OBJECTIVE To determine the locomotor response to the administration of fentanyl in horses with and without the G57C polymorphism of the μ-opioid receptor.
ANIMALS 20 horses of various breeds and ages (10 horses heterozygous for the G57C polymorphism and 10 age-, breed-, and sex-matched horses that did not have the G57C polymorphism).
PROCEDURES The number of steps each horse took was counted over consecutive 2-minute periods for 20 minutes to determine a baseline value. The horse then received a bolus of fentanyl (20 μg/kg, IV), and the number of steps was again counted during consecutive 2-minute periods for 60 minutes. The mean baseline value was subtracted from each 2-minute period after fentanyl administration; step counts with negative values were assigned a value of 0. Data were analyzed by use of a repeated-measures ANOVA.
RESULTS Data for 19 of 20 horses (10 horses with the G57C polymorphism and 9 control horses without the G57C polymorphism) were included in the analysis. Horses with the G57C polymorphism had a significant increase in locomotor activity, compared with results for horses without the polymorphism. There was a significant group-by-time interaction.
CONCLUSIONS AND CLINICAL RELEVANCE Horses heterozygous for the G57C polymorphism of the μ-opioid receptor had an increased locomotor response to fentanyl administration, compared with the response for horses without this polymorphism. The clinical impact of this finding should be investigated.
Objective—To evaluate the effect of pneumoperitoneum on cardiorespiratory variables and working space during experimental induction of 3 intra-abdominal pressures (IAPs) in cats.
Animals—6 healthy young adult neutered male domestic shorthair cats.
Procedures—All cats were anesthetized through use of a standardized protocol. A catheter was placed in the right femoral artery for blood pressure and blood gas monitoring. A thermodilution catheter was placed in the right jugular vein via fluoroscopic guidance. Cardiopulmonary variables were measured before (baseline) and 2 and 30 minutes after initiation of pneumoperitoneum at IAPs of 4, 8, and 15 mm Hg; these were created through the use of a mechanical insufflator. At each IAP, abdominal dimensions (height, width, and circumference) were measured at a standardized location.
Results—At 4 mm Hg and 8 mm Hg IAP, no clinically important changes were identified in cardiorespiratory values. Heart rate, cardiac index, and stroke volume index remained unchanged throughout the study at all IAPs. Mean arterial blood pressure began to increase at 8 mm Hg and was significantly higher, compared with baseline, at both time points at 15 mm Hg. At 15 mm Hg, Paco2 was significantly higher and cats were more acidotic than at baseline. Working space was subjectively greater at 8 mm Hg than at 4 mm Hg IAP; however, at 15 mm Hg, no clinically important enlargement of the working space was identified, compared with at 8 mm Hg.
Conclusions and Clinical Relevance—Values of cardiopulmonary variables were largely unchanged by induction of pneumoperitoneum in healthy cats up to an IAP of 8 mm Hg, and no clinically important increases in working space were evident at an IAP of 15 versus 8 mm Hg. These findings provide little justification for use of IAPs > 8 mm Hg in healthy cats undergoing laparoscopic procedures; however, whether the situation is similar in diseased or elderly cats remains to be determined.
Objective—To evaluate the exposure obtained for minimally invasive abdominal organ biopsy (MIOB) from 3 access incisions in cats.
Design—Prospective experimental study and clinical case series.
Animals—6 purpose-bred research cats and 6 feline clinical patients with indications for abdominal organ biopsy.
Procedures—Three 3-cm incisions into the peritoneal cavity were created at different locations along the linea alba in research cats in randomized order. A wound retraction device was inserted in each incision. Ability to exteriorize various abdominal organs to the extent required to reasonably perform a surgical biopsy was recorded, and results were compared among incision sites. On the basis of results obtained, the access incision that provided exposure of the most frequently biopsied abdominal organs was used to perform MIOB in 6 feline clinical patients with various underlying pathological conditions.
Results—On the basis of experiments with research cats, a 3-cm access incision centered midway between the caudal margin of the xiphoid cartilage and the umbilicus was found to provide access for MIOB for most organs. In 5 of 6 clinical patients, all of the organs of interest were biopsied successfully via this incision location, although access to all hepatic lobes and all parts of the pancreas was inconsistent. In 1 cat, conversion to an open approach was performed because a palpable mass was detected in the area of the duodenocolic ligament.
Conclusions and Clinical Relevance—Optimization of access incision location for MIOB allowed biopsy specimen collection from organs of interest to be performed in a minimally invasive manner in cats.
Objective—To determine the minimum anesthetic concentration (MAC) of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha) and compare MAC obtained via mechanical and electrical stimulation.
