Respiratory effects of sevoflurane

The respiratory effects of sevoflurane were studied in seven patients and compared with values obtained in another seven patients anesthetized with halothane. Resting ventilation, resting PaCO2, and ventilatory response to CO2 were measured awake and at 1.1 and 1.4 MAC levels of both anesthetic agents. We found that with sevoflurane, tidal volume and the slopes of the CO2 response curves decreased and PaCO2 increased with increasing depth of anesthesia, as with other inhaled anesthetics. A compensatory increase in respiratory frequency was not enough to prevent a decrease in minute volume with increasing depth of anesthesia. At 1.1 MAC, sevoflurane produced almost the same degree of respiratory depression as halothane. At 1.4 MAC, sevoflurane produced more profound respiratory depression than halothane.     

The acute hypoxic ventilatory response under halothane,isoflurane, and sevoflurane anaesthesia in rats*

The relative order of potency of anaesthetic agents on the hypoxic ventilatory response has been tested in humans, but animal data are sparse. We examined the effects of 1.4, 1.6, 1.8, and 2.0 MAC halothane, isoflurane, and sevoflurane on phrenic nerve activity in euoxia (baseline) and during acute normocapnic hypoxia (inspired oxygen fraction 0.09) in adult male Sprague‐Dawley rats. With halothane, all animals became apnoeic even in euoxia, and the hypoxic response was completely abolished at all anaesthetic levels. With isoflurane, 5 of 14 animals exhibited phrenic nerve activity in euoxia at 1.4 MAC and demonstrated a hypoxic response (302% of baseline activity), but all became apnoeic and lost the hypoxic response at higher doses. With sevoflurane, phrenic nerve activity and a hypoxic response was preserved in at least some animals at all doses (i.e. even the highest dose of 2.0 MAC). Similar to the rank order of potency previously observed in humans, the relative order of potency of depression of the hypoxic ventilatory response in rats was halothane (most depressive) > isoflurane > sevoflurane (p = 0.01 for differences between agents).     

A Comparison of the Respiratory Effects of Sevoflurane and Halothane in Infants and Young Children

Background: This study compared the respiratory effects of sevoflurane with those of halothane in anesthetized infants and young children.

Methods: Infants were randomized to receive 1 minimum alveolar concentration (MAC) halothane or sevoflurane in a mixture of nitrous oxide and oxygen. Anesthetic management included the use of a laryngeal mask. Flow, airway pressure, and the end-tidal carbon dioxide pressure (PETCO(2)) were measured during spontaneous ventilation and airway occlusions. Respiratory inductive plethysmography was used to assess chest wall motion.

Results: Measurements were obtained in 30 infants and young children (mean (SD) age, 14.5 (5.9) months), 15 of whom received sevoflurane and 15 received halothane. Some respiratory depression, as indicated by a PETCO(2) of 45 mmHg (6 kPa), was present in both groups. Minute ventilation and respiratory frequency were significantly lower during sevoflurane than halothane anesthesia (4.5 compared with 5.4 (1/m2)/min, and 37.5 compared with 46.7 breaths/min, respectively, P < 0.05). There was no difference in respiratory drive, but the shape of the flow waveform differed according to anesthetic agent, with peak inspiratory flow reached later, and peak expiratory flow reached earlier, in the sevoflurane group. There was also significantly less thoracoabdominal asynchrony during sevoflurane anesthesia.     

The stress reaction in the recovery phase from halothane and isoflurane anesthesia

