OBJECTIVES

The association between butorphanol and levomepromazine to obtain neuroleptanalgesia is still uncommon in cats, requiring more studies about the effects of these drugs on this species.

The aim of this study was to evaluate the possible electrocardiographic alterations that may occur in female cats anesthetized with propofol and pre-medicated or not with butorphanol, during an elective surgical procedure. In addition, the presence of variations in cardiac and pulmonary physiology that could be related to alterations in the myocardium electric conduction was also studied.

MATERIALS

Twenty adult healthy female cats were divided into two groups with ten animals each (G1 and G2). Both groups were pre-medicated with levomepromazine (1mg/kg/IM), but only G2 received butorphanol (0.4 mg/kg/IM). The anesthetic induction was made intravenously, using the dose of propofol required to allow orotracheal intubation. Propofol was also used to maintain the anesthesia during 60 minutes through complementary doses of 3 mg/kg, by the same route, when necessary. The electrocardiogram was recorded in DII lead in both groups. Respiratory rate, heart rate, systolic, diastolic and mean arterial blood pressure, and oxyhemoglobin saturation were also evaluated. The measurements were realized 20 minutes after the premedication (M1), immediately after the anesthesia induction (M2) and at each 20 minutes after M2 (M3, M4, M5 and M6). The numerical data were submitted to Tukey test (p<0.05).

RESULTS

After the anesthesia induction there was a reduction in the respiratory rate, since M2 in G2 and M3 in G1. It was possible to observe that propofol effects were increased by butorphanol. The oxyhemoglobin saturation was always next to the expected values for anesthetized animals (95%). After premedication all the animals presented tachycardia, which was more intense in G2. The systolic, diastolic and mean arterial blood pressure were within normal values in both groups.

Regarding to the electrocardiography, an increase in the QT interval were observed since M2 and it became more intense during the anesthesia (M3 until M5). It was more evident in G1. Among the few electrocardiographic alterations recorded, it was observed a S-T segment elevation that occurred in two animals of G1 and in three animals of G2, and also a change in T wave conformation in one animal of G2.

CONCLUSION

The results allow us to conclude that the addition of butorphanol to the premedication didn't interfere in the electrocardiographic values and in the cardiovascular and respiratory physiology. So, it's use in the premedication of cats anesthetized with propofol can be indicated.