Mivacurium infusion requirement and spontaneous recovery of neuromuscular transmission in children anaesthetized with nitrous oxide and fentanyl,halothane, isoflurane or sevoflurane

BACKGROUND: Forty children, aged 3-11 years, ASA I or II, were allocated at random to receive N2O/O2-fentanyl or 1 MAC halothane, isoflurane or sevoflurane-N2O/O2 anaesthesia. Mivacurium was used for muscle relaxation. METHODS: Electromyographic response of the adductor pollicis to train-of-four (TOF) stimulation, 2 Hz for 2 s, applied to the ulnar nerve at 10-s intervals was recorded using the Relaxograph (Datex, Helsinki, Finland). An intubating dose of mivacurium, 0.2 mg.kg-1 was given, and when T1 returned to 5%, muscle relaxation was maintained by continuous infusion of mivacurium, adjusted manually to maintain a stable 90-99% block. RESULTS: Halothane, isoflurane and sevoflurane groups had lower infusion requirements for mivacurium than the N2O-fentanyl group (P=0.000083). Mivacurium requirement was 18.8 +/- 6.8, 10.8 +/- 4.2, 6.9 +/- 3.9 and 9.6 +/- 5.6 microg.kg-1.min-1 for children receiving N2O/O2-fentanyl, halothane, isoflurane and sevoflurane anaesthesia, respectively. CONCLUSIONS: Spontaneous recovery from T1=10% to TOF ratio=0.7 was insignificantly prolonged from 6.3 to 12.5 min in the fentanyl group to 7-16.5 min in children anaesthetized with inhalational anaesthetics.     

Pharmacokinetic-pharmacodynamic relationship of rocuronium under stable nitrous oxide-fentanyl or nitrous oxide-sevoflurane anesthesia in children

BACKGROUND: The aim of this study was to compare pharmacokinetics and pharmacokinetic-pharmacodynamic (PK-PD) relationship of rocuronium in children anesthetized with nitrous oxide (N2O) and fentanyl or with N2O and sevoflurane. METHODS: Twenty-four children (3-11 years old, ASA PS I or II) were randomized to receive N2O/O2-fentanyl or N2O/O2-sevoflurane (one MAC) anesthesia. Neuromuscular transmission was monitored electromyographically. Initial bolus dose of rocuronium, 0.6 mg x kg(-1) was followed by continuous infusion, targeting at steady-state 95% T1 depression. Neuromuscular transmission was allowed to recover spontaneously. Plasma samples were collected at the moment of discontinuation of infusion, and 10, 20, 30, 50, 60 and 75 min afterwards. Concentrations of rocuronium were measured using high-performance liquid chromatography with electrochemical detection (HPLC-EC). Rocuronium PK was described by a two-compartment model and PD parameters were estimated using effect compartment and sigmoidal E(max) models. RESULTS: No differences in rocuronium PK parameters were observed between study groups. Clearance was 3.91 +/- 2.07 and 3.62 +/- 0.80 ml x min(-1) x kg(-1) in sevoflurane and fentanyl groups, respectively (P < 0.65). Effect compartment concentrations corresponding to 50% inhibition of T1 (EC50) were 1.41 +/- 0.45 and 2.32 +/- 1.00 microg x ml(-1) (P < 0.02), and rate constants for equilibration between plasma and effect compartment (k(e0)) values were 0.10 +/- 0.04 and 0.24 +/- 0.14 min(-1) (P < 0.009) in sevoflurane and fentanyl groups, respectively. CONCLUSIONS: Disposition of rocuronium was similar under stable N2O-fentanyl and N2O-sevoflurane anesthesia. Sevoflurane reduced rocuronium requirements as well as decreased EC50 relevant to inhibition of T1 and rocuronium transfer to effect compartment. Therefore, the potentiating effect of sevoflurane seems to be mainly of PD origin, probably due to an increased sensitivity of the neuromuscular junction.     