This study was undertaken to investigate the influences of halothane and isoflurane as well as different extubation techniques on the endocrine stress response during recovery from general anesthesia. Forty patients scheduled for herniorrhaphy and cholecystectomy were randomly allocated to 4 groups: 20 received halothane and 20 received isoflurane anesthesia. Within the halothane and isoflurane groups, 10 patients each were extubated during anesthesia (1/2 MAC) and a further 10 had awake extubation. Premedication, induction of anesthesia, and intraoperative anesthetic management were standardized in all groups. Plasma levels of endocrine stress parameters as well as mean arterial pressure (MAP), heart rate (HR), and arterial oxygen saturation (SaO2) were measured at nine time points up to 60 min after extubation. Biometric data and duration of operation and anesthesia were comparable in all groups. In the recovery period, epinephrine levels were higher in the isoflurane groups than in the halothane groups (P = 0.02). With respect to time course, earlier and more marked increases of epinephrine, norepinephrine, and antidiuretic hormone (ADH) levels were observed in the isoflurane groups compared to the halothane groups (P less than 0.01), representing the more rapid elimination of isoflurane. The sympathoadrenergic stress response was more pronounced in patients with extubation during anesthesia than in those with awake extubation: epinephrine levels were slightly higher and group levels of norepinephrine were significantly increased (P = 0.02). No influence of the extubation techniques was observed on ADH, ACTH, and cortisol levels or on MAP, HR, or SaO2. In summary, extubation during anesthesia did not reduce the endocrine stress response. It is concluded that awake extubation should be preferred unless the operation or the patient's condition requires extubation during anesthesia.     

The respiratory effects of isoflurane, enflurane and halothane in spontaneously breathing children

The respiratory effects of halothane, isoflurane and enflurane were assessed during nitrous oxide anaesthesia (N2O 50%) in three groups of unstimulated, spontaneously breathing children who weighed 10-20 kg and were aged 1-6 years. Respiratory variables were measured or calculated from capnographic and pneumotachographic recordings at three multiples of minimal alveolar concentration (MAC). The slope of the carbon dioxide response was measured. Similar increases in end tidal carbon dioxide were found for the three agents at each MAC multiple, and similar decreases in tidal volume and in the slope of the ventilatory response to carbon dioxide. A dose-related tachypnoea occurred with halothane and a significant decrease in the duration of inspiration and the duration of each breath at the deepest level of anaesthesia. A significant increase in both these times occurred with enflurane, and a decrease in respiratory rate. No change in respiratory rate occurred with isoflurane at increasing alveolar concentrations whereas at each level of anaesthesia inspiratory time was significantly reduced.     

The effects of volatile anesthetics on the Q-Tc interval

OBJECTIVE: To examine the effects of halothane, isoflurane, and sevoflurane on Q-Tc interval (corrected for heart rate) during inhalation induction of anesthesia. DESIGN: Prospective, double-blind, randomized study. SETTING: Departments of Cardiology and Anesthesiology in a university hospital. PARTICIPANTS: Patients undergoing noncardiac surgery. INTERVENTIONS: A total of 65 American Society of Anesthesiologists physical status I-II patients, aged 16 to 50 years, undergoing general anesthesia, were randomly allocated to receive halothane, isoflurane, or sevoflurane. MEASUREMENTS AND MAIN RESULTS: The time to reach the predetermined end-tidal concentrations of 3 minimum alveolar concentration was 6 to 10 minutes. When compared with preinduction values, heart rate decreased after halothane (p < 0.01) and sevoflurane (p < 0.05) administration; in contrast, heart rate increased after induction of anesthesia with isoflurane (p < 0.05). The mean QRS intervals were not significantly changed after halothane, isoflurane, or sevoflurane. The Q-Tc interval was increased with isoflurane compared with baseline (465 +/- 23 v 441 +/- 18 msec, p < 0.01), not changed with sevoflurane (441 +/- 17 v 434 +/- 19 ms, p > 0.05), and shortened with halothane (426 +/- 23 v 445 +/- 21 msec, p < 0.01). CONCLUSION: Sevoflurane or halothane may be preferred to isoflurane in patients with conditions that are known to induce a prolonged Q-Tc interval. The effects of Q-Tc interval changes resulting from different anesthetic agents on morbidity and the incidence of arrhythmias during anesthesia warrant further investigation.     

