Effects of medetomidine and midazolam alone or in combination on the metabolic and neurohormonal responses in healthy cats

Abstract

The purpose of this study was to investigate the effects of a medetomidine-midazolam combination on some neurohormonal and metabolic variables in healthy cats. Five cats were used repeatedly in each of 5 groups, which were injected intramuscularly with physiological saline solution (control), 0.5 mg/kg of midazolam, 40 microg/kg of medetomidine, 80 microg/kg of medetomidine, and 40 microg/kg of medetomidine plus 0.5 mg/kg of midazolam. Blood samples were taken 10 times over 24 h from a catheter introduced into the jugular vein. Plasma concentrations of glucose, insulin, glucagon, cortisol, nonesterified fatty acids (NEFAs), norepinephrine, and epinephrine were determined. In addition, the duration of lateral recumbency, rectal temperature, heart rate, and respiratory rate were examined. The combination of medetomidine and midazolam enhanced the duration of lateral recumbency and reduced the hyperglycemia induced by medetomidine alone. Recovery from hypoinsulinemia induced by the medetomidine-midazolam combination tended to be more rapid than when the same dose of medetomidine was used alone. The decrease in plasma norepinephrine levels induced by medetomidine alone was diminished by the addition of midazolam. Midazolam alone did not significantly change the plasma glucose, insulin, glucagon, cortisol, epinephrine, or NEFA concentration, but increased the norepinephrine concentration. This study revealed that the combination of medetomidine and midazolam produces minimal neurohormonal and metabolic changes when compared with medetomidine alone in cats.

Figure 1

Area-under-the-curve (AUC) data from 0 to 6 h for the plasma glucose concentration in 5 cats after administration of physiological saline (control), midazolam, 0.5 mg/kg (MID0.5), medetomidine, 40 or 80 μg/kg (MED40 and MED80), or a combination of these sedative agents. Means are shown along with vertical bars indicating the standard error. *significantly different from the control value at P < 0.05; **significantly different from the control at P < 0.01.

Figure 2

For the plasma insulin concentration the AUC data for 0 to 1 h are plotted.

Figure 3

For the plasma nonesterfied fatty acid (NEFA) concentration, the AUC data from 0 to 4 h are plotted. *significantly different from the control value at P < 0.05.

Figure 4

For the plasma norepinehrine concentration, the AUC data for 0 to 3 h are plotted. *significantly different from the MID0.5 value at P < 0.05. **significantly different from the MID0.5 value at P < 0.01.

Figure 5

For the plasma epinephrine concentration, the AUC data for 0 to 3 h data are plotted.