Pharmacokinetics of Desflurane in Clinical Setting: At Two Different Flow Rate

Abstract

Introduction: Desflurane due to its favorable quality of quick wash in and wash out has gained popularity as a preferred inhalational anesthetic agent for low flow anesthesia (LFA) which can be costeffective, minimizing the operation theatre pollution. This study was conducted to assess the pharmacokinetic effects and safety of desflurane in lower flow rates. Aim:To compare the pharmacokinetics of desflurane by assessing its inspired and end tidal concentrations at fresh gas flow (FGF) of 1 and 1.5 L/min.To compare the inspired and end tidal concentrations of oxygen, nitrous oxide at 1 and 1.5 L/min FGF, to assess the safety as per adequate oxygenation and depth of anesthesia, haemodynamic stability, consumption of gases, MAC values and incidence of awareness.Materials and methods: One hundred patients were included and divided into two groups of 50 each of ASA grades I and II undergoing general anesthesia for laparoscopic abdominal surgeries. They were maintained with FGF of group A-1 L/min, group B-1.5 L/min All patients were monitored for hemodynamics, entropy, inspired and expired concentration of desflurane, oxygen, nitrous oxide, MAC values at FGF depending on the group with O 2 :N 2 O 50:50 and 5% desflurane. The recovery parameters, side effects and awareness were noted. Results:We found that Inspired and end tidal concentrations of desflurane were significantly different for both groups, but the difference between inspired and end tidal concentrations and ratio of end tidal to vaporizer setting were comparable as the duration of anesthesia increases suggesting saturation being achieved. The inspired and end tidal concentrations of oxygen were significantly different but were maintained at adequately safe levels. Hemodynamics were maintained and comparable in both the groups. The MAC values and requirements of desflurane, oxygen and nitrous oxide were higher in group B and recovery took significantly longer time. The incidence of side effects were comparable and none of the patients experienced awareness. Conclusion:The pharmacokinetics of desflurane favour the use of LFA. Conducting anaesthesia at a FGF 1 L/min was equally safe and there was no added advantage of using 1.5 L/min FGF. In today's modern era low flow anesthesia can be safely practiced and reduces the cost and environmental pollution.Clinical significance: Desflurane can be used efficiently at lower rates with the advantage of reducing the cost and not jeopardising the safety as per the oxygenation, hemodynamic stability and depth of anesthesia.