The influence of 0.5 % isoflurane on a vecuronium-induced neuromuscular blockade

The influence of adding 0.5% isoflurane to a narcotic-based anaesthesia on the duration of effect and recovery time after repetitive administration of vecuronium was studied in ten healthy patients. The twitch response in the adductor pollicis muscle was recorded after supramaximal train-of-four (TOF) stimulation of the ulnar nerve at the wrist. Prior to endotracheal intubation a bolus dose of vecuronium (0.08 mg/kg b.w.) was given. During surgery repeated injections of vecuronium (0.02 mg/kg b.w.) were administered at a TOF ratio of 0.25. Hand-skin temperature, systolic blood pressure, end-tidal CO2 and isoflurane concentrations were continuously monitored. Before and after 90 min administration of isoflurane, the duration of effect was 21 +/- 4 and 24 +/- 5 min (mean +/- s.d., P less than 0.05) respectively. Corresponding recovery times were 270 +/- 60 and 280 +/- 70 s (n.s.). Skin temperature remained unchanged and systolic blood pressure showed only minor variations. The addition of 0.5% isoflurane to a narcotic-based anaesthesia causes a moderate increase in duration of effect but no change in recovery time from a repetitive vecuronium-induced neuromuscular blockade of 0.02 mg/kg.     

Tetanus-induced changes in apparent recovery after bolus doses of atracurium or vecuronium.

The current study evaluated the duration and magnitude of post-tetanic effects in 56 patients recovering from a bolus dose of nondepolarizing relaxant to assess the impact of tetanus on monitoring in a common clinical setting. After induction of general anesthesia (thiopental, fentanyl, oxygen, nitrous oxide, and isoflurane), a baseline response to train-of-four (TOF) stimulation was recorded using an adductor pollicis force transducer, and the ratio of the fourth response (T4) to the first (T1) was calculated. Patients then received a bolus dose of either atracurium 0.50 mg.kg-1 (n = 28) or vecuronium 0.10 mg.kg-1 (n = 28). TOF was recorded at 12-s intervals between 25% and 75% recovery of T1 (time25-75%, first data set); then, block was reestablished with the same agent (atracurium 0.10 or vecuronium 0.02 mg.kg-1), and monitoring of time25-75% was repeated (second data set). Subjects were randomized such that none, one, or both sets had TOF monitoring interrupted by a 5-s, 50-Hz tetanic stimulus at 50% recovery (TET). For each drug, 7 patients were assigned to each of the four possible sequences: no tetanus (NOTET) set followed by NOTET set; NOTET-TET; TET-NOTET; and TET-TET. After either drug, the TET data sets demonstrated significant acceleration of recovery of T1 from 50% to 75% (time50-75%) of its baseline height (P less than 0.05 by paired t test). After atracurium, time50-75% was shortened by the tetanic stimulation from a control of 6.3 +/- 1.1 to 5.0 +/- 1.3 min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Train–of–four fade during onset of neuromuscular block with nondepolarising neuromuscular blocking agents

Fade in the train-of-four (TOF) responses during onset of neuromuscular block was studied following administration of atracurium (225 or 450 micrograms/kg), vecuronium (40 or 80 micrograms/kg), pancuronium (60 or 120 micrograms/kg) and tubocurarine (450 micrograms/kg). TOF ratios were measured at approximate heights of T1 (first response in the TOF) of 75, 50 and 25%. Fade in TOF increased as the height of T1 decreased, with maximum fade being observed at T1 of 25%. The greatest difference between relaxants was observed at T1 of 25%, vecuronium showing the least fade and pancuronium, atracurium and tubocurarine showing increasing fade, in that order. The difference between atracurium and tubocurarine or between vecuronium and pancuronium was not significant, but the degree of TOF fade was significantly greater with atracurium and tubocurarine in comparison to vecuronium or pancuronium.     

