but briefer periods do not seem to reduce respiratory complications. However, a meta-analysis published in 2011 suggested that each additional week of smoking cessation has a significant impact in the reduction in post-operative complications.

Prospective evaluation of the effects of smoking cessation on postoperative outcomes is not easy – a substantial number of patients do not want to stop smoking and even among those that attempt to stop the success rate is thought to be about 50% which makes it difficult to recruit patients in the context of a defined protocol. This paper was a retrospective cohort analysis of adult patients undergoing non-cardiac surgery with the main outcome easier being the relationship between smoking cessation and in-hospital morbidity/mortality.

The summary of the results is that smoking cessation is associated with reduced in-hospital morbidity and mortality – importantly this was shown to be independent of the cessation interval. From a clinical perspective, patients should be encouraged to stop smoking regardless of the time period before surgery.

Incidence of venous thromboembolic events in enhanced recovery after surgery for colon cancer: a retrospective, population-based cohort study. Moms MI, Vendler TA, Haidari JE et al for the Copenhagen cOmplete Mesocolic Excision Study group (COMES). Colorectal disease 2017 doi:10.1111/codi.13910

Abdominal surgery in patients with cancer is associated with an increased risk of venous thromboembolism (VTE). Both the Danish and NICE guidelines recommend prolonged thromboprophylaxis with low-molecular weight heparin for 28 days after executive surgery for colon cancer. The evidence behind these guidelines relies on randomised controlled trials that included both benign and malignant colorectal disorders or colorectal abdominal cancers pooled with other gastrointestinal tract, urinary tract and gynaecological malignancies including palliative surgery. None of these trials included enhanced recovery after surgery (ERAS) programmes.  This study aimed to investigate the risk of symptomatic VTE in patients undergoing elective resection of colon cancer following an ERAS without prolonged VTE prophylaxis.

This was a retrospective analysis of patient who underwent surgery between 2008 and 2013. The median length of stay was 4 days. Of the 1893 patients included, 4 (0.2%) had a non-fatal symptomatic VTE. All 4 of these patients had other postoperative complications prior to the VTE. The rate of VTE found in this study is much lower that the overall 14% risk quoted after major abdominal or pelvic surgery.

It would appear that the risk of symptomatic VTEs is negligible in patients having colon cancer resection following an ERAS programme with an uncomplicated post-operative recovery. It may be that the early mobilisation in an ERAS programme may contribute to the lower risk. The findings of this study suggest that there is a possibility that prolonged VTE prophylaxis may not be cost-effective in these patients.

However, before any changes are made or guidelines rewritten – this is a retrospective study. It does raise questions but further randomised trials are needed to investigate this further.

Randomised feasibility trial of high-intensity training before elective abdominal aortic aneurysm repair. New GA, Batterham K, Colling J et al. British Journal of Surgery 2017 doi:10.1002/bjs.10669

Abdominal aortic aneurysms (AAAs) are usually asymptomatic until they rupture which then carries an overall mortality rate in excess of 80%. Elective surgery, either open or endovascular, is the most effective treatment for preventing AAA-related rupture and death. Open aneurysm repair in particular is associated with neuroendocrine, metabolic and inflammatory changes that lead to an increase in global tissue oxygen uptake of up to 50%. Patients who have a low cardiorespiratory fitness levels are less able to meet these extra demands which can lead to tissue hypoxia and life-threatening complications. A study published in 2010 found that up to half of the patients presenting for intra-abdominal surgery did not have the fitness levels to be deemed at low risk of perioperative complications as quantified by cardiopulmonary exercise testing.

It seems intuitive that improving cardiorespiratory fitness would lead to reduced complications rates after surgery. The clinical effectiveness and cost effectiveness of preoperative exercise testing has not yet been established. It is unclear whether meaningful improvements in cardiorespiratory fitness can be achieved for patients with a large AAA in the limited window available before surgery (usually 4-6 weeks). This study aimed to look at the feasibility and acceptability of high-intensity training (HIT) for preoperative optimisation of patients with a large AAA. Patients were either randomised to usual care or preoperative HIT consisting of three exercise sessions a week for four weeks.

The preoperative HIT seemed to be feasible and acceptable to patients although twenty of the twenty-seven exercise participants had to have their exercise aims adjusted due to triggering safety criteria (such as a systolic blood pressure over 180mmHg). This may have contributed to the fact that measured cardiorespiratory fitness did not change substantially at group level. However, the results seem to point to a beneficial effect of the exercise programme on health status and physical function for up to 12 weeks after hospital discharge.

