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

ObjectiveTo investigate the analgesic and side effects of epidural morphine or a fentanyl patch after ovariohysterectomy in dogs.Study designProspective, randomized clinical study.AnimalsTwenty female mongrel dogs undergoing ovariohysterectomy.MethodsThe dogs were allocated to one of two groups: epidural morphine or transdermal fentanyl patch. Anaesthesia was induced with propofol and maintained with isoflurane. Morphine (0.1 mg kg^?1) was administered epidurally in the epidural morphine group and a transdermal fentanyl patch was applied 24 hours before the operation in the fentanyl patch group.The heart rate, respiratory rate, body temperature, plasma cortisol concentration, and sedation and analgesia scores were recorded during the 24 hour post-operative period. Adverse effects such as vomiting, anorexia, skin reactions, urinary retention, and time to start licking the surgical site were also recorded. p < 0.05 was considered significant. Statistical analyses utilized anova for repeated measures, Friedman tests, Mann-Whitney U-tests and independent sample t-tests as relevant.ResultsPain scores were lower in the epidural group than in the fentanyl group at all post-operative times. The dogs in the epidural morphine group were calm and relaxed, whereas discomfort and vocalization were recorded in the fentanyl patch group. The sedation scores were higher in the fentanyl patch group throughout the 12 hour period. Salivation and anorexia lasted longer in the fentanyl patch group than in the epidural morphine group. Plasma cortisol concentrations were high in the early post-operative period in both groups. The fentanyl patch group had higher cortisol concentrations than the epidural morphine group. Slight erythema was recorded in two dogs when the patches were removed.Conclusion and clinical relevanceEpidurally administered morphine provided better analgesia and caused fewer adverse effects than the fentanyl patch after ovariohysterectomy in dogs.     

The effect of neuraxial morphine on postoperative pain in dogs after extrahepatic portosystemic shunt attenuation

ObjectiveTo investigate the analgesic effect of epidural morphine after surgical extrahepatic portosystemic shunt (EHPSS) attenuation.Study designRandomized clinical trial.AnimalsA total of 20 dogs with a congenital EHPSS.MethodsDogs were randomly allocated to be given either a single epidural dose of 0.2 mg kg^–1 preservative-free morphine (group M) or not (group C) before surgery. All dogs were administered 0.3 mg kg^–1 methadone intravenously (IV) as preanaesthetic medication. Pain scores were determined every 2 hours for the first 24 hours postoperatively using the short-form Glasgow Composite Measure Pain Scale (GCMPS-SF). Dogs with a GCMPS-SF pain score >4/20 or >5/24 received 0.1 mg kg^–1 methadone IV as rescue analgesia and were reassessed 30 minutes later. If more than three doses of methadone were administered in a 2 hour period, alternative pain relief was provided and a treatment failure recorded. The GCMPS-SF pain scores and number of rescue analgesia injections were analysed over 24 hours. The last observation carried forward method was applied in case of treatment failure. Food consumption and time to first urination were recorded. Data were analysed using a Mann–Whitney U test and presented as median (minimum–maximum range), with significance set at p < 0.05.ResultsGroup M showed lower GCMPS-SF pain scores [15 (11–41) versus 31 (11–86); p = 0.023] and lower postoperative methadone requirements [0 (0–0.2) versus 0.25 (0–0.5) mg kg^–1; p = 0.029] than group C. There were three treatment failures in group C only. Food consumption and time to first urination did not differ between groups.Conclusions and clinical relevanceEpidural morphine reduced the requirement for postoperative analgesia in this study population.     

Evaluation of analgesic and physiologic effects of epidural morphine administered at a thoracic or lumbar level in dogs undergoing thoracotomy

ObjectiveTo evaluate the analgesic and physiological effects of epidural morphine administered at the sixth and seventh lumbar or the fifth and sixth thoracic vertebrae in dogs undergoing thoracotomy.Study designProspective, randomized, blinded trial.AnimalsFourteen mixed-breed dogs, weighing 8.6 ± 1.4 kg.MethodsThe animals received acepromazine (0.1 mg kg^?1) IM and anesthesia was induced with propofol (4 mg kg^?1) IV. The lumbosacral space was punctured and an epidural catheter was inserted up to the region between the sixth and seventh lumbar vertebrae (L, n = 6) or up to the fifth or sixth intercostal space (T, n = 8). The dogs were allowed to recover and after radiographic confirmation of correct catheter position, anesthesia was reinduced with propofol IV and maintained with 1.7% isoflurane. Following stabilization of monitored parameters, animals received morphine (0.1 mg kg^?1) diluted in 0.9% NaCl to a final volume of 0.25 mL kg^?1 via the epidural catheter, and after 40 minutes, thoracotomy was initiated. Heart rate and rhythm, systolic, mean and diastolic arterial pressures, respiratory rate, arterial hemoglobin oxygen saturation, partial pressure of expired CO₂ and body temperature were measured immediately before the epidural administration of morphine (0 minute) and every 10 minutes during the anesthetic period. The Melbourne pain scale and the visual analog scale were used to assess post-operative pain. The evaluation began 3 hours after the epidural administration of morphine and occurred each hour until rescue analgesia.ResultsThere were no important variations in the physiological parameters during the anesthetic period. The post-operative analgesic period differed between the groups, being longer in T (9.9 ± 1.6 hours) compared with L (5.8 ± 0.8 hours).ConclusionsThe use of morphine, at a volume of 0.25 mL kg^?1, administered epidurally over the thoracic vertebrae provided longer lasting analgesia than when deposited over the lumbar vertebrae.Clinical relevanceThe deposition of epidural morphine provided longer lasting analgesia when administered near to the innervation of the injured tissue without increasing side effects.     