异氟醚对新斯的明拮抗维库溴铵肌松作用的影响

目的：研究一定浓度的异氟醚对新斯的明拮抗维库溴铵肌松作用的影响。方法：30例病人随机分为三组（各10例）：（1）丙泊酚静脉麻醉组,即对照组（P组）。（2）观察组。以异氟醚维持麻醉,再分为两组;术中呼气未异氟醚浓度均为1MAC,临近手术结束用新斯的明拮抗时,呼气末异氟醚浓度分别为1MAC（1M组（）和0．3MAC（0．3M组）,术中各组均连续输注维库溴铵,术毕以新斯的明0．035mg/kg拮抗并记录以下数据;维库溴铵输注速率,从拮抗开始到T1恢复到90％,TOF恢复到0．7和0．9的时间拮抗后15分钟时的T1,TOF比值,结果：1M组和0．3M组维库溴铵输注速率较P组降低IP＜0．05）,新斯的明拮抗后,0．3M组和1M组T1恢复到90％,TOF恢复到0．7和0．9的时间较P组延长（P＜0．05和P＜0．01）,1M组TOF恢复到0．9的时间较0＝3M组延长（P＜0．05）,在新斯的明拮抗后15分钟,0．3M组和1M组的T1和TOF比值均低于P组（P＜0．05）,1M组的TOF比值低于0．3M组（P＜0．05）,结论：呼气未浓度为1MAC和0．3MAC的异氟醚均能影响新斯的明对维库溴铵肌松作用的拮抗。     

Residual neuromuscular block is a risk factor for postoperative pulmonary complications A prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium

Background: After anaesthesia involving pancuronium a high incidence of both residual neuromuscular block and postoperative pulmonary complications (POPC) has been reported. The aim of this study was to compare the incidence of POPC following the use of pancuronium, atracurium, and vecuronium, and to examine the effect of residual neuromuscular block on the incidence of POPC.
Methods: A total of 691 adult patients undergoing abdominal, gynaecological, or orthopaedic surgery under general anaesthesia were randomised to receive either pancuronium, atracurium, or vecuronium. Perioperatively, the response to train-of-four (TOF) nerve stimulation was evaluated manually. Post-operatively, the TOF ratios were measured mechanomyograph-ically, and through a 6-day follow-up the patients were examined for pulmonary complications.
Results: The incidence of residual block, defined as a TOF ratio <0.7, was significantly higher in the pancuronium group (59/226: 26%) than in the atracurium/vecuronium groups (24/450: 5.3%). In the pancuronium group, significantly more patients with residual block developed POPC (10/59: 16.9%) as compared to patients without residual block (8/167 4.8%). In the atracurium/vecuronium groups, the incidence of POPC was not significantly different in patients with (1/24: 4.2%) or without (23/426: 5.4%) residual block. Multiple regression analysis indicated that abdominal surgery, age, long-lasting surgery, and a TOF ratio<0.7 following the use of pancuronium were potential risk factors for the development of POPC.
Conclusion: Postoperative residual block caused by pancuronium is a significant risk factor for development of POPC.     

Benzodiazepines and neuromuscular blocking drugs in patients

The interaction between four benzodiazepines (diazepam, lorazepam, lormetazepam and midazolam) and two nondepolarizing neuromuscular blocking drugs (vecuronium and atracurium) was investigated in 113 patients during general anaesthesia. Neuromuscular function was monitored by recording the mechanical twitch tension of the adductor pollicis muscle of the thumb in response to ulnar nerve stimulation with single supramaximal stimuli of 0.2 ms at 0.1 Hz. In the first group of patients a benzodiazepine (diazepam 20 mg, lorazepam 5 mg, lormetazepam 2 mg or midazolam 15 mg), was injected i.v. 15 min before a single bolus of vecuronium 45 micrograms kg-1. In the second group of patients suxamethonium 1 mg kg-1 was given for endotracheal intubation, and 30 min later the patients received atracurium 200 micrograms kg-1. Fifteen min before injection of atracurium one of the same benzodiazepines as in the first group was injected i.v. Comparisons were made with control patients receiving thiopentone. Neither benzodiazepine caused significant potentiation of neuromuscular blocking agents in comparison with control. With midazolam, however, the duration to 25% and to 75% recovery of the twitch height after vecuronium was significantly longer than with diazepam. The time to 25% recovery of the twitch height after atracurium was significantly longer in patients receiving midazolam than in those receiving diazepam. The recovery index was not influenced by the four benzodiazepines.     