This feasibility study points to the fact that preoperative exercise and improving cardiorespiratory fitness could be beneficial. Large, multicentre trials that explore clinical and cost effectiveness are needed before recommendations can be safely made about preoperative exercise programmes.

Echocardiography and passive leg raising in the postoperative period: A prospective observational study. El Hadouti Y, Valencia L, Becerra A et al. European Journal of Anaesthesiology 2017;34(11):748-754 doi:10.1097/EJA.0000000000000679 

Perioperative fluid management is a controversial and challenging issue. Both over hydration and conservative fluid therapy can lead to postoperative complications. The difficulty is that many patients have signs that could suggest hypovolaemia (such as oliguria, tachycardia and hypotension) but not all these patients will respond to fluid administration.

Passive leg raising has been demonstrated to simulate preload increase and distinguish fluid responders from non-responders. Studies validating passive leg raising have been carried out most frequently on non-surgical patients. In this study patients in whom low cardiac output was suspected in the immediate postoperative period were included. A baseline echocardiogram was done then repeated 90 seconds after the patients legs had been elevated by 45 degrees. The measurements were repeated after legs had been lowered and finally repeated again after 500mls of fluid administered as a bolus. An increase in cardiac output of greater than 11% after passive leg raising predicted a volume response following fluid with 68% sensitivity and 100% specificity.

This study had a very low sample size and a note is made of difficulty in carrying out the echocardiogram as left lateral decubitus position is best for the echocardiogram but passive leg raising in this position is not really possible. Despite the positive results the potential benefits or clinical uses of using echocardiography and passive leg raising to determine fluid responsiveness remain to be seen.

Acute kidney injury in trauma patients. Harris A, Libert N, Duranteau J. Current Opinion in Critical Care. 2017 doi:10.1097/MCC.0000000000000463 

Multiple organ failure is a later complication of severe trauma that substantially increases morbidity and mortality. Acute kidney injury (AKI) after trauma is associated with an independent association with prolonged hospital stay and mortality. Severe trauma is a time when several renal aggressions occur at the same time making it challenging to establish a strategy to prevent AKI. Factors such as haemorrhage, rhabdomyolysis, traumatic inflammation and renal hits due to emergency surgery or infections may cause acute renal disorders.

The incidence of severe AKI ranges from 9 to 23% and a total of 2 to 8% of trauma patient will require renal replacement therapy. The main risk factors for the development of AKI in trauma patients include haemorrhage, rhabdomyolysis, trauma inflammation, excessive fluid resuscitation and abdominal compartment syndrome.

Trauma care aims at stopping haemorrhage as soon as possible. The earlier this is achieved the better for tissue perfusion. Post traumatic vasoplegic shock can occur and in this situation attention should be paid to arterial pressure to try to optimise renal perfusion. Fluid resuscitation with balanced solute solutions seem to be the most beneficial for trauma patients with regards to AKI although there are no randomised controlled trials looking at this. What this paper makes clear is that AKI is a very real risk for trauma patients and once the initial trauma resuscitation has been carried out special attention should be paid to maintaining renal perfusion. Given the diverse nature of why patients develop AKI after trauma it is difficult to have one protocol to try to reduce the risk.

Sex differences in mortality after abdominal aortic aneurysm repair in the UK. Sidloff D, Saratzis M, Sweeting J et al.  British Journal of Surgery 2017;104(12):1656-1664 doi:10.1002/bjs.10600

Abdominal aortic aneurysm (AAA) screening has been shown to be effective in men both at reducing AAA-related mortality and in cost-effectiveness. Consequently there is now an established AAA screening programme for men over the age of 65 in England and Wales. The benefit of screening for women has not been established. However, one in seven elective AAA repairs are on women and women account for approximately one-third of all deaths from ruptured AAA. Furthermore women have a fourfold higher rupture rate than men at equivalent aortic diameters which suggests there is a strong case for intimating AAA screening in women. Perioperative risk is critical in determining the effectiveness of a screening programme and risk estimates are lacking for women having AAA repairs.

Data from the UK National Vascular Registry was analysed for a 4 year period from 2010 to 2014 with the primary outcome being in-hospital mortality. 13% of the patients included were women. Mortality rates were higher in women for both elective AAA repair (open or endovascular) and emergency repair. The excess mortality rate was found to be largely independent of age, aneurysm diameter and smoking status. It is not clear why this difference in mortality exists although the Canadian Society for Vascular Surgery Aneurysm Study Group identified that women are more likely to be older, have a positive family history of AAA and have significant aortoiliac occlusive disease.

