The effects of cisatracurium on morbidly obese women

There is conflicting evidence on the duration of action of atracurium in obese patients. Cisatracurium is one of the stereoisomers of atracurium. We investigated the neuromuscular effects of cisatracurium in morbidly obese patients. Twenty obese female patients (body mass index >40) were randomized in two groups. Group I (n = 10) received 0.2 mg/kg of cisatracurium on the basis of real body weight (RBW), whereas in Group II (n = 10) the dose was calculated on ideal body weight (IBW). In a control group of 10 normal weight female patients (body mass index 20-24), the dose of cisatracurium was based on RBW. Neuromuscular transmission was monitored using acceleromyography of the adductor pollicis, and anesthesia was induced and maintained with remifentanil and propofol. Onset time was comparable between Group I and the control group (132 s versus 135 s; P = ns). The duration 25% was longer in Group I than in the control group (74.6 min versus 59.1 min; P = 0.01) and in the control group compared with Group II (45.0 min; P = 0.016). In conclusion, the duration of action of cisatracurium was prolonged in morbidly obese patients when dosed according to RBW compared with a control group of normal weight patients. Duration was also prolonged in the control group patients compared with morbidly obese patients to whom the drug was administered on the basis of IBW.     

Pharmacokinetics of rocuronium bromide in obese female patients.

Following administration of 0.6 mg kg-1 rocuronium, the pharmacokinetics and the pharmacodynamics were studied in six obese and six control (normal weight) patients receiving balanced anaesthesia. Twelve gynaecological patients were allocated into two groups, according to body mass index (normal weight: body mass index: 20-24, obese weight: body mass index > 28). Venous plasma concentrations were determined by high-pressure liquid chromatography before administration of rocuronium, at 1, 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, 48, 60, 75, 120, 180, 240, 300, 360 and 420 min after administration of rocuronium and at recovery of single twitch to 25% and 75% of control twitch height. Onset time was shorter (NS) in the obese compared with normal weight (obese weight: 65 +/- 16, normal weight: 100 +/- 39 s, mean +/- SD). Duration 25% (obese weight: 29.5 +/- 5.3, normal weight: 28.4 +/- 5.3 min) and spontaneous recovery time (obese weight: 12.6 +/- 2.7, normal weight: 12.5 +/- 2.3 min) did not show any differences between the two groups. The pharmacokinetics of rocuronium were comparable in the two groups. The volume of distribution at steady state Vss (mL kg-1) was 208 +/- 56 in normal weight and 169 +/- 37 in obese weight. Distribution (T1/2 alpha) and elimination half-life (T1/2 beta) as well as mean residence time were 15.6 +/- 3.7, 70.3 +/- 23.9 and 53.2 +/- 9.8 min in normal weight and 16.9 +/- 3.8, 75.5 +/- 25.5 and 51.1 +/- 18.9 min in obese weight, respectively. Also, no differences were observed in plasma clearance (3.89 +/- 0.58 in normal weight and 3.62 +/- 1.42 mL kg-1 min-1 obese weight). This study indicates that the pharmoacodynamics and pharmacokinetics of rocuronium are in female patients not altered by obesity.     

Total intravenous anesthesia with remifentanil, propofol and cisatracurium in end-stage renal failure

PURPOSE: To compare recovery parameters of total intravenous anesthesia (TIVA) with remifentanil and propofol, hemodynamic responses to perioperative events, and pharmacodynamic parameters of cisatracurium in 22 end-stage renal failure and 22 normal renal function patients. METHODS: Anesthesia was induced with 2-3 mg x kg(-1) propofol and 1 microg x kg(-1) remifentanil and maintained with 75 microg x kg(-1) x min(-1) propofol and propofol initial infusion of 0.2 microg x kg(-1) x min(-1) propofol. Arterial pressure and heart rate were maintained by remifentanil infusion rate adjustments. The first twitch (T1) was maintained at 25% by an infusion of cisatracurium. RESULTS: There was no difference in the time to maintenance of adequate respiration, date of birth recollection, first analgesic administration, between the renal failure (4.8+/-2.5, 7.8+/-3.2, 12.3+/-5.3 min respectively) and the control group (5.2+/-2.8, 8.1+/-3.1, 12.7+/-5.5 min): nor were there any differences in the time to 25% T1 recovery, T1 recovery from 25% to 75%, or cisatracurium infusion rate between the renal failure group (32.1 +/-10.8 min, 18.2+/-5.5 min, 0.89+/-0.29 microg x kg(-1) min(-1) respectively) and the control group (35.9 (7.9 min, 18.4+/-3.8 min, 0.95+/-0.22 microg x kg(-1) x min(-1)). CONCLUSION: End-stage renal failure does not prolong recovery from TIVA with remifentanil and propofol, or the recovery from cisatracurium neuromuscular block.     

