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.     

Rocuronium zur elektiven Narkoseeinleitung Verlauf der neuromuskulären Blockade und Intubationsbedingungen nach 2facher ED95 (0,6 mg/kg) und nach Dosisreduktion (0,4 mg/kg)

BACKGROUND: Rocuronium is a non-depolarising neuromuscular blocking agent structurally related to vecuronium. The compound has a rapid onset and an intermediate duration of action. The rapid onset is of importance in patients at risk for pulmonary aspiration, for elective induction of anaesthesia slower onset properties generally are accepted. In this context, we asked whether the induction dose of rocuronium may be reduced to doses smaller than 2 x ED95 in situations in which slower onset properties may be acceptable. METHODS: The time course of neuromuscular block and intubating conditions of two different doses rocuronium, 2 x ED95 (0.6 mg/kg) and 1.3 x ED95 (0.4 mg/kg), were investigated in 90 patients. We first determined the time course of neuromuscular block using electromyography (EMG), n = 15 for each group. In the second part the intubating conditions 3 min after injection of either rocuronium 0.6 mg/kg or rocuronium 0.4 mg/kg were evaluated, n = 30 for each group. RESULTS: In the present study reduction of the dose of rocuronium led to a slower onset (148 +/- 32 s vs. 220 +/- 30 s; P < 0.05) and a shorter clinical duration (21 min +/- 4 vs. 36 +/- 7 min; P < 0.05). The recovery index was modified by the dose reduction: 11 +/- 3 min after 0.6 mg/kg rocuronium and 9 +/- 2 min after 0.4 mg/kg. After both doses of rocuronium the intubating conditions were good to excellent, no difference between both rocuronium groups were found. CONCLUSION: In the present study dose reduction from 0.6 mg/kg rocuronium to 0.4 mg/kg rocuronium led to a slower onset and reduced clinical duration. However, the intubating conditions, evaluated 3 min after injection of the muscle relaxant were comparable. This offers new possibilities for muscle relaxation for surgical or diagnostic procedures of short duration and may reduce costs.     

Comparative Pharmacology of Cisatracurium (51W89), Atracurium, and Five Isomers in Cats

Background: Atracurium has four chiral centers and the marketed product is a mixture of ten optical and geometric isomers. Six of the isomers were prepared and evaluated for neuromuscular blocking activity and autonomic effects in anesthetized cats. This study reports the comparative pharmacology of the six isomers and atracurium that led to the selection of one isomer, cisatracurium (Nimbex, 51W89) for clinical development.

Methods: Purpose bred cats, anesthetized with alpha-chloralose (80 mg/kg) and pentobarbital sodium (7 mg/kg) administered intraperitoneally, were used in this study. Neuromuscular blocking effects were assessed from the effects on the tibialis anterior twitch evoked at 0.15 Hz. Inhibition of the autonomic nervous system was assessed from the effects on the nictitating membrane contraction, in response to preganglionic sympathetic nerve stimulation and the bradycardia/vasodepressor responses to vagal nerve stimulation. Cardiovascular effects and plasma histamine concentrations were determined after a bolus injection of cisatracurium or atracurium.

Results: Like atracurium, all six isomers produced dose-dependent neuromuscular block (NMB). The calculated ED95 NMB values varied approximately tenfold (43+/-2 micro gram/kg-488+/-56 micro gram/kg). The "R-series" isomers were more potent than the corresponding "S series" isomers. With the exception of the S,Trans-S', Trans isomer, the NMB effects, i.e., onset times (range 2.6+/-0.2 min to 4.7+/-0.3 min) and total durations (range 9.9+/- 1.4 min to 14+/-0.9 min), of the other five isomers were very similar to that of atracurium. The former isomer had a relatively short duration of action. The 25-75% recovery times after cisatracurium at 1x ED sub 95 (4.4+/-0.4 min), 4x ED95 (4.5+/-0.4 min), and continuous infusions lasting at least 60 min that maintained 95-99% NMB (4.8+/-0.4 min) indicated a noncumulative effect. The vagal ID50: NMB ED95 ratios for atracurium and the six isomers ranged from 2 to 27. The sympathetic ID25: NMB ED95 ranged from 2.7 to 60. Atracurium and all of the isomers, except cisatracurium, produced cardiovascular effects after intravenous bolus administration at large doses (700-4,800 micro gram/kg). In contrast to atracurium, there were no changes in plasma histamine concentrations associated with the administration of doses of cisatracurium equivalent to 60x the NMB ED95 (62+/-8 micro gram/kg).     

