Objective—To compare the anesthetic and cardiorespiratory effects of total IV anesthesia with propofol (P-TIVA) or a ketamine-medetomidine-propofol combination (KMP-TIVA) in horses. Design—Randomized experimental trial. Animals—12 horses. Procedure—Horses received medetomidine (0.005 mg/kg [0.002 mg/lb], IV). Anesthesia was induced with midazolam (0.04 mg/kg [0.018 mg/lb], IV) and ketamine (2.5 mg/kg [1.14 mg/lb], IV). All horses received a loading dose of propofol (0.5 mg/kg [0.23 mg/lb], IV), and 6 horses underwent P-TIVA (propofol infusion). Six horses underwent KMP-TIVA (ketamine [1 mg/kg/h {0.45 mg/lb/h}] and medetomidine [0.00125 mg/kg/h {0.0006 mg/lb/h}] infusion; the rate of propofol infusion was adjusted to maintain anesthesia). Arterial blood pressure and heart rate were monitored. Qualities of anesthetic induction, transition to TIVA, and maintenance of and recovery from anesthesia were evaluated. Results—Administration of KMP IV provided satisfactory anesthesia in horses. Compared with the P-TIVA group, the propofol infusion rate was significantly less in horses undergoing KMP-TIVA (0.14 ± 0.02 mg/kg/min [0.064 ± 0.009 mg/lb/min] vs 0.22 ± 0.03 mg/kg/min [0.1 ± 0.014 mg/lb/min]). In the KMP-TIVA and P-TIVA groups, anesthesia time was 115 ± 17 minutes and 112 ± 11 minutes, respectively, and heart rate and arterial blood pressure were maintained within acceptable limits. There was no significant difference in time to standing after cessation of anesthesia between groups. Recovery from KMP-TIVA and P-TIVA was considered good and satisfactory, respectively. Conclusions and Clinical Relevance—In horses, KMP-TIVA and P-TIVA provided clinically useful anesthesia; the ketamine-medetomidine infusion provided a sparing effect on propofol requirement for maintaining anesthesia.

ABSTRACT. The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 µg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKMdrug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia was 38 ± 8 min and infusion rate of MKM-drug combination was 0.091 ± 0.021 ml/kg/hr. Time to standing after discontinuing MKM-TIVA was 33 ± 13 min. The quality of recovery from anesthesia was satisfactory in 3 horses and good in 6 horses. An additional 5 healthy thoroughbred horses were anesthetized with MKM-TIVA in order to assess cardiopulmonary effects. These 5 horses were anesthetized for 60 min and administered MKM-drug combination at 0.1 ml/kg/hr. Cardiac output and cardiac index decreased to 70-80%, stroke volume increased to 110% and systemic vascular resistance increased to 130% of baseline value. The partial pressure of arterial blood carbon dioxide was maintained at approximately 50 mmHg while the arterial partial pressure of oxygen pressure decreased to 50-60 mmHg. MKM-TIVA provides clinically acceptable general anesthesia with mild cardiopulmonary depression in horses. Inspired air should be supplemented with oxygen to prevent hypoxemia during MKM-TIVA. KEY WORDS: equine, ketamine, medetomidine, midazolam, total intravenous anesthesia.

Cardiovascular measurements remained within acceptable values in artificially ventilated horses during P-TIVA or KMP-TIVA. Decreased cardiac output associated with KMP-TIVA was primarily the result of decreases in heart rate.

ABSTRACT. Electroretinography (ERG) is an effective method for the diagnosis of retinal disease. In the dog, dependable ERG recording is difficult without the use of an expensive device like a Ganzfeld full-field stimulator. The International Society for Clinical Electrophysiology of Vision has defined the standard flash stimulus condition (SF) and evaluation of the retina using the b/a ratio in humans. In dogs, evaluation using the b/a ratio has not been reported, whereas the intensity of SF has been defined. In this study, we performed a convenient ERG recording method using a contact lens electrode with a built-in light source (LED-electrode), and confirmed SF as reported previously. ERG recordings were performed on 15 healthy beagle dogs under sedation. We performed bilateral ERG at 12 different intensities after 30 min dark adaptation. After 10 min light adaptation, we recorded single flash cone and flicker cone response using the SF determined in this study. In this study, SF of 3.0 cd/m 2 /sec (6,000 cd/m 2 , 0.5 msec) resulted in b/a=2. The intensity for rod response that recorded only the b-wave was 0.0096 cd/m 2 /sec (80 cd/m 2 , 0.12 msec). We could achieve ERG for each response easily and smoothly under sedation, and without general anesthesia. Using an LED-electrode, we could perform more quantitative and reproducible ERG examinations than with traditional methods. We propose that the b/a ratio is the most useful parameter in ERG reporting for evaluating retinal function. KEY WORDS: canine, contact lens electrode, electroretinography, rod response, standard flash.

ABSTRACT. Sparing effects of carprofen and meloxicam with or without butorphanol on the minimum alveolar concentration (MAC) of sevoflurane were determined in 6 dogs. Anesthesia was induced and maintained with sevoflurane in oxygen, and MAC was determined by use of a tail clamp method. The dogs were administered a subcutaneous injection of carprofen (4 mg/kg) or meloxicam (0.2 mg/kg), or no medication (control) one hour prior to induction of anesthesia. Following the initial determination of MAC, butorphanol (0.3 mg/ kg) was administered intramuscularly, and MAC was determined again. The sevoflurane MACs for carprofen alone (2.10 ± 0.26%) and meloxicam alone (2.06 ± 0.20%) were significantly less than the control (2.39 ± 0.26%). The sevoflurane MACs for the combination of carprofen with butorphanol (1.78 ± 0.20%) and meloxicam with butorphanol (1.66 ± 0.29%) were also significantly less than the control value after the administration of butorphanol (2.12 ± 0.28%). The sevoflurane sparing effects of the combinations of carprofen with butorphanol and meloxicam with butorphanol were additive.