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.     

Retrospective comparison of three locoregional techniques for pelvic limb surgery in dogs

ObjectiveTo retrospectively compare the efficacy and duration of effect of three commonly used locoregional blocks in dogs undergoing pelvic limb orthopaedic surgery.Study designRetrospective clinical study.AnimalsA total of 236 dogs that underwent pelvic limb surgery and were administered a locoregional technique.MethodsA total of 236 hospital records were reviewed and 230 included in statistical analysis. Dogs were grouped as following: electrostimulation-guided pre-iliac femoral and sciatic nerve block (group PFS, n = 70); ultrasound-guided saphenous and sciatic nerve block (group SS, n = 76); or lumbosacral epidural (group EPI, n = 84). In group EPI, bupivacaine 0.5% or ropivacaine 0.75% was used with morphine. Dogs were pain scored (short form of the Glasgow Composite Measure Pain Scale) hourly following recovery from anaesthesia. Analysed data included: time to first postoperative dose of methadone, pain score at that time, intraoperative rescue analgesia, intraoperative hypotension and ability to walk and urinate overnight. Separate analyses were performed including all pelvic limb surgeries and including only elective stifle surgeries. Kruskal–Wallis and Mann–Whitney tests were performed. A p value < 0.05 was considered significant. The median (range) is reported.ResultsFor all pelvic limb surgeries, the time to first postoperative methadone was 530 (110–1337), 440 (140–1030) and 466 (135–1094) minutes in groups EPI, PFS and SS, respectively, and was not significantly different. Postoperatively, 10/84, 15/70 and 12/76 dogs in groups EPI, PFS and SS, respectively, did not require methadone (nonsignificant). Significantly fewer dogs in group EPI (18%) required intraoperative rescue analgesia compared with group SS (38%), but not compared with PFS (30%). Significantly more dogs in group EPI had hypotension intraoperatively (30%) and urinary retention postoperatively (62%).Conclusions and clinical relevanceIntraoperative analgesia may be superior with EPI than SS for some surgeries of the pelvic limb, but not for stifle surgeries. All three techniques provided similar requirement for postoperative analgesia, but EPI caused higher incidence of intraoperative hypotension and postopertive urinary retention.     

Efficacy and side effects of intraoperative analgesia with intrathecal bupivacaine and levobupivacaine: a retrospective study in 82 dogs

ObjectiveTo evaluate spinal (intrathecal) anaesthesia (SA) in addition to general anaesthesia in dogs, and report the incidence of side effects and cardiovascular response (CR) to surgery.Study designRetrospective clinical study.AnimalsOne hundred and fifteen dogs undergoing general anaesthesia for surgery caudal to the diaphragm between 2005 and 2008.MethodsRecords of anaesthetized dogs that had received SA with bupivacaine or levobupivacaine 0.5%, together with morphine or fentanyl were reviewed. Success rate of SA, complication rate and incidence of CR were recorded and examined in relation to the dose of local anaesthetic administered and the type of surgery. Univariate and Cusum analysis were performed to identify independent predictors of response to surgical stimulation and characterize the learning curve for the technique, respectively.ResultsEighty-two dogs received successful SA. The Cusum plot suggested that a failure rate of 10% is achieved when the procedure is performed more than 66 times. Median local anaesthetic dose related to weight was 0.40 mg kg^?1 (0.3–0.5), and to spinal cord length 0.1 mg cm^?1 (0.07–0.12). Morphine was added to the local anaesthetic in 56 and fentanyl in 22 dogs. CR post-stimulus occurred in 29 cases: 11 of 22 ovariohysterectomies, 14 of 33 hindlimb-surgeries, 2 of 10 caudal-abdominal-surgeries and 2 of 17 Caesarean sections. Anaesthetic dose related to weight was not a predictor of CR. Bradycardia occurred in seven, hypotension in 24, urinary retention in four and hypersalivation in 6 of 82 dogs.ConclusionsSA was practicable to apply, but in this study did not totally block CR, Side effects were minimal, with an incidence similar to that in humans.Clinical relevanceSA can be used in clinical cases with few side effects although monitoring of and ensuing treatment of hypotension is required. Comparative prospective studies are required to establish efficacy and a reliable dose.     

