Is postspinal hypotension a sign of impaired cardiac performance in the elderly? An observational mechanistic study

Background: We have previously reported that stroke volume is reduced in a majority of elderly patients undergoing surgical repair of hip fracture before and after intrathecal injection of anaesthetic. We aimed to investigate these observations further in a prospective study of elderly patients undergoing elective hip or knee arthroplasty under spinal anaesthesia.

Methods: Patients ≥65 yr undergoing elective arthroplasty were monitored with LiDCOplus™ preoperatively (baseline), before and continuously for 45 min after spinal anaesthesia. Postspinal hypotension was defined as systolic blood pressure (bp) < 100 mm Hg or > 30% decrease from baseline. Associations between post-spinal hypotension and haemodynamic changes before (i.e. between baseline and before injection) spinal anaesthesia were analysed by logistic regression analysis.

Results: Twenty patients with a mean age of 74 (range 66-89) yr were included. Stroke volume index decreased by 14% (95% CI 9.3%-19%) before spinal anaesthesia. When patients were categorised according to post-spinal hypotension (Y/N) the patterns of haemodynamic changes differed. In the hypotensive patients, cardiac index progressively decreased whereas it increased initially in the non-hypotensive patients. Reduction of cardiac index from baseline before spinal anaesthesia was associated with increased risk of hypotension: OR 0.79 (95% CI 0.60, 0.91). The predictive value of reduced cardiac index was good (AUC under ROC curve 0.91).

Conclusions: A decrease in cardiac output from baseline before spinal anaesthesia and an inability to increase it after induction may be important features of postspinal hypotension in elderly patients.