The post-operative analgesic effects of epidurally administered morphine and transdermal fentanyl patch after ovariohysterectomy in dogs

Challenges with Assessing and Treating Pain in Research Primates: A Focused Survey and Literature Review

Research primates may undergo surgical procedures making effective pain management essential to ensure good animal welfare and unbiased scientific data. Adequate pain mitigation is dependent on whether veterinarians, technicians, researchers, and caregivers can recognize and assess pain, as well as the availability of efficacious therapeutics. A survey was conducted to evaluate primate veterinary approaches to pain assessment and alleviation, as well as expressed challenges for adequately managing primate pain. The survey (n = 93 respondents) collected information regarding institutional policies and procedures for pain recognition, methods used for pain relief, and perceived levels of confidence in primate pain assessment. Results indicated that 71% (n = 60) of respondents worked at institutions that were without formal experimental pain assessment policies. Pain assessment methods were consistent across respondents with the majority evaluating pain based on changes in general activity levels (100%, n = 86) and food consumption (97%, n = 84). Self-reported confidence in recognizing and managing pain ranged from slightly confident to highly confident, and there was a commonly expressed concern about the lack of objective pain assessment tools and science-based evidence regarding therapeutic recommendations of analgesics for research primates. These opinions correspond with significant gaps in the primate pain management literature, including limited specific pharmacokinetic data and efficacy testing for commonly used analgesics in research primate species as well as limited research on objective and specific measures of pain in research primates. These results demonstrate that there are inconsistencies in institutional policies and procedures surrounding pain management in research primates and a lack of objective pain assessment methods. Demonstrating the gaps and challenges in primate pain management can inform guideline development and suggest areas for future research.

Randomized clinical trial comparing outcomes after fentanyl or ketamine-dexmedetomidine analgesia in thoracolumbar spinal surgery in dogs

Background

Opioids are widely used for perioperative pain control in dogs undergoing spinal surgery, but alternatives may be required because data suggest that opioids exacerbate inflammation in the injured spinal cord and veterinary access to opioids may become more restricted in the future.

Objectives

To compare recovery of ambulation and other functions between spinal cord‐injured dogs receiving peri‐operative fentanyl and those receiving a ketamine‐dexmedetomidine combination.

Animals

A total of 102 client‐owned dogs undergoing decompressive surgery for thoracolumbar intervertebral disc herniation.

Methods

Randomized clinical trial. Dogs were randomized 1:1 to fentanyl or a ketamine‐dexmedetomidine combination for intra and postoperative analgesia. Primary outcome was time to recovery of ambulation; secondary outcomes were the postoperative Colorado Acute Pain Scale, the short‐form Glasgow Composite Measure Pain Scale, time to recovery of voluntary urination and time to unassisted eating.

Results

No difference was found in time to recovery of ambulation between groups (adjusted sub‐hazard ratio, 0.83; 95% confidence interval [CI], 0.55‐1.24; P = .36) or in pain scores (Colorado: χ² = 14.74; P = .32; Glasgow: χ² = 6.61; P = .76). Differences in time to recovery of eating and urination were small but favored ketamine‐dexmedetomidine (adjusted odds ratios, 3.31; 95% CI, 1.53‐7.16; P = .002 and 2.43; 95% CI, 1.00‐5.96; P = .05, respectively).

Conclusions and Clinical Importance

There was no evidence that, at the doses used, fentanyl impaired ambulatory outcome after surgery for thoracolumbar intervertebral disc herniation in dogs. Pain control appeared similar between groups. Secondary outcomes suggested minor benefits associated with ketamine‐dexmedetomidine. The ketamine‐dexmedetomidine combination appears to be a reasonable alternative to peri‐operative opioids.

Fentanyl patch versus tramadol for the control of postoperative pain in canine ovariectomy and mastectomy

OBJECTIVES

The purpose of the present study was to evaluate the postoperative analgesic efficacy of fentanyl patches versus subcutaneous tramadol after canine ovariectomy, with and without unilateral mastectomy.

