The optimal bolus dose of alfentanil for tracheal intubation during sevoflurane induction without neuromuscular blockade in day-case anaesthesia

Background: The purpose of this study was to determine the optimal bolus dose of alfentanil required to provide successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane and 60% nitrous oxide without neuromuscular blockade in adult day-case anaesthesia.
Methods: Twenty-four adults, aged 18–60 years, undergoing general anaesthesia for short ambulatory surgery were enroled into the study. After vital capacity induction, with sevoflurane 5% and 60% nitrous oxide in oxygen, pre-determined dose of alfentanil was injected over 30 s. The dose of alfentanil was determined by modified Dixon's up-and-down method (2 μg/kg as a step size). Ninety seconds after the end of bolus administration of alfentanil, the trachea was intubated. Systolic blood pressure, heart rate and SpO₂ were recorded at anaesthetic induction, before, 1 min and 3 min after intubation.
Results: The bolus dose of alfentanil for successful tracheal intubation was 10.7±2.1 μg/kg in 50% of patients during inhalation induction. From probit analysis, 50% effective dose (ED₅₀) and ED₉₅ values (95% confidence limits) of alfentanil were 10.7 μg/kg (8.0–12.9 μg/kg) and 14.9 μg/kg (12.9–31.1 μg/kg), respectively.
Conclusions: Using the modified Dixon's up-and-down method, the bolus dose of alfentanil for successful tracheal intubation was 10.7±2.1 μg/kg in 50% of adult patients during inhalation induction using 5% sevoflurane and 60% nitrous oxide in oxygen without neuromuscular blocking agent in day-case anaesthesia.     

The optimal dose of remifentanil for intubation during sevoflurane induction without neuromuscular blockade in children

The optimal dose of remifentanil needed to produce successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane without the use of neuromuscular blocking drugs, was investigated in 25 children aged 3-10 years. Sixty seconds after inhalation induction of anaesthesia using sevoflurane 5% in 100% oxygen, a predetermined dose of remifentanil was injected over 30 s. The dose of remifentanil was determined using the modified Dixon's up-and-down method (0.2 microg x kg(-1) as a step size). The first patient was tested at 1.0 microg x kg(-1) remifentanil. Ninety seconds following the bolus administration of remifentanil, the child's trachea was intubated. The optimal bolus dose of remifentanil required for successful tracheal intubation was 0.56 (0.15) microg x kg(-1) in 50% of children during inhalation induction using 5% sevoflurane in the absence of neuromuscular blocking drugs. Using probit analysis, the 95% effective dose (ED(95)) of remifentanil was 0.75 microg x kg(-1) (95% confidence limits 0.63-1.38 microg x kg(-1)).     

芬太尼复合七氟醚诱导无肌松插管的量效关系

目的 观察芬太尼复合七氟醚诱导无肌松插管的半数有效量(ED_(50)).方法 择期短小手术患者26例,ASA Ⅰ-Ⅱ,年龄25～45岁纳入研究.8%七氟醚肺活量诱导,跟睑反射消失后,维持呼气末七氟醚浓度3%,按照改良Dixon序贯法调整芬太尼剂量(剂量梯度为0.4 μg/kg),静脉注射芬太尼4 min后气管插管.记录麻醉诱导前平均动脉压(MAP)、心率(HR)和熵指数(Entropy indices)的基础值以及捅管前后1 min及插管后3 min的变化.结果 8%七氟醚诱导,维持呼气末浓度3%,成功无肌松气管插管的芬太尼ED_(50)为(1.2±0.3)μg/kg,采用probit分析方法 芬太尼ED_(50)和ED95及(95%可信区间)分别为1.2 μg/kg(0.9～1.6) μg/kg和1.9 μg/kg(1.6～3.9) μg/kg.结论 8%七氟醚肺活量诱导,维持呼气末七氟醚浓度3%,无肌松满意气管插管的芬太尼ED_(50)为(1.2±0.3)μg/kg.     

