The potency of pancuronium at the adductor pollicis and diaphragm in infants and children

[Pharmacodynamics and safety of mivacurium in infants and children under halothane-nitrous oxide anesthesia]

OBJECTIVES

To determine pharmacodynamic effects and safety of mivacurium in paediatric patients.

STUDY DESIGN

Multicentric, prospective, open, non-randomized study.

PATIENTS

Forty-eight three-month-old to eight-year-old physical class ASA I or II children.

METHOD

Anaesthesia was induced and maintained with halothane and nitrous oxide. Tracheal intubation was performed without a neuromuscular blocking agent. Neuromuscular blockade was measured with a strain force transducer after train-of-four stimulation of the ulnar nerve at the wrist every ten seconds. A single bolus dose of mivacurium (0.2 mg.kg-1) was injected during 15 seconds in patients allocated into three groups. Group 1: three to 12-month-old infants (n = 15), group 2: one- to three-year-old children (n = 16) and group 3: three- to eight-year-old children (n = 17). Onset and recovery parameters were measured in each patient. Heart rate and noninvasive arterial blood pressure were recorded every minute for five minutes after mivacurium injection.

RESULTS

Following halothane administration for 29 and 32 min, and a FEThalothane = 1 vol%, mivacurium (0.2 mg.kg-1) determined a 100% neuromusmcular blockade in all patients. The onset time was 71 +/- 34 s (mean +/- SD) in all patients and did not differ between groups. Time to 25% and 95% recovery of the first twitch and recovery index for all the patients were 12 +/- 3 min, 19 +/- 5 min and 4 +/- 2 min respectively and did not differ between groups. No prolonged paralysis was observed. No significant changes of HR and BP occurred.

CONCLUSIONS

Following 0.2 mg.kg-1 of mivacurium in patients aged between three months to eight years, a complete blockade occurs with a rapid onset time and a short duration of action, without significant cardiovascular effect.

Intubation in children after 0.3 mg/kg of mivacurium

STUDY OBJECTIVE

To distinguish among potential predictors of early, easy intubation in children, including apnea, neuromuscular block at two sites, and time, after administration of 0.3 mg/kg of mivacurium.

DESIGN

Prospective, randomized study.

SETTING

Operating rooms of Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania.

PATIENTS

60 ASA physical status I and II children aged 2 through 7 years, scheduled for elective surgical procedures requiring endotracheal intubation.

INTERVENTIONS AND MEASUREMENTS

After premedication with midazolam, general anesthesia was induced with halothane and nitrous oxide, and patients were randomly assigned to one of four groups. Mivacurium 0.3 mg/kg was given and tracheal intubation was begun 45 seconds after its injection, or when apnea, block of the orbicularis oculi, (OO) or block of the adductor pollicis (AP) was noted. Intubation conditions were evaluated by an experienced endoscopist.

MAIN RESULTS

The first clinical event after administration of mivacurium 0.3 mg/kg was apnea at 43 seconds (median) (average 48 seconds, SEM 2 seconds) after injection. The difference in the time at which neuromuscular block occurred at the AP (median 75 seconds) (average 77 seconds, SEM 2 seconds) and the OO (median 63 seconds) (average 68 seconds, SEM 4 seconds) was statistically, but not clinically, significantly different. All nine intubations that were begun at least 90 seconds after administration of mivacurium resulted in good or excellent intubation conditions, as did 30 of the 51 intubations started earlier.

CONCLUSIONS

In children, there is no advantage to monitoring neuromuscular function at the OO rather than the AP. After administration of 0.3 mg/kg of mivacurium, a 90-second interval before the start of intubation was a better predictor of good intubation conditions during halothane anesthesia (1% inspired) than were changes in evoked neuromuscular function.

Monitoring orbicularis oculi predicts good intubating conditions after vecuronium in children

PURPOSE

The aim of the study was to compare visual estimation of onset of neuromuscular blockade at both the adductor pollicis (AP) and the orbicularis oculi (OO) in children and to determine if monitoring the OO could predict good intubating conditions during vecuronium-induced neuromuscular blockade.

