Association of intraoperative pulse pressure drop and minimum mean arterial pressure with postoperative length of stay: A stratified reanalysis of published data by age and sex.

Abstract

Intraoperative hypotension (IOH) is associated with postoperative organ dysfunction, but no universal definition exists. Guidelines recommend a mean arterial pressure (MAP) threshold of 60-70 mmHg. Prolonged postoperative length of stay (pPOLOS) serves as a proxy for organ injury. This study explores the association between IOH and pPOLOS risk, accounting for patient characteristics (sex and age). Retrospective, single-center cohort study of adult patients undergoing general anesthesia for scheduled non-cardiac surgery between July 2017 and December 2019. pPOLOS was defined as a LOS higher than the median value (main outcome). Relationships between pPOLOS risk and three previously identified IOH variables-drop in pulse pressure (DropPP: difference between maximum and minimum values), minimal MAP (MinMAP), and cumulative time with pulse pressure > 61 mmHg per hour of surgery (CumTimePP > 61 mmHg)-were modeled using piecewise linear splines. Our study examined 9,516 patients. For the whole population, the relationship between DropPP and pPOLOS risk was pseudolinear with no activation threshold (slope 0.29-0.52%/mmHg). For MinMAP, an activation threshold of 73 mmHg was identified, below which the association became linear (slope: -0.64%/mmHg). For CumTimePP > 61 mmHg, pPOLOS risk increased sharply (initial slope: 8.40%/min) and reached a saturation threshold at two minutes. Women demonstrated a lower pPOLOS risk and a lower IOH threshold than men. In contrast, older patients (≥65 years) exhibited a higher baseline pPOLOS risk and showed no identifiable IOH threshold. The identified IOH threshold (MAP < 73 mmHg) is in line with values reported in the existing literature. Pulse pressure variability, age, and sex emerged as key determinants of pPOLOS risk.