Neuromuscular effects of 600 μg·kg−1 of rocuronium in infants during nitrous oxide-halothane anaesthesia

Rocuronium bromide (Zemuron) is a new steroidal nondepolarizing neuromuscular blocking drug. We were interested in determining the effect of a bolus of rocuronium in infants during halothane anaesthesia as we did previously in older children. Eighteen infants (2-11 months) received a bolus of 600 μg·kg^?1, which is equal to twice the dose of rocuronium estimated to produce 95% depression of neuromuscular function (ED₉₅) in children (2-12 yr). Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s at 10-s intervals. Time (mean ± SEM, range) from administration of 600 μg·kg^?1 rocuronium to 90% (B₉₀) and 100% (B₁₀₀) neuromuscular block was 37 ± 2 (20-60) s and 64 ± 10 (20-180) s, respectively. The time to recovery of neuromuscular transmission to 10% (T₁₀) was 35.3 ± 3.0 (20.7-57.8) min and to 25% of baseline (T₂₅) was 41.9 ± 3.2 (24.3-67.7) min. The recovery index (T₂₅-T₇₅) was 26.6 ± 2.7 (11.7-44.5) min, and the time to recovery of the train-of-four ratio (T₄/T₁) ± 0.75 was 82.1 ± 6.9 (53.2-138.3) min. The plasma concentration of rocuronium when T₁ had recovered to about 30% was 654 ± 34 (417-852) ng·ml^?1 which is similar to that observed in children. Six-hundred μg·kg^?1 of rocuronium has a rapid onset of effect in infants and prolonged duration of action in infants compared to children.     

Pancuronium dose-response revisited

We were interested in determining the cumulative dose-response relationship of pancuronium in infants and children during nitrous oxide–halothane anaesthesia. Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle from supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s at 10 s intervals. Forty patients were divided into four equal groups according to age: 3–6 months, 7–12 months, 13–47 months and 48–83 months. The effective dose, ED₅₀ (mean ± SEM), of pancuronium in these age groups was 24 ± 2, 30 ± 2, 34 ± 3, 29 ± 2 μgμkg^-1, respectively; the ED₉₅ (mean ± SEM) was 45 ± 2, 52 ± 3, 62 ± 6, 62 ± 4 μgμkg^-1, respectively. The ED₉₅ of pancuronium was significantly less (P < 0.05) for infants from 3 to 6 months of age than for children from 13 to 83 months of age. Infants thus appear to be more sensitive than children to the neuromuscular blocking effects of pancuronium during halothane anaesthesia.     

Pharmacodynamic behaviour of rocuronium in the elderly

This study compared the potency and time course of action of rocuronium (ORG 9426) in elderly and young patients during nitrous oxide-opioid anaesthesia. One hundred ASA physical status I– II patients (60, âgéd 65–80 yr, and 40, âgéd 20–45 yr) were studied by measuring the force of contraction of the adductor pollicis in response to train-of-four stimulation of the ulnar nerve. After induction of anaesthesia with thiopentone and maintenance with N₂O/O₂ and fentanyl, rocuronium 120,160, 200, or 240 μg · kg ^?1 was administered to determine dose-response curves. When maximum block had been obtained,further rocuronium to a total of 300 μg · kg ^?1 was given. Additional doses of 100 μg · kg^?1 were administered when the first twitch height (T₁) had recovered to 25% control. At the end of surgery neuromuscular blockade was allowed, whenever possible, to recover spontaneously until T₁ was 90% of control before administration of neostigmine. There was no difference in the potency of rocuronium in the elderly and the younger patients. The ED₅₀ was 196 ±8 (SEE for the mean) in elderly,vs 215 ±17 iμg · kg ^{? 1} in young patients (NS). When individual cumulative dose-response curves were constructed, the ED₅₀ was 203 ± 7(SEM) and 201 ± 10 μg · kg ^{? 1} in the elderly and the young respectively (NS). However, the onset of maximum neuromuscular block was slower in the elderly 3.7 ±1.1 (SD) vs 3.1 ± 0.9 min, P < 0.05). The time to 25% T ₁ recovery was longer in the elderly (11.8 ± 8.1 vs 8.0 ± 6.5 min,P <0.05) as was the recovery index, time from 25 to 75% T₁ recovery (15.5 ± 6.2 vs 11.2 ± 4.9 min, P< 0.05). The duration of neuromuscular block after each maintenance dose was longer in the elderly (P <0.01) and increased gradually with time. It is concluded that rocuronium is an intermediate-acting neuromuscular blocking drug with a similar potency in elderly and young patients, but the onset and recovery of neuromuscular blockade are slower in the elderly.     