Comparison of epidural versus intrathecal anaesthesia in dogs undergoing pelvic limb orthopaedic surgery

ObjectiveTo compare the procedural failure rate (PFR), intraoperative rescue analgesia (iRA) probability and postoperative duration of motor block after epidural and intrathecal anaesthesia in dogs undergoing pelvic limb orthopaedic surgery.Study designProspective, randomized clinical trial.AnimalsNinety-two client-owned dogs.MethodsDogs were assigned randomly to receive either lumbosacral epidural anaesthesia (EA) (bupivacaine 0.5% and morphine 1%) or intrathecal anaesthesia with the same drugs in a hyperbaric solution (HIA). Inaccurate positioning of the needle, assessed by radiographic imaging, and lack of cerebral spinal fluid outflow were considered procedural failures (PFs) of EA and HIA, respectively. Fentanyl (1 μg kg⁻¹ IV) was provided for intraoperative rescue analgesia, when either the heart rate or the mean arterial pressure increased by 30% above the pre-stimulation value. Its use was recorded as a sign of intraoperative analgesic failure. The motor block resolution was evaluated postoperatively. Variables were compared using Fisher's exact test, the Mann–Whitney U test and the Kaplan–Meier ‘survival’ analysis as relevant.ResultsThe PFRs in the EA and HIA groups were 15/47 (32%) and 3/45 (7%), respectively (p = 0.003). Differences in iRA were analysed in 26 and 30 subjects in the EA and HIA groups respectively, using Kaplan–Meier survival analysis. The iRA probability within the first 80 minutes of needle injection (NI) was higher in the EA group (p = 0.045). The incidence of dogs walking within 3 hours of NI was significantly higher in the HIA group (8/20, 40%) than in the EA group (0/17) (p = 0.004).Conclusions and clinical relevanceHIA was found to have lower PF, lower intraoperative analgesic failure and faster motor block resolution. In this study HIA was shown to provide some advantages over EA in dogs undergoing commonly performed pelvic limb orthopaedic surgery in a day-hospital regime.     

Anaesthetic,analgesic and cardiorespiratory effects of intramuscular medetomidine‐ketamine combination alone or with morphine or tramadol for orchiectomy in cats

ObjectivesTo compare the anaesthetic, analgesic and cardiorespiratory effects of intramuscular (IM) medetomidine and ketamine administered alone or combined with morphine or tramadol, for orchiectomy in cats.Study designRandomised, blinded, prospective clinical study.AnimalsThirty client-owned cats.Materials and methodsCats (n = 10 in each group) received a combination of medetomidine (60 μgkg^?1) and ketamine (10 mg kg^?1) alone (MedK); combined with morphine (0.2 mg kg^?1) (MedKM), or combined with tramadol (2 mg kg^?1) (MedKT) IM. Time of induction, surgical and recovery events were recorded, and physiological parameters measured and recorded. Analgesia was evaluated with a visual analogue scale, a composite scoring system and the von Frey mechanical threshold device, every hour from three to eight hours post-drug administration injection. Data were analyzed with a linear mixed model, Kruskal–Wallis or Chi-square tests (p < 0.05).ResultsMedian (IQR) induction and recovery times (minutes) were not significantly (p = 0.125) different between groups: 5.6 (2.7–8.0), 7.4 (5.1–9.6) and 8.0 (5.8–14.9) for induction and 128.5 (95.1–142.8), 166.4 (123.1–210.0) and 142.9 (123.4–180.2) for recovery, with MedK, MedKT and MedKM, respectively. Two cats (MedKM) required alfaxalone for endotracheal intubation. In all groups, three or four cats required additional isoflurane for surgery. Arterial oxygen tension overall (mean ± SD: 66 ± 2 mmHg) was low. Surgery resulted in increased systolic arterial blood pressure (p < 0.001), haemoglobin saturation (p < 0.001), respiratory (p = 0.003) and heart rates (p = 0.002). Pain scores did not differ significantly between groups. Von Frey responses decreased over time; changes over time varied by treatment (p < 0.001), MedK returning to baseline values more rapidly than MedKM and MedKT. No cat required rescue analgesics.Conclusion and clinical relevanceAll three protocols can provide adequate anaesthesia and analgesia for orchiectomy in cats. However, rescue intervention to maintain surgical anaesthesia may be required in some cats. Oxygen supplementation is advised.     