METHODS

Thirty ASAI--II children (1.5-9 yr) were studied. Anaesthesia was induced with 6-8 mg.kg-1 thiopentone. The ulnar nerve at the wrist and the temporal branch of the facial nerve were stimulated every 10 sec using train-of-four (TOF) stimuli. Vecuronium, 0.15 mg.kg-1, was administered as a bolus. The responses at both the OO and the AP were evaluated visually. Patients were randomly divided into two groups. In the AP group (n = 15), the trachea was intubated when the AP was completely blocked. In the OO group (n = 15), intubation was performed when the OO was completely blocked. Intubating conditions were scored on a scale of 1 to 4.

RESULTS

All the patients had complete blockade at both the orbicularis oculi and the adductor pollicis. In the two group, time from injection of vecuronium to complete neuromuscular blockade was shorter at the orbicularis oculi than at the adductor pollicis, 1.5 +/- 0.5 min vs 2.3 +/- 0.7 min, respectively, (P < 0.05; mean +/- SD) in the AP group, 1.7 +/- 0.3 min vs 2.3 +/- 0.8 min, respectively in the OO group (P < 0.05). Intubating conditions were excellent in all patient except one, where it was rated as good. They did not differ between groups.

CONCLUSION

Following administration of 0.15 mg.kg-1 vecuronium in children, monitoring of the OO can detect good intubating conditions 0.7 min earlier than with monitoring of the AP.

Assessment of neuromuscular block at the thumb and great toe using accelography in infants

We assessed neuromuscular block at the thumb and great toe using accelography after the administration of vecuronium in infants. Train-of-four stimuli were simultaneously applied to the ulnar and tibial nerves using cutaneous electrodes. Anaesthesia was maintained with nitrous oxide (66%) in oxygen and sevoflurane (1%). Vecuronium 0.1 mg.kg-1 was used for paralysis and reversed with intravenous neostigmine 0.04 mg.kg-1 with atropine 0.02 mg.kg-1 when the train-of-four ratio on the right great toe returned to 25%. The mean (SD) times from initial administration of vecuronium to completion of maximal block on the thumb and great toe were 78 (21.1) s and 75 (14.3) s, respectively (p > 0.05). The times from maximal block to 25% recovery of twitch height at the thumb and great toe were 46 (9.1) min and 45 (9.0) min, respectively. The reversal time from 25% to 75% of the train-of-four ratio after the administration of neostigmine was 136 (49.1) s. We conclude that neuromuscular monitoring of the great toe in infants may be a suitable alternative when the thumb is inaccessible.

Comparison of train-of-four and posttetanic response as guides for endotracheal intubation in children

STUDY OBJECTIVE

To evaluate and compare the predictive values of the absence of train-of-four (TOF) or posttetanic response as guides for endotracheal intubation in children.

DESIGN

Prospective controlled study in children.

SETTING

Induction of anesthesia and endotracheal intubation at a university-affiliated hospital.

PATIENTS

Thirty pediatric patients age 1 to 10 years, ASA physical status I, who were undergoing elective surgery were divided into two equal groups.

INTERVENTIONS

Anesthesia was induced with halothane and maintained at 1% inspired concentration. Fifteen children were stimulated with the TOF (2 Hz for 2 seconds) technique and 15 with the twitch-tetanus-twitch sequence. All the patients received atracurium 0.4 mg/kg. Upon abolishment of the TOF or tetanus-twitch sequence, endotracheal intubation was performed and the conditions for intubation were evaluated.

MEASUREMENTS AND MAIN RESULTS

In the group of patients stimulated by the TOF technique, the neuromuscular response was ablated in 1.7 +/- 0.1 minutes, a significantly shorter time than in those stimulated by the tetanus-twitch sequence (4.0 +/- 0.4 minutes; p less than 0.0001). Conditions for intubation did not differ between the two groups.

CONCLUSIONS

Good intubating conditions can generally be counted on when the TOF has disappeared; additional waiting for the disappearance of posttetanic response is unnecessary. The observation that the disappearance of the tetanus-twitch sequence is a good indicator of deep neuromuscular blockade during recovery from atracurium in children cannot be extrapolated to the induction period.

