Evaluation of intraperitoneal ropivacaine for postoperative analgesia following ovariohysterectomy in dogs

Abstract

Objective To determine if intraperitoneal (IP) ropivacaine in conjunction with systemic analgesics improves postoperative analgesia following ovariohysterectomy (OHE) in dogs. Study Design Randomized, blinded, clinical trial. Animals Twenty dogs presented to the Veterinary Academic Hospital for elective OHE. Methods Dogs were premedicated with acepromazine (0.03 mg kg-1) and morphine (0.3 mg kg-1) intramuscularly (IM). Anaesthesia was induced with propofol (4 mg kg-1) intravenously (IV) and maintained with isoflurane (2%) in oxygen. Dogs were randomly assigned into one of two groups: group R received ropivacaine (n=10; 1 mg kg-1) and group S received 0.9 % saline (n=10; 0.1