Bupivacaine 0.25% and methylene blue spread with epidural anesthesia in dog

ObjectiveTo evaluate the extent sensory and motor blocks produced by the epidural injection of different volumes of 0.25% bupivacaine (Bu) with methylene blue (MB), in dogs.Study designProspective experimental trial.AnimalsTwenty healthy adult mongrel dogs, weighing 9.9 ± 1.9 kg.MethodsDogs were randomly allocated into one of four groups that received 0.2, 0.4, 0.6 or 0.8 mL kg^?1 of an epidural solution containing 0.25% Bu and MB. Sensory block was evaluated against time by pinching the tail, hind limb interdigital web, toenail bases and the skin over the vertebral dermatomes. Motor block was assessed by ataxia, hind limb weight-bearing ability and by loss of muscle tone of the tail and pelvic limbs. Data were collected at 2, 5, 10, 15 and 30 minutes after the end of epidural injection. After the final time point, dogs were euthanatized and laminectomies were conducted to expose the extent of the dural dye staining.ResultsThe volumes 0.2, 0.4, 0.6 and 0.8 mL kg^?1 of 0.25% Bu and MB blocked a mean of 5, 14.2, 20.2 and 21 dermatomes, respectively. The extent of the senory block increased up to a volume of 0.6 mL kg^?1. Motor block was longer-lasting and more intense than sensory block. Complete dyeing of the spinal cord with MB was achieved in some dogs at 0.4 mL kg^?1 and all dogs at 0.6 mL kg^?1.ConclusionsThe volume of anesthetic injected into the epidural space plays an important role in the quality of the epidural anesthesia. At 0.25%, bupivacaine provided an efficient sensory block at 0.6 mL kg^?1.Clinical relevanceRelatively high volumes (0.6 mL kg^?1) of 0.25%, BU and MB were needed to produce an effective sensory and motor block caudal to the umbilicus, but all spinal cord segments were reached by MB at this dose.     

Hypobaric intrathecal anaesthesia for partial hemipelvectomy in a dog.

OBJECTIVE : To report the intrathecal use of a hypobaric anaesthetic solution for partial hemipelvectomy in a nine-year-old, neutered female, Golden Retriever dog, weighing 34 kg. METHODS : Under inhalational anaesthesia, with the dog lying in lateral recumbency and the surgical side uppermost, 1.9 ml of a hypobaric solution containing 3.42 mg of bupivacaine and 0.66 mg of morphine were administered in the subarachnoid space at L5-6 level 30 minutes before surgery. Following the intrathecal injection the dog was maintained for five minutes in a 10 degrees head-down position, then for three minutes in a 10 degrees head-up position. RESULTS : Apart from a transient increase in heart and respiratory rates during resection of the sartorius muscle, which was treated with a plasma Target Controlled Infusion (TCI) of fentanyl, spinal anaesthesia provided cardiovascular stability and excellent relaxation of the surgical site. Neither motor blockade nor proprioceptive deficit were apparent in the contra-lateral hind limb at recovery, 200 minutes after injection. Postoperatively, rescue analgesia was not required in the 48 hours following surgery. CLINICAL SIGNIFICANCE : In dogs, the use of intrathecal hypobaric bupivacaine and morphine as a part of a balanced anaesthetic protocol should be considered during unilateral major orthopaedic surgeries of the pelvis and hind limb, as it allowed a reduction in the dose administered compared to isobaric solutions, providing selective spinal anaesthesia, excellent long-lasting analgesia, and rapid recovery of ambulation.     

A comparison of epidural analgesia provided by bupivacaine alone,bupivacaine + morphine,or bupivacaine + dexmedetomidine for pelvic orthopedic surgery in dogs

