Analgesia in dogs after intercostal thoracotomy. A comparison of morphine, selective intercostal nerve block, and interpleural regional analgesia with bupivacaine

Repeated bolus injections of bupivacaine for continuous bilateral transversus thoracis plane block undergoing median sternotomy in a dog: A case report

An 8-year-old, 6.5 kg, neutered female Shih-Tzu dog was presented for surgical resection of a mediastinal mass. A median sternotomy and left cranial lung lobectomy were performed. Intraoperatively, with the patient under general anaesthesia, a bilateral transversus thoracis plane (TTP) block was performed by injecting 0.5% bupivacaine (0.2 ml/kg) per side using real-time ultrasound guidance. After surgery, indwelling catheters for repeated bolus injections of bupivacaine in TTP were placed as follows: the fifth sternebra was palpated in dorsal recumbency, and the transducer was placed in the longitudinal plane lateral to the sternal border. A 16 gauge over-the-needle catheter was inserted caudo-cranially using an in-plane technique and located in the TTP. An intermittent bolus of bupivacaine (0.1 ml/kg) per side was injected via the indwelling catheter every 8 h for 3 days, with a constant rate infusion of an intravenous fentanyl (1 μg/kg/h) and ketamine (0.12 mg/kg/h) combination. Post-operative pain was evaluated using the Glasgow composite measure pain scale and the score was 4-5/24 on the day of surgery and gradually decreased over time. Additional rescue analgesia was not required. Repeated boluses of bupivacaine for a continuous bilateral TTP block may be a useful adjuvant for perioperative pain management strategies, including median sternotomy, in dogs.

Development of Enhanced Recovery After Surgery (ERAS) protocols in veterinary medicine through a one-health approach: the role of anesthesia and locoregional techniques

Enhanced Recovery After Surgery (ERAS) is a new and emerging concept in human medicine that involves rethinking the preoperative, intraoperative, and postoperative periods. The ultimate, overarching aim is to improve patient outcome following surgery and, thus, return to a normal daily routine as soon as possible. The development and implementation of locoregional anesthetic techniques in humans is one of the key elements driving these protocols. In veterinary medicine, we are no exception: the rapidly growing interest, development, and refinement of these techniques in our veterinary species is changing the way we think of anesthesia and analgesia. The potential real benefits are yet to be determined, as this concept is implemented into our veterinary hospitals in general, and our surgical patients in particular, in a more systematic and routine way. In this article, we will introduce the reader to the concept of ERAS protocols and the role of regional anesthesia in some common surgical procedures.

Description of an Ultrasound-Guided Transverse Approach to the Transversus Thoracis Plane Block and Evaluation of Injectate Spread in Canine Cadavers

Simple Summary

In humans, the aim of the transversus thoracis plane block is to desensitise the intercostal nerves running through this plane, providing analgesia to the anterior chest wall. Our objective was twofold: describing an ultrasound-guided transverse approach to the transversus thoracis plane and evaluating the spread of two injectable volumes in canine cadavers. Gross anatomy of the ventral thoracic area and sonoanatomy between the fifth and sixth costal cartilages were described in two dog cadavers. Eight cadavers were used to describe this approach and were subsequently dissected to evaluate the injectate spread and the intercostal nerves staining after low volume (0.5 mL kg⁻¹) and high volume (1 mL kg⁻¹) dye-lidocaine injection. After all injections, the injectable solution was distributed along the transversus thoracis plane, staining a median number (range) of 3 (2–4) and 4 (3–5) nerves with low and high volume, respectively (p = 0.014). The transverse approach to the transversus thoracis plane is a feasible, single injection point technique that provides the staining of several intercostal nerves. The injection of high versus low volume increases the number of stained nerves.

Abstract

Transversus thoracis plane (TTP) block has demonstrated to produce analgesia in humans undergoing median sternotomy. The objectives of the study were to describe an ultrasound-guided transverse approach to the transversus thoracis plane (t-TTP) and to evaluate the spread of two injectable volumes in canine cadavers. Two cadavers were used to describe relevant gross anatomy of the ventral thoracic area and sonoanatomy between the fifth and sixth costal cartilages. Then, eight cadavers were used to describe the ultrasound-guided injection into the TTP and were dissected to evaluate the injectate spread and the intercostal nerves staining with two different dye-lidocaine volumes: low volume (LV) 0.5 mL kg⁻¹ and high volume (HV) 1 mL kg⁻¹. To compare the spread between both volumes the Fisher’s exact test and Wilcoxon signed-rank test were used. The solution spread along the TTP after all injections, staining a median number (range) of 3 (2–4) and 4 (3–5) nerves with LV and HV, respectively (p = 0.014). The injection of HV versus LV increases the number of stained nerves. Ultrasound-guided t-TTP is a feasible technique that provides staining of several intercostal nerves with a single injection site, so it could be useful to provide analgesia to the ventral chest wall.

Ultrasound-guided parasternal injection in dogs: a cadaver study

OBJECTIVES

To describe the technique of performing an ultrasound-guided distal parasternal intercostal block and to determine the distribution of two volumes of methylene blue dye solution injected in canine cadavers.

STUDY DESIGN

Prospective cadaver study.

ANIMALS

A group of seven canine cadavers weighing 12-34 kg.

METHODS

The space between the transversus thoracic and the internal intercostal muscles is a virtual cavity. Ultrasound-guided injections in the distal (parasternal) intercostal space were performed using dye solution at 0.05 mL kg^-1 in each intercostal space from the second to seventh (LV, low volume, six injections per dog) in one hemithorax, and 0.1 mL kg^-1 in the third, fifth and seventh intercostal spaces (HV, high volume, three injections in each dog) on the contralateral side. Anatomical dissection was carried out to describe dye spread characteristics and staining of intercostal nerves.

RESULTS

The ultrasonographic landmarks for injection were identified in each cadaver. In the LV group the solution was found in every intercostal space (36/36), whereas the HV injection stained six intercostal spaces in two dogs, five in two, and in two dogs the solution was found in four and three spaces, respectively, demonstrating multisegmental distribution. Intrapleural staining was observed after two injections.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasound-guided injection of 0.05 mL kg^-1 at the distal intercostal space resulted in staining of the intercostal nerve in all dogs when performed in every space and may be an appropriate alternative to previously reported techniques. A single injection of 0.1 mL kg^-1 may anaesthetize more than one intercostal nerve, but not consistently. Clinical investigations are warranted to better characterize and to refine this locoregional technique.