MATERIALS AND METHODS

A total of 40 female dogs were included in the present study, all of which were domesticated, healthy and 4-12 years of age. The animals were divided into four groups (n = 10 per group) based on the surgery and the analgesic protocol used: the TO group only underwent ovariectomy, and received postoperative tramadol; the TM group underwent both ovariectomy and mastectomy, and received postoperative tramadol; the FO group only underwent ovariectomy, and received fentanyl patches; and the FM group underwent both ovariectomy and mastectomy, and received fentanyl patches. Postoperative pain was evaluated every 4 h for 24 h using a numeric analogue scale (NAS) and a modified Glasgow Composite Measure Pain Scale Short Form (CMPS-SF).

RESULTS

The results of the present study showed that patients in all four groups tolerated postoperative surgical stress well. Analysis of variance for repeated measures did not show significant differences in the NAS scores and in Glasgow CMPS-SF between groups in terms of pain scores or rescue analgesia.

CLINICAL SIGNIFICANCE

These results indicated that the analgesic effect of the fentanyl patch was similar to that of subcutaneous (SC) tramadol in female dogs after ovariectomy, with and without unilateral mastectomy, suggesting that the fentanyl patch may represent a valid supplementary tool for the control of postoperative pain in animals after surgery.

Comparison of the analgesic effects of morphine and tramadol after tumor surgery in dogs

BACKGROUND

Pain thresholds may differ between animal species. It may even vary among individuals of the same species. Therefore, assessing pain in animals is challenging.

AIMS

The objective of the present study was to compare the analgesic effects of tramadol with morphine.

METHODS

The study was carried out on randomly selected 20 dogs with tumors in different breeds and gender. After induction of anesthesia with propofol, dogs were intubated, and anesthesia was maintained with sevoflurane. Intravenous fentanyl citrate was used for intraoperative analgesia after stabilization of the anesthesia. When the tumors were surgically removed and the operation was completed, dogs were divided into two groups to give the postoperative analgesic agent. The first 10 dogs to be investigated were identified as the morphine group and the second 10 dogs as the tramadol group. Postoperative pain scores, heart rates, respiratory rates, and body temperatures were recorded at 0, 4, 8, 12, 16, 20, and 24 hours after the operation.

RESULTS

Pain scores were lower in the morphine group than in the tramadol group during all postoperative processes.

CONCLUSION

As a result, it was determined that tramadol has immediate analgesic effects than morphine; however, morphine provides better analgesia than tramadol.

Comparison of the effects of morphine-lidocaine-ketamine and fentanyl-lidocaine-ketamine combinations administered as constant rate infusions on postprocedure rectal temperature in dogs

OBJECTIVE

To compare the effects of morphine-lidocaine-ketamine (MLK) and fentanyl-lidocaine-ketamine (FLK) combinations administered as constant rate infusions (CRIs) during and after veterinary procedures on postprocedure rectal temperature in dogs.

ANIMALS

32 clinically normal client-owned dogs undergoing nonemergent procedures.

PROCEDURES

Dogs were randomly assigned to receive an MLK or FLK combination (16 dogs/group). During the procedure, each dog received 2% lidocaine hydrochloride (1 mg/kg/h; both groups), ketamine hydrochloride (0.6 mg/kg/h; both groups), and morphine (0.36 mg/kg/h; MLK group) or fentanyl (4 μg/kg/h; FLK group) via CRI for analgesia; esophageal temperature was maintained at 37° to 39°C. At extubation, each drug dose in each assigned combination was halved and administered (via CRI) for 12 additional hours for postprocedure analgesia. Rectal temperature and other data were recorded at baseline (prior to administration of premedicants), extubation (0 hours), and 0.5, 1.5, 3, 6, and 12 hours thereafter.