Effects of an Intubating Dose of Succinylcholine and Rocuronium on the Larynx and Diaphragm: An Electromyographic Study in Humans

Background: Paralysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle.

Methods: Electromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium.

Results: The maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P 相似文献   

Bioavailability of Intramuscular Rocuronium in Infants and Children

Background: Intramuscular rocuronium, in doses of 1,000 micro gram/kg in infants and 1,800 micro gram/kg in children, produces complete twitch depression in 5-6 min. To determine the rate and extent of absorption of rocuronium after intramuscular administration, blood was sampled at various intervals after rocuronium administration by both intramuscular and intravenous routes to determine plasma concentrations (Cp) of rocuronium.

Methods: Twenty-nine pediatric patients ages 3 months to 5 yr were anesthetized with N2 O and halothane. The trachea was intubated, ventilation was controlled, and adductor pollicis twitch tension was measured. When anesthetic conditions were stable, rocuronium (1,000 micro gram/kg for infants and 1,800 micro gram/kg for children) was injected either intramuscularly (in the deltoid muscle) or intravenously. Four venous plasma samples were obtained from each child 2-240 min after rocuronium administration. A mixed-effects population pharmacokinetic analysis was applied to these values to determine bioavailability, absorption rate constant, and time to peak Cp with intramuscular administration.

Results: With intramuscular administration, rocuronium's bioavailability averaged 82.6% and its absorption rate constant was 0.105 min sup -1. Simulation indicated that Cp peaked 13 min after rocuronium was given intramuscularly, and that 30 min after intramuscular administration, less than 4% of the administered dose remained to be absorbed from the intramuscular depot.     

Rocuronium versus succinylcholine for rapid sequence induction of anesthesia and endotracheal intubation: a prospective, randomized trial in emergent cases

When anesthesia is induced with propofol in elective cases, endotracheal intubation conditions are not different between succinylcholine and rocuronium approximately 60 s after the injection of the neuromuscular relaxant. In the present study, we investigated whether, in emergent cases, endotracheal intubation conditions obtained at the actual moment of intubation under succinylcholine differ from those obtained 60 s after the injection of rocuronium. One-hundred-eighty adult patients requiring rapid sequence induction of anesthesia for emergent surgery received propofol (1.5 mg/kg) and either rocuronium (0.6 mg/kg; endotracheal intubation 60 s after injection) or succinylcholine (1 mg/kg; endotracheal intubation as soon as possible). The time from beginning of the induction until completion of the intubation was shorter after the administration of succinylcholine than after rocuronium (median time 95 s versus 130 s; P < 0.0001). Endotracheal intubation conditions, rated with a 9-point scale, were better after succinylcholine administration than after rocuronium (8.6 +/- 1.1 versus 8.0 +/- 1.5; P < 0.001). There was no significant difference in patients with poor intubation conditions (7 versus 12) or in patients with failed first intubation attempt (4 versus 5) between the groups. We conclude that during rapid sequence induction of anesthesia in emergent cases, succinylcholine allows for a more rapid endotracheal intubation sequence and creates superior intubation conditions compared with rocuronium.     

Evaluation of the endotracheal intubating conditions of rocuronium (ORG 9426) and succinylcholine in outpatient surgery.

