Comparison of Isoflurane and Propofol Maintenance Anesthesia and Evaluation of Cerebrospinal Fluid Lactate and Plasma Lactate Concentrations for Dogs with Intracranial Disease Undergoing Magnetic Resonance Imaging

This thesis contains two studies. The first study consisted of a prospective, randomized, clinical trial involving twenty-five client-owned dogs with intracranial disease. Each dog was randomly assigned to receive propofol or isoflurane for maintenance of anesthesia, without premedication. All dogs received propofol IV to effect, were intubated and mechanically ventilated (end-tidal carbon dioxide [ETCO2] 30-35 mmHg). Temperature and cardiac output were measured pre- and post-magnetic resonance imaging (MRI). Scores for mentation, neurological status, maintenance, and recovery were obtained. Pulse oximetry, end tidal gases, arterial blood pressure (AP), heart rate (HR) and requirements for dopamine administration to maintain mean AP > 60 mmHg were recorded throughout anesthesia. Cardiac index was higher, while HR was lower, with propofol in dogs younger than 5 years. Dogs receiving isoflurane were 14.7 times more likely to require dopamine. Sedation and maintenance scores and temperature were not different. Mean and diastolic AP were higher in the propofol group. Recovery scores were better with propofol. Change in neurological score from pre- to post-anesthesia was not different between treatments. In the second study, blood and CSF were collected from 11 dogs with intracranial disease after MRI (Group ID-MRI), in 10 healthy dogs post-MRI (Group H-MRI), and in 39 healthy dogs after induction of anesthesia (Group H-Anesth). Groups ID-MRI and H-MRI were induced to anesthesia with propofol, IV to effect, and maintained on isoflurane or propofol. Dogs in H-Anesth were premedicated with acepromazine and hydromorphone, induced with propofol or thiopental, IV to effect, and maintained on isoflurane. Neurologic scores (NS) and sedation scores (SS) were assessed pre-anesthesia in ID-MRI dogs. There was a tendency for higher cerebrospinal fluid lactate (CSFL) in ID-MRI than H-MRI or H-Anesth (p = 0.12). There was agreement between CSFL and plasma lactate (PL) in ID-MRI dogs (p = 0.007), but not in H-MRI (p = 0.45) or H-Anesth (p = 0.15). Of the ID-MRI dogs, those with worse NS had higher CSFL (r2 = 0.44). Propofol showed some advantages to isoflurane in this patient population for maintenance of blood pressure and recovery. The results of the second study warrant further investigation.