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Does age or pseudocholinesterase activity predict mivacurium infusion rate in children?
D A Markakis1, P S Hart, M Lau
1Department of Anesthesia, University of California, San Francisco, USA.
Insights
Mivacurium infusion rates are approximately twice as large in children compared to adults. Pseudocholinesterase activity influences mivacurium infusion rates in children, particularly at lower target twitch depression levels.
Area of Science:
- Pharmacology
- Anesthesiology
- Pediatric Medicine
Background:
- Previous studies suggest higher mivacurium infusion rates in children than adults.
- A limited relationship between pseudocholinesterase activity and mivacurium infusion rate in children has been noted.
Purpose of the Study:
- To investigate if mivacurium infusion rates are higher in children than adults.
- To determine the influence of pseudocholinesterase activity on mivacurium infusion rates in pediatric patients.
Main Methods:
- Comparing mivacurium infusion rates for 50% and 90% twitch depression (IR50, IR90) in 20 children (1-9 yr) and 14 adults (18-58 yr).
- Patients received N2O and isoflurane (0.75 MAC).
- Hill equation and linear regression were used to analyze data; analysis of covariance compared groups.
Main Results:
- Mivacurium infusion rates were approximately double in children compared to adults.
- In children, IR50 showed a relationship with pseudocholinesterase activity (r2 = 0.22, P = 0.038), but IR90 did not (r2 = 0.11, P = 0.21).
Conclusions:
- Mivacurium infusion rates are indeed higher in pediatric patients than in adults.
- Pseudocholinesterase activity is a significant factor influencing mivacurium infusion rates in children.
Abstract:
Previous studies have suggested that the mivacurium infusion rate to maintain target twitch depression is greater in children than in adults, and that there is only a limited relationship between pseudocholinesterase activity and mivacurium infusion rate in children. We therefore examined whether mivacurium infusion rates are larger in children than in adults, and whether pseudocholinesterase activity influences mivacurium infusion rate in children. In 20 children aged 1-9 yr, mechanical twitch response to ulnar nerve train-of-four stimulation was measured; concurrent data were obtained in 14 adults aged 18-58 yr. All patients were anesthetized with N2O and isoflurane, 0.75 minimum alveolar anesthetic concentration (MAC) (age-adjusted). Mivacurium was infused at constant rates for > 15 min targeting 50% and 90% twitch depression. The Hill equation was fit to the resulting values for twitch depression versus mivacurium infusion rate to predict infusion rates producing 50% and 90% twitch depression (IR50 and IR90, respectively). The relationship of IR50 and IR90 to pseudocholinesterase activity was determined by linear regression; values for children and adults were compared by analysis of covariance. For children, IR50 (r2 = 0.22, P = 0.038) but not IR90 (r2 = 0.11 P = 0.21) was related to pseudocholinesterase activity. Infusion rates were approximately twice as large in children as in adults. We confirm that mivacurium infusion rates are larger in children than in adults and demonstrate a relationship between pseudocholinesterase activity and infusion rates.