Analgesia In Dogs Research Articles

Development of a retrobulbar injection technique for ocular surgery and analgesia in dogs

To develop and compare 3 techniques for retrobulbar injection of local anesthetic agents for ocular surgery and analgesia in dogs. Prospective study. 17 dogs (including 9 cadavers). Inferior-temporal palpebral (ITP), perimandibular, and combined superior-inferior peribulbar injection techniques were compared by assessing the distribution of latex after injection into the orbits of 5 canine cadavers; magnetic resonance imaging (MRI) evaluation of the distribution of contrast agent after injection in the retrobulbar space of 4 canine cadavers; and assessment of the efficacy and MRI evaluation of the anatomic distribution of injections of a lidocainecontrast agent mixture in 4 anesthetized, nonrecovery dogs. By use of the preferred technique (ITP), the ocular effects of lidocaine anesthesia were evaluated in 4 dogs; during a 2-week period after treatment, dogs underwent ophthalmic examination, Schirmer tear testing (STT), intraocular pressure (IOP) measurement, and Cochet-Bonnet esthesiometry. Of the 3 techniques, the ITP technique was the preferred method for retrobulbar administration of anesthetic agent in dogs because it was efficacious (pupil dilation and central rotation of the globe achieved in all eyes), easiest to perform, and provided thorough coverage of the intraconal retrobulbar space without complication. During the 2-week follow-up period, the ITP injection did not significantly affect STT, IOP, or Cochet-Bonnet esthesiometry values in dogs. In dogs, retrobulbar administration of anesthetic agents via the ITP technique is a potential alternative to systemic administration of neuromuscular blocking agents for ophthalmic surgery and provides the additional benefit of local ocular analgesia.

Anaesthesia and analgesia for dogs and cats in South Africa undergoing sterilisation and with osteoarthritis - an update from 2000 : report

A survey was conducted in 2000 into the use of analgesic drugs by veterinarians in South Africa. This survey was repeated in 2005 to establish whether the use of analgesic drugs has increased and which analgesic drugs are being used for acute pain and osteoarthritis. The number of sterilisations performed and the number of new cases of osteoarthritis in dogs and cats was estimated. It is estimated that approximately 260000 cats are operated on each year in South Africa and that 150000 cats are sterilised. Five hundred thousand dogs undergo surgery, of which 242000 are sterilised. It appears that the number of surgical procedures performed in South Africa has decreased. The estimated death rate following anaesthesia has remained unchanged at 1:1004. Overall, the use of analgesics by South African veterinarians has increased significantly. Fifty-six per cent of cats and 74% of dogs were given peri-operative analgesics but this increased to 94% and 84% after including pre-anaesthetic medications with analgesic properties. The use of opioids (morphine and buprenorphine) and propofol has increased significantly. Approximately 253000 dogs and 33000 cats with osteoarthritis are seen by veterinarians in South Africa annually. The recognition by veterinarians of osteoarthritis in cats appears to be poor and is in need of attention. Carprofen and glucosamine/chondroitin are the most commonly used agents for the treatment of osteoarthritis. Details of the drugs used by veterinarians are given. Knowledge of analgesic drugs has increased significantly over the last 5 years. Continuing education is thought to have played an important role in the changes reported in this study.

Comparison of morphine and carprofen administered alone or in combination for analgesia in dogs undergoing ovariohysterectomy