Smoking increases the requirement for rocuronium

Purpose

To compare the potency of rocuronium in non-smokers and smokers during general anaesthesia.

Methods

In a randomized, open clinical study, 40 patients, 17–62 yr of age, were anaesthetized with propofol, alfentanil and nitrous oxide in oxygen. After obtaining individual dose-response curves for rocuronium, bolus doses of rocuronium were given to maintain neuromuscular block at 90–99% for 60 min. Evoked adductor pollicis electromyography (EMG) was used to monitor neuromuscular block.

Results

The ED₉₅ values (± SEM) for rocuronium were 460.5 ± 28.9 and 471.5 ± 22.1 μg·kg^?1 for nonsmokers and smokers, respectively (P:NS). However, doses of rocuronium to maintain 90–99% neuromuscular block (± SEM) were 620.1 ± 46.7 and 747.4 ± 56.0 μg·kg^?1·hr^?1 for non-smokers and smokers, respectively (P = 0.0504).

Conclusion

The results may indicate increased metabolism of rocuronium in smokers rather than increased requirement of rocuronium at the receptor site.     

Neuromuscular effects of rocuronium in children during halothane anaesthesia

Rocuronium bromide, a nondepolarizing muscle relaxant has been shown to have a short onset and intermediate duration of action in adults and young children. We evaluated onset time, intubating conditions, as well as duration of action of rocuronium in children ages four to 12 years during nitrous oxide-halothane anaesthesia. Following a stable recording of train-of-four (TOF) impulses at the ulnar nerve, patients were given rocuronium 600 μg˙kg^?1 intravenously. We found that the time to 90% and 100% neuromuscular (N-M) block of the (TOF) was 51 ± 18 s and 66 ± 32 s respectively. Intubation was achieved at 94 ± 31 s and rated as good or excellent in all cases. Time to recovery of N-M transmission to 25%, 75% and 90% of control was 29 ± 8 min, 42 ± 14 min and 46 ± 16 min respectively. Heart rate increased ～12 BPM after drug injection, while the blood pressure remained unchanged. From our data we conclude that, as in other age groups, rocuronium has a rapid onset, intermediate duration of action in children 4–12 years of age, and appears devoid of significant side effects.     

Neuromuscular blocking effects of rocuronium during desflurane, isoflurane, and sevoflurane anaesthesia

Purpose

To determine the magnitude of the potentiation of rocuronium by desflurane, isoflurane and sevoflurane 1.5 MAC anaesthesia.

Methods

In a prospective, randomised, study in 80 patients, the cumulative dose-effect curves for rocuronium were determined during anaesthesia with desflurane, sevoflurane and isoflurane (with N₂O 70%, 15 min steady state) or total intravenous anaesthesia (TIVA) using propofol/fentanyl. Neuromuscular block was assessed by acceleromyography (TOF-Guard®) after train-of-four (TOF) stimulation of the ulnar nerve (2Hz every 12sec, 200 μsec duration), Rocuronium was administered in increments of 100 μg·kg^?1 until first twitch (T₁) depression > 95%.

Results

Rocuronium led to more pronounced T₁ depression with desflurane or sevoflurane anaesthesia than with TIVA. The ED₅₀ and ED₉₅ were lower during desflurane (95 ± 25 and 190 ± 80 μg·kg^?1) and sevoflurane (120 ±30 and 210 ± 40 μg·kg^?1) than with TIVA (150 ± 40 and 310 ± 90 μg·kg^?1) (P < .01), while the difference was not significant for isoflurane (130 ± 40 and 250 ± 90 μg·kg^?1). Following equi-effective dosing (T₁ > 95%) the duration to 25% T₁ recovery, recovery index (25/75), and TOF_0.70 was: 13.2 ± 1.8, 12.7 ± 3.4, and 26.9 ± 5.7 min during anaesthesia with desflurane; 15.5 ± 5.0, 11.4 ± 3.8, and 31.0 ± 6.0 min with sevoflurane; 13.9 ± 4.7, 10.7 ± 3.3, and 26.3 ± 8.9 min with isoflurane; and 13.9 ± 3.9, 11.3 ± 5.7, and 27.5 ± 8,2 min with TIVA anaesthesia (P: NS).

