Ketamine–Propofol Coadministration for Induction and Infusion Maintenance in Anesthetized Dogs: Effects on Electroencephalography and Antinociception

SIMPLE SUMMARY: The coadministration of ketamine and propofol (ketofol) via constant rate infusion (CRI) was studied as a total intravenous anesthetic in dogs. The study found that ketofol induced a biphasic EEG pattern. Subanesthetic doses during induction and recovery led to high beta EEG activity, reflecting increased brain activity. During maintenance with anesthetic doses, the EEG shifted to low beta activity, merging ketamine and propofol EEG characteristics. Ketofol CRI provided robust antinociception activity and maintained a stable heart rate and blood pressure. Subanesthetic ketofol doses caused behavioral excitement, including nystagmus, tongue flicking, salivation and muscle activity. However, these effects were temporary and not a major concern. Such excitement was absent during high-dose general anesthesia. In summary, ketofol CRI showed promise as a safe and effective total intravenous anesthetic combination for dogs. It featured distinct biphasic EEG patterns, stable cardiovascular function and potent antinociception. ABSTRACT: The effects of concurrent ketamine and propofol (ketofol) constant rate infusion (CRI) were examined in six dogs. The K:P ratio was 1:2, with an initial CRI of 0.25/0.5 mg/kg/min over ten minutes, followed by a 0.5 mg/kg ketamine bolus for induction. During induction, a comprehensive EEG frequency spectrum from delta to gamma was observed, accompanied by subanesthetic-dose ketofol-induced behavioral excitation, including nystagmus, tongue flicking, salivation and active muscle activity. The dogs were maintained on three 15 min decremental doses of ketofol CRI (0.8/1.6, 0.4/0.8 and 0.2/0.4 mg/kg/min). This phase featured a significant decrease in the Patient State Index, electromyographic activity and a shift to low beta waves (SEF95: 13–18 Hz). Additionally, profound antinociception to electric stimulation and a stable heart rate and blood pressure (MBP 81.5–110 mmHg) were observed, as well as a merging of ketamine and propofol EEG characteristics during maintenance. In the recovery phase, a return to beta and gamma EEG patterns and excitement behavior occurred, accompanied by a significant reduction in antinociception, highlighting features of low doses of ketofol. This study reveals biphasic EEG dynamic changes, associated behaviors and robust antinociception and cardiovascular function, suggesting the utility of ketofol as a total intravenous anesthetic combination in dogs.