In this study the analgesic efficacy of the pure agonistic opioid morphine and the cyclo-oxygenase type-2-selective carprofen were compared since there is no previous specific comparative study for these two common analgesics. Forty-five bitches undergoing elective ovariohysterectomy were randomly assigned to one of three groups; receiving morphine 0.4 mg/kg bodyweight pre-operatively and 0.2 mg/kg every 4-6 hours thereafter (Morphine group), receiving a once-off carprofen 4 mg/kg injection (Carprofen group) or receiving both morphine and carprofen (MorphCarp group). The dogs were premedicated with acepromazine 0.01 mg/kg and induced with either thiopentone 5-10 mg/kg or propofol 4-6 mg/kg. General anaesthesia was maintained with halothane in oxygen. The degree of pain was assessed over a 24-hour period under blinded conditions using a pain scale modified from the University of Melbourne pain scale and the Glasgow composite pain tool. Physiological parameters such as respiratory rate, pulse rate and body temperature were also assessed over the same time period. There was no significant difference in pain-scores and thus analgesia offered by the three analgesia protocols at any assessment point across the three groups, but there were differences within groups across time points. Baseline total pain-scores were lower than scores at all post-operative points within all three groups. Both morphine and carprofen provided good analgesia without any obvious adverse effects. This study indicates that at the dosages indicated above, carprofen administered on its own produces analgesia equal to that produced by morphine and that the two drugs administered together do not produce better analgesia than either drug administered on its own.

Use of a continuous, local infusion of bupivacaine for postoperative analgesia in dogs undergoing total ear canal ablation

To determine whether addition of a continuous, local infusion of bupivacaine would improve postoperative analgesia in dogs undergoing total ear canal ablation. Randomized controlled trial. 16 dogs undergoing total ear canal ablation (12 unilaterally and 4 bilaterally with > 1 month between procedures). Dogs were randomly allocated to receive morphine (0.25 mg/kg [0.11 mg/lb]) at the end of the procedure (10 procedures) or morphine and a continuous, local infusion of bupivacaine (0.13 to 0.21 mg/kg/h [0.06 to 0.1 mg/lb/h]; 10 procedures). Dogs were observed for 48 hours after surgery. Additional doses of morphine were administered up to every 4 hours in dogs with signs of severe pain. Temperament, sedation, analgesia, and cumulative pain scores were not significantly different between groups any time after surgery. Recovery score was significantly higher for dogs that received bupivacaine than for control dogs 2 hours after extubation but not at any other time. Serum cortisol concentration was not significantly different between groups at any time but, in both groups, was significantly increased at the time of extubation, compared with all other observation times. Total number of additional doses of morphine administered was not significantly different between groups. Bupivacaine was not detected in the plasma of any of the dogs that received the local bupivacaine infusion. Results suggest that addition of a continuous, local infusion of bupivacaine did not significantly increase the degree of postoperative analgesia in dogs that underwent total ear canal ablation and were given morphine at the end of surgery.

Evaluation of analgesia provided by the administration of epidural ketamine in dogs with a chemically induced synovitis

Objective To determine if epidural ketamine provides analgesia in dogs with a chemically induced synovitis.Study design Prospective randomized experimental trial.Animals Thirty-two healthy, adult mongrel dogs (13–30 kg).Methods (Part I) Synovitis was induced in the right stifle of 16 dogs and allowed to develop for 12 hours. Epidural injection at the lumbosacral space of either ketamine (2 mg kg−1; n = 8) or placebo (n = 8) was performed. Limb use and pain were measured using a force platform and numerical rating scale (NRS). Assessments were performed before and at 12, 14, 16, 18, 20, and 24 hours after the induction of synovitis. (Part II) Epidural injection of either ketamine (n = 8) or placebo (n = 8) was performed immediately before the induction of synovitis. Analgesia was assessed as in Part I. Assessments occurred before and at 2, 4, 6, 8, and 12 hours after the induction of synovitis.Results (Part I) Vertical ground reaction forces (VGRF) significantly decreased and NRS scores of total pain significantly increased after the induction of synovitis in all dogs (p < 0.05). No significant differences in VGRF or NRS scores were measured between treatment groups at any assessment period. (Part II) Dogs that received ketamine had significantly lower NRS scores 2 hours after treatment (p < 0.05). NRS scores did not differ between groups at any other evaluation. VGRF did not differ significantly between treatment groups at any assessment period.Conclusion Epidural ketamine at a dose of 2 mg kg−1 administered after the development of synovitis does not provide significant levels of analgesia. Administration of ketamine before the induction of synovitis significantly decreased the NRS score 2 hours post-induction.Clinical relevance Administration of epidural ketamine before tissue injury may provide analgesia of short duration in dogs.

