OBJECTIVE To determine the cardiopulmonary effects of IV administration of fentanyl to cats anesthetized with isoflurane and during anesthetic recovery with concurrent administration of acepromazine or dexmedetomidine. ANIMALS 6 healthy adult cats. PROCEDURES Cats received an IV bolus (5 μg/kg) followed by an IV infusion (5 μg/kg/h) of fentanyl for 120 minutes during isoflurane anesthesia and for 30 minutes after discontinuing isoflurane. Cats were randomly assigned in a crossover study to receive acepromazine (0.05 mg/kg) or dexmedetomidine (2.5 μg/kg), IV, when isoflurane was discontinued. Cardiopulmonary data were obtained during anesthesia and for 30 minutes during the anesthetic recovery period. RESULTS The administration of fentanyl during isoflurane anesthesia resulted in a transient increase in arterial blood pressure, mean pulmonary artery pressure, and oxygen delivery. Compared with values during isoflurane anesthesia, administration of dexmedetomidine during anesthetic recovery resulted in significant decreases in cardiac index, stroke index, and oxygen delivery and significant increases in arterial, central venous, and mean pulmonary artery pressures; systemic vascular resistance index; and oxygen extraction ratio. Administration of acepromazine resulted in increases in heart rate, cardiac index, oxygen uptake, and oxygen extraction ratio. Oxygen extraction ratio did not differ between acepromazine and dexmedetomidine. CONCLUSIONS AND CLINICAL RELEVANCE Fentanyl transiently improved indices of cardiopulmonary performance when administered to healthy cats anesthetized with isoflurane. The cardiovascular effects of acepromazine and dexmedetomidine in healthy cats receiving fentanyl during recovery from isoflurane anesthesia differed, but measured cardiopulmonary parameters remained within acceptable limits.

OBJECTIVE To evaluate the effects of using ropivacaine combined with dexmedetomidine for sciatic and saphenous nerve blocks in dogs. ANIMALS 7 healthy adult Beagles. PROCEDURES In phase 1, dogs received each of the following 3 treatments in random order: perineural sciatic and saphenous nerve injections of 0.5% ropivacaine (0.4 mL/kg) mixed with saline (0.9% NaCl) solution (0.04 mL/kg; DEX0PN), 0.5% ropivacaine mixed with dexmedetomidine (1 μg/kg; DEX1PN), and 0.5% ropivacaine mixed with dexmedetomidine (2 μg/kg; DEX2PN). In phase 2, dogs received perineural sciatic and saphenous nerve injections of 0.5% ropivacaine and an IV injection of diluted dexmedetomidine (1 μg/kg; DEX1IV). For perineural injections, the dose was divided equally between the 2 sites. Duration of sensory blockade was evaluated, and plasma dexmedetomidine concentrations were measured. RESULTS Duration of sensory blockade was significantly longer with DEX1PN and DEX2PN, compared with DEX0PN; DEX1IV did not prolong duration of sensory blockade, compared with DEX0PN. Peak plasma dexmedetomidine concentrations were reached after 15 minutes with DEX1PN (mean ± SD, 348 ± 200 pg/mL) and after 30 minutes DEX2PN (816 ± 607 pg/mL), and bioavailability was 54 ± 40% and 73 ± 43%, respectively. The highest plasma dexmedetomidine concentration was measured with DEX1IV (1,032 ± 415 pg/mL) 5 minutes after injection. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that perineural injection of 0.5% ropivacaine in combination with dexmedetomidine (1 μg/kg) for locoregional anesthesia in dogs seemed to balance the benefit of prolonging sensory nerve blockade while minimizing adverse effects.

In humans and other mammals, general anesthesia impairs thermoregulation, leading to warm core blood redistributing to the periphery. This redistribution is an important contributor to hypothermia that can be reduced with pre-warming before anesthesia. Additionally, sedation following premedication has been associated with hypothermia in dogs. In a prospective, randomized, cross-over study, 8 adult male and female rats (weighing 388 to 755 g) were sedated with intramuscular ketamine-midazolam-hydromorphone, then placed in an unwarmed cage or warmed box for 14 minutes, followed by 30 minutes of isoflurane anesthesia with active warming. Core body temperature was monitored throughout. After sedation, warmed rats gained 0.28°C ± 0.13°C and unwarmed rats lost 0.19°C ± 0.43°C, a significant difference between groups (P = 0.004). After anesthesia, warmed rats maintained higher core temperatures (P < 0.0001) with 2/8 and 6/8 of warmed and unwarmed rats becoming hypothermic, respectively. Pre-warming during sedation and active warming during general anesthesia is effective in minimizing hypothermia.