Post-operative analgesic effects of butorphanol or firocoxib administered to dogs undergoing elective ovariohysterectomy

ObjectiveTo compare the post-operative analgesic effects of butorphanol or firocoxib in dogs undergoing ovariohysterectomy.Study designProspective, randomized, blinded, clinical trial.AnimalsTwenty-five dogs >1 year of age.MethodsDogs received acepromazine intramuscularly (IM), 0.05 mg kg^?1 and either butorphanol IM, 0.2 mg kg^?1 (BG, n = 12) or firocoxib orally (PO), 5 mg kg^?1 (FG, n = 13), approximately 30 minutes before induction of anesthesia with propofol. Anesthesia was maintained with isoflurane. Ovariohysterectomy was performed by the same surgeon. Pain scores using the dynamic and interactive visual analog scale (DIVAS) were performed before and at 1, 2, 3, 4, 6, 8 and 20 hours after the end of surgery by one observer, blinded to the treatment. Rescue analgesia was provided with morphine (0.5 mg kg^?1) IM and firocoxib, 5 mg kg^?1 (BG only) PO if DIVAS > 50. Groups were compared using paired t-tests and Fisher’s exact test (p < 0.05). Data are presented as mean ± SD.ResultsThe BG required significantly less propofol (BG: 2.6 ± 0.59 mg kg^?1; FG: 5.39 ± 0.7 mg kg^?1) (p < 0.05) but the anesthesia time was longer (BG: 14 ± 6, FG: 10 ± 4 minutes). There were no differences for body weight (BG: 7.9 ± 5.0, FG: 11.5 ± 4.6 kg), sedation scores, and surgery and extubation times (BG: 10 ± 2, 8 ± 5 minutes; FG: 9 ± 3, 8 ± 4 minutes, respectively) (p > 0.05). The FG had significantly lower pain scores than the BG at 1, 2 and 3 hours following surgery (p < 0.05). Rescue analgesia was administered to 11/12 (92%) and 2/13 (15%) dogs in the BG and FG, respectively (p < 0.05).Conclusion and clinical relevanceFirocoxib produced better post-operative analgesia than butorphanol. Firocoxib may be used as part of a multimodal analgesia protocol but may not be effective as a sole analgesic.     

Comparison of analgesia provided by lidocaine, lidocaine-morphine or lidocaine-tramadol delivered epidurally in dogs following orchiectomy

ObjectiveTo evaluate and compare the postoperative analgesia provided by epidural lidocaine, lidocaine/morphine or lidocaine/tramadol in dogs following elective orchiectomy.Study designProspective experimental trial.AnimalsThirty-six mongrel dogs aged 2-8 years old, weighing 6.6-22 kg.MethodsThe dogs received 6.0 mg kg^?1 of lidocaine combined with 1.0 mg kg^?1 of tramadol, 0.1 mg kg^?1 of morphine or 0.01 mL kg^?1 of 0.9% NaCl epidurally. Analgesia was assessed at 4, 8, 12, 18 and 24 hours (T4, T8, T12 and T24) after the offset of lidocaine using a scale composed of physiologic and behavioral parameters. Rescue analgesia with morphine (0.2 mg kg^?1, IM) was performed if the evaluation score exceeded 10 during the postoperative period. The scores over time were analyzed using the Friedman’s two-way analysis of variance and the comparison between groups was made by the Kruskal-Wallis test with statistical significances accepted if p = 0.05.ResultsThere were no differences in the pain scores between the morphine and tramadol groups over time and no rescue analgesia was administered. In the NaCl group, rescue analgesia was needed at T4, T8 and T12. Within this group, the final evaluation times (T18 and T24) had lower pain scores than at T4, T8 and T12.Conclusions and clinical relevanceEpidural lidocaine/tramadol provided an analgesic effect comparable to that of epidural lidocaine/morphine during the first 12 hours after surgical castration without substantial side effects, suggesting that tramadol may be an effective postoperative analgesic in dogs submitted to this surgical procedure.     