Attitudes and concerns of French veterinarians towards pain and analgesia in dogs and cats

ObjectiveTo compare the attitudes of French veterinarians to pain, and their provision of analgesia to animals, with that reported from other countries. Study designEpidemiological study. MethodsIn June 1999, 379 French veterinarians were surveyed to ascertain their views on pain evaluation and control in dogs and cats, and their use of analgesics in daily practice. Survey results are expressed as a percentage of responses. ResultsThe questionnaire was returned by 189 veterinarians (49.9%). The response rate was influenced by age (younger veterinarians were more likely to respond) but not gender. A majority (99.5%) expressed moderate to extreme concern over pain in their patients. Pain evaluation was based on the animal's attitude (88.3% dogs, 82.5% cats), interaction with the caregiver, response to palpation of the painful area (66.5% dogs, 62.7% cats) and inappetence (29.3% dogs, 46.3% cats, p < 0.001). Only 14.3% of respondents considered their knowledge of pain recognition to be inadequate. Many (58.8%) considered their methods of pain quantification and control (47% dogs, 59% cats) to be inadequate. Difficulties in recognizing pain (58.3%), a lack of knowledge in the appropriate use of analgesics (41.7%) and fear of drug side effects (30%) were used to explain inadequate provision of analgesia. Only 16.1 and 8.1% used opioids in dogs and cats, respectively. This low level of use resulted from the imposition of French narcotic legislation (79.9%) and lack of knowledge of opioid pharmacology (73.7%). Nonsteroidal anti‐inflammatory drugs (NSAIDs) and glucocorticoids were the most commonly used analgesics in both species (100% (dogs) and 96.7% (cats)). The most popular NSAID used in France was tolfenamic acid, followed by meloxicam (dogs), ketoprofen, nimesulide (cats) and carprofen (dogs). The type of surgery performed influenced the use of analgesics, from 17.2% for castration to 83.7% for orthopaedic procedures. Nonsurgical conditions believed to warrant analgesia included osteoarthritis (97.8%), trauma (97.3%) and bone neoplasia (93.4%). Female veterinarians were more likely than males to evaluate pain and provide analgesia. ConclusionFrench practitioners demonstrate a level of interest in analgesia, which appears to be at least equivalent to that reported from English‐speaking countries. The signs used to indicate the presence of pain do not, in general, appear to differ. Excessive confidence in their ability to recognize pain (despite a general ignorance of the subject), the minor role of animal health technicians in pain management and misconceptions about analgesics (mainly opioids) are French pecularities.

The evaluation of analgesia provided by epidural ketamine in dogs with chemically induced synovitis

Ketamine, a noncompetitive NMDA receptor antagonist, has been shown to provide analgesia in some species. To target the NMDA receptor specifically and to potentially minimize some untoward side-effects, ketamine had been used epidurally. The objective of this study was to determine the analgesic effect of epidurally administered ketamine in dogs with chemically induced synovitis. Sixteen healthy dogs were used. Dogs were anesthetized with propofol (4 mg kg−1 IV). Synovitis was induced by injecting 1 mL of sodium urate crystal solution (10 mg mL−1) into the right stifle. Dogs were allowed to recover and the synovitis was allowed to develop for 12 hours. The dogs were then anesthetized again using propofol (4 mg kg−1 IV). Lumbosacral epidural injections were performed with each dog receiving either 2 mg kg−1 of ketamine (20 mg mL−1) or an equal volume of placebo (sterile water containing not more than 0.1 mg mL−1 benzethonium chloride). Analgesia was assessed at baseline and then at 12, 14, 16, 18, 20, and 24 hours after induction of synovitis. Ground reaction forces (peak vertical force and impulse area) and overall pain were measured using a force platform and a pain scoring system (numerical rating scale). Analysis of the data by Repeated Measures anova showed that the dogs developed a significant lameness between the baseline and 12 hours. However, no significant difference in ground reaction forces or total pain score was demonstrated between the treatment and control groups at any other time. In conclusion, ketamine administered epidurally at a dose of 2 mg kg−1 did not provide significant analgesia in dogs with chemically induced synovitis.