OBJECTIVE To assess the feasibility of a novel technique involving a vessel and tissue–sealing device (VTSD) for ovariectomy in chickens to evaluate the potential application of the procedure to other avian species. ANIMALS 20 domestic laying hens (Gallus domesticus), of which 10 were immature (< 4 months old) and 10 were adults (> 18 months old). PROCEDURES Ovariectomy was performed with a VTSD through a left lateral celiotomy. Birds were allowed to recover for 14 days after the procedure and then were euthanized for necropsy. A board-certified veterinary pathologist performed complete necropsies, with particular attention to identifying any remaining ovarian tissue. RESULTS All birds survived the procedure. For the mature and juvenile birds, the mean ± SD durations of anesthesia (interval from intubation to extubation) were 67.2 ± 7.6 minutes and 50.5 ± 5.1 minutes, respectively, and mean durations of surgery were 45.3 ± 8.5 minutes and 31.6 ± 5.1 minutes, respectively. Three birds had severe hemorrhage during ovariectomy. At necropsy, ovarian tissue was present grossly in 2 mature birds and histologically in 6 additional birds (2 mature and 4 juvenile birds), indicating incomplete excision in 8 (40%) birds. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the evaluated VTSD can be used to successfully perform ovariectomies in both juvenile and mature chickens, although the procedure was associated with major hemorrhage and incomplete excision of ovarian tissue in some cases. Use of this VTSD for ovariectomy in birds of other species, particularly birds with reproductive tract disease, should be investigated.

OBJECTIVE To determine whether isoflurane-anesthetized cats with demonstrated resistance to the immobilizing effects of fentanyl would exhibit naltrexone-reversible sparing of the minimum alveolar concentration (MAC) of isoflurane when fentanyl was coadministered with the centrally acting catecholamine receptor antagonist acepromazine. ANIMALS 5 healthy male purpose-bred cats. PROCEDURES Anesthesia was induced and maintained with isoflurane in oxygen. Baseline isoflurane MAC was measured by use of a standard tail clamp stimulus and bracketing study design. Afterward, fentanyl was administered IV to achieve a plasma concentration of 100 ng/mL by means of target-controlled infusion, and isoflurane MAC was remeasured. Next, acepromazine maleate (0.1 mg/kg) was administered IV, and isoflurane MAC was remeasured. Finally, isoflurane concentration was equilibrated at 70% of the baseline MAC. Movement of cats in response to tail clamping was tested before and after IV bolus administration of naltrexone. Physiologic responses were compared among treatment conditions. RESULTS Isoflurane MAC did not differ significantly between baseline and fentanyl infusion (mean ± SD, 1.944 ± 0.111% and 1.982 ± 0.126%, respectively). Acepromazine with fentanyl significantly decreased isoflurane MAC to 1.002 ± 0.056% of 1 atm pressure. When isoflurane was increased to 70% of the baseline MAC, no cats moved in response to tail clamping before naltrexone administration, but all cats moved after naltrexone administration. CONCLUSIONS AND CLINICAL RELEVANCE Acepromazine caused fentanyl to decrease the isoflurane MAC in cats that otherwise did not exhibit altered isoflurane requirements with fentanyl alone. Results suggested that opioid-mediated increases in brain catecholamine concentrations in cats counteract the opioid MAC-sparing effect.

OBJECTIVE To compare intraoperative and short-term postoperative variables pertaining to laparoscopic ovariectomy (LapOVE) and open ovariectomy (OVE) in rabbits (Oryctolagus cuniculus). ANIMALS Twelve 4− to 5-month-old female New Zealand White rabbits. PROCEDURES Rabbits were randomly assigned to undergo LapOVE (n = 6) or OVE (6), with a vessel-sealing device used to seal and transect the ovarian pedicles. Laparoscopic ovariectomy was performed with a 3-port approach. Variables were measured during surgery (surgery and anesthesia times and incision lengths) and for up to 7 days after surgery (food consumption, feces production, body weight, vital parameters, blood glucose and cortisol concentrations, abdominal palpation findings, facial grimace scale scores, and ethograms). RESULTS Mean surgery (43.2 vs 21.7 minutes) and anesthesia (76.2 vs 48.8 minutes) times were longer and mean incision length was shorter (24.0 vs 41.5 mm) for LapOVE versus OVE. No significant differences in postoperative variables were identified between groups. During LapOVE, small intestinal perforation occurred in 1 rabbit, which was then euthanized. Postoperative complications for the remaining rabbits included superficial incisional dehiscence (LapOVE, 1/5; OVE, 2/6), subcutaneous emphysema (LapOVE, 1/5; OVE, 0/6), and seroma formation (LapOVE, 1/5; OVE, 0/6). CONCLUSIONS AND CLINICAL RELEVANCE Surgery time for LapOVE was twice that of OVE, and LapOVE resulted in unique complications in rabbits. No evidence of a reduction in pain or faster return to baseline physiologic status was found for LapOVE. Further evaluation of LapOVE in rabbits is warranted, with modification to techniques used in this study or a larger sample size.