小儿体外循环时低温对阿曲库铵肌松作用的影响

研究小儿低温体外循环对阿曲库铵肌松作用的影响。选择在体外循环下行心脏手术的小儿２０例。并据体外循环低温程度分为Ａ、Ｂ两组。麻醉诱导后，用ＪＳ－１型肌松监测仪监测神经肌肉阻滞程度。首量阿曲库铵０．５ｍｇ／ｋｇ静注后，行气管插管。每当Ｔ１恢复至基础值２５％时，给予静注阿曲库铵０．２ｍｇ／ｋｇ，观察记录体外循环前、中、后期维持量阿曲库铵起效时间、作用时间及恢复时间（Ｔ５￣２５）的变化。结果：低温体外循环     

阿曲库铵气管插肌松条件的研究

研究了肌松监测下阿曲库铵气管插管的肌松条件。３２例患者随机分为三组。麻醉诱导：硫喷妥纳５～７ｍｇ／ｋｇ、阿曲库铵０．６ｍｇ／ｋｇ。根据肌松监测分别当Ｔ１＝２５％（组Ａ）、Ｔ１＝１０％（组Ｂ）、Ｔ１＝２％（组Ｃ）时气管插管。结果发现阿曲库铵首量后５．４分钟，Ｔ１＝２％时气管插管最为满意，随Ｔ１值的增加或给药后的时间缩短，插管的满意程度降低，尽管Ｔ１＝２５％时也可顺利气管插管，但插管的满意程度明显比Ｔ     

阿曲库铵气管插管肌松条件的研究

研究了肌松监测下河曲库铵气管插管的肌松条件。３２例患者随机分为三组。麻醉诱导：硫喷妥钠５～７ｍｇ／ｋｇ、阿曲库铵０．６ｍｇ／ｋｇ。根据肌松监测分别当Ｔ１＝２５％（组Ａ）、Ｔ１＝１０％（组Ｂ）、Ｔ１＝２％（组Ｃ）时气管插管。结果发现阿曲库铵首量后５．４分钟，Ｔ１＝２％时气管插管最为满意，随Ｔ１值的增加或给药后的时间缩短，插管的满意程度降低，尽管Ｔ１＝２５％时也可顺利气管插管，但插管的满意程度明显比Ｔ１＝２％时为差。三组气管插管后ＨＲ、ＭＡＰ均增加，但以组Ａ和组Ｂ增加明显，三组ＨＲ的增加幅度随Ｔ１值的增加而明显增加。     

阿曲库铵前处理对琥珀胆碱胆松作用起效时间影响的临床研究

研究阿曲库铵作前处理对琥珀胆碱肌松作用的起效和持续时间的影响。２０例患者分为对照组和前处理组。前处理组在注诱前５分钟预注阿曲库铵０．０６ｍｇ／ｋｇ，观察Ｔｈ降至Ｔ２５．Ｔ１０和％０的时间，Ｔ０的持续时间和Ｔｈ恢复至Ｔ１０、Ｔ２５、Ｔ７５的时间。结果表明，用阿曲库铵作前处理，既可缩短琥珀胆碱的起效时间，又不明显影响肌松持续时间，也能有效地防止琥珀胆碱肌震颤对患者可能造成的多种危害。     

安氟醚及异氟醚对阿曲库铵临床药效的影响

目的：观察吸入１％安氟醚或等效浓度异氟醚对阿曲库铵临床药效的影响。方法：３０例择期手术病人随机分为三组，分别吸入６７％Ｎ２Ｏ（Ⅰ组），１％安氟醚（Ⅱ组）或０．６７％异氟醚（Ⅲ组）后观察阿曲库铵临床药效。结果：静注阿曲库铵０．５ｍｇ／ｋｇ后，Ⅰ、Ⅱ和Ⅲ组的起效时间分别是２．２±０．４２分、２．１±０．４２分和２．１±０．３４分（Ｐ＞０．０５），作用时间分别是４５．８５±３．７分、５５．２５±６．４７分和５５．８８±８．２５分（Ｐ＜０．０１）；维持９０％～９５％颤搐抑制所需阿曲库铵的静脉滴注速度分别为６．２７７±１．０９２μｇ·ｋｇ－１·ｍｉｎ－１、４．２７２±０．５８５μｇ·ｋｇ－１·ｍｉｎ－１和４．５０５±０．７１６μｇ·ｋｇ－１·ｍｉｎ－１（Ｐ＜０．０１）。结论：１％安氟醚及等效浓度的异氟醚均可增强阿曲库铵的临床药效，但两者之间的增强无显著差异。     