RESULTS

Mean postprocedure rectal temperature was significantly lower at each postextubation time point for the MLK group, compared with corresponding values for the FLK group. Compared with the baseline value, mean postprocedure rectal temperature was significantly lower at 0, 0.5, 1.5, and 3 hours for the FLK group and at all postprocedure time points for the MLK group. Hypothermia (rectal temperature < 37°C) was detected at ≥ 1 postprocedure time point more often in dogs in the MLK group (9/16) than in the FLK group (1/16).

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs that received an MLK combination for analgesia during and after a veterinary procedure developed hypothermia more commonly than did dogs that received an FLK combination under similar conditions.

Anaesthetic management and complications of canine adrenalectomies: 41 cases (2007-2017)

Little information is available about the management of adrenalectomies in veterinary anaesthesia. The aim of this study was to describe the anaesthetic techniques, the complication rate and outcome of these cases. Data were collected retrospectively from patients' records. Descriptive statistics were performed with Student's t-tests and Chi-square tests where appropriate. Forty-one cases were included. The mean age was 124.7 ± 29.4 months and the median body weight was 23.1 kg (5.3-69 kg). Carcinoma was the most common diagnosis (34.1%). Premedication was most commonly achieved with methadone alone (70.7%) IV. Propofol was the most common induction agent (39%). An infusion of opioids (80.4%) and an epidural injection of morphine (70.7%) were the most common analgesic techniques. Hypotension was the most common complication observed (51.2%). The mortality rate was 14.6%. The lowest recorded oesophageal temperature was statistically associated with the incidence of haemorrhage (P = 0.025). The invasion of the vena cava (P = 0.001) was significantly associated with haemorrhagic complications. The survival rate was better when patients received hydrocortisone intra-operatively (P = 0.026). This study highlights some possible association between the anaesthetic management and the outcome of the procedure.

A systematic review of analgesia practices in dogs undergoing ovariohysterectomy

Aim

This was a systematic review conducted to evaluate the analgesic drugs and techniques used in the management of pain in dogs undergoing ovariohysterectomy.

Materials and Methods

Systematic searches in PubMed, Google Scholar, and ScienceDirect were conducted for peer-reviewed articles written in English and published from 1995 to 2015. The key search words were dogs, ovariohysterectomy, pain, and analgesics. This was followed by a manual search of the references within the primary data sources. Inclusion and exclusion of studies and data extraction were performed independently by two reviewers. All randomized studies evaluating the effects of analgesics during ovariohysterectomy in dogs were included.

Results

A total of 31 trials met the criteria and were, therefore, included in the study. Data on the type of analgesic drugs used, the technique of administration, and the need for rescue analgesia were extracted from the papers. Individual analgesic protocols were used in 83.9% of the studies compared to multimodal drug therapy, which was used in 16.1% of the studies. Opioids were used in 39.0% of studies, nonsteroidal anti-inflammatory drugs (NSAIDs) in 19.4%, a combination of NSAIDs and opioids in 19.4%, local analgesics in 6.5%, and acupuncture in 3.2% of the studies. Drug administration was done using three approaches that included pre-operative (64.5%), post-operative (22.6%) as well as combined pre- and post-operative approach (12.9%). In 77.4% of the studies, administration of analgesics was done once, while in 12.9%, it was done as a 72-h post-operative course. 24-h and 48-h courses of post-operative pain therapy were done in 6.5% and 3.2% of the studies, respectively. About 57% of the dogs in the control groups required rescue analgesia as compared to 21.6% in the single and 11.3% in multimodal drug therapy groups. The requirement for rescue analgesics was highest in dogs treated using acupuncture (43.8%) and lowest in dogs treated using NSAID-opioid combination (8.6%). Fewer dogs among those that received pain medication preoperatively and postoperatively required rescue analgesia compared to those in groups given drugs before and after surgery only. More dogs (26.4%) among those given analgesics only once postoperatively required rescue analgesia as compared to those that received analgesics daily for 72 h (4.4%).

