Tissue composition and halothane solubility in the horse.

This research study examined the relationship between the halothane muscle/gas partition coefficients in horses and fat content of muscle samples and plasma triglyceride concentration. A significant correlation was found in both cases.

Research Objective and Methods

• The main goal of this research was to investigate the solubility of halothane – a potent inhalation anesthetic – in different muscles and blood of horses. Halothane muscle/gas partition coefficients were determined for 26 samples taken from eight different muscles across four horses.
• In addition, the researchers also assessed the blood/gas partition coefficients in 24 horses, and examined whether these coefficients were influenced by variations in plasma triglyceride concentrations, total and free cholesterol concentrations, and packed cell volume.

Key Findings

• The significant outcome of the study was the discovery of a relationship between the halothane muscle/gas partition coefficients and the fat content in the muscle samples of horses. Specifically, the regression coefficient was found to be 1.913 (with a Standard Error of the Mean (SEM) of 0.109) per percent ether-extractable fat content, indicating a strong positive association.
• Similarly, the blood/gas partition coefficients also showed a significant dependency on plasma triglyceride concentrations, with a regression coefficient of 0.00084 (with a SEM of 0.00033) per milligram per deciliter (mg dl-1).
• Conversely, the relationship between the blood/gas partition coefficients and plasma free and total cholesterol concentrations was found to be positive but statistically insignificant.
• In a multiple regression analysis, the correlation between packed cell volume and the blood/gas partition was found to be borderline negative, with a regression coefficient of -0.01 (SEM 0.005) per percent packed cell volume (p.c.v.).

Implications

• The findings of the research imply that fat content in muscles and plasma triglyceride concentrations can impact the solubility of halothane, which could potentially affect the effectiveness of this anesthetic in a clinical setting. This is significant as it provides veterinarians with valuable knowledge for achieving optimal anesthesia in horses, particularly those with higher levels of fat or altered plasma triglyceride concentrations.
• Furthermore, the indication of a negative relationship between packed cell volume and the blood/gas partition coefficient (although borderline) could suggest that hematocrit levels could also play a role in halothane solubility. However, more research is needed to confirm and further investigate this relationship.