Effect of intraperitoneal or incisional bupivacaine on pain and the analgesic requirement after ovariohysterectomy in dogs

ObjectiveTo compare the effect of intraperitoneal (IP) or incisional (INC) bupivacaine on pain and the analgesic requirement after ovariohysterectomy in dogs.Study designProspective, randomized clinical study.AnimalsThirty female dogs undergoing ovariohysterectomy (OHE).MethodsDogs admitted for elective OHE were anesthetized with acepromazine, butorphanol, thiopental and halothane. Animals were randomly assigned to one of three groups (n = 10 per group). The treatments consisted of preincisional infiltration with saline solution (NaCl 0.9%) or bupivacaine with epinephrine and/or IP administration of the same solutions, as follows: INC and IP 0.9% NaCl (control group); INC 0.9% NaCl and IP bupivacaine (5 mg kg^?1, IP group); INC bupivacaine (1 mg kg^?1) and IP 0.9% NaCl (INC group). Postoperative pain was evaluated by a blinded observer for 24 hours after extubation by means of a visual analog scale (VAS) and a numeric rating scale (NRS). Rescue analgesia (morphine, 0.5 mg kg^?1, IM) was administered if the VAS was >5/10 or the NRS >10/29.ResultsAt 1 hour after anesthesia, VAS pain scores were [medians (interquartile range)]: 6.4 (3.1–7.9), 0.3 (0.0–2.6) and 0.0 (0.0–7.0) in control, IP and INC groups, respectively. VAS pain scores were lower in the IP compared to the control group. Over the first 24 hours, rescue analgesia was administered to 7/10, 5/10 and 3/10 dogs of the control, INC and IP groups, respectively. Total number of dogs given rescue analgesia over the first 24 hours did not differ significantly among groups.Conclusions and clinical relevanceIntraperitoneal bupivacaine resulted in lower pain scores during the first hour of the postoperative period and there was a trend towards a decreased need for rescue analgesia after OHE in dogs.     

Epidural administration of combinations of ropivacaine,morphine and xylazine in bitches undergoing total unilateral mastectomy: a randomized clinical trial

ObjectiveTo investigate the epidural administration of combinations of ropivacaine, morphine and xylazine in bitches undergoing unilateral mastectomy.Study designProspective, randomized, blinded, clinical study.AnimalsA total of 22 bitches scheduled to undergo unilateral mastectomy for mammary tumor excision.MethodsDogs were anesthetized with acepromazine (0.02 mg kg^–1) and morphine (0.3 mg kg^–1) intramuscularly, propofol intravenously (IV) and isoflurane. Prior to the beginning of surgery, dogs were randomly administered one of three epidural treatments: ropivacaine (0.75 mg kg^–1) with morphine (0.1 mg kg^–1) (group RM, n = 7); ropivacaine with xylazine (0.1 mg kg^–1) (group RX, n = 8); or ropivacaine with morphine and xylazine (group RMX, n = 7). Cardiopulmonary variables and the expired concentration of isoflurane (Fe′Iso) were recorded intraoperatively. Meloxicam (0.1 mg kg^–1) was administered IV during skin closure. Postoperative pain scores were evaluated with the Glasgow composite measure pain scale short form for 24 hours, and rescue analgesia with morphine (0.5 mg kg^–1) was administered intramuscularly when pain scores were ≥ 6/24.ResultsFe′Iso was significantly higher in group RM than in groups RX and RMX. Heart rate decreased significantly in groups RX and RMX, but blood pressure remained within acceptable values. The number of dogs administered rescue analgesia within 24 hours was significantly higher in group RX (seven dogs, 87.5%) than in groups RM (one dog, 14.3%; p = 0.01) and RMX (two dogs, 28.6%; p = 0.04). Time to standing was significantly longer in group RX than in group RM.Conclusions and clinical relevanceAll epidural treatments provided adequate antinociception with minimal cardiovascular adverse effects during mastectomy. The inclusion of morphine (groups RM and RMX) provided the best postoperative analgesia. Owing to the undesirable effect of xylazine on ambulation, the combination ropivacaine–morphine appeared to provide greater benefits in bitches undergoing unilateral mastectomy.     

Effect of extradurally administered morphine on postoperative analgesia in dogs undergoing surgery for thoracolumbar intervertebral disk extrusion

