Efficacy of lumbosacral and sacrococcygeal epidural ropivacaine in dogs undergoing surgery for perineal hernia

Epidural anesthesia is commonly administered as part of balanced anesthesia for perioperative analgesia. The main goal of this randomized clinical trial was to compare the efficacy of two epidural approaches in dogs undergoing surgery for a perineal hernia. A secondary aim was to compare motor blockade. Intact ASA 1 and 2 male dogs, weighing ≤25 kg with no previous surgery for perineal hernia were enrolled. After premedication with IM acepromazine 0.02 mg/kg and butorphanol 0.3 mg/kg, general anesthesia was induced with propofol and maintained with sevoflurane in oxygen. Dogs were randomly allocated to receive either a lumbosacral (LS, n = 30) or a sacrococcygeal (SC, n = 26) epidural injection with ropivacaine 1% (0.2 mL/kg) under computed tomography guidance. Successful analgesia was defined as no need of intraoperative rescue analgesia (fentanyl 3 μg/kg IV). Clinical failure was defined as the need of more than two boluses of fentanyl/h each dog received meloxicam 0.2 mg/kg IV at the end of the surgery. The Glasgow Composite Pain Scale short form (GCPS-SF), tactile sensitivity, pressure pain thresholds and motor blockade were assessed at 4, 6, 8, and 24 h after the epidural injection. Methadone (0.2 mg/kg, IV) was administered if the GCPS-SF was ≥6/24 points. Differences between groups were analyzed with the Mann-Whitney U test, Student's t-test or Fisher's Exact test, as appropriate. Success rate was assessed for non-inferiority between groups. The non-inferiority margin was set at -10%. Epidural analgesia was successful in 24 dogs in group LS and 17 dogs in group SC (p = 0.243), resulting in success rates of 80 and 65% in LS and SC groups, respectively. The non-inferiority of group SC versus group LS was confirmed. Clinical failure was recorded in two dogs in group LS and one dog in group SC. No significant differences between groups were detected in the GCPS-SF score, tactile sensitivity, pressure pain thresholds, need of post-operative methadone, or motor blockade. Both epidural techniques are valuable analgesic options for perineal hernia repair in dogs.

Computer tomographic comparison of cranial spread of contrast in lumbosacral and sacrococcygeal epidural injections in dog cadavers

OBJECTIVE

To compare the cranial spread of epidural injectates between lumbosacral (LS) and sacrococcygeal (SCo) approaches in order to guide volume selection for SCo epidural anaesthesia in the dog.

STUDY DESIGN

Prospective, randomized cadaveric experimental study.

ANIMAL

A group of 13 adult greyhound cadavers.

METHODS

The greyhound cadavers were randomly allocated to receive an epidural injection of diluted contrast via the LS or SCo approach. Incremental volumes (0.1, 0.2, 0.4 and 0.6 mL kg^-1) were injected consecutively, and a computed tomography (CT) scan was completed following every volume increment. Cranial spread of contrast was recorded by counting the number of vertebrae cranial to the LS space that the injectate had reached, expressed as a vertebral value (n). This vertebral value was measured taking into consideration the percentage of the cord surrounded by contrast (vertebral canal coverage, %).

RESULTS

The cranial spread of contrast was similar at 0.1 mL kg^-1 [1 (0-3) versus 2 (1-3) n], 0.2 mL kg^-1 [3 (0-10) versus 3 (1-5) n], 0.4 mL kg^-1 [12 (9-18) versus 11 (3-19) n] and 0.6 mL kg^-1 [18 (12-20) versus 15 (10-23) n] for the LS and SCo injections, respectively (p = 0.945). There was a significant interaction between the volume injected and vertebral canal coverage (p < 0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

The cranial spread of contrast was similar, independent of whether the epidural injection was performed in the LS or SCo intervertebral space. Current volume guidelines used for the LS approach may produce similar distribution patterns when the SCo approach is used. Further studies are required in order to evaluate the in vivo effectiveness and the adequacy in differently sized dogs of the results found herein.