Association between continuous low-dose norepinephrine infusion and intraoperative hypotension burden in patients aged 80 years and older undergoing total hip arthroplasty: a retrospective cohort study

Objective To compare the associations of different intraoperative blood pressure management strategies with hypotension burden and postoperative recovery outcomes in patients aged 80 years or older undergoing total hip arthroplasty under general anesthesia. Methods This single-center retrospective cohort study included patients aged ≥80 years undergoing total hip arthroplasty under general anesthesia. Patients were grouped according to intraoperative blood pressure management strategy: continuous low-dose norepinephrine (NE) infusion versus conventional reactive management. In the NE group, infusion was typically started immediately after induction and titrated within a usual range of 0.01–0.05 μg/kg/min according to continuous arterial pressure monitoring, overall hemodynamic trends, and clinical judgment, primarily for intraoperative blood pressure support. The primary outcome was intraoperative hypotension burden, quantified using the time-weighted average (TWA), area under the curve (AUC), and hypotension duration ratio (HDR) for MAP <65 mmHg. Secondary outcomes included postoperative delirium and postoperative length of hospital stay. Multivariable logistic regression was used to explore factors associated with postoperative delirium. Results A total of 119 patients were analyzed (NE group, n = 56; control group, n = 63). Compared with conventional management, continuous low-dose NE infusion was associated with a lower intraoperative hypotension burden, including lower TWA of MAP <65 mmHg (0.24 [0.00–0.42] vs. 0.46 [0.25–0.83] mmHg; p < 0.001), as well as lower AUC and HDR (all p < 0.001). The NE group also had a lower incidence of POD (10.7% vs. 28.6%, p = 0.015) and a shorter postoperative length of hospital stay (7 [7–8] vs. 8 [7–9] days, p < 0.01). In multivariable analysis, the NE-based strategy remained independently associated with lower odds of POD after adjustment for age and history of stroke (adjusted OR 0.24; 95% CI 0.08–0.68; p = 0.007). Conclusion In patients aged 80 years and older undergoing total hip arthroplasty, a continuous low-dose norepinephrine infusion strategy was associated with lower intraoperative hypotension burden and better postoperative recovery indicators. Given the retrospective observational design and potential residual confounding, these findings should be interpreted cautiously.