Postoperative analgesia in dogs receiving epidural morphine plus medetomidine.

This investigation was carried out to compare the postoperative analgesia and plasma morphine concentrations in dogs given epidural morphine or epidural morphine combined with medetomidine prior to surgery. Twelve dogs (seven males and five females) with ruptured cranial cruciate ligaments presented to the Washington State University Veterinary Teaching Hospital. Six dogs received an epidural injection of morphine (0.1 mg/kg) and six dogs received epidural morphine (0.1 mg/kg) combined with medetomidine (0.005 mg/kg). Numeric rating scale (NRS) pain scores and cumulative pain scores (CPS) were assigned to 10-min segments of video. Video segments, heart rates and respiratory rates were recorded prior to premedication and at 4, 8, 12, 18 and 24 h after epidural injection. Blood was sampled from the cephalic vein at each of these times and during anesthesia at 0.5, 1, 2 and 3 h after epidural injection. Data were analyzed using either Friedman's test or one-way anova for repeated measures. In the morphine group, significant increases compared with premedication values were detected at 4, 8 and 12 h after epidural injection for NRS and at 4 and 12 h after epidural injection for CPS. In the morphine plus medetomidine group, NRS was significantly higher at 4 and 8 h whereas there were no differences from baseline values for CPS. Plasma morphine concentrations were not significantly different between treatment groups, but were significantly increased compared with preinjection values at 0.5, 1, 12, 18, and 24 h in the morphine plus medetomidine group. Epidurally administered morphine combined with medetomidine was associated with only minor benefits based on subjective pain scoring when compared with morphine alone in these dogs undergoing repair of a ruptured cranial cruciate ligament.

Epidural Catheter Analgesia in Dogs and Cats: Technique and Review of 182 Cases (1991–1999)

AbstractObjective:To characterize the indications and techniques for catheterization of the epidural space to treat pain in dogs and cats in a veterinary teaching hospital intensive care unit, and describe the analgesic regimens used in those patients. To provide a detailed description of the technique of epidural catheterization in companion animals.Design:Retrospective case series and clinical practice review.Setting:The Veterinary Teaching Hospital at the North Carolina State University College of Veterinary Medicine.Animals:Records from 160 dogs and 22 cats that had epidural catheters placed were identified.Interventions:Epidural catheterization for the purpose of providing analgesia for a variety of surgical and medical disorders was performed on both awake and anesthetized patients.Measurements and main results:The most frequently used analgesic agents were preservative‐free morphine and bupivacaine. 2The range of duration of catheter dwell time was 1.3–332 hours, with a mean duration of 50 hours and a median of 39 hours. Suspicion of catheter malpositioning prompted radiographic imaging of the catheter in 44 patients, and malpositioning was confirmed in 6 of those. Catheter tip positioning was recorded in 46 patients. The tip was located at L3‐L6 in 16, and T5‐L3 in 30. Twenty‐seven of those 30 patients were catheterized to treat pain associated with thoracotomy, forelimb amputation, pancreatitis, or peritonitis. Fifty‐one (28%) patients received no analgesics beyond those provided by the epidural catheter.Conclusions:Epidural administration of analgesia appeared to provide significant pain relief and was adequate as a sole analgesic treatment in some patients. Serious complications in these critically ill animals appeared to be uncommon. (J Vet Emerg Crit Care 2001; 11(2): 95–103)

Postoperative analgesia in dogs receiving epidural morphine and medetomidine

Analgesia was assessed in 12 dogs (seven males, five females; mean ± SEM age = 79.1 ± 8.9 months and weight = 38.2 ± 2.2 kg) undergoing repair of a ruptured cranial cruciate ligament. All dogs were given acepromazine (0.05 mg kg−1 IM) and atropine (0.04 mg kg−1 IM), induced with propofol and maintained with isoflurane in oxygen. Prior to surgery, dogs randomly received either preservative-free morphine (0.1 mg kg−1) or morphine (0.1 mg kg−1) with medetomidine (MEDET), 5 µg kg−1, via lumbosacral epidural injection.