A well designed trial of matched women and men undergoing elective AAA repair would be needed to explain the differences seen. The higher mortality rate in women may have an impact on the benefit offered by any AAA screening programme.

July 2017

Written by: Dr C. Williams

A national survey of the effects of fatigue on trainees in anaesthesia in the UK.  McClelland L, Holland J, Lomas J-P, Redfern N, Plunkett E. Anaesthesia 2017 doi:10.1111/anae.13965

This article publishes the results of a survey carried out by two Welsh trainees looking at the impact of fatigue reported by anaesthetic trainees. With news headlines of junior doctors dying following crashes while driving after night shifts and recent BBC Inside Out South coverage of a junior doctor’s driving ability after a night shift* this is an important topic to look at. Since the introduction of the European Working Time Directive in 2009 the working patterns of junior doctors have changed with far more shift work and often rotas that change from days to nights and back again very quickly. Also with training arranged in the way it is now, many trainees may move hospital every 6 months to 1 year, sometimes over large geographical areas.  Maybe this issue has always been the case, maybe we are more aware due to increased knowledge, understanding and recognition of the effects of fatigue but what is clear is that it is not something that can be ignored. The results of this survey highlight some worrying figures. High numbers of trainees say that fatigue has affected their physical health, psychological wellbeing, personal relationships and ability to train including exams, audits/QI projects. A high proportion reported being involved in an accident or near miss when travelling home after a night shift. This has implications both to the safety of the trainee and to the public.

This survey has highlighted this important issue. It has been a contributing factor in the establishment of a ‘fatigue group’ in association with the AAGBI, GAT and the RCoA. There have been efforts made by some trusts to highlight the risks of fatigue and provide strategies and advice to help junior doctors. Of course, fatigue is not something that only affects doctors or even just healthcare professionals but anyone who works shifts particularly night shifts. Although this survey only concentrates on one set of junior doctors, it would seem sensible that strategies that work for trainee anaesthetists to cope with fatigue may be generalizable to other groups of people affects by this issue. Hopefully highlighting the problem of fatigue and supporting doctors, managers and trusts on how to tackle this issue will make things safer for doctors, and ultimately our patients and the public.

*http://www.bbc.com/news/av/uk-england-berkshire-38716140/doctors-fall-asleep-driving-after-punishing-night-shifts-the-bbc-learns

Prehabilitation in perioperative care. Moorthy K, Wynter-Blyth V. British Journal of Surgery 2017;104(7):802-803. doi:10.1002/bjs.10516

This is article looking at prehabilitation and the role it plays in patients with upper gastrointestinal cancer. It is a well known fact now that there are greater demands placed on surgical systems with the patient population undergoing major abdominal surgery becoming older and increasingly frail with multiple co-morbidities. This is coupled with organizational issues such as a drive for earlier postoperative discharge and with surgeons facing increased scrutiny of their work and complication rates in response to governmental and public demands for greater transparency. High-risk patients are undoubtedly at greater risk of adverse postoperative events and a longer recovery time. The article talks about enhanced recovery programmes which are well established in many surgical specialties and have led to post operative outcome improvements. However, they mainly focus on the intraoperative and postoperative phases of the patient journey. The concept of prehabilitation is based on the principle that amongst other things, structured exercise in the preoperative period will provide the patient with a ‘physiological buffer’ to withstand the stress of surgery. Although preoperative exercise is associated with improved preoperative functional capacity there is currently limited evidence to show that it improves postoperative outcomes. There are several clinical trials in progress that aim to address this evidence gap. Importantly, prehabilitation must be about more than just exercise. Addressing all the other factors that contribute to outcome such as body weight, nutrition, alcohol, smoking and the critical but often forgotten psychological aspect. The preoperative period is an ideal opportunity to make the most of a ‘teachable moment’ and emphasise the importance of making positive lifestyle changes. This is an exciting area that is being explored. The publication of new clinical trials should provide some answers. Future research is needed possibly looking at cost-effectiveness and how prehabilitation can be linked to enhanced recovery pathways. Ultimately the aim is a better outcome for the patient.

Claims for compensation after injuries relating to airway management: a nationwide study covering 15 years. Fornebo I, Simonsen KA, Bukholm IRK, Kongsgaard UE. Acta Anaesthesiologic Scandinavica 2017 doi:10.1111/aas.12914

One of the anaesthetist’s ‘raison d’être’ is to manage the airway by whichever method they chose for the given situation – facemask, oral or nasal airway, a supraglottic device or an endotracheal tube. However, no method is risk free and all may cause complications ranging dental damage, soft tissue trauma through to catastrophic complications due to failure to secure the airway. A subset of patients have specific characteristics that may mean we can predict a likely difficult airway. Equally there are patients who have none of these characteristics yet are found to have a difficult airway at induction of anaesthesia.