Conclusion

Interaction of rocuronium and volatile anaesthetics resulted in augmentation of the intensity of neuromuscular block but did not result in significant effects on duration of or recovery from the block.     

Mivacurium in infants and children

Mivacurium is the only available short-acting nondepolarizing muscle relaxant in clinical use. It is a bis-quaternary benzylisoquinolinium ester hydrolysed by plasma-cholinesterase into inactive compounds. The ED₅₀ and ED₉₅ in children are about 50 μg·kg^?1 and 90 μg·kg^?1 respectively. In infants, they have a tendency to be lower. A standard intubating dose of 0.25 mg·kg^?1 causes complete neuromuscular depression in 1.5–2 min, recovery to 5% in 6–10 min, and complete recovery in 15–20 min. The recent tendency is to use 0.3 mg·kg^?1 to obtain better intubating conditions with slight prolongation of effect. Since the recovery profile of mivacurium is independent of the dose and duration, it is most suitable for administration by continuous infusion. The infusion requirement in children is 10–16 μg·kg^?1 min^?1, which is about twice that of adults. Cutaneous flushes from histamine release are commonly seen with the larger doses of mivacurium; however, the associated hypotensive effects are minimal and counteracted by the tracheal intubation. The duration of action of mivacurium is prolonged in patients with cholinesterase deficiency. Mivacurium's neuromuscular effects can be satisfactorily antagonized by edrophonium or neostigmine.     

Nondepolarizing neuromuscular blocking drugs and train-of-four fade

The aim of this study was to examine differences in prejunctional effects of different relaxants by measuring the train-offour (TOF) fade during the onset and recovery of neuromuscular block. The relaxants studied were atracurium (225 μg · kg^?1), mivacurium (65 μg · kg^?1) rocuronium (300 μg · kg^?1)) and vecuronium (40 μg · kg^?1)). The TOF ratios were measured at approximate heights of T₁) (first response in the TOF) of 90, 75, 50, and 25%. The TOF fade (as shown by lower TOF ratios) increased with a decrease in the T₁) during onset of neuromuscular block. Although there was a slightly greater fade with atracurium and rocuronium during the onset of block, the differences among the relaxants were insignificant. It is concluded that the relative prejunctional effects of these relaxants are similar.     

The pharmacodynamics of rocuronium in pediatric patients anesthetized with halothane

The aim of this study was to determine the neuromuscular blocking potency of rocuronium (ORG 9426) in 4-to 14-year old children anesthetized with halothane. After induction of anesthesia, the ulnar nerve was stimulated with electrical impulses of 0.2 ms duration every 12 s and the force of contraction of the thumb (P) was continuously recorded. Doses of 0.12, 0.16, 0.20, and 0.24 mg·kg⁻¹ rocuronium were administered, in a randomized fashion, to 4 groups of 12 patients each. The ED₅₀, ED₉₀, and ED₉₅ of rocuronium determined from the log dose-probit regression lines were 0.18, 0.34, and 0.40 mg·kg⁻¹, respectively. To facilitate tracheal intubation, after the development of the maximal effect of the first dose, a variable second dose of rocuronium was administered to increase the total dose to 0.3 mg·kg⁻¹. If after the second dose P was greater than 10% of control, additional 0.025–0.1 mg·kg⁻¹ increments of rocuronium were administered until P became less than 10% of control. At this time the trachea was intubated. Muscular relaxation was maintained with 0.075, 0.1, or 0.125 mg·kg⁻¹ rocuronium, administered whenever P recovered to 25% of control. The clinical duration of these doses was 6.9±2.8, 6.1±0.4, and 8.1±0.6 min, respectively. On repeated administration of three 0.1 or 0.125 mg·kg⁻¹ doses, rocuronium showed little cumulative tendency. Time for spontaneous recovery of P from 25% to 75%, 8.4±0.39 min and from 10% to 90%, 16.19±0.15 min, of control, were relatively short. When at termination of anesthesia T4/T1 ratios were lower than 0.75, the residual neuromuscular block could be antagonized with 0.5 mg·kg⁻¹ edrophonium in 2 min. Rocuronium, 0.3 mg·kg⁻¹ caused a 13.5% increase of heart rate but had no effect on blood pressure. In conclusion, in 4 to 14-year-old children, rocuronium appears to have a more rapid onset and shorter duration of action than other steroid-type muscle relaxants. Presented in part at the Annual Meeting of the American Society of Anesthesiologists, San Francisco, October, 1991     

