title: Tachyphylaxis and phase II block development during infusion of succinylcholine in children.
abstract: Contraction of the adductor of the thumb in response to ulnar nerve stimulation during continuous infusion of succinylcholine (SCh) was evaluated in 22 children anesthetized with halothane (1% to 1.5%) and N2O/O2. Twitch rates of 0.1 Hz were used to evaluate the force of contraction. Train-of-four stimulation (2 Hz for 2 seconds) was used to differentiate between phase I and phase II block. Tachyphylaxis to the effects of SCh occurred in 23 +/- 2 minutes in all children at a mean (+/- SE) dose of 3.0 +/- 0.4 mg/kg of SCh. In 21 of the 22 children, phase II block, as defined by a train-of-four ratio less than 50%, occurred in 29 +/- 5 minutes after 4.1 +/- 0.6 mg/kg of SCh. A mean dose of 10.3 +/- 0.6 mg/kg of SCh administered in a span of 71 +/- 5 minutes produced a mean train-of-four ratio of 12 +/- 5%. The recovery from phase II block after 10.3 +/- 0.6 mg/kg of SCh to train-of-four ratios of 50% and 75% was 16 +/- 3 minutes and 41 +/- 5 minutes, respectively. Caution should be used when more than 3 mg/kg of SCh is infused intravenously; adequate neuromuscular monitoring should be available and ample time should be given for spontaneous recovery.
mesh_terms: D000293:Adolescent; D000758:Anesthesia; D002648:Child; D002675:Child, Preschool; D006221:Halothane; D006801:Humans; D007223:Infant; D007263:Infusions, Parenteral; D007442:Intubation, Intratracheal; D013390:Succinylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D013618:Tachyphylaxis; D013997:Time Factors
chemical_list: D013390:Succinylcholine; D006221:Halothane