Objective—To determine induction doses, anesthetic
constant rate infusions (CRI), and cardiopulmonary
effects of propofol in red-tailed hawks and great
horned owls and propofol pharmacokinetics in the
owls during CRI.
Animals—6 red-tailed hawks and 6 great horned
Procedure—The CRI dose necessary for a loss of
withdrawal reflex was determined via specific stimuli.
Anesthesia was induced by IV administration of
propofol (1 mg/kg/min) and maintained by CRI at the
predetermined dose for 30 minutes. Heart and respiratory
rates, arterial blood pressures, and blood gas
tensions were obtained in awake birds and at various
times after induction. End-tidal CO2 (ETCO2) concentration
and esophageal temperature were obtained
after induction. Propofol plasma concentrations were
obtained after induction and after completion of the
CRI in the owls. Recovery times were recorded.
Results—Mean ± SD doses for induction and CRI
were 4.48 ± 1.09 mg/kg and 0.48 ± 0.06 mg/kg/min,
respectively, for hawks and 3.36 ± 0.71 mg/kg and
0.56 ± 0.15 mg/kg/min, respectively, for owls.
Significant increases in PaCO2, HCO3, and ETCO2 in
hawks and owls and significant decreases in arterial
pH in hawks were detected. A 2-compartment model
best described the owl pharmacodynamic data.
Recovery times after infusion were prolonged and
varied widely. Central nervous system excitatory
signs were observed during recovery.
Conclusions and Clinical Relevance—Effects on
blood pressure were minimal, but effective ventilation
was reduced, suggesting the need for careful monitoring
during anesthesia. Prolonged recovery periods
with moderate-to-severe excitatory CNS signs may
occur in these species at these doses. (Am J Vet Res 2003;64:677–683)
Objective—To compare effectiveness and complications associated with peribulbar and retrobulbar anesthesia with bupivacaine in cats.
Animals—6 healthy adult cats.
Procedures—Cats were sedated with dexmedetomidine and received a peribulbar injection of 0.5% bupivacaine (1.5 mL), iopamidol (0.5 mL), and saline (0.9% NaCl) solution (1 mL) or retrobulbar injection of 0.5% bupivacaine (0.75 mL) and iopamidol (0.25 mL) in a crossover study with ≥ 2 weeks between treatments. The contralateral eye was the control. Injectate distribution was evaluated with CT. After atipamezole administration, periocular and corneal sensations, intraocular pressure (IOP), and ocular reflexes and appearance were evaluated for 24 hours.
Results—All peribulbar and 3 of 6 retrobulbar injections resulted in CT evidence of intraconal injectate. Corneal sensation and periocular skin sensation were absent or significantly reduced relative to that for control eyes for 3 hours after peribulbar injection. Mean ± SD IOP immediately after injection was significantly higher for eyes with peribulbar injections (33 ± 12 mm Hg) than for control eyes or eyes with retrobulbar injections (both 14 ± 4 mm Hg) but 10 minutes later decreased to 18 ± 3 mm Hg. Exophthalmos, chemosis, and ptosis were evident in most injected eyes, and irritation was evident in 3 of 6 peribulbar-injected and 1 of 6 retrobulbar-injected eyes. All conditions resolved within 14 hours.
Conclusions and Clinical Relevance—Peribulbar injection resulted in intraconal deposition of bupivicaine in a higher percentage of cats than did retrobulbar injection and induced notable anesthesia relative to that for the control eye; however, IOP increased temporarily.
PROCEDURES Anesthesia was induced and maintained with isoflurane; intermittent positive-pressure ventilation was provided. The minimum alveolar concentration of isoflurane was determined for each bird by use of the bracketing method and a supramaximal electrical stimulus. Fentanyl (20 μg/kg) was administered IV. Arterial (red-tailed hawks) or jugular venous (Hispaniolan Amazon parrots) blood samples were obtained immediately before and 1, 2, 4, 8, 15, 30, 60, 120, 180, 240, and 480 minutes (red-tailed hawks) and 1, 5, 10, 15, 30, 60, 120, and 180 minutes (Hispaniolan Amazon parrots) after fentanyl administration.