Pharmacokinetics and pharmacodynamics of vecuronium in the obese surgical patient.

The effect of obesity on the disposition and action of vecuronium was studied in 14 surgical patients. After induction of anesthesia with thiopental and maintenance of anesthesia by inhalation of nitrous oxide and halothane, seven obese patients (93.4 +/- 13.9 kg, 166% +/- 30% of ideal body weight, mean +/- SD) and seven control patients (60.9 +/- 12.3 kg, 93% +/- 6% of ideal body weight) received 0.1 mg/kg of vecuronium. Plasma arterial concentrations of muscle relaxant were determined at 1, 3, 5, 10, 15, 20, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300, and 360 min by a spectrofluorometric method. Simultaneously, neuromuscular blockade was assessed by stimulation of the ulnar nerve and quantification of thumb adductor response. Times to 50% recovery of twitch were longer in the obese than in the control patients (75 +/- 8 versus 46 +/- 8 min) as were 5%-25% recovery times (14.9 +/- 4.0 versus 10.0 +/- 1.7 min) and 25%-75% recovery times (38.4 +/- 13.8 versus 16.7 +/- 10.3 min). However, vecuronium pharmacokinetics were similar for both groups. When the data were calculated on the basis of ideal body weight (IBW) for obese and control patients, total volume of distribution (791 +/- 303 versus 919 +/- 360 mL/kg IBW), plasma clearance (4.65 +/- 0.89 versus 5.02 +/- 1.13 mL.min-1.kg IBW-1), and elimination half-life (119 +/- 43 versus 133 +/- 57 min) were not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

不同体温对兔不同剂量顺式阿曲库铵肌松效应的影响

目的 评价不同体温对兔不同剂量顺式阿曲库铵肌松效应的影响.方法 健康成年新西兰大白兔72只,体重2.0～2.2 kg,雌雄各半,随机分为低体温组(L组)、常温组(N组)和高体温组(H组),每组24只,各组直肠温度依次为34.5、38.5和41.8℃,各组随机分为4个亚组,L<1～4组、N1～4组和H1～4组,每组6只.各亚组分别于直肠温度稳定20 min后静脉注射顺式阿曲库铵0.33、0.66、0.99和1.32 mg/kg,于改变动物体温前5 min、给药前2 min、给药后5、10、30、60、90 min时监测平均动脉压(MAP)、心率(HR)及直肠温度,记录肌松起效时间、从注药毕到T1恢复至基础值5%、25%和95%的时间及恢复指数.结果 不同体温下相同剂量组间比较:与N组比较,H组肌松起效时间、从注药毕到T1恢复至基础值5%、25%和95%的时间及恢复指数缩短,L组延长(P<0.05或0.01);相同体温下不同剂量组间比较:随顺式阿曲库铵剂量增加,各组肌松起效时间缩短、从注药毕到T1恢复至基础值5%、25%和95%的时间延长(P<0.01);剂量与体温因素的交互作用对起效时间的影响差异有统计学意义(P<0.01);相同剂量不同体温下MAP、HR比较:与N组比较,H组各时点MAP降低、HR升高,L组各时点MAP、HR升高(P<0.05或0.01).结论 体温升高时顺式阿曲库铵的肌松效应降低,体温降低时顺式阿曲库铵的肌松效应升高;相同体温下顺式阿曲库铵(0.33～1.32 mg/kg)的肌松效应呈剂量依赖性;两因素间存在交互作用.     