Objective-To investigate the effect of intraoperative extradural morphine administration on postoperative analgesia in dogs undergoing thoracolumbar spinal surgery to treat disk extrusion. Design-Prospective clinical trial. Animals-26 client-owned dogs undergoing thoracolumbar spinal surgery. Procedures-Animals were randomly allocated to receive morphine (0.1 mg/kg [0.045 mg/lb], extradurally) or no treatment (control group). Following preanesthetic medication with methadone (0.25 mg/kg [0.11 mg/lb], IM), anesthesia was induced with propofol and maintained with isoflurane or sevoflurane in oxygen. Lidocaine and fentanyl were administered during surgery in both groups at fixed rates. In the morphine administration group, morphine was splashed over the dura mater immediately prior to wound closure. Postoperative analgesia was assessed for 48 hours by assessors unaware of group allocation, and methadone was administered as rescue analgesic. Demographic characteristics, urinary output, days of hospitalization, and perioperative use of analgesics were compared via a Mann-Whitney U test. Results-Demographic data were similar between groups. In the morphine administration group, 2 of 13 dogs required postoperative methadone, and in the control group, methadone was administered to 11 of 13 dogs. The total number of doses of methadone administered in the 48 hours after surgery was 28 in the control group and 3 in the morphine administration group. No adverse effects were recorded in any group. Conclusions and Clinical Relevance-Intraoperative extradural morphine administration was effective in reducing postoperative analgesic requirement. Dogs undergoing thoracolumbar spinal surgery benefited from topical administration of preservative-free morphine administered directly on the dura mater as part of analgesic management.     

A comparison of epidural morphine with low dose bupivacaine versus epidural morphine alone on motor and respiratory function in dogs following splenectomy

ObjectiveTo compare post-operative motor function in dogs that received epidural morphine and low dose bupivacaine versus epidural morphine alone following splenectomy.Study designProspective, randomized study.Animals16 client owned dogs undergoing routine splenectomy.MethodsFollowing splenectomy dogs were randomly allocated into one of two groups. The morphine group (MOR) was administered epidural morphine (0.1 mg kg^?1); the morphine-bupivacaine group (MORB) received epidural morphine (0.1 mg kg^?1) and low dose bupivacaine [0.25 mg kg^?1, (0.167%)]. The adjusted final volume was 0.15 mL kg^?1 in both groups. Motor function and pain assessment were performed at pre-determined times using a simple numerical motor score and the University of Melbourne Pain Scale (UMPS) respectively. An arterial blood gas was performed 2 hours following epidural administration to check for respiratory compromise. If patients scored >7 on the UMPS or were deemed painful by the observer they were administered hydromorphone intravenously and dose and time of rescue analgesia were recorded.ResultsThere were no statistically significant differences in motor scores, pain scores, amount of rescue analgesia administered or PaCO₂ between treatment groups. No dogs demonstrated respiratory depression or profound motor dysfunction at any time point during the study. 9/16 (56%) dogs did not require rescue analgesia during the first 18 hours following splenectomy.Conclusions and clinical relevanceThe combination of low dose bupivacaine (0.25 mg kg^?1) and morphine (0.1 mg kg^?1) when administered epidurally has little effect on post-operative motor function. This combination can be used without concern of motor paralysis in healthy animals.     

Characterisation of tramadol,morphine and tapentadol in an acute pain model in Beagle dogs

ObjectiveTo evaluate the analgesic potential of the centrally acting analgesics tramadol, morphine and the novel analgesic tapentadol in a pre-clinical research model of acute nociceptive pain, the tail-flick model in dogs.Study designProspective part-randomized pre-clinical research trial.AnimalsFifteen male Beagle dogs (HsdCpb:DOBE), aged 12–15 months.MethodsOn different occasions separated by at least 1 week, dogs received intravenous (IV) administrations of tramadol (6.81, 10.0 mg kg^?1), tapentadol (2.15, 4.64, 6.81 mg kg^?1) or morphine (0.464, 0.681, 1.0 mg kg^?1) with subsequent measurement of tail withdrawal latencies from a thermal stimulus (for each treatment n = 5). Blood samples were collected immediately after the pharmacodynamic measurements of tramadol to determine pharmacokinetics and the active metabolite O-demethyltramadol (M1).ResultsTapentadol and morphine induced dose-dependent antinociception with ED50-values of 4.3 mg kg^?1 and 0.71 mg kg^?1, respectively. In contrast, tramadol did not induce antinociception at any dose tested. Measurements of the serum levels of tramadol and the M1 metabolite revealed only marginal amounts of the M1 metabolite, which explains the absence of the antinociptive effect of tramadol in this experimental pain model in dogs.Conclusions and clinical relevanceDifferent breeds of dogs might not or only poorly respond to treatment with tramadol due to low metabolism of the drug. Tapentadol and morphine which act directly on μ-opioid receptors without the need for metabolic activation are demonstrated to induce potent antinociception in the experimental model used and should also provide a reliable pain management in the clinical situation. The non-opioid mechanisms of tramadol do not provide antinociception in this experimental setting. This contrasts to many clinical situations described in the literature, where tramadol appears to provide useful analgesia in dogs for post-operative pain relief and in more chronically pain states.     