Dose-response characteristics of pancuronium in neonates, infants and children

This paper presents pharmacodynamic data for pancuronium in neonates, infants, children and adolescents during N2O-O2-fentanyl anaesthesia. Neuromuscular block (NMB) was evaluated by the adductor pollicis electromyogram. Dose-response curves of pancuronium were parallel in all age-groups. ED95 was greatest in children and least in infants (93 vs. 66 micrograms/kg, P less than 0.05). The rate of spontaneous recovery following 95% NMB was comparable in all age-groups, as was the maintenance requirement of pancuronium when related to ED-values. The hourly requirement to maintain NMB greater than 85% was 60-68% of the individual ED95 dose. When administered on this basis, pancuronium is an equally long-acting neuromuscular blocking agent in patients of all ages.

Neuromuscular blocking agents in paediatric patients: influence of age on the response

This paper reviews the studies in which neuromuscular blocking drugs were compared in at least two different age groups of patients. Most recent studies have lead to a uniform concept of the variation of the effect of these drugs in different age groups. In general, the dose of a nondepolarizing agent required to produce a particular degree of relaxation is similar in neonates (less than one month), infants (one to twelve months) and adolescents (more than thirteen years). However, in children from three to ten years the dose is significantly greater. The maximal effect is reached more quickly in neonates and infants than in the older children and adolescents. These results can be explained by changes in sensitivity, distribution volume and muscle mass. The duration of effect of a nondepolarizing agent is significantly altered by age only in the case of vecuronium, which has a prolonged action in neonates and infants. Suxamethonium remains as the agent with the most rapid onset.

Dose-related effects of succinylcholine on the adductor pollicis and masseter muscles in children

This study was performed to determine the effects of various doses of succinylcholine on resting tension and evoked twitch height at the masseter and adductor pollicis muscles in children. Twenty patients, aged 3-10 yr, ASA physical status I or II, were randomly assigned to receive succinylcholine 0.15, 0.25, 0.50 or 1.00 mg.kg-1, during halothane-nitrous oxide anaesthesia. Supramaximal train-of-four stimulation was applied simultaneously to the ulnar nerve and the nerve to the masseter. Transducers recorded force at the jaw and the thumb. Maximum blockade of the first twitch (T1) and maximum resting tension change were measured. Potency of succinylcholine at the two muscles was estimated by linear regression of the logit transformation of T1 versus log dose. The relationship between resting tension change and log dose was established by linear regression. The masseter muscle was more sensitive to succinylcholine than the adductor pollicis with an ED95 of 0.28 +/- 0.02 (mean +/- SEM) vs 0.44 +/- 0.05 mg.kg-1 (P less than 0.05). Onset of neuromuscular blockade was faster at the masseter, and recovery occurred simultaneously in both muscles. A dose-related increase in resting tension was observed in both muscles, but its magnitude was five times greater at the masseter. With succinylcholine, 1 mg.kg-1, this increase was 51.6 +/- 16.8 g at the masseter and 9.1 +/- 2.3 g at the adductor pollicis. Tension returned to baseline within 1-2 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Potency of atracurium on masseter and adductor pollicis muscles in children

The sensitivity of the masseter to atracurium was measured in ten children aged 3-10 yr undergoing elective surgery, and compared with that of the adductor pollicis. During nitrous oxide-halothane anaesthesia and mechanical ventilation, supramaximal nerve stimulation was applied to the ulnar nerve at the elbow and to the nerve to the masseter, at a point inferior to the zygomatic arch, anterior to the mandibular condyle. Jaw closure was measured by a force displacement transducer system attached to an oral airway and connected to a metal frame fixed to the operating table 10 cm caudad to the chin. Cumulative dose-response curves for atracurium were obtained by the injection of doses followed by an infusion to compensate for elimination. The mean ED50s and ED95s were similar at the masseter and the adductor pollicis. At the masseter, these were 0.150 +/- 0.013, mean +/- SEM, mg.kg-1 and 0.254 +/- 0.021 mg.kg-1, respectively. At the adductor pollicis, corresponding values were 0.145 +/- 0.009 mg.kg-1, and 0.259 +/- 0.016 mg.kg-1. However, this relationship was not constant in every patient, and in some patients the masseter was much more sensitive than the adductor pollicis. The time from injection of the first dose of atracurium to maximum blockade was 2.5 +/- 0.2 min at the masseter and 3.2 +/- 0.2 min at the adductor pollicis (P less than 0.05). It is concluded that when atracurium is administered to paediatric patients, neuromuscular blockade is usually of the same intensity at each muscle but occurs sooner at the masseter than at the adductor pollicis.(ABSTRACT TRUNCATED AT 250 WORDS)