A comparison between vecuronium and atracurium in myasthenia gravis

We evaluated the effect of vecuronium bromide and atracurium besylate on the train–of–four response in the management of muscle relaxation in 20 patients with myasthenia gravis (MG) who were undergoing thymectomy. We confirmed the safe use of these two non–depolarizing muscle relaxants in MG patients. Vecuronium (0.04 mg–kg^-1) demonstrated a lesser clinical duration than did atracurium (0.2 mg–kg^-1) (38± 19 vs 50 ± 21 min, mean ± s.e.mean). The recovery time for vecuronium patients was shorter than that for atracurium patients (22 ± 18 vs 38± 18 min), but the time until onset of neuromuscular blockade was longer with vecuronium (246 ±105 vs 107 ± 103 s). During spontaneous recovery from neuromuscular relaxation, at Tl/C of 25% and 100%, the train–of–four fade with vecuronium was significantly greater than that with atracurium (0.04 ± 0.02, 0.16 ± 0.03 vs 0.17 ±0.01, 0.83 ± 0.03), suggesting that vecuronium had a greater prejunctional effect than did atracurium.     

Train-of-Four recovery after pharmacologic antagonism of pancuronium-, pipecuronium-, and doxacurium-induced neuromuscular block in anaesthetized humans

Previous studies have suggested that the increased duration of action of long-acting neuromuscular relaxants may make their pharmacologic antagonism more difficult and, thus, increase the likelihood of residual block. This hypothesis was tested in healthy, adult humans who received a background of isoflurane/N₂O/fentanyl anaesthesia.
Study subjects were paralyzed with either pancuronium (N=8), pipecuronium (N=8), or the longer-acting relaxant, doxacurium (N=8). Neuromuscular function was monitored, and, using a blinded, randomized study design, the relaxants were titrated to identify the ED₉₅ dose in each patient. Thereafter, spontaneous recovery was observed until there was 25% ofbaseline response to the first supramaximal twitch (Tl) in a train-of-four (TOF). At this time, the block was antagonized with neostigmine 0.07 mg/kg and glycopyrrolate 0.014 mg/kg i.v., and recovery of TOF was recorded.
Spontaneous recovery to 25% of the baseline Tl response occurred at 52± 14 min (mean±SD) following administration of either pancuronium and pipecuronium, and 85 ±33 min following doxacurium ( P <0.05 for doxacurium versus pancuronium and pipecuronium). In doxacurium-rreated patients, reversal of block with neostigmine was less predictable and less complete than with the other two relaxants. For example, the ratio of the fourth to first twitch (T4/T1) of the TOF at 10 and 15 min after reversal was significantly less with doxacurium (59 ±14% and 61±16%, respectively) than with either pancuronium (75±6% and 75±10%) or pipecuronium (76±9% for both). At 30 min post-neostigmine, the incidence of residual block (i.e. T4/T1 <0.70) was: pancuronium 2 patients, pipecuronium 1 patient, and doxacurium 5 patients.
These studies support the hypothesis that incomplete reversal of neuromuscular block is more likely with longer-acting neuromuscular relaxants.     

Effects of propofol and isoflurane on the neuromuscular block induced by atracurium]

Speed of onset, duration of action and recovery time for a bolus injection of atracurium were measured in two groups of patients. In group I anaesthesia considered of propofol, fentanyl, nitrous oxide and oxygen mixture. The induction dose of propofol was 2 mg/kg-1 followed by an infusion of 9.0 mg/kg-1/h-1 for first half hour and 4.5 mg/Kg-1/h-1 subsequently. In group II anaesthesia consisted of isoflurane, fentanyl, nitrous oxide and oxygen mixture. Isoflurane was given upon clinical needs. Speed of onset, duration of action, and recovery time for atracurium were measured in the two groups. No statistically significant differences between speed of onset and duration of action between the two groups were found. The recovery period from T1 = 10% to T1 = 70% twitch response was considerably longer with isoflurane (25 min +/- 6) than with propofol (18 min +/- 3) (p less than 0.01). Results obtained suggest that for adequate relaxation during tracheal intubation smaller doses of atracurium are not needed during isoflurane than propofol administration. Because of the longer recovery period of residual neuromuscular blockade during isoflurane anaesthesia decreasing doses of atracurium and careful monitoring of twitch depression tension are also suggested.     