Effects of diazepam and flumazenil on minimum alveolar concentrations for dogs anesthetized with isoflurane or a combination of isoflurane and fentanyl.

To determine the effect of a constant-rate infusion of fentanyl on minimum alveolar concentration (MAC) of isoflurane and to determine the interaction between fentanyl and a benzodiazepine agonist (diazepam) and antagonist (flumazenil) in isoflurane-anesthetized dogs. 8 mixed-breed adult dogs. Dogs were anesthetized with isoflurane 3 times during a 6-week period. After a 30-minute equilibration period, each MAC determination was performed in triplicate, using standard techniques. Fentanyl was administered as a bolus (10 microg/kg of body weight, IV) that was followed by a constant infusion (0.3 microg/kg per min, IV) throughout the remainder of the experiment. After determining isoflurane-fentanyl MAC in triplicate, each dog received saline (0.9% NaCl) solution, diazepam, or flumazenil. After 30 minutes, MAC was determined again. Fentanyl significantly decreased isoflurane MAC (corrected to a barometric pressure of 760 mm Hg) from 1.80+/-0.21 to 0.85+/-0.14%, a reduction of 53%. Isoflurane-fentanyl-diazepam MAC (0.48+/-0.29%) was significantly less than isoflurane-fentanyl-saline MAC (0.79+/-0.21%). Percentage reduction in isoflurane MAC was significantly greater for fentanyl-diazepam (74%), compared with fentanyl-saline (54%) or fentanyl-flumazenil (61%). Mean fentanyl concentrations for the entire experiment were increased over time and were higher in the diazepam group than the saline or flumazenil groups. Fentanyl markedly decreased isoflurane MAC in dogs. Diazepam, but not flumazenil, further decreased isoflurane-fentanyl MAC. Our results indicate that diazepam enhances, whereas flumazenil does not affect, opioid-induced CNS depression and, possibly, analgesia in dogs.

Comparison of epidural buprenorphine and morphine for post-operative analgesia in dogs

Buprenorphine is an effective analgesic when administered epidurally to humans. The purpose of this study was to compare epidural buprenorphine (B; n = 10) with epidural morphine (M; n = 10) for post-operative analgesia in dogs undergoing cranial cruciate ligament repair. All dogs were premedicated with acepromazine (0.1 mg kg−1 IM), induced with propofol (4–6 mg kg−1 IV) and maintained with halothane in oxygen. Dogs were randomly assigned to receive B (0.004 mg kg−1) or M (0.1 mg kg−1) in the lumbosacral epidural space in a total volume of 0.2 mL kg−1. End-tidal halothane and CO2 and temperature were recorded every 15 minutes until extubation (t = 0). A numerical rating pain score (SPS) was recorded at t = 0, 1, 2, 4, 6, 10 and 24 hours by a blinded observer. Dogs received rescue morphine (1.0 mg kg−1 IM) if indicated by SPS and the time of rescue analgesic administration was recorded. Observable side-effects such as urinary retention, sedation or pruritus were recorded. Data were analyzed with repeated measures anova. Mean ± SD body weight (kg) and age (yrs) for B dogs was 34.2 ± 10.8 and 5.5 ± 2.8; for M dogs these values were 36.6 ± 13.5 and 5.9 ± 3.3. Mean ± SD SPS for B dogs at t = 0, 1, 2, 4, 6, 10 and 24 hours were 1.2 ± 0.75, 3.2 ± 2.0, 4.5 ± 4.3, 4.6 ± 3.4, 4.7 ± 3.0, 5.0 ± 4.9 and 5.1 ± 3.5. For M dogs these values were 1.7 ± 0.5, 2.6 ± 2.0, 3.7 ± 0.75, 4.2 ± 2.2, 4.1 ± 3.0, 3.1 ± 2.1 and 3.9 ± 1.9. There were no significant differences between B and M with respect to SPS, times or frequency of rescue morphine administration, end-tidal halothane and CO2, or esophageal temperature. Fifty per cent of dogs in both groups required rescue morphine. Buprenorphine is as effective as morphine for epidural analgesia in healthy dogs undergoing hindlimb orthopedic surgery.

