Federico Corletto

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.

Sparing effect of a low dose of intrathecal morphine on fentanyl requirements during spinal surgery: a preliminary clinical investigation in dogs.

OBJECTIVE To evaluate the effect of preoperative intrathecal administration of a low dose of morphine on intraoperative fentanyl requirements in dogs undergoing cervical and thoracolumbar spinal surgery. STUDY DESIGN Prospective randomized clinical study. ANIMALS Dogs (n=18) matched by surgical procedure administered intrathecal morphine (MG) or no-treatment (control group, CG). METHODS After premedication with romifidine (4 microg/kg, intravenously) and induction with propofol, anesthesia was maintained with sevoflurane in oxygen. Intrathecal morphine 0.03 (0.023-0.034) mg/kg was administered at lumbar level 41 (25-65) minutes before surgery in MG. Ketamine (0.5 mg/kg) was administered hourly, starting before incision. Fentanyl infusion (1.2 and 4.2 microg/kg/h in MG and CG, respectively) was administered after a loading dose (5 and 10 microg/kg in MG and CG, respectively), and boluses were given if an increase >20% in heart rate and arterial blood pressure was observed. Total amount of fentanyl administered was recorded, to calculate hourly requirements and predict plasma concentration using a computer simulation. RESULTS Hourly fentanyl consumption and predicted plasma concentrations at the time of response to surgery were significantly lower in MG compared with CG. CONCLUSIONS Preoperative administration of a low dose of intrathecal morphine has a sparing effect on intraoperative fentanyl requirements. CLINICAL RELEVANCE Preoperative intrathecal administration of a low dose of morphine at the lumbar level represented a safe and effective mean of providing intraoperative analgesia in dogs undergoing cervical and thoracolumbar spinal surgery.

Retrospective comparison of two peripheral lumbosacral plexus blocks in dogs undergoing pelvic limb orthopaedic surgery.

OBJECTIVES To compare the lateral pre-iliac approach to the lumbar plexus combined with lumbar paravertebral sciatic nerve block, and the dorsal paravertebral approach to the lumbar plexus combined with sciatic nerve block in dogs. METHODS Retrospective examination of case records of dogs that received the blocks and underwent pelvic limb orthopaedic surgery between 2010 and 2012. Success rate (intraoperative fentanyl consumption <2·1 µg/kg/hour), type and dose of local anaesthetic used, multiple of minimum alveolar concentration of volatile anaesthetic agent administered, incidence of intraoperative hypotension, postoperative methadone administration, postoperative contralateral limb paralysis and neurological complication at 6 weeks re-examination were analysed. RESULTS Ninety-six and 95 records were retrieved in which lateral pre-iliac - lumbar paravertebral sciatic nerve and dorsal paravertebral - sciatic nerve were used, respectively. Success rates were 82·3% in lateral pre-iliac - lumbar paravertebral sciatic nerve and 74·7% in dorsal paravertebral - sciatic nerve groups. Bupivacaine, levobupivacaine and ropivacaine were used. Total local anaesthetic doses, intraoperative hypotension and postoperative methadone administered were similar between groups; minimum alveolar concentration multiple was significantly (P<0·001) lower in lateral pre-iliac - lumbar paravertebral sciatic nerve group. No neurological complications were noted. CLINICAL SIGNIFICANCE Although success rates and perioperative analgesic requirements were not significantly different, the different exposure to anaesthetic agents suggests that the two techniques may not be equivalent.

Effect of three anesthetic induction protocols on laryngeal motion during laryngoscopy in normal cats.

OBJECTIVES To objectively measure and subjectively score the effect of 3 anesthetic induction protocols on arytenoid cartilage motion in normal cats. STUDY DESIGN Randomized prospective clinical study. ANIMALS Cats (n = 35) without previous history of respiratory dysfunction. METHODS Cats were randomly assigned to administration of alfaxalone, propofol, or midazolam and ketamine to induce anesthesia after premedication with methadone. Videolaryngoscopy was performed. Still images at maximum inspiration and expiration were used to measure the area and height of the rima glottidis. Change in rima glottidis area and of normalized glottal gap area (NGGA = area/height(2) ) was calculated. Subjective scores for arytenoid movement were obtained. Kruskal-Wallis test was performed on change of NGGA and rima glottidis area. RESULTS No statistically significant difference was found between groups for age, sex, body weight, and body condition score. Percentage increase of rima glottidis area and change in NGGA were similar for all groups (P = .33 and P = .29). No significant differences were found for subjective scores between groups (P = .54). Arytenoid movement was not detected during videolaryngoscopy and subjective scoring in 3 cats anesthetized with propofol and in 3 cats anesthetized with midazolam and ketamine, despite presence of respiratory movements. CONCLUSIONS No difference in laryngeal motion was observed between the 3 protocols used to induce anesthesia in cats premedicated with methadone.

