Effects of minimal flow sevoflurane and desflurane anesthesia on hemodynamics, body temperature and anesthetic consumption

General anesthesia is achieved by administration of inhalation anesthetics in the carrier medical gas after intravenous sedative hypnotics. The amount of carrier gas determines the rate of anesthesia, its depth, and the consumption of inhaled gases and vapors. Low flow anesthesia is a technique that results in return of at least 50% of the exhaled gas after carbondioxide (CO2) absorption using the re-breathing system. Minimal flow anesthesia is a kind of low flow anesthesia technique in which fresh gas flow is reduced to 0.5 mL/min. Minimal flow anesthesia has clinical, ecological and economical advantages. The low blood-gas solubility of sevoflurane and desflurane, which are commonly used in current general anesthesia practice, and the technical superiority of modern anesthesia devices ensure that these agents are selected as suitable and safe inhalation anesthetics for low and minimal flow anesthesia. In this study, we aimed to compare the minimal flow sevoflurane and desflurane anesthesia in terms of hemodynamic parameters, body temperature, anesthetic gas consumption and cost. After the ethics committee approval, 120 patients with ASA I-II physical status over 18 years of age who underwent elective surgery for longer than 60 minute after general anesthesia were randomized into two groups: sevoflurane (Group S) or desflurane (Group D). The Dräger Perseus® A500 workstation that allows minimal flow was used. Patient characteristics as age, gender, body weight, height, body surface area were recorded. Before induction electrocardiogram, non-invasive blood pressure, pulse oximetry were monitored. Following induction nasopharyngeal body temperature, endtidal carbondioxide pressure (EtCO2) and train-of-four (TOF) monitoring were performed. In all cases, operating room temperature was kept constant. Initial vital measurements were recorded. Pre-oxygenation was performed for 3 minutes with 6 L/min to 100% oxygen in all cases. Endotracheal intubation was performed after administration of 40 mg prilocain, 2.5 mg/kg propofol, 1 µg/kg fentanyl and 0.6 mg/kg rocuronium bromide. Fractional inspirium oxygen concentration (FiO2), was reduced to 40% and fresh gas flow was 4 L/min after intubation and sevoflurane or desflurane was started as 1.5 minimal alveolar concentration (MAC) according to the patient's group. Medical air was used as carrier gas. The cases were ventilated in volume controlled mode with 6-8 mL/kg tidal volume, 12 breaths/min and 5 cmH2O positive end-expiratory pressure (PEEP). EtCO2 was maintained 30-40 mmHg. In all cases FiO2, fractional inspirium carbondioxide pressure (FiCO2), fractional inspirium agent concentration (Fiagent), fractional expirium agent concentration (Feagent) were recorded. In both groups, when the MAC value reached 0.9, fresh gas flow was reduced to 0.5 L/min and FiO2 was increased to 68%. This MAC value was maintained until the end of the case. Hearth rate, systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), and peripheral oxygen saturation (SpO2) were recorded on the 1st, 5th, 10th, 15th and 30th and then every 30 minutes; nasopharyngeal body temperature, Fiagent, Feagent, FiO2, FiCO2, MAC values, expirium minute ventilation (MVe) and EtCO2 were recorded on the 5th, 10th, 15th, 30th and then every 30 minutes after the induction. At the end of the surgery, the vaporizer was switched off and the fresh gas flow was increased (4 L/min, FiO2 100%). The patient was allowed to breath spontaneously with manual ventilation and muscle relaxant was antagonized. Eye opening command was given at the 3rd, 6th and then every minute. When the TOF ratio was 100%, extubation was carried out. The time to extubation and the eye opening time were recorded. There were no differences in patient characteristics and initial hemodynamic parameters of Group S and Group D. There were statistically significant differences between the times to reach 0.9 MAC, extubation and eye opening, anesthetic, O2 and air consumption, measurement of inhalation agent consumption with Biro's formula and Dräger Perseus® A500 algorithm in both groups. There was no significant difference between the two groups concerning other data. Sevoflurane consumption per operation was 23.6 ± 10.9 mL, and desflurane consumption was 31.6 ± 12.0 mL. Mean value for sevoflurane consumption was 11.5 ± 3.8 mL, desflurane consumption was 21.6 ± 8.1 mL by calculated Biro's formula. For Group S, oxygen consumption was 115.2 ± 34.0 L, air consumption was 49.8 ± 19.5 L, time to reach 0.9 MAC was 7.3 ± 3.2 min, extubation was 7.1 ± 2,5 min and eye opening was 10.7 ± 2.7 min. For Group D, oxygen consumption was 95.7 ± 19.6 L, air consumption was 32.5 ± 11.8 L, time to reach 0.9 MAC was 4.2 ± 1.5 min, extubation was 6.1 ± 1.8 min and eye opening was 7.9 ± 2.2 min. With minimal gas flow; the times to reach target MAC, time to extubation and eye opening were significantly faster for desflurane as compared to sevoflurane and anesthetic, oxygen and air consumption in desflurane anesthesia were less than sevoflurane. With these findings, we can say that desflurane has a faster anesthetic induction and recovery times with lower anesthetic consumption. We concluded that minimal flow desflurane anesthesia has more favorable results than minimal flow sevoflurane anesthesia; however, these results should be supported by further studies.