Conclusions

This study provides evidence that opioids are the mainstream analgesic drugs used in managing acute post-operative pain in dogs' post-ovariohysterectomy. In addition, multimodal drug therapy, particularly, NSAID-opioids combination is more effective for pain management than single drug administration. Administering analgesics both before and after surgery is associated with better outcomes and so is a protracted course of post-operative pain therapy. Although these practices should be encouraged, controlled studies should be conducted to conclusively determine the best practices for pain management in dogs undergoing ovariohysterectomy.

Epidural anesthesia and analgesia in small animal practice: An update

Epidural anesthesia is a commonly performed technique in both human and veterinary medicine. The technique is relatively simple following appropriate training and provides anesthesia and analgesia for acute and chronic pain. Several drug combinations have been administered by this route with variable success and duration. Multiple techniques to guide or confirm correct epidural needle placement are discussed in this article, as well as anatomical features of the epidural space, effect of drug volume and concentration, and adverse effects of the technique in small animal practice. This article is not an exhaustive review of the literature, but an update of some new findings over the last decade.

Effect of laparotomy on the pituitary-adrenal axis in dogs

OBJECTIVE To assess effects of major abdominal surgery on serum cortisol and aldosterone and plasma canine ACTH (cACTH) concentrations. ANIMALS 39 healthy dogs undergoing laparotomy during veterinary student surgical laboratories. PROCEDURES Blood samples were obtained before and at completion of surgery. Serum cortisol and aldosterone and plasma cACTH concentrations were measured by use of validated radioimmunoassays. Changes in concentrations (postoperative concentration minus preoperative concentration) were calculated. Data were analyzed by use of the Wilcoxon signed rank test, Pearson correlation analysis, and Mann-Whitney rank sum test. RESULTS Cortisol, aldosterone, and cACTH concentrations increased significantly from before to after surgery. Although cortisol and aldosterone concentrations increased in almost all dogs, cACTH concentrations decreased in 6 of 32 (19%) dogs. All dogs had preoperative cortisol concentrations within the reference range, but 24 of 39 (62%) dogs had postoperative concentrations above the reference range. A correlation between the change in cACTH concentration and the change in cortisol concentration was not detected. CONCLUSIONS AND CLINICAL RELEVANCE Laparotomy caused a significant increase in serum cortisol and aldosterone concentrations. In most dogs, but not all dogs, plasma cACTH concentrations increased. Lack of correlation between the change in cACTH concentration and the change in cortisol concentration suggested that increased postoperative cortisol concentrations may have been attributable to ACTH-independent mechanisms, an early ACTH increase that caused a sustained cortisol release, or decreased cortisol clearance. Further studies are indicated to evaluate the effects of various anesthetic protocols and minimally invasive surgical techniques on the stress response.

A case of acute postoperative transitory sialadenosis of the submandibular glands in a healthy dog

A 1-year-old healthy female cross-breed dog, weighing 4.5 kg, was scheduled for elective neutering. Fentanyl (5 µg/kg) and propofol (4 mg/kg) were administered intravenously (IV) to induce anesthesia, which was maintained with isoflurane and a constant fentanyl infusion rate (10 µg/kg/hr). During the recovery from the anesthesia, the presence of bilateral dense submandibular masses was recognized, as was the excessive secretion of saliva. An ultrasound examination was performed and revealed bilateral abnormally-diffused enlargement of the submandibular salivary glands. A cytology examination was conducted, and no signs of abnormality were found. The size of the swellings subsequently diminished, completely subsiding after 2 hr, as did the hyper-salivation. To the authors' knowledge, this represents the first case report of an acute transient swelling of submandibular glands after general anesthesia in a dog.