A comparative evaluation of inhaled halothane, isoflurane, and sevoflurane during acute normovolemic hemodilution in dogs

The hemodynamic response to acute normovolemic hemodilution (ANH) can be affected by the anesthetics used. We randomized 18 mongrel dogs to undergo ANH with 3 different inhaled anesthetics: halothane, isoflurane, or sevoflurane. Hemodynamics, oxygen transport, and gastric pH were measured before blood withdrawal, at the end of hemodilution, and 30 and 60 min after the end of hemodilution. The baseline measurements of all hemodynamic variables were similar among groups, with the exception of heart rate, which was more rapid in the sevoflurane group. Thirty minutes after hemodilution, the cardiac index increased 88%, 86%, and 157% in the halothane, isoflurane, and sevoflurane groups, respectively, whereas arterial-venous oxygen differences and oxygen consumption were larger in the halothane group compared with the isoflurane and sevoflurane groups. Gastric pH obtained by tonometry did not change and was not different among groups. Because the hemodynamic response to ANH was not blunted, all three anesthetics may be safely used for the maintenance of anesthesia.     

Comparative effects of halothane, isoflurane, and sevoflurane on the liver with hepatic artery ligation in the beagle.

Recently, there has been increasing interest in the alterations in splanchnic and hepatic circulation and preservation of hepatic oxygenation and function during anesthesia and surgery. However, the effects of volatile anesthetics under a condition of marginal hepatic oxygen supply are not well understood. Using a crossover design, we therefore studied the effects of equianesthetic concentrations (1.5 MAC) of halothane, isoflurane, and sevoflurane on hepatic oxygenation and function in nine beagles in which the hepatic artery had been ligated. Portal blood flow was measured by an electro-magnetic flow meter. Hepatic function was assessed by indocyanine green elimination kinetics. While cardiac output and mean arterial pressure were greater during halothane anesthesia than during isoflurane and sevoflurane anesthesia, portal blood flow and hepatic oxygen supply were significantly less during halothane and sevoflurane anesthesia than during isoflurane anesthesia. With regard to hepatic oxygen uptake, there was a significant difference between halothane (2.7 +/- 1.2 ml.min-1 x 100 g-1) and sevoflurane (3.7 +/- 2.0 ml.min-1 x 100 g-1; P less than 0.05). Consequently, the hepatic oxygen supply/uptake ratio and the hemoglobin oxygen saturation and oxygen partial pressure in hepatic venous blood during sevoflurane anesthesia were significantly less than they were with the other anesthetics. Indocyanine green clearance was better preserved during sevoflurane anesthesia (39.7 +/- 12.0 ml.min-1) than during halothane anesthesia (30.9 +/- 8.4 ml.min-1; P less than 0.05). We conclude that sevoflurane is accompanied by a smaller oxygen supply/uptake ratio than is halothane and isoflurane, while it preserves hepatic function.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebrovascular carbon dioxide reactivity during general anesthesia: a comparison between sevoflurane and isoflurane

We compared cerebrovascular carbon dioxide reactivity during the administration of sevoflurane and isoflurane anesthesia by measuring cerebral blood flow velocity (CBFV) as an indirect measurement of cerebral blood flow. Thirty patients, 20-70 yr old, undergoing lower abdominal surgery and without known cerebral or cardiovascular system disease, were randomly assigned to either sevoflurane or isoflurane treatment groups. Anesthesia was induced with thiopental 5 mg/kg IV and maintained with either sevoflurane or isoflurane in 67% nitrous oxide and oxygen. The CBFV and pulsatility index (PI) of the left middle cerebral artery were monitored with transcranial Doppler. The P(ETCO)2 was increased stepwise from 20 to 50 mm Hg by changing the respiratory rate with a constant tidal volume. At every 5-mm Hg stepwise change in P(ETCO)2, CBFV and PI were recorded. CBFV increased with increasing P(ETCO)2. CBFV was significantly smaller in the isoflurane group at P(ETCO)2 = 20-40 mm Hg than in the sevoflurane group. The rate of change of CBFV with changes in CO2 was larger in the isoflurane group than in the sevoflurane group. PI was constant over time and was not different between groups. In conclusion, hypocapnia-induced reduction of intracranial pressure might be more effective during the administration of isoflurane than sevoflurane. IMPLICATIONS: Changes in cerebral blood flow caused by the changes of carbon dioxide tension are greater during the administration of isoflurane anesthesia compared with sevoflurane anesthesia. Attempts to decrease intracranial pressure by decreasing carbon dioxide tension may be more successful during isoflurane than sevoflurane anesthesia administration.     