Different priming techniques,including mivacurium,accelerate the onset of rocuronium

Different priming sequences of equipotent doses of rocuronium and mivacurium on the onset of maximum neuromuscular block and intubating conditions were compared with those obtained after succinylcholine. During thiopentone-fentanylnitrous oxide anaesthesia, 70 patients were randomly assigned into seven groups. Group I received mivacurium 0.15 mg · kg^?1 as a single bolus dose. Group II received a priming dose of mivacurium 0.015 mg · kg^?1 followed three minutes later by mivacurium 0.135 mg · kg^?1. Group III received rocuronium 0.6 mg · kg^?1 as a single bolus dose, and Group IV received an initial dose of rocuronium 0.06 mg · kg^?1 followed by rocuronium 0.54 mg · kg^?1. Group V received a priming dose of mivacurium 0.015 mg · kg^?1 followed by rocuronium 0.54 mg · kg^?1. Group VI received an initial dose of rocuronium 0.06 mg · kg^?1 followed by mivacurium 0.135 mg · kg^?1. Group VII received succinykholine 1.0 mg · kg^?1. Groups I, III, and VII received a placebo injection before the administration of the neuromuscular blocking drug. Additional thiopentone 2 mg · kg^?1 iv was given 30 sec before intubation. Onset times (mean (95% confidence interval)) after priming a rocuronium block with either rocuronium (73 (57–90) sec) or mivacurium (58 (47–69) sec) were similar to those after succinykholine (54 (40–68) sec), and were shorter (P < 0.01) than that observed in other groups. Intubating conditions were not different between the groups. The duration of neuromuscular block was shortest with succinykholine. It is concluded that priming a rocuronium block with either mivacurium or rocuronium resulted in a neuromuscular block comparable to that of succinykholine in both the onset of action and intubating conditions.     

Reduced-dose rocuronium for day-case tonsillectomy in children where volatile anaesthetics are not used: operating room time saving

Objectives: Mivacurium, rocuronium, and vecuronium are neuromuscular blocking agents (NMB) commonly used in pediatric day‐case anesthesia. Mivacurium is the most appropriate NMB for short surgical procedures where NMB drugs were required but is not available in all countries. Aim: We evaluated the operating room time minimization after reduced‐dose rocuronium (0.45 mg·kg^?1) during elective day‐case tonsillectomy in children. Methods/Materials: One hundred and five children (6–9 years, ASA I/II status) scheduled for day‐case tonsillectomy were included in prospective, double blind clinical study. Children were randomly divided in three equal groups. All children were premedicated (midazolam 0.25 mg·kg^?1 orally, EMLA). Anesthesia was induced (2.5 mg·kg^?1) and maintained (0.1 mg·kg^?1·min^?2) by propofol and alfentanil (0.0015 mg·kg^?1·min^?1) and supplemented by inhalation mixture of 50% of O2/Air. Neuromuscular block was achieved by vecuronium (0.1 mg·kg^?1) (V) or rocuronium in standard (0.6 mg·kg^?1) (R) or reduced dose (0.45 mg·kg^?1) (LD). Neuromuscular transmission was monitored by acceleromyography. Time analysis of NMB drugs action was performed. Results: Time difference from the end of tonsillectomy to T90 neuromuscular block recovery was significantly shorter in LD Group (7.3 ± 0.41 min), (V = 15.9 ± 1.06, R = 16.0 ± 1.7 min) (P = 0.0011). The onset time of neuromuscular block was prolonged in LD Group (LD=3.1 ± 0.4, R = 1.3 ± 0.4, V = 2.2 ± 0.2 min) (P = 0.0039) without changing the intubating conditions. The maximum operation room time saving per each tonsillectomy was 37% in LD Group (Group V 21%, Group R 17%) (P = 0.0001). Low incidence of postoperative nausea and vomiting (PONV) 3–6% (0.4577) and good visual analog scale (VAS) score (≤2) (0.5969) were found in all study groups 12 h after surgery. Conclusions: Reduced‐dose rocuronium in addition with propofol and alfentanil in children where volatile anesthetics are not used effectively saves the operating room time during short elective surgical procedures, avoids delays in patient recovery, allows high level of acceptable intubating conditions, and improves the optimal surgical work. Low incidences of PONV as VAS score may achieved successfully.     

