Degree Of Neuromuscular Blockade Research Articles

COMPARISON OF FOUR NON-DEPOLARIZING NEUROMUSCULAR BLOCKING DRUGS IN THE SUPPRESSION OF THE OCULOCARDIAC REFLEX DURING STRABISMUS SURGERY IN CHILDREN

Eighty children (aged 2-12 yr) undergoing strabismus surgery were randomly assigned to receive tubocurarine, alcuronium, pancuronium or vecuronium during anaesthesia with thiopentone, fentanyl and nitrous oxide in oxygen. Heart rate and rhythm were recorded before and after the induction of anaesthesia and before and during traction on an extraocular muscle. End-tidal carbon dioxide concentration and the degree of neuromuscular blockade were monitored. Alcuronium seemed to give more protection against the oculocardiac reflex (defined as a 20% decrease in heart rate) than did tubocurarine, pancuronium or vecuronium.

Factors affecting leak around tracheal tubes in children.

This study determined which variables affected endotracheal tube "leak" pressures in 80 surgical patients, two weeks to 11 years of age, intubated with uncuffed tracheal tubes. We defined "leak" pressure as the inspiratory pressure needed to cause an audible escape of gas around the endotracheal tube. "Leak" pressure was measured after varying either head position, tracheal tube depth within the trachea, fresh gas flow rate, or degree of neuromuscular block. "Leak" pressure increased progressively from 16.9 +/- 1.3 cmH2O with complete patient paralysis to 30.6 +/- 1.4 cmH2O following 100 per cent recovery of neuromuscular function. Turning the head from a neutral position to one side increased "leak" pressure from 14.7 +/- 1.7 cmH2O to 24.4 +/- 2.5 cmH2O. Varying tracheal tube depth or fresh gas flow rate produced no significant change in "leak" pressure. Thus, there may be marked variability in "leak" pressure, depending on head position and degree of neuromuscular blockade. Keeping the patient fully paralyzed with the head in a neutral position provides a reliable and consistent method for measuring "leak" pressures.

Potentiation of Neuromuscular Blockade in Man Produced by Combinations of Pancuronium and Metocurine or Pancuronium and d-Tubocurarine

Simultaneous administration of combinations of pancuronium, metocurine, and d-tubocurarine (dTc) were given to A.S.A. class I-II surgical patients during N2O-narcotic-thiopental anesthesia to determine the degree of neuromuscular blockade produced. The pancuronium-metocurine and the pancuronium-dTc combinations were each significantly more potent (p < 0.05) than the additive effects of each of the individual drugs given alone. This greater than additive neuromuscular blocking effect was not seen with the metocurine-dTc combination. Despite the potentiation of neuromuscular blocking intensity by the pancuronium-metocurine and the pancuronium-dTc combination, the duration of blockade was not prolonged. Possibly, such potentiation of neuromuscular blockade might be attributed to simultaneous pre- and postjunctional receptor inhibition. Additional mechanisms might involve augmented conformational attachment to pre- and postjunctional cholinergic receptors or altered protein binding such that a greater than expected proportion of unbound drug reaches its neuromuscular site of activity. Regardless of mechanism, combining pancuronium with dTc or with metocurine can provide surgical relaxation or ideal conditions for endotracheal intubation with smaller amounts of each drug than would be anticipated if their effects were simply additive.

The absence of antagonism by naloxone during halothane/nitrous oxide anaesthesia in man.

Sixteen patients were studied to determine if naloxone could be shown to affect general anaesthesia with halothane and oxygen or nitrous oxide and oxygen with halothane. Changes in blood pressure, pulse rate, electroencephalogram and evidence of physical response were observed. The end-tidal halothane and carbon dioxide were controlled. The temperature and blood gases were held constant, as was the degree of neuromuscular blockade. Naloxone 1.2 mg was administered during general anaesthesia with either halothane in oxygen or halothane with nitrous oxide to 16 patients who were premedicated without a narcotic. No significant responses were recorded.

Pharmacokinetic studies in man with gallamine triethiodide. I. Single and multiple clinical doses.

Plasma concentrations of gallamine were determined in 6 patients undergoing anaesthesia for elective surgery receiving a single intravenous bolus dose of 2 mg/kg and in a further 11 patients requiring additional doses (0.5 to 2 mg/kg) of the relaxant. The two-compartment open model was found to characterize adequately both the single and multiple dose data. No significant differences were noted when the model-independent pharmacokinetic parameters between the two groups of patients were compared with the exception of the distribution phase half-life (t1/2 alpha) (6.70 min single vs 9.19 min multiple p less than 0.05). Mean values for the pooled data for the half-life (t1/2 beta), plasma clearance (Clp) and volume of distribution (Vd beta) were 134.58 min, 1.20 ml/min/kg and 225.28 ml/kg respectively. Evoked twitch response was monitored in each patient to assess the degree of neuromuscular blockade. In only one patient was the bolus dose sufficient to produce complete (100%) blockade, thus the degree of maximal response varied between 78 to 100% and took some 3 to 10 minutes after dose administration. The concurrently measured gallamine plasma concentrations ranged from 9.30 to 19.20 micrograms/ml. Linear regression of the offset data (20 to 80% paralysis) in 10 patients revealed a recovery rate of 0.35 to 1.33%/min. For 5 patients where offset data was available over the entire range of response (0 to 100%) the calculated mean effective plasma concentrations for gallamine at 50 and 95% paralysis (ECp50, ECp95) were found to vary between 3.43 to 10.28 micrograms/ml, and 5.66 to 23.37 micrograms/ml respectively.

Characteristics of Succinylcholine Neuromuscular Blockade in Neonates

The neuromuscular response of 10 infants to train-of-four electrical stimuli was examined during anesthesia with N2O-O2-halothane and after 1.5 mg/kg of succinylcholine IV. The ulnar nerve was stimulated electrically with a Grass S88 SIU at the wrist; the resultant force of thumb adduction was recorded. Trains-of-four, 2-Hz, supramaximal, square stimulating pulses (0.1 m/sec) were applied every 12 seconds. The maximum twitch depression following injection of succinylcholine and the train-of-four ratio were noted for the control period, at 25 percent neuromuscular transmission (T25), 50 percent neuromuscular transmission (T50), and 90 percent transmission (T90). The degree of neuromuscular blockade following succinylcholine was calculated by comparing the height of the 1st twitch of the train of stimuli to the height of the 1st twitch of the train of stimuli during anesthesia alone. During anesthesia and before administration of succinylcholine the train-of-four ratio averaged 0.92, a ratio comparable to that reported in adults during similar anesthesia. The average maximum neuromuscular blockade after 1.5 mg/kg succinylcholine was 91.1 percent. At T25 the train-of-four ratio averaged 0.72; at T50 the ratio averaged 0.79; and at T90 the ratio averaged 0.87. Using the criteria for succinylcholine phase II neuromuscular block suggested by Lee, no infant developed a phase II block with an initial dose of succinylcholine of 1.5 mg/kg.