ObjectiveTo compare the analgesic efficacy of bupivacaine, bupivacaine + morphine, or bupivacaine + dexmedetomidine administered epidurally in dogs undergoing pelvic limb orthopedic surgery.Study designProspective, randomized, double blinded clinical trial.AnimalsSixty dogs weighing (mean ± SD) 35 ± 15.7 kg, aged 5 ± 3 years.MethodsDogs were assigned to receive a lumbosacral epidural containing bupivacaine (B) 0.5%, 1 mg kg^?1; B, bupivacaine 0.5%, 1 mg kg^?1 + morphine 1%, 0.1 mg kg^?1; B + M, or bupivacaine 0.5%, 1 mg kg^?1 + dexmedetomidine 0.05%, 4 μg kg^?1; B + D. The anesthetic protocol was standardized. The median expired isoflurane concentration (E′Iso) and requirement for additional induction agent preventing purposeful movement were recorded. Pain was scored using visual analog (VAS) and modified University of Melbourne (UMPS) pain scales. Sedation was assessed using a 0–4 scale. All parameters were recorded preoperatively, and at extubation (t = 0), then at 1, 2, 4, 8, 12, 16, and 20–24 hours. Hydromorphone was administered postoperatively to patients with a VAS ≥ 35 and/or UMPS ≥ 9. Time to first voluntary urination and first motor activity were recorded.ResultsPostoperatively, B + D had a lower UMPS pain score than B at t = 1 hour (p = 0.013), but not compared to B + M. The B + D group had a shorter time to urination (p = 0.0131) and a longer time for return of motor function (p = 0.0068). There were no other differences between the treatments.Conclusion and clinical relevanceEpidurally administered B, B + M, or B + D in dogs all provided acceptable analgesia to manage post–operative orthopedic pelvic limb pain. Epidural administration of B + D is an effective alternative to the analgesia provided by B or B + M, but is associated with increased time to return of motor function. The direct neurotoxic effects of epidural dexmedetomidine have not been fully tested.     

Results of preemptive epidural administration of morphine with or without bupivacaine in dogs and cats undergoing surgery: 265 cases (1997-1999)

OBJECTIVE: To determine prevalence of adverse effects associated with epidural administration of morphine with or without bupivacaine in dogs and cats undergoing surgery and evaluate effects of epidural administration of morphine on postoperative pain severity. DESIGN: Retrospective study. ANIMALS: 242 dogs and 23 cats. PROCEDURE: Morphine with or without bupivacaine was administered prior to surgery with a Tuohy needle, spinal needle, or epidural catheter. In 18 dogs that underwent surgery twice, results of preemptive epidural administration of morphine with or without bupivacaine were compared with results of systemic administration of oxymorphone and ketoprofen. RESULTS: The delivered fraction of isoflurane was significantly lower in animals given morphine and bupivacaine than in animals given morphine alone. Analgesia was of significantly longer duration in dogs given morphine and bupivacaine than in dogs given morphine alone. During anesthesia, mild respiratory and cardiovascular depression was reported. Seven dogs and 2 cats had urine retention, and 2 dogs developed pruritus. Six dogs vomited when a second dose of morphine was given epidurally the day after surgery. Eight of 72 dogs had delayed hair growth. In 18 dogs that underwent surgery twice, the delivered fraction of isoflurane was significantly lower and the duration of analgesia was significantly longer when morphine with or without bupivacaine was given epidurally than when oxymorphone and ketoprofen were given. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that preemptive epidural administration of morphine with or without bupivacaine is a safe and effective method of inducing long-lasting analgesia in dogs and cats and is superior to standard management of postoperative pain with repeated injection of oxymorphone and ketoprofen.     

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.     

Epidural anesthesia in dogs undergoing hindlimb orthopedic surgery: effects of two injection sites

This prospective clinical trial evaluated the effects of epidural anesthesia (EA) placed at the lumbosacral compared to the L5–L6 junction in dogs undergoing hindlimb orthopedic surgery. In all, 98 dogs were randomly assigned to receive injection at either L7–S1 (LS group) or L5–L6 (LL group) at the same local anesthetic regimen (1 mg/kg bupivacaine 0.5% and 0.1 mg/kg morphine 1%). Fentanyl (1 µg/kg) was the intraoperative rescue analgesia (iRA) administered if mean arterial pressure increased by 30% above pre-stimulation value. Procedural failure, iRA, hypotension, motor block resolution, and postoperative side effects were recorded. There were 7/47 (15%) epidural procedural failures in the LS group and 8/51 (16%) (P=1.00) in the LL group; iRA was administered in 21/40 (52%) LS group dogs and in 13/43 (30%) LL group dogs, respectively (P=0.047). The incidence of hypotension was 10/40 (25%) and 16/43 (37%) in the LS group and the LL group, respectively (P=0.25). Proprioceptive residual deficit at 8 hr after EA was recorded in 3/26 (12%) in group LS dogs and in 13/26 (50%) group LL dogs, respectively (P=0.01). The proprioceptive residual deficit at 24 hr in one dog (LL group) resolved within 36 hr. No episodes of postoperative urinary retention, pruritus or neurological damage were recorded. The L5–L6 EA decreased significantly iRA but delays the proprioceptive recovery time. Further studies are needed to determine whether a lower bupivacaine dose reduces the duration of the residual block retaining the same incidence of iRA.     