Impact of surgical preparatory rinses with isopropyl alcohol or water on perioperative body temperature in pediatric female dogs and cats

ObjectiveTo describe the effects of presurgical preparation with an isopropyl alcohol or water rinse on the perioperative rectal temperature (RT) of puppies and kittens.Study designRandomized clinical trial.AnimalsA total of 48 intact female mixed breed puppies and 43 intact female Domestic Short Hair kittens aged 8–18 weeks.MethodsAll animals were premedicated with intramuscular buprenorphine (0.02 mg kg^–1) and acepromazine (0.05 mg kg^–1). Anesthesia was induced with intravenous propofol (4 mg kg^–1 to effect) for puppies or ketamine (5 mg kg^–1) and midazolam (0.25 mg kg^–1) for kittens. RT was measured every minute for the first 15 minutes at the beginning of hair/fur removal, then every 5 minutes for 45 minutes (dogs) and 35 minutes (cats). All animals were prepared for surgery using a 1.6% chlorhexidine solution, then rinsed with either isopropyl alcohol (group CA) or water (group CW).ResultsMean RT difference between the groups was not significant at any time point. The mean RT at 45 minutes for dogs was 35.9 °C and 36.0 °C in groups CA and CW, respectively (p = 0.74). The mean RT at 35 minutes for cats was 35.1 °C in both groups (p = 0.84).Conclusions and clinical relevanceThe use of either water or alcohol as a rinsing agent results in the same degree of perioperative temperature change. Other factors that contribute to perioperative hypothermia should be considered when choosing between these rinsing agents in surgical preparation of pediatric and small animals.     

Use of a pulsed electromagnetic field for treatment of post-operative pain in dogs: a pilot study

Objective To determine if pulsed electromagnetic field (PEMF) therapy reduces post‐operative pain in dogs following ovariohysterectomy, and to evaluate PEMF interaction with post‐operative morphine analgesia. Study design Randomized controlled clinical trail. Animals Sixteen healthy dogs weighing 18 (10–32) kg [median (range)] and aged 13 (3–36) months. Materials and methods Anesthesia consisted of atropine (0.04 mg kg^?1, SC), acepromazine (0.02 mg kg^?1, SC), fentanyl (0.01 mg kg^?1, SC), thiopental (10–15 mg kg^?1, IV) and halothane in oxygen. Ovariohysterectomies were performed by senior veterinary students. Pain score (numeric rating scale, 0–28), pulse rate, respiratory rate, indirect mean arterial pressure (MAP), and body temperature were evaluated prior to anesthetic premedication, at extubation, 30 minutes after extubation, and then hourly for 6 hours. Following extubation, dogs were randomly divided into four groups: a control group that received 0.9% NaCl, IV, and no PEMF; a magnet group that received 0.9% NaCl, IV, and PEMF; a morphine group that received morphine 0.25 mg kg^?1, IV, and no PEMF; and, a magnet/morphine group that received morphine 0.25 mg kg^?1, IV, and PEMF. A single observer, blinded to treatment, obtained all behavioral observations and physiologic data. Data were analyzed using the Kruskal–Wallis statistical test with a significance of p < 0.05. Results Significant differences in MAP (mm Hg) [median (range)] occurred at 300 minutes [morphine 108 (83–114) and magnet/morphine 90 (83–97) < magnet 135 (113–117)], and at 360 minutes [magnet/morphine 93 (81–100) < control 127 (111–129) and magnet 126 (111–129)]. At 30 minutes the total pain score for the magnet/morphine group [1.5 (0–5)] was significantly less than control [8 (6–13)], but not different from magnet [5.5 (4–7)] or morphine [4.5 (2–9)]. Conclusions and clinical relevance Although no clear benefit was seen in this study, the results suggest that PEMF may augment morphine analgesia following ovariohysterectomy in dogs, and that further study of the analgesic effects of PEMF is warranted.     

The effects of medetomidine on the action of vecuronium in dogs anaesthetized with halothane and nitrous oxide