The time-course of action and tracheal intubating conditions of rocuronium and succinylcholine under intravenous anesthesia with propofol, alfentanil, and nitrous oxide were studied in 30 patients undergoing outpatient surgery. The neuromuscular effects of both drugs were quantified by recording the indirectly evoked twitch response of the adductor pollicis muscle after ulnar nerve stimulation (0.1 Hz, 0.2 ms supramaximal stimuli). Patients were given either 0.6 mg/kg rocuronium (n = 20) or 1 mg/kg succinylcholine (n = 10) intravenously. Sixty seconds after the administration of the muscle relaxant, the trachea was intubated and the intubating conditions were scored by a "blinded" assessor. Intubating conditions were not different (P = 0.34) between the rocuronium and succinylcholine groups. The onset and duration of neuromuscular blockade were shorter with succinylcholine than with rocuronium. The depression of the twitch response to 5% of control value occurred in 0.8 +/- 0.1 min with 1 mg/kg succinylcholine and 1.2 +/- 0.5 min with 0.6 mg/kg rocuronium (P less than 0.01). The recovery of the twitch response to 25%, 75%, and 90% of its control value was shorter after succinylcholine (P less than 0.001) and occurred at 8.1 +/- 2.6, 10.3 +/- 3.9, 11.3 +/- 4.6 and 25.3 +/- 5.0, 33.1 +/- 5.9, 36.1 +/- 6.3 min after succinylcholine and rocuronium, respectively. Also the time required for spontaneous recovery from 25% to 75% of the control twitch response was significantly shorter (P less than 0.001) after succinylcholine (2.2 +/- 1.4 min) than after rocuronium (7.8 +/- 2.1 min). It is concluded that in spite of the pharmacodynamic differences between succinylcholine and rocuronium, the intubating conditions after administration of both compounds are similar and develop at the same rate.     

Effects of an intubating dose of succinylcholine and rocuronium on the larynx and diaphragm: an electromyographic study in humans

BACKGROUND: Paralysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle. METHODS: Electromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium. RESULTS: The maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P < or = 0.05). Onset time was not different between the larynx (58+/-10 s), the diaphragm (57+/-8 s), and the adductor pollicis (54+/-13 s), after succinylcholine (all mean +/- SD). After rocuronium, onset time was 124+/-39 s at the larynx, 130+/-44 s at the diaphragm, and 115+/-21 s at the adductor pollicis. After succinylcholine administration, time to 90% recovery was 8.3+/-3.2, 7.2+/-3.5, and 9.1+/-3.0 min at the larynx, the diaphragm, and the adductor pollicis, respectively. Time to 90% recovery after rocuronium administration was 34.9+/-7.6, 30.4+/-4.2, and 49.1+/-11.4 min at the larynx, the diaphragm, and the adductor pollicis, respectively. CONCLUSION: Neuromuscular blocking effect of muscle relaxants on the larynx can be measured noninvasively by electromyography. Although the larynx appears to be resistant to muscle relaxants, we could not demonstrate that its onset time differed from that of peripheral muscles.     

Intramuscular rocuronium in infants and children: a multicenter study to evaluate tracheal intubating conditions, onset, and duration of action.

BACKGROUND: This multicenter, assessor-blinded, randomized study was done to confirm and extend a pilot study showing that intramuscular rocuronium can provide adequate tracheal intubating conditions in infants (2.5 min) and children (3 min) during halothane anesthesia. METHODS: Thirty-eight infants (age range, 3-12 months) and 38 children (age range, 1 to 5 yr) classified as American Society of Anesthesiologists physical status 1 and 2 were evaluated at four investigational sites. Anesthesia was maintained with halothane and oxygen (1% end-tidal concentration if <2.5 yr; 0.80% end-tidal concentration if >2.5 yr) for 5 min. One half of the patients received 0.45 mg/kg intravenous rocuronium. The others received 1 mg/kg (infants) or 1.8 mg/kg (children) of intramuscular rocuronium into the deltoid muscle. Intubating conditions and mechanomyographic responses to ulnar nerve stimulation were assessed. RESULTS: The conditions for tracheal intubation at 2.5 and 3 min in infants and children, respectively, were inadequate in a high percentage of patients in the intramuscular group. Nine of 16 infants and 10 of 17 children had adequate or better intubating conditions at 3.5 and 4 min, respectively, after intramuscular rocuronium. Better-than-adequate intubating conditions were achieved in 14 of 15 infants and 16 of 17 children given intravenous rocuronium. Intramuscular rocuronium provided > or =98% blockade in 7.4+/-3.4 min (in infants) and 8+/-6.3 min (in children). Twenty-five percent recovery occurred in 79+/-26 min (in infants) and in 86+/-22 min (in children). CONCLUSIONS: Intramuscular rocuronium, in the doses and conditions tested, does not consistently provide satisfactory tracheal intubating conditions in infants and children and is not an adequate alternative to intramuscular succinylcholine when rapid intubation is necessary.     