Early Analgesic Efficacy of Morphine, Butorphanol, Lidocaine, Bupivacaine or Carprofen After Periodontal Treatment in Dogs

The early effectiveness of 5 analgesics was investigated after periodontal treatment. Dogs were assigned to 6 groups (n = 14 each). A prospective, randomized and blinded clinical study was performed. Before anesthesia was induced, butorphanol, morphine, carprofen and saline were administered. After induction, a maxillary and mandibular block was performed with lidocaine or bupivacaine. Painful periodontal therapies were performed. Two hours after the administration of analgesics and after anesthesia reversal, pain was scored using the Visual Analog Scale for pain (VAS) and the modified University of Melbourne Pain Score (UMPS). Blood glucose and cortisol levels were measured prior to analgesic administration and again 2 hours later. Rescue analgesia was provided when the VAS exceeded 50 mm or the UMPS exceeded 14 points. Rescue analgesia was required in one patient in the morphine group and one in the carprofen group. The VAS values were significantly lower in the butorphanol group compared to those of the saline group and in the bupivacaine group vs. those in the saline and lidocaine groups. Significantly lower UMPS values were obtained in the bupivacaine group compared to those in the saline, butorphanol and lidocaine groups and in the carprofen group vs. those in the saline and lidocaine groups. Significantly higher serum cortisol values were found in the lidocaine group compared to those in the saline, bupivacaine and carprofen groups. Administration of carprofen or the use of nerve blocks with bupivacaine improved analgesia after periodontal treatment more than did butorphanol, morphine or nerve blocks using lidocaine.

Evaluation of the effect of ultrasound guidance on the accuracy of intercostal nerve injection: a canine cadaveric study

OBJECTIVE

To develop an ultrasound-guided approach to intercostal nerve injection and to compare the success rate of intercostal nerve injections using blind or ultrasound-guided technique in canine cadavers.

STUDY DESIGN

Prospective, randomized, descriptive, experimental anatomic study.

ANIMALS

A total of 14 mid-sized adult canine cadavers.

METHODS

Ultrasound landmarks were identified by dissection of four cadavers and used to develop an ultrasound-guided technique. The remaining 10 cadavers were randomly assigned to blind (five cadavers) or ultrasound-guided (five cadavers) injections of the third to the ninth intercostal nerves bilaterally with 0.03 mL kg^-1 of colorant per injection. The target for intercostal injections was the caudal border of the respective rib, between the internal intercostal membrane and the parietal pleura. Additionally, displacement of the parietal pleura without visible intramuscular distribution was considered the end point for ultrasound-guided injections. For each cadaver, a practitioner in training performed the blocks on one hemithorax, while an experienced practitioner performed the blocks on the opposite hemithorax. Injections were considered successful if ≥1 cm of the target nerve was stained with colorant upon dissection. Success rates and length of nerve staining were analyzed with Fisher's exact and t tests, respectively. Data were considered statistically different with p < 0.05.

RESULTS

Success rates of blind and ultrasound-guided technique were 57.1% and 91.4%, respectively (p < 0.0001). The length of intercostal nerve staining was 3.1 ± 1.2 cm and 3.6 ± 1.0 cm using blind and ultrasound-guided techniques, respectively (p = 0.02). No differences were observed between the two practitioners for blind (p = 0.33) and ultrasound-guided techniques (p = 0.67).

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasound guidance improves the accuracy of intercostal nerve injections when compared with blind technique, independently of the level of expertise in regional anesthesia.

Ultrasound-guided serratus plane block as an effective adjunct to systemic analgesia in four dogs undergoing thoracotomy

Background

Ultrasound-guided serratus plane block (UGSPB) is a loco-regional anesthesia technique designed to desensitize the thoracic wall. It is a compartmental block, where local anesthetic is delivered to the fascial, inter-muscular plane. Since its original description in humans, two cadaveric veterinary studies, redefining the technique, have been performed. Taking into account the successful use of the UGSPB in human medicine, we employed the veterinary description to perform this block in four dogs undergoing thoracotomy. The case series described below aims to share our experience of the clinical application of this new loco-regional anesthesia technique in dogs.

Case Description

Four dogs, with different underlying medical conditions underwent cranial lateral thoracotomy. The analgesia protocol consisted of intravenous methadone and UGSPB performed half an hour before the beginning of the procedure. The cardiovascular system was closely monitored for any signs of nociception. Fentanyl, although available as rescue analgesia, was not required in any of these cases as no signs of nociception were present.

Conclusion

To the authors' knowledge, this is the first veterinary clinical report using the UGSPB as a part of a multimodal analgesia protocol in dogs undergoing thoracotomy. Based on this observation, UGSPB has the potential to prevent nociception and reduce the intraoperative opioid requirements in dogs undergoing thoracotomy. A prospective randomized clinical trial is required to confirm these promising results.

Life-Threatening Hemorrhage During Patent Ductus Arteriosus Ligation in a Cat: Xenotransfusion With Canine Blood

A 13-month-old Sphynx cat was referred for patent ductus arteriosus (PDA) ligation. A left thoracotomy was performed and the PDA was efficiently ligated. Immediately after chest tube placement, it presented extensive intrathoracic bleeding from the caudal intercostal artery. In view of the absolute necessity of a blood transfusion and given that compatible feline blood was not available, xenotransfusion of canine blood was administered to the cat and resulted in a positive outcome.

Locoregional Anesthesia of the Thoracic Limbs and Thorax in Small Animals

The incorporation of nerve stimulation and ultrasound guidance to veterinary regional anesthesia allows accurate performance of techniques to block the thoracic limb and the thorax. When performed correctly, regional anesthesia can either constitute an alternative to the use of opioids and other systemic analgesics, or have a significant opioid-sparing effect. This article provides an overview of some techniques described using objective methods of nerve location, which can be used to provide perioperative locoregional anesthesia and analgesia to the thoracic limb and thorax. The approaches described may be used to decrease the perioperative use of opioids in small animals.

Modified rib pivot lateral thoracotomy: a case series

OBJECTIVE

To describe a modified rib pivot thoracotomy and its clinical application in client-owned dogs and cats.

STUDY DESIGN

Case series of 24 dogs and 1 cat requiring a thoracotomy.

METHODS

A lateral thoracic incision over the required thoracic segment was made. The latissimus dorsi muscle was reflected dorsally. The predetermined rib was identified and the periosteum overlying the rib was elevated circumferentially, avoiding the intercostal neurovascular structures. Holes were pre-placed above and below the proposed osteotomy site. The rib was osteotomised and pivoted cranially. The pleura was incised and the required intrathoracic procedure was then performed. The thoracic cavity was closed by pre-placement of a suture through the pre-placed holes within the osteotomised rib. The pleura and intercostal musculature were closed, avoiding the intercostal neurovascular structures. The rib was re-apposed and the lateral approach was closed. The cases included were reviewed for both the rib pivoted as per the procedure required and postoperative complications.