Clinical evaluation of the anaesthetic sparing effect of brachial plexus block in cats

ObjectiveTo evaluate the isoflurane sparing effect and the post-surgical analgesia provided by a brachial plexus block (BPB) in cats undergoing distal thoracic limb surgery.Study designProspective randomized blinded clinical study.AnimalsTwenty client-owned cats.MethodsCats were assigned to receive either no BPB (group NB) or a nerve stimulator guided BPB (group BPB) using lidocaine (3.6 mg kg^?1) and bupivacaine (1.2 mg kg^?1). Pre-medication consisted of midazolam and ketamine intravenously (IV). Anaesthesia was induced with propofol IV to effect and maintained with isoflurane delivered in oxygen and a continuous rate infusion of fentanyl (2 μg kg^?1 hour^?1). End-tidal isoflurane concentration (Fe′ISO) was adjusted every 3 minutes guided by changes in cardiorespiratory parameters and reflexes present, to maintain a stable depth of anaesthesia. Five time points were chosen to record all parameters and compare values between groups. Recovery and post-operative pain assessment were performed using a visual analogue scale (VAS) at 15 and 45 minutes after extubation and thereafter at hourly intervals until 5 hours after placement of the BPB.ResultsNo clinically significant differences were seen for heart rate, respiratory rate and non-invasive blood pressure between groups. Mean Fe′ISO was significantly lower in group BPB compared with group NB at all time points. In group NB, all intraoperative measurements of Fe′ISO were significantly higher compared with baseline (3 minutes before start of surgery) measurements. During recovery, VAS scores for group BPB were significantly lower than for group NB. Additional analgesics were needed in all cats within the study period.Conclusion and Clinical relevanceIn cats undergoing orthopaedic surgery of the thoracic limb, BPB reduced intra-operative isoflurane requirement and pain during the early post-operative period when compared with procedures without a BPB. BPB is a useful adjunct to anaesthesia in such cases.     

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.     

Comparison of clinical effects of epidural levobupivacaine morphine versus bupivacaine morphine in dogs undergoing elective pelvic limb surgery

Objective

To evaluate the efficacy, in terms of the amount of rescue analgesia required, and the clinical usefulness of epidural injection of morphine with bupivacaine or levobupivacaine for elective pelvic limb surgery in dogs during a 24-hour perioperative period.

Opioid requirements after locoregional anaesthesia in dogs undergoing tibial plateau levelling osteotomy: a pilot study

ObjectiveTo determine the intraoperative and early postoperative opioid requirement after ultrasound-guided sciatic and/or femoral nerve block or epidural anaesthesia in dogs undergoing tibial plateau levelling osteotomy (TPLO).Study designProspective, masked, pilot, randomized, clinical trial.AnimalsA total of 40 client-owned dogs undergoing TPLO.MethodsEach dog was randomly assigned to group SF (combined sciatic and femoral nerve block), group S (sciatic nerve block), group F (femoral nerve block) or group E (epidural anaesthesia). A total of 0.3 mL kg^–1 of ropivacaine 0.5% was administered to each nerve or in the epidural space. Intraoperatively, fentanyl (2 μg kg^–1) was administered intravenously when heart rate, mean arterial pressure or respiratory rate increased by >30% compared with baseline values. Postoperatively, a visual analogue scale (VAS) and a modified German version of the French pain scale (4AVet) were used to assess pain every 30 minutes for 150 minutes and again once the morning after surgery. Methadone (0.1 mg kg^–1) was administered intravenously if the VAS was ≥ 4 cm [maximal value 10 cm; median (interquartile range)] or the composite pain score was ≥5 [maximal value 15; median (interquartile range)]. Significance was defined as p ≤ 0.05.ResultsGroups SF and E required less total intraoperative and early postoperative opioid doses compared with groups S and F (p = 0.031). No dogs in group SF had a block failure or required postoperative methadone. A reduced methadone requirement was found in group SF compared with all the other groups up to 150 minutes after recovery (p = 0.041).Conclusions and clinical relevanceCombined sciatic and femoral nerve block and epidural anaesthesia lead to less cumulative consumption of perioperative opioids than single nerve blockade. Sciatic or femoral nerve block alone might be insufficient to control nociception and early postoperative pain in dogs undergoing TPLO.     