Einfluss des Geschlechts auf den Verlauf der neuromuskulären Blockade nach Rocuronium

BACKGROUND: We studied 40 patients (20 female and 20 male) undergoing elective surgery under general anaesthesia to evaluate the effect of gender on the pharmacodynamics of rocuronium. METHODS: Using electromyography (EMG) we determined the maximal neuromuscular block and time course of action of 0.45 mg/kg rocuronium (1.5 x ED95). RESULTS: Age and body mass index were comparable between females and males (38 (+/- 8) vs. 37 (+/- 10) years and 24.2 (+/- 2.9) vs. 25.2 (+/- 1.7) kg/m2. However, significant differences in weight and height were found between females and males (65.7 +/- 9.3 kg vs. 77.5 +/- 5.5 kg; p < 0.01 and 178 +/- 6.8 cm vs. 164 +/- 6.7 cm; p < 0.01). Onset time was shorter in females (168 +/- 65 s vs. 211 +/- 56 s; p < 0.05). Maximal neuromuscular blockade after 0.45 mg/kg rocuronium was 94 (+/- 3) % in females and 89 (+/- 6) % in males; p < 0.01. Clinical duration was increased in females (23 +/- 5 min vs. 17 +/- 5 min; p < 0.05), while the recovery index was comparable between both groups (9 +/- 4 min in females and 9 +/- 3 min in males; n.s.). CONCLUSION: Compared to men neuromuscular blockade after 0.45 mg/kg rocuronium was more pronounced in women. The onset time was shortened and the clinical duration increased in female patients.     

Mivacurium When Precedent by Pancuronium Becomes a Long-acting Muscle Relaxant

Background: To ensure rapid recovery of neuromuscular block, it might be useful to administer a short-acting relaxant after a long-acting one. Therefore, the interaction between pancuronium and mivacurium was investigated when mivacurium was administered during the recovery from pancuronium block.

Methods: After written informed consent, 41 adult patients were studied during propofol/alfentanil/nitrous oxide/oxygen anesthesia. Neuromuscular function was monitored using an electromyographic (EMG) method. After a stable EMG calibration response, cumulative doses of pancuronium were given to establish a 95% neuromuscular block. In the control group, an ED95 dose of 100 micro gram/kg mivacurium was administered instead of pancuronium. When the EMG response after pancuronium or mivacurium had recovered to 25% of the baseline, a single randomized intravenous bolus dose of 10 or 70 micro gram/kg mivacurium was given. Thereafter, spontaneous recovery of the neuromuscular function was recorded.

Results: The time from pancuronium until T1 25% EMG recovery was 38 +/-12 min (mean+/-SD). The respective times after 10 or 70 micro gram/kg mivacurium were 28+/-8 and 54+/-7 min in the pancuronium group or 3+/-1 (n = 3) and 10+/-4 min in the mivacurium group (P = 0.0001). Times to 95% EMG recovery after 10 or 70 micro gram/kg mivacurium were 77+/-14 and 97+/-16 min in the pancuronium group and 11+/-3 and 20+/-7 min in the mivacurium group, respectively (P < 0.0001). Recovery indexes after 10 or 70 micro gram/kg mivacurium were 26+/-4 and 22+/- 6 min in the pancuronium group or 7+/-3 (n = 3) and 5+/- 2 min in the mivacurium group, respectively (P < 0.0001). Times from the administration of 10 or 70 micro gram/kg mivacurium until train-of-four ratio 0.7 were 94+/-16 and 111+/-14 min in the pancuronium group and 12+/-4 and 22+/-8 min in the mivacurium group, respectively (P < 0.0001).     