芬太尼或瑞芬太尼复合七氟醚诱导在无肌松条件下插管的应用

目的计算芬太尼或瑞芬太尼复合七氟醚诱导在无肌松条件下插管的半数有效量(ED50),比较抑制气管插管反应的效果。方法择期短小手术患者49例,ASAⅠ或Ⅱ级,年龄20～50岁。按照入室顺序随机分为芬太尼组(F组,n=23)和瑞芬太尼组(R组,n=26)。8%七氟醚肺活量诱导,眼睑反射消失后,维持呼气末七氟醚浓度(CETSev)为3%。按照改良Dixon序贯法调整芬太尼(剂量梯度为0.05μg/kg)或瑞芬太尼的剂量(剂量梯度为0.1μg/kg),静脉注射芬太尼或瑞芬太尼4min后气管插管。记录患者眼睑反射消失时间及气管插管反应。结果芬太尼ED50为1.30μg/kg(95%CI1.25～1.35μg/kg),瑞芬太尼ED50为0.47μg/kg(95%CI0.39～0.53μg/kg)。F组声带活动、呛咳和体动的发生率均明显高于R组(P<0.05)。结论无肌松条件下瑞芬太尼较芬太尼能更好地抑制气管插管反应。     

七氟醚诱导无肌松下舒芬太尼抑制气管插管反应的浓度

目的 测定七氟醚诱导无肌松条件下舒芬太尼抑制气管插管反应的效应室靶浓度(EC50和EC95).方法 选择27例ASA Ⅰ或Ⅱ级择期全麻手术患者,吸入8%七氟醚诱导同时靶控输注(TCI)舒芬太尼,舒芬太尼靶浓度按改良序贯法增加或减少0.02 ng/ml.患者意识消失后七氟醚浓度降至5%,待舒芬太尼的血浆浓度和效应室浓度平衡1 min后行气管插管.用概率单位回归法计算出舒芬太尼抑制气管插管反应的EC50、EC95及相应的95%可信区间(CI).结果 舒芬太尼抑制气管插管反应的EC50为0.325 ng/ml,95%CI为0.307～0.342 ng/ml;EC95为0.363 ng/ml,95%CI为0.344～0.498 ng/ml.结论 七氟醚诱导时无肌松条件下舒芬太尼抑制气管插管反应的EC50和EC95为0.325 ng/ml和0.363 ng/ml.     

Optimal dose of propofol for intubation after sevoflurane inhalation without neuromuscular blocking agent in children

Background: This study was designed to determine the optimal dose of propofol for excellent intubating conditions in children without neuromuscular blockade at various alveolar concentrations of sevoflurane. Methods: Sixty‐three children, aged 0.5–5 years, were randomized to three groups of end‐tidal sevoflurane concentration (ET_sevo) 3%, 3.5%, and 4%. Inhalation anesthesia was started with sevoflurane 7% in 100% oxygen. When the patients became unconscious, inspired concentration was adjusted to obtain the target ET_sevo for each group. When ET_sevo reached the target concentration, a predetermined dose of propofol was given and tracheal intubation was performed. The proper dose of propofol was determined using the ‘up‐and‐down’ method. Results: The median dose (95% confidence intervals) of propofol for excellent tracheal intubating conditions in 50% of children were 1.25 mg/kg (0.84–1.75) at ET_sevo of 3%, 0.76 mg/kg (0.35–1.21) at 3.5%, and 0.47 mg/kg (0.26–1.09) at 4%. The frequency of adverse effects was not different between groups during induction and recovery. Conclusion: Propofol 1.5–2 mg/kg provides excellent intubating conditions at 3–4% ET_sevo in children without using any neuromuscular blocking agent.     

The effect of ketamine on tracheal intubating conditions without neuromuscular blockade during sevoflurane induction in children

Purpose  

The purpose of this study was to investigate the effect of ketamine on intubating conditions for tracheal intubation during anesthesia induction with sevoflurane and alfentanil in pediatric patients.     

Bispectral index guided timing of intubation without neuromuscular blockade during sevoflurane induction of anaesthesia in adults

The aim of this study was to assess the effectiveness of bispectral index monitoring (BIS) as a guide to the timing of intubation during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents in adults, and specifically, whether a target BIS value of 25 provides better intubating conditions than a target BIS of 40. Forty patients were randomized into one of two groups, a target BIS 25 (n =21) or a target BIS 40 (n =19). Patients received premedication with midazolam 20 microg/kg and fentanyl 0.5 microg/kg. Sevoflurane induction of anaesthesia was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was then intubated, with intubating conditions being assessed using a standardized scale. The BIS 25 group had a superior median intubating score of 4 (range 3-9,[IQR 4-5]) vs the BIS 40 group with a median of 7 (5-10, [6-9], P<0.001). The time to reach target BIS values was not statistically different (BIS 25 group 6.6 min, BIS 40 group 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3% +/- 1.2%) vs the BIS 40 group (3.5% +/- 0.95) (P<0.001). There was no statistical difference in haemodynamic parameters between groups. A target BIS value of 25 provides good to excellent intubating conditions and better intubating conditions than a target BIS of 40 during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents.     

