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Vecuronium kinetics and dynamics in anesthetized infants and children
Insights
Vecuronium pharmacokinetics and dynamics differ between infants and children. Infants have a larger volume of distribution and longer mean residence time, affecting drug response during anesthesia.
Area of Science:
- Pharmacology
- Anesthesiology
- Pediatric Medicine
Background:
- Vecuronium is a neuromuscular blocking agent used in anesthesia.
- Understanding its pharmacokinetic and dynamic properties in pediatric populations is crucial for safe and effective use.
Purpose of the Study:
- To determine the pharmacokinetics and pharmacodynamics of vecuronium in infants and children.
- To compare these parameters between the two age groups under specific anesthetic conditions.
Main Methods:
- Intravenous infusion of vecuronium (2.5 micrograms/kg/min) in infants (3-11 months) and children (1-5 years) under nitrous oxide and halothane anesthesia.
- Monitoring of adductor pollicis muscle twitch tension and measurement of vecuronium plasma concentrations via mass spectrometry.
- Analysis using linear regression, noncompartmental techniques, and effect compartment modeling.
Main Results:
- Infants exhibited a larger volume of distribution (Vdss) and longer mean residence time compared to children.
- Plasma clearance (Cl) was similar between infants and children.
- The steady-state concentration for 50% twitch depression (Cpss50) was lower in infants, indicating greater sensitivity.
Conclusions:
- Age-related differences in vecuronium Vdss, mean residence time, and Cpss50 exist between infants and children.
- These findings are comparable to those observed with d-tubocurarine, suggesting similar age-related pharmacokinetic/dynamic alterations for neuromuscular blockers.
Abstract:
Vecuronium kinetics and dynamics were determined in five infants (3 to 11 months old) and five children (1 to 5 years old) during anesthesia with 70% nitrous oxide and 0.9 MAC halothane. Vecuronium was infused intravenously at a rate of 2.5 micrograms/kg/min while twitch tension of the adductor pollicis muscle was recorded and venous blood samples were drawn for determination of vecuronium concentrations by mass spectrometry. The elimination t1/2 was determined by linear regression of the log postdistribution concentration-time data; these values and noncompartmental techniques were used to calculate total plasma clearance (Cl), volume of distribution at steady state (Vdss), and mean residence time. The steady-state plasma concentration resulting in 50% depression of twitch tension (Cpss50) was determined by an effect compartment and a sigmoid concentration vs. paralysis model. Vdss was larger in infants (357 +/- 70 ml/kg; mean +/- SD) than in children (204 +/- 116 ml/kg), and Cl was of the same order for infants and children (5.6 +/- 1.0 and 5.9 +/- 2.4 ml/kg/min). Mean residence time was longer in infants (66.3 +/- 22.9 minutes) than in children (34.3 +/- 8.0 minutes). Cpss50 was lower in infants (57 +/- 18 ng/ml) than in children (110 +/- 28 ng/ml). The quantity of vecuronium in the body at steady state at 50% depression of twitch tension (Vdss X Cpss50) was similar in infants and children (21.2 +/- 9.9 and 19.0 +/- 3.3 micrograms/kg). During comparable nitrous oxide-halothane anesthesia, age-related changes in Vdss, Cl, and Cpss50 were much like those found for d-tubocurarine.(ABSTRACT TRUNCATED AT 250 WORDS)