Awakening properties of isoflurane, sevoflurane, and desflurane in pediatric patients after craniotomy for supratentorial tumours.

BACKGROUND: The aim of this prospective, comparative, randomized study was to compare the inhalational anesthetics isoflurane, sevoflurane, and desflurane in pediatric patients undergoing craniotomy for excision of supratentorial tumors. We assessed early postoperative recovery outcome, intraoperative hemodynamics, and degree of brain swelling, as well as postoperative vomiting and shivering. METHODS: Sixty patients scheduled for supratentorial brain tumor excision, were randomly allocated into 1 of 3 groups (20 patients each); isoflurane, sevoflurane, and desflurane group. After IV induction of anesthesia, maintenance was achieved using the inhalational anesthetic according to the allocated group. Tracheal extubation time was the primary endpoint. The secondary endpoints included: emergence time and the interval time needed to reach Aldrete score ≥9, intraoperative degree of brain swelling, intraoperative heart rate and mean arterial blood pressure, as well as postoperative vomiting and shivering. RESULTS: The mean emergence time, extubation time, and the interval required to reach Aldrete score 9 were significantly shorter in the desflurane and sevoflurane groups than the isoflurane group. No statistically significant changes in the 3 groups regarding intraoperative brain swelling, hemodynamics, and postoperative shivering or vomiting were noted. CONCLUSIONS: Desflurane and sevoflurane can be used to facilitate early emergence from anesthesia in neurosurgical pediatric patients. Emergence times are shorter with desflurane or sevoflurane than with isoflurane. The patients who received desflurane or sevoflurane have similar intraoperative and postoperative incidence of adverse effects compared with those who received isoflurane. Thus, desflurane and sevoflurane can be considered as suitable for emergence in pediatric neurosurgical anesthesia.

Physiologically based pharmacokinetic rat model for methyl tertiary-butyl ether; comparison of selected dose metrics following various MTBE exposure scenarios used for toxicity and carcinogenicity evaluation.

There are a number of cancer and toxicity studies that have been carried out to assess hazard from methyl tertiary-butyl ether (MTBE) exposure via inhalation and oral administration. MTBE has been detected in surface as well as ground water supplies which emphasized the need to assess the risk from exposure via drinking water contamination. This model can now be used to evaluate route-to-route extrapolation issues concerning MTBE exposures but also as a means of comparing potential dose metrics that may provide insight to differences in biological responses observed in rats following different routes of MTBE exposure. Recently an updated rat physiologically based pharmacokinetic (PBPK) model was published that relied on a description of MTBE and its metabolite tertiary-butyl alcohol (TBA) binding to alpha 2u-globulin, a male rat-specific protein. This model was used to predict concentrations of MTBE and TBA in the kidney, a target tissue in the male rat. The objective of this study was to use this model to evaluate the dosimetry of MTBE and TBA in rats following different exposure scenarios, used to evaluate the toxicity and carcinogenicity of MTBE, and compare various dose metrics under these different conditions. Model simulations suggested that although inhalation and drinking water exposures show a similar pattern of MTBE and TBA exposure in the blood and kidney (i.e. concentration-time profiles), the total blood and kidney levels following exposure of MTBE to 7.5mg/ml MTBE in the drinking water for 90 days is in the same range as administration of an oral dose of 1000 mg/kg MTBE. Evaluation of the dose metrics also supports that a high oral bolus dose (i.e. 1000 mg/kg MTBE) results in a greater percentage of the dose exhaled as MTBE with a lower percent metabolized to TBA as compared to dose of MTBE that is delivered over a longer period of time as in the case of drinking water.

Listening to music during anesthesia does not reduce the sevoflurane concentration needed to maintain a constant bispectral index.