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.     

Retrospective clinical evaluation of ultrasound guided transverse abdominis plane block in dogs undergoing mastectomy

HistoryEleven female dogs of different breeds undergoing unilateral radical (n = 7) or regional abdominal mastectomy (n = 4) received an ultrasound guided transverse abdominis plane block (TAP-block).Physical examinationSubjects showed single or multiple mammary tumours. Serum biochemistry, CBC and electrocardiogram were unremarkable. Eight animals were classified as ASA physical status II and 3 as ASA III.ManagementDogs were premedicated with methadone [0.1 or 0.2 mg kg^?1 intravenously (IV) or intramuscularly respectively] or fentanyl (2.5 μgkg^?1 IV). Anaesthesia was induced with propofol and maintained with isoflurane or sevoflurane. Unilateral ultrasound guided TAP blocks were performed in the caudal and cranial abdomen with bupivacaine 0.25% (0.3 to 0.35 mL kg^?1). Intercostal nerve blocks (T₄ to T₁₁) with bupivacaine 0.25% (0.013 to 0.04 mL kg^?1) completed the blocked area in dogs undergoing radical mastectomy.Follow upThe median (range) of end-expired isoflurane and sevoflurane necessary to maintain anaesthesia was 1.15 (1.07–1.22) and 2.07 (2.05–2.2) vol% respectively. A single administration of fentanyl (2.5 μg kg^?1, IV) was administered to control nociception (defined as an increased heart rate or mean arterial blood pressure above 20% of the pre-incisional value) in four of 11 dogs. All dogs received carprofen (2 mg kg^?1 subcutaneously) at the end of surgery. Post-operative pain, assessed for 120 minutes using the short form of Glasgow Composite Pain Scale (0–24), was always lower than 3. No rescue analgesia (allowed by the protocol) was required in this time.ConclusionTransverse abdominis plane block combined with intercostal nerve blocks may be useful to produce intraoperative anti-nociception and short term post-operative analgesia in dogs undergoing unilateral mastectomy.     

Effects of tramadol,morphine or their combination in dogs undergoing ovariohysterectomy on peri-operative electroencephalographic responses and post-operative pain

Abstract

AIM: To compare the peri-operative electroencephalogram (EEG) responses and post-operative analgesic efficacy of pre-operative morphine or tramadol with a combination of low-dose pre-operative morphine and post-operative tramadol, in dogs undergoing ovariohysterectomy.

METHODS: Dogs undergoing routine ovariohysterectomy were treated with either pre-operative morphine (0.5 mg/kg S/C, n=8), or tramadol (3 mg/kg S/C, n=8), or pre-operative low-dose morphine (0.1 mg/kg S/C) and post-operative tramadol (3 mg/kg I/V, n=8). All dogs received routine pre-anaesthetic medication, and anaesthesia was induced with I/V thiopentone to effect and maintained with halothane in oxygen. Respiratory rate, heart rate, end-tidal halothane tension (EtHal) and end-tidal CO₂ tension (EtCO₂) were monitored throughout surgery. The EEG was recorded continuously in a three electrode montage. Median frequency (F50), total power (Ptot) and 95% spectral edge frequency (F95) of the EEG power spectra were compared during different 100-second periods of surgery: prior to and during skin incision, ligation of each ovarian pedicle, ligation of uterine body and skin closure. Post-operatively, pain was assessed using the short form of the Glasgow composite measure pain scale (CMPS-SF).

