Intra and postoperative effects of adding detomidine to a lidocaine paravertebral anaesthesia in cows undergoing standing abomasum displacement surgery

This study investigated the benefits of adding detomidine to a lidocaine proximal paravertebral nerve block (PPNB) for standing laparotomy in cattle. Forty adult cows undergoing surgery for abomasal displacement were randomly assigned to receive a PPNB with lidocaine (LIDO: 40ml 2% lidocaine per injection site) or lidocaine-detomidine (LIDO-DETO: lidocaine + 5μg/kg detomidine equally distributed to the lidocaine syringes). The PPNB was done at T13, L1 and L2 vertebra, always by the same investigator using a blind technique. Intraoperative sedation score, pain score, heart (HR) and respiratory rate (RR) were recorded before PPNB and repeatedly after (5, 10, 15min, then every 15min) by a blinded observer (ODA). Rescue analgesia (local lidocaine infiltration) was applied based on the blinded surgeon's decision. Quality of anaesthesia was also assessed by the surgeons using a visual analogue scale (VAS) at the end of the intervention. Postoperative pain was evaluated (ODA) using the Zürich Composite Measure Pain Scale (ZCMPS) and mechanical nociceptive threshold (MNT) testing at 0, 2, 6, 12, and 24hours. Surgery was completed in all cows, though two (LIDO-DETO) went into sternal recumbency. LIDO-DETO resulted in superior VAS (P < 0.001), higher sedation (P < 0.001), lower pain scores (P = 0.001), and reduced RR (P = 0.015). Postoperatively, LIDO-DETO cows showed significantly lower ZCMPS (P = 0.048) and higher MNT on the wound's left side (P = 0.026). Adding detomidine to lidocaine PPNB improved intraoperative anaesthesia quality with potential postoperative analgesic benefits.