The anticonvulsant effects of volatile anesthetics on lidocaine-induced seizures in cats

Large concentrations of sevoflurane and isoflurane, but not halothane, induce spikes in the electroencephalogram. To elucidate whether these proconvulsant effects affect lidocaine-induced seizures, we compared the effects of sevoflurane, isoflurane, and halothane in cats. Fifty animals were allocated to 1 of 10 groups: 70% nitrous oxide (N2O), 0.6 minimum alveolar anesthetic concentration (MAC) + 70% N2O, 1.5 MAC + 70% N2O, and 1.5 MAC of each volatile agent in oxygen. Lidocaine 4 mg x kg(-1) x min(-1) was infused IV under mechanical ventilation with muscle relaxation. Electroencephalogram in the cortex, amygdala, and hippocampus and multiunit activities in the midbrain reticular formation (R-MUA) were recorded. Lidocaine induced spikes first from the amygdala or hippocampus in the 70% N2O and halothane groups and from the cortex in the sevoflurane and isoflurane groups. Lidocaine induced seizures in all cats in the 70% N2O and 0.6 MAC + N2O groups. Seizure occurrence was reduced in the 1.5 MAC + N2O group (P < 0.05 versus 70% N2O). The onset of seizure was delayed in the 0.6 MAC + N2O and 1.5 MAC groups for sevoflurane and isoflurane, but not for halothane, compared with the 70% N2O group (P < 0.05). Lidocaine increased R-MUA with seizure by 130%+/-56% in the 70% N2O group. The increase of R-MUA with seizure was more suppressed in the volatile anesthetic groups than in the 70% N2O group (P < 0.05). In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased. IMPLICATIONS: Increasingly, epidural blockade is combined with general anesthesia to achieve stress-free anesthesia and continuous pain relief in the postoperative period. In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased.     

The comparative cardiovascular effects of sevoflurane with halothane and isoflurane

Using closed chest dogs, the cardiovascular effects of sevoflurane were compared with those of halothane and isoflurane in equipotent doses of 1.0, 1.5, 2.0, 2.5 and 3.0 MAC. They were evaluated by the changes of arterial blood pressure, central venous pressure, pulmonary artery pressure, maximum rate of left ventricular pressure rise (LV dp/dt), cardiac output and coronary sinus blood flow. The suppression of left cardiac function by sevoflurane was less than that of halothane, but was greater than that of isoflurane. Heart rate, systemic vascular resistance with sevoflurane were slightly lower than that of isoflurance. The coronary sinus blood flows with sevoflurane and isoflurane were significantly (P < 0.05 at 1.0 MAC, P < 0.005 at 2.0 MAC) higher than halothane. There was no significant difference on coronary sinus flow between sevoflurane and isoflurane. The depth of anesthesia could be quickly changed by adjustment of inspired sevoflurane concentration in comparison with the other two anesthetics.(Kazama T, Ikeda K: The comparative cardiovascular effects of sevoflurane with halothane and isoflurane. J Anesth 2: 63–68, 1988)     

Effects of isoflurane, sevoflurane, and halothane on myofilament Ca2+ sensitivity and sarcoplasmic reticulum Ca2+ release in rat ventricular myocytes

