Tissue solubility of four volatile anesthetics in fresh and frozen tissue specimens from swine.

OBJECTIVE

To determine tissue solubilities of desflurane, sevoflurane, enflurane, and halothane in swine and to evaluate the effects of freezing specimens on tissue solubility,

SAMPLE POPULATION

Arterial blood samples and specimens of brain, heart, liver, kidney, muscle, and subcutaneous fat from 5 healthy female adult Chinese Meishan pigs.

PROCEDURE

Each tissue specimen was divided into 2 parts. One part was used to measure tissue-gas partition coefficients immediately after collection. The other part was frozen at -20 C for 6 days prior to determination of tissue-gas partition coefficients. Tissue-gas and blood-gas partition coefficients were measured by use of gas chromatography, and tissue-blood partition coefficients were calculated. Regression analysis was performed to determine whether fat-gas partition coefficients were correlated with lean tissue-gas partition coefficients.

RESULTS

Tissue-gas and blood-gas partition coefficients of halothane were greater than those of enflurane followed by coefficients of sevoflurane and desflurane. However, the order of anesthetic agents with the greatest to smallest tissue-blood partition coefficients was sevoflurane, halothane, enflurane, and desflurane. Muscle-gas partition coefficients of sevoflurane and enflurane, liver-gas partition coefficients of desflurane and halothane, and the kidney-gas partition coefficient of enflurane were significantly greater in frozen specimens, compared with fresh specimens. Lean tissue-gas partition coefficients of all 4 volatile anesthetics correlated directly with fat-gas partition coefficients.

CONCLUSIONS AND CLINICAL RELEVANCE

The fat content of lean tissue is an important factor in determining the tissue solubility of volatile anesthetics. Freezing specimens before determination of tissue-gas partition coefficients may result in a false increase in tissue solubility.