Validation of the dorsal approach for the blockade of the femoral nerve using ultrasound and nerve electrolocation in cats

Comparison between Bilateral Ultrasound-Guided Quadratus Lumborum Block and Sacrococcygeal Epidural in Cats Undergoing Ovariectomy

BACKGROUND

Ultrasound-guided quadratus lumborum block (QLB) and sacrococcygeal epidural anaesthesia (ScE) have been used for neutering cats, providing effective pain relief.

OBJECTIVES

To compare the effects of the QLB with those of ScE in cats undergoing ovariectomies.

METHODS

Feral cats undergoing ovariectomy were premedicated with dexmedetomidine (20 μg kg-1) and methadone (0.2 mg kg-1) intramuscularly. Anaesthesia was induced with 2-4 mg kg-1 of propofol intravenously and maintained with isoflurane in oxygen. The cats were randomly allocated to the groups QLB (bilateral QLB with 0.4 mL kg-1 of 0.25% bupivacaine) and ScE (0.3 mL kg-1 of 0.25% bupivacaine). Hemodynamic data and analgesia rescue were collected at four intraoperative periods. The pain scale and motor block were assessed in both groups during the postoperative period.

RESULTS

The ScE results in increased hypotension, prolonged extubation time, and higher postoperative motor block than the QLB (p < 0.05). The QLB and ScE groups required a similar number of intraoperative rescues and presented the same postoperative pain scale classification.

CONCLUSIONS

The QLB with 0.25% bupivacaine is a potential alternative to ScE with 0.25% bupivacaine in perioperative pain management in elective cat ovariectomy. The QLB promoted less hypotension and postoperative motor block when compared with the ScE group.

Regional anesthetic techniques for the pelvic limb and abdominal wall in small animals: A review of the literature and technique description

Increasing interest in using peripheral nerve blocks in small animals is evident, given the numerous studies published recently on this topic in important veterinary journals. Initially, research was focused on intraoperative analgesia to the pelvic limb, and several descriptions of lumbosacral plexus, femoral and sciatic nerve blocks have been described in studies. There is recent interest in developing techniques for somatosensory blockade of the abdominal wall. This article is the second part of a two-part review of regional anesthesia (RA) in small animals, and its aim is to discuss the most relevant studies in the veterinary literature, where objective methods of nerve location have been used, and to illustrate in pictures the currently used techniques for providing RA to the abdominal wall and the pelvic limb in small animals.

Defining local nerve blocks for feline distal pelvic limb surgery: a cadaveric study

Objectives Anatomical and methodological detail is lacking regarding local anesthetic peripheral nerve block techniques for distal pelvic limb surgery in cats. The aim of this study was to develop, describe and test nerve block methods based on cadaveric dissections and dye injections. Methods Ten pairs of feline pelvic limbs (n = 20) were dissected and the tibial nerve (T n.), common fibular (peroneal) nerve (CF n., and its two branches, the superficial fibular [peroneal] nerve [SpF n.] and the deep fibular [peroneal] nerve [DpF n.]) and the saphenous nerve (Sa n.) were identified. Based on these dissections, a 'distal crus block' (selective blockade of the CF n., T n. and Sa n.) and a 'distal pes block' (selective blockade of the SpF n., DpF n., T n. and Sa n.) were developed for surgical procedures in two different regions of the distal pelvic limb. Techniques were tested using new methylene blue (NMB) dye injections in feline pelvic limbs (n = 12). Using a 25 G × 5/8 inch needle and 1 ml syringe, 0.1 ml/kg of NMB dye solution was injected at the site of the CF n., and 0.05 ml/kg was injected at the sites of the SpF n., DpF n., Sa n. and T n. The length and circumference (fully or partially stained) of each stained nerve were measured. Results Positive staining of nerves was observed in 12/12 limbs. The lengths stained for the CF n., DpF n., SpF n., Sa n. and T n. were 27.19 ± 7.13, 20.39 ± 5.57, 22.82 ± 7.13, 30.89 ± 6.99 and 25.16 ± 8.09 mm, respectively. The nerves were fully stained in 12, 12, 10, 11 and 11 out of 12 limbs, respectively. Conclusions and relevance These two, three-point injection methods may be an effective perioperative analgesia technique for feline distal pelvic limb procedures.

Sciatic and femoral nerve blockade using bupivacaine alone, or in combination with dexmedetomidine or buprenorphine in cats

The aim of this study was to determine the onset and offset of antinociception after sciatic (ScN) and femoral (FN) nerve blocks. Six healthy adult cats (4.8±1.3years; 4.3±0.4 kg) were included in a randomised, crossover, blinded and controlled study. Following sedation with dexmedetomidine (25 µg/kg, intramuscular), each ScN and FN injection was performed using 0.1 ml/kg of saline (CONTROL), bupivacaine (0.46 per cent, 0.46 mg/kg; BUPI), bupivacaine and dexmedetomidine (1 µg/kg; BUPI-DEX) or bupivacaine and buprenorphine (2.5 µg/kg; BUPI-BUPRE). Atipamezole (250 µg/kg) was administered after injections. Paw withdrawal thresholds (PWT) and motor blockade were evaluated before sedation and up to 24 hours. The PWT were significantly increased at half an hour in CONTROL, from two to four hours in BUPI and BUPI-DEX when compared with baseline. Motor blockade was observed between one and three hours in treatments using bupivacaine. Ability to walk was significantly impaired in BUPI at half an hour to two hours, BUPI-DEX at one to two hours and BUPI-BUPRE at two hours. Antinociception was observed in BUPI between one and eight hours, and in BUPI-DEX and BUPI-BUPRE between one and four hours. This study could not demonstrate a benefit of administering bupivacaine with dexmedetomidine or buprenorphine in cats. Results in BUPI-DEX may have been biased by the administration of atipamezole.