AAHA/AAFP pain management guidelines for dogs & cats

Pain management in dogs and cats has undergone a dramatic evolution in the past decade. Current approaches focus on anticipation and prevention of pain, as well as both pharmacologic and nonpharmacologic management techniques. The veterinary team plays an essential role in educating pet owners about recognizing and managing pain in their pets.     

Evaluation of opioid receptors in synovial membranes of horses

OBJECTIVE: To evaluate mu-opioid receptors in synovial membranes of horses and determine whether these receptors are up-regulated in nerve endings during inflammation. SAMPLE POPULATION: Synovial tissue obtained from 39 client-owned horses during arthroscopy and 14 research horses during necropsy; brain and synovial tissues were obtained during necropsy from 1 horse, and control tissues were obtained from a mouse. PROCEDURE: Horses were classified into 7 groups on the basis of histologically determined degree of inflammation. Binding of primary rabbit antibody developed against mu-opioid receptors in equine synovial tissue was studied, using western blot analysis. Synovial membranes were tested for mu-opioid receptors by immunohistochemical staining, using a diaminobenzidine-cobalt chloride chromogen. Homogenates of synovial membranes were evaluated by use of radioligand binding. RESULTS: Examination of western blots of equine thalamus revealed that rabbit antibody developed against mu-opioid receptors yielded a band (molecular weight, 55 kd) that corresponded with that of other opioid receptors. Use of immunohistochemical staining of synovial tissue revealed considerable staining in the proliferative lining layer and in regions surrounding vascular structures. Specific radioligand binding of tissue homogenates was found in all groups. We did not detect significant differences in binding between horses with inflammation and horses without inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: Results of immunohistochemical analysis and radioligand binding of tissue homogenates suggest that there are opioid receptors in synovial membranes of horses. Our results support the practice of intra-articular administration of opioids to relieve pain after arthroscopic surgery in horses.     

Use of low doses of ketamine administered by constant rate infusion as an adjunct for postoperative analgesia in dogs

OBJECTIVE: To compare indicators of postoperative pain and behavior in dogs with and without a low-dose ketamine infusion added to usual perioperative management. DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: 27 dogs undergoing forelimb amputation. PROCEDURE: Dogs were anesthetized with glycopyrrolate, morphine, propofol, and isoflurane. Thirteen dogs were treated with ketamine IV, as follows: 0.5 mg/kg (0.23 mg/lb) as a bolus before surgery, 10 microg/kg/min (4.5 microg/lb/min) during surgery, and 2 microg/kg/min (0.9 microg/lb/min) for 18 hours after surgery. Fourteen dogs received the same volume of saline (0.9% NaCl) solution. All dogs received an infusion of fentanyl (1 to 5 microg/kg/h [0.45 to 2.27 pg/lb/h]) for the first 18 hours after surgery. Dogs were evaluated for signs of pain before surgery, at the time of extubation, and 1, 2, 3, 4, 12, and 18 hours after extubation. Owners evaluated their dogs' appetite, activity, and wound soreness on postoperative days 2, 3, and 4. RESULTS: Dogs that received ketamine infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day 3 than dogs that received saline solution infusions. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that perioperative administration of low doses of ketamine to dogs may augment analgesia and comfort in the postoperative surgical period.     

Evaluation of xylazine and ketamine for total intravenous anesthesia in horses

OBJECTIVE: To evaluate the use of xylazine and ketamine for total i.v. anesthesia in horses. ANIMALS: 8 horses. PROCEDURE: Anesthetic induction was performed on 4 occasions in each horse with xylazine (0.75 mg/kg, i.v.), guaifenesin (75 mg/kg, i.v.), and ketamine (2 mg/kg, i.v.). Intravenous infusions of xylazine and ketamine were then started by use of 1 of 6 treatments as follows for which 35, 90, 120, and 150 represent infusion dosages (microg/kg/min) and X and K represent xylazine and ketamine, respectively: X35 + K90 with 100% inspired oxygen (O2), X35 + K120-(O2), X35 + K150-(O2), X70 + K90-(O2), K150-(O2), and X35 + K120 with a 21% fraction of inspired oxygen (ie, air). Cardiopulmonary measurements were performed. Response to a noxious electrical stimulus was observed at 20, 40, and 60 minutes after induction. Times to achieve sternal recumbency and standing were recorded. Quality of sedation, induction, and recovery to sternal recumbency and standing were subjectively evaluated. RESULTS: Heart rate and cardiac index were higher and total peripheral resistance lower in K150-(O2) and X35 + K120-air groups. The mean arterial pressure was highest in the X35 + K120-air group and lowest in the K150-(O2) group (125 +/- 6 vs 85 +/- 8 at 20 minutes, respectively). Mean Pa(O2) was lowest in the X35 + K120-air group. Times to sternal recumbency and standing were shortest for horses receiving K150-(O2) (23 +/- 6 minutes and 33 +/- 8 minutes, respectively) and longest for those receiving X70 + K90-(O2) (58 +/- 28 minutes and 69 +/- 27 minutes, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Infusions of xylazine and ketamine may be used with oxygen supplementation to maintain 60 minutes of anesthesia in healthy adult horses.     