Tacrine does not alter the potency of succinylcholine in the rat

Purpose

Tacrine is a cholinesterase inhibitor used to manage Alzheimer’s dementia. Giveniv, it prolongs succinylcholine blockade in humans but the effects of chronic oral tacrine are not known.

Methods

Groups of adult rats were given 2.5 mg · kg^?1 tacrine (chronic groups) or 1 ml saline (control) twice daily by gavage for one, two, four or eight weeks. An additional (acute) group received 2.5 mg · kg^?1 tacrineiv. Twelve to 18 hr after the last gavage of tacrine or saline, and ~20 min afteriv tacrine, cumulative dose-response curves of succinylcholine were determined in the tibialis and soleus muscles in anaesthetized, ventilated rats during monitoring of evoked twitch response to indirect (nerve) train-of-four stimulation.

Results

The ED₅₀ and ED₉₅ of succinylcholine in control rats were (mean ± SD) 204 ± 41 and 382 ± 96 μg · kg^?1 respectively, in the tibialis muscle, and 280 ± 52 and 629 ± 168 μg · kg^?1 in the soleus muscle (P < 0.05 between muscles). In the acute and chronic tacrine groups, the mean ED₅₀ and ED₉₅ ranged from 166–197 and 277–396 μg · kg^?1, respectively, in the tibialis muscle, and 248–333 and 546–667 μg · kg^?1, in the soleus muscle. Dose responses did not differ among acute and chronic tacrine groups and the control group.

Conclusion

Chronic oral tacrine does not alter muscle response to succinylcholine in the rat. This may not apply to Alzheimer patients receiving chronic tacrine since the interaction between acute tacrine and succinylcholine in the rat differs from that in humans.     

Mivacurium infusion requirements following vecuronium: different response between adults and children

The mivacurium infusion requirements following vecuronium were evaluated in 15 adults and 15 children in an open prospective clinical study. This study was undertaken to elucidate whether potentiation of effect occurred when a mivacurium infusion was administered after vecuronium was used for the facilitation of tracheal intubation. The adult patients were anaesthetized with N₂O:O₂, propofol and fentanyl, the children with halothane (1%) N₂O:O₂ Vecuronium 100 μg · kg^?1 was administered during stimulation of the ulnar nerve with train-of-four stimuli at 0.1 Hz. The force of contraction of the adductor pollicis was recorded. Upon recovery of the twitch response from vecuronium, a mivacurium infusion was started at 4 μg · kg^?1 · min^?1, thereafter adjustments were made to maintain the first twitch of the train-of-four (T₁ at 1–10% of control. The mean (±SE) initial infusion requirements in children of mivacurium was 4.3 (0.4) μg · kg^?1 · min^?1 which increased linearly (P < 0.001) over the next 90 min to 10 μg · kg^?1 · min^?1. In adults the infusion requirement was lower than in children and remained at approximately 3 μg · kg^?1 · min^?1 over the next 75 min. At the end of the surgical procedure, the children recovered faster than the adults with no child requiring reversal. Because of prolonged recovery (>20 min), seven adults required reversal with 15–70 μg · kg^?1 neostigmine. Mivacurium infusion requirements following vecuronium are higher in children than adults. Potentiation of the effects of mivacurium were seen when vecuronium preceeded mivacurium. This potentiation of effect lasted longer in adults than in children.     

Optimum dose of neostigmine to reverse shallow neuromuscular blockade with rocuronium and cisatracurium

We examined the use of neostigmine for reversing shallow (defined as train‐of‐four ratio of 0.5), cisatracurium‐ and rocuronium‐induced neuromuscular block in 112 patients, by use of 0 μg.kg^?1, 10 μg.kg^?1, 20 μg.kg^?1 or 40 μg.kg^?1 dose of neostigmine for reversal. The times from neostigmine administration to train‐of‐four ratios of 0.7, 0.9 and 1.0 were evaluated. Analysis of variance showed that the duration of action was significantly longer after cisatracurium compared with rocuronium. The time to reach a train‐of‐four ratio of 1.0 was significantly shorter with neostigmine 40 μg.kg^?1 compared with lower neostigmine doses, and at this dose the time did not differ between cisatracurium and rocuronium. The recovery time from a train‐of‐four ratio of 0.5–1.0 did not differ between cisatracurium and rocuronium, and was significantly shortened by the administration of neostigmine. We conclude that a neostigmine dose of 40 μg.kg^?1 was the most effective at reducing recovery time after neuromuscular blockade.     