An alternate method for estimating the dose-response relationships of neuromuscular blocking drugs

Slopes of the dose-response relationships for all available neuromuscular blocking drugs appear to be essentially parallel and to approximate a log-dose/logit value of 4.75. We tested the possibility of estimating both 50% effective dose (ED(50)) and 95% effective dose (ED(95)) values from a single dose-response data point when that slope is postulated. We compared the ED(50) and ED(95) values of rocuronium and succinylcholine calculated by using traditional log-dose/logit regression analysis with the same values obtained by averaging individual estimates of potency as determined by using the Hill equation. After the induction of anesthesia (propofol/alfentanil), tracheal intubation was accomplished without the administration of neuromuscular blocking drugs. Anesthesia was maintained with nitrous oxide and propofol. The evoked electromyographic response to 0.10-Hz single stimuli was continuously recorded. After baseline stabilization, a single IV bolus of succinylcholine (0.08-0.26 mg/kg, n = 50) or rocuronium (0. 13-0.30 mg/kg, n = 40) was administered and the peak effect noted. By using log-dose/logit regression analysis, we calculated ED(50) and ED(95) values for rocuronium of 0.17 and 0.33 mg/kg and 0.14 and 0.27 mg/kg for succinylcholine. When potency was calculated from the Hill equation, the resultant ED(50) and ED(95) values did not differ by more than +/-4% from those obtained by using regression analysis. Averaging of single-dose estimates of neuromuscular potency provides a useful adjunct and reasonable alternative to conventional regression analysis.     

Repeated Doses of Rocuronium Bromide Administered to Cirrhotic and Control Patients Receiving Isoflurane: A Clinical and Pharmacokinetic Study

Background: Steroid muscle relaxants often display pharmacodynamic changes in patients with cirrhosis because of alterations in elimination processes. Rocuronium is a new steroid muscle relaxant possibly eliminated through the liver. This study was designed to compare rocuronium pharmacodynamics and pharmacokinetics in cirrhotic and healthy patients.

Methods: Rocuronium was administered to 26 cirrhotic patients and 24 control subjects anesthetized with isoflurane for an elective procedure. Patients were randomly allocated to receive an initial dose of rocuronium: 120, 180, 250, or 300 micro gram *symbol* kg sup -1. Dose-response curves were established, and ED50 was calculated. Preselected maintenance doses (75, 150, or 225 micro gram *symbol* kg sup -1) were administered at 25% recovery of twitch height to compare clinical duration of action. At the end of the procedure, relaxation was reversed in half of the patients, and the time course of recovery was compared in the two groups. Blood samples drawn during the procedure and after the last maintenance dose allowed pharmacokinetic analysis in six cirrhotic patients and six control subjects.

Results: ED50 of the initial dose was 144 micro gram *symbol* kg sup -1 in cirrhotic patients and 60 micro gram *symbol* kg sup -1 in control subjects, related to a higher initial volume of distribution (cirrhotic 78.5+/-31.7 ml *symbol* kg sup -1, control 29.8 +/-17.3 ml *symbol* kg sup -1). Time from complementary dose to 25% recovery was longer in cirrhotic patients (41.0+/-20.7 min vs. 30.2+/-9.7 min), but time course of action during maintenance was not statistically different in the two groups. In cirrhotic patients receiving five maintenance doses or more, prolongation of the duration of action with successive maintenance doses could be statistically demonstrated. Spontaneous recovery was delayed in cirrhotic patients, because of impaired elimination processes: greater volume of distribution at steady-state (264+/-92 vs. 151+/-59 ml *symbol* kg sup -1); trend toward a lower clearance (189+/-60 vs. 296 +/-169 ml *symbol* min sup -1).     