Comparison of recovery after intermediate duration of anaesthesia with sevoflurane and isoflurane

BACKGROUND: The purpose of this study was to compare recovery from anaesthesia after sevoflurane and isoflurane were administered to children for more than 90 min. METHODS: After parental informed consent and ethical committee approval, children aged between 2 months and 6 years, ASA I or II, were randomly allocated to sevoflurane (n=20) or isoflurane (n=20) groups. Halogenated agents were discontinued following skin closure and patients were ventilated mechanically with 100% oxygen until minimum alveolar concentration (MAC) values awake were obtained (endtidal concentrations 0.6 MAC for sevoflurane and 0.4 MAC for isoflurane). Effective perioperative analgesia was provided by a caudal block. RESULTS: The mean (+/- SD) duration of anaesthesia was 132 +/- 38 min and 139 +/- 49 min for sevoflurane and isoflurane, respectively. Early recovery occurred sooner in the isoflurane group (time to extubation was 16 +/- 7 min and 11 +/- 5 min, P<0.01; Aldrete's score at 0 min was 5.5 +/- 1.5 and 7.4 +/- 1.8, P<0.001, respectively). But the time to be fit for discharge from recovery room was similar at 136 +/- 18 min and 140 +/- 20 min, respectively. CONCLUSIONS: After intermediate duration of anaesthesia administered to children for up to 90 min, isoflurane and sevoflurane allow recovery after approximatively the same lapse of time.     

Probability of acceptable intubation conditions with low dose rocuronium during light sevoflurane anaesthesia in children

BACKGROUND: To define the rocuronium doses which would provide 50%, 90%, and 95% probability of 'acceptable' intubation conditions during light sevoflurane anaesthesia, we studied 60 children aged 2-7 years in a prospective, randomised, assessor blinded study. METHODS: After mask ventilation with 1 MAC sevoflurane/N2O for 17+/-1 (x+/-SD) min we administered rocuronium (either 0.15, 0.22, 0.3, 0.5, or 1.0 mg. kg(-1)) or placebo, and quantified the evoked force of the adductor pollicis muscle. Intubation conditions were assessed before and 2 min after injection of the test drug. RESULTS: Intubation conditions were improved significantly with rocuronium and scored 'acceptable' in 70%, 90%, and 100% of the children after injection of rocuronium 0.15, 0.22, and 0.3 mg x kg(-1), respectively. In parallel, twitch tension decreased to 53% (6-100), 26% (11-100), and 11% (0-19) of baseline (median (range)). Recovery of train-of-four ratio to 0.8 was achieved 13 (7-19), 16 (8-28), and 27 (23-44) min after injection of the respective rocuronium doses. Higher rocuronium doses did not further improve intubation conditions but only prolonged time of neuromuscular recovery. Logistic regression analysis revealed that rocuronium 0.11 (CI 0.05-0.16), 0.21 (0.14-0.28), and 0.25 (0.15-0.34) mg x kg(-1) provides a 50%, 90%, and 95% probability of 'acceptable' intubation conditions in children during 1 MAC sevoflurane/N2O anaesthesia, respectively. Furthermore, we calculated that force depression of adductor pollicis muscle to 81% (CI 72-90), 58% (42-74), and 50% (29-71) of baseline is associated with 50%, 90%, and 95% probability of 'acceptable' intubation conditions. CONCLUSIONS: Submaximal depression of muscle force with low dose rocuronium improves intubation conditions in children during light sevoflurane anaesthesia while allowing rapid recovery of neuromuscular function. However, when using low dose rocuronium neuromuscular monitoring may be helpful to detect children with inadequate response to the relaxant so as to avoid an unsuccessful intubation attempt.     