Animals—15 healthy thick-billed parrots.
Procedures—Anesthesia was induced in each parrot by administration of sevoflurane in oxygen. An end-tidal sevoflurane concentration of 2.5% was established in the first bird. Fifteen minutes was allowed for equilibration. Then, 2 types of noxious stimulation (mechanical and electrical) were applied; stimuli were separated by 15 minutes. Responses to stimuli were graded as positive or negative. For a positive or negative response to a stimulus, the target end-tidal sevoflurane concentration of the subsequent bird was increased or decreased by 10%, respectively. The MAC was calculated as the mean end-tidal sevoflurane concentration during crossover events, defined as instances in which independent pairs of birds evaluated in succession had opposite responses. A quantal method was used to determine sevoflurane MAC. Physiologic variables and arterial blood gas values were also measured.
Results—Via quantal analysis, mean sevoflurane MAC in thick-billed parrots determined with mechanical stimulation was 2.35% (90% fiducial interval, 1.32% to 2.66%), which differed significantly from the mean sevoflurane MAC determined with electrical stimulation, which was 4.24% (90% fiducial interval, 3.61% to 8.71%).
Conclusions and Clinical Relevance—Sevoflurane MAC in thick-billed parrots determined by mechanical stimulation was similar to values determined in chickens and mammals. Sevoflurane MAC determined by electrical stimulation was significantly higher, which suggested that the 2 types of stimulation did not induce similar results in thick-billed parrots.
Objective—To assess the effects of ketamine hydrochloride, propofol, or compounded thiopental sodium administration on intraocular pressure (IOP) and qualities of induction of and recovery from anesthesia in horses.
Animals—6 healthy adult horses.
Procedures—Horses were sedated with xylazine hydrochloride (0.5 mg/kg), and anesthesia was induced with guaifenesin followed by ketamine (2 mg/kg), propofol (3 mg/kg), or thiopental (4 mg/kg) in a crossover study with ≥ 1 week between treatments. For each horse, IOP in the right eye was measured with a handheld applanation tonometer before and after xylazine administration, at the time of recumbency, and every 3 minutes after induction of anesthesia until spontaneous movement was observed. Cardiorespiratory responses and venous blood measurements were recorded during anesthesia. Induction of and recovery from anesthesia were subjectively evaluated by investigators who were unaware of the anesthetic treatment of each horse. Data were analyzed via a repeated-measures ANOVA with Holm-Ŝidák post hoc comparisons.
Results—Compared with findings after xylazine administration (mean ± SD, 17 ± 3 mm Hg), thiopental decreased IOP by 4 ± 23%, whereas propofol and ketamine increased IOP by 8 ± 11% and 37 ± 16%, respectively. Compared with the effects of ketamine, propofol and thiopental resulted in significantly lower IOP at the time of recumbency and higher heart rates at 3 minutes after induction of anesthesia. No other significant differences among treatments were found.
Conclusions and Clinical Relevance—These findings support the use of thiopental or propofol in preference to ketamine for horses in which increases in IOP should be minimized.
To evaluate analgesic effects and complications associated with intraorbital insertion of an absorbable gelatin hemostatic sponge (AGHS) soaked with 1% ropivacaine solution following enucleation in dogs.
20 client-owned dogs undergoing enucleation.
Dogs were randomly assigned to receive an AGHS soaked with 1% ropivacaine solution (n = 10) or saline (0.9% NaCl) solution (control group; 10) inserted intraorbitally prior to skin closure following enucleation. Carprofen (2 mg/kg [0.9 mg/lb]) was administered SC once after orotracheal extubation and then PO twice a day for 5 days. During the postoperative recovery period, apparent pain level was scored at various points with a modified short-form Glasgow Composite Pain Scale (score range, 0 to 19), and methadone was administered for rescue analgesia if any score was ≥ 5. After dogs returned home, owners recorded their behavior and apparent pain level for the first 3 days following enucleation.
At extubation, the median (range) pain score was significantly higher in the control group (8 [2 to 14]) versus the ropivacaine group (3 [1 to 7]). A greater proportion of dogs in the control group received methadone (7/10 vs 1/10) and had crying or attention-seeking behavior on the first day following enucleation (7/10 vs 1/10). No complications were observed in either group.
CONCLUSIONS AND CLINICAL RELEVANCE
Addition of intraorbital insertion of a ropivacaine-soaked AGHS to the analgesic protocol for dogs undergoing enucleation provided better analgesia than was achieved without this treatment as measured immediately and the first day after surgery, with no noted adverse effects.
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.