OBJECTIVE To compare the doses of propofol required to induce general anesthesia in dogs premedicated with acepromazine maleate or trazodone hydrochloride and compare the effects of these premedicants on cardiovascular variables in dogs anesthetized for orthopedic surgery.
PROCEDURES 15 dogs received acepromazine (0.01 to 0.03 mg/kg [0.005 to 0.014 mg/lb], IM) 30 minutes before anesthetic induction and 15 received trazodone (5 mg/kg [2.27 mg/lb] for patients > 10 kg or 7 mg/kg [3.18 mg/lb] for patients ≤ 10 kg, PO) 2 hours before induction. Both groups received morphine sulfate (1 mg/kg [0.45 mg/lb], IM) 30 minutes before induction. Anesthesia was induced with propofol (4 to 6 mg/kg [1.82 to 2.73 mg/lb], IV, to effect) and maintained with isoflurane or sevoflurane in oxygen. Bupivacaine (0.5 mg/kg [0.227 mg/lb]) and morphine (0.1 mg/kg [0.045 mg/lb]) were administered epidurally. Dogs underwent tibial plateau leveling osteotomy (n = 22) or tibial tuberosity advancement (8) and were monitored throughout anesthesia. Propofol induction doses and cardiovascular variables (heart rate and systemic, mean, and diastolic arterial blood pressures) were compared between groups.
RESULTS The mean dose of propofol required for anesthetic induction and all cardiovascular variables evaluated did not differ between groups. Intraoperative hypotension developed in 6 and 5 dogs of the acepromazine and trazodone groups, respectively; bradycardia requiring intervention developed in 3 dogs/group. One dog that received trazodone had priapism 24 hours later and was treated successfully. No other adverse effects were reported.
CONCLUSIONS AND CLINICAL RELEVANCE At the described dosages, cardiovascular effects of trazodone were similar to those of acepromazine in healthy dogs undergoing anesthesia for orthopedic surgery.
Objective—To compare preoperative administration
of meloxicam and butorphanol to perioperative administration
of butorphanol alone for control of postoperative
signs of pain in dogs.
Animals—40 client-owned dogs scheduled for surgical
repair of a cranial cruciate ligament rupture.
Procedure—Group-1 dogs received butorphanol (0.2
mg/kg, IV) and meloxicam (0.2 mg/kg, IV) just prior to
surgery. Group-2 dogs received butorphanol just prior
to surgery (0.2 mg/kg, IV) and at incision closure (0.1
mg/kg, IV). Pain assessment began 1 to 2 hours
before surgery and from extubation until 24 hours
after surgery by obtaining the following measurements:
the visual analog scale (VAS) score, cumulative
pain score (CPS), adjusted cumulative pain score,
modified cumulative pain score, and the adjusted
modified cumulative pain score (AMCPS). Serum cortisol
concentration was measured between 12 to 24
and between 1 to 2 hours prior to surgery, and at 30
minutes, and 1, 2, 4, 8, 18, and 24 hours after extubation.
Results—No significant differences between treatment
groups were observed in CPS or VAS score. At
8, 9, 10, and 11 hours after extubation, meloxicambutorphanol-
treated dogs had a significantly lower
AMCPS, compared with butorphanol-alone-treated
dogs. Total serum cortisol concentration (area under
the curve) during the measurement period was significantly
lower in meloxicam-butorphanol-treated
dogs, compared with butorphanol-alone treated dogs.
Conclusions and Clinical Relevance—Preoperative
single dose administration of meloxicam-butorphanol
is equivalent to or slightly better than the administration
of 2 perioperative doses of butorphanol for the
control of postoperative signs of pain in dogs. (Am J
Vet Res 2002;63:1557–1563)
Objective—To compare the outcomes of doublelayer
inverting anastomosis (DIA), single-layer anastomosis
(SLA), and single-layer anastomosis combined
with a hyaluronate membrane (SLA+HA-membrane)
with respect to stomal diameter, adhesion formation,
surgery time, and anastomotic healing in horses.