Rocuronium pharmacokinetic-pharmacodynamic relationship under stable propofol or isoflurane anesthesia

PURPOSE: To compare the pharmacokinetics, pharmacodynamics and the concentration-effect relationship of rocuronium in patients under stable propofol or isoflurane anesthesia. METHODS: Ten patients were randomized to receive fentanyl, propofol and nitrous oxide (60%) or fentanyl, thiopental, isoflurane (1.2% end-tidal concentration) and nitrous oxide (60%). To obtain good intubation conditions and maintain adequate muscle relaxation during surgery, patients received two bolus doses of rocuronium: 0.5 mg x kg(-1) (1.7 x ED95) at induction followed one hour later by 0.3 mg x kg(-1) (1 x ED95). Arterial blood samples were obtained over six hours after the second bolus dose. Plasma concentrations of rocuronium were measured using high pressure liquid chromatography. Muscle twitch tension was monitored by mechanomyography for the two doses. Pharmacokinetic and pharmacodynamic parameters were determined. RESULTS: No differences in rocuronium pharmacokinetic parameters were observed between both groups. After the second bolus, clinical duration was 20 +/- 6 min in the propofol group vs 39 +/- 8 min in the isoflurane group (P <0.05). The effect compartment concentration corresponding to 50% block, EC50, was higher under propofol anesthesia: 1008 vs 592 microg x L(-1) (P <0.05). CONCLUSION: Rocuronium body disposition is similar under stable propofol or isoflurane anesthesia. In contrast to isoflurane, propofol does not prolong the neuromuscular block. Therefore, the potentiating effect of isoflurane is of pharmacodynamic origin only, as explained by an increased sensitivity at the neuromuscular junction. In contrast with isoflurane anesthesia where the dose of rocuronium has to be decreased under stable conditions, no dose adjustment is required under propofol anesthesia.     

Rocuronium potency and recovery characteristics during steady-state desflurane, sevoflurane, isoflurane or propofol anaesthesia

We have studied the potency and recovery characteristics of rocuronium during 1.25 MAC of isoflurane, desflurane, sevoflurane or propofol anaesthesia in 84 patients using electromyography. Potency was determined by a cumulative bolus technique. The mean ED50 of rocuronium was 169 (SD 41), 126 (32), 121 (28) and 136 (25) micrograms kg-1 during propofol, isoflurane, sevoflurane and desflurane anaesthesia, respectively (ns), and ED90 values were 358 (62), 288 (29), 289 (28) and 250 (28) micrograms kg-1, respectively. The reduction in ED90 was statistically significant for all three inhalation anaesthetics (P < 0.05) compared with propofol. After 120 min, the cumulative infusion rate of rocuronium to obtain twitch depression of 90-95% was 9.0 (1.9), 6.3 (1.6), 6.1 (2.0) and 6.1 (1.1) micrograms kg-1 min-1 during propofol, isoflurane, sevoflurane and desflurane anaesthesia, respectively (P < 0.01). Recovery index was 22 (13), 27 (10), 28 (13) and 26 (14) min under propofol, isoflurane, sevoflurane and desflurane anaesthesia, respectively (ns). There were no significant differences between the three potent inhalation anaesthetics in relation to potency, infusion requirements or recovery characteristics of rocuronium.      

A comparison of antagonism of rocuronium-induced neuromuscular blockade during sevoflurane and isoflurane anaesthesia

Volatile anaesthetic agents potentiate neuromuscular blocking agents and retard their rate of reversal. We hypothesised that there was a difference in the rate of reversal of rocuronium-induced neuromuscular blockade based on the selection of inhalation agent. Thirty-eight patients undergoing elective surgical procedures received either sevoflurane or isoflurane, by random allocation. Neuromuscular blockade was induced using rocuronium 0.6 mg.kg-1 followed by continuous intravenous infusion to maintain 90% suppression of the single twitch response. Upon completion of surgery, the rocuronium infusion was discontinued, neostigmine 50 microg.kg-1 and glycopyrrolate 10 microg.kg-1 were administered. Times from reversal to T1 = 25, 50 and 60% and train-of-four ratio = 0.6 were recorded. The mean (SD) times to train-of-four ratio = 0.6 in the isoflurane and sevoflurane groups were 327 (132) and 351 (127) s, respectively. The mean (SD) times to single twitch response T1 = 25, 50 and 60% in the isoflurane group were 81 (33), 161 (59) and 245 (84) s, respectively, and in the sevoflurane group were 95 (35), 203 (88) and 252 (127) s, respectively. It is concluded that reversal of rocuronium-induced neuromuscular blockade is similar during isoflurane and sevoflurane anaesthesia.     