RESULTS A 3-compartment and a 2-compartment model best described fentanyl pharmacokinetics in red-tailed hawks and Hispaniolan Amazon parrots, respectively. Median apparent volume of the central compartment and volume of distribution at steady state were 222 mL/kg and 987 mL/kg, respectively, for the red-tailed hawks and 5,108 mL/kg and 13,079 mL/kg, respectively, for the Hispaniolan Amazon parrots. Median clearance and elimination half-life were 8.9 mL/min/kg and 90.22 minutes, respectively, for the red-tailed hawks and 198.8 mL/min/kg and 51.18 minutes, respectively, for the Hispaniolan Amazon parrots.
CONCLUSIONS AND CLINICAL RELEVANCE Pharmacokinetic results for fentanyl in isoflurane-anesthetized red-tailed hawks and Hispaniolan Amazon parrots indicated large differences and should strongly discourage extrapolation of doses between these 2 species.
Objective—To evaluate the effects of dorsal versus lateral recumbency on the cardiopulmonary system during isoflurane anesthesia in red-tailed hawks (Buteo jamaicensis).
Animals—6 adult 1.1- to 1.6-kg red-tailed hawks.
Procedures—A randomized, crossover study was used to evaluate changes in respiratory rate, tidal volume, minute ventilation, heart rate, mean arterial and indirect blood pressures, and end-tidal Pco2 measured every 5 minutes plus Paco2 and Pao2 and arterial pH measured every 15 minutes throughout a 75-minute study period.
Results—Respiratory rate was higher, tidal volume lower, and minute ventilation not different in lateral versus dorsal recumbency. Position did not affect heart rate, mean arterial blood pressure, or indirect blood pressure, although heart rate decreased during the anesthetic period. Birds hypoventilated in both positions and Paco2 differed with time and position × time interaction. The Petco2 position × time interaction was significant and Petco2 was a mean of 7 Torr higher than Paco2. The Paco2 in dorsal recumbency was a mean of 32 Torr higher than in lateral recumbency. Birds in both positions developed respiratory acidosis.
Conclusions and Clinical Relevance—Differences in tidal volume with similar minute ventilation suggested red-tailed hawks in dorsal recumbency might have lower dead space ventilation. Despite similar minute ventilation in both positions, birds in dorsal recumbency hypoventilated more yet maintained higher Pao2, suggesting parabronchial ventilatory or pulmonary blood flow distribution changes with position. The results refute the hypothesis that dorsal recumbency compromises ventilation and O2 transport more than lateral recumbency in red-tailed hawks.
OBJECTIVE To compare intraosseous pentobarbital treatment (IPT) and thoracic compression (TC) on time to circulatory arrest and an isoelectric electroencephalogram (EEG) in anesthetized passerine birds.
ANIMALS 30 wild-caught adult birds (17 house sparrows [Passer domesticus] and 13 European starlings [Sturnus vulgaris]).
PROCEDURES Birds were assigned to receive IPT or TC (n = 6/species/group). Birds were anesthetized, and carotid arterial pulses were monitored by Doppler methodology. Five subdermal braided-wire electrodes were used for EEG. Anesthetic depth was adjusted until a continuous EEG pattern was maintained, then euthanasia was performed. Times from initiation of euthanasia to cessation of carotid pulse and irreversible isoelectric EEG (indicators of death) were measured. Data (medians and first to third quartiles) were summarized and compared between groups within species. Necropsies were performed for all birds included in experiments and for another 6 birds euthanized under anesthesia by TC (4 sparrows and 1 starling) or IPT (1 sparrow).