BACKGROUND: The aim of this study was to describe and compare the effects of isoflurane, sevoflurane, and halothane at selected concentrations (i.e., concentrations that led to equivalent depression of the electrically evoked Ca2+ transient) on myofilament Ca2+ sensitivity, sarcoplasmic reticulum (SR) Ca2+ content, and the fraction of SR Ca2+ released during electrical stimulation (fractional release) in rat ventricular myocytes. METHODS: Single rat ventricular myocytes loaded with fura-2 were electrically stimulated at 1 Hz, and the Ca2+ transients and contractions were recorded optically. Cells were exposed to each anesthetic for 1 min. Changes in myofilament Ca2+ sensitivity were assessed by comparing the changes in the Ca2+ transient and contraction during exposure to anesthetic and low Ca2+. SR Ca2+ content was assessed by exposure to 20 mm caffeine. RESULTS: Isoflurane and halothane caused a depression of myofilament Ca2+ sensitivity, unlike sevoflurane, which had no effect on myofilament Ca2+ sensitivity. All three anesthetics decreased the electrically stimulated Ca2+ transient. SR Ca2+ content was reduced by both isoflurane and halothane but was unchanged by sevoflurane. Fractional release was reduced by both isoflurane and sevoflurane, but was unchanged by halothane. CONCLUSIONS: Depressed myofilament Ca2+ sensitivity contributes to the negative inotropic effects of isoflurane and halothane but not sevoflurane. The decrease in the Ca2+ transient is either responsible for or contributory to the negative inotropic effects of all three anesthetics and is either primarily the result of a decrease in fractional release (isoflurane and sevoflurane) or primarily the result of a decrease in SR Ca2+ content (halothane).     

Tidal breathing technique for induction of anaesthesia with high concentration of sevoflurane, isoflurane or halothane in infants undergoing cardiac surgery

Aims nduction characteristics of sevoflurane were compared with isoflurane and halothane in 45 acyanotic infants undergoing surgery for congenital heart disease. Methods Infants were randomized into three groups of 15 each. None of them received premedication. In group I induction was done with 8% sevoflurane in 100% oxygen, in group II with 5% isoflurane in 100% oxygen and in group III with 4% halothane in 100% oxygen. Induction time, intubation time, haemodynamic variables and side effects like coughing, laryngospasm, breatholding and excessive crying were noted. Results The mean induction time taken as loss of eyelash reflex was significantly lower in sevoflurane group (52.80±8.5 seconds) as compared to isoflurane (196.80±49.13 seconds) and halothane groups (168.72±9.1 seconds) (p value <0.001). The mean intubation time in sevoflurane group was 2.97±0.48 minutes followed by halothane group (5.10±2.9 minutes) and isoflurane group (6.70±1.77 minutes) (p value < 0.001). The incidence of coughing and laryngospasm was observed in 6% (1 in 15), each in sevoflurane and halothane groups and 20% (3 in 15) cases in isoflurane group. Haemodynamics were comparable in both sevoflurane and isoflurane groups. However in halothane group significant decrease in mean arterial pressure was observed. Conclusion Sevoflurane anaesthesia is a better alternative for induction in infants undergoing cardiac surgery as compared to isoflurane and halothane. (Ind J Thorac Cardiovasc Surg, 2001; 17:233-237)     

Sevoflurane anesthesia maintains reflex tachycardia on position change from supine recumbent to head-up tilt

This study evaluated the effects of inhalational anesthetics on hemodynamic changes in response to head-up tilt in humans. Twenty-four patients were randomly divided into three groups that received either halothane, isoflurane, or sevoflurane. Changes in heart rate, blood pressure, and plasma norepinephrine concentrations were determined before and during head-up tilt position in the awake and anesthetized state. Head-up tilt caused a significant increase in the heart rate, concomitantly with a decrease or no significant changes in systolic blood pressure in the awake state. However, under 2 minimum alveolar concentrations (MAC) of halothane and isoflurane anesthesia, the heart rate did not significantly change during head-up tilt in spite of significant decreases in systolic blood pressure. In contrast, under 2 MAC of sevoflurane anesthesia, the heart rate significantly increased during head-up tilt. Plasma norepinephrine did not significantly alter during head-up tilt in the awake as well as the anesthetized state. These results suggest that sevoflurane maintains an increase in heart rate in response to head-up tilt, whereas halothane and isoflurane attenuate the response.     

