Consequences of the addition of nitrous oxide to anesthesia during pneumoperitoneum in videolaparoscopic surgeries

The use of pneumoperitoneum during videolaparoscopic surgeries activates neuroendocrine mechanisms, and causes cardiovascular and hormonal changes. The aim of this study was to evaluate the effects of the addition of nitrous oxide, to maintain adequate anesthetic levels, on the cardiovascular sympathetic response and in the expired concentration of sevoflurane (ECsevo) during pneumoperitoneum, by evaluating hemodynamic parameters, BIS, and SEF95%, during videolaparoscopic cholecystectomies.

Thirty-one patients, physical status ASA I and II, ages 19 to 76 years, were included in the study. Anesthetic induction was accomplished with sufentanyl 0.3 microg kg(-1)), propofol (2.5 mg kg(-1)), and cisatracurium (0.15 mg kg(-1)). During the maintenance phase of anesthesia, the dose of ECsevo was adjusted to maintain BIS between 40 and 60. The administration of increasing concentrations of nitrous oxide, 20%, 40%, and 60%, was initiated after inducing pneumoperitoneum. The bispectral index, SEF95%, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were evaluated at M1 - 5 minutes after the pneumoperitoneum; M2 - when the expired concentration of N2O = 20% (ECN2O = 20%); M3 - ECN2O = 40%; M4 - ECN2O = 60%.

There were no significant differences among SBP, DBP, MAP, and HR in the moments studied. There was a significant difference in ECsevo in those same moments, with a 35% reduction when M1 and M4 were compared.

When nitrous oxide is administered in association with sevoflurane during pneumoperitoneum in videolaparoscopic cholecystectomy, it provides for hemodynamic stability and reduces the amount of sevoflurane needed while, at the same time, maintaining electroencephalographic parameters compatible with adequate anesthesia.