Clinical effect of mivacurium in morbidly obese patients

OBJECTIVES: To compare the clinical effect of mivacurium in morbidly obese and normal-weight patients. PATIENTS AND METHODS: Ten morbidly obese patients (body mass index >40) and 10 normal-weight patients (body mass index, 21-24) with normal plasma cholinesterase levels. Anesthesia was provided with propofol and remifentanil in continuous infusion and a mixture of oxygen and nitrous oxide. Mivacurium was administered at a dose based on the patient's weight (0.15 mg x kg(-1)). The neuromuscular block was monitored by train-of-four (TOF) acceleromyography after stimulation of the cubital nerve at the forearm. We measured the onset time (time from administration of the muscle relaxant to 95% twitch depression), duration of block (times from dosing to 5% recovery after the first twitch [T1] of a TOF stimulus and to a TOF ratio of 80%), and the recovery indices (time between 25% and 75% recovery after T1 and between recovery of TOF ratios of 25% and 80%). Groups were compared with the Student t test. RESULTS: Mean (SD) onset time was similar in the 2 groups (normal weight 2.73 [1] minutes vs morbidly obese 1.91 [0.6] minutes). Other measures of duration and recovery were also similar in the 2 groups, respectively: duration of dose-T1 5%, 12.23 (2.1) vs 11.45 (3) minutes; dose-TOF ratio 80%, 24.71 (4.6) vs 24.81 (5) minutes); recovery index T1 25%-75%, 6.45 (2) vs 5.56 (1) minutes; recovery of TOF ratio T1 25%-80%, 9 (2) vs 10.11 (2) minutes. CONCLUSION: We found no differences in the clinical effect of mivacurium between morbidly obese and normal-weight patients when doses were based on real weight.     

Recovery of neuromuscular block after continuous infusion of cisatracurium in patients with renal dysfunction]

OBJECTIVE: Study of the recovery of neuromuscular block after continuous infusion of cisatracurium in patients with renal dysfunction. STUDY DESIGN: Prospective case-control study. PATIENTS: Forty adult patients scheduled for urological surgery were assigned to two groups according to the creatinine clearance (CC) as a measure of the renal function: group IR (CC < 60 mL.min-1) or group NR (CC > or = 60 mL.min-1). METHODS: After premedication with hydroxyzine, anaesthesia was induced with propofol, sufentanil and cisatracurium (0.15 mg.kg-1), and maintained using isoflurane, sufentanil and a continuous infusion of cisatracurium (0.12 mg.kg-1.h-1) adjusted for maintained a post-tetanic count < or = 5. Neuromuscular transmission was monitored at the adductor pollicis using accelerography (TOF Gard). Onset and recovery times in both groups were compared using Student's t test. RESULTS: Infusion time and total dose of cisatracurium were comparable in both groups. Onset times were 3.9 +/- 0.8 min and 3.5 +/- 0.6 min in groups IR and NR respectively. After the infusion, the time to train-of-four ratio of 0.8 were not different in both groups: 77 +/- 18 min (group IR) and 73 +/- 13 min (group NR). However, the spontaneous recovery intervals 25%-75% were delayed in group IR (20 +/- 9 min vs 14 +/- 5 min p < 0.05). CONCLUSION: There are minor differences in the pharmacodynamics of cisatracurium between patients with normal or impaired renal function. Nevertheless, a marked interindividual variability in the recovery parameters was observed in patients with renal dysfunction.     

Prevention of atelectasis formation during the induction of general anesthesia in morbidly obese patients

Atelectasis caused by general anesthesia is increased in morbidly obese patients. We have shown that application of positive end-expiratory pressure (PEEP) during the induction of anesthesia prevents atelectasis formation in nonobese patients. We therefore studied the efficacy of PEEP in morbidly obese patients to prevent atelectasis. Twenty-three adult morbidly obese patients (body mass index >35 kg/m(2)) were randomly assigned to one of two groups. In the PEEP group, patients breathed 100% oxygen (5 min) with a continuous positive airway pressure of 10 cm H(2)O and, after the induction, mechanical ventilation via a face mask with a PEEP of 10 cm H(2)O. In the control group, the same induction was applied but without continuous positive airway pressure or PEEP. Atelectasis, determined by computed tomography, and blood gas analysis were measured twice: before the induction and directly after intubation. After endotracheal intubation, patients of the control group showed an increase in the amount of atelectasis, which was much larger than in the PEEP group (10.4% +/- 4.8% in control group versus 1.7% +/- 1.3% in PEEP group; P < 0.001). After intubation with a fraction of inspired oxygen of 1.0, PaO(2) was significantly higher in the PEEP group compared with the control group (457 +/- 130 mm Hg versus 315 +/- 100 mm Hg, respectively; P = 0.035) We conclude that in morbidly obese patients, atelectasis formation is largely prevented by PEEP applied during the anesthetic induction and is associated with a better oxygenation. IMPLICATIONS: Application of positive end-expiratory pressure during induction of general anesthesia in morbidly obese patients prevents atelectasis formation and improves oxygenation. Therefore, this technique should be considered for anesthesia induction in morbidly obese patients.     