Although not common, disastrous outcomes with failed or difficult tracheal intubation are well known to anaesthetists. An integral part of our training is the learning strategies to manage both the anticipated and unanticipated difficult airway.

This study looked at compensation claims relating to airway management over a 15-year period in Norway. 0.8% of claims relating to anaesthesia involved airway management. 38% of claims related to dental injuries. Severe injuries were defined as failed intubation, misplaced endotracheal tube, aspiration or a ‘miscellaneous’ group. They accounted for 10% of all the claims but made up 37% of claims relating to emergency procedures. Interestingly all claims made from patients needing airway management in a pre-hospital setting and 87% of the claims from ICU were rejected. This may reflect the situation in which airway management is considered a life-saving procedure.

Although the results of this study are specific to Norway it serves to highlight that airway management can result in complications and we should continue to be vigilant particularly in emergency cases.

Intraoperative ketamine for prevention of postoperative delirium or pain after major surgery in older adults: an international, multicenter, double-blind, randomized clinical trial. Avidan MS, Maybrier HR, Abdallah AB, Jacobsohn E et al. The Lancet. 2017;390(10091):267-275 doi:10.1016/S0140-6736(17)31467-8

In patients over the age of 60 delirium is one of the most common complications and is associated with increased morbidity and mortality. It has many causes and the pathophysiology is not completely understood which makes it difficult to predict and treat. In surgical patients risk factors are likely to be pain, treatment with opioids and the inflammatory response to injury. In theory a drug that provides analgesia and prevents delirium would be an important advance in perioperative medicine. A postoperative infusion of dexmedetomidine has shown promise although further studies are recommended. However, this drug is expensive and requires a continuous intravenous infusion therefore is unlikely to be a practical solution.

It has been reported that intraoperative subanaesthetic ketamine administration reduces postoperative pain, reduces postoperative opioid requirement and reduces the postoperative markers of inflammation. Based on this the study authors hypothesise that intraoperative ketamine may reduce the incidence of postoperative delirium. But ketamine is also well known to be a psychoactive drug with hallucinogenic properties so could theoretically contribute to postoperative delirium.

This multicentre study randomly allocated patients to one of three groups – placebo (to receive normal saline), low dose ketamine (0.5mg/kg) or high dose ketamine (1mg/kg) to be given after induction of general anaesthesia but before surgical incision. They found that there was no difference in the incidence of delirium in any of the groups and there were more postoperative hallucinations and nightmares with increasing doses of ketamine.

In conclusion, ketamine does not reduce postoperative delirium and may actually increase harm by increasing the incidence of hallucinations and nightmares. Ketamine use has increased particularly with the introduction of enhanced recovery programmes – maybe the time has come for some further studies regarding its use in elderly patients.

Falls from the O.R. or procedure table. Prielipp RC, Weinkauf JL, Esser TM, Thomas BJ, Warner MA. Anesthesia & Analgesia 2017. doi:10.1213/ANE.0000000000002125 

Patients falling from the operating table is a scenario that thankfully most anaesthetists will not encounter. I know of one event that happened in a neighbouring theatre when I had just started my anaesthetic training. The patient was unharmed and that was the last I heard about it. The American Society of Anesthesiologists highlights that anaesthesia is the practice of medicine with one of its primary foci being ‘management and preservation of patient safety’. A patient falling from the operating table is a clear breakdown of this responsibility and can have medical, professional, legal and financial consequences.

This study looked at claims recorded in the Anaesthesia Closed Claims Project database looking for claims associated with falling from the year 2000 to now. There were 21 claims identified – 15 in patient having general anaesthsia and 4 in those receiving regional anaesthesia. Approximately half of the claims resulted in payouts to the patients ranging from $18,000 to $925,000. Patient falls from the operating table must be considered preventable adverse events. Injuries from falls such as these can be catastrophic including brain damage, paralysis and even death.

This paper talks very much about the anaesthetists duty and role in preventing falls. The reality is that it should preventing falls should be shared responsibility for every member of the team. Many of the falls occurred when patients were partially sedated or awakening from general anaesthesia and potentially confused or agitated. From experience this is the time at which other staff may be distracted and concentrating on other tasks. The entire operating theatre team need to be proactive in maintaining patient safety at all times.

