Postoperative delirium in elderly patients is associated with subsequent cognitive impairment. Sprung J, Roberts R, Weingarten T et al.

British Journal of Anaesthesia 2017;119(2):316-323

Presented by: Dr I. Roberts

Background  

Paper examined the risk for postoperative delirium (POD) in patients with mild cognitive impairment (MCI) or dementia, and the association between POD and subsequent development of MCI or dementia in cognitively normal elderly patients.

Design & Setting

  • Ran by Mayo clinic.
  • Made use of a cohort that already available on a database to ascertain if patients with cognitive dysfunction experienced post operative delirium.
  • Patients 65 yr of age enrolled in the Mayo Clinic Study of Aging who were exposed to any type of anaesthesia from 2004 to 2014 were included.
  • Cognitive status was evaluated before and after surgery by neuropsychological testing and clinical assessment, and was defined as normal or MCI/dementia.
  • Postoperative delirium was detected with the Confusion Assessment Method for the intensive care unit.

 Subjects

  • In 2004, 70–89 yr olds were identified from a Mayo Clinic Database, randomly selected, and invited to participate in the study.
  • In 2008, ongoing recruitment was initiated using the same protocols as baseline
  • In 2012, the lower limit of the age criterion was reduced to 50 years of age.
  • The study includes all participants enrolled and examined in person in the MCSA study from November 2004 to February 2014 who underwent surgeries and procedures under anaesthesia at Mayo Clinic in Rochester, MN, USA
  • Only participants who were 65 yr of age at enrolment were included.

 Intervention

  • Nil specific intervention.
  • The use of the CAM ICU scoring system was used to identify post op delirium.
  • A pre and post op cognitive impairment screen was used to ascertain both baseline and post op cognition levels.

Outcomes

Claimed to have confirmed previous findings that in a general surgical population elderly patients with cognitive dysfunction at the time of surgery are at higher risk for clinically evident post op delirium compared with patients without mild cognitive impairment.

Main finding is that elderly patients who are cognitively normal at a detailed assessment performed before surgery and who experience clinically evident post op delirium are more likely to develop cognitive impairment or dementia subsequently compared with those who do not experience post op delirium.

Results

  • The frequency of POD was higher in patients with pre-existing cognitive impairment compared with no cognitive impairment/dementia.
  • The frequency of MCI/dementia at the first postoperative evaluation was higher in patients who experienced POD compared with those who did not.

Conclusions

Mild cognitive impairment or dementia is a risk for post op delirium. Elderly patients who have not been diagnosed with cognitive impairment but experience post op delirium are more likely to be diagnosed subsequently with cognitive impairment or dementia.

Strengths

  • Ambitious project.
  • Made us of a large source of data that was readily available.
  • Appeared to confirm a notion that is already in existing literature.
  • Made use of validated means for detecting both cognitive dysfunction and post op delirium.

Weaknesses

  • Observational study only.
  • Mixed methodology with observation both retrospective and prospective.
  • Data observational in nature with no firm validated intervention being studied.
  • Lots of the conclusions seem to be inferred.
  • Did not drill into the data to ascertain if there was one particular factor causing post op delirium.
  • Did not offer any insights into how this phenomenon may be tackled in the future.
  • The journal club group felt it was a weak paper with no rigorous methodology that could be used to garner meaningful results.
  • Appears that this group had a large data set and used it to contrived this paper, which doesn’t appear to clinically add anything to this known phenomenon that already exists in the literature.

Implications

The reader will be aware of the notion that the long term effect of anaesthesia can result in cognitive impairment. The reader will also be appreciative of the fact that post op delirium can contribute to cognitive decline in at risk patients over time.

Potential for impact

  • Raises awareness amongst trainees about this phenomenon.
  • Impact level is poor due to weaknesses within the paper.