RESULTS: There was no difference in F50 or Ptot of the EEG between baseline and noxious surgical events within each treatment group, or between the three groups (p>0.05). The mean F95 was higher during the first three periods of surgery for dogs administered tramadol and low-dose morphine than those that received 0.5 mg/kg morphine (p=0.001). Dogs that received low-dose morphine and tramadol had lower CMPS-SF pain scores after ovariohysterectomy than those that received either tramadol or morphine alone (p=0.001). There was no difference in pain scores between dogs in the latter two groups.

CONCLUSION AND CLINICAL RELEVANCE: Tramadol and morphine administered pre-operatively provided an equal degree of post-operative analgesia in dogs after ovariohysterectomy. A combination of pre-operative low-dose morphine and post-operative tramadol produced better post-operative analgesia than either drug administered alone pre-operatively. Administration of analgesics pre- and post-operatively could result in improved post-operative well-being of ovariohysterectomised dogs.     

Combined paravertebral plexus block and parasacral sciatic block in healthy dogs

ObjectiveTo evaluate the effectiveness of paravertebral lumbar plexus block combined with parasacral sciatic block to anesthetize one hind limb in awake dogs.Study designRandomized, controlled, blinded experimental study.AnimalsEight healthy mongrel dogs weighing 12.4 ± 4.5 kg and aged 7 ± 2.33 years.MethodsAfter sedation with medetomidine, dogs received B1: bupivacaine 0.25%, 0.2 mL kg^?1, B2: bupivacaine 0.5%, 0.2 mL kg^?1, B3: bupivacaine 0.25% 0.4 mL kg^?1, P1: NaCl 0.2 mL kg^?1, P2: NaCl 0.4 mL kg^?1. The lumbosacral plexus was blocked through a paravertebral block of the fourth, fifth and sixth lumbar nerves combined with a parasacral block. The relevant nerves were located using a nerve stimulator and injections of each treatment were administered. Degree and durations of sensory blockade were determined through the response to a Halsted clamp pressure on the skin innervated by the saphenous/femoral and lateral cutaneous femoral nerves (lumbar dermatomes) and by the peroneal and tibial nerves. The degree and duration of motor blockade was assessed evaluating the ability to walk normally and proprioception.ResultsP1 and P2 treatments did not show any grade of sensory or motor blockade. The B2 treatment produced a higher degree of sensory blockade compared to B1 and B3 for both lumbar and sciatic dermatomes. There was no significant difference in the degree of sensory blockade comparing B1 to B3. The B2 treatment had greater motor blockade compared to B1 and B3. The duration of sensory and motor blockade was longer in B2 compared to B1 and B3.Conclusion and clinical relevanceWhen the nerve stimulator is used to perform the lumbosacral plexus block, the concentration of the bupivacaine has a more important role than the volume to produce a more solid and longer block.     

Closed system anaesthesia in dogs using liquid sevoflurane injection; evaluation of the square-root-of-time model and the influence of CO2 absorbent

Objective To determine whether predictable alveolar concentrations of sevoflurane are reliably produced in dogs when liquid sevoflurane is injected into closed circuit breathing systems, as calculated by Lowe's square‐root‐of‐time anaesthetic uptake model, and to confirm the validity of the model using soda lime and calcium hydroxide lime. Study design Prospective clinical study. Animals Eleven healthy dogs with a mean body mass of 34 ± 9 kg scheduled for pelvic limb orthopaedic surgery. Materials and methods Following pre‐anaesthetic medication, anaesthesia was induced with propofol and maintained with sevoflurane in a closed circle system. Epidural anaesthesia was performed with morphine and bupivacaine. Liquid sevoflurane was injected into the circuit by syringe, using dosages and time intervals derived from Lowe's square‐root‐of‐time anaesthetic uptake model. The target alveolar concentration chosen was 1.1 × MAC (2.6% end‐tidal sevoflurane). Either soda lime (group S; n = 6) or calcium hydroxide lime (Amsorb; group A; n = 5) were used for CO₂ absorption. Sevoflurane concentration and the respiratory gas composition were measured with an infrared gas analyser. Results End‐tidal sevoflurane concentrations were close to the predicted value of 2.6% at 9 minutes (2.53 ± 0.1% group S; 2.60 ± 0.26% group A) and 16 minutes (2.55 ± 0.30 group S; 2.52 ± 0.28% group A) but declined thereafter to reach 50% (group S) and 64% (group A) of the predicted value at 121 minutes. There was a constant trend towards higher end‐tidal sevoflurane concentrations in group A but the difference was not statistically significant. Conclusions The square‐root‐of‐time model leads to significantly lower alveolar concentrations than expected, suggesting that the rate of sevoflurane uptake in dogs declines less rapidly than predicted. The use of Amsorb tends to reduce the deviation from predicted concentrations. Clinical relevance The model used in this study provided only an approximate guide to the volume of liquid sevoflurane required. Consequently, the definitive dose schedule must be based on measured anaesthetic concentrations and clinical monitoring.     

