Objective—To investigate the effects of buprenorphine on cardiopulmonary variables and on abdominal auscultation scores in horses.
Animals—6 healthy adult horses.
Procedures—Horses were restrained in stocks and allocated to 2 treatments in a randomized crossover design, with 1-week intervals between each treatment. Saline (0.9% NaCl) solution was administered IV as a control, whereas buprenorphine (10 μg/kg, IV) was administered to the experimental group. Cardiopulmonary data were collected for 120 minutes after buprenorphine or saline solution administration. Abdominal auscultation scores were monitored for 2 and 12 hours after drug administration in the control and experimental groups, respectively.
Results—Following control treatment, horses remained calm while restrained in the stocks and no significant changes in cardiopulmonary variables were observed throughout the study. Buprenorphine administration caused excitatory phenomena (restlessness and head shaking). Heart rate, cardiac index, and arterial blood pressure were significantly increased after buprenorphine administration until the end of the observational period (120 minutes). Minimal changes were found in arterial blood gas tensions. Abdominal auscultation scores decreased significantly from baseline for 4 hours after buprenorphine administration.
Conclusions and Clinical Relevance— Buprenorphine induced excitement and hemodynamic stimulation with minimal changes in arterial blood gas tensions. These effects may impact the clinical use of buprenorphine in horses. Further studies are indicated to investigate the effects of buprenorphine on gastrointestinal motility and fecal output.
Objective—To evaluate the effect of remifentanil administered by use of a constant rate infusion on the predicted plasma concentration (Cppredicted) of propofol required to prevent awareness in 50% of anesthetized dogs (Cp50predicted).
Animals—6 healthy dogs.
Procedures—Each dog received 2 treatments (1-week interval): induction and maintenance of anesthesia with propofol alone and induction of anesthesia with propofol and maintenance of anesthesia by use of propofol and a constant rate infusion of remifentanil (0.3 μg/kg/min). To induce anesthesia, propofol was administered by use of a target-controlled infusion system to achieve Cppredicted of 6.0 μg/mL. Propofol Cppredicted was adjusted in 0.5 μg/mL increments or decrements; the motor response to a supramaximal electrical nociceptive stimulus was assessed after each change to determine Cp50predicted (mean of the highest Cppredicted at which gross purposeful movement was detected in response to stimulation and the lowest Cppredicted at which such movement was not detected).
Results—Mean ± SD duration of anesthesia for dogs receiving propofol (148 ± 35 minutes) and dogs receiving propofol-remifentanil treatment (141 ± 28 minutes) did not differ. Overall mean propofol Cppredicted for induction of anesthesia was 6.0 ± 0.5 μg/mL. For maintenance of anesthesia, propofol Cp50predicted was significantly reduced following addition of remifentanil to the protocol (2.0 ± 0.5 μg/mL vs 0.9 ± 0.4 μg/mL; 55% decrease).
Conclusions and Clinical Relevance—In nonpremedicated dogs, propofol Cp50predicted of 6.0 μg/mL may be recommended for induction of anesthesia. Propofol requirements for maintaining target-controlled infusion system–based anesthesia were reduced via infusion of remifentanil at a rate of 0.3 μg/kg/min.
Objective—To evaluate the correlation between the bispectral index (BIS) and end-tidal isoflurane (ETISO) concentration and compare the use of 3 BIS sensor positions in dogs.
Animals—6 adult dogs.
Procedures—Mechanically ventilated dogs received pancuronium, and depth of anesthesia was altered by increasing ETISO concentration from 1.5% to 2.3% and 3.0%. The BIS, suppression ratio (relative percentage of isoelectric electroencephalographic waveforms), and signal quality index (SQI) were recorded at each ETISO concentration for each of 3 BIS sensor positions (frontal-occipital, bifrontal, and frontal-temporal positions).
Results—The BIS and ETISO concentration were poorly correlated; regardless of sensor positioning, mean BIS values did not change significantly as ETISO was increased. At 3% isoflurane, regardless of sensor positioning, there was an increase in suppression ratio coincident with BIS < 40 in some dogs, whereas paradoxic increases in BIS (> 60) were recorded in others. Furthermore, at 3.0% isoflurane, the SQI was significantly lower for the bifrontal sensor position (compared with values for the other positions), but low SQI values prevented recording of BIS values from the frontal-occipital sensor position in 2 dogs. Overall, BIS values derived from the 3 sensor positions did not differ.
Conclusions and Clinical Relevance—In dogs, BIS values may not reflect changes in depth of isoflurane anesthesia in the absence of noxious stimulation. Of the 3 sensor positions, frontal-temporal positioning provided better correlation with changes in depth of anesthesia induced via changes in isoflurane concentrations. However, the sensor placements yielded similar results at SQI values > 50.