Cardiorespiratory effects of epidurally administered ketamine or lidocaine in dogs undergoing ovariohysterectomy surgery: a comparative study

Analgesic and hemodynamic effects of ketamine in subanesthetic doses during surgical anesthesia and postoperative, are due to the action on the N-methyl-D-aspartate receptors (NMDAR). To evaluate the intraoperative cardiorespiratory effects provided by ketamine compared to lidocaine, both administered epidurally, in bitches submitted to ovariohysterectomy. Thirty-six dogs of different breeds were used in a randomized, prospective, and blinded clinical trial. Two groups were formed: G (ketamine 3 mg/kg, n=18) and G (lidocaine 4 mg/kg, n=18). Animals were premedicated with acepromazine 0.05 mg/kg intravenous. Anesthesia was induced with propofol 5 mg/kg intravenous. Anesthetic maintenance was performed with isoflurane in 100% oxygen. Every 5 min during surgery, heart rate (HR), respiratory rate (RR), esophageal temperature (°C), oxygen saturation (SPO ), end tidal carbon dioxide (ETCO ) and mean arterial pressure (MAP) were monitored. Cardiorespiratory variables during anesthesia were within normal ranges. Heart rate was significantly higher at 5 (108 ± 12 95 ± 11) and 10 (110 ± 11 97 ± 11) min in G compared to G after the start of surgery (P=0.03 and P=0.01, respectively). Mean arterial pressure was higher in G , (100 ± 23, 105 ± 35, and 103 ± 35 mmHg) in comparison with G (66 ± 7, 74 ± 10, and 67 ± 9 mmHg) at 20, 25 and 30 min (P=0.01, P=0.004, and P=0.002, respectively). Mild hypothermia at 25 (36.5 1.3C) and 30 (36.5 1.4C) min in the G was recorded. Epidural administration of ketamine provides better hemodynamic stability, compared to the use of epidural lidocaine.