Postoperative Analgesia Provided by Liposomal Hydromorphone in Client-Owned Dogs Undergoing Limb Amputation

The analgesic efficacy of liposomal hydromorphone (LE-hydro) was tested in dogs undergoing limb amputation. The positive controls (n = 10) received subcutaneous (SQ) hydromorphone (0.2 mg/kg) and 1.5 mL of blank liposomes before surgery; fentanyl continuous rate infusion (CRI), 5-10 μg/kg/hr IV, during and for 24 hr after surgery; and a fentanyl patch at extubation. The negative controls (n = 7) received SQ hydromorphone (0.2 mg/kg) and 1.5 mLs of blank liposomes SQ before surgery, fentanyl CRI (5-10 μg/kg/hr IV) during surgery but stopped at extubation, and a fentanyl patch at extubation. The test group (n = 11) received 3 mg/kg of LE-hydro and 1.5 mL of saline SQ before surgery, 1.5 mL of saline SQ, and a saline CRI during surgery. All groups received a bupivacaine block in the limb prior to amputation and carprofen prior to surgery. Treatment failures, pain scores, opioid side effects, heart rate, respiratory rate, temperature, and client-reported pain and side effects were evaluated. There were three treatment failures in the positive control (3/10) and test groups (3/11). Negative controls had seven treatment failures (7/7). Side effects for all three groups were within expected limits. LE-hydro provides postoperative analgesia equivalent to fentanyl CRI in dogs undergoing limb amputation.

Evaluation of the effects of methadone and tramadol on postoperative analgesia and serum interleukin-6 in dogs undergoing orthopaedic surgery

BACKGROUND

Acute postsurgical pain is of great interest due to potential risk of becoming chronic if not treated properly, worsening patient's recovery and quality of life. Twenty-eight dogs with ruptured cruciate ligaments were divided into three groups that received intramuscular injections of 4 mg/kg of tramadol (TRA), 0.5 mg/kg of methadone (MET0.5), or 0.7 mg/kg of methadone (MET0.7). Physiological parameters (heart and respiratory rates and blood pressure) were evaluated at specified times: baseline (TBL), 1 (T1), 2 (T2), 4 (T4), 6 (T6), and 24 (T24) hours after premedication. Pain scores were described by visual analogue scale (VAS), modified Glasgow Composite, and Colorado University Acute Pain scales. Blood samples for measurement of interleukin (IL)-6 were collected at TBL, T1, T6, and T24. This was a prospective, randomised investigation to evaluate the efficacy of tramadol and methadone as premedications in dogs undergoing osteotomies.

RESULTS

There were no statistically significant differences between groups with respect to age, weight, gender, surgery time, and time to extubation. Heart rate, respiratory rate, and blood pressure values were maintained within acceptable ranges, and a reduction was observed at T2 in MET0.5 and MET0.7 compared with TBL. Increases in VAS scores were observed in TRA at T4 compared with TBL, T1, and T24 and between T1 and T6 (p < 0.001). In MET0.5, there was significant increase in VAS score at T4 compared with T1 (p < 0.001). TRA and MET0.5 showed significantly higher mean ± SD VAS scores (3.4 ± 2.5 and 2.5 ± 2.6, respectively) than MET0.7 (1.1 ± 1.5) at T4 (p < 0.001). TRA showed greater demand of rescue analgesia (four animals in T4 and two in T6) (p < 0.037). There were no statistically significant differences in sedation scores, Colorado Scale scores, or interleukin levels between groups and time points.

CONCLUSIONS

Methadone given as premedication in doses of 0.7 mg/kg was better at controlling pain compared with lower doses and tramadol. However, dosage increases, administered as rescue analgesia, promoted adequate pain control even in tramadol group. Influence of these analgesics on IL-6 release could not be demonstrated, but significant levels were not found.

Effects of opioids on phagocytic function, oxidative burst capacity, cytokine production and apoptosis in canine leukocytes