Continuous infusions of atracurium and vecuronium,compared with intermittent boluses of pancuronium: dose requirements and reversal

This study was designed to determine the effect of prolonged infusion on the ease of reversal of atracurium and vecuronium, and whether factors which potentiate the block delayed reversal. In phase one, 40 patients were randomized (double blind) to determine the steady state conditions for atracurium and vecuronium. Fourteen atracurium patients and 17 vecuronium patients were evaluable. The unblinded second phase involved the steady state conditions using halothane or isoflurane and atracurium infusions. The infusion required for 95% twitch depression (TD95) for atracurium was 7.6 +/- 1.1 micrograms.kg-1 x min-1. The requirement for vecuronium changes with time: TD95 at 30 min was 1.01 +/- 0.16, at 60 min 0.89 +/- 0.12 and after 90 min 0.85 +/- 0.17 micrograms.kg-1 x min-1 (P < 0.05). The mean TD95 was 0.94 +/- 0.23 micrograms.kg-1 x min-1. Multivariate regression analysis of the infusion data revealed a vecuronium model predicting TD95 by the duration of infusion (P < 0.05) and weight (P = 0.05). Atracurium TD95 was predicted by age (P = 0.05). The addition of an inhalation agent to atracurium reduced the infusion rate by 2.01 +/- 0.28 micrograms.kg-1 x min-1 (P = 0.0001) for each increase in MAC. The mean reversal times for atracurium with three different anaesthetics and for vecuronium were not different. Reversal of pancuronium blockade, from less profound twitch depression (86.4 vs 95%) took twice as long as for atracurium and vecuronium for which the following predictors were identified: age, weight, duration of infusion, level of blockade, and type of anaesthetic, using a stepwise regression model.(ABSTRACT TRUNCATED AT 250 WORDS)     

七氟烷对罗库溴铵、维库溴铵及阿曲库铵临床药效的影响

目的 以丙泊酚为对照,观察1.3 MAC的七氟烷对罗库溴铵、维库溴铵及阿曲库铵临床药效的影响.方法 选择60例择期腹部手术的病人随机分为6组,每组10人.七氟烷罗库溴铵组(sR组)、七氟烷维库溴铵组(SV组)及七氟烷阿曲库铵组(SA组)分别吸入1.3 MAC的七氟烷及静注芬太尼维持麻醉,丙泊酚罗库溴铵组(CR组)、丙泊酚维库溴铵组(CV组)及丙泊酚阿曲库铵组(CA组)以丙泊酚6 mg·kg-1·h-1～8 mg·kg～·h-1及芬太尼维持麻醉.监测起效时间、最大抑制程度、作用时间、维持速率、恢复时间、恢复指数.结果 七氟烷组与相应的对照组在最大抑制程度、恢复指数方面的无统计学差异,起效时间、作用时间、维持速率、恢复时间有统计学差异.结论 七氟烷能明显延长罗库溴铵、维库溴铵以及阿曲库铵的作用时间和恢复时间并减少其起效时间、维持剂量,但对最大抑制程度和恢复指数则无明显影响.     

Tactile evaluation of train-of-four count as an indicator of reliability of antagonism of vecuronium- or atracurium-induced neuromuscular blockade.

Recent evidence suggests that edrophonium is not the agent of choice to reverse profound neuromuscular blockade but remains an efficacious drug when the level of neuromuscular blockade to be antagonized is modest. We studied 90 healthy adults in an attempt to address the questions: 1) How much variability in such neuromuscular parameters as single twitch height and the train-of-four (TOF) fade ratio (T4/T1) exist when the TOF count first returns to four palpable responses? 2) Is edrophonium a reliable antagonist at this measured point of recovery? 3) What is the optimal dose of edrophonium needed to produce prompt (less than 10 min) and satisfactory (T4/T1 greater than 0.7) reversal when the fourth response of the thumb to indirect TOF stimulation just becomes palpable? Patients were given a bolus atracurium or vecuronium (n = 45 in each group) followed by an iv infusion sufficient to maintain single twitch as measured by electromyography at 10-15% of control values. At the end of surgery, the infusion was terminated and spontaneous recovery was allowed to begin. Once the tactile TOF count was four, edrophonium 0.3, 0.5, or 0.75 mg/kg was administered. At a count-of-four the first twitch averaged 37% of control (+/- 8.5% standard deviation; pooled data from all groups) and the mean T4/T1 ratio was 0.14 +/- 0.049. After atracurium neuromuscular blockade, edrophonium 0.3 mg/kg produced adequate antagonism in 10 min. At this time the mean T4/T1 ratio was 0.79 +/- 0.07 and the lowest observed value was 0.67. Increasing the edrophonium dose to 0.75 mg/kg accelerated recovery by 4-5 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Utility of double burst stimulation in the detection of residual neuromuscular blockade