ObjectiveTo quantify the effects of medetomidine on the onset and duration of vecuronium-induced neuromuscular blockade in dogs.Study designRandomized, prospective clinical study.AnimalsTwenty-four, healthy, client-owned dogs of different breeds, aged between 6 months and 10 years and weighing between 5.0 and 40.0 kg undergoing elective surgery.MethodsDogs were randomly allocated to two groups. Pre-anaesthetic medication in group M+ was intramuscular acepromazine (ACP) 25 μg kg⁻¹, morphine 0.5 mg kg⁻¹ and medetomidine 5 μg kg⁻¹. Group M− received ACP and morphine only, at the same dose rate. After induction with thiopental, anaesthesia was maintained with halothane in oxygen and nitrous oxide. End-tidal halothane concentration was maintained at 1.1%. Neuromuscular blockade was produced with intravenous vecuronium (50 μg kg⁻¹) and monitored using a train of four stimulus applied at the ulnar nerve. The times taken for loss and reappearance of the four evoked responses (twitches [T]) were recorded. Normal and nonparametric data were analysed with an independent t-test and Mann-Whitney's U-test, respectively.ResultsThe fourth twitch (T4) disappeared at similar times in each group: 107 ± 19; [72–132] (mean ± SD; [range]) seconds in M+ and 98 ± 17 [72–120] seconds in M− dogs. The first twitch (T1) was lost at 116 ± 15; [96–132] seconds in group M+ and 109 ± 19; [72–132] seconds in M−. The fourth twitch returned significantly earlier in M+ dogs: 20.8 ± 3.8 [14–28] minutes compared with 23.8 ± 2.7 [20–27] minutes (p = 0.032). The duration of drug effect (T4 absent) was significantly shorter (p = 0.027) in M+ (18.9 ± 3.7 minutes) compared with M− dogs (22.2 ± 2.9 minutes). The recovery rate (interval between reappearance of T1 and T4) was significantly more rapid (p = 0.0003) in medetomidine recipients (3.0 ± 1.2 versus 5.2 ± 1.3 minutes).Conclusion and clinical relevance Medetomidine 5 μg kg⁻¹ as pre-anaesthetic medication shortened the duration of effect of vecuronium in halothane-anaesthetized dogs and accelerated recovery, but did not affect the onset time. These changes are of limited clinical significance.     

Glomerular filtration rate after tramadol, parecoxib and pindolol following anaesthesia and analgesia in comparison with morphine in dogs

ObjectiveTo compare the effects of morphine, parecoxib, tramadol and a combination of parecoxib, tramadol and pindolol on nociceptive thresholds in awake animals and their effect on glomerular filtration rate (GFR) in dogs subjected to 30 minutes of anesthesia.AnimalsEight adult mixed breed experimental dogs.Study designRandomized, controlled trial.MethodsDogs received 0.05 mg kg^?1 acepromazine subcutaneously (SC) as anaesthetic pre-medication. Thirty to sixty minutes later, they received either tramadol 3 mg kg^?1 intravenously, (IV), parecoxib (1 mg kg^?1 IV), a combination of tramadol 3 mg kg^?1 (IV), parecoxib 1 mg kg^?1 (IV) and pindolol 5 μg kg^?1 (SC), morphine (0.1 mg kg^?1 (IV) or 0.9% saline (2 mL). Anaesthesia was then induced with IV propofol to effect (2.9 ± 0.8 mg kg^?1) and maintained with halothane in oxygen for 30 minutes. Systolic arterial blood pressure was maintained above 90 mmHg with IV fluids and by adjusting the inspired halothane concentration. Post-treatment nociceptive thresholds to mechanical stimuli, expressed as percent of pre-treatment values, were compared between the treatments to assess the analgesic efficacy of the drugs. Plasma iohexol clearance (ICL), a measure of GFR, was estimated both before and 24 hours after induction of anaesthesia to study the drugs’ effects on renal perfusion. Nociceptive threshold and GFR data were compared using mixed model analysis in sas^®9.1.ResultsBoth tramadol and parecoxib produced similar analgesia, which was less than that of morphine. Their combination with pindolol produced analgesia comparable with morphine. None of the test drugs, either alone or in combination, reduced GFR.ConclusionTramadol and parecoxib (either alone or in combination) can increase nociceptive thresholds in awake dogs and have minimal effects on renal perfusion in normotensive dogs subjected to anaesthesia.     

Effects of tramadol alone,in combination with meloxicam or dipyrone,on postoperative pain and the analgesic requirement in dogs undergoing unilateral mastectomy with or without ovariohysterectomy

ObjectiveTo compare the effects of tramadol alone, or in combination with dipyrone or meloxicam, on postoperative pain and analgesia requirement after unilateral mastectomy with or without ovariohysterectomy in dogs.Study designProspective, randomized, clinical study.AnimalsTwenty seven bitches undergoing unilateral mastectomy with or without ovariohysterectomy.MethodsAnesthesia was induced with propofol and maintained with isoflurane and a constant rate infusion of morphine. Before the end of surgery, dogs were randomly assigned to receive intravenous tramadol alone (3 mg kg^?1, group T), combined with dipyrone (30 mg kg^?1, group TD) or meloxicam (0.2 mg kg^?1, group TM). Dogs received additional doses of tramadol (groups T and TM) or tramadol with dipyrone (group TD) at 8 and 16 hours after extubation. Postoperative pain was assessed by a blinded observer before anesthesia (baseline) and at 1, 2, 3, 4, 6, 8, 12, 16 and 24 hours after extubation using a visual analog scale (VAS) and a modified Glasgow scale. Rescue analgesia (morphine, 0.5 mg kg^?1) was administered if the Glasgow pain score was >3.5.ResultsThere were no significant differences among groups in pain scores evaluated by the VAS or the Glasgow scale. In groups T, TD and TM, pain scores were significantly higher than at baseline for 6, 8 and 2 hours, respectively. Rescue analgesia was administered to 3/9, 2/9 and 1/9 dogs in groups T, TD and TM, respectively (p > 0.05) [Correction added on 15 August 2013, after first online publication: ‘T, TM and TD’ was changed to ‘T, TD and TM’.].Conclusions and clinical relevanceUnder the conditions of this study, tramadol alone or in combination with dypyrone or meloxicam provided effective analgesia for 24 hours in most dogs after unilateral mastectomy with or without ovariohysterectomy. Further evaluation of combination therapies is needed in larger groups of dogs.     