Opioids alter immune and apoptotic pathways in several species. They are commonly used in companion animals affected with infectious and/or inflammatory disease, but the immunomodulatory and apoptotic effects of these drugs in dogs are relatively unknown. The aim of the present study was to evaluate the effects of morphine, buprenorphine and fentanyl on canine phagocyte function, oxidative burst capacity, leukocyte cytokine production, and lymphocyte apoptosis. Blood from six healthy adult dogs was incubated in the presence or absence of morphine (200 ng/mL), buprenorphine (10 ng/mL) or fentanyl (10 ng/mL) for 3 h (phagocytic function; cytokine production) or 8 h (apoptosis). Neutrophil phagocytosis of opsonized Escherichia coli, respiratory burst capacity after stimulation with opsonized E. coli or phorbol 12-myristate 13-acetate (PMA), and Annexin V-FITC staining of apoptotic lymphocytes were evaluated using flow cytometry. Leukocyte production of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 was assessed after incubation with lipopolysaccharide (LPS), lipoteichoic acid (LTA) or peptidoglycan. Morphine promoted a more intense respiratory burst. Morphine, buprenorphine and fentanyl all promoted LPS- or LTA-induced TNF-α and IL-10 production. However, the opioids tested did not alter TNF-α:IL-10 ratios. Morphine, buprenorphine and fentanyl all inhibited neutrophil apoptosis, an effect that was not concentration dependent in nature. These data indicate that opioids alter immune and apoptotic pathways in dogs. The possible effects of opioids on immune and cellular responses should be considered when designing studies and interpreting outcomes of studies involving administration of opioids in dogs.

Evaluation of risk factors for development of corneal ulcer after nonocular surgery in dogs: 14 cases (2009-2011)

OBJECTIVE

To evaluate the prevalence of and risk factors for development of corneal ulcers after nonocular surgery performed with general anesthesia in dogs.

DESIGN

Retrospective case-control study.

ANIMALS

14 dogs with development of corneal ulcers after nonocular surgery and 718 control dogs.

PROCEDURES

Medical records of dogs evaluated at the Veterinary Medical Teaching Hospital of Seoul National University from January 2009 to June 2011 were reviewed for assessment of risk factors for development of corneal ulcers.

RESULTS

Among the 732 reviewed cases, 14 (1.9%) dogs of 6 breeds developed a corneal ulcer after nonocular surgery. Duration of anesthesia was significantly longer in dogs with ulcers than dogs without ulcers. The number of medications received and procedures performed were also significantly higher in dogs with ulcers than dogs without ulcers. Dogs with a small skull (OR, 8.59; 95% confidence interval [CI], 1.04 to 70.90) and dogs that received neurosurgery (OR, 21.12; 95% CI, 5.77 to 77.25) were more susceptible to development of corneal ulcers. Also, postoperative application of a fentanyl patch was a risk factor for development of corneal ulcers (OR, 4.53; 95% CI, 1.05 to 19.60).

CONCLUSIONS AND CLINICAL RELEVANCE

Several risk factors were identified for development of corneal ulcers after nonocular surgery was performed with general anesthesia in dogs. Perioperative eye protection strategies and postoperative ophthalmic examination are needed to reduce the occurrence of corneal ulcers and their progression, especially for high-risk dogs and procedures.

A comparison of extradural tramadol and extradural morphine for postoperative analgesia in female dogs undergoing ovariohysterectomy

PURPOSE: To compare the postoperative analgesic effects of the extradural tramadol or morphine in female dogs undergoing ovariohysterectomy. METHODS: Sixteen female dogs were randomly assigned to two groups of eight animals each and received morphine (0.1mg kg-1 M group) or tramadol (2mg kg-1 T group). The pre-anesthetic medication was intravenously (iv) acepromazine (0.05mg kg-1). Anesthesia was induced with propofol (4mg kg-1iv) and maintained with isoflurane. The degree of analgesia was evaluated using a numerical rating scale that included physiologic and behavior variables. Dogs were scored at one, three, six and 12 hours after surgery by one blinded observer. Dogs were treated with morphine (0.5mg kg-1) if their scores were >6. Serum cortisol was measured before the pre-anesthetic medication was administered (basal), at the time of the ovarian pedicle clamping (T0), and at 1 (T1), 6 (T6) and 12 (T12) hours postoperative. RESULTS: The pain score did not differ between morphine and tramadol treatments. Rescue analgesia was administered to one dog in the T treatment group. Serum cortisol did not differ between treatments. CONCLUSION: The extradural administration of morphine or tramadol is a safe and effective method of inducing analgesia in female dogs undergoing ovariohyterectomy.