Ideal versus corrected body weight for dosage of sugammadex in morbidly obese patients

To date, the dosing of sugammadex is based on real body weight without taking fat content into account. We compared the reversal of profound rocuronium-induced neuromuscular blockade in morbidly obese patients using doses of sugammadex based on four different weight corrections. One hundred morbidly obese patients, scheduled for laparoscopic bariatric surgery under propofol-sufentanil anaesthesia, were randomly assigned four groups: ideal body weight; ideal body weight + 20%; ideal body weight + 40%; and real body weight. Patients received sugammadex 2 mg.kg(-1), when adductor pollicis monitoring showed two responses. The primary endpoint was full decurarisation. Secondary endpoints were the ability to get into bed independently on arrival to the post-anaesthetic care unit and clinical signs of residual paralysis. There was no residual paralysis in any patient. Morbidly obese patients can safely be decurarised from rocuronium-induced neuromuscular blockade T1-T2 with sugammadex dosed at 2 mg.kg(-1) ideal body weight + 40% (p < 0.0001).     

Comparison of cisatracurium-induced neuromuscular block at the masseter and adductor pollicis muscle

Adequate relaxation of the masseter muscle is important during endotracheal intubation and for the patency of a patient's airway during recovery from anaesthesia. We evaluated onset and recovery from cisatracurium-induced neuromuscular block at the masseter and adductor pollicis muscles. Thirty patients were randomly allocated to receive either 0.1 or 0.15 mg kg(-1) cisatracurium. The evoked response was measured at both muscles using acceleromyography. Onset time was significantly shorter at the masseter muscle than at the adductor pollicis (0.1 mg kg(-1) cisatracurium: 155+/-52 vs. 229+/-44 s; 0.15 mg kg(-1) cisatracurium: 105+/-24 vs. 174+/-35 s). Following 0.1 mg kg(-1) cisatracurium, recovery to a TOF-ratio of 0.7 was faster at the masseter compared to the adductor pollicis (P < 0.05). In the 0.15 mg kg(-1) cisatracurium group recovery of T1 to 75% of control and to a TOF-ratio of 0.7 occurred sooner at the masseter (P < 0.05). We conclude that onset and recovery from cisatracurium neuromuscular block occurs more rapidly at the masseter than at the adductor pollicis. It appears unlikely that residual paralysis is present at the masseter once neuromuscular function at the adductor pollicis has completely recovered.     

The effect of anesthetic technique on recovery from neuromuscular blockade with cisatracurium

OBJECTIVES: To assess the effect of four anesthetic techniques on recovery after a single dose of 0.2 mg/kg of cisatracurium. PATIENTS AND METHOD: After giving informed consent, 96 patients of both sexes, ASA I-III, were enrolled. Anesthesia was induced with fentanyl, propofol O2-N2O (FiO2 40%) after which the patients were randomly assigned to four groups according to maintenance technique: propofol by infusion, sevoflurane, desflurane or isoflurane at 1.3 MAC. Neuromuscular block was monitored (electromyographic recording of the pollicis adductor). Variables recorded were time of maximum block, duration of action of 1% and 25%, and recovery indices at T0-TR75 andT25%-T75%. ANOVA was performed ( = 0.05 and beta = 0.1). RESULTS: The groups were homogeneous. Time until recovery of 25% of baseline amplitude of the first response to a train of four (TOF) (T1) was longer in the desflurane group (68.4 +/- 11.1 min) than in the propofol group (60.2 +/- 9.4 min; p < 0.05). Time until recovery of 75% of the TOF-ratio was longer in the sevoflurane (96.8 +/- 13.1 min), desflurane (101.5 +/- 14.4 min) and isoflurane (94.1 +/- 13.9 min) groups than in the propofol group (83.7 +/- 1.3 min) (p < 0.0001).Times until recovery of T1 up to 1% were not statistically different: 45.8 +/- 10.7 (propofol), 50.6 +/- 11.0 (sevoflurane), 51.3 +/- 11.5 (desflurane) and 46.5 +/- 11.2 min (isoflurane). The 25% - 75% recovery index was also similar at 19.0 +/- 9.3 (propofol), 20.0 +/- 5.1 (sevoflurane), 25.7 +/- 12.4 (desflurane) and 20.9 +/- 7.9 (isoflurane). CONCLUSIONS: The inhaled anesthetics studied prolong the duration of clinical effect of cisatracurium more than does propofol.     