OBJECTIVE: To assess the usefulness of double burst stimulation (DBS) for detecting neuromuscular blockade caused by atracurium and vecuronium. PATIENTS AND METHODS: One hundred nineteen adult patients were randomly assigned to receive atracurium (n = 62) or vecuronium (n = 57), with electromyographic monitoring of the number of responses to train of four (TOF) stimuli, TOF-ratio (TR) and the amplitude of the first TOF response (T1) in the pollicis adductor and the response to neurostimulator DBS in the contralateral forearm. During recovery from neuromuscular blockade an independent anesthesiologist manually assessed two responses to DBS every minute as being clearly differentiated, doubtful or undifferentiated. The results were later compared to T1 and TR. RESULTS: Significant differences (p < 0.05) between groups were observed for TR in doubtful (0.27 +/- 0.18 and 0.34 +/- 0.17 for atracurium and vecuronium, respectively) and undifferentiated (0.34 +/- 0.22 and 0.43 +/- 0.18, respectively) responses to DBS, and for T1 with three TOF responses (26.0 +/- 13.6 and 33.1 +/- 14.2, respectively) or four responses (30.9 +/- 14.1 and 38.7 +/- 18.4, respectively). T1 values when TR was 0.75 (extubation criterion) were 68.1 +/- 23.8% and 60.5 +/- 17.4% for the atracurium and vecuronium groups, respectively (NS). CONCLUSIONS: Assuming that DBS reduces the risk of residual curarization and that a TOF-ratio greater than 0.75 indicates adequate recovery from neuromuscular blockade, manual assessment of DBS response as obtained in this study indicates curarization and equal responses do not guarantee its absence. The most reliable index of recovery from neuromuscular blockade is the TR obtained by electromyographic monitoring.     

Comparison of integrated evoked EMG between the hypothenar and facial muscle groups following atracurium and vecuronium administration

In 17 healthy patients undergoing O2.N2O.isoflurane anaesthesia, following atracurium or vecuronium administration, we compared simultaneous integrated evoked electromyograms (IEEMGs) during spontaneous recovery of the adductor digiti minimi (ADM) and orbicularis oris (OOM) muscle groups in response to train-of-four (TOF) stimulation of the ulnar and facial nerves, respectively. In all patients, the onset of neuromuscular recovery occurred first in the OOM. The time required to recover to a T4/T1 = 0.70 +/- 0.01 (SD) was earlier in the OOM compared with the ADM muscles in both the atracurium (33.4 +/- 5 vs 46.5 +/- 8, P less than 0.005) and vecuronium (46.5 +/- 12 vs 60.3 +/- 20, P less than 0.005) groups. When the OOM attained a T4/T1 = 0.70 +/- 0.01, the simultaneous T4/T1 in the ADM was 0.29 +/- 0.15 (P less than 0.05) in the atracurium group and 0.41 +/- 0.16 (P less than 0.01) in the vecuronium group. We conclude that (1) the facial muscles (OOM) recover earlier than the hypothenar muscles (ADM) and (2) an EMG T4/T1 = 0.70 in the facial muscles may not indicate adequate recovery of neuromuscular function.     

Use of vecuronium bromide and atracurium besylate in continuous intravenous infusion in urologic surgery

The effects of continuous i.v. infusion of atracurium and vecuronium monitored by TOF supplied by an ABM monitor have been compared in 60 patients subdivided into four groups and submitted to anaesthesia with isoflurane for urological surgery interventions. Groups A and V received respectively an initial bolus of 0.5 mg/kg atracurium and of 0.08 mg/kg vecuronium followed immediately by continuous i.v. infusion of 5.5 micrograms/kg/min. Atracurium or 0.9 micrograms/kg/min of vecuronium; recovery of neuromuscular function happened spontaneously. Groups A' and V' differed by virtue of the use of 0.04 mg/kg prostigmin in the recovery phase. Average consumption of atracurium and vecuronium were respectively 5.1 +/- 1.75 micrograms/kg/min (2.6-9.03) and 0.75 +/- 0.20 micrograms/kg/min (0.5-1.2) in groups A-A' and V-V'. In groups A and V Recovery time 25-75" of T1 and TR presented a statistically significant difference (p less than 0.05) in favour of atracurium. In groups A' and V' the same parameters presented a statistically non-significant difference (p greater than 0.05). The ratio TI/TR does not vary to a statistically significant extent in the 4 groups. The number of infusion rate variations needed to maintain stable neuromuscular block was lower in the atracurium groups.     