Animals—18 adult horses.
Procedure—Midline celiotomy and end-to-end anastomoses
were performed. In control horses (n = 6),
DIA was performed; in treated horses, SLA was performed
(6) or SLA+HA-membrane was performed (6).
Horses were euthanatized 21 days after surgery.
Abdominal adhesions were evaluated grossly and histologically.
Stomal diameters were measured ultrasonographically
and compared with adjacent luminal
diameters. Anastomotic healing was evaluated histologically
for fibrosis and inflammation, tissue alignment,
and inversion. Surgery times were recorded for
the anastomotic procedure and compared among
Results—There were significantly more adhesions in
the SLA group, compared with the DIA and SLA+HAmembrane
groups. Reduction in stomal diameters in
the DIA group was significantly greater than the SLA
and SLA+HA-membrane groups. Surgery times for
the DIA group were significantly greater than the SLA
and SLA+HA-membrane groups. Histologic findings
of fibrosis, inflammation, and mucosal healing were
similar among groups. There was significant tissue
inversion in the DIA group, compared with the 2 treatment
groups. Tissue alignment was not different
Conclusions and Clinical Relevance—Use of a
SLA+HA-membrane was an effective small intestinal
anastomotic technique. This technique was faster to
perform and resulted in a larger stomal diameter,
compared with the DIA technique and significantly
fewer perianastomotic adhesions, compared with the
SLA technique. (Am J Vet Res 2001;62:1314–1319)
To determine the pharmacokinetics and pharmacodynamics of methadone after IV or IM administration to isoflurane-anesthetized chickens.
6 healthy adult Hy-Line hens.
In a randomized crossover-design study, methadone (6 mg/kg) was administered IV and IM to isoflurane-anesthetized chickens with a 1-week washout period between experiments. Blood samples were collected immediately before and at predetermined time points up to 480 minutes after methadone administration. Plasma concentrations were determined by liquid chromatography–mass spectrometry, and appropriate compartmental models were fit to the plasma concentration-versus-time data. Cardiorespiratory variables were compared between treatments and over time with mixed-effect repeated-measures analysis.
A 3-compartment model best described the changes in plasma methadone concentration after IV or IM administration. Estimated typical values for volumes of distribution were 692 mL/kg for the central compartment and 2,439 and 2,293 mL/kg for the first and second peripheral compartments, respectively, with metabolic clearance of 23.3 mL/kg/min and first and second distributional clearances of 556.4 and 51.8 mL/kg/min, respectively. Typical bioavailability after IM administration was 79%. Elimination half-life was 177 minutes, and maximum plasma concentration after IM administration was 950 ng/mL. Heart rate was mildly decreased at most time points beginning 5 minutes after IV or IM drug administration.
CONCLUSIONS AND CLINICAL RELEVANCE
Disposition of methadone in isoflurane-anesthetized chickens was characterized by a large volume of distribution and moderate clearance, with high bioavailability after IM administration. Additional studies are warranted to assess pharmacokinetics and pharmacodynamics of methadone in awake chickens.
To evaluate the effect of a constant rate infusion of ketamine on cardiac index (CI) in sheep, as estimated using noninvasive cardiac output (NICO) monitoring by partial carbon dioxide rebreathing, when anesthetized with sevoflurane at the previously determined minimum alveolar concentration that blunts adrenergic responses (MACBAR).
12 healthy Dorset-crossbred adult sheep.
Sheep were anesthetized 2 times in a balanced placebo-controlled crossover design. Anesthesia was induced with sevoflurane delivered via a tight-fitting face mask and maintained at MACBAR. Following induction, sheep received either ketamine (1.5 mg/kg IV, followed by a constant rate infusion of 1.5 mg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (placebo). After an 8-day washout period, each sheep received the alternate treatment. NICO measurements were performed in triplicate 20 minutes after treatment administration and were converted to CI. Blood samples were collected prior to the start of NICO measurements for analysis of ketamine plasma concentrations. The paired t test was used to compare CI values between groups and the ketamine plasma concentrations with those achieved during the previous study.