The optimal dose of remifentanil for acceptable intubating conditions during propofol induction without neuromuscular blockade

Study ObjectiveTo determine the optimal remifentanil dose required to provide acceptable intubating conditions following induction of anesthesia with propofol without using neuromuscular blockade.DesignDose-response study.SettingOperating room of a university hospital.Patients50 ASA physical status 1 men, aged between 20 and 40 years, who were scheduled for general anesthesia.InterventionsIntubating conditions were evaluated according to the scoring system described by Viby-Mogensen et al. Successful intubation was defined as excellent or good.MeasurementsFor induction of anesthesia, an intravenous (IV) bolus dose of propofol 2.0 mg/kg was given over 30 seconds followed by the administration of predetermined IV remifentanil over 30 seconds; intubation was performed 90 seconds after completion of the remifentanil administration. The dose of remifentanil used for each patient was determined by the response of the previously tested patients, using the modified Dixon's up-and-down method (using 0.2 μg/kg as a step size). The first patient was tested with remifentanil 1.0 μg/kg. If intubation failed, the remifentanil dose was increased by 0.2 μg/kg; if intubation was successful, the dose was decreased by 0.2 μg/kg. Mean arterial pressure (MAP), heart rate (HR), and peripheral oxygen saturation were recorded during the study period.Main ResultsAccording to probit analysis, the effective dose of remifentanil in 50% (ED₅₀) and 95% (ED₉₅) of patients were 1.40 μg/kg and 2.40 μg/kg, respectively. Preintubation and postinduction HR and MAP values were lower than preinduction values (P < 0.001).ConclusionThe optimal bolus dose of remifentanil for acceptable intubating conditions was 2.40 μg/kg (95% confidence interval, 1.90-9.0 μg/kg) in 95% of patients during induction of anesthesia with propofol 2.0 mg/kg without neuromuscular blocking agents.     

Optimal rocuronium dose for intubation during inhalation induction with sevoflurane in children

Background. We studied 120 children aged 2–7 yr in a prospective,randomized, assessor-blinded fashion to define the optimal rocuroniumdose which provides a 95% probability of acceptable intubationconditions (ED_95TI) during inhalation induction with sevoflurane. Methods. After inhalation induction with 8% sevoflurane in 60%nitrous oxide and 40% oxygen, and loss of the eyelash reflex,we administered rocuronium (0.1, 0.15, 0.22, 0.3, or 0.6 mgkg^–1) or placebo. We quantified neuromuscular functionby stimulation of the ulnar nerve at 0.1 Hz to produce contractionof the adductor pollicis muscle using accelerometry. Intubationconditions were assessed 2 min after test drug injection. Theoptimal rocuronium dose was defined as the lowest dose, whichallowed acceptable intubation conditions in 95% of children(ED_95TI). Results. Two minutes after injection of placebo or rocuronium,intubation conditions were acceptable in 35, 45, 80, 90, 95,and 100% of children, respectively. Rocuronium 0.07 [CI 0.02–0.11],0.24 [0.19–0.31], and 0.29 [0.23–0.38] mg kg^–1provided 50, 90, and 95% probability of acceptable intubatingconditions. When thumb acceleration was depressed by 50% ormore, intubating conditions were considered acceptable in 97%of children. Recovery of the train-of-four ratio to 0.8 averaged12 (7), 16 (7), 24 (7), 24 (8), and 50 (22) min after the respectivedose of rocuronium. Conclusions. During inhalation induction with 8% sevofluranein 60% nitrous oxide, rocuronium 0.29 mg kg^–1 (ED₉₅) optimizesintubation conditions for surgery of short duration. Br J Anaesth 2002; 89: 277–81     

Propofol 2 mg/kg is superior to propofol 1 mg/kg for tracheal intubation in children during sevoflurane induction