Neuromuscular effects of isoflurane in patients with myasthenia gravis

Seventeen myasthenia gravis and seven control patients were studied mechano (MMG)- and electromyographically (EMG) during isoflurane/oxygen/air anaesthesia. In myasthenic patients the mean train-of-four ratio and neuromuscular block (by MMG) during 1.9 MAC isoflurane anaesthesia were 55 +/- 9% and 46 +/- 12%, respectively. The correlation between simultaneous MMG and EMG measurements was excellent (r2 = 0.933, P less than 0.001). The occurrence of HLA-B8 together with acetylcholine receptor antibodies seems to predispose myasthenic patients to a neuromuscular depression produced by isoflurane. Our current and prior results show that isoflurane possesses approximately twice as strong a neuromuscular blocking effect as halothane in myasthenic patients.     

Time course of potentiation of mivacurium by halothane and isoflurane in children

We studied 40 children, aged 1-15 yr, to analyse the time course of potentiation of mivacurium produced by halothane and isoflurane. A steady infusion requirement of mivacurium to maintain 90% neuromuscular block was established during thiopentone-alfentanil-nitrous oxide- oxygen anaesthesia. Patients were then allocated randomly to receive 1 MAC end-tidal concentration of either halothane (group Hal) or isoflurane (group Iso) while neuromuscular block was maintained at 90%. Both volatile agents decreased the infusion requirements of mivacurium in an exponential manner in that maximal potentiation occurred only after 30-80 min. Maximal reduction in infusion rate (32% in group Hal and 70% in group Iso; P < 0.0001) did not depend on the age of the child but became established sooner the younger the child in the case of isoflurane (P = 0.002).      

Reversal of rocuronium with edrophonium during propofol versus sevoflurane anesthesia

BACKGROUND: The use of volatile anesthetics for maintenance of anesthesia can enhance the action of non-depolarizing muscle relaxants and interfere with the reversal of neuromuscular blockade. In this study, we studied the antagonism of rocuronium with edrophonium-atropine during propofol- versus sevoflurane-based anesthesia. METHODS: Following induction of anesthesia with propofol (2-2.5 mg kg(-1), i.v.) and fentanyl (1-2 microg kg(-1) i.v.), rocuronium 0.6 mg kg(-1) i.v. was administered to facilitate tracheal intubation. Patients were then randomized to receive either a propofol infusion (100 microg kg(-1) min(-1)) or sevoflurane (1.0%, end-tidal) in combination with nitrous oxide 66% for maintenance of anesthesia. Neuromuscular blockade was monitored using electromyography at the wrist, and reversed with edrophonium 1.0 mg kg(-1) and atropine 0.015 mg kg(-1) when the first twitch hight (T1) of the train-of-four (TOF) stimulation recovered to 25% of the baseline value. Anesthetic maintenance with propofol or sevoflurane was continued following reversal until a TOF ratio of 0.7 was attained. RESULTS: The clinical duration of action (i.e., time to 25% T1 recovery) was similar during both propofol- (39.3+/-14.6 min) and sevoflurane-based (48.1+/-19.7 min) anesthesia. However, the reversal time from 25% T1 to TOF ratio of 0.7 was significantly longer with sevoflurane [Median 2.8 (range 0.5-18.8) min] compared with propofol [1.5 (0.75-3) min] (P<0.05). CONCLUSIONS: We conclude that the clinical duration of action after a single dose of rocuronium, 0.6 mg kg(-1) i.v., was similar during both propofol- and sevoflurane-based anesthesia. However, the reversal of rocuronium-induced residual blockade was slower and more variable in the presence of sevoflurane.     