 

Perioperative COX-2 inhibitors may increase the risk of post-operative acute kidney injury. Abrahamsson A, Oras J, Snygg J, Block L. Acta Anaesthesiologica Scandinavica 2017;61(7):714-721 doi:10.1111/aas.12912

This was a study looking at patients who had undergone pancreaticoduodenectomy. In 2012, enhanced recovery after surgery (ERAS) guidelines were published for these patients recommending a restrictive fluid regimen to avoid the fluid overload that has been shown to be hazardous for these patients. Acute kidney injury (AKI) is not uncommon after major abdominal surgery and is known to be a major cause of postoperative morbidity and mortality. Perioperative hypotension and hypovolaemia are known to contribute to AKI.

Anaesthetists in Gothenburg, Sweden made the observation that patients undergoing open pancreatic surgery with an ERAS restrictive fluid protocol were more likely to develop postoperative AKI and spend longer on ICU. Consequently, they reviewed the notes of patients who underwent pancreatic surgery prior to the introduction of the ERAS fluid protocol and compared this to patients who underwent surgery after the introduction of the ERAS fluid protocol. They found that the incidence of AKI was significantly higher in the patients who underwent surgery using the ERAS restrictive fluid protocol (13% vs 2% in the pre-ERAS patient group). They also found that COX-2 inhibitors were given more frequently to patients in the ERAS group.

They concluded that the combination of a goal-directed restrictive fluid therapy with the administration of COX-2 inhibitors significantly increases the risk of AKI.

Postoperative respiratory complications in patients at risk for obstructive sleep apnea: a single-institution cohort study. Ramachandran SK, Pandit J, Devine S, Thompson A, Shanks A. Anesthesia & Analgesia 2017;125(1):272-279 doi:10.1213/ANE.0000000000002132 

Obstructive sleep apnoea (OSA) is not an uncommon condition and is thought to affect up to 25% of middle-aged men and up to 10% of middle-aged women. It has a significant impact on quality of life, life expectancy, cardiovascular disease and respiratory disease. Recent evidence also suggest that it is associated with a 3 to 6 times increase in post-operative respiratory complications. The majority of patients with OSA remain undiagnosed and preoperative screening remains the most efficient method to identify those at risk.

This retrospective observational study looked back over the notes of 108,479 patients and assigned OSA risk retrospectively using the Perioperative Sleep Apnea Predictive (PSAP) score*. They found that a high PSAP score was associated with a higher incidence of postoperative respiratory complications and an increased need for postoperative intubation. Other factors that were associated with postoperative respiratory complications include the anaesthetic agent used, neuromuscular blocking agents and opioid use.

Patients with suspected OSA should be identified, assessed and commenced on appropriate treatment preoperatively where possible. They may also require a modification of the anaesthetic technique used to try to minimize the risk of postoperative respiratory complications (PRCs) and a recognition that they are at higher risk of developing PRCs.

*Ramachandran SK, Kheterpal S, Consens F et al. Derivation and validation of a simple perioperative sleep apnea prediction score. Anesth Analg. 2010;110:1007-1015

Body height and the spread of spinal anaesthesia for caesarean section: a prospective controlled trial. Acta Anaesthesiologica Scandinavica 2017;61(7):824-831 doi:10.1111/aas.12928

Spinal anaesthesia is the preferred anaesthetic technique for caesarean sections. However, as this article rightly points out there is a considerable variability in the dose regimens used. As a trainee one only has to ask several different consultants to realise that each one has a preferred dose for the ‘best’ spinal anaesthetic! The aim is a dose of intrathecal bupivacaine that maintains anaesthesia but minimizes the risk of maternal hypotension. Several patient variables are usually factored into predicting the spread of spinal anaesthesia including age, height, weight and body mass index. The time required to achieve an adequate sensory block for surgery tends to increase linearly with height and decrease with increasing weight.

This study hypothesized that shorter patients need a lower spinal anaesthesia dose than taller patients. 270 pregnant women were assigned to either the tall (T) group or shorter (S) group. Both groups were then randomly assigned to one of nine subgroups of intrathecal ropivacaine dose (between 7-15mg). They found that height did not significantly affect the height of the block achieved with the different doses. However, larger ropivacaine doses were associated with increased hypotension which was more pronounced in shorter patients.

This was a small study and maybe separating patients on height alone is too simplistic to answer the question. Ultimately, the answer as to the best dose of local anaesthetic for spinal anaesthesia remains to be discovered.

Website Powered by WordPress.com.

Up ↑