RESULTS

The study group comprised 8 Staffordshire Bull Terriers, 2 Poodles, 2 German Shepherd Dogs, 1 each of Basset Hound, Rhodesian Ridgeback, Golden Retriever, Australian Shepherd, Vizsla, Bull Mastiff, Schnauzer, Jack Russell Terrier, Bulldog, Deerhound, Labrador Retriever and Australian Terrier, and 1 cat. A modified rib pivot thoracotomy was performed for lung lobectomy (n = 11), oesophagectomy (7), subtotal pericardectomy (5), patent ductus arteriosus ligation (1) and thoracic duct ligation (1). Follow-up ranged from 2 to 40 weeks postoperatively. Postoperative complications included seroma formation in two dogs.

CONCLUSION

A modified rib pivot thoracotomy should be considered as an alternative lateral thoracic approach with good exposure, minimal complications and low morbidity.

Evaluation of thoracic epidural analgesia induced by lidocaine, ketamine, or both administered via a lumbosacral approach in dogs

OBJECTIVE

To determine the analgesic and systemic effects of thoracic epidural administration of ketamine, lidocaine, or both in conscious dogs.

ANIMALS

6 adult mixed-breed dogs.

PROCEDURES

Each dog received 2% lidocaine hydrochloride without epinephrine (3.8 mg/kg), 5% ketamine hydrochloride (3.0 mg/kg), or both in randomized order with ≥ 1 week between treatments. Drugs were administered in a total volume of 0.25 mL/kg through a thoracic epidural catheter implanted via the lumbosacral approach. Heart rate, blood pressure, respiratory rate, rectal temperature, analgesia, sedation, and ataxia were determined before treatment (baseline [time 0]) and at 5, 10, 15, 20, 30, 40, 50, 60, 90, 120, 150, and 180 minutes after administration.

RESULTS

The main areas of analgesia for the 3 treatments were the thorax and forelimbs bilaterally. Median duration of analgesia was shorter after administration of ketamine (30 minutes) than after administration of lidocaine (40 minutes) and lidocaine plus ketamine (90 minutes). All treatments caused moderate motor blockade, and only the ketamine and lidocaine plus ketamine treatments caused mild sedation. Significant decreases in systolic and mean arterial blood pressure were observed only with the lidocaine plus ketamine treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Thoracic epidural administration of lidocaine plus ketamine resulted in longer duration of analgesia of the thorax and forelimbs bilaterally in conscious dogs, compared with administration of ketamine or lidocaine alone. Additional studies are needed to determine whether this technique adequately relieves postoperative pain after thoracic surgical procedures and whether it causes respiratory depression in dogs.

Hemodynamic Effects of Interpleural Lidocaine and Bupivacaine Combination in Anesthetized Dogs with and Without an Open Pericardium

OBJECTIVE

To identify dysrhythmias and hemodynamic changes after lidocaine and bupivacaine infusion into the interpleural space with an open pericardium.

STUDY DESIGN

Experimental study.

ANIMALS

Six adult dogs.

METHODS

Systemic arterial pressure and electrocardiogram were recorded. A 7.5 Fr Swan-Ganz catheter was advanced to the level of the main pulmonary artery to record pulmonary arterial pressure. Cardiac output was measured by a thermodilution technique. A pericardial window (PW) was performed in 3 dogs using thoracoscopy. Hemodynamic variables were recorded before and 15 minutes after injection of lidocaine (1.5 mg/kg) and bupivacaine (1.5 mg/kg) into the pleural space in the control group and in the pericardial space for the PW group. A randomized-block ANOVA for repeated measures was used to evaluate the effect of local anesthetic administration on hemodynamic and electrophysiologic variables in dogs with a pericardectomy.

RESULTS

Each dog maintained sinus rhythm. Infusion of local anesthetic induced a significant increase in right ventricular diastolic pressure (P = .002) and a significant decrease in stroke volume (P = .047) in both groups; however, the effects were not significantly different between groups.

CONCLUSIONS

Infusion of lidocaine and bupivacaine, either intrapleural or in the pericardial space, had a mild detrimental effect on cardiac output.

CLINICAL RELEVANCE

Intrapleural administration of lidocaine and bupivacaine at a therapeutic dose can be used safely in healthy dogs with a pericardectomy.

Comparison of perioperative analgesic protocols for dogs undergoing tibial plateau leveling osteotomy

OBJECTIVE

To compare effects of 3 commonly used perioperative analgesic protocols (epidural injection, intra-articular injection, and intravenous [IV] injection) for management of postoperative pain in dogs after tibial plateau leveling osteotomy (TPLO).

STUDY DESIGN

Prospective, randomized clinical trial.

ANIMALS

Fifty-six healthy dogs with naturally occurring cranial cruciate ligament rupture.

METHODS

Dogs were premedicated with IV hydromorphone and acepromazine and were randomly assigned to receive either E (preoperative epidural injection with morphine and bupivacaine), IA (pre- and postoperative intra-articular injections of bupivacaine), or C (neither epidural morphine and bupivacaine, nor intra-articular bupivacaine). All dogs were administered hydromorphone (0.05 mg/kg IV) at extubation and as needed to maintain comfort postoperatively. Patients were observed and monitored continuously for 24 hours and discomfort was assessed using visual analog pain scores (VASs), multifactorial pain scores (MPSs), and response to a pressure nociceptive threshold (PNT) measuring device. Time to 1st dose and the total doses of hydromorphone required to achieve adequate comfort for each dog were recorded.

RESULTS

No differences in measured indices of postoperative pain were observed between dogs of each treatment group; VAS (P=.190), MPS (P=.371), and PNT (P=.160). Time to 1st analgesic intervention was longer for Group E compared with Group C (P=.005) and longer for Group IA compared with Group C (P=.032). Although time to 1st intervention between Groups E and IA were longer for Group E, differences were not significant. To provide an adequate level of comfort, more analgesic interventions were administered to dogs in Group C compared with dogs in group E (P=.015). On average, more hydromorphone was administered to Group C compared with Group IA (P=.072) and to Group IA compared with Group E (P=.168), but statistical significance was not reached for these data.

CONCLUSIONS

In this study population, significant differences were seen in time to 1st hydromorphone dose between Groups E and IA compared with Group C. As well, more supplemental analgesia was administered to Group C compared with Group E to maintain the same level of postoperative comfort. Although differences between Groups E and IA tended to favor the epidural group, differences were minimal and not statistically significant.

CLINICAL RELEVANCE

Our results suggest that regardless of analgesic protocol, measured indices of pain in dogs after TPLO can be minimized if dogs are continuously observed and appropriately supplemented with parenteral opioids. However, the frequency of postoperative opioid dosing can be minimized and may be a factor when contemplating supplementary use of epidural or intra-articular injections as part of a balanced analgesic approach.