Minimum alveolar concentration of halogenated volatile anaesthetics in left ventricular hypertrophy and congestive heart failure in rats

BACKGROUND: Although many physiological and pathological conditions affect minimal alveolar concentration (MAC), there are no reliable data on the MAC for halogenated anaesthetics during left ventricular hypertrophy (LVH) and congestive heart failure (CHF). The aim of this experimental study was to determine the MAC values of halothane, isoflurane, and sevoflurane in rats, at early and later stages of cardiomyopathic hypertrophy. METHODS: LVH was induced by ascending aortic stenosis in 3-4-week-old rats. LVH and CHF in each animal were assessed weekly by echocardiography. MAC of halothane, isoflurane, and sevoflurane was determined using the tail-clamp technique in spontaneously breathing rats from each group. Response vs no-response data were analysed using logistic regression analysis. Data are medians (95% confidence interval). RESULTS: The MAC of halothane [1.30% (1.26-1.34)], isoflurane [1.52% (1.48-1.57)], and sevoflurane [2.93% (2.78-3.07)] in rats with LVH was not different from sham-operated rats [respectively, 1.23% (1.20-1.26), 1.52% (1.47-1.56), and 2.90% (2.79-3.00)]. Conversely, the MAC of halothane [1.44 (1.39-1.50)] and isoflurane [1.74 (1.69-1.78)], but not sevoflurane [2.99 (2.93-3.06)], was significantly increased in rats with CHF. CONCLUSIONS: MAC values for halothane, isoflurane, and sevoflurane were unchanged in rats with pressure-induced overload LVH. Conversely, the MAC for halothane and isoflurane, but not sevoflurane, was significantly increased in rats with CHF.     

Sevoflurane decreases bispectral index values more than does halothane at equal MAC multiples

At the minimum alveolar concentration (MAC) of inhaled anesthetics, 50% of subjects move in response to noxious stimulation. Similarly, at MAC-awake, 50% of subjects respond appropriately to command. The bispectral index (BIS) nominally measures the effect of anesthetics on wakefulness or consciousness. We postulated that the use of halothane with a larger MAC-awake/MAC ratio than sevoflurane would produce higher BIS values at comparable levels of MAC. We studied 33 unpremedicated patients anesthetized by inhalation, 18 with sevoflurane and 15 with halothane. We measured BIS before and during anesthesia at 1 MAC, both before and after tracheal intubation facilitated by fentanyl and rocuronium and then at 1.5 MAC. BIS measurements were made after meeting steady-state conditions. No surgery was performed during this study. BIS values in awake patients did not differ between the sevoflurane and halothane groups (96 +/- 2 and 96 +/- 2, mean +/- sd, respectively). At 1 MAC without and with neuromuscular blockade and at 1.5 MAC, BIS values for patients anesthetized with halothane (54 +/- 7, 56 +/- 7, and 49 +/- 7, respectively) exceeded those for patients anesthetized with sevoflurane (34 +/- 6, 34 +/- 6, and 29 +/- 5, respectively) (P < 0.0001). This finding adds to other evidence indicating that BIS is drug specific.     

The effect of halothane on mivacurium infusion requirements in adult surgical patients