Multicenter, randomized controlled trial of pain-related behaviors following routine neutering in dogs

OBJECTIVE: To evaluate the degree of postoperative pain in dogs undergoing elective castration or ovariohysterectomy (OHE); determine whether an association exists between surgeon experience, incision length, or surgery duration and degree of postoperative pain; and determine whether analgesic treatment decreases expression of postoperative pain behaviors. DESIGN: Randomized controlled clinical trial. ANIMALS: 426 client-owned dogs undergoing OHE or castration. PROCEDURES: Dogs underwent OHE or castration performed by an experienced veterinarian or a fourth-year veterinary student. Dogs were randomly assigned to 1 of 4 treatment groups: no perioperative analgesic treatment (n = 44), preoperative administration of morphine (144), preoperative administration of nalbuphine (119), and postoperative administration of ketoprofen (119). Dogs were evaluated while in the hospital before anesthesia and for 4 hours after surgery and once a day at home for 3 days after surgery. RESULTS: Dogs in all 4 groups had significant increases in overall pain scores after surgery, compared with baseline scores. There were significant differences among groups, with control dogs having significantly higher increases in overall pain scores than dogs in the other groups. Factors that did not influence the frequency or severity of pain-related behaviors included breed, individual hospital, anesthetic induction protocol, surgeon experience, and duration of surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that dogs expressed behaviors suggestive of pain following OHE and castration, that analgesic treatment mitigated the expression of pain-related behaviors, and that surgeon experience and surgery duration did not have any effect on expression of pain-related behaviors.     

Correlations between acute radiation scores and pain scores in canine radiation patients with cancer of the forelimb

Objective To determine whether there is a correlation between skin acute radiation score (ARS) and pain scores and to determine if skin ARSs can be used to predict future pain scores and increased need for analgesia in dogs undergoing radiation therapy for cancer of the forelimb. Study design Prospective observational study. Animals Seven middle‐aged dogs of various breeds with cancer of the forelimb. Methods Each neoplasm was surgically removed and a histologic diagnosis was obtained. Curative intent radiation therapy was initiated 2½–4½ weeks after surgery. Curative intent radiation therapy was delivered as prescribed. Two trained observers scored the dogs using a visual analog pain scale (VAS), Glasgow composite measure of pain scale, short form (GCMPS) and skin ARS prior to each day’s therapy. Daily scores were averaged and scatter plots were developed. Generalized estimating equation regressions were used to calculate standard error, 95% confidence interval, and p‐values for each relationship. Confidence and prediction bands were plotted. Results A statistically significant correlation between skin ARS and VAS and GCMPS pain scores was identified indicating that as the skin ARS increased so did the pain scores. A general correlation between VAS and GCMPS scores was observed. Early (fraction days 1–6) GCMPS scores were significantly influenced by anxiety behavior unrelated to pain. Skin ARS was found to predict precisely current and future presence of pain, but could only predict a range of potential future pain scores based on the pain management approach in use during this study. Conclusions Skin ARS can provide valuable information for initiating preemptive analgesia and intensifying pain management during curative intent radiation therapy. Daily pain scoring with an acceptable pain scale should be used in conjunction with the skin ARS to improve patient pain management. Clinical relevance Pain is an anticipated consequence of curative intent radiation therapy. Understanding the correlation between pain and skin ARS may facilitate more effective pain management.