四个成串刺激和双短强直刺激用于评价神经肌肉传导阻滞的比较

采用单盲法对１０例患者比较目测或触感四个成串刺激（ＴＯＦ）和双短强直刺激（ＤＢＳ）肌收缩效应衰减，用于评价神经肌肉传导阻滞的相关性及可靠程度。结果发现，ＤＢＳ比值（ＤＢＳＲ）印ＴＯＦ比值（Ｔ４／Ｔ１）之间具有良好的相关性（ｒ＝０．９７，Ｐ＜０．００１）。在 Ｔ４／Ｔ１；低于 ０．７时、ＴＯＦ和ＤＢＳ的衰减检出率分别为 ３５％和 ６５％（Ｐ＜０．０１）；当 Ｔ４／Ｔ１为 ０． ４～０． ５时，ＴＯＦ和 ＤＢＳ的衰减检出率分别为 ３５／和８０％；当Ｔ４／Ｔ１为０．５～０．６时，ＴＯＦ的衰减检出率为７％，而ＤＢＳ的衰减检出率为６７％；当Ｔ４／Ｔ１为０．６～０．７时，ＴＯＦ已不能检测到衰减。但ＤＢＳ的衰减检出率仍有：３６％．但当Ｔ４／Ｔ１恢复到０．７以上时，ＤＢＳ的分辨率仅为２％．由此可见，如果仅凭目测或触感评价术后肌张力的恢复情况，则ＴＯＰ未检测到衰减并不能排除严重的肌张力恢复不全，而ＤＢＳ未检测到衰减时，肌张力已较好恢复。     

Early and late reversal of rocuronium and vecuronium with neostigmine in adults and children.

We investigated the influence of the timing of neostigmine administration on recovery from rocuronium or vecuronium neuromuscular blockade. Eighty adults and 80 children were randomized to receive 0.45 mg/kg rocuronium or 0.075 mg/kg vecuronium during propofol/fentanyl/N2O anesthesia. Neuromuscular blockade was monitored by train-of-four (TOF) stimulation and adductor pollicis electromyography. Further randomization was made to control (no neostigmine) or reversal with 0.07 mg/kg neostigmine/0.01 mg/kg glycopyrrolate given 5 min after relaxant, or first twitch (T1) recovery of 1%, 10%, or 25%. Another eight adults and eight children received 1.5 mg/kg succinylcholine. At each age, spontaneous recovery of T1 and TOF was similar after rocuronium and vecuronium administration but was more rapid in children (P < 0.05). Spontaneous recovery to TOF0.7 after rocuronium and vecuronium administration in adults was 45.7 +/- 11.5 min and 52.5 +/- 15.6 min; in children, it was 28.8 +/- 7.8 min and 34.6 +/- 9.0 min. Neostigmine accelerated recovery in all reversal groups (P < 0.05) by approximately 40%, but the times from relaxant administration to TOF0.7 were similar and independent of the timing of neostigmine administration. Recovery to T1 90% after succinylcholine was similar in adults (9.4 +/- 5.0 min) and children (8.4 +/- 1.1 min) and was shorter than recovery to TOF0.7 in any reversal group after rocuronium or vecuronium administration. Recovery from rocuronium and vecuronium blockade after neostigmine administration was more rapid in children than in adults. Return of neuromuscular function after reversal was not influenced by the timing of neostigmine administration. These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated. Implications: These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated. Although spontaneous and neostigmine-assisted recovery is more rapid in children than in adults, in neither is return of function as rapid as after succinylcholine administration.     

Potentiation of nondepolarizing muscle relaxants by nifedipine iv in inhalation anesthesia