Oral clonidine does not alter vecuronium neuromuscular blockade in anaesthetized patients

Since clonidine, an α₂-agonist, inhibits the release of norepinephrine or acetylcholine which can decrease nondepolarizing muscle relaxant-induced neuromuscular blockade, the authors examined whether clonidine given as an oral preanaesthetic medication would alter the onset, duration or recovery of a vecuronium neuromuscular blockade in lightly anaesthetized patients. Thirty-eight patients (aged 20–73 yr) randomly received oral clonidine either approximately 5 μg · kg^?1 (n = 21) or none (n = 17), 90 min before arrival in the operating room. We measured acceleration of thumb contraction with ulnar nerve stimulation at the wrist to assess neuromuscular blockade. The onset time (the time from injection to decrease to 5% of baseline twitch height), duration (the time interval between injection and return of the first twitch to 25% of the baseline value), and recovery index (the time interval of the first twitch from 25% to 75% of the baseline value) of neuromuscular blockade from a single bolus of vecuronium 0.1 mg · kg^?1 iv were determined and compared between the clonidine-treated and control patients during lower abdominal or extremity surgery under epidural plus general anaesthesia with fentanyl and nitrous oxide in oxygen. No differences were noted between the control and clonidine groups in onset time (100 ± 6 sec (mean ± SE) vs 101 ± 6 sec), duration (44.5 ±2.7 min vs 42.9 ±2.7 min), or recovery index (21.6 ± 2.8 min vs 19.1 ± 1.9 min) of neuromuscular blockade from vecuronium, respectively. These results show that oral preanaesthetic medication of clonidine 5 μg · kg^?1 does not alter neuromuscular blockade induced with vecuronium 0.1 mg · kg^?1 in patients during combined epidural and fentanyl/nitrous oxide general anaesthesia.     

Effective pain relief with continuous intrapleural bupivacaine after thoracotomy in infants and children

The effect of continuous intrapleural bupivacaine on pain relief after lateral thoracotomy was studied in nine infants (≤ 15 kg body weight) and 11 children (> 15 kg body weight). An intrapleural catheter was inserted under direct vision during surgery. After extubation, the patients were transferred to the ICU where vital signs and pain scores were monitored. An intrapleural infusion of bupivacaine 0.25% with adrenaline was given at a loading dose of 0.625 mg˙kg^?1 body weight followed by a continuous infusion with a starting rate of 1.25 mg˙kg^?1˙h^?1. Haemodynamic and respiratory parameters did not differ significantly from control values throughout the study period in either group. The mean infusion rate could be reduced stepwise in both groups to 0.75 ± 0.32 mg˙kg^?1˙h^?1 and 0.73 ± 0.38 mg˙kg^?1˙h^?1 respectively. The pain score indicated a rapid onset of analgesia in both groups and remained low during the study period. The degree of analgesia amongst other factors was position dependent. The lack of any recognizable side effects or complications related to this method has been most encouraging. Only one child required a supplementary dose of an opioid. We conclude that continuous intrapleural access has proved to be a safe and suitable route for pain relief in infants and children following thoracotomy.     

Duration of action of an equipotent dose of vecuronium in infants and in children

During general anaesthesia without any volatile anaesthetic agents, ten infants and ten children received incremental doses of vecuronium to achieve a 95% neuromuscular block. Thereafter, the thenar electromyographic response was allowed to recover spontaneously. Total dose of vecuronium to establish a 95.0 ± 0.5% (mean ± SEM) neuromuscular block was 66% greater for children than for infants (73 ± 4 vs. 44 ± 4 μg·kg^?1, P < 0.0001). However, recovery index and time to complete recovery of the neuromuscular function were 88 and 89% longer, respectively, in infants than in children (P < 0.0001). These results of the effect of an equipotent dose of vecuronium in infants and in children confirm that vecuronium is a long acting neuromuscular blocking agent in infants.     

