Intraoperative Hypotension and Its Association with Postoperative Acute Kidney Injury

Abstract

Background: Intraoperative hypotension (IOH) is a common perioperative complication linked to inadequate organ perfusion. The kidney, with its high metabolic demand and unique microvascular architecture, is particularly vulnerable to ischemic injury. The precise thresholds of mean arterial pressure (MAP) and duration of hypotension that precipitate renal injury remain a critical area of investigation.

Objective: This study aimed to investigate the association between varying degrees of IOH and the incidence of postoperative acute kidney injury (AKI) in patients undergoing major non-cardiac surgery at a tertiary care center.

Methods: We conducted a prospective, observational cohort study of 100 adult patients undergoing elective major non-cardiac surgery under general anesthesia. Invasive or oscillometric blood pressure was recorded at 5-minute intervals intraoperatively. The primary exposure was IOH, defined as a mean arterial pressure (MAP) of <65 mmHg for a cumulative duration of ≥5 minutes. Patients were categorized into No IOH, Short IOH (<10 minutes), or Prolonged IOH (≥10 minutes). The primary outcome was the incidence of AKI, defined according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria, based on serum creatinine changes within the first 72 hours postoperatively.

Results: The overall incidence of AKI was 21%. The incidence was significantly higher in the Prolonged IOH group (44.4%) compared to the Short IOH group (16.7%) and the No IOH group (5.3%) (p<0.001). Multivariate logistic regression analysis identified prolonged IOH (MAP <65 mmHg for ≥10 minutes) as an independent predictor of AKI (Adjusted Odds Ratio [aOR] 9.43; 95% CI 2.18 – 40.75; p=0.003). Even a shorter duration of hypotension (≥5 minutes) showed a trend towards increased risk. Other significant risk factors included pre-existing hypertension and higher baseline serum creatinine.

Conclusion: Intraoperative hypotension, particularly when MAP falls below 65 mmHg for a cumulative duration of 10 minutes or more, is strongly and independently associated with an increased risk of postoperative acute kidney injury. This study underscores the importance of meticulous hemodynamic management and avoiding even modest periods of hypotension in the perioperative setting to safeguard renal function.