Comparison of Different Anesthetic Regimens using Isoflurane and Propofol as Constant-Rate Infusion for Long-term Anesthesia in Dogs

The objective of the present study was to compare between three anesthetic protocols for long-term anesthesia (2 h); protocol 1: xylazine (1mg/kg)/ketamine (10mg/kg) and inhalation of isoflurane in 100% of oxygenprotocol 2: xylazine (1mg/kg)/ketamine (10mg/kg) and propofol (24mg/kg/h) by CRI, and protocol 3: propofol (5mg/kg) and propofol (12mg/kg/h) by CRI. Three clinically healthy adult mongrel dogs of both sexes were used. Food and water were withheld for 12 and 6 h before induction of anesthesia, respectively. Intravenous catheter was placed in the cephalic vein. A wash-out period of 15 days was allowed between protocols. For all protocols (1, 2, and 3), physiological parameters were recorded using a patient monitor. Depth of anesthesia and muscle relaxation were determined by recording various reflexes. Times of first limb movement, regaining swallowing reflex and extubation, sternal recumbency, and standing were recorded. Quality of recovery was also recorded. Venous blood samples were collected into EDTA-containing Vacutainer tubes immediately before anesthesia, 10min after induction with ketamine/propofol, one hour and two h of anesthesia and after complete recovery for hematological analysis by using an automated machine. Data were recorded and expressed as mean ± SD and analyzed with commercial statistical software. Results revealed slight variations among animals of the three protocols in the physiological parameters. The quality and depth of anesthesia were excellent in dogs anesthetized with isoflurane and were good in dogs during propofol infusion. The duration of deep anesthesia during propofol infusion was shorter than isoflurane, with the shortest duration in protocol 3. There were variations among animals of the three protocols in the recovery parameters. The mean scores of the recovery quality were 4.3, 4.7, and 4 for protocols 1, 2, and 3, respectively, which sited between good and excellent scores of recoveries. Slight ataxia was recorded in a dog of protocol 1. However, ataxia and urination were recorded in dogs of protocols 1 and 2. In conclusion, the effect of isoflurane and propofol on physiological parameters of dogs during long-term anesthesia was minimum and recovery was uneventful. The quality and depth of anesthesia were excellent in dogs anesthetized with isoflurane and were good in dogs during propofol infusion. The duration of deep anesthesia during propofol infusion was shorter than isoflurane, with the shortest duration in protocol 3 (12mg/kg/h). Isoflurane provides more reliable and consistent anesthetic plane plus it's not expensive as propofol. However, it requires special equipment. Propofol achieved effective anesthesia, with fast induction and less hypothermia than isoflurane administration. Apnea was recorded in two dogs after initial induction with propofol.