Desaturation following rapid sequence induction using succinylcholine vs. rocuronium in overweight patients

Background: Rapid sequence induction may be associated with hypoxemia. The purpose of this study was to investigate the possible difference in desaturation during rapid sequence induction in overweight patients using either succinylcholine or rocuronium. Methods: Sixty patients with a body mass index (BMI) between 25 and 30 kg/m², American Society of Anesthesiologists class I or II, undergoing general anesthesia were randomly divided into a succinylcholine group and a rocuronium group. After a 3‐min preoxygenation, patients received rapid sequence induction of general anesthesia with midazolum–fentanyl–propofol and succinylcholine (1.5 mg/kg) or rocuronium (0.9 mg/kg). Ventilation was not initiated until oxygen saturation declined to 92%. We measured the times when oxygen saturation reached 98%, 96%, 94% and 92%. Safe Apnea Time was defined as the time from administration of neuromuscular blocking drugs to oxygen saturation fell to 92%. The recovery period was defined as the time from initiation of ventilation until oxygen saturation was 97%. Arterial blood gases were taken at baseline, after preoxygenation and at 92% oxygen saturation. Results: The mean Safe Apnea Time (95% CI) was 283 (257–309) s in succinylcholine vs. 329 (303–356) s in rocuronium (P=0.01). The mean recovery period (95% CI) was 43 (39–48) s in succinylcholine vs. 36 (33–38) s in rocuronium (P=0.002). Blood gas analysis showed no difference between the two groups. Conclusions: Succinylcholine was associated with a significantly more rapid desaturation and longer recovery of oxygen saturation than rocuronium during rapid sequence induction in overweight patients.     

Pharmacodynamics of high-dose vecuronium in children during balanced anesthesia.

To compare the speed of onset, intubating conditions, duration of action, and recovery from neuromuscular blockade with vecuronium to those with succinylcholine, 40 ASA physical status 1 or 2 children (ages 2-9 yr) were studied during N2O-O2-opioid anesthesia. Each child was randomly assigned to receive a bolus dose of one of the following muscle relaxants: succinylcholine 2.0 mg/kg (n = 10), vecuronium 0.1 mg/kg (n = 10), vecuronium 0.2 mg/kg (n = 10), or vecuronium 0.4 mg/kg (n = 10). The evoked electromyogram of the abductor digiti minimi to train-of-four stimulation was monitored. We found that with succinylcholine, the time to 95% twitch depression (speed of onset, mean +/- SD), 24 +/- 7 s, was significantly less than that with each dose of vecuronium: 0.1 mg/kg, 83 +/- 21 s; 0.2 mg/kg, 58 +/- 17 s; and 0.4 mg/kg, 39 +/- 11 s, respectively (P less than 0.05). The time to laryngoscopy and intubation did not differ significantly between succinylcholine (48 +/- 10 s) and vecuronium 0.4 mg/kg (57 +/- 13 s); however, both were significantly less than than with vecuronium 0.1 and 0.2 mg/kg (P less than 0.005). The intubating conditions were excellent in 100% of patients. The duration of action was least with succinylcholine (5.7 +/- 1.5 min) and increased with increasing doses of vecuronium: 0.1 mg/kg, 23.9 +/- 5.1 min; 0.2 mg/kg, 55.2 +/- 11.6 min; and 0.4 mg/kg, 74.6 +/- 9.9 min, respectively (P less than 0.001). The recovery index was most rapid with succinylcholine (1.6 +/- 0.4 min) and was slowest with vecuronium 0.4 mg/kg (22.6 +/- 2.1 min) (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Onset of neuromuscular block at the masseter and adductor pollicis muscles following rocuronium or succinylcholine

PURPOSE: To compare the onset time of two different rocuronium doses (0.6 and 0.9 mg x kg(-1)) and succinylcholine (1.5 mg x kg(-1), preceeded by 0.06 mg x kg(-1) rocuronium) at the masseter and the adductor pollicis muscle. METHODS: In a randomized study, 60 ASA I or II adult women, 18-65 yr of age, were anesthetized with propofol and fentanyl and nitrous oxide in oxygen. Neuromuscular monitoring was performed using acceleromyography simultaneously on the masseter and adductor pollicis. Onset time was measured at both muscles using supramaximal 0.1 Hz single twitch stimulation (square-wave pulse 0.2 msec duration). RESULTS: In all patients, complete neuromuscular block occurred at the masseter and adductor pollicis muscles. Lag-time and onset time were faster at the masseter that at the adductor pollicis muscle in both rocuronium-groups (P < 0.01) and in the succinylcholine-group (P < 0.01). Furthermore, onset time was more rapid after 0.9 mg x kg(-1) rocuronium (65 +/- 7 s) than after succinylcholine (83 +/- 19 sec) at the AP (P < 0.05), but did not differ at the masseter (33 +/- 6 vs 36 +/- 7 sec). CONCLUSIONS: Following rocuronium and succinylcholine, onset time is faster at the masseter than at the adductor pollicis muscle.     