阿曲库铵前处理对琥珀胆碱肌松作用起效时间影响的临床研究

研究阿曲库铵作前处理对琥珀胆碱肌松作用的起效和持续时间的影响。２０例患者分为对照组和前处理组。前处理组在静注诱导药前５分钟预注阿曲库铵０．０６ｍｇ／ｋｇ，观察Ｔｈ降至Ｔ２５、Ｔ１０和Ｔ０的时间，Ｔ０的持续时间和Ｔｈ恢复至Ｔ１０、Ｔ２５、Ｔ７５的时间。结果表明，用阿曲库铵作前处理，既可缩短琥珀胆碱的起效时间，又不明显影响其肌松持续时间，也能有效地防止琥珀胆碱肌震颤对患者可能造成的多种危害。     

哌库溴铵前处理对琥珀胆碱的肌震颤及肌松效应的影响

目的：观察哌库溴铵前处理对琥珀胆碱肌震颤的预防作用及对其肌松效应的影响。方法：３６例择期手术病人随机分成三组，Ⅰ组静注琥珀胆碱１ｍｇ／ｋｇ（对照组）。Ⅱ、Ⅲ组静注哌库溴铵１５μｇ／ｋｇ后３．５分钟分别注入琥珀胆碱１ｍｇ／ｋｇ和１．５ｍｇ／ｋｇ。结果：哌库溴铵前处理能有效地消除琥珀胆碱引起的肌震颤，但使１ｍｇ／ｋｇ琥珀胆碱的起效时间延长、阻滞程度降低、气管插管条件变差、肌松恢复时间缩短。当琥珀胆碱的剂量增至１．５ｍｇ／ｋｇ时，肌松效应恢复满意。结论：哌库溴铵前处理使琥珀胆碱的肌松效应减弱，故琥珀胆碱的插管剂量应增至１．５ｍｇ／ｋｇ，以获得满意的肌松。     

维库溴铵对琥珀胆碱肌松效应的影响

研究维库溴铵（Ｖ）作用的不同的不同消退期给予琥珀胆碱的肌松效应。方法：５５例全麻择期手术病人，按维库溴铵作用的不同消退期（５０％或７５％）和琥珀胆碱的剂量（１．０ｍｇ／ｋｇ或１．５ｍｇ／ｋｇ），随机分为六组。１－４组在维库溴铵作用消退５０％或７５％时，分别给予胆碱１．０ｍｇ／ｋｇ和１．５ｍｇ／ｋｇ；５、６组分别阳琥胆三１．ｍｇ／ｋｇ和１．５ｍｇ／ｋｇ作为对照。结果１－４组的琥珀胆碱使用时间比对照组     

罗库溴铵合用阿曲库铵时肌松效应及不良反应

合理伍用非去极化肌松药,以谋求最佳肌松效应、插管条件及最小副作用,已成为研究的热点。罗库溴铵起效快,有利于快速诱导插管,但它效价低且插管时存在膈源性咳嗽［１］;阿曲库铵效价高且能产生优良插管条件,但起效慢,组胺释放作用强。本研究旨在观察罗库溴铵和阿曲库铵合用时肌松效应、插管条件、循环功能改变及组胺释放反应,探讨临床应用价值。资料与方法４５例病人年龄２４～５８岁,ＡＳＡⅠ～Ⅱ级,行择期腹部手术,男２９例,女１６例,无影响神经肌肉传导功能因素。术前３０分钟阿托品０．５ｍｇ、苯巴比妥０．１ｇ肌注。患者…     