Mean ± SD CI of the ketamine and placebo treatments were 2.69 ± 0.65 and 2.57 ± 0.53 L/min/m2, respectively. No significant difference was found between the 2 treatments. Mean ketamine plasma concentration achieved prior to the NICO measurement was 1.37 ± 0.58 µg/mL, with no significant difference observed between the current and prior study.
Ketamine, at the dose administered, did not significantly increase the CI in sheep when determined by partial carbon dioxide rebreathing.
OBJECTIVE To determine the minimum alveolar concentration that blunts adrenergic responses (MACBAR) for isoflurane and evaluate effects of fentanyl on isoflurane MACBAR in sheep.
ANIMALS 13 healthy adult Dorset-cross adult ewes.
PROCEDURES In a crossover design, each ewe was anesthetized 2 times for determination of isoflurane MACBAR. Anesthesia was induced with propofol administered IV. Sheep initially received fentanyl (5 μg/kg, IV, followed by a constant rate infusion of 5 μg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment). After a washout period of at least 8 days, the other treatment was administered. For MACBAR determination, a mechanical nociceptive stimulus (ie, sponge forceps) was applied at the coronary band for 1 minute. The MACBAR values of the 2 treatments were compared by means of a paired t test. During MACBAR determination, blood samples were collected for measurement of plasma fentanyl concentration.
RESULTS Mean ± SD isoflurane MACBAR of the fentanyl and control treatments was 1.70 ± 0.28% and 1.79 ± 0.35%, respectively; no significant difference was found between the 2 treatments. Plasma concentration of fentanyl reached a median steady-state concentration of 1.69 ng/mL (interquartile range [25th to 75th percentile], 1.47 to 1.79 ng/mL), which was maintained throughout the study.
CONCLUSIONS AND CLINICAL RELEVANCE Administration of fentanyl at 5 μg/kg, IV, followed by a constant rate infusion of the drug at 5 μg/kg/h did not decrease isoflurane MACBAR. Further studies to determine the effect of higher doses of fentanyl on inhalation anesthetic agents and their potential adverse effects are warranted. (Am J Vet Res 2016;77:119–126)
OBJECTIVE To compare analgesic and gastrointestinal effects of lidocaine and buprenorphine administered to rabbits undergoing ovariohysterectomy.
ANIMALS Fourteen 12-month-old female New Zealand White rabbits.
PROCEDURES Rabbits were assigned to 2 treatment groups (7 rabbits/group). One group received buprenorphine (0.06 mg/kg, IV, q 8 h for 2 days), and the other received lidocaine (continuous rate infusion [CRI] at 100 μg/kg/min for 2 days). Variables, including food and water consumption, fecal output, glucose and cortisol concentrations, and behaviors while in exercise pens, were recorded.
RESULTS Rabbits receiving a lidocaine CRI had significantly higher gastrointestinal motility, food intake, and fecal output and significantly lower glucose concentrations, compared with results for rabbits receiving buprenorphine. Rabbits receiving lidocaine also had a higher number of normal behaviors (eg, sprawling, traveling, and frolicking) after surgery, compared with behaviors such as crouching and sitting that were seen more commonly in rabbits receiving buprenorphine. Both groups had significant weight loss after surgery. Pain scores did not differ significantly between treatment groups. Significant decreases in heart rate and respiratory rate were observed on the day of surgery, compared with values before and after surgery. Rabbits in the lidocaine group had significantly overall lower heart rates than did rabbits in the buprenorphine group.
CONCLUSIONS AND CLINICAL RELEVANCE A CRI of lidocaine to rabbits provided better postoperative outcomes with respect to fecal output, food intake, and glucose concentrations. Thus, lidocaine appeared to be a suitable alternative to buprenorphine for alleviating postoperative pain with minimal risk of anorexia and gastrointestinal ileus.