Background: Propofol has been used to facilitate tracheal intubation within a short time of sevoflurane induction without a muscle relaxant in children. We compared as the primary outcome the incidence of excellent intubating conditions after 8% sevoflurane and propofol 1 or 2 mg/kg. Methods: One hundred and four patients (2–7 years) were randomly assigned to receive propofol 1 mg/kg in group SP1 (n=53) or propofol 2 mg/kg in group SP2 (n=51) after inhalation induction using sevoflurane 8% in oxygen. Forty‐five seconds after propofol and controlled ventilation, intubating conditions were assessed using a four‐point scoring system based on ease of laryngoscopy, vocal cords position, coughing, jaw relaxation and limb movement. Heart rate and systolic blood pressure were measured as baseline, after sevoflurane induction, propofol, intubation and at 2 and 5 min following intubation. Results: Three patients in group SP1 were excluded from analysis. Time from sevoflurane induction to intubation (248.9±71.3 s in group SP1 vs. 230.9±61.3 s in group SP2) and endtidal sevoflurane before intubation (5.6±1.6% in group SP1 vs. 5.2±1.5% in group SP2) did not differ between the two groups. The incidence of excellent intubating conditions was significantly higher in group SP2 compared with group SP1 [47/51 (92%) vs. 28/50 (56%)]. The incidence of acceptable intubating conditions was significantly higher in group SP2 compared with group SP1 [48/51 (94%) vs. 35/50 (70%)]. No hemodynamic difference was noted at any time point between the two groups. Conclusion: Propofol 2 mg/kg during 8% sevoflurane induction resulted in a higher proportion of excellent intubating conditions compared with propofol 1 mg/kg.     

复合七氟烷吸入用于患儿无肌松药气管插管时瑞芬太尼的半数有效剂量

目的 确定复合七氟烷吸入用于患儿无肌松药气管插管时瑞芬太尼的半数有效剂量(ED50).方法 择期手术患儿25例,年龄4～9岁,ASA Ⅰ或Ⅱ级.吸入5%七氟烷行麻醉诱导,维持呼气末二氧化碳分压30～35 mm Hg.吸入七氟烷3 min后静脉注射瑞芬太尼,注射时间30 s,瑞芬太尼注射完毕后90 s时行气管插管.采用序贯法进行试验,瑞芬太尼初始剂量为1.2 μg/kg,相邻剂量比值为1.2.采用Viby-Mogensen评分法评价气管插管条件,气管插管失败时,静脉注射罗库溴铵0.3 mg/kg,待肌肉松驰后再行气管插管.计算瑞芬太尼的ED50及其95%可信区间.结果 复合5%七氟烷吸入用于患儿无肌松药气管插管时瑞芬太尼的ED50及其95%可信区间为0.68(0.65～0.71)μg/kg.结论 复合5%七氟烷吸入用于患儿无肌松药气管插管时瑞芬太尼的ED50及其95%可信区间为0.68(0.65～0.71)μg/kg.     

Anaesthetic induction time for tracheal intubation using sevoflurane or halothane in children

The current study was designed to determine the anaesthetic induction time required for tracheal intubation (Time_EI) with equipotent inspired concentrations of 5% sevoflurane and 2.5% halothane in oxygen. Time_EI that prevents 50% and 95% of patients from coughing and gross purposeful muscular movements after intubation was defined as Time_EI50 and Time_EI95, respectively. Thirty-six patients aged 1–7 years were enrolled in the study. Anaesthesia was induced via mask and when Time_EI attained a predetermined value, intubation was performed using an uncuffed tube. Each Time_EI at which tracheal intubation was attempted was predetermined according to the up-and-down method. When intubation was accomplished without gross purposeful muscular movements, it was considered a smooth intubation. Determination with this method revealed that Time_EI50 and Time_EI95 for the sevoflurane/halothane groups were 147/214 s and 194/255 s, respectively. In conclusion, it is possible to determine Time_EI using an inspired sevoflurane concentration of 5% and halothane 2.5% in oxygen. The technique with 5% sevoflurane seems more practical for paediatric anaesthesia induction in busy clinical situations.     

The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction without muscle relaxation

Study Objective

To determine the most suitable effect-site concentration of remifentanil during lightwand intubation when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL without neuromuscular blockade.

Design

Prospective study using a modified Dixon's up-and-down method.

Setting

Operating room of an academic hospital.

Patients

28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery.

Interventions

Anesthesia was induced by TCI propofol effect-site concentration to 4.0 μg/mL, and the dose of remifentanil given to each patient was determined by the response of the previously tested patient using 0.2 ng/mL as a step size. The first patient was tested at a target effect-site concentration of 4.0 ng/mL of remifentanil. If intubation was successful, the remifentanil dose was decreased by 0.2 ng/mL; if it failed, the remifentanil dose was increased by 0.2 ng/mL. Successful intubation was defined as excellent or good intubating conditions.