Background: The extent of interaction between volatile anaesthetics and neuromuscular blocking agents depends both on the inhalational anaesthetic and the muscle relaxant. Halothane has the weakest potentiating effect on neuromuscular blocking drugs and previous studies of the interaction between halothane and mivacurium have been contradictory. We were interested in determining the effect of different levels of halothane-nitrous oxide anaesthesia on infusion requirements of mivacurium. Methods: Sixty adult surgical patients were studied. Anaesthesia was induced with thiopentone and fentanyl and intubation facilitated with mivacurium 0.15 mg kg^-1. The patients were randomly assigned to one of four study groups. The control group received nitrous oxide in oxygen (2: 1) supplemented with fentanyl, while in the other groups halothane was administered at different end-tidal concentrations: 0.19% (Group 2), 0.37% (Group 3), 0.74% (Group 4), corresponding to 0.25, 0.5 and 1.0 MAC of halothane. Neuromuscular block was kept at 95% with a closed-loop feedback infusion of mivacurium and monitored with electromyography. Plasma cholinesterase concentrations and dibucaine numbers were determined. Results: Mivacurium infusion requirements (mean±SD) were 7.5±3.1 μg kg^-1 min^-1 with nitrous oxide-fentanyl anaesthesia. In the groups receiving 0.25, 0.5 or 1.0 MAC of halothane the steady-state infusion rates of mivacurium were reduced to 6.3±2.8, 5.6±1.4 and 5.7±2.5 μg-kg^-1min^-1 (P < 0.05), respectively. There was a linear relationship between mivacurium infusion requirements and plasma cholinesterase activity. Conclusion: Halothane anaesthesia reduces mivacurium infusion requirements by 15–25% compared to nitrous oxide-fentanyl anaesthesia. Interindividual differences in the extent of this interaction are great.     

The minimum alveolar concentration (MAC) and hemodynamic effects of halothane, isoflurane, and sevoflurane in newborn swine

To determine the minimum alveolar concentration (MAC) and hemodynamic responses to halothane, isoflurane, and sevoflurane in newborn swine, 36 fasting swine 4-10 days of age were anesthetized with one of the three volatile anesthetics in 100% oxygen. MAC was determined for each swine. Carotid artery and internal jugular catheters were inserted and each swine was allowed to recover for 48 h. After recovery, heart rate (HR), systemic systolic arterial pressure (SAP), and cardiac index (CI) were measured awake and then at 0.5, 1.0, and 1.5 MAC of the designated anesthetic in random sequence. The (mean +/- SD) MAC for halothane was 0.90 +/- 0.12%; the MAC for isoflurane was 1.48 +/- 0.21%; and the MAC for sevoflurane was 2.12 +/- 0.39%. Awake (mean +/- SD) measurements of HR, SAP, and CI did not differ significantly among the three groups. Compared to the awake HR, the mean HR decreased 35% at 1.5 MAC halothane (P less than 0.001), 19% at 1.5 MAC isoflurane (P less than 0.005), and 31% at 1.5 MAC sevoflurane (P less than 0.005). Compared to awake SAP, mean SAP measurements decreased 46% at 1.5 MAC halothane (P less than 0.001), 43% at 1.5 MAC isoflurane (P less than 0.001), and 36% at 1.5 MAC sevoflurane (P less than 0.005). Mean SAP at 1.0 and 1.5 MAC halothane and isoflurane were significantly less than those measured at equipotent concentrations of sevoflurane (P less than 0.005). Compared to awake CI, mean CI measurements decreased 53% at 1.5 MAC halothane (P less than 0.001) and 43% at 1.5 MAC isoflurane (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Desflurane and isoflurane improve neurological outcome after incomplete cerebral ischaemia in rats

We have investigated the effects of isoflurane and desflurane on neurological outcome in a rat model of incomplete cerebral ischaemia. We studied 40 non-fasted male Sprague-Dawley rats, anaesthetized, intubated and ventilated mechanically with isoflurane and nitrous oxide in oxygen (FlO2 0.3). Arterial and venous catheters were inserted for measurement of arterial pressure, drug administration and blood sampling. A biparietal electroencephalogram (EEG) was recorded continuously using subdermal platinum electrodes. At completion of surgery, administration of isoflurane was discontinued (with the exception of those animals receiving isoflurane as treatment) and rats were allowed an equilibration period of 30 min according to the following procedure: group 1 (n = 10), 66% nitrous oxide in oxygen and fentanyl (bolus 10 micrograms kg-1 i.v. followed by infusion at a rate of 25 micrograms kg-1 h-1); group 2 (n = 10), 1.0 MAC of isoflurane in oxygen (FlO2 0.3) and air; groups 3 and 4 (n = 10 per group), 1.0 MAC or 1.5 MAC of desflurane in oxygen (FlO2 0.3) and air, respectively. Ischaemia was produced by combined unilateral common carotid artery ligation and haemorrhagic hypotension to 35 mm Hg for 30 min. Functional neurological deficit was evaluated for 3 days after cerebral ischaemia. At baseline, brain electrical activity was higher with fentanyl-nitrous oxide, 1.0 MAC of isoflurane and 1.0 MAC of desflurane (groups 1-3) compared with 1.5 MAC of desflurane (group 4). Neurological outcome was improved in isoflurane and desflurane anaesthetized animals (groups 2-4), regardless of the concentration used compared with fentanyl-nitrous oxide anaesthesia (group 1). The increase in plasma epinephrine and norepinephrine concentrations during ischaemia was significantly higher in fentanyl-nitrous oxide anaesthetized animals (group 1) compared with animals who received volatile anaesthetics (groups 2-4). These data suggest that cerebral protection produced by isoflurane and desflurane appears to be related to reduction in sympathetic activity rather than suppression of cerebral metabolic rate.      

