A retrospective comparison of two analgesic strategies after uncomplicated tibial plateau levelling osteotomy in dogs.

OBJECTIVE

To compare the efficacy and side effects of postoperative methadone administered according to pain score (PS) or every 4 hours (Q4), after unilateral uncomplicated tibial plateau levelling osteotomy (TPLO) in dogs in which a peripheral nerve block (PNB) was administered.

STUDY

DESIGN

Retrospective, case-control study.

ANIMALS: Clinical records of dogs that underwent a TPLO in 2015 were retrieved; 136 out of 174 dogs were included: 52 assigned to group PS, 84 to group Q4.

METHODS

In group PS, methadone was administered according to the short form of the Glasgow Composite Measure Pain Scale (CMPS-SF), whereas in group Q4 methadone was administered at 4 hour intervals. Demographic data, anaesthetic technique, surgery time, American Society of Anesthesiologists classification, PNB performed, local anaesthetic used and dose, anti-inflammatory drugs administered, end-expiratory fraction of isoflurane, perioperative opioid consumption, time to first postoperative methadone administration, pain scores, time to first pain score, food intake, number of postoperative observations, presence/absence of specific keywords representing the general state and behaviour of the animal, use of the operated limb and reaction to wound palpation were retrieved. Fisher's exact test, chi-square test, Student t test or Mann-Whitney U test were used, considering p<0.05 significant. Odds ratios and 95% confidence intervals were calculated, when indicated.

RESULTS

Four times more methadone was administered to dogs in group Q4, and whilst not having lower pain scores or better short-term outcome (e.g. toe-touching and weight bearing), were 23.42 times (1.37 to 400.40) more likely to vomit, 3.76 (1.50 to 9.49) more likely to vocalize, and their food intake was 38% less than dogs in group PS. No dogs in group PS vomited postoperatively.

CONCLUSIONS AND CLINICAL RELEVANCE: Administration of methadone Q4 caused more side effects than administration guided by CMPS-SF. This should be considered when planning postoperative analgesia in dogs undergoing uncomplicated TPLO and in which a PNB has been performed.