Propofol fails to attenuate the cardiovascular response to rapid increases in desflurane concentration

Abstract

Background: A rapid increase in desflurane concentration to greater than 1 MAC transiently increases heart rate, arterial blood pressure, and circulating catecholamine concentration. Because propofol decreases sympathetic outflow, it was hypothesized that propofol would blunt these responses. Methods: To test this hypothesis, five healthy male volunteers were studied three times. After induction of anesthesia with 2 mg · kg -1 propofol, anesthesia was maintained with 4% end-tidal desflurane in oxygen (0.55 MAC) via an endotracheal tube for 32 min. On separate occasions, in random order, either no propofol or 2 mg · kg -1 propofol was administered either 2 or 5 min before increasing end-tidal desflurane concentration from 4% to 8%. Results: Without propofol pretreatment, the increase to 8% desflurane transiently increased heart rate (from 63 ± 3 beats/min to 108 ± 5 beats/min, mean ± SEM; P < 0.01), mean arterial pressure (from 73 ± 1 mmHg to 118 ± 6 mmHg; P < 0.01), and epinephrine concentration (from 14 ± 1 pg · ml -1 to 279 ± 51 pg · ml -1; P < 0.05). There was no significant change in norepinephrine concentration (from 198 ± 37 pg · ml -1 to 277 ± 46 pg · ml -1). The peak plasma epinephrine concentration was attenuated by each propofol pretreatment (158 ± 35 pg · ml -1, propofol given 2 min before, and 146 ± 41 pg · ml -1, propofol given 5 min before; P < 0.05), but neither propofol pretreatment modified the cardiovascular or norepinephrine responses. Conclusions: Although able to blunt the increase in epinephrine concentration, propofol 2 mg · kg -1 propofol does not attenuate the transient cardiovascular response to a rapid increase in desflurane concentration to greater than 1 MAC.