Arterial pulse pressure and postoperative morbidity in high-risk surgical patients

British Journal of Anaesthesia 2018;120(1):94e100

Presented by: Dr Richard Cashmore

Background

  • Arterial Pulse pressure reflects the complex haemodynamic interplay between stroke volume, heart rate, aortic compliance, and peripheral vascular tone.
  • In contrast to the general medical population (where elevated PP is associated with increased all cause cardiovascular mortality), lower pulse pressure in patients with cardiac failure is associated with accelerated mortality.
  • Authors state that deconditioned surgical patients share similar cardiovascular and autonomic features with cardiac failure patients
  • They propose that low preoperative pulse pressure may therefore also be associated with increased risk of postoperative morbidity in higher-risk surgical patients.

 Design & Setting

  • This was a Secondary Analysis of a Prospective, Multicentre, Cohort study
  • Authors Hypothesized that the pulse pressure threshold identified in cardiac failure patients ≤53 mm Hg– (the authors refer to The MAGGIC [Meta-Analysis Global Group in Chronic Heart Failure] meta-analysis identified pulse pressure ≤53mm Hg as a robust independent predictor of mortality),was associated in a similar manner with postoperative morbidity in higher-risk surgical patients referred for cardiopulmonary exercise testing as part of their routine preoperative assessment.

Subjects

  • Referral for CPX testing by the Surgeon, Anaesthetist or both, or if 1) planned major surgery over 2hrs 2) they were deemed to be at higher risk of postoperative morbidity or mortality by their referring clinician, on the basis of their preoperative co-morbidity, the magnitude of the surgical insult, or both (+POSSUM scored but not mentioned further).
  • Patients were excluded if they did not consent, or had contra-indication to CPX testing.
  • The primary explanatory outcome was any postoperative complication, assessed using the Post-Operative Morbidity Survey (POMS) by postoperative day 5.
  • Power calculation- Postop ≥569 patients would be required to detect a clinically relevant reduction of 20% fewer patients being free of morbidity on postoperative day 5.

 Intervention

  • The types of surgery involved in this study, usual standard of care (multi-centre)
  • Postoperative management was conducted according to local clinical guidelines

Outcomes

  • The presence of morbidity from any of the nine domains of the POMS was considered to constitute the presence of significant morbidity by postoperative day 5.
  • Secondary clinical outcomes were time to become morbidity free and hospital length of stay.

Results

  • Stats- divided cohort into two groups according to threshold (≤53) as above. The relationship was compared using Fisher’s exact test. Continuous data was analysed using analysis of covariance (controlling for age, sex, and BMI), with post hoc Tukey-Kramer tests to identify within-and between-factor differences.
  • To determine whether observed associations were a result of confounding, they repeated the analysis using a one-way, hierarchical forward switching logistic regression model, which included the following covariates that are associated with postoperative morbidity: age, BMI, sex, diabetes mellitus, preoperative cardiovascular disease and medication (ischaemia, cardiac failure, and dysrhythmias), and anaerobic threshold 11.1 ml kg-1 min-1
  • Logistic regression analysis confirmed that pulse pressure 53 mm Hg [OR:1.95 (1.11-3.46); P¼0.02] and type of surgery [OR: 5.88 (1.75-19.8); P¼0.004] were associated with all-cause morbidity on postoperative day 5 (Supplementary Table S4).

 Conclusions

  • Patients with pulse pressure ≤53mmHg were more likely to sustain postoperative morbidity in the first 5 days after surgery [odds ratio: 2.24 (1.29-3.38); P<0.001], as reflected by the time to become morbidity free.
  • In our study, we found that patients with pulse pressure ≤53mm Hg alone, or in combination with a systolic arterial pressure threshold <140mm Hg (219/243), had a similar incidence of postoperative morbidity by postoperative day 5 [OR: 1.94 (0.25-15.2); P¼9].
  • Mirroring the heart failure literature, we found that lower pulse pressure was independently associated with more postoperative morbidity.

Strengths

  • Prospective
  • Adequate powering stated
  • Study personnel and patients were blinded to pulse pressure data linked to outcomes.

Weaknesses

  • Fairly catch-all referral criteria
  • Un-even split of comparison groups 519 vs 302 (post exclusion 400 vs 260)
  • No specifics of incremental CPX programme details.
  • All hospitals used enhanced recovery programmes (? all the same)
  • Peri-operative management was not uniform (+/- neuroaxial etc)
  • 161 excluded from study (large percentage)
  • Comprehensive echocardiography (which was logistically and financially beyond the scope of this study cohort) and B-type natriuretic peptide data are likely to help in clarifying these findings in both heart failure and perioperative populations
  • Short term follow-up
  • No mention of powering for subgroup analysis made.
  • No specific details given on the type of surgery involved.
  • Supplementary data link takes me to a page on low carbon steel.

 Implications

  • Pulse pressure is a simple, inexpensive, and readily available clinical index, provides additional useful preoperative information in surgical patients who are deconditioned, with low cardiopulmonary reserve.

 Potential for impact

  • Claim that findings suggest that lower pulse pressure in higher-risk surgical patients merits the consideration of an extensive preoperative assessment centred on cardiovascular performance.
  • An interesting area, but limitations of study may impact.