Infusion requirements and reversibility of rocuronium at the corrugator supercilii and adductor pollicis muscles

Background: The aim of this study is to compare the infusion rates required to maintain a constant neuromuscular block and the reversibility of rocuronium at the corrugator supercilii muscle (CSM) and the adductor pollicis muscle (APM).
Methods: We randomly allocated 30 female patients into two groups of 15 patients each to monitor neuromuscular block at either the CSM or the APM. After induction of anaesthesia and laryngeal mask insertion, contraction of the CSM to the facial nerve stimulation or that of the APM to the ulnar nerve stimulation was quantified using an acceleromyograph during 1.0–1.5% end-tidal sevoflurane anaesthesia. All the patients received a bolus of 1 mg/kg rocuronium. When the first twitch (T1) of train-of-four (TOF) recovered to 10% of the control, rocuronium infusion was commenced and maintained at T1 of 10% of the control at the CSM or APM for 120 min. Immediately after rocuronium infusion was discontinued, the time required for 0.04 mg/kg neostigmine-facilitated recovery to a TOF ratio of 0.9 was recorded.
Results: Rocuronium infusion dose after a lapse of 120 min was significantly larger in the CSM than in the APM [7.1 (2.3) vs. 4.7 (2.6) μg/kg/min; P =0.001]. The time for facilitated recovery was shorter in the CSM than in the APM [11.4 (3.8) vs. 16.2 (6.0) min; P =0.016].
Conclusion: A larger rocuronium infusion dose was required to maintain a constant neuromuscular block at the CSM. Neostigmine-mediated reversal was faster at the CSM.     

性别因素对七氟醚增强顺阿曲库铵或罗库溴铵肌松效应的影响

目的 探讨性别因素对七氟醚增强顺阿曲库铵或罗库溴铵肌松效应的影响.方法 择期全麻手术患者240例,年龄20～60岁,ASA分级Ⅰ或Ⅱ级,BMI 20～30 kg/m2,随机分为2组(n=120):顺阿曲库铵组和罗库溴铵组,各组按性别和麻醉药再分4个亚组(n=30):女性异丙酚组、男性异丙酚组、女性七氟醚组和男性七氟醚组.各异丙酚组靶控输注异丙酚,血浆靶浓度2～6 μg/ml,各七氟醚组吸入七氟醚,于靶控输注或待呼气末七氟醚浓度稳定于1.71%5 min后,静脉注射顺阿曲库铵0.15 mg/kg或罗库溴铵0.6 mg/kg.记录肌松起效时间、肌松作用峰值时间、T1 25%恢复时间和TOFR25%恢复时间.结果 与异丙酚麻醉比较,女性患者七氟醚麻醉时,罗库溴铵TOFR 25%恢复时间延长,顺阿曲库铵肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长,男性患者七氟醚麻醉时,罗库溴铵起效时间缩短,肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长,顺阿曲库铵肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长(P＜0.05或0.01);七氟醚麻醉时与男性患者比较,女性患者罗库溴铵T1 25%恢复时间和TOFR 25%恢复时间缩短,顺阿曲库铵起效时间缩短(P＜0.05或0.01).结论 七氟醚对罗库溴铵肌松的增强作用存在性别差异,男性强于女性;对顺阿曲库铵肌松的增强作用无明显性别差异.     