Priming with rocuronium accelerates neuromus-cular block in children: a prospective randomized study

PURPOSE: To determine the effects of a priming technique with respect to onset time and duration of action of rocuronium (1.5 x ED(95), 2.0 x ED(95)) in a pediatric patient population. METHODS: Eighty-four children, age one to seven years undergoing elective pediatric surgery, were studied in a randomized controlled trial. Neuromuscular function was assessed by accelerometry in response to single-twitch stimulation to assess onset of neuromuscular block, followed by train-of-four (TOF) stimulation at the wrist every 15 sec. Children were randomly allocated to one of four groups: Groups 1 and 3 received saline placebo, followed one minute later by a single bolus dose of rocuronium 0.45 mg.kg(-1) iv (1.5 x ED(95)) and 0.6 mg kg(-1) iv (2.0 x ED(95)), respectively. Patients in Groups 2 and 4 received an initial dose of rocuronium 0.045 mg.kg(-1) iv and 0.06 mg.kg(-1) iv, respectively, followed one minute later by rocuronium 0.405 mg.kg(-1) and 0.54 mg.kg(-1)iv, respectively. RESULTS: Rocuronium priming significantly accelerated the time to maximum rocuronium-induced neuromuscular block when compared to placebo [median (95% confidence interval)]: 122.5 (98-186) vs 92.5 (68-116) sec (1.5 x ED(95), Group 1 vs Group 2, P < 0.05) and 85 (60-142) vs 55 (48-72) sec (2.0 x ED(95), Group 3 vs Group 4, P < 0.05), respectively. Spontaneous recovery to a TOF-ratio >or= 0.9 was dose-dependent and not influenced by priming. CONCLUSION: Priming accelerated the onset of rocuronium in children. A priming interval of one minute and a cumulative dose of rocuronium 1.5 x ED(95) resulted in an onset of neuromuscular block comparable to a single dose of rocuronium (2.0 x ED(95)).     

Intramuscular Rocuronium in Infants and Children: A Multicenter Study To Evaluate Tracheal Intubating Conditions, Onset, and Duration of Action

Background: This multicenter, assessor-blinded, randomized study was done to confirm and extend a pilot study showing that intramuscular rocuronium can provide adequate tracheal intubating conditions in infants (2.5 min) and children (3 min) during halothane anesthesia.

Methods: Thirty-eight infants (age range, 3-12 months) and 38 children (age range, 1 to 5 yr) classified as American Society of Anesthesiologists physical status 1 and 2 were evaluated at four investigational sites. Anesthesia was maintained with halothane and oxygen (1% end-tidal concentration if < 2.5 yr; 0.80% end-tidal concentration if > 2.5 yr) for 5 min. One half of the patients received 0.45 mg/kg intravenous rocuronium. The others received 1 mg/kg (infants) or 1.8 mg/kg (children) of intramuscular rocuronium into the deltoid muscle. Intubating conditions and mechanomyographic responses to ulnar nerve stimulation were assessed.

Results: The conditions for tracheal intubation at 2.5 and 3 min in infants and children, respectively, were inadequate in a high percentage of patients in the intramuscular group. Nine of 16 infants and 10 of 17 children had adequate or better intubating conditions at 3.5 and 4 min, respectively, after intramuscular rocuronium. Better-than-adequate intubating conditions were achieved in 14 of 15 infants and 16 of 17 children given intravenous rocuronium. Intramuscular rocuronium provided >= 98% blockade in 7.4 +/- 3.4 min (in infants) and 8 +/- 6.3 min (in children). Twenty-five percent recovery occurred in 79 +/- 26 min (in infants) and in 86 +/- 22 min (in children).     