Controlled, clinical trial assessing saphenous, tibial and common peroneal nerve blocks for the control of perioperative pain following femoro-tibial joint surgery in the nonchondrodystrophoid dog

OBJECTIVE

To determine whether bupivacaine peripheral nerve block of the saphenous, tibial and common peroneal nerves proximal to the femoro-tibial joint reduces peri-operative pain following extracapsular surgical stabilization of cranial cruciate ligament rupture in the nonchondrodystrophoid dog.

ANIMALS

Forty-one dogs with naturally acquired femoro-tibial joint instability. Study design Randomized, controlled, clinical trial.

METHODS

Dogs diagnosed with suspected cranial cruciate ligament injury based on physical and radiographic evidence were randomly assigned to treatment (bupivacaine) or control (saline) nerve blocks before femoro-tibial joint surgery. Pain scores, skin sensation, pain threshold to incisional pressure, time to first systemic 'rescue' opioid analgesic and total analgesic dose were evaluated for 24 hours. p < 0.05 was considered significant.

RESULTS

Treatment dogs had a significantly longer period of cutaneous desensitization than control dogs. There were no significant differences between treatment and control groups for pain score, pain threshold to incisional pressure, or time to first-rescue analgesic. The treatment group received significantly more supplemental analgesics than the control group.

CONCLUSIONS

These peripheral nerve blocks were easy to perform and resulted in significant desensitization of the associated nerve autonomous zones, but did not improve post-operative analgesia.

CLINICAL RELEVANCE

Clinical benefit was not detected when using this technique for peri-operative pain management following extracapsular cranial cruciate ligament surgical stabilization.

Assessment of a von Frey device for evaluation of the antinociceptive effects of morphine and its application in pharmacodynamic modeling of morphine in dogs

OBJECTIVE

To assess the use of a von Frey device as a mechanical nociceptive stimulus for evaluation of the antinociceptive effects of morphine in dogs and its potential application in the pharmacodynamic modeling of morphine in that species.

ANIMALS

6 healthy Beagles.

PROCEDURE

von Frey thresholds were measured in all dogs before and at intervals after they received no treatment (control dogs) and i.v. administration of morphine sulfate (1 mg/kg; treated dogs) in a crossover study. The von Frey device consisted of a rigid tip (0.5 mm in diameter) and an electronic load cell; the operator was unaware of recorded measurements.

RESULTS

Application of the von Frey device was simple and well tolerated by all dogs and caused no apparent tissue damage. No significant changes in thresholds were detected in the control dogs at 8 hourly measurements, indicating a lack of acquired tolerance, learned aversion, or local hyperalgesia. When assessed as a group, treated dogs had significantly high thresholds for 4 hours following morphine administration, compared with baseline values; individually, thresholds decreased to baseline values within (mean +/- SE) 2.8 +/- 0.6 hours. The maximal effect (change from baseline values) was 213 +/- 43%, and the plasma morphine concentration to achieve 50% maximal effect was 13.92 +/- 2.39 ng/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Data suggest that, in dogs, evaluation of the antinociceptive effect and pharmacodynamic modeling of a dose of morphine sulfate (1 mg/kg, i.v.) can be successfully achieved by use of a von Frey device.

Intercostal thoracotomy closure: transcostal sutures as a less painful alternative to circumcostal suture placement

OBJECTIVE

To determine if transcostal thoracotomy closure resulted in less pain than circumcostal closure.

STUDY DESIGN

Experimental cadaver and prospective clinical study.

ANIMALS

Two canine cadavers and 13 adult, 22-29 kg dogs.

METHODS

Phase 1: In 2 cadavers, 4 suture passage techniques were evaluated to determine the incidence of nerve entrapment in circumcostal intercostal thoracotomy closure. Phase 2: Pain after circumcostal closure (7 dogs) or transcostal closure (6 dogs) of a 4th intercostal space thoracotomy was evaluated by use of pain threshold scores, fentanyl administration rates, heart and respiratory rates, and numerical ratings for behavior. Arterial blood gas analyses were obtained 4 hours postoperatively. Transcostal closure was accomplished by drilling 5-6 small holes in the 5th rib and passing sutures through the holes and around the 4th rib to achieve closure. Pain threshold scores (PTS) were measured by an observer unaware of closure assignment, at 2, 4, 12, and 24 hours after closure by applying slowly increasing pressure to the incision line using a load cell. Rates of fentanyl administration were adjusted based on subjective impressions of dog comfort by a second observer unaware of closure assignment.

RESULTS

A 70-100% incidence of nerve entrapment was found for all circumcostal techniques. PTS was higher (P=.045) and fentanyl infusion rates were lower (P=.001) for the transcostal group at 2, 4, 12, and 24 hour postoperatively compared with the circumcostal group.

CONCLUSION

There is a high incidence of nerve entrapment using circumcostal closure techniques. A transcostal technique appears to be associated with less pain during the first 24 hours postoperatively.

CLINICAL RELEVANCE

Based on lower pain scores, transcostal thoracotomy closure may be preferable to circumcostal closure techniques.

Evaluation of a short duration behaviour-based post-operative pain scoring system in rats

We have recently demonstrated dose-related analgesic-induced reductions in the occurrence of 7 behavioural activities following midline laparotomy in rats. For these behaviours to be useful in evaluating pain in laboratory rats they must be shown to occur after different types of surgery, and frequently enough to allow rapid scoring of animals. Here, the relevant behaviours were used to test the analgesic efficacy of meloxicam with a variation of our previous laparotomy model. As part of an unrelated project, 57 male Fischer rats were divided into groups to receive either saline (0.2 ml/100g s.c.), meloxicam (0.5, 1 or 2 mg/kg s.c.) or carprofen (2.5, 5, or 10 mg/kg s.c.) 1h before surgery. Behaviour data were collected for 10 min following 25 min of recovery from isoflurane anaesthesia. The cumulative frequencies of back arching, fall/stagger, writhe and poor gait were used to compute a composite behaviour score. Irrespective of whether analyses included only 5 or all 10 min of the observation period, the relevant behaviours occurred significantly more often in rats given saline or low dose meloxicam than in those given 1 or 2 mg/kg of meloxicam, or any dose of carprofen. We conclude that this technique of quantifying post-surgery behaviour is an effective pain scoring method following abdominal surgery in rats, and that 1 mg/kg meloxicam significantly attenuates laparotomy induced pain. Since only a short observation period is required, this approach represents an important practical advance in assessing abdominal pain severity and clinical drug potency.

Assessment of pain in dogs: veterinary clinical studies

Hundreds of thousands of animals are presented to US veterinarians annually for surgery or for evaluation of painful disease. This large population offers the opportunity for clinical research of both acute and chronic pain syndromes. Although there is growing interest by veterinary clinical specialists to explore the nature of animal pain and how best to treat it, this resource is relatively unknown to the pain research community. Computer-assisted collection of behavioral data has created new opportunities for characterizing the pain experience in animal species for the benefit of both animals and humans. This review describes the current state of veterinary clinical pain studies in dogs and an application of computer-assisted behavioral analysis.

