Objective To evaluate and compare the cardiopulmonary effects of induction of anesthesia with isoflurane (Iso), ketamine-diazepam (KD), or propofol-diazepam (PD) in hypovolemic dogs.
Study design Prospective randomized cross-over trial.
Animals Six healthy intact, mixed breed, female dogs weighing 20.7 ± 4.2 kg and aged 22 ± 2 months.
Methods Dogs had 30 mL kg−1 of blood removed at a rate of 1.5 mL kg−1 minute−1 under isoflurane anesthesia. Following a 30-minute recovery period, anesthesia was reinduced. Dogs were assigned to one of three treatments: isoflurane via facemask using 0.5% incremental increases in the delivered concentration every 30 seconds, 1.25 mg kg−1 ketamine and 0.0625 mg kg−1 diazepam intravenously (IV) with doses repeated every 30 seconds as required, and 2 mg kg−1 propofol and 0.2 mg kg−1 diazepam IV followed by 1 mg kg−1 propofol increments IV every 30 seconds as required. Following endotracheal intubation all dogs received 1.7% end-tidal isoflurane in oxygen. Cardiopulmonary variables were recorded at baseline (before induction) and at 5 or 10 minute intervals following endotracheal intubation.
Results Induction time was longer in Iso (4.98 ± 0.47 minutes) compared to KD (3.10 ± 0.47 minutes) or PD (3.22 ± 0.45 minutes). To produce anesthesia, KD received 4.9 ± 2.3 mg kg−1 ketamine and 0.24 ± 0.1 mg kg−1 diazepam, while PD received 2.2 ± 0.4 mg kg−1 propofol and 0.2 mg kg−1 diazepam. End-tidal isoflurane concentration immediately following intubation was 1.7 ± 0.4% in Iso. Arterial blood pressure and heart rate were significantly higher in KD and PD compared to Iso and in KD compared to PD. Arterial carbon dioxide partial pressure was significantly higher in PD compared to KD and Iso immediately after induction.
Conclusions and clinical relevance In hypovolemic dogs, KD or PD, as used in this study to induce anesthesia, resulted in less hemodynamic depression compared to isoflurane.