Combined lidocaine and xylazine increases the duration of analgesia in proximal paravertebral blocks in adult dairy cattle compared to lidocaine alone.

Objective: To develop an ultrasound (US)-assisted proximal paravertebral block (PPVB) technique and compare the duration of analgesic effects of US-assisted PPVBs using lidocaine and lidocaine plus xylazine.

Methods: US-assisted PPVBs were performed in a hospital setting in 7 university-owned adult Holsteins with either 90 mL of lidocaine total or 89.4 mL of lidocaine plus 0.6 mL (12 mg) of xylazine in a randomized, blinded, cross-over design with each cow receiving each block after a 7-day washout period. Proximal paravertebral block success and duration were tested up to 8 hours after injection with a needle-pinprick test in 3 sites (dorsal, middle, and ventral) along a paralumbar fossa incision line beginning about 10 cm ventral to the transverse processes and about 10 cm caudal to the last rib. The success and duration of anesthesia of lidocaine and lidocaine-xylazine PPVBs, as well as differences between the 3 sites, were compared.

Results: The needle-pinprick analgesic scores were significantly different 4 hours after lidocaine and lidocaine-xylazine PPVBs at the dorsal and ventral sites along a flank incision. The lidocaine group returned to pre-PPVB scores significantly earlier (4 hours) than the lidocaine-xylazine group (6 hours).

Conclusions: The combination of lidocaine-xylazine significantly increased the duration of anesthesia compared to PPVBs performed with lidocaine alone.

Clinical relevance: Lidocaine and xylazine are readily available to veterinarians and relatively inexpensive. In a clinical setting, using lidocaine and xylazine to perform PPVBs may be useful to prolong flank anesthesia in adult cattle.