Newer Analgesics: Nonsteroid Anti-inflammatory Drugs, Opioids, and Combinations

Analgesia is an intrinsic part of anesthesia, and the use of opioids for premedication, supplementation of anesthesia, and postoperative analgesia is not new. Development of new potent and less toxic NSAIDs has now resulted in this type of analgesic, also playing a major role in perioperative analgesia. Weak cyclo-oxygenase inhibitors, and NSAIDs with high COX2 activity, are proving successful in the provision of analgesia in dogs and cats. Some newer opioids developed for man have potential for use in dogs and cats, and buprenorphine, a partial agonist, deserves further evaluation. Some novel analgesics have potential for use in animals, but the specific analgesic role of old friends ketamine and the alpha 2 adrenoceptor agonists is worthy of closer scrutiny.

Oxytocin content of the cerebrospinal fluid of dogs and its relationship to pain induced by spinal cord compression.

To determine whether oxytocin exists in the cerebrospinal fluid (CSF) of dogs and whether the amount of oxytocin in the CSF of dogs with neck or back pain caused by spinal cord compression is significantly different than that in the CSF of clinically normal dogs. Prospective controlled study. A total of 15 purpose-bred beagles and 17 client-owned dogs. CSF was collected by needle puncture of the cerebellar medullary cistern after induction of general anesthesia. Oxytocin levels within the samples were determined through radioimmunoassay. Dogs with spinal cord compression had significantly more oxytocin in their CSF than the clinically normal dogs (13.76 +/- 2.0 pg/mL and 3.61 +/- 0.63 pg/mL, respectively; P < .0001). Dogs with chronic signs (>7 days) had significantly more oxytocin in their CSF than dogs with acute signs (<7 days) (21.60 +/- 0.86 pg/mL and 6.80 +/- 0.81 pg/mL, respectively; P < .0001). Both acutely and chronically affected dogs had significantly more oxytocin in their CSF than the controls (P < .005 and P < .0001 respectively). Dogs with neck and back pain caused by spinal cord compression have significantly more oxytocin in their CSF than clinically normal dogs. Dogs with chronic clinical signs have significantly more oxytocin in their CSF than dogs with acute clinical signs. In humans, intrathecal injection of oxytocin is effective in treating low back pain for up to 5 hours. Intrathecal oxytocin may be a logical choice for perioperative analgesia in dogs undergoing myelography because the intrathecal space is accessed for injection of contrast agent.

モルヒネの硬膜外投与による犬の術後鎮痛効果

モルヒネの硬膜外投与による犬の術後鎮痛効果

Hemodynamic effects of epidural ketamine in isoflurane-anesthetized dogs.

