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  • Author or Editor: Paulo V. Steagall x
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Abstract

OBJECTIVE

To determine the prevalence of and covariates associated with the oculocardiac reflex (OCR) occurring in dogs during enucleations.

SAMPLE

145 dogs that underwent enucleation at 2 veterinary teaching hospitals between January 2010 and June 2015.

PROCEDURES

Information was collected from the medical records of included dogs regarding age and body weight at hospital admission, breed (for classification of brachycephalic status), and whether they had received anticholinergic drugs or a retrobulbar nerve block (RNB) prior to enucleation. An OCR was considered to have occurred if there was a sudden decrease of ≥ 30% in heart rate from the baseline value (mean heart rate prior to the sudden decrease) during surgery in the absence of intraoperative administration of opioids or α2-adrenoceptor agonists. Associations were explored between the collected data and the prevalence of OCR by means of binomial logistic regression.

RESULTS

4.8% (7/145) of dogs had an OCR noted during enucleation. Dogs that received a preoperative RNB (n = 82) had significantly lower odds of an OCR being observed than dogs that received no preoperative RNB (OR, 0.12). No association with OCR was identified for age or brachycephalic conformation or for preoperative administration of anticholinergic drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings suggested that preoperative administration of an RNB, but not preoperative administration of anticholinergic drugs, was associated with a lower prevalence of OCR in dogs during enucleations.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To evaluate agreement between observers with different training and experience for assessment of postoperative pain and sedation in cats by use of a dynamic and interactive visual analog scale (DIVAS) and for assessment of postoperative pain in the same cats with a multidimensional composite pain scale (MCPS).

DESIGN Randomized, controlled, blinded study.

ANIMALS 45 adult cats undergoing ovariohysterectomy.

PROCEDURES Cats received 1 of 3 preoperative treatments: bupivacaine, IP; meloxicam, SC with saline (0.9% NaCl) solution, IP, (positive control); or saline solution only, IP (negative control). All cats received premedication with buprenorphine prior to general anesthesia. An experienced observer (observer 1; male; native language, Spanish) used scales in English, and an inexperienced observer (observer 2; female; native language, French) used scales in French to assess signs of sedation and pain. Rescue analgesia was administered according to MCPS scoring by observer 1. Mean pain and sedation scores per treatment and time point, proportions of cats in each group with MCPS scores necessitating rescue analgesia, and mean MCPS scores assigned at the time of rescue analgesia were compared between observers. Agreement was assessed by intraclass correlation coefficient determination. Percentage disagreement between observers on the need for rescue analgesia was calculated.

RESULTS Interobserver agreements for pain scores were good, and that for sedation scores was fair. On the basis of observer 1's MCPS scores, a greater proportion of cats in the negative control group received rescue analgesia than in the bupivacaine or positive control groups. Scores from observer 2 indicated a greater proportion of cats in the negative control group than in the positive control group required rescue analgesia but identified no significant difference between the negative control and bupivacaine groups for this variable. Overall, disagreement regarding need for rescue analgesia was identified for 22 of 360 (6.1%) paired observations.

CONCLUSIONS AND CLINICAL RELEVANCE Interobserver differences in assessing pain can lead to different conclusions regarding treatment effectiveness.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the isoflurane-sparing effects of lidocaine and fentanyl administered by constant rate infusion (CRI) during surgery in dogs.

Design—Randomized prospective study.

Animals—24 female dogs undergoing unilateral mastectomy because of mammary neoplasia.

Procedures—After premedication with acepromazine and morphine and anesthetic induction with ketamine and diazepam, anesthesia in dogs (n = 8/group) was maintained with isoflurane combined with either saline (0.9% NaCl) solution (control), lidocaine (1.5 mg/kg [0.68 mg/lb], IV bolus, followed by 250 μg/kg/min [113 μg/lb/min], CRI), or fentanyl (5 μg/kg [2.27 μg/lb], IV bolus, followed by 0.5 μg/kg/min [0.23 μg/lb/min], CRI). Positive-pressure ventilation was used to maintain eucapnia. An anesthetist unaware of treatment, endtidal isoflurane (ETiso) concentration, and vaporizer concentrations adjusted a nonprecision vaporizer to maintain surgical depth of anesthesia. Cardiopulmonary variables and ETiso values were monitored before and after beginning surgery.