RESULTS Median time to isoelectric EEG did not differ significantly between treatment groups for sparrows (19.0 and 6.0 seconds for TC and IPT, respectively) or starlings (88.5 and 77.5 seconds for TC and IPT, respectively). Median times to cessation of pulse were significantly shorter for TC than for IPT in sparrows (0.0 vs 18.5 seconds) and starlings (9.5 vs 151.0 seconds). On necropsy, most (14/17) birds that underwent TC had grossly visible coelomic, pericardial, or perihepatic hemorrhage.
CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that TC might be an efficient euthanasia method for small birds. Digital pressure directly over the heart during TC obstructed venous return, causing rapid circulatory arrest, with rupture of the atria or vena cava in several birds. The authors propose that cardiac compression is a more accurate description than TC for this procedure.
OBJECTIVE To determine effects of 3 plasma concentrations of fentanyl on the minimum alveolar concentration of isoflurane (MACiso) and cardiovascular variables in Hispaniolan Amazon parrots (Amazona ventralis).
ANIMALS 6 adult parrots.
PROCEDURES In phase 1, anesthesia was induced and maintained with isoflurane; intermittent positive-pressure ventilation was provided. The MACiso was determined for each bird by use of a bracketing method and supramaximal electrical stimulus. Fentanyl (20 μg/kg) was administered IV, and blood samples were collected over time to measure plasma fentanyl concentrations for pharmacokinetic calculations. In phase 2, pharmacokinetic values for individual birds were used for administration of fentanyl to achieve target plasma concentrations of 8, 16, and 32 ng/mL. At each concentration, MACiso and cardiovascular variables were determined. Data were analyzed with mixed-effects multilevel linear regression analysis.
RESULTS Mean ± SD fentanyl plasma concentrations were 0 ng/mL, 5.01 ± 1.53 ng/mL, 12.12 ± 3.58 ng/mL, and 24.93 ± 4.13 ng/mL, and MACiso values were 2.09 ± 0.17%, 1.45 ± 0.32%, 1.34 ± 0.31%, and 0.95 ± 0.14% for fentanyl target concentrations of 0, 8, 16, and 32 ng/mL, respectively. Fentanyl significantly decreased MACiso in a dose-dependent manner. Heart rate and blood pressure significantly decreased at all fentanyl doses, compared with values for MACiso at 0 ng of fentanyl/mL.
CONCLUSIONS AND CLINICAL RELEVANCE Fentanyl significantly decreased the MACiso in healthy Hispaniolan Amazon parrots, but this was accompanied by a depressive effect on heart rate and blood pressure that would need to be considered for application of this technique in clinical settings.
Objective—To describe clinicopathologic features of dogs that underwent lung lobectomy for resection of primary lung tumors via video-assisted thoracoscopic surgery (VATS) or open thoracotomy (OT) and to compare short-term outcomes for dogs following these procedures.
Design—Retrospective cohort study.
Animals—46 medium- to large-breed dogs with primary lung tumors.
Procedures—Medical records of dogs that underwent a lung lobectomy via VATS (n = 22) or OT (24) for resection of primary lung tumors between 2004 and 2012 were reviewed. Dogs were included if they weighed > 10 kg (22 lb) and resection of a primary lung tumor was confirmed histologically. Tumor volumes were calculated from preoperative CT scans where available. Surgical time, completeness of excision, time in the ICU, indwelling thoracic drain time, postoperative and total hospitalization time, incidence of major complications, and short-term survival rate were evaluated.
Results—VATS was performed with a 3-port (n = 12) or 4-port (10) technique and 1-lung ventilation (22). In 2 of 22 (9%) dogs, VATS was converted to OT. All dogs survived to discharge from the hospital. There were no significant differences between the VATS and OT groups with regard to most variables. Surgery time was significantly longer for VATS than for OT (median, 120 vs 95 minutes, respectively).
Conclusions and Clinical Relevance—In medium- to large-breed dogs, short-term outcomes for dogs that underwent VATS for lung lobectomy were comparable to those of dogs that underwent OT. Further studies are required to evaluate the effects of surgical approach on indices of postoperative pain and long-term outcomes.