Post-induction hypotension and early intraoperative hypotension associated with general anaesthesia

Background: We hypothesized that different phases of intraoperative hypotension should be differentiated because of different underlying causative mechanisms. We defined post-induction hypotension (PIH; i.e. arterial hypotension occurring during the first 20 min after anaesthesia induction) and early intraoperative hypotension (eIOH; i.e. arterial hypotension during the first 30 min of surgery).

Methods: In this retrospective study, we included 2037 adult patients who underwent general anaesthesia. Arterial hypotension was defined as a systolic arterial blood pressure (SAP) <90 mm Hg or a need for norepinephrine infusion at > 6 µg min -1 at least once during the phases of PIH and eIOH. Multivariate logistic regression analysis was used to test for association of clinical factors with PIH and eIOH.

Results: Independent variables significantly related to PIH were pre-induction SAP [odds ratio (OR) 0.97 (95% confidence interval 0.97-0.98)], age [OR 1.03 (1.02-1.04)], and emergency surgery [OR 1.75 (1.20-2.56); P <0.01 each]. Pre-induction SAP [OR 0.99 (0.98-0.99), P <0.01], age [OR 1.02 (1.02-1.03), P <0.01], emergency surgery [OR 1.83 (1.28-2.62), P <0.01], supplementary administration of spinal or epidural anaesthetic techniques [OR 3.57 (2.41-5.29), P <0.01], male sex [OR 1.41 (1.12-1.79), P <0.01], and ASA physical status IV [OR 2.18 (1.19-3.99), P =0.01] were significantly related to eIOH.

Conclusions: We identified clinical factors associated with PIH and eIOH. The use of these factors to estimate the risk of PIH and eIOH might allow the avoidance or timely treatment of hypotensive episodes during general anaesthesia.