BACKGROUND: Music reduces stress responses in awake subjects. However, there remains controversy about the role of music or therapeutic suggestions during general anesthesia and postoperative recovery. We thus tested the hypothesis that intraoperative exposure to soothing music reduces the end-tidal concentration of sevoflurane (ETSevo) necessary to maintain bispectral index (BIS) near 50 during laparoscopic surgery. METHODS: Forty patients, aged 40-60 yrs, ASA I and II, undergoing laparoscopic hernias or cholecystectomy under general anesthesia were studied. All patients were connected to a BIS monitor. Anesthesia was induced with fentanyl 2 microg/kg, sevoflurane in oxygen, rocuronium (0.6 mg/kg), and maintained with sevoflurane in oxygen and 50% nitrous oxide, with an infusion of fentanyl (1 microg x kg(-1) x h(-1)). Sevoflurane was titrated to maintain BIS near 50 throughout the procedure. Patients were randomly assigned to either listen to music or not. RESULTS: The ETSevo necessary to maintain a BIS near 50 was virtually identical in patients who listened to music (1.29 +/- 0.33%) and those who did not (1.27 +/- 0.33%, P = 0.84). Patients who listened to music reported slightly less pain, but the difference was not statistically significant. Mean arterial blood pressure was slightly higher in patients who listened to music (101 +/- 11 mm Hg) than in those who did not (94 +/- 10 mm Hg, P = 0.040). CONCLUSIONS: The end-tidal concentration of sevoflurane required to maintain BIS near 50 during laparoscopic cholecystectomy was virtually identical in patients exposed to music or not. Although previous work suggests that music reduces preoperative stress and may be useful during sedation, our results do not support the use of music during surgery.

Effect-site half-time for burst suppression is longer than for hypnosis during anaesthesia with sevoflurane.

BACKGROUND: The relationship between measures of drug effect such as bispectral index (BIS) and end-tidal (ET) levels of anaesthetic agents is described by the 'effect site equilibrium half-time', t(1/2)(ke0). There are limited data available on sevoflurane t(1/2)(ke0) during routine anaesthesia and surgery. Preliminary observations suggested t(1/2)(ke0) for the degree of hypnosis as estimated by BIS is different from that for burst suppression of the electroencephalograph, occurring at 'deep' levels of anaesthesia. This study aimed to determine and compare t(1/2)(ke0) for these two 'effects'. METHODS: Large changes in ET sevoflurane were produced in 13 subjects during surgery. ET sevoflurane, BIS, and burst suppression ratio (BSR) were recorded every 10 s. Data were divided into epochs with BIS>30 (BIS) or with BSR>10% (burst suppression). Using a non-parametric modelling technique, t(1/2)(ke0) was determined for each epoch. RESULTS: There were 36 'BIS' and 20 burst suppression zones. Mean (sd) t(1/2)(ke0) for BIS was 3.48 (1.12) min and for BSR 9.9 (6.4) min. In all subjects, t(1/2)(ke0) BIS

Wash-in and wash-out curves of sevoflurane and isoflurane in morbidly obese patients.

BACKGROUND: The aim of this prospective, randomized study is to compare sevoflurane and isoflurane pharmacokinetics in morbidly obese patients. METHODS: With Ethical Committee approval and written informed consent, 14 obese patients (BMI >35 kg/m2), ASA physical status II, undergoing laparoscopic, silicone-adjustable gastric banding were randomly allocated to receive either sevoflurane (n=7) or isoflurane (n=7) as main anesthetic agents. General anesthesia was induced with 1 mg x kg-1 fentanyl, 6 mg x kg-1 sodium thiopental, and 1 mg x kg-1 succinylcholine followed by 0.4 mg kg-1 x h-1 atracurium bromide (doses were referred to ideal body weight). Intermittent positive pressure ventilation (IPPV) was applied using a Servo-900C ventilator with a nonrebreathing circuit and a 15 l x min-1 fresh gas flow (tidal volume: of 10 ml x kg-1; respiratory rate: 12 breaths/min; inspiratory to expiratory time ratio of 1:2) using an oxygen/air mixture (FiO2=50%), while supplemental boluses of thiopental or fentanyl were given as indicated in order to maintain blood pressure and heart rate values within +/-20% from baseline. After adequate placement of tracheal tube and stabilization of the ventilation parameters, 2% sevoflurane or 1.2% isoflurane was given for 30 min via a nonrebreathing circuit. End-tidal samples were collected at 1, 5, 10, 15, 20, 25 and 30 min, and measured using a calibrated infrared gas analyzer. General anesthesia was then maintained with the same inhalational agents, while supplemental fentanyl was given as indicated. After the last skin suture the inhalational agents were suspended, and the end tidal samples were collected at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 min. Then the lungs were manually ventilated until extubation. RESULTS: No differences in age, gender and body mass index were reported between the two groups. Surgical procedure required 91+/-13 in the sevoflurane group and 83+/-32 min in the isoflurane group. The FA/FI ratio was higher in the sevoflurane group from the 5th to the 30th min. Also the washout curve was faster in the sevoflurane group during the observation period; however, the observed differences were statistically significant only 30 and 60 sec after discontinuation of the inhalational agents. CONCLUSIONS: The results of this prospective, randomized study confirmed that sevoflurane provides more rapid wash-in and wash-out curves than isoflurane also in the morbid obese patient.