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Age and solubility of volatile anesthetics in blood
Insights
Blood-gas partition coefficients for volatile anesthetics increase with age, being lowest in newborns and highest in adults. This age-related solubility impacts anesthetic partial pressure rise in children.
Area of Science:
- Anesthesiology
- Pharmacokinetics
- Pediatric Medicine
Background:
- The rate of rise of alveolar anesthetic partial pressure differs between children and adults.
- This difference may be partly due to age-related changes in volatile anesthetic solubility in blood.
Purpose of the Study:
- To investigate the effect of age on the blood-gas partition coefficients of common volatile anesthetics.
- To determine if age-related solubility differences explain faster anesthetic induction in children.
Main Methods:
- Measured blood-gas partition coefficients for isoflurane, enflurane, halothane, and methoxyflurane.
- Studied four groups: newborns, children (3-7 years), adults (20-40 years), and elderly adults (75-85 years).
Main Results:
- Blood-gas partition coefficients were lowest in newborns and highest in adults.
- Coefficients in children were intermediate, significantly different from newborns and adults, but not elderly adults.
- Anesthetic solubility correlated with serum concentrations of albumin, triglycerides, cholesterol, and globulins.
Conclusions:
- Age significantly influences blood-gas partition coefficients of volatile anesthetics.
- Lower solubility in children contributes to the more rapid increase in alveolar anesthetic partial pressure in this age group.
Abstract:
The more rapid rate of rise of alveolar anesthetic partial pressure in children compared with adults may be explained in part by an increasing solubility of volatile anesthetics in blood with age. To investigate this possibility, the authors measured the blood-gas partition coefficients of isoflurane, enflurane, halothane, and methoxyflurane in four groups of fasting subjects: 10 full-term newborns (at delivery), 11 children (3-7 years old), 11 adults (20-40 years old), and 10 elderly adults (75-85 years old). The blood-gas partition coefficients were greatest in adults: isoflurane 1.46, enflurane 2.07, halothane 2.65, and methoxyflurane 16.0; and least in newborns: 1.19, 1.78, 2.14, 13.3, respectively. The blood-gas partition coefficients in children (1.28, 1.78, 2.39, 15.0, respectively), which were intermediate between those in newborns (P less than 0.005) and those in adults (P less than 0.005), were not significantly different from those in elderly adults (1.29, 1.79, 2.41, 15.0, respectively). The blood-gas partition coefficients of both isoflurane and enflurane correlated directly with the serum albumin and triglyceride concentrations; that of halothane correlated directly with the serum cholesterol, albumin, triglyceride, and globulin concentrations; and that of methoxyflurane correlated directly with the serum cholesterol, albumin, and globulin concentrations. The authors conclude that age significantly affects blood-gas partition coefficients, and the lower blood-gas partition coefficients in children explain in part the more rapid rise of alveolar anesthetic partial pressure in this age group.