Effects of preoperative administration of ketoprofen on anesthetic requirements and signs of postoperative pain in dogs undergoing elective ovariohysterectomy

OBJECTIVE

To determine the effects of preoperative administration of ketoprofen on anesthetic requirements and signs of postoperative pain in dogs undergoing elective ovariohysterectomy.

DESIGN

Randomized, controlled clinical trial.

ANIMALS

22 clinically normal client-owned dogs.

PROCEDURE

60 minutes before induction of anesthesia, 11 dogs were given ketoprofen (2 mg/kg [0.9 mg/lb], i.m.), and the other 11 were given saline (0.9% NaCl) solution. Dogs were premedicated with glycopyrrolate, acepromazine, and butorphanol and anesthetized with thiopental; anesthesia was maintained with isoflurane. Ovariohysterectomy was performed by an experienced surgeon, and butorphanol was given 15 minutes before completion of the procedure. Objective behavioral scores and numerical pain scores at rest and with movement were recorded every 2 hours for 12 hours after surgery and then every 4 hours for an additional 12 hours.

RESULTS

Preoperative administration of ketoprofen did not reduce the dose of thiopental required to induce anesthesia or the end-tidal concentration of isoflurane required to maintain anesthesia. Activity levels and median objective behavioral scores were significantly higher 4 and 6 hours after surgery in dogs given ketoprofen than in dogs given saline solution. However, mean numerical pain scores in dogs given ketoprofen were not significantly different from scores for dogs given saline solution at any time.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that preoperative administration of ketoprofen does not reduce anesthetic requirements in dogs undergoing elective ovariohysterectomy but may reduce signs of pain after surgery. Results also suggest that the objective behavioral score may be a more sensitive measure of acute postoperative pain than traditional numerical pain scores.

Analgesia in critical care

All medical interventions, including the provision of analgesia, are associated with risks and benefits, which, when considered together, comprise that intervention's risk/benefit ratio. All interventions have alternatives (including no intervention), and each alternative possesses its own risk/benefit ratio. Clinical decision making involves comparing and contrasting the risk/benefit ratios of alternative interventions (relative risk/benefit ratio). The most formidable limitations of drug treatment relate to their potential to produce pharmacologic side effects or complications. Careful monitoring and the use of strategies for preventing and managing drug side effects are often all that is required to maintain efficacy.

Evaluation of the clinical efficacy of meloxicam in cats with painful locomotor disorders

The ability of two non-steroidal anti-inflammatory drugs to modify the clinical manifestations of pain associated with locomotor disease was assessed. Sixty-nine cats with acute or chronic locomotor disorders were recruited from 14 first opinion UK veterinary practices and randomly allocated to one of two treatment groups. Group A received meloxicam drops (0.3 mg/kg orally on day 1 followed by 0.1 mg/kg daily for four more consecutive days) and group B received ketoprofen tablets (1.0 mg/kg orally once daily for five days). Each cat underwent a full clinical examination before treatment, 24 hours after initiation of treatment and 24 hours after completion of treatment. General clinical parameters (demeanour and feed intake) and specific locomotor parameters (weightbearing, lameness, local inflammation and pain on palpation) were scored using a discontinuous scale scoring system. The two groups did not differ in terms of age, weight, gender distribution or duration of clinical signs; nor did they differ in terms of general clinical or specific locomotor scores pretreatment. Both treatment regimens resulted in a significant improvement in demeanour, feed intake and weightbearing, and a significant reduction in lameness, pain on palpation and inflammation. No significant difference was observed between the two treatment groups with respect to any of the parameters measured and both treatments were associated with minimal observed side effects. Meloxicam and ketoprofen were found to be effective analgesics and well tolerated in cats with acute or chronic locomotor disorders when administered for short-term treatment (five days) in such cases. However, meloxicam was assessed to be significantly more palatable than ketoprofen.

Incidence of pneumothorax from intercostal nerve block for analgesia in rib fractures

BACKGROUND

The incidence of pneumothorax (PTX) after individual intercostal nerve block (INB) for postoperative pain reportedly varies from 0.073% to 19%.1-3 This study investigated the incidence of PTX after INB for rib fractures.

METHODS

We conducted a retrospective chart review of patients admitted between January 1996 and December 1999 with rib fractures who received INB.

RESULTS

One hundred sixty-one patients received 249 intercostal nerve block procedures (INBPs). An INBP is one session where a set of intercostal nerves are blocked. A total of 1,020 individual intercostal nerves were blocked. There were 14 pneumothoraces. The overall incidence of PTX per patient was 8.7%, with an incidence of PTX per INBP of 5.6%. The incidence of PTX was 1.4% for each individual intercostal nerve blocked.

CONCLUSION

The incidence of PTX per individual intercostal nerve blocked is low. INB is an effective form of analgesia, and for most patients with rib fractures one INBP is sufficient to allow adequate respiratory exercises and discharge from the hospital.

Behavioural effects of laparotomy and analgesic effects of ketoprofen and carprofen in rats

Rat behaviour was studied to develop a reliable method of determining the severity and duration of post-laparotomy pain, and to assess analgesic effects of ketoprofen or carprofen. Behaviour was studied in groups of ten animals 1 h following subcutaneous (s/c) saline (0.2 ml/100 g), ketoprofen or carprofen (5, 10 or 15 mg/kg) given either alone, or prior to surgery. The frequency of over 150 individual behavioural acts was calculated during the first post-treatment hour, the hour immediately prior to darkness, and the first 15 min of each of 5 subsequent hours. Discriminant analysis and analysis of variance isolated several easily recognizable behaviours which were markedly altered in frequency by surgery. These were unaffected by drug administration alone and were mainly transient, easily quantifiable activities; 'cat-like' back arching, horizontal stretching followed by abdominal writhing and twitching while inactive. Reductions in the frequency of these behaviours following surgery with analgesic treatment supported the hypothesis that they reflected post-operative pain. Ketoprofen and carprofen were equipotent and no dose related effects were apparent. Analgesic activity lasted between 4 and 5 h with the 5 mg/kg dosage, this being estimated from the duration of overall and specific behaviour differences between saline and drug treated animals. The data provided substantial evidence as to the usefulness of behavioural criteria for estimating pain severity, and for the first time, the basis of a system for routine pain assessment and management in rats subjected to abdominal surgery.

Analgesia and analgesic techniques

In recent years, there has been a great increase in our understanding of pain mechanisms and our awareness of pain in small animals. Despite increased knowledge, many animals still go undertreated or untreated. Small exotic animals are a unique group of patients, and can prove challenging for the practitioner concerned with their welfare. This article reviews the process of nociception and how one can intervene in the pain pathway. Newer analgesic drugs are discussed, along with some novel administration techniques that can be adapted for small mammals. Ketamine has been regarded primarily as a chemical restraining agent, but new information reveals that it may have an important place in pain management.

