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Halothane concentrations required to block the cardiovascular responses to incision (MAC CVR) in infants and children
1Department of Anesthesiology, University of Tsukuba, Ibaraki, Japan.
Insights
This study determined the halothane concentration in nitrous oxide needed to prevent cardiovascular responses to skin incision in infants and children. The minimum effective concentration was lowest in one- to three-year-olds.
Area of Science:
- Anesthesiology
- Pediatric Anesthesia
- Pharmacology
Background:
- Cardiovascular responses to surgical stimuli are critical indicators of anesthetic depth in pediatric patients.
- Determining the minimum alveolar concentration (MAC) of anesthetics required to block these responses is essential for safe anesthesia.
- Halothane and nitrous oxide (N2O) are commonly used anesthetic agents in pediatric populations.
Purpose of the Study:
- To determine the halothane concentration in N2O required to block cardiovascular responses to skin incision (MAC CVR) in infants and children.
- To compare MAC CVR values across different pediatric age groups.
Main Methods:
- Sixty-four unpremedicated infants and children (1 month to 7 years) were studied.
- The MAC CVR was assessed using the 'up and down technique' after a steady state of halothane and 60% N2O was achieved.
- Cardiovascular responses were defined as an increase in mean arterial pressure (MAP) or heart rate (HR) > 10%.
Main Results:
- The MAC CVR50 values for halothane with 60% N2O varied by age group: 1.16% (1-6 mo), 1.17% (7-12 mo), 0.95% (1-3 yr), and 1.12% (4-7 yr).
- The MAC CVR50 was significantly lower in children aged 1-3 years compared to other age groups (P < 0.05).
- Changes in MAP correlated with changes in HR and pupillary diameter.
Conclusions:
- Halothane MAC CVR values in infants and children are generally higher than those required to block motor responses (MAC).
- The lowest halothane requirement to block cardiovascular responses to skin incision was observed in children aged one to three years.
- These findings provide age-specific data for optimizing halothane anesthesia in pediatric patients.
Abstract:
The purpose of this study was to determine the halothane concentration in N2O required to block the cardiovascular responses to skin incision (MAC CVR) in infants and children. We studied 64 unpremedicated ASA 1 infants and children (one month to seven years). In each infant or child, anaesthesia was induced slowly with halothane and N2O, and an endotracheal tube was placed. The MAC CVR was assessed, after a steady state end-tidal halothane concentration had been established for ten minutes, by the "up and down technique" of Dixon. Positive responses were defined as an increase in MAP or HR > 10%. The MAC CVR50 values of halothane with 60% N2O were 1.16 +/- 0.23% at 1-6 mo, 1.17 +/- 0.18% at 7-12 mo, 0.95 +/- 0.26% at 1-3 yr, and 1.12 +/- 0.16% at 4-7 yr. The value at 1-3 years children was less than those in the other age groups (P < 0.05). The changes of MAP were correlated with changes of both HR and pupillary diameter. These results indicate that the values of MAC CVR50 of halothane in infants and children are higher than those required to block motor responses (MAC). The halothane requirement to block cardiovascular responses is lowest in the children aged one to three years.