Potency and time course of mivacurium block during sevoflurane, isoflurane and intravenous anesthesia

PURPOSE: To determine the potency and time course of action of mivacurium neuromuscular block under routine clinical conditions during sevoflurane, isoflurane and intravenous anesthesia. METHOD: Patients were anesthetized with nitrous oxide 66% in oxygen and 1.5 MAC sevoflurane or isoflurane or a propofol infusion, neuromuscular block being monitored using mechanomyography. Potency was determined using administration of single doses of mivacurium of 40-100 micrograms.kg-1 and construction of dose-response curves (n = 72). The onset and duration of action were determined following a bolus dose of 0.2 mg.kg-1 of mivacurium (n = 30). RESULTS: The ED50 and ED95 (with 95% confidence limits) were estimated to be 42 (35-51) and 86 (74-98) micrograms.kg-1, 52 (45-60) and 89 (72-110) micrograms.kg-1, and 53 (45-62) and 95 (81-112) micrograms.kg-1 during sevoflurane, isoflurane and propofol anesthesia respectively (P < 0.05 between sevoflurane and propofol). Following administration of the 0.2 mg.kg-1 dose, neither the times (mean +/- SD) to maximum block (1.6 +/- 0.31, 1.7 +/- 0.21 and 1.6 +/- 0.45 min, respectively) nor the times to 25 and 90% recovery of T1 (20 +/- 4.5 and 33 +/- 8.8 min, 21 +/- 3.8 and 33 +/- 6.5 min, and 18 +/- 4.1 and 28 +/- 5.8 min respectively) were different among groups. The times to recovery of TOF ratio to 0.8 were 40 +/- 10.0, 36 +/- 8.5 and 29 +/- 5.5 min in the sevoflurane, isoflurane and propofol groups respectively (P = 0.017 between the sevoflurane and propofol groups). CONCLUSIONS: Under usual conditions of clinical anesthesia the potency of mivacurium was slightly enhanced during sevoflurane compared with intravenous anesthesia but the duration of action was only minimally prolonged during sevoflurane and isoflurane anesthesia.     

Early and late reversal of rocuronium with pyridostigmine during sevoflurane anaesthesia in children

This study investigated the effect of pyridostigmine administered at different levels of recovery of neuromuscular function after rocuronium during sevoflurane anaesthesia in children. Fifty-one patients aged 3 to 10 years, ASA physical status 1 or 2 were randomized to 4 groups: a spontaneous recovery group; or, reversal with pyridostigmine 0.25 mg/kg with glycopyrrolate 0.01 mg/kg at one of three times: 5 minutes after rocuronium administration; at 1% twitch height (T1) recovery; or at a 25% twitch height (T25) recovery. Anaesthesia was induced with thiopentone (5-7 mg/kg) and maintained with 2-3% sevoflurane and 50% nitrous oxide. Atropine (0.015 mg/kg) and, after calibrating the TOF-Watch, rocuronium (0.6 mg/kg) were then administered. Maximal block occurred 1.1+/-0.5 min (mean, SD) after rocuronium administration. In the spontaneous recovery group, the clinical duration (recovery to T25) was 40.1+/-8.8 min and the recovery index (time between T25 and T75) 19.9+/-9.8 min. Recovery to TOF >0.9 from the time of rocuronium administration was reduced by approximately 30% in the pyridostigmine groups compared to the spontaneous recovery group. There was no significant difference among the three pyridostigmine groups. When pyridostigmine was given at T1 or T25, the time from pyridostigmine administration to TOF >0.9 was shorter than for the group receiving pyridostigmine 5 minutes after rocuronium.     

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.