Retrospective assessment of peripheral nerve block techniques used in cats undergoing hindlimb orthopaedic surgery

Objectives The aim of this study was to assess retrospectively the efficacy and complication rate of hindlimb peripheral nerve blocks (PNBs) in cats. Methods Clinical records of cats that received PNBs and underwent hindlimb orthopaedic surgery from February 2010 to October 2014 were examined. Type of PNB, type and dose of local anaesthetic used, end-expiratory fraction of isoflurane (FE′Iso) administered, additional intraoperative analgesia, incidence of hypotension, postoperative opioid requirement, postoperative contralateral limb paralysis and neurological complications at the 6 week re-examination were investigated. Results Eighty-nine records were retrieved but only 69 were analysed. Four combinations of PNBs were used: 34 lateral preiliac (LPI) approach to lumbar plexus (LP) associated with lumbar paravertebral approach to sciatic nerve (SN); 20 LPI–LP associated with the lateral approach to SN; three LPI–LP associated with gluteal approach to SN; 12 dorsal-paravertebral (DPV) approach to LP associated with lateral SN. Levobupivacaine was used for the majority of PNBs. The mean intraoperative FE′Iso was 1.15%; hypotension was documented in 55.1% of anaesthetics, while 31.8% of cats received fentanyl and/or ketamine intraoperatively. Postoperatively, 72.7% of cats received at least one dose of opioid, while five cats required further postoperative analgesia (ketamine constant rate infusion and/or gabapentin). No cats showed contralateral limb paralysis and neurological complications at the 6 week re-examination. No differences were found when comparing the different PNBs used. Conclusions and relevance PNBs contributed to perioperative anaesthesia/analgesia in cats undergoing hindlimb orthopaedic surgery. However, the clinical relevance of intraoperative hypotension needs further investigation.

Thoracic Epidural Catheter Placement Using a Paramedian Approach with Cephalad Angulation in Three Dogs

Objective To describe a technique for insertion of a thoracic epidural catheter. Study Design Clinical report. Animals Dogs (n = 3) undergoing thoracic wall resection and thoracotomy. Methods A paramedian approach with cephalic angulation was used to place a 24-g epidural catheter in 3 dogs. Dogs 1 and 2 had left caudal thoracic wall resection and dog 3 had left thoracotomy. In dog 1, the epidural catheter was inserted at L2–L3 intervertebral space and the tip of the catheter advanced to the level of T13 vertebral body. In dog 2, the epidural catheter was inserted at T12–T13 intervertebral space and the tip of the catheter was advanced to the level of T8 vertebral body. In dog 3, the epidural catheter was inserted at T13–L1 intervertebral space and its tip advanced until reaching the vertebral body of T10. All dogs were administered a combination of bupivacaine and morphine through the epidural catheter to provide intra- and postoperative analgesia. Results The peridural space was identified and the tip of the catheter was positioned where intended in all dogs. Dog 1 developed transient Horners syndrome and dog 3 required intraoperative fentanyl during the first part of the procedure. Conclusion Paramedian approach with cephalad angulation is a suitable technique to place thoracic epidural catheters in dogs.OBJECTIVE To describe a technique for insertion of a thoracic epidural catheter. STUDY DESIGN Clinical report. ANIMALS Dogs (n = 3) undergoing thoracic wall resection and thoracotomy. METHODS A paramedian approach with cephalic angulation was used to place a 24-g epidural catheter in 3 dogs. Dogs 1 and 2 had left caudal thoracic wall resection and dog 3 had left thoracotomy. In dog 1, the epidural catheter was inserted at L2-L3 intervertebral space and the tip of the catheter advanced to the level of T13 vertebral body. In dog 2, the epidural catheter was inserted at T12-T13 intervertebral space and the tip of the catheter was advanced to the level of T8 vertebral body. In dog 3, the epidural catheter was inserted at T13-L1 intervertebral space and its tip advanced until reaching the vertebral body of T10. All dogs were administered a combination of bupivacaine and morphine through the epidural catheter to provide intra- and postoperative analgesia. RESULTS The peridural space was identified and the tip of the catheter was positioned where intended in all dogs. Dog 1 developed transient Horners syndrome and dog 3 required intraoperative fentanyl during the first part of the procedure. CONCLUSION Paramedian approach with cephalad angulation is a suitable technique to place thoracic epidural catheters in dogs.