The purpose of this study was to determine the hemodynamic effects of epidural ketamine administered during isoflurane anesthesia in dogs. Prospective, single-dose trial. Six healthy dogs (five males, one female) weighing 25.3 +/- 3.88 kg. Once anesthesia was induced, dogs were maintained at 1.5 times the predetermined, individual minimum alveolar concentration (MAC) of isoflurane. Dogs were instrumented and allowed to stabilize for 30 minutes before baseline measurements were recorded. Injection of 2 mg/kg of ketamine in 1 mL saline/4.5 kg body weight was then performed at the lumbosacral epidural space. Hemodynamic data were recorded at 5, 10, 15, 20, 30, 45, 60, and 75 minutes after epidural ketamine injection. Statistical analysis included an analysis of variance (ANOVA) for repeated measures over time. All data were compared with baseline values. A P < .05 was considered significant. Baseline values +/- standard error of the mean (X +/- SEM) for heart rate, mean arterial pressure, mean pulmonary artery pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index, stroke index, systemic vascular resistance, pulmonary vascular resistance, and rate-pressure product were 108 +/- 6 beats/min, 85 +/- 10 mm Hg, 10 +/- 2 mm Hg, 3 +/- 1 mm Hg, 5 +/- 2 mm Hg, 2.3 +/- 0.3 L/min/m2, 21.4 +/- 1.9 mL/beat/m2, 3386 +/- 350 dynes/sec/cm5, 240 +/- 37 dynes/sec/cm5, and 12376 +/- 1988 beats/min x mm Hg. No significant differences were detected from baseline values at any time after ketamine injection. The epidural injection of 2 mg/kg of ketamine is associated with minimal hemodynamic effects during isoflurane anesthesia. These results suggest that if epidural ketamine is used for analgesia in dogs, it will induce minimal changes in cardiovascular function.

Evaluation of Femoral Nerve Blockade for Postoperative Analgesia in Dogs Undergoing Stifle Arthrotomy

SummaryThe efficacy of the femoral nerve block (FNB) in alleviating postoperative pain was evaluated in dogs undergoing stifle arthrotomy. The pre- and postoperative nerve blocks were compared to intraarticular administration of a local anaesthetic. Forty-eight dogs with a ruptured cranial cruciate ligament were randomly assigned to the following groups: Group A (n = 16) received a femoral perineural injection prior to surgery; eight dogs within this group were given 0.5% bupivacaine and eight dogs received 0.9% saline. Group B (n = 16) had a femoral perineural injection immediately after surgery; eight dogs received 0.5% bupivacaine and eight received 0.9% saline. Group C (n = 16) dogs were given 0.5% bupivacaine (n = 8) or 0.9% saline (n = 8) intraarticularly. Postoperative pain was evaluated using a visual analog scale and a numerical rating scale, including measurement of heart rate, respiratory rate and systolic pressure. The dogs were scored preoperatively and at zero to six and at 24 hours after the operation. A significant difference was not noted between groups during the time until the first dose of supplemental analgesia nor in the total dose of supplemental analgesia required. The duration of the operation was found to be negatively correlated with the duration of postoperative analgesic effect. There was not any significant difference between the groups in pain scores at any time.Femoral nerve block (FNB) was evaluated for the control of postoperative pain in dogs undergoing stifle arthrotomy. FNB, using bupivacaine, was performed preoperatively and was compared to a postoperative FNB, and to saline controls. In addition, the efficacy of the FNB was compared to intra-articularly administered bupivacaine. Differences were not found between any groups in the alleviation of postoperative pain.

Epidural administration of bupivacaine, morphine, or their combination for postoperative analgesia in dogs

Objective To compare the analgesic effects of epidural administration of morphine (MOR), bupivacaine hydrochloride (BUP), their combination (COM), and 0.9% sterile NaCl solution (SAL) in dogs undergoing hind limb orthopedic surgeries. Design Blinded, randomized clinical trial. Animals 41 healthy dogs admitted for elective orthopedic surgeries involving the pelvis or hind limbs. Procedure Analgesic and control agents were administered postoperatively prior to recovery from isoflurane anesthesia. Ten dogs received MOR, 0.1 mg/ kg of body weight; 10 received BUP, 0.5%, 1 ml/10- cm distance from the occipital protuberance to the lumbosacral space; 11 received COM; and 10 received SAL epidurally. Dogs were monitored for 24 hours after epidural injection for pain score, heart and respiratory rates, blood pressure, time to required administration of supplemental analgesic agent, total number of supplemental doses of analgesic agent required, and plasma concentrations of cortisol, MOR, and BUP. Results Pain scores were significantly lower in dogs in the COM and BUP groups than in dogs in the SAL group. Pain scores also were significantly lower in dogs in the COM group than in dogs in the MOR group. Time to required administration of supplemental analgesic agent was longer for dogs in the COM group than for dogs in the MOR and SAL groups. Total number of supplemental doses of analgesic agent required was lower for dogs in the BUP and COM groups than for dogs in the SAL group. Clinical Implications Postoperative epidural administration of COM or BUP alone provides longerlasting analgesia, compared with MOR or SAL. (J Am Vet Med Assoc 1996;209:698-607)

