The effect of anesthetic technique on mortality and major morbidity after hip fracture surgery: a retrospective, propensity-score matched-pairs cohort study

INTRODUCTION: Spinal anesthesia (SA) has physiological benefits over general anesthesia (GA), but there is insufficient evidence regarding a mortality benefit. We performed a retrospective propensity score-matched cohort study to evaluate the impact of anesthetic technique on mortality and major morbidity in patients undergoing hip fracture surgery. MATERIALS AND METHODS: Clinical, laboratory and outcome data were extracted from electronic databases for patients who underwent hip fracture surgery over a 13-year period at the University Health Network in Toronto, Ontario, Canada. The anesthetic technique was documented (SA or GA), and the primary outcome was 90-day mortality. Secondary outcomes included mortality at 30 and 60 days, hospital length of stay, pulmonary embolism (PE), major blood loss and major acute cardiac events. A propensity-score matched-pair analysis was performed following a non-parsimonious logistic regression model. RESULTS: Of the 2591 patients identified, 883 patients in the SA group were matched to patients in the GA group in a 1:1 ratio. There was a weak association between SA and lower 90-day mortality (risk ratio (RR) 0.74, 95% CI 0.52 to 0.96, 99% CI 0.48 to 1.00, p=0.037). SA was also associated with a lower incidence of both PE (1.3% vs 0.5%, p<0.001) and major blood loss (7.7% vs 4.8%, p<0.001) and a shorter hospital length of stay by about 2 days (median 11.9 vs 10 days, p=0.024). There was no difference in major cardiac events or mortality at 30 and 60 days. DISCUSSION: This propensity-score matched-pairs cohort study suggests that SA is weakly associated with a lower 90-day mortality following hip fracture surgery. SA was also associated with improved morbidity evidenced by a lower rate of PE and major blood loss and a shorter hospital length of stay. Given the retrospective nature of the study, these results are not proof of causality.