Measurements and Main Results

The remifentanil effect-site concentration was measured. The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction using 2% propofol target effect-site concentration to 4 μg/mL was 2.16 ± 0.19 ng/mL. From probit analysis, the effect-site concentration of remifentanil required for successful lightwand intubation in 50% (EC50) and 95% (EC95) of adults was 2.11 ng/mL (95% CI 1.16-2.37 ng/mL) and 2.44 ng/mL (95% CI 2.20-3.79 ng/mL), respectively.

Conclusion

A remifentanil effect-site concentration of 2.16 ± 0.19 ng/mL given before a propofol effect-site concentration of 4 μg/mL allowed lightwand intubation without muscle relaxant.     

婴幼儿单纯吸入七氟醚诱导时的半数有效量

目的 测定婴幼儿全凭七氟醚诱导插管时的半数有效量(ED50).方法 选择ASAⅠ级患儿42例,年龄6个月～3岁,起始呼气末七氟醚浓度为4%,观察前一例患儿插管是否成功而序贯地按0.2%的浓度递增或递减.所得数据以加权均数法求得七氟醚的ED50.结果 七氟醚的ED50为4.2%,95%可信区间为4.1%～4.3%.结论 七氟醚可用于婴幼儿全凭吸入诱导插管.     

Optimum priming dose of vecuronium for tracheal intubation

To determine the optimum priming dose of vecuronium, we divided 173 surgical patients into five groups according to priming dose (0, 2.5, 5.0, 7.5, and 10 μg·kg⁻¹). For endotracheal intubation, we administered a priming dose of vecuronium, and then after 4 min, the remainder was injected for a total dosage of 0.15 mg·kg⁻¹. Onset time was determined by a 95% depression of twitch height as shown by electromyography (EMG) of the hypothenar muscles. This was measured by repeating the train-of-four (TOF) stimulation. An increased priming dose shortened the onset time; however, this shortening rate diminished when the dosage was above 7.5 μg·kg⁻¹. In the zero priming dose group there was a significant correlation between onset time and age, and between onset time and body mass index (BMI) in women (r=0.62 and −0.45, respectively); however, this correlation was not observed in men. A priming dose of 10 μg·kg⁻¹ showed a decrease of TOF ratio to 95% or less in 1 out of 25 cases. Although one-third of the patients in the 5 and 7.5 μg·kg⁻¹ groups complained of clinical symptoms such as ptosis, this was clinically allowable. We conclude that the optimum priming dose of vecuronium is 7.5 μg·kg⁻¹; however, in obese patients, a smaller dosage would be recommended.     

Mivacurium-induced neuromuscular blockade during sevoflurane and halothane anaesthesia in children