Retrospective clinical evaluation of hypobaric spinal anaesthesia in dogs undergoing pelvic limb orthopaedic surgery

OBJECTIVE To evaluate intraoperative effects, complications, postoperative rescue analgesia requirement and presence of postoperative unilateral blockade after hypobaric spinal anaesthesia in dogs. METHODS Retrospective review of case records of dogs that underwent pelvic limb orthopaedic surgery and received hypobaric spinal anaesthesia. Cases that contained complete information on perioperative analgesia, end tidal anaesthetic agent, arterial blood pressure, postoperative urination, motor function and assessment at the sixth week re-examination were selected. RESULTS Twenty-four of forty-eight records were sufficiently complete to meet the selection criteria. Local anaesthetic dose and volume of the solution administered were 0 · 22 (±0 · 06) mg/kg and 0 · 16 (±0 · 05) mL/kg, respectively. Fentanyl was administered intraoperatively in seven dogs (29%); mean ± sd end-expired isoflurane was 1 · 09 ± 0 · 17%; hypotension was observed in nine dogs (37 · 5%). Unilateral blockade was documented in 18 dogs (75%); 6 dogs (25%) required methadone postoperatively; urinary retention was not observed. One dog developed steroid responsive meningitis arteritis. CLINICAL SIGNIFICANCE Hypobaric spinal anaesthesia achieved unilateral postoperative pelvic limb motor blockade in dogs, although bilateral block occurred in a proportion of animals; intraoperative hypotension was not infrequent. Fentanyl and postoperative methadone might be required to control nociception and pain, despite technical success in performing spinal anaesthesia.

A retrospective comparison of two analgesic strategies after uncomplicated tibial plateau levelling osteotomy in dogs

OBJECTIVE To compare the efficacy and side effects of postoperative methadone administered according to pain score (PS) or every 4 hours (Q4), after unilateral uncomplicated tibial plateau levelling osteotomy (TPLO) in dogs in which a peripheral nerve block (PNB) was administered. STUDY DESIGN Retrospective, case-control study. ANIMALS Clinical records of dogs that underwent a TPLO in 2015 were retrieved; 136 out of 174 dogs were included: 52 assigned to group PS, 84 to group Q4. METHODS In group PS, methadone was administered according to the short form of the Glasgow Composite Measure Pain Scale (CMPS-SF), whereas in group Q4 methadone was administered at 4 hour intervals. Demographic data, anaesthetic technique, surgery time, American Society of Anesthesiologists classification, PNB performed, local anaesthetic used and dose, anti-inflammatory drugs administered, end-expiratory fraction of isoflurane, perioperative opioid consumption, time to first postoperative methadone administration, pain scores, time to first pain score, food intake, number of postoperative observations, presence/absence of specific keywords representing the general state and behaviour of the animal, use of the operated limb and reaction to wound palpation were retrieved. Fishers exact test, chi-square test, Student t test or Mann-Whitney U test were used, considering p<0.05 significant. Odds ratios and 95% confidence intervals were calculated, when indicated. RESULTS Four times more methadone was administered to dogs in group Q4, and whilst not having lower pain scores or better short-term outcome (e.g. toe-touching and weight bearing), were 23.42 times (1.37 to 400.40) more likely to vomit, 3.76 (1.50 to 9.49) more likely to vocalize, and their food intake was 38% less than dogs in group PS. No dogs in group PS vomited postoperatively. CONCLUSIONS AND CLINICAL RELEVANCE Administration of methadone Q4 caused more side effects than administration guided by CMPS-SF. This should be considered when planning postoperative analgesia in dogs undergoing uncomplicated TPLO and in which a PNB has been performed.

Hiccup-Like Response in a Dog Anesthetized with Isoflurane

An eight-year-old, female intact Golden Retriever underwent magnetic resonance imaging (MRI) for investigation of urinary and faecal incontinence. Soon after induction of general anesthesia, tracheal intubation, and isoflurane administration, hiccup-like movements were evident. These hiccup-like movements did not respond to hyperventilation and increase of anesthetic. After having ruled out pulmonary disease, the animal was reanesthetized with a similar technique; hiccup-like movements reoccurred and did not stop after discontinuation of isoflurane and commencement of a propofol infusion. Eventually, a nondepolarizing neuromuscular blocking agent was administered to stop the hiccup-like response and allow MRI to be performed. This case report describes the pathophysiology of hiccup-like response and its management in a dog.