Results—Heart rate was lower in the fentanyl group. Mean arterial pressure did not differ among groups after surgery commenced. In the control group, mean ± SD ETiso values ranged from 1.16 ± 0.35% to 1.94 ± 0.96%. Fentanyl significantly reduced isoflurane requirements during surgical stimulation by 54% to 66%, whereas the reduction in ETiso concentration (34% to 44%) observed in the lidocaine group was not significant.

Conclusions and Clinical Relevance—Administration of fentanyl resulted in greater isoflurane sparing effect than did lidocaine. However, it appeared that the low heart rate induced by fentanyl may partially offset the improvement in mean arterial pressure that would be expected with reduced isoflurane requirements.

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in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To evaluate antinociceptive effects of IV administration of hydromorphone alone or followed by buprenorphine or butorphanol to cats.

ANIMALS 6 healthy adult cats.

PROCEDURES In a randomized, blinded crossover design, cats received each of 4 treatments in which 2 IV injections were given 30 minutes apart: 2 of saline (0.9% NaCl) solution (Sal-Sal) or 1 each of hydromorphone HCl and saline solution (H-Sal), hydromorphone and buprenorphine HCl (H-Bupre), or hydromorphone and butorphanol tartrate (H-Butor). Skin temperature and thermal threshold were recorded before (baseline) and for 12 hours after the first injection. Percentage of maximum possible effect (%MPE) and thermal excursion (TE) were compared among treatments and measurement points.

RESULTS Compared with baseline values, skin temperature was higher from 0.75 to 2 hours after the first injection for H-Sal; at 0.5, 1, 3, and 4 hours for H-Bupre; from 0.5 to 3 hours for H-Butor; and from 0.5 to 1 hours for Sal-Sal. Thermal excursion was higher than at baseline from 0.25 to 2 hours for H-Sal and H-Bupre and 0.25 to 0.75 hours for H-Butor; %MPE increased from 0.25 to 2 hours for H-Sal, 0.25 to 3 hours for H-Bupre, and 0.25 to 0.75 hours for H-Butor. Results were similar for comparisons with Sal-Sal, except TE was greater for H-Sal versus Sal-Sal and TE and %MPE were greater for H-Bupre versus Sal-Sal from 0.25 to 1 hours after the first injection.

CONCLUSIONS AND CLINICAL RELEVANCE Butorphanol administration decreased the duration of antinociception achieved with hydromorphone administration in cats. This opioid interaction and its impact on pain management require additional investigation.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate pharmacokinetics of bupivacaine after IP administration to cats undergoing ovariohysterectomy.

ANIMALS 8 healthy cats.

PROCEDURES Anesthesia was induced with propofol and maintained with isoflurane. Buprenorphine (0.02 mg/kg, IV) and meloxicam (0.2 mg/kg, SC) were administered. A 20-gauge catheter was inserted into a jugular vein for blood sample collection. A ventral midline incision was made, and a solution of 0.5% bupivacaine (2 mg/kg) diluted with an equal volume of saline (0.9% NaCl) solution (final concentration, 0.25% bupivacaine) was injected into the peritoneal space over the right and left ovarian pedicles and caudal aspect of the uterus before ovariohysterectomy. Cats were monitored for signs of bupivacaine toxicosis. Venous blood samples (2 mL) were collected before (time 0) and 2, 5, 10, 15, 20, 30, 60, 120, and 240 minutes after bupivacaine administration. Plasma bupivacaine concentrations were determined with a liquid chromatography–tandem mass spectrometry method. Pharmacokinetic parameters were determined by data plotting followed by analysis with a noncompartmental model.