阿曲可林和维库溴铵间歇静注法和持续静滴法的比较研究

本文在８０例颅脑胸腹部等手术病人，通过ＴＯＦ监测神经肌接头功能，观察阿曲可林和维库溴铵间歇静注和持续静滴两种给药方法的肌松程度、用药量和恢复时间。结果：（１）间歇静注需频繁给药，肌松程度波动较大，持续静滴法肌松程度恒定。（２）维持肌颤搐２５％以下的静注法与维持肌颤搐５－１０％的静滴法的用药量几乎相等，阿曲可林为６．０５～６．７１μｇ／ｋｇ／ｍｉｎ，维库溴铵为１．１１～１．１２μｇ／ｋｇ／ｍｉｎ。（     

Cisatracurium am M. orbicularis oculi Vergleich der neuromuskulären Wirkung von Cisatracurium und Atracurium am M. orbicularis oculi und M. adductor pollicis

OBJECTIVES: Muscle relaxants have different pharmacodynamic profiles in various muscles. Therefore, results obtained for one muscle cannot be extrapolated to other muscles. In the adductor pollicis muscle cisatracurium exerts a pharmacodynamic profile comparable to atracurium, despite the known difference in onset time. However, studies evaluating the neuromuscular effect of cisatracurium in different muscles are lacking. Accordingly, this study compares the pharmacodynamic profile of cisatracurium and atracurium in the orbicularis oculi muscle (OO) - which shows a neuromuscular course similar to the diaphragm and the laryngeal muscles - and the adductor pollicis muscle (AP). METHODS: Forty-five patients (ASA I-II), scheduled for elective spinal surgery were anaesthetized with propofol and fentanyl. Endotracheal intubation was performed without using a muscle relaxant. Neuromuscular transmission was monitored using acceleromyography in both muscles. Patients received 0.1 mg/kg (2x ED(95)) or 0.15 mg/kg (3x ED(95)) cisatracurium, or 0.5 mg/kg atracurium (2x ED(95)) at random. Onset and recovery times were measured according to the recommendation of the Copenhagen Consensus Conference. RESULTS: Onset time was significantly shorter in the OO than in the AP following 0.15 mg/kg cisatracurium and 0.5 mg/kg atracurium (P<0.05). No differences in onset time between the two muscles were found after 0.1 mg/kg cisatracurium. The recovery of T(1) to 10% of its control was completed sooner in the OO than in the AP in all three groups (P<0.05). CONCLUSIONS: Cisatracurium shows a dose-dependent shorter onset time in the OO than in the AP. This is consistent with the current view that the onset of non-depolarizing neuromuscular blockers is more rapid in the OO than in the AP. However, at least a dose of 3x ED(95) of cisatracurium was necessary to show a difference in onset time between both muscles. In contrast, atracurium is reported to lead to a significantly shorter onset of neuromuscular block in the OO following 2x the ED(95). The more rapid recovery of T(1) to 10% of its control in all three groups in the OO is due to the relative resistance of this muscle to muscle relaxants.     

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.     

Effect of different doses of cisatracurium on intraocular pressure in sedated patients