Retrospective analysis of complications associated with retrobulbar bupivacaine in dogs undergoing enucleation surgery

ObjectiveTo investigate complications associated with, and without, bupivacaine retrobulbar local anesthesia in dogs undergoing unilateral enucleation surgery.Study designRetrospective, observational study.AnimalsA total of 167 dogs underwent unilateral enucleation surgery via a transpalpebral approach.MethodsRecords from 167 dogs that underwent unilateral enucleation surgery that did (RB) or did not (NB) include retrobulbar bupivacaine anesthesia were reviewed, including anesthetic record, daily physical examination records, surgery report, patient discharge report and patient notes within 14 days of the surgery. Specific complications and severity were compared between RB and NB using the Wilcoxon rank-sum test. A ‘complication burden’ (0–5) comprising five prespecified complications was assigned and tested using rank-sum procedures. Statistical significance was set to 0.05.ResultsGroup RB included 97 dogs and group NB 70 dogs. Dogs in NB had a 17.0 percentage points (points) greater risk for a postoperative recovery complication (38.6% versus 21.6%; 95% confidence interval: 3.0–30.6 points; p = 0.017). There was inconclusive evidence that dogs in group RB had a lower risk of requiring perioperative anticholinergic administration (12.4% versus 22.9%; 10.5 points; p = 0.073). Other complications were similar between groups RB and NB with risks that differed by <10 points. The risk of hemorrhage was similar between groups RB (22.7%) and NB (20.0%) with no significant difference in the level of severity (p = 0.664).Conclusions and clinical relevanceIn this retrospective study, the use of retrobulbar bupivacaine for enucleation surgery in dogs was not associated with an increased risk of major or minor complications.     

Femoral nerve block: a novel psoas compartment lateral pre‐iliac approach in dogs

ObjectiveTo describe a new approach to block the femoral nerve and to evaluate the distribution of a dye injected into the psoas compartment using a new femoral nerve block approach; to assess its clinical application, when combined with a sciatic nerve block, for surgical anaesthesia/analgesia of the pelvic limb in dogs.Study designProspective anatomical, research and clinical study.AnimalsTwo dog cadavers; two dogs that had to be euthanized for reasons unrelated to this study, and 15 dogs undergoing pelvic limb orthopaedic surgery.MethodsPhase 1: anatomical dissections were performed to determine a simple method to approach the femoral nerve within the psoas compartment. Phase 2: 0.1 mL kg^?1 of a lidocaine-new methylene blue solution was injected bilaterally after successful electrolocation of the femoral nerve in two anaesthetized dogs. Colorant spread was evaluated through femoral nerve dissections after euthanasia. Phase 3: in 15 dogs undergoing pelvic limb orthopaedic surgery under light general anaesthesia with isoflurane, intra-operative analgesic effect (cardiovascular responses) and early post-operative pain score, of the novel femoral nerve block combined with a sciatic nerve block as the sole analgesic protocol, were evaluated.ResultsPhase 1: a needle inserted from the lateral aspect of the lumbar muscles, cranially to the iliac crest and with a 30–45° caudo-medial direction, reaches the femoral nerve in the caudal portion of the psoas compartment. Phase 2: Four femoral nerves were stained >2 cm. Phase 3: this novel lateral pre-iliac approach, combined with the sciatic nerve block, blunted the intra-operative cardiovascular response to surgical stimulation in 13 out of 15 anaesthetized dogs. In addition, rescue analgesia was not required in the early post-operative 2-hour period.Conclusion and clinical relevanceThe lateral pre-iliac femoral nerve block technique may provide adequate intra- and early post-operative pain relief in dogs undergoing pelvic limb surgery.