Anesthesia in the News
  • Intraoperative Hypotension and Perioperative MI Risk

    A newly published study, published in July in the journal Anesthesia & Analgesia, has identified intraoperative hypotension (IOH) as a possible contributor to clinically significant perioperative myocardial infarction (MI) in patients undergoing noncardiac surgery.

    Cases, criteria, and controls

    The researchers conducted a nested case-control study with patients developing MI <30 days post surgery matched with non-MI patients, sampled from a large surgery cohort.  Study participants were adults undergoing noncardiac surgery at three university hospitals in Sweden from 2007 to 2014.

    Matching criteria were age, sex, American Society of Anesthesiologists (ASA) physical status, cardiovascular disease, hospital, year-, type-, and extent of surgery. Patients’ medical records were reviewed to validate MI diagnoses and retrieve information on comorbid history, baseline blood pressure, laboratory and intraoperative data.  Main exposure was IOH, defined as a decrease in systolic blood pressure (SBP), in mm Hg, from preoperative individual resting baseline lasting at least 5 minutes.

    Outcomes were acute MI, fulfilling the universal criteria, subclassified as type 1 and 2, occurring within 30 days and mortality beyond 30 days among case and control patients.  Conditional logistic regression assessed the association between IOH, decrease in SBP from individual baseline, and perioperative MI.  Mortality rates were estimated using Cox proportional hazards.  Relative risk estimates were reported as were the corresponding absolute risks derived from the well-characterized source population.

    ‘Triple increased odds’

    A total of 326 cases met the inclusion criteria and were successfully matched with 326 controls.  The distribution of MI type was 59 (18%) type 1 and 267 (82%) type 2.  Median time to MI diagnosis was 2 days; 75% were detected within a week of surgery.

    Multivariable analysis acknowledged IOH as an independent risk factor of perioperative MI.  IOH, with reduction of 41-50 mm Hg, from individual baseline SBP, was associated with a more than tripled increased odds, odds ratio (OR) = 3.42 (95% confidence interval [CI], 1.13-10.3), and a hypotensive event >50 mm Hg with considerably increased odds in respect to MI risk, OR = 22.6, (95% CI, 7.69-66.2).  In patients with a very high-risk burden, the absolute risk of an MI diagnosis increased from 3.6 to 68 per 1,000 surgeries.

    Scrutiny please

    The study authors posit that their research indicates that IOH seems to be an important contributor to clinically significant perioperative MI in patients undergoing noncardiac surgery.  As such, they counsel that “The high absolute MI risk associated with IOH among a growing population of patients with a high-risk burden undergoing surgery suggests that increased vigilance of BP control in these patients may be beneficial.”

    For a deep dive into the study details, “Intraoperative Hypotension and Myocardial Infarction Development Among High-Risk Patients Undergoing Noncardiac Surgery: A Nested Case-Control Study,” Anesth Analg. 2021 Jul 1;133(1):6-15., find the link at:

    https://pubmed.ncbi.nlm.nih.gov/33555690/