Pharmacokinetics and analgesic efficacy of intranasal administration of tramadol in dogs after ovariohysterectomy

ObjectiveTo assess analgesic efficacy and the pharmacokinetics of intranasal (IN) tramadol in dogs following ovariohysterectomy.Study designRandomized, blinded clinical study.AnimalsA total of 30 bitches undergoing elective ovariohysterectomy.MethodsDogs were randomly assigned to one of three experimental groups (10 dogs per group): IN tramadol 4 mg kg^–1 (group T-IN), intravenous (IV) tramadol 4 mg kg^–1 (group T-IV) and IV methadone 0.2 mg kg^–1 (group M). Drugs were administered at extubation. At established time points (before surgery and up to 8 hours after drug administration) analgesia was assessed using the Italian version of the Glasgow Composite Measure Pain Scale Short Form and physiological variables were recorded. To determine the pharmacokinetics of IN tramadol, blood samples were collected at predetermined time points. Shapiro–Wilk test was used to assess whether data were normally distributed and consequently parametric or non parametric tests were applied. A p value < 0.05 was considered significant.ResultsNo significant intergroup differences were observed in the dogs that were administered rescue analgesia and time of its administration. Excluding dogs that were administered rescue analgesia, no significant intergroup differences emerged in pain scores and physiological variables, except for a lower rectal temperature in group M compared with the tramadol groups. After IN administration, tramadol was rapidly absorbed into the systemic circulation, reaching its maximum concentration (range 74.74–200.29 ng mL^–1) within 30–60 minutes, it then decreased rapidly and was detectable in plasma for up to 2 hours after treatment in all dogs.Conclusions and clinical relevanceIN tramadol administration appears to be as effective as IV tramadol and methadone treatments in pain management of dogs after elective ovariohysterectomy. Given its low concentrations and short detection time in plasma after the IN route, systemic tramadol action appears unlikely.     

Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain‐free female cats

ObjectiveTo assess the potential of a thermal carbon dioxide (CO₂) laser to explore antinociception in pain-free cats.Study designExperimental, prospective, blinded, randomized study.AnimalsSixty healthy adult female cats with a (mean ± standard deviation) weight of 3.3 ± 0.6 kg.MethodsCats were systematically allocated to one of six treatments: saline 0.2 mL per cat; morphine 0.5 mg kg⁻¹; buprenorphine 20 μg kg⁻¹; medetomidine 2 μg kg⁻¹; tramadol 2 mg kg⁻¹, and ketoprofen 2 mg kg⁻¹. Latency to respond to thermal stimulation was assessed at baseline and at intervals of 15–30, 30–45, 45–60, 60–75, 90–105 and 120–135 minutes. Thermal thresholds were assessed using time to respond behaviourally to stimulation with a 500 mW CO₂ laser. Within-treatment differences in response latency were assessed using Friedman’s test. Differences amongst treatments were assessed using independent Kruskal–Wallis tests. Where significant effects were identified, pairwise comparisons were conducted to elucidate the direction of the effect.ResultsCats treated with morphine (X² = 12.90, df = 6, p = 0.045) and tramadol (X² = 20.28, df = 6, p = 0.002) showed significant increases in latency to respond. However, subsequent pairwise comparisons indicated that differences in latencies at specific time-points were significant (p < 0.05) only for tramadol at 60–75 and 90–105 minutes after administration (21.9 and 43.6 seconds, respectively) in comparison with baseline (11.0 seconds). No significant pairwise comparisons were found within the morphine treatment. Injections of saline, ketoprofen, medetomidine or buprenorphine showed no significant effect on latency to respond.Conclusions and clinical relevanceThe CO₂ laser technique may have utility in the assessment of thermal nociceptive thresholds in pain-free cats after analgesic administration and may provide a simpler alternative to existing systems. Further exploration is required to examine its sensitivity and comparative utility.