RESULTS No signs of bupivacaine toxicosis were observed. Maximum bupivacaine plasma concentration was 1,030 ± 497.5 ng/mL at a mean ± SD value of 30 ± 24 minutes after administration. Mean elimination half-life was 4.79 ± 2.7 hours. Mean clearance indexed by bioavailability and volume of distribution indexed by bioavailability were 0.35 ± 0.18 L•h/kg and 2.10 ± 0.84 L/kg, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE Intraperitoneal administration of bupivacaine resulted in concentrations that did not cause observable toxicosis. Studies to investigate analgesic effects for this technique in cats are warranted.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of a constant rate infusion of remifentanil, alone or in combination with ketamine, in healthy cats anesthetized with isoflurane.

Design—Randomized, controlled, clinical trial.

Animals—23 cats undergoing elective ovariohysterectomy.

Procedures—Cats were premedicated with acepromazine and morphine; anesthesia was induced with propofol and maintained with isoflurane. Cats were given constant rate infusions of remifentanil (20 μg/kg/h [9 μg/lb/h], IV; n = 8), remifentanil and ketamine (0.5 mg/kg [0.23 mg/lb], then 1.8 mg/kg/h [0.82 mg/lb/h], IV; 7), or crystalloid fluids (8). The anesthesiologist was blinded to treatment group, end-tidal isoflurane concentration, and vaporizer setting. Heart rate, systolic arterial blood pressure, respiratory rate, end-tidal partial pressure of CO2, temperature, and end-tidal isoflurane concentration were monitored; recovery scores were assigned.

Results—There were no significant differences among treatment groups with respect to age, body weight, surgery time, anesthesia time, time to extubation, recovery score, or cardiorespiratory variables. End-tidal isoflurane concentration was significantly reduced in cats given remifentanil and ketamine (mean ± SD, 0.63 ± 0.4%), compared with concentration in cats given crystalloid fluids (1.22 ± 0.5%) but not compared with concentration in cats given remifentanil alone (1.03 ± 0.4%). Compared with cats given crystalloid fluids, mean isoflurane requirement was reduced by 48.3% in cats given remifentanil-ketamine and 15.6% in cats given remifentanil alone.

Conclusions and Clinical Relevance—At the dosages administered, a constant rate infusion of remifentanil-ketamine resulted in a significant decrease in the isoflurane requirement in healthy cats undergoing ovariohysterectomy. However, significant differences in cardiovascular variables were not observed among treatment groups.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the antinociceptive effects of epidurally administered hydromorphone in conscious, healthy cats.

Animals—7 healthy adult cats.

Procedures—An epidural catheter was implanted in each cat. Thermal threshold (TT) was measured by increasing the temperature of a probe placed on the thorax and monitoring the cat's response. Mechanical threshold (MT) was measured by manually inflating a modified blood-pressure bladder affixed to a thoracic limb and monitoring the response. After the baseline TT and MT values were determined, hydromorphone (0.05 mg/kg) or an equal volume of saline (0.9% NaCl) solution was epidurally injected. The TT and MT were again measured at 15, 30, 45, 60, 120, 180, 240, 300, 360, and 480 minutes after injection.

Results—TT and MT did not change significantly from baseline values at any point after saline solution was administered. The MT and TT values were significantly higher than the baseline value at 15 minutes and at 120 and 180 minutes after hydromorphone administration, respectively. The MT and TT values after hydromorphone administration were also significantly different from those obtained at 30 minutes and at 15 minutes and 120 to 300 minutes, respectively, after administration of saline solution. No significant changes in skin temperature were detected after either treatment.

Conclusions and Clinical Relevance—Epidural administration of hydromorphone at a dosage of 0.05 mg/kg yielded thermal and some mechanical antinociceptive effects in cats, and no hyperthermia was detected. Additional studies of the antinociceptive effectiveness and duration of epidurally administered hydromorphone in clinical situations are required.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate adverse effects of long-term oral administration of carprofen, etodolac, flunixin meglumine, ketoprofen, and meloxicam in dogs.

Animals—36 adult dogs.

Procedures—Values for CBC, urinalysis, serum biochemical urinalyses, and occult blood in feces were investigated before and 7, 30, 60, and 90 days after daily oral administration (n = 6 dogs/group) of lactose (1 mg/kg, control treatment), etodolac (15 mg/kg), meloxicam (0.1 mg/kg), carprofen (4 mg/kg), and ketoprofen (2 mg/kg for 4 days, followed by 1 mg/kg daily thereafter) or flunixin (1 mg/kg for 3 days, with 4-day intervals). Gastroscopy was performed before and after the end of treatment.