Estudo comparativo entre toracotomia intercostal, esternotomia mediana parcial e total em cães sadios (Canis familiaris ): avaliação clínica e hemogasométrica

O objetivo deste experimento foi comparar as alterações hemogasométricas e as possíveis complicações trans e pós-operatórias encontradas na toracotomia intercostal direita, esternotomia mediana parcial e esternotomia mediana total, determinando qual das técnicas produziu menor grau de intercorrências. Foram utilizados dezoito cães, sem raça definida, adultos, machos e fêmeas, com peso entre quinze e vinte quilos e em condições de saúde julgadas satisfatórias para o experimento. Os cães foram divididos em três grupos de seis animais, de acordo com a técnica cirúrgica empregada: GRUPO A -animais submetidos à toracotomia intercostal direita; GRUPO B - animais submetidos à esternotomia mediana parcial e GRUPO C - animais submetidos à esternotomia mediana total. Os cães foram avaliados quanto às possíveis intercorrências intra e pós-operatórias, alterações das freqüências cardíaca e respiratória, temperatura, oxigenação, ventilação, equilíbrio ácido-básico e dor. Durante sete dias foi feita avaliação da ferida cirúrgica, não observando-se intercorrências com cicatrização, infecção, presença de fístulas e deiscência de sutura. Os resultados obtidos foram analisados estatisticamente. Concluiu-se que as três técnicas foram exeqüíveis em cães, pois permitiram recuperação pós-operatória satisfatória e comparativamente não foram verificadas alterações significativas quanto ao pH, gases sangüíneos e dor.

Subjective and objective measurements of postoperative pain in cats

OBJECTIVE

To evaluate the ability of various subjective and objective measurements to determine the presence and degree of postoperative pain in cats.

DESIGN

Randomized controlled prospective clinical study.

ANIMALS

18 healthy client-owned cats.

PROCEDURE

Cats were randomly assigned to 3 groups of 6: control, tenectomy, and onychectomy. Jugular catheters were placed the day prior to surgery. All surgeries were performed by the same surgeon, and all observations were made by the same blinded trained observer. One hour prior to surgery and at assigned intervals for 36 hours after surgery, heart rate, respiratory rate, and rectal temperature were measured. Scores were assigned for 3 interaction responses, including response to palpation, by use of simple descriptive scales, and to 2 pain assessments by use of visual analogue scales. Blood was collected to measure plasma beta-endorphin and cortisol concentrations. Butorphanol was administered to all cats before surgery and to any cat subjectively assessed to be experiencing pain after surgery.

RESULTS

Only visual analogue scale scores and response to palpation scores differed significantly between control and surgical groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Determination of the presence of pain in cats can be made on the basis of observation and interaction by a trained observer. Physiologic measurements, including plasma cortisol and beta-endorphin concentrations, did not differentiate between control cats and cats that underwent surgery.

Local and regional anesthesia

Local anesthetics have the unique ability to produce complete blockade of sensory nerve fibers and prevent or pre-empt the development of secondary (central) sensitization to pain. For this reason, local and regional anesthetic techniques are often used with opioids, alpha 2-receptor agonists, dissociatives, and anti-inflammatory drugs as part of a multimodal strategy to manage pain. Lidocaine and bupivacaine are the local anesthetics used most commonly in dogs and cats. Lidocaine has a fast onset (10-15 min) and an intermediate duration of action (60-120 min), and is used for short diagnostic and surgical procedures. Bupivacaine has a slow onset (20-30 min) and a long duration of action (240-360 min), and is used to control pain both preoperatively and postoperatively. Local anesthetics are relatively safe if they are administered correctly. Administration of an excessive dose and accidental intravenous administration are probably the most common causes of systemic toxicity in small animals. Doses of local anesthetics, especially those for cats and small dogs, should always be calculated carefully. In many animals, the most simple and elegant way to control pain perioperatively is to perform a local or regional anesthetic block. Veterinarians should not hesitate to incorporate local and regional anesthetic techniques into their pain management strategies for dogs and cats.

Acute pain management

We encounter patients with acute pain many times each day, and few aspects of veterinary practice offer such an opportunity to help so many in such a profoundly rewarding way. As emphasized here and elsewhere, we now have excellent tools with which to help these animals, and the biggest impediment to optimal treatment of their pain is often our own difficulty in recognizing its presence. Perhaps the single most important aspect of treating acute pain is to cultivate an ability to see past our personal biases and expectations which may limit treatment and to rediscover the common sense we had about pain before we entered the profession. By rededicating ourselves to seeking out, preventing, and relieving pain, we not only perform a vital service for our patients but also elevate our profession even as we reap financial and spiritual rewards for our efforts. What could be better?

The effects of ovariohysterectomy plus different combinations of halothane anaesthesia and butorphanol analgesia on behaviour in the bitch

One hundred and sixty-six behaviours were identified as possible indices of post-operative pain-induced distress in the bitch. These were assessed in bitches after treatment with different combinations of halothane and butorphanol in the absence of surgery and following ovariohysterectomy under halothane anaesthesia with or without butorphanol analgesia given at different stages during the operation. Behaviour was monitored while the bitches were alone (non-interactive) and when routinely examined and handled prior to blood sampling (interactive). Seventy-six of the 166 behaviours occurred so infrequently (less than two occurrences per hour) as to be of no value as indices. Non-interactive behaviours associated with surgery were a decrease in normal speed cage circling and an increase in drawing the rear limbs up in the pike position. The infrequent non-interactive behaviours of incision licking, vomiting and flank gazing were considered to be expressions of pain caused by ovariohysterectomy. During the post-surgical period, bitches given analgesic moved less frequently than those not receiving analgesic. Vocalisation was associated with dysphoria of analgesia rather than pain-induced distress. The behaviour of bitches after ovariohysterectomy suggests that this is a painful procedure which warrants analgesia.

Thoracoscopic versus open partial pericardectomy in dogs: comparison of postoperative pain and morbidity

OBJECTIVE

To evaluate postoperative pain and morbidity in dogs undergoing open thoracotomy and partial pericardectomy versus thoracoscopic pericardectomy.

STUDY DESIGN

Research study in normal dogs.

ANIMALS OR SAMPLE POPULATION

Fourteen mixed breed healthy dogs.

METHODS

Seven dogs had a partial pericardectomy through a standard left lateral thoracotomy at the fifth intercostal space. The remaining seven dogs underwent selective lung ventilation and thoracoscopic partial pericardectomy. Surgery sites in both groups were bandaged and each dog received a single postoperative dose of morphine (0.2 mg/kg, intramuscularly [i.m.]). Postoperative pain was evaluated using a standard pain score table at 1, 5, 9, 17, 29, and 53 hours after surgery. Dogs receiving a pain score of six or greater received an additional dose of morphine. At each observation point, blood samples were taken to measure blood glucose and plasma cortisol concentrations. Pain scores, blood glucose, and plasma cortisol concentrations were compared between the two groups using two-way ANOVA.