Effects of ephedrine on the onset time of neuromuscular block and intubating conditions after cisatracurium: preliminary results

We studied the effects of intravenous ephedrine on the onset time and the intubating conditions 2 min after a bolus dose of cisatracurium (0.15 mg kg-1). Thirty patients anaesthetized with sufentanil and propofol were randomly divided in 2 groups to receive either ephedrine (70 micrograms.kg-1) or saline, 5 s before propofol. Cisatracurium was administered after loss of consciousness. Neuromuscular block was assessed at the adductor pollicis using accelography. Tracheal intubation was performed 2 min after cisatracurium injection and rated as excellent, good, poor or bad. At intubation, neuromuscular block (% height of control T1) was greater in patients receiving ephedrine (36.1 +/- 25.8% vs 57.9 +/- 25.1%) (mean +/- SD). The frequency of excellent intubating conditions was higher after ephedrine (86.6%) than after saline (40.0%). The onset time of cisatracurium was shorter after ephedrine (167 +/- 64.8 s vs 234.9 +/- 63.1 s). Thus, a low dose of ephedrine given before induction of anaesthesia improves the intubating conditions 2 min after 0.15 mg kg-1 cisatracurium and this effect likely relates to a quicker onset of neuromuscular block.     

Cisatracurium pharmacodynamics in patients with oculopharyngeal muscular dystrophy

The pharmacodynamics of muscle relaxants in patients with oculopharyngeal muscular dystrophy (OPMD) have never been studied. We designed this study to compare the pharmacodynamics of cisatracurium in OPMD patients versus a control group. Forty patients were enrolled: 20 OPMD patients requiring general anesthesia for cricopharyngeal myotomy and 20 age-matched controls undergoing an operation of similar duration and expected blood loss. Anesthesia was standardized, and both groups received a bolus of cisatracurium 0.1 mg/kg. Onset time, time to 10% T1 recovery, and the intervals 10%-25% and 25%-75% were calculated for both groups. A subgroup analysis was performed in patients with a more severe form of OPMD. Demographic and intraoperative data were similar. Onset time was significantly longer in OPMD patients compared with the control group (4.6 +/- 1.5 min versus 3.4 +/- 1.0 min; P = 0.001). There was no difference in recovery times or indices between groups, regardless of the severity of the disease. In conclusion, there was no difference in the duration of a cisatracurium-induced neuromuscular block between OPMD patients and a control group. A delayed onset of action of the drug may occur.     

Pharmacokinetics and pharmacodynamics of a 0.1 mg/kg dose of cisatracurium besylate in children during N2O/O2/propofol anesthesia

We studied the pharmacokinetics and pharmacodynamics of cisatracurium in 9 children (mean weight, 17.1 kg) aged 1-6 yr (mean, 3.75 yr) during propofol-nitrous oxide anesthesia. Neuromuscular monitoring was performed. Venous samples were taken before injection of a 0.1 mg/kg dose of cisatracurium and then at 2, 5, 10, 30, 60, 90, and 120 min. Cisatracurium plasma concentrations were determined by high performance liquid chromatography. Onset time was 2.5 +/- 0.8 min, recovery to 25% of baseline twitch height was 37.6 +/- 10.2 min, and the 25%-75% recovery index was 10.9 +/- 3.7 min. Distribution and elimination half-lives were 3.5 +/- 0.9 min and 22.9 +/- 4.5 min, respectively. Steady-state volume of distribution (0.207 +/- 0.031 L/kg) and total body clearance (6.8 +/- 0.7 mL/min/kg) were significantly larger than those published for adults. Pharmacodynamic results were comparable to those obtained in pediatric studies during halothane or opioid anesthesia with the exception of a longer recovery to 25% baseline. Although the plasma-effect compartment equilibration rate constant was twofold faster (0.115 +/- 0.025 min(-1)) than that published for cisatracurium in adults, the effect compartment concentration corresponding to 50% block was similar (129 +/- 27 ng/mL).     