Results—For serum γ-glutamyltransferase activity, values were significantly increased at day 30 in dogs treated with lactose, etodolac, and meloxicam within groups. Bleeding time was significantly increased in dogs treated with carprofen at 30 and 90 days, compared with baseline. At 7 days, bleeding time was significantly longer in dogs treated with meloxicam, ketoprofen, and flunixin, compared with control dogs. Clotting time increased significantly in all groups except those treated with etodolac. At day 90, clotting time was significantly shorter in flunixin-treated dogs, compared with lactose-treated dogs. Gastric lesions were detected in all dogs treated with etodolac, ketoprofen, and flunixin, and 1 of 6 treated with carprofen.

Conclusions and Clinical Relevance—Carprofen induced the lowest frequency of gastrointestinal adverse effects, followed by meloxicam. Monitoring for adverse effects should be considered when nonsteroidal anti-inflammatory drugs are used to treat dogs with chronic pain.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of increasing doses of remifentanil hydrochloride administered via constant rate infusion (CRI) on the minimum alveolar concentration (MAC) of isoflurane in cats.

Animals—6 healthy adult cats.

Procedures—For each cat, 2 experiments were performed (2-week interval). On each study day, anesthesia was induced and maintained with isoflurane; a catheter was placed in a cephalic vein for the administration of lactated Ringer's solution or remifentanil CRIs, and a catheter was placed in the jugular vein for collection of blood samples for blood gas analyses. On the first study day, individual basal MAC (MACBasal) was determined for each cat. On the second study day, 3 remifentanil CRIs (0.25, 0.5, and 1.0 μg/kg/min) were administered (in ascending order); for each infusion, at least 30 minutes elapsed before determination of MAC (designated as MACR0.25, MACR0.5, and MACR1.0, respectively). A 15-minute washout period was allowed between CRIs. A control MAC (MACControl) was determined after the last remifentanil infusion.

Results—Mean ± SD MACBasal and MACControl values at sea level did not differ significantly (1.66 ± 0.08% and 1.52 ± 0.21%, respectively). The MAC values determined for each remifentanil CRI did not differ significantly. However, MACR0.25, MACR0.5, and MACR1.0 were significantly decreased, compared with MACBasal, by 23.4 ± 7.9%, 29.8 ± 8.3%, and 26.0 ± 9.4%, respectively.

Conclusions and Clinical Relevance—The 3 doses of remifentanil administered via CRI resulted in a similar degree of isoflurane MAC reduction in adult cats, indicating that a ceiling effect was achieved following administration of the lowest dose.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the thermal antinociceptive effects and duration of action of nalbuphine decanoate after IM administration to Hispaniolan Amazon parrots (Amazona ventralis).

Animals—10 healthy adult Hispaniolan Amazon parrots of unknown sex.

Procedures—Nalbuphine decanoate (33.7 mg/kg) or saline (0.9% NaCl) solution was administered IM in a randomized complete crossover experimental design (periods 1 and 2). Foot withdrawal threshold to a noxious thermal stimulus was used to evaluate responses. Baseline thermal withdrawal threshold was recorded 1 hour before drug or saline solution administration, and thermal foot withdrawal threshold measurements were repeated 1, 2, 3, 6, 12, 24, 48, and 72 hours after drug administration.

Results—Nalbuphine decanoate administered IM at a dose of 33.7 mg/kg significantly increased thermal foot withdrawal threshold, compared with results after administration of saline solution during period 2, and also caused a significant change in withdrawal threshold for up to 12 hours, compared with baseline values.

Conclusions and Clinical Relevance—Nalbuphine decanoate increased the foot withdrawal threshold to a noxious thermal stimulus in Hispaniolan Amazon parrots for up to 12 hours and provided a longer duration of action than has been reported for other nalbuphine formulations. Further studies with other types of nociceptive stimulation, dosages, and dosing intervals as well as clinical trials are needed to fully evaluate the analgesic effects of nalbuphine decanoate in psittacine birds.

Full access
in American Journal of Veterinary Research