Effect of d-tubocurarine pretreatment on succinylcholine twitch augmentation and neuromuscular blockade

Subparalyzing doses of d-tubocurarine (dTC) given before succinylcholine decrease the duration of neuromuscular blockade. In animal preparations, they also abolish succinylcholine-induced twitch augmentation, defined as a greater-than-maximal contraction in response to a single stimulus. To determine quantitatively the effect of dTC on succinylcholine potency and on twitch augmentation in humans, 60 adult patients, ASA physical status I or II, were assigned randomly to receive either 0.05 mg/kg of dTC or saline 2 min before induction of anesthesia with fentanyl and thiopental. Train-of-four stimulation was applied every 12 s to the ulnar nerve and the force of contraction of the adductor pollicis muscle was measured. One minute after induction of anesthesia, 0.15, 0.20, 0.25, 0.35, or 0.50 mg/kg of succinylcholine was given. The height of the first twitch (T1) reached 121% +/- 6% (mean +/- SEM) of control without dTC, and was virtually abolished by dTC pretreatment (105% +/- 1%, P less than 0.01). Twitch augmentation was more noticeable with lower doses of succinylcholine, and was not observed in the response to the fourth stimulus of the train of four (T4). The potency of succinylcholine was decreased by approximately one-half in the dTC-pretreated groups. The ED50 was 0.27 +/- 0.04 mg/kg without dTC and 0.50 +/- 0.06 mg/kg with dTC (P less than 0.002). The corresponding values for ED90 were 0.51 +/- 0.07 and 1.02 +/- 0.12 mg/kg, respectively (P less than 0.02). The ED95 values were 0.63 +/- 0.09 and 1.28 +/- 0.15 mg/kg, respectively (P less than 0.02). The slopes of the regression lines did not deviate significantly from parallelism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of tracheal intubating conditions and neuromuscular blocking profiles after intubating doses of mivacurium chloride or succinylcholine in surgical outpatients

Thirty ASA physical status I or II outpatients scheduled to undergo short procedures (less than 1 hr in duration) requiring tracheal intubation received either 1.0 mg/kg succinylcholine or 0.20 mg/kg (2.5 x ED95) or 0.25 mg/kg (3 x ED95) mivacurium. A N2O/O2/narcotic anesthetic technique was utilized and the ulnar nerve was stimulated with subcutaneous electrodes placed at the wrist. Tracheal intubation was attempted in all patients either 2 min after mivacurium or 1 min after succinylcholine. Intubation conditions were not different between the succinylcholine and mivacurium groups or between the two mivacurium groups. The onset and duration of neuromuscular blockade were shorter with succinylcholine than with mivacurium. Suppression of the T1 response to 90% of baseline occurred in 0.9 min with 1.0 mg/kg succinylcholine and at 2.2 and 1.5 min respectively, with 0.20 mg/kg and 0.25 mg/kg mivacurium. Initial recovery of the T1 response occurred at 6.4 min after 1.0 mg/kg succinylcholine and 12.7 and 13.6 min respectively after 0.20 mg/kg and 0.25 mg/kg mivacurium. Subsequent to initial recovery from the intubating dose of relaxant, infusions of mivacurium or succinylcholine were administered to maintain approximately 95% block. The mean infusion rates were 6.6 micrograms.kg-1.min-1 mivacurium and 41.2 micrograms.kg-1.min-1 for succinylcholine. Spontaneous recovery from neuromuscular blockade occurred more quickly after succinylcholine than after mivacurium: the time from cessation of infusion to recovery of T1 to 95% of baseline was 6.5 min in patients given succinylcholine and 16.7 min in patients given mivacurium. When reversal was in order, residual mivacurium-induced blockade was readily antagonized by 0.045 mg/kg neostigmine.(ABSTRACT TRUNCATED AT 250 WORDS)