不同麻醉下老年高血压患者围术期心肌损伤的比较

目的 比较不同麻醉下老年高血压患者围术期心肌损伤的程度,为老年高血压患者选择适宜的麻醉方法.方法 择期行胸外科手术的老年高血压患者36例,年龄64岁,ASA Ⅱ或Ⅲ级,高血压Ⅱ级,高血压危险程度为中、高危险组,随机分为七氟醚组(S组)、异氟醚组(Ⅰ组)和异丙酚组(P组),每组12例.插管成功后至术毕,S组和I组呼气末吸入麻醉药浓度分别为1.7%、1.2%;P组静脉靶控输注异丙酚,血浆靶浓度2～3μg/ml.分别于麻醉前、气管插管后、手术探查后、拔除气管导管后即刻记录心电图ST段水平.于麻醉前、手术开始1 h、术毕、术后3、6、12、24 h抽取上肢静脉血,采用ELISA法测定血浆心肌肌酸激酶同工酶(CK-MB)活性和心肌肌钙蛋白I(cTnI)、白细胞介素-6(IL-6)、C反应蛋白(CRP)、可溶性细胞间粘附分子-1(sICAM-1)的浓度.结果 拔除气管导管后即刻P组ST段水平明显低于S组和I组(P<0.05);与麻醉前比较,手术开始至术毕24 h各组血浆CK-MB活性、cTnI、IL-6、CRP和slCAM-1浓度明显升高(P<0.05);S组和I组术后24 h血浆cTnI,IL-6、CRP和sICAM浓度明显低于P组(P<0.05).结论 采用七氟醚或异氟醚复合麻醉时较采用异丙酚复合麻醉时老年高血压患者心肌损伤程度轻,围术期的炎性反应减轻;老年高血压患者宜采用吸人麻醉.     

Oral clonidine does not change ventilatory response to carbon dioxide in sevoflurane-anesthetized children

BACKGROUND: Clonidine is a useful premedicant for pediatric anesthesia. The drug has potential for ventilatory depression. The aim of the current study was to determine the effects of clonidine premedication on the ventilatory response to hypercapnia during sevoflurane anesthesia using the carbon dioxide (CO(2)) steady state method. METHODS: Sixty children (3-13 yr) were assigned to receive clonidine 4 microg x kg(-1) or placebo. Anesthesia was maintained with spontaneous breathing and 2% sevoflurane. Minute ventilation (VE), respiratory rate (RR), endtidal CO(2) pressure (P(ECO(2)), and arterial hemoglobin oxygen saturation (SpO2) were measured with a facemask tightly fitted before and during 7% CO(2) inhalation. RESULTS: Compared with placebo, oral clonidine failed to reduce VE volume before CO(2) loading under general anesthesia with 2% sevoflurane. Inhalation of CO(2) increased VE. Oral clonidine did not attenuate the increase in VE induced by hypercapnic challenge under sevoflurane anesthesia. There were no differences in RR, P(ECO(2), or SpO2 between the placebo and clonidine groups before and during CO(2) loading. CONCLUSION: These data suggest that oral clonidine is a suitable premedication for sevoflurane anesthesia under spontaneous breathing conditions in children.     

Effects of four volatile anesthesics on postanesthetic ventilation: a comparison of halothane,enflurane, isoflurane,and sevoflurane

To investigate the effects of four volatile anesthetics (halothane, enflurane, isoflurane, and sevoflurane) on postanesthetic ventilation and levels of consciousness, we enrolled 24 patients undergoing tympanoplasty in this study. Anesthesia was maintained with 67% nitrous oxide and one of four volatile anesthetics. We measured end-tidal carbon dioxide concentration (C_ETco₂), minute volume ( ) and respiratory rate (RR), and determined the volatile anesthetic concentration in whole arterial blood (C_BAnesth) and arterial carbon dioxide tension (Paco₂) at 20 min and 2h after tracheal extubation. We also observed the level of consciousness (awake, drowsy, and asleep) before the measurement. Ventilatory variables were similar among the four groups at 20 min, although the ratio of volatile anesthetic concentration in the alveoli to the minimum alveolar concentration (MAC) (C_AAnesth/MAC ratio) calculated from C_BAnesth in the halothane group was twice those in the other groups. In the halothane group, Paco₂ was significantly higher, and and RR were significantly lower compared with the isoflurane and sevoflurane groups at 2h. Halothane tended to prolong the recovery of levels of consciousness. We conclude that isoflurane and sevoflurane provide clinical advantages over halothane on postanesthetic ventilation and recovery of levels of consciousness.     