The pharmacodynamic effects of rocuronium when dosed according to real body weight or ideal body weight in morbidly obese patients

We investigated the pharmacodynamic effects of rocuronium on morbidly obese patients. Twelve morbidly obese female patients (body mass index >40 kg/m(2)) admitted for laparoscopic gastric banding were randomized into two groups. Group 1 (n = 6) received 0.6 mg/kg of rocuronium based on real body weight, whereas Group 2 (n = 6) received 0.6 mg/kg of rocuronium based on ideal body weight. In a control group of six normal-weight female patients admitted for laparoscopic surgery, rocuronium was dosed on the basis of their real body weight. Neuromuscular transmission was monitored by using acceleromyography of the adductor pollicis; anesthesia was induced and maintained with remifentanil and propofol. The onset time tended to be shorter in Group 1 and the control group compared with Group 2, but this did not achieve statistical significance. Duration of action to 25% of twitch tension was more than double in Group 1 (55 min) compared with the other two groups (22 and 25 min; P < 0.001). Duration of action was similar between Group 2 and control. Recovery index tended to be longer in Group 1, but without a significant difference. In conclusion, in morbidly obese patients, the duration of action of rocuronium is significantly prolonged when it is dosed according to real body weight. Therefore, the dosage should be assessed on the basis of ideal rather than on real body weight in clinical practice.     

Comparison of the neuromuscular blocking effect of cisatracurium and atracurium on the larynx and the adductor pollicis

BACKGROUND: Cisatracurium unlike atracurium is devoid of histamine-induced cardiovascular effects and this alone would be the greatest advantage in replacing atracurium for the facilitation of tracheal intubation. On the other hand, 2 ED(95) doses of cisatracurium (100 micro g/kg) do not yield satisfactory intubating conditions such as those seen with equipotent doses of atracurium and therefore the recommended intubating dose of cisatracurium is 3 ED(95). To understand this discrepancy better, we evaluated the potency and onset of atracurium and cisatracurium directly at the larynx adductors in humans. METHODS: The study was conducted in 54 patients (ASA class I or II) undergoing peripheral surgery requiring general anesthesia. Cisatracurium 25-150 micro g/kg or atracurium 120-500 micro g/kg intravenous (i.v.) boluses doses were administered during anesthesia with propofol, nitrous oxide, oxygen and fentanyl. Neuromuscular block was measured by electromyography (single twitch stimulation every 10 s) at the larynx and the adductor pollicis. The dose-response effect measured at both muscles included maximum neuromuscular blockade achieved (Emax), the time to maximum depression of twitch height (onset) and time to spontaneous recovery of the twitch height to 25%, 75% and 90% (T25, T75, T90) of control value. RESULT: The onset at the larynx was of 196 +/- 28 s after the 100 micro g/kg cisatracurium dose compared with 140 +/- 14 s after the 500 micro g/kg atracurium dose (P < 0.05). Emax at the larynx was 92 +/- 1% and 98 +/- 1% after 100 micro g/kg cisatracurium and 500 micro g/kg atracurium, respectively (P < 0.05). The time to onset of maximum suppression Emax = 100 +/- 0% after a 150 micro g/kg cisatracurium dose was 148 +/- 29 s. At the larynx, the ED(50) was 25 micro g/kg for cisatracurium and 180 micro g/kg for atracurium and the ED(95) was 87 micro g/kg for cisatracurium compared with 400 micro g/kg for atracurium. CONCLUSION: The slow onset time at the laryngeal muscles after cisatracurium can be explained by the higher potency as compared with atracurium.     