The efficacy of clonidine for reducing perioperative haemodynamic changes and volatile anaesthetic requirements in children

Background: Oral clonidine given as a premedicant in adults has been shown to reduce intraoperative inhalation anaesthetic requirements and provide perioperative haemodynamic stability. We conducted the current study to ascertain whether or not these beneficial effects of clonidine can be reproduced in children. Methods: In a prospective, randomized, double-blind, controlled clinical trial, 60 children (ASA I) aged 5–11 yr, received placebo (control), 2 μg kg^-1 clonidine, or 4 μg kg^-1 clonidine orally 105 min before induction of anaesthesia. Anaesthesia was induced with halothane, nitrous oxide in oxygen via mask and maintained with halothane and 60% nitrous oxide in oxygen. The halothane concentration was titrated to the concentration required to maintain haemodynamic stability (defined as 20% of blood pressure (BP) and heart rate (HR)) for maintenance of anaesthesia. The end-tidal concentration of halothane was monitored throughout anaesthesia. On completion of surgery, nitrous oxide and halothane were discontinued. Following confirmation of recovery from anaesthesia and muscle relaxation, the endotracheal tube was removed. Results: Higher inspired concentrations of halothane (%) were required in the control and 2 μg kg^-1 clonidine-treated groups (mean SD: 1.1 ±0.2 and 1.0±0.2, respectively) than in the 4 μg kg^-1 clonidine-treated group (0.6±0.1) for haemodynamic stability (P<0.05). Clonidine, 4 μg kg^-1, significantly reuced the intraoperative lability (coefficient of variation) of systolic and diastolic BP and HR compared with the other two regimens. Conclusion: Oral clonidine premedication at a dose of 4 μg kg^-1 provided intraoperative haemodynamic stability and reduced anaesthetic requirements in children. However, we are unable to extrapolate these observations to younger children and infants.     

Comparison of reversal with neostigmine of low‐dose rocuronium vs. reversal with sugammadex of high‐dose rocuronium for a short procedure

Some short procedures require deep neuromuscular blockade, which needs to be reversed at the end of the procedure. Forty‐four patients undergoing elective laryngeal micro‐surgery were randomly allocated into two groups: rocuronium 0.45 mg.kg^?1 with neostigmine (50 μg.kg^?1 with glycopyrrolate 10 μg.kg^?1) reversal (moderate block group) vs. rocuronium 0.90 mg.kg^?1 with sugammadex (4 mg.kg^?1) reversal (deep block group). The primary outcome was the intubating conditions during laryngoscopy secondary outcomes included recovery of neuromuscular block; conditions for tracheal intubation; satisfaction score as determined by the surgeon; onset of neuromuscular block; and postoperative sore throat. The onset of neuromuscular block was more rapid, and intubation conditions and ease of intra‐operative laryngoscopy were more favourable, and the satisfaction score was lower in the moderate block group compared with the deep block group. No difference was found in the incidence of postoperative sore throat. In laryngeal micro‐surgery, the use of rocuronium 0.9 mg.kg^?1 with sugammadex for reversal was associated with better surgical conditions and a shorter recovery time than rocuronium 0.45 mg.kg^?1 with neostigmine.     

Oral clonidine premedication reduces vomiting in children after strabismus surgery

This is a prospective randomized double-blind trial conducted to determine whether preoperative orally administered clonidine causes or potentiates postoperative vomiting in 140 children (3–12 yr) undergoing strabismus surgery. They were all inpatients and classified randomly into four groups (n = 35 each); placebo (control), diazepam 0.4 mg · kg^?1, clonidine 2 μg · kg^?1, and clonidine 4 μg · kg^?1. These agents were administered 93–112 min (mean: 100 min) before the anticipated time of induction of anaesthesia. All children received inhalational anaesthesia with halothane and nitrous oxide in oxygen.’ Muscle relaxation in all patients was obtained with vecuronium and residual neuromuscular blockade was antagonized with neostigmine and atropine before tracheal extubation. Diclofenac suppository was prescribed to prevent postoperative pain. No opioids or postoperative antiemetics were administered. All children remained in hospital for two days postoperatively. The incidence and frequency of vomiting were compared in the groups with Kruskall-Wallis Rank test. Clonidine 4 μg · kg^?1 caused a lower incidence and frequency of vomiting than did placebo and diazepam (incidence and frequency: 11% and 1,37% and 3, and 34% and 2 in clonidine 4 μg · kg^?1, placebo, and diazepam, respectively; P < 0.05 for clonidine 4 μg · kg^?1 vs placebo and diazepam). However, lowdose clonidine was ineffective. These data suggest that preanaesthetic medication with clonidine 4 μg · kg^?1 may be useful for preventing emesis following strabismus surgery. This property of clonidine indicates that it may be superior to other sedative premedicants such as diazepam and midazolam.