A comparison of 3 anesthetic protocols for 24 hours of mechanical ventilation in cats.

Objective: To compare the recovery times, recovery quality, and cardiovascular (CV) effects of 3 anesthetic protocols during 24 hours of mechanical ventilation (MV) in healthy cats.

Design: Prospective, randomized, crossover study.

Setting: Research laboratory at a veterinary teaching hospital.

Animals: Six healthy intact male purpose-bred cats.

Interventions: Each cat was randomly assigned to receive 3 anesthetic protocols for 24 hours of MV; Protocol K consisted of ketamine, Protocol P, propofol; and Protocol PK, propofol plus fixed-rate low-dose ketamine. Each infusion drug dose was adjusted using a sedation scoring system. All protocols included fixed doses of fentanyl (10 μg/kg/h) and midazolam (0.5 mg/kg/h).

Measurements And Main Results: Drug doses and recovery times were recorded. Recovery quality was scored. Blood gas results, CV parameters, and frequency of bradycardia or hypotension requiring interventions were recorded. The mean d dose ± standard error of K was 81.3 ± 3.3 μg/kg/m. The median dose (95% cardiac index) of propofol (μg/kg/m) in PK was 16.0 (13.1, 19.6) and in P was 48.1 (39.3, 58.9). P necessitated significantly more propofol than PK (P < 0.05). Protocol K (35.6 ± 3.2 hours) had significantly longer times to full recovery compared to P (18.2 ± 3.2 hours). Protocol K had significantly longer times to head up, crawling, and standing compared to P and PK. Cats sedated with PK (2.33 ± 0.47) required significantly more interventions for hypotension than K (0.50 ± 0.47). Protocol P (3.2 ± 0.4) and PK (1.4 ± 0.3) required significantly more interventions for bradycardia compared to K (0.8 ± 0.3). When comparing protocol K to P and PK, significant differences in blood pressure, lactate, oxygen delivery, and oxygen consumption were noted.

Conclusions: Cats anesthetized with P had shorter times to full recovery compared to K. Cats anesthetized with K required fewer interventions for bradycardia or hypotension but had longer recovery times compared to P or PK. Protocol PK reduced the propofol dose required to maintain optimal anesthesia.