Recovery from Sevoflurane Anesthesia: A Comparison to Isoflurane and Propofol Anesthesia

Backgroud: Sevoflurane has a lower blood:gas partition coefficient than isoflurane, which may cause a more rapid recovery from anesthesia; it also might cause faster emergence times than for propofol-based anesthesia. We evaluated a database that included recovery endpoints from controlled, randomized, prospective studies sponsored by Abbott Laboratories that compared sevoflurane to isoflurane or propofol when extubation was planned immediately after completion of elective surgery in adult patients.

Methods: Sevoflurane was compared to isoflurane in eight studies (N = 2,008) and to propofol in three studies (N = 436). Analysis of variance was applied using least squares method mean values to calculate the pooled mean difference in recovery endpoints between primary anesthetics. The effects of patient age and case duration also were determined.

Results: Sevoflurane resulted in statistically significant shorter times to emergence (-3.3 min), response to command (-3.1 min), orientation (-4.0 min) and first analgesic (-8.9 min) but not time to eligibility for discharge (-1.7 min) compared to isoflurane (mean difference). Times to recovery endpoints increased with increasing case duration with isoflurane but not with sevoflurane (patients receiving isoflurane took 4-5 min more to emerge and respond to commands and 8.6 min more to achieve orientation during cases longer than 3 hr in duration than those receiving sevoflurane). Patients older than 65 yr had longer times to orientation, but within any age group, orientation was always faster after sevoflurane. There were no differences in recovery times between sevoflurane and propofol.     

EFFECTS OF HALOTHANE, ISOFLURANE AND ENFLURANE ON VENTILATION IN CHILDREN

The ventilatory effects of halothane in eight children werecompared with those of isoflurane in eight children and enfluranein six children. All studies were completed before surgery commenced,and the children received no preopera-tive medication. The depressionof ventilation produced by the three agents increased in a dose-relatedfashion as the alveolar concentrations were increased, and thedepression of ventilation that they produced in oxygen was greaterthan that produced by equipotent concentrations in nitrous oxide.While the increase in ventilatory frequency and the decreasein T_E associated with increasing concentrations of halothanewere statistically significant (P < 0.05), the increase infrequency associated with isoflurane was not, although it wassufficient to maintain the end-tidal and arterial-ized venousPco, in the isoflurane group at a value which did not differsignificantly from that in the halothane group. Profound depressionof ventilation was produced in the children by enflurane, clearlybecause no increase in ventilatory frequency was associatedwith its use. It was evident that the ventilatory effects ofthe three volatile agents in unstimulated children are verysimilar to those described elsewhere in the adult. There wasno difference of any clinical significance between the degreeof depression of ventilation produced by halothane and isofluranein children.     

Sevoflurane reduced but isoflurane maintained hepatic blood flow during anesthesia in man

The indocyanine green (ICG) clearance rate (K) and estimated total hepatic blood flow (THBF) were studied by the single injection technique. The THBF was estimated from the calculated circulating blood volume and the fixed extraction rate. The blood concentration of ICG was determined by the finger piece technique. Twenty-seven patients were randomly divided into three groups of nine and received 67% nitrous oxide, 33% oxygen, and the following volatile anesthetics: 0.8% halothane, 1.2% isoflurane, or 1.7% sevoflurane. ICG (0.5 mg·kg⁻¹) was administered intravenously and K was determined three times following the injection. The K value in the halothane and sevoflurane groups decreased significantly 1 h after induction of anesthesia: from 0.188±0.048 to 0.142±0.029 in the halothane group and from 0.178±0.027 to 0.155±0.021 in the sevoflurane group. There was no significant change in the K value in the isoflurane group throughout the study.