Influence of preinduction methoxamine, lactated Ringer solution, or hypertonic saline solution infusion or postinduction dobutamine infusion on anesthetic-induced hypotension in horses.

This study examines the effects of various treatments on hypotension, often induced by anesthesia, in horses. The researchers conducted trials using different treatments and found that the administration of certain solutions or drugs can actually prevent or reduce hypotension during halothane administration.

Overview of the Research

• The researchers anesthetized six horses with acepromazine, guaifenesin, thiamylal, and halothane in oxygen. These four agents are commonly used for inducing general anesthesia in veterinary medicine.
• The horses underwent five treatments in a randomized sequence: no treatment (control), administration of methoxamine, lactated Ringer solution, 7.5% hypertonic saline solution, or constant infusion of dobutamine during anesthesia. All treatments were administered intravenously (IV).
• Various cardiovascular responses including heart rate, ECG, blood pressure, central venous pressure, cardiac output, blood gas analysis, packed cell volume (PCV), and plasma total protein concentration were measured throughout the study.

Key Findings

• After administration of lactated Ringer solution, hypertonic saline solution, or dobutamine, the horses showed an increase in blood pressure during halothane administration compared to the control group. This suggests these treatments can prevent or reduce anesthetic-induced hypotension.
• The improved blood pressure response after hypertonic saline treatment and dobutamine infusion was related to an increase in cardiac output, indicating these treatments can improve heart function under anesthesia.
• No other statistically significant differences were observed in other cardiopulmonary responses among the treatments during anesthesia, implying these treatments have minimal impact on other cardiovascular parameters.
• The study also found that dobutamine infusion increased the packed cell volume (PCV), which is a measure of the volume percentage of red blood cells in blood, while the administration of hypertonic saline or lactated Ringer solution reduced plasma total protein concentration. This indicates these treatments might have some effects on blood components under the influence of anesthesia.