The neuromuscular blocking effects of mivacurium during sevoflurane or halothane anaesthesia was studied in 38 paediatric patients aged 1–12 yr. All received premedication with midazolam, 0.5 mg · kg⁻¹ po and an inhalational induction with up to 3 MAC of either agent in 70% N₂O and O₂. The ulnar nerve was stimulated at the wrist by a train-of-four stimulus every ten seconds and the force of adduction of the thumb recorded with a Myotrace force transducer. Anaesthesia was maintained with a one MAC end-tidal equivalent of either volatile agent for five minutes before patients received mivacurium (0.2 mg · kg⁻¹) iv. The onset of maximal blockade occurred in 2.4 ± 1.26 (mean ± SD) min with halothane and 1.8 ± 0.54 min with sevoflurane (NS). Four patients failed to achieve 100% block (3 halothane, 1 sevoflurane). The times from injection to 5, 75, and 95% recovery during sevoflurane (9.8 ± 2.6, 19.5 ± 4.4, and 24.2 ± 4.8 min) were greater than during halothane anaesthesia (7.2 ± 2.2, 15.0 ± 4.0, 19.2 ± 4.9 min, respectively (P < 0.005). All patients demonstrated complete spontaneous recovery of neuromuscular function (T₁ > 95%, T₄/T₁ > 75%) during the surgery which lasted 24–63 min. All patients showed clinical signs of full recovery of neuromuscular blockade (i.e., headlift, gag, or cough). Pharmacological reversal was not required. It is concluded that following a single intubating dose of mivacurium, the time to maximum relaxation was not different during halothane and sevoflurane anaesthesia; recovery times to 5, 75 and 95% twitch height were longer during sevoflurane anaesthesia and neuromuscular reversal was not necessary. L’activité neurobloquante du mivacurium pendant l’anesthésie au sévoflurane ou à l’halothane fait l’objet de cette étude réalisée chez 38 enfants de 1 à 12 ans. Tous ont été prémédiqués au midazolam 0,5 mg · kg⁻¹ et l’anesthésie est induite avec un agent volatil jusqu’à MAC 3 de l’un des agents dans du N₂O à 70%. Le nerf cubital était stimulé au poignet au train de quatre aux dix seconds et la force de l’adduction du pouce mesurée avec un transducteur de force Myotrace. L’anesthésie était entretenue avec l’équivalent MAC I d’un des deux agents volatils pendant cinq minutes avant l’administration de mivacurium (0,2 mg · kg⁻¹). Le début du bloc maximum est survenu dans 2,4 ± 1,26 (moyenne ± SD) min avec l’halothane et 1,8 ± 0,54 min avec le sévoflurane (NS). Quatre patients n’ont pas été bloqués à 100% (trois avec l’halothane, un avec le sévoflurane). L’intervalle séparant l’injection à 5; 75, et 95% de la récupération pendant l’anesthésie au sévoflurane (9,8 ± 2,6, 19,5 ± 4,4 et 24,2 ± 4,8 min) a été plus long que pendant l’anesthésie à l’halothane (7,2 ± 2,2, 15,0 ± 4,0, 19,2 ± 4,9 min, respectivement (P < 0,005). An moniteur, chez tous les patients, la fonction neuromusculaire a récupéré spontanément (T₁ > 95%, T₄/T₁ > 75%) au cours de la chirurgie qui a duré de 24–63 min. Tous les patients montraient aussi les signes cliniques d’une récupération complète (par ex., levée de la tête, réflexe pharyngé ou toux). Aucun antagoniste pharmacologique n’a été requis. Il est conclu que le délai jusqu’à la relaxation maximum après une seule dose d’intubation de mivacurium ne diffère pas entre l’anesthésie à l’halothane et l’anesthésie au sévoflurane; les délais de retour à 5, 75 et 95% de la hauteur du twitch sont plus longs pendant l’anesthésie au sévoflurane et il n’est pas nécessaire d’antagoniser le bloc neuromusculaire.

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Supported in part by a grant from Abbott Laboratories, Chicago, Illinois.     

Tactile assessment for the reversibility of rocuronium-induced neuromuscular blockade during propofol or sevoflurane anesthesia

We sought to determine whether tactile train-of-four (TOF) count can predict the efficacy of neostigmine administration for rocuronium-induced blockade during propofol or sevoflurane anesthesia, and to follow subsequent recovery until the TOF ratio reached 0.9. One-hundred-sixty patients, divided into eight equal groups, were randomly allocated to maintenance of anesthesia with propofol or sevoflurane. The tactile response of the adductor pollicis to TOF stimulation was evaluated on one arm, and the mechanomyographic response was recorded on the other. Neuromuscular block was induced with rocuronium 0.6 mg/kg and maintained with rocuronium to 15% of the control first twitch in TOF. Neostigmine 0.07 mg/kg was administered on reappearance of the first (Group I), second (Group II), third (Group III), or fourth (Group IV) tactile TOF response in each anesthesia. At this time, sevoflurane or the propofol dosage was reduced in each group (n = 20 in each group). The times from administration of neostigmine until the TOF ratio recovered to 0.7, 0.8, and 0.9 were recorded. The times [median (range)] to TOF ratio = 0.9 were 8.6 (4.7-18.9), 7.5 (3.4-9.8), 5.4 (1.6-8.6), and 4.7 (1.3-7.2) min in Groups I-IV during propofol anesthesia, respectively, and 28.6 (8.8-75.8), 22.6 (8.3-57.4), 15.6 (7.3-43.9), and 9.7 (5.1-26.4) min in corresponding groups during sevoflurane anesthesia, respectively (P < 0.0001). We recommend more than 2 TOF responses with propofol anesthesia and 4 TOF responses with sevoflurane anesthesia for adequate reversal within 10 and 15 min, respectively. The more tactile TOF responses present at the time of reversal achieved greater adequate recovery; however, tactile TOF responses are not a completely reliable predictor within a reasonable time period.