Evaluation of pulmonary function and analgesia in dogs after intercostal thoracotomy and use of morphine administered intramuscularly or intrapleurally and bupivacaine administered intrapleurally

SUMMARY Eighteen dogs undergoing lateral thoracotomy at the left fifth intercostal space were randomly assigned to 1 of 3 postoperative analgesic treatment groups of 6 dogs each as follows: group A, morphine, 1.0 mg/kg of body weight, im; group B, 0.5% bupivacaine, 1.5 mg/kg given interpleurally; and group C, morphine, 1.0 mg/kg given interpleurally. Heart rate, respiratory rate, arterial blood pressure, arterial blood gas tensions, alveolar-arterial oxygen differences, rectal temperature, pain score, and pulmonary mechanics were recorded hourly for the first 8 hours after surgery, and at postoperative hours 12, 24, and 48. These values were compared with preoperative (control) values for each dog. Serum morphine and cortisol concentrations were measured at 10, 20, and 30 minutes, hours 1 to 8, and 12 hours after treatment administration. All dogs had significant decreases in pHa, PaO2, and oxygen saturation of hemoglobin, and significant increases in PaCO2 and alveolar-arterial oxygen differences in the postoperative period, but these changes were less severe in group-B dogs. Decreases of 50% in lung compliance, and increases of 100 to 200% in work of breathing and of 185 to 383% in pulmonary resistance were observed in all dogs after surgery. Increases in work of breathing were lower, and returned to preoperative values earlier in group-B dogs. The inspiratory time-to-total respiratory time ratio was significantly higher in group-B dogs during post-operative hours 5 to 8, suggesting improved analgesia. Blood pressure was significantly lower in group-A dogs for the first postoperative hour. Significant decreases in rectal temperature were observed in all dogs after surgery, and hypothermia was prolonged in dogs of groups A and C. Significant differences in pain score were not observed between treatment groups. Cortisol concentration was high in all dogs after anesthesia and surgery, and was significantly increased in group-B dogs at hours 4 and 8. Significant differences in serum morphine concentration between groups A and C were only observed 10 minutes after treatment administration. In general, significant differences in physiologic variables between groups A and C were not observed. Results of the study indicate that anesthesia and thoracotomy are associated with significant alterations in pulmonary function and lung mechanics. Interpleurally administered bupivacaine appears to be associated with fewer blood gas alterations and earlier return to normal of certain pulmonary function values. Interpleural administration of morphine does not appear to provide any advantages, in terms of analgesia or pulmonary function, compared with its im administration.

Advantages and Guidelines for Using Alpha-2 Agonists as Anesthetic Adjuvants

Xylazine and medetomidine produce reliable sedation, muscle relaxation, and analgesia in dogs and cats. In addition, alpha-2 agonists have proved very effective as sedative-analgesic adjuncts when coadministered with benzodiazepine or opioid agonists. Alpha-2 agonists should not be classified as monoanesthetics. They are excellent anesthetic adjuncts when combined with dissociatives and opioids. Because of the acute alterations in cardiopulmonary function commonly induced by alpha-2 agonists, it is suggested that their use be restricted to the young healthy patient undergoing routine surgical or diagnostic procedure. The development of more specific and selective alpha-2 agonists will continue to enhance the safety and reliability of this novel class of compounds. The unique spectrum of anesthetic properties induced by alpha-2 agonists has assured them of an increasingly prominent role in the development of new and sophisticated ways of achieving anesthesia.