RESULTS

Blood glucose concentrations, plasma cortisol concentrations, and pain scores were significantly different between the two groups, with the thoracotomy dogs having higher values at 1, 5, and 9 hours postoperatively. Three of the open thoracotomy dogs required additional analgesia after the initial dose of morphine. In addition, two dogs that underwent open thoracotomy were lame in the left forelimb and two others developed dehiscence of their wounds.

CONCLUSIONS AND CLINICAL RELEVANCE

Thoracoscopic partial pericardectomy has several advantages over open partial pericardectomy including decreased postoperative pain, fewer wound complications, and more rapid return to function.

Assessment of the respiratory actions of intramuscular morphine in conscious dogs

The actions on the respiratory system of 0.25, 0.5 and 1.0 mg kg(-1) morphine given intramuscularly were studied in conscious dogs. Dogs breathed oxygen with 0, 2 and 4 per cent CO(2), in that order, through a mask attached to a flow sensor and connected to a respiratory mechanics monitor. When a steady state period of respiration was reached breathing pure oxygen, respiratory rate, tidal volume, respiratory minute volume, peak expiratory flow rate and end tidal CO(2)(PetCO(2)) were measured. The respiratory minute volume and PetCO(2) were measured when the dogs breathed 2 and 4 per cent CO(2) in oxygen, the points plotted onto a graph and the gradient of the line, describing the PCO(2)/ventilation response, plus the intercept with the y-axis were determined. Measurements for each morphine dose were taken before injection and at 30 minutes, 1, 2, 3, 4, 6 and 8 hours post injection. The incidence of panting after morphine was dose related and it occurred in all dogs given the high dose. Morphine reduced the gradients of the PCO(2)/ventilation response lines and raised the intercept. Other changes were increased respiratory minute volume and peak expiratory flow and decreased PetCO(2) and tidal volume.

Analgesics and pain

There has been a substantial increase in the use of analgesics for pain management in the last 10 years. Traditionally, veterinarians have not been trained in the identification of or monitoring of patients that are in pain, even though an evaluation of pain is inherent in assessing improvement in many medical and surgical diseases. Until recently, the physiology and pharmacology of opioids, NSAIDs, local anesthetics, and alpha 2 agonists were taught, but the therapeutic role of these drugs was generally believed to be related to restraint, anesthesia, or control of inflammation rather than to pain management.

Comparison of transdermal fentanyl and intramuscular oxymorphone on post-operative behaviour after ovariohysterectomy in dogs

The effects of transdermal fentanyl and i.m. oxymorphone on behavioural and physiological responses, after ovariohysterectomy in dogs, were investigated. The study involved three groups of 10 dogs: fentanyl/surgery (FS), oxymorphone/surgery (OS), fentanyl/control (FC). A transdermal fentanyl delivery system (50 microg hour(-1)) (FS and FC) was applied 20 hours before surgery, or i.m. oxymorphone (OS) was administered. After ovariohysterectomy (FS and OS) or anaesthesia alone (FC), dogs were continuously videotaped for 24 hours and a standardised hourly interaction with a handler performed. The videotapes were analysed, and interactive and non-interactive behaviours evaluated. In addition, pain and sedation scores, pulse and respiratory rates, rectal temperature, arterial blood pressure, plasma cortisol and plasma fentanyl concentrations were measured. This study showed that transdermal fentanyl and i.m. oxymorphone (0.05 mg kg(-1)) produced comparable analgesic effects over a 24 hour recording period. I.m. oxymorphone produced significantly more sedation and lower rectal temperatures than transdermal fentanyl. There were no significant differences between groups in respiratory and heart rates, and arterial blood pressures.

Pain and its management

The management of pain in geriatric patients is a critical part of good veterinary care. The older patient poses unique issues in the selection of appropriate analgesic drugs due to altered drug absorption, metabolism and the frequent occurrence of underlying disease. Narcotics and NSAIDs are important analgesics that can be safely administered in geriatric patients provided that dosing amount and frequency are adjusted. Alternative analgesic techniques, such as nerve blocks, spinal analgesia and transcutaneous patches, offer a particularly useful source of analgesia in compromised geriatric patients.

Local and regional anesthesia and analgesia

Many benefits can be obtained from the use of drugs applied locally or regionally when treating dogs and cats that are in pain or will be in pain because of surgical trauma. These techniques often use less medication than for systemic administration with a reduction in the likelihood of toxic effects from these compounds. Complete relief of pain can be achieved by blocking nerves originating from the site of injury by using local anesthetics, but this may entail loss of all sensation and motor paralysis. Other drugs, such as the opioids, may decrease the nociceptive input with minimal effect on motor activity. This report discusses the use of local anesthetics and other drugs for analgesia of the skin, mucous membranes, joints, pleura, and peritoneum, and the application of these drugs for regional blocks of peripheral nerves and epidural/intrathecal injection.

Review of the technique and complications of median sternotomy in the dog and cat

The surgical and medical records of 67 dogs and nine cats which underwent median sternotomy over a five-year period were reviewed. The indication for median sternotomy and the short and longer term complications were recorded. Twenty-six of the dogs died or were euthanased within 48 hours of the surgery as a consequence of the pre-existing disease or complications of the intrathoracic surgical procedure. A further four dogs were enthanased between 48 hours and 14 days following confirmation of neoplastic processes. Thirty-seven dogs were alive at 14 days: of these, seven dogs (19 per cent) experienced short-term wound complications, including haemorrhage, wound infection, thoracic limb neurological deficits and excessive postoperative discomfort. Of the 37 dogs alive for longer term follow-up, eight dogs (22 per cent) experienced wound complications, including haemorrhage, sternal fracture, sternal osteomyelitis and delayed wound healing. No complications were noted in the cats.