Pharmacodynamic interactions between cisatracurium and rocuronium

The onset and duration of maintenance doses of neuromuscular blocking drugs may be influenced by the original neuromuscular blocking drug used. We assessed the effect of the interaction between steroidal and benzo-isoquinolinium compounds on the clinical duration of maintenance doses of cisatracurium. Sixty adult patients undergoing anesthesia with isoflurane, nitrous oxide, and oxygen were randomized to receive the following: Group I = rocuronium 0.6 mg/kg followed by cisatracurium 0.03 mg/kg when the first twitch in the train-of-four (TOF) recovered to 25%, Group II = cisatracurium 0.15 mg/kg followed by cisatracurium 0.03 mg/kg, and Group III = rocuronium 0.6 mg/kg followed by rocuronium 0.15 mg/kg. Neuromuscular blockade was monitored using acceleromyography (TOF-Guard, Boxtel, The Netherlands). The clinical duration (mean +/- SD) of the first 2 maintenance doses was 41 +/- 10, 31 +/- 7++, and 25 +/- 8++ min, and 39 +/- 11, 30 +/- 6+, 29 +/- 9* min in Groups I-III, respectively (*P < 0.05, +P < 0.01, ++P < 0.001; Group I versus II and III). Thus, the clinical duration of the first two maintenance doses of cisatracurium was prolonged when administered after rocuronium. IMPLICATIONS: We assessed the clinical effect of administering cisatracurium after an intubating dose of rocuronium in 60 patients undergoing isoflurane/nitrous oxide and oxygen anesthesia. The clinical duration of the first two maintenance doses of cisatracurium administered after rocuronium was significantly prolonged. This supports the contention that combinations of structurally dissimilar neuromuscular blocking drugs result in a synergistic effect.     

Pharmacokinetics of sufentanil in obese patients.

The pharmacokinetics of sufentanil were determined in eight obese (94.1 +/- 14 kg, mean +/- SD) and eight control patients (70.1 +/- 13 kg) anesthetized for neurosurgery. After induction of anesthesia, 4 micrograms/kg of sufentanil was administered in a single intravenous bolus. Multiple arterial samples were obtained at timed intervals over 6 h, and plasma concentrations of sufentanil were measured by radioimmunoassay. Calculation of pharmacokinetic variables from the derived compartmental models demonstrated an increased volume of distribution of sufentanil in the obese (9098 +/- 2793 mL/kg ideal body weight, mean +/- SD) when compared with a control group (5073 +/- 1673 mL/kg ideal body weight) (P less than 0.01) and a prolonged elimination half-life (208 +/- 82 min vs 135 +/- 42 min, P less than 0.05). The total volume of distribution correlated linearly with the degree of obesity, as expressed in percent ideal body weight (r = 0.67). In contrast, plasma clearance was similar in both obese and control groups (32.9 +/- 12.5 vs 26.4 +/- 5.7 mL/kg ideal body weight). The high lipid solubility of sufentanil probably explains the altered pharmacokinetics of this opioid in obese patients.     

Onset of vecuronium neuromuscular block is more rapid in patients undergoing Caesarean section

This investigation was carried out in ten patients undergoing elective Caesarean section and the results were compared with those of a control group of ten nonpregnant females of the same age group. The study investigated the onset of vecuronium neuromuscular block and the conditions of tracheal intubation when ketamine (1.5 mg.kg-1)-vecuronium 100 micrograms.kg-1) sequence was used for rapid-sequence induction of anaesthesia. The ulnar nerve was stimulated supra-maximally at the wrist with train-of-four stimuli every 20 sec, and the electromyographic response of the adductor pollicis muscle was displayed. The onset of 50% neuromuscular block as monitored by electromyography was shorter in the Caesarean group (80 +/- 30 sec) than in the control group (144 +/- 43 sec). The conditions of intubation at 50% block were adequate in both groups. Also, the onset of 90% block was shorter in the Caesarean group. The time of recovery to T1/control ratio of 25% was longer in the Caesarean group (46 +/- 10 min) than in the control patients (28 +/- 10 min). The results show that administration of vecuronium according to body weight results in a more rapid onset and delayed recovery of neuromuscular block in pregnant women undergoing Caesarean section than in the nonpregnant control patients.