Objective: To determine if 1) administration of a neuroleptanalgesia sedative combination (hydromorphone-diazepam) would result in alteration of heart rate and fractional shortening parameters and 2) if administration of a neuroleptanalgesia sedative combination (hydromorphone-diazepam) prior to administration of a dissociative sedative combination (ketamine-diazepam) would blunt increases in heart rate and fractional shortening parameters previously reported with the use of dissociative-based sedation.
Design: Single blinded, randomized, crossover design.
Animals: Eleven privately owned healthy cats with normal echocardiograms.
Procedure: All cats received each of the following injections with at least one week separating each treatment: Treatment A (TA) – saline IM followed in 15 minutes by diazepam (0.2 mg/kg IM) and hydromorphone (0.2 mg/kg IM) combined in the same syringe; Treatment B (TB) – saline IM followed in 15 minutes by ketamine (6 mg/kg IM) and diazepam (0.2 mg/kg IM) combined in the same syringe; Treatment C (TC) – diazepam and hydromorphone combined in the same syringe followed in 15 minutes by ketamine and diazepam combined in the same syringe. Echocardiograms were performed using the right parasternal position 15 minutes after the second injection. Heart rate (HR) and parameters to determine fractional shortening (FS) in the short axis view were recorded in triplicate for each treatment group. An analysis of variance for repeated measures with a Fisher's LSD protected t-test was used for statistical analysis.
Results: Fractional shortening was significantly increased in each treatment group compared to baseline (p<0.05). There was a significant increase in FS between TA and TB (p<0.05), TA and TC (p<0.05), but not between TB and TC (p=0.9). Heart rate was not significantly increased between baseline and TA. There was a significant increase in HR between baseline and both TB and TC (p<0.05), but not between TB and TC (p<0.05)
Conclusion: The increase in fractional shortening induced by dissociative-based chemical restraint in normal cats is not blunted by the prior administration of a neuroleptanalgesia combination. The increase in fractional shortening following administration of the neuroleptanalgesia combination may have been due to an indirect increase in sympathetic tone (stress response).