Comparison of three methods for relief of pain after ear canal ablation in dogs

This study compared three methods of pain relief in dogs that had total ear canal ablation with lateral bulla osteotomy. The hypothesis was that systemic opioids with preoperative local nerve blocks would provide superior pain relief. Thirty-one dogs with chronic otitis externa were included in the study. Dogs were randomly assigned to one of three protocols: systemic opioids alone (10 dogs, group 1), systemic opioids with bupivacaine splash block (11 dogs, group 2), and systemic opioids with preoperative local bupivacaine nerve blocks (10 dogs, group 3). Twenty-one dogs had bilateral ear ablation and 10 had unilateral ablation. Pain was assessed preoperatively, at extubation, 2 hours postextubation, and 1 day postoperatively by a single observer blinded to the analgesic protocol used. Pain scores were not significantly different within or between groups, nor did unilateral versus bilateral ablation have a significant effect on the score. Mean scores were less than 3 (scale 1 to 5) for all groups at all observation times. Rough recoveries were noted in 30% of group 1 dogs, 0% of group 2, and 20% of group 3 dogs. Ninety-four percent of dogs were moderately to heavily sedated at extubation. Sixty percent of group 3 dogs remained moderately to heavily sedated 2 hours postextubation. Rectal temperature, pulse rate, respiratory rate, and postoperative change in serum cortisol levels were not significantly different between groups. Postoperative increase in blood glucose was significantly higher in groups 1 and 3 compared with preoperative levels. Twenty-three percent of the dogs required additional analgesia or tranquilization after surgery, as determined by the anesthetist; 1 dog in group 1, 2 in group 2, and 4 in group 3. Each of the three analgesic protocols provided similar pain relief in dogs undergoing total ear canal ablation.

Postoperative analgesia for stifle surgery: a comparison of intra-articular bupivacaine, morphine, or saline

A prospective study was undertaken to compare the analgesic effect of intra-articular bupivacaine, morphine, or saline in the 24-hour period following cranial cruciate ligament repair in dogs. Thirty-six clinical patients with ruptured cranial cruciate ligaments were randomly assigned to one of three groups. After surgical stabilization, and before skin closure, an intra-articular injection was given; group one (n = 12) received 0.5% bupivacaine HCl at 0.5 mL/kg, group two (n = 12) received morphine at 0.1 mg/kg diluted with saline to a volume of 0.5 mL/kg, and group three (n = 12) received saline at 0.5 mL/kg. Heart rate, respiratory rate, mean arterial blood pressure, cumulative pain score, visual analog pain score, and pain threshold test on both stifles were recorded preoperatively and at 0 to 6 and 24 hours postoperatively. Surgeons and pain scoring investigators were unaware of the intra-articular medication given. Supplemental analgesia, if needed, was provided in the postoperative period according to subjective assessment of patient discomfort. Postoperative pain scores were lowest in the bupivacaine group and highest in the saline group. Pain threshold, measured by applying calibrated loads to the knee, was higher postoperatively in the bupivacaine group than in the saline group. Dogs in the morphine and bupivacaine groups required less supplemental analgesia than dogs in the saline group. The local provision of analgesia reduces the need for systemic drugs with potential side effects. Both intra-articular morphine and intra-articular bupivacaine provided better postoperative analgesia than intra-articular saline, with intra-articular bupivacaine showing the greatest effect.

Evaluation of the hemodynamic effects of interpleural bupivacaine in dogs

The hemodynamic effects of interpleural (IP) bupivacaine were studied in six halothane-anesthetized dogs. On four separate occasions, each dog received IP saline (S), or bupivacaine at a low dosage of 1.5 mg/kg (L), high dosage of 3.0 mg/kg (H), or high dosage of 3.0 mg/kg with epinephrine 5 micrograms/mL (HE). Heart rate, systolic and mean arterial pressures, and base excess were significantly lower in the H dosage group than in the other treatment groups. Cardiac output, expressed as a percentage of change from baseline, was significantly higher in the L group than in the H and S groups. Pulmonary arterial pressure and respiratory rate were significantly higher in the HE group than in the other three groups. Mean plasma concentrations of bupivacaine peaked between 5 and 15 minutes after IP injection. Maximum plasma concentrations in individual dogs were variable; however, mean maximum plasma concentrations in the H and HE groups were not significantly different. Clinically significant hypotension occurred in one dog in the H group and in one dog in the HE group. No pulmonary complications were detected.

Pharmacological management of pain and infection in the surgical oncology patient

Surgical oncology patients are often high-risk patients that require careful perioperative management for a successful outcome. Prophylactic antibiotics are needed to prevent infection in tissues compromised by disease, radiation, or chemotherapy. Pain control is needed to prevent the stress response to surgery from worsening the outcome and to aid in the maintenance of patient comfort.

Analgesia in dogs after intercostal thoracotomy: a clinical trial comparing intravenous buprenorphine and interpleural bupivacaine

We prospectively studied 26 dogs that presented for intercostal thoracotomy. Dogs were premedicated with oxymorphone, induced with diazepam and etomidate, and anesthesia was maintained with isoflurane in oxygen. Preoperatively, animal patients were randomly assigned to one of two groups. Group 1 (n = 13) received buprenorphine (10 microgram/kg intravenously [IV]) every 6 hours for 24 hours starting 10 minutes before tracheal extubation. Group 2 (n = 13) received 0.5% bupivacaine (1.5 mg/kg) administered interpleural (IP) by slow injection through a pediatric feeding tube fixed to the most dorsal aspect of the thoracotomy incision. Interpleural injections were administered with each dog placed in lateral recumbency with the incision positioned ventrally; IP injections were administered every 4 hours for 24 hours starting 10 minutes before tracheal extubation. All cases were monitored in the intensive care unit for 24 hours postoperatively. The analgesic efficacy of each regimen was evaluated using a pain scoring system that included a subjective pain score, heart rate, and respiratory rate. Arterial blood pressure, arterial blood gases, oxygen saturation, body temperature, and changes in the electrocardiogram or neurological status were also noted. Significant increases in mean heart rate, respiratory rate, and total pain score occurred after surgery in dogs in the buprenorphine group. In contrast, dogs in the bupivacaine group had no significant changes when compared with their preoperative values. Dogs in the bupivacaine group had significantly decreased total pain scores and better PaO2 and oxygen saturation values when compared with the dogs receiving buprenorphine. Hypoventilation did not occur in either group.

Analgesia after lateral thoracotomy in dogs. Epidural morphine vs. intercostal bupivacaine

One of two analgesic treatments was randomly assigned to 40 dogs undergoing lateral thoracotomy. Group E (20 dogs) received an epidural injection of morphine (0.1 mg/kg) before surgery. Group I (20 dogs) received injections of bupivacaine around five intercostal nerves when the thorax was about to be closed. All dogs were given an opioid as part of their preoperative medication (meperidine or butorphanol), followed by thiopental for induction and halothane or methoxyflurane for maintenance of anesthesia. Scores were assigned for pre-operative demeanor and response to restraint and injection. Alertness, undisturbed pain behavior, and response to palpation of the wound were assessed 3, 6, 12, and 24 hours after surgery. Dogs that appeared uncomfortable were given analgesics. Blood for evaluation of arterial blood gases was obtained at 3 and 6 hours after surgery. The person scoring the dogs was blinded to the treatment given. There were no statistically significant differences between the groups. Group E contained more "nervous" dogs (12 vs. 6) and more dogs in group E received postoperative analgesics (8 vs. 2). Both techniques appeared to provide adequate analgesia for most dogs.