Causes of arterial hypotension during anesthetic induction with propofol investigated with perfusion index and ClearSightTM in young and elderly patients

BACKGROUND: Mechanism underlying the hypotension during anesthetic induction in elderly patients is inferred to differ from that in younger patients due to structural changes in arteries. The aim of the study was to determine if a decrease in cardiac output (CO) or systemic vascular resistance (SVR) is the main mechanism of the hypotension.METHODS: Fifty-six patients comprising 28 healthy elderly patients aged 75-90 years (group E) and 28 healthy younger patients aged 20-40 years (group Y) were enrolled. General anesthesia was induced with propofol (1.2 mg/kg, group E; 2 mg/kg, group Y), remifentanil (0.15 µg/kg/min, group E; 0.3 µg/kg/min, group Y) and rocuronium. Primary outcome was to compare serial changes in PI of Radical-7TM, SVR, CO and stroke volume variations (SVV) of ClearSightTM (Edwards Lifesciences Corp., Irvine, CA, USA) during the five-minute period from propofol administration until intubation.RESULTS: The degree of increase in PI and reduction in SVR in group Y were significantly greater than those in group E (P<0.01 with repeated measure ANOVA). The degree of reduction in CO and increase in SVV were significantly larger in group E (P<0.01). All values of mean arterial blood pressure measured during the five-minute correlated negatively with PI in group Y (r=0.44, P<0.01) and positively with CO in group E (r=0.4, P<0.01).CONCLUSIONS: The main mechanisms of hypotension during anesthetic induction contribute to the decrease in CO in elderly and reduction of SVR in younger. PI only shows the vascular tone of a finger but can be a surrogate for SVR.