BACKGROUND AND OBJECTIVE: The aim was to examine the course of intraocular pressure after relaxation with different doses of cisatracurium. METHODS: The investigation was carried out as a prospective, randomized double-blind study in a crossover design in 30 postoperative patients with stable haemodynamic and respiratory function (ASA I and II). To exclude any disrupting factors, patients remained intubated and continuously sedated. Twenty patients received an intubation dose (2 x ED95) of cisatracurium (0.1 mg kg(-1)) compared with atracurium (0.5 mg kg(-1)). In a second series, 10 patients were given an effective dose, ED95 (0.05 mg kg(-1)), and a repeat dose (0.02 mg kg(-1)) of cisatracurium. The intraocular pressure was determined before (T0) as well as 1 (T1), 5 (T5), 10 (T10), 15 (T15), 20 (T20) and 45 (T45) min after bolus administration. RESULTS: Intraocular pressure decreased after an intubation dose of either cisatracurium or atracurium, and reached a minimum after 10 min (6.7 +/- 2.2 and 7.9 +/- 2.1 mmHg, respectively). There was no significant difference between either muscle relaxant (P = 0.27). When lower doses of cisatracurium (0.05 and 0.02 mg kg(-1)) were applied, the intraocular pressure also decreased, albeit to a lesser extent and with a delayed onset (8.4 +/- 1.9 mmHg after 10 min, 9.9 +/- 3.4 mmHg after 15 min). There was no significant difference between dosages (p = 0.44). CONCLUSIONS: Cisatracurium is a useful drug in patients when a decrease of intraocular pressure is wanted and where muscle relaxation is necessary and acceptable.     

Pharmacokinetics of Cisatracurium in Patients Receiving Nitrous Oxide/Opioid/Barbiturate Anesthesia

Background: Cisatracurium, one of the ten isomers in atracurium, is a nondepolarizing muscle relaxant with an intermediate duration of action. It is more potent and less likely to release histamine than atracurium. As one of the isomers composing atracurium, it presumably undergoes Hofmann elimination. This study was conducted to describe the pharmacokinetics of cisatracurium and its metabolites and to determine the dose proportionality of cisatracurium after administration of 2 or 4 times the ED95.

Methods: Twenty ASA physical status 1 or 2 patients undergoing elective surgery under nitrous oxide/opioid/barbiturate anesthesia were studied. Patients received a single rapid intravenous bolus dose of 0.1 or 0.2 mg *symbol* kg sup -1 (2 or 4 times the ED95, respectively) cisatracurium. All patients were allowed to recover spontaneously to a train-of-four ratio greater or equal to 0.70 after cisatracurium-induced neuromuscular block. Plasma was extracted, acidified, and stored frozen before analysis for cisatracurium, laudanosine, the monoquaternary acid, and the monoquaternary alcohol metabolite.

Results: The clearances (5.28+/-1.23 vs. 4.66+/- 0.67 ml *symbol* min sup -1 *symbol* kg sup -1) and terminal elimination half-lives (22.4+/-2.7 vs. 25.5+/-4.1 min) were not statistically different between patients receiving 0.1 mg *symbol* kg sup -1 and 0.2 mg *symbol* kg sup -1, respectively. Maximum concentration values for laudanosine averaged 38+/-21 and 103+/-34 ng *symbol* ml sup -1 for patients receiving the 0.1 and 0.2 mg *symbol* kg sup -1 doses, respectively. Maximum concentration values for monoquaternary alcohol averaged 101+/-27 and 253+/-51 ng *symbol* ml sup -1, respectively. Monoquaternary acid was not quantified in any plasma sample.     

Atracurium and vecuronium: repeated bolus injection versus infusion.

The purpose of this study was to compare the characteristics of recovery from neuromuscular blockade after either atracurium or vecuronium given by intravenous infusion or by repeated injection. Four groups of 10 patients each were studied during nitrous oxide narcotic anesthesia. An initial intravenous dose of 2 x ED95 of either muscle relaxant was followed by an intravenous infusion started at 5% recovery of control twitch tension and adjusted for 95% block or by repeated injection of 0.6 x ED95 administered whenever twitch tension had returned to 25% of control. There were no significant differences between the maintenance doses required based on method of administration: atracurium repeated injection, 1.6 +/- 0.3 x ED95 h-1; atracurium infusion, 1.7 +/- 0.3 x ED95 h-1; vecuronium repeated injection, 1.8 +/- 0.5 x ED95 h-1; and vecuronium infusion, 1.6 +/- 0.4 x ED95 h-1. Nevertheless, differences of up to 20 min were noted in the recovery indices in the following order: atracurium repeated injection = atracurium infusion less than vecuronium repeated injection less than vecuronium infusion. A single dose of neostigmine (7 micrograms/kg) significantly reduced the recovery indices, thereby eliminating their differences.     

Precurarization of succinylcholine with cisatracurium: the influence of the precurarization interval

PURPOSE: To determine the influence of two different pretreatment intervals, i.e. 3 and 6 min, on the efficacy of 0.01 mg/kg cisatracurium in preventing succinylcholine-induced fasciculations and myalgia. METHODS: A total of 60 adult patients were randomized and received either 0.01 mg/kg cisatracurium (0.2*ED(95)) i.v. (Cis 3 group: pretreatment interval 3 min, Cis 6 group: pretreatment interval 6 min) or normal saline i.v. (placebo group) prior to injection of succinylcholine. The incidence and severity of fasciculations and myalgia and side-effects of precurarization were assessed. RESULTS: The incidence of muscle fasciculations was only reduced in the Cis 6 group (45%) compared with the Placebo group (85%), p<0.05. Cisatracurium was associated with a higher incidence of paralytic symptoms in both pretreatment groups (Cis 3: 75%, Cis 6: 80%) compared with the Placebo group (30%), p<0.05. CONCLUSION: Cisatracurium is only effective in preventing succinylcholine-induced fasciculations when a longer pretreatment interval, i.e. 6 min instead of 3 min, is chosen. Precurarization led to signs of paralysis in both pretreatment groups in the majority (75-80%) of patients without reducing the incidence or severity of postoperative myalgia.     

Dose-response relationships for edrophonium and neostigmine as antagonists of moderate and profound atracurium blockade

To measure the ability of neostigmine and edrophonium to reverse moderate and profound atracurium blockade, dose-response relationships were established for these reversal agents given at 1% and 10% twitch height recovery. Eighty-five ASA I and II adult patients received atracurium, 0.4 mg/kg, during a thiopental-nitrous oxide-enflurane anesthetic. Train-of-four stimulation was applied every 12 seconds, and the force of contraction of the adductor pollicis muscle was recorded. Edrophonium, 0.1, 0.2, 0.4, or 1 mg/kg; neostigmine, 0.005, 0.01, 0.02 or 0.05 mg/kg; or no reversal agent was given when there was either 1% or 10% recovery of the first twitch response. With profound blockade, the slope of the edrophonium dose-response relationship was significantly flatter (P less than 0.05) than that of neostigmine. The dose of neostigmine required to achieve 80% first twitch recovery (ED80) after 10 minutes was 0.013 +/- 0.003 mg/kg (mean +/- SEM) if given at 10% recovery, and 0.032 +/- 0.004 mg/kg if given at 1% recovery. The ED80 for edrophonium was 0.22 +/- 0.04 mg/kg and 1.14 +/- 0.33 mg/kg, respectively. These values corresponded to neostigmine:edrophonium potency ratios of 16.6 +/- 3.5 and 35.3 +/- 8.9 at 90% and 99% blockade respectively (P less than 0.006). We conclude that the relative potency of neostigmine is greater than that of edrophonium for antagonism of profound atracurium blockade.     

Mivacurium chloride (BW B1090U)-induced neuromuscular blockade during nitrous oxide-isoflurane and nitrous oxide-narcotic anesthesia in adult surgical patients

The neuromuscular and cardiovascular effects of mivacurium were studied in 90 adult patients during nitrous oxide-oxygen-isoflurane (n = 45, ISO group) and nitrous oxide-oxygen-narcotic (n = 45, BAL group) anesthesia. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate dose-response relations, three subgroups of nine patients in the ISO group received mivacurium doses of 0.025, 0.03, and 0.04 mg/kg, respectively. Similarly, three subgroups of nine patients in the BAL group received mivacurium doses of 0.03, 0.04, and 0.05 mg/kg, respectively. The ED50 and ED95 of mivacurium in each group were estimated from linear regression plots of log dose vs probit of maximum percentage depression of neuromuscular function. The estimated ED50 values for the ISO and BAL groups were 0.029 and 0.041 mg/kg, respectively. The estimated ED95 values for the ISO and BAL groups were 0.045 and 0.058 mg/kg, respectively. Recovery indexes were measured in 26 patients who received ED95 or greater doses of mivacurium in either the ISO or BAL groups. The recovery index was shorter in the BAL group (5.5 +/- 1.6 minutes [n = 10]), than in the ISO group (7.4 +/- 3.0 minutes [n = 16]). The addition of isoflurane (0.5-0.75% end-tidal concentration) to nitrous oxide-narcotic anesthesia augments the degree of neuromuscular blockade from a given dose of mivacurium and also prolongs the recovery index.     

Effect of isoflurane and sevoflurane on the magnitude and time course of neuromuscular block produced by vecuronium, pancuronium and atracurium

We have compared the ability of equipotent concentrations of isoflurane and sevoflurane to enhance the effect of non-depolarizing neuromuscular blocking drugs. Ninety ASA I and II patients of both sexes, aged 18-50 yr, were stratified into three blocker groups (Vec, Pan and Atr), to undergo neuromuscular block with vecuronium (n = 30), pancuronium (n = 30) or atracurium (n = 30), respectively. Within each group, patients were allocated randomly to one of three anaesthetic subgroups to undergo maintenance of anaesthesia with: (1) alfentanil-nitrous oxide- oxygen (n = 10); (2) alfentanil-nitrous oxide-oxygen-isoflurane (n = 10); or (3) alfentanil-nitrous oxide-oxygen-sevoflurane (n = 10) anaesthesia. During maintenance of anaesthesia, end-tidal concentrations of isoflurane, sevoflurane and nitrous oxide were 0.95, 1.70 and 70%, respectively. Both the evoked integrated electromyogram and mechanomyogram of the adductor pollicis brevis muscle were measured simultaneously. In the Vec and Pan groups, a total dose of 40 micrograms kg-1 of vecuronium or pancuronium, respectively, was given, and in the Atr group a total dose of atracurium 100 micrograms kg-1. Each blocker was given in four equal doses and administered cumulatively. We showed that 0.95% isoflurane and 1.70% sevoflurane (corresponding to 0.8 MAC of each inhalation anaesthetic, omitting the MAC contribution of nitrous oxide) augmented and prolonged the neuromuscular block produced by vecuronium, pancuronium and atracurium to a similar degree.      

Influences of age and gender on dose response and time course of effect of atracurium in anesthetized adult patients.

STUDY OBJECTIVE: To determine the influences of age and gender on the dose response and the time course of effect of atracurium. DESIGN: Prospective, nonrandomized, clinical comparison. SETTING: Operating room, Plastic Surgery Hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. PATIENTS: 72 adult ASA physical status I patients (38 male and 34 female), aged 15 to 59 years, scheduled for elective plastic surgery. INTERVENTIONS: Patients were divided into the three groups on the basis of age: Group 1, patients aged 15-29 years (n = 32); Group 2, patients aged 30-40 years (n = 21); and Group 3, patients aged 41-59 years (n = 19). Anesthesia was maintained with 60% nitrous oxide in oxygen, thiopental, and incremental doses of fentanyl as required. The dose-response relationship of atracurium was determined by a cumulative dose-response technique. MEASUREMENTS AND MAIN RESULTS: Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12 seconds and the percentage depression of first twitch (T1) response was used as the study variable. Age and gender significantly affected the dose-response relationship and time course of recovery of atracurium. Advancing age was associated with a reduced effective doses (ED50, ED90, and ED95) of atracurium and a longer duration of action. The effective doses of atracurium were greater, and its duration of action was shorter in men than in women. There were significant differences in the 50%, 90%, and 95% effective dose (ED50, ED90, and ED95) of atracurium, and clinical duration and total duration following administration of atracurium 400 micrograms/kg among the three age groups, and between men and women. CONCLUSIONS: Age and gender have significant effects on the dose response and time course of effect of atracurium. Older patients and women are more sensitive to atracurium-induced neuromuscular block than are young patients and men.