Jaw muscle tension after succinylcholine in children undergoing strabismus surgery.

The increases in tension at the masseter and adductor pollicis muscles following succinylcholine, 1 mg.kg-1, during halothane anaesthesia were measured in eight children, 3-10 yr, with strabismus. The results were compared with those obtained in a control group of general surgical patients. Supramaximal train-of-four (TOF) stimulation was applied to the ulnar nerve and the nerve to the masseter simultaneously. Jaw closure was measured by a force transducer system. In all patients, succinylcholine caused an increase in resting tone at the jaw and at the thumb. In the strabismus group, the magnitude of this increase was 55.7 +/- 23.2 g, mean +/- SD, at the jaw and 11.3 +/- 5.6 g at the thumb. This was not significantly different from the values obtained in controls, 45.3 +/- 33.4 g and 7.9 +/- 4.2 g, respectively. The duration of the phenomenon was 1-2 min in both muscles studied, and was not statistically different in the strabismus group. Time to complete neuromuscular blockade was significantly faster at the masseter, 31 +/- 6 sec--control groups; 39 +/- 11 sec--strabismus group, than at adductor pollicis, 61 +/- 34 sec--control groups; 75 +/- 28 sec--strabismus group (P less than 0.05 and 0.013 respectively). It is concluded that succinylcholine causes similar increases in jaw tension and comparable degrees of neuromuscular blockade in patients undergoing strabismus surgery as in other children.

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)

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)

Jaw muscle tension after succinychloline in children undergoing strabismus surgery.

The increases in tension at the masseter and adductor pollicis muscles following succinylcholine, 1 mg · kg-1, during halothane anaesthesia were measured in eight children, 3-10 yr, with strabismus. The results were compared with those obtained in a control group of general surgical patients. Supramaximal train-of-four (TOF) stimulation was applied to the ulnar nerve and the nerve to the masseter simultaneously. Jaw closure was measured by a force transducer system. In all patients, succinylcholine caused an increase in resting tone at the jaw and at the thumb. In the strabismus group, the magnitude of this increase was 55.7 ±23.2 g, mean ±SD, at the jaw and 11.3 ±5.6 g at the thumb. This was not significantly different from the values obtained in controls, 45.3 ±33.4 g and 7.9 ±4.2 g, respectively. The duration of the phenomenon was 1-2 min in both muscles studied, and was not statistically different in the strabismus group. Time to complete neuromuscular blockade was significantly faster at the masseter, 31 ±6 sec -control groups; 39 ±11 sec -strabismus group, than at adductor pollicis, 61 ±34 sec -control groups; 75 ±28 sec -strabismus group (P < 0.05 and 0.013 respectively). It is concluded that succinylcholine causes similar increases in jaw tension and comparable degrees of neuromuscular blockade in patients undergoing strabismus surgery as in other children.

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

This study was performed to détérmine the effects of various doses of succinylcholine on resting tension and evoked twitch height at the masséter and adductor pollicis muscles in children. Twenty patients, aged 3-10yr, 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 masséter. 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 masséter 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 < 0.05). Onset of neuromuscular blockade was faster at the masséter, 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 masséter. With succinylcholine, 1 mg · kg-1, this increase was 51.6 ± 16.8 g at the masséter and 9.1 ± 2.3 g at the adductor pollicis. Tension returned to baseline within 1-2 min. It is concluded that in children (1) succinylcholine produces dose-related changes in resting tension; (2) this effect, although quantitatively important at the masséter, is not restricted to that muscle; and (3) relatively small doses of succinylcholine are required to block neuromuscular transmission at the jaw.