Severity, duration, and pattern of intraoperative hypotension and early postoperative cognitive decline in adults undergoing non-cardiac surgery: a prospective observational cohort study

Introduction Intraoperative hypotension (IOH) is known to pose risks for myocardial and renal injury, but its links to early postoperative cognitive decline (ePOCD) are ambiguous due to varying definitions of IOH across studies. Method This prospective observational cohort study at a tertiary teaching hospital in Ajman, United Arab Emirates, involved 261 adults undergoing elective non-cardiac surgeries under general anaesthesia. The study defined IOH as a decrease in mean arterial pressure (MAP) exceeding 20% from the pre-induction baseline and categorised it by severity (mild, moderate, severe) and duration/pattern (controlled episodes, prolonged episodes, frequent short episodes). Cognitive assessment was conducted using the Mini-Mental State Examination and Montreal Cognitive Assessment pre-surgery, immediately after, and on postoperative day 1. Results The results indicated that 93.1% of patients experienced IOH as defined, primarily mild and moderate cases, with no severe instances recorded. ePOCD was identified in 3.1% of patients. Scores on both cognitive assessments dropped significantly right after surgery but showed partial recovery by day 1. Notably, the presence of IOH did not correlate with ePOCD, whereas the severity and pattern of hypotension were associated with it, with higher ePOCD rates in patients with moderate hypotension and in those with a single prolonged episode or frequent short episodes than in those with a single short (controlled) episode. In addition, patients experiencing ePOCD were significantly older and had longer durations of hypotension. The findings suggest that a simple threshold of >20% relative change in MAP fails to predict ePOCD risk, whereas cumulative exposure, severity, and pattern of hypotension were associated with ePOCD in this exploratory analysis. Because all ePOCD events occurred in the oldest patients, these associations could not be separated from the effect of age and should not be interpreted as evidence that these measures predict ePOCD independently. Discussion These results argue against relying on binary definitions of IOH in neurocognitive studies and highlight the importance of exposure metrics. Confounding, particularly by age, prevented causal inference because of the small number of ePOCD events and collinearity between age and hypotensive exposure.