Calcium entry blockers are now widely used in the treatment of cardiovascular diseases. Nifedipine is established for the treatment of perioperative hypertension during anesthesia. Previous animal experiments have demonstrated that calcium entry blockers potentiate the neuromuscular response induced by nondepolarizing blocking drugs. Occasional observations in patients have led to the suggestion that this phenomenon may be of clinical significance. The interaction of nifedipine with nondepolarizing muscle relaxants in patients was assessed in a prospective clinical study. PATIENTS AND METHODS. Atracurium or vecuronium was administered for muscular relaxation in 44 patients anesthesized with isoflurane in nitrous oxide/oxygen. Monitoring included checks on noninvasive blood pressure, heart rate, pharyngeal temperature, tidal volume, end-tidal CO2 and neuromuscular transmission with a Datex ABM 100 Relaxograph ("train of four"). In the first study protocol atracurium was given to the patients after the intubation dose of 0.5 mg/kg in equal repetition doses of 0.2 mg/kg whenever T1 reached 25%. In 12 patients with the second repetition dose 1 mg nifedipine was injected i.v. The duration of neuromuscular depression with nifedipine until T1 reached 25% again was compared with the duration without nifedipine in the same patient. In the second protocol, constant neuromuscular blockade was accomplished in 11 patients by administration of atracurium or vecuronium at a constant perfusion rate at a level of 75% twitch depression. After 15 min of stable neuromuscular blockade 1 mg nifedipine was injected. In the third study protocol, 1 mg nifedipine i.v. was given at the end of anesthesia when the patients began to breathe spontaneously (T1 was at least 25%). RESULTS. In each patient there was a significant prolongation of neuromuscular blockade from 29 min +/- 6 min up to 40 min +/- 8 min when nifedipdine was given with the second repetition dose (P less than 0.001). During continuous relaxation with constant neuromuscular depression nifedipine increased the neuromuscular blockade from 75% up to 90% +/- 4% (P less than 0.05). In patients with spontaneous breathing and fading but still existing neuromuscular blockade nifedipine injection resulted in hypoventilation. The cardiovascular effects of 1 mg nifedipine, although significant, attained no clinically relevant values. CONCLUSIONS. Our results confirm previous assumptions of synergistic effects of neuromuscular blocking drugs and nifedipine in patients. This synergistic effect includes both duration and intensity of neuromuscular blockade. In the postoperative period patients may be endangered by nifedipine therapy if recovery from the neuromuscular depression is not complete.     

Does vecuronium accumulate in the renal transplant patient?

Twenty ASA physical status Class III patients undergoing cadaver renal transplantation were studied. After 90 per cent T1 recovery, as determined by train-of-four measurement, from 1.0 mg.kg-1 succinylcholine to facilitate tracheal intubation, nine patients received atracurium 0.25 mg.kg-1 (Group I) and 11 patients received vecuronium 0.05 mg.kg-1 (Group II) intravenously. The following measurements were made: time to maximum block onset (first dose Max), injection to start of recovery (start REC1), injection to 25 per cent T1 twitch recovery (REC 251), injection to 75 per cent T1 (REC 75(1], injection to 90 per cent T1 (REC 90(1] and time from 25-75 per cent recovery T1 (REC 25-75(1]. Maximum blockade (Max block 1) was also measured. At 90 per cent T1 recovery, if time permitted, an identical dose of the appropriate relaxant was administered. Time from second dose to onset of maximum block (second dose Max) and 90 per cent recovery after second dose (REC 90(2] were then measured. At the conclusion of surgery, neuromuscular blockade was reversed with neostigmine 2.5 mg and glycopyrrolate 0.5 mg. One way ANOVA was performed to determine significance between the groups and a p less than 0.05 was considered significant. A paired t test was also performed between REC 90(1) and REC 90(2) for atracurium and vecuronium respectively. A p less than 0.05 was again considered significant. Measurement of first dose Max, start REC1, REC25(1), REC 75(1), REC 90(1), REC 25-75(1) and Max block 1 revealed no difference between the patients receiving an initial dose of atracurium and those receiving vecuronium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atracurium and vecuronium interaction with gentamicin and tobramycin

Drug interactions between the aminoglycosides (tobramycin and gentamicin) and atracurium and vecuronium were studied prospectively in 44 patients. Twenty-two patients had therapeutic serum levels of tobramycin or gentamicin and 22 served as controls. Onset time, clinical duration, and time to spontaneous recovery of T4/T1 ratio of 0.70 after atracurium or vecuronium injection were measured. No statistically significant differences were found in onset time, but clinical duration and time to recovery were significantly longer in patients receiving tobramycin or gentamicin and paralyzed with vecuronium than for controls (P less than 0.01 for clinical duration and P less than 0.0005 for recovery). The neuromuscular block produced by atracurium was not significantly influenced by the presence of therapeutic serum levels of tobramycin or gentamicin. We conclude that for patients treated with these antibiotics, atracurium may present some advantages over vecuronium when a prolonged block is not desired.