PAPER 630 Journal of Small Animal Practice • Vol 54 • December 2013 • © 2013 British Small Animal Veterinary Association
Journal of Small Animal Practice (2013) 54, 630–637
Accepted: 14 September 2013; Published online: 24 October 2013
Retrospective comparison of two peripheral lumbosacral plexus blocks in dogs undergoing pelvic limb orthopaedic surgery
E. Vettorato, C. De Gennaro, S. Okushima and F. Corlet to
Dick White Referrals, Station Farm – London Road, Six Mile Bottom, Cambridgeshire CB80UH
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.
The use of loco-regional anaesthetic techniques, and in particular peripheral nerve blocks (PNBs), has gained popularity in veterinary anaesthesia, especially in dogs (Campoy et al. 2008, Mahler & Adogwa 2008, Portela et al. 2010, 2013, Vettorato et al. 2012, Campoy et al. 2012a,b). In humans, PNBs are preferred over neuraxial anaesthesia because of their unilateral blockade, lower incidence of intraoperative hypotension and postoperative urinary retention, shorter hospitalisation time and fewer neurological complications (Fowler et al. 2008).
The femoral (FN) and the sciatic (SN) nerves are responsible for the majority of the pelvic limb innervation in dogs (Evans & de Lahunta 2010). Several approaches have been experimentally described to localise FN and SN using a peripheral nerve stimulator. The FN can be localised: (1) at fifth and sixth lumbar (L5 to L6) intervertebral space using a dorsal-paravertebral approach (DPV) to the lumbar plexus (Campoy et al. 2008); (2) h t t p :/ / w w w .b s a v a .c o m /
Journal of Small Animal Practice • Vol 54 • December 2013 • © 2013 British Small Animal Veterinary Association 631
Pelvic limb peripheral nerve blocks in dogs 60 mmHg for two consecutive readings obtained at 5-minute intervals.
The amount of methadone (Comfortan; Eurovet Animal
Health) administered postoperatively was calculated adding the boluses of methadone administered as required according to the short form of the Glasgow Composite Measure Pain Scale (GCMPS-SF) for the first 24 postoperative hours (Reid et al. 2007). The dose obtained was divided by the animal’s bodyweight.
Pain assessment was performed at 2-hour intervals, according to standard perioperative care in the authors’ institution.
Dorsal-paravertebral (DPV) approach to the lumbar plexus
This block was performed as described by Campoy et al. (2008).
Briefly, with the dogs in lateral recumbency and the limb undergoing PNB uppermost, the skin area corresponding to L4–L6 vertebrae was aseptically prepared. The positive electrode for stimulation was applied to the skin of the ventral abdomen. An insulated stimulating needle (Locoplex; Vygon) of appropriate length was inserted lateral to the spinal process of L5 and advanced parallel to the sagittal plane between the transverse processes of L5–L6 until contraction of the quadriceps muscle was elicited. Initial current intensity was set at 1·5 to 2 mA, with pulse width of 0·1 ms and stimulation frequency at 1 to 2 Hz (EZstim II ES400; Life-Tech). Local anaesthetic was injected when the quadriceps muscle contraction was maintained using a current between 0·2 and 0·6 mA, following negative aspiration of blood to exclude intravascular needle placement.
Lateral Pre-Iliac (LPI) approach to the lumbar plexus
This block was performed as described by Portela et al. (2013).
Briefly, with the dog in lateral recumbency and the limb undergoing PNB uppermost, the skin covering the lumbar muscles cranially to the wing of ilium was aseptically prepared. The positive electrode for stimulation was applied to the skin of the ventral abdomen. An insulated stimulating needle of appropriate length was inserted cranially to the iliac wing and directed caudo-medially with an inclination of 30 to 45°. Initial current intensity was set at 1·5 to 2 mA with pulse width of 0·1 ms and stimulation frequency at 1 to 2 Hz. Local anaesthetic was injected when the quadriceps muscle contraction was maintained using a current between 0·2 and 0·6 mA, after negative aspiration of blood to exclude intravascular needle placement.
Sciatic Nerve (SN) block
The block was performed as described by Campoy et al. (2008).
Briefly, with the dog in lateral position and the limb undergoing