Nakasuji M et al. – A decrease in systemic vascular resistance (SVR), not cardiac output (CO), is the main mechanism of hypotension seen during spinal anesthesia in elderly patients.

• Records from 60 consecutive patients over 80years of age, who underwent hip fracture repair (intramedullary nail or compression hip screw) during spinal anesthesia were studied.
• After injection of isobaric 0.5% bupivacaine in the L3-L4 intervertebral space in the lateral decubitus position, patients were turned supine.
• Acetate Ringer’s solution (300mL) was infused over 30minutes after subarachnoid puncture.
• A decrease in systolic arterial pressure to less than 100mmHg was treated with an intravenous injection of 5mg ephedrine.
• The hypotension group (n=18) comprised patients who required ephedrine during the 30 minutes after the puncture, and the nonhypotension group (n=42) consisted of patients who maintained stable arterial pressure with crystalloid infusion only.
• Cardiac output (CO) and stroke volume variation (SVV) every 20seconds using the Vigileo-FloTrac system continuously from arrival in the operating room (OR) to 30minutes after the subarachnoid puncture were recorded.
• Serial changes in systemic vascular resistance (SVR), CO, and SVV from baseline after puncture were compared between the two groups.

• The decrease in SVR over 20minutes after the puncture was significantly greater in the hypotension group than the nonhypotension group (P=0.047).
• Cardiac output was stable in the two groups.
• Stroke volume variation in the first 10minutes after the puncture increased to similar levels in the two groups, then decreased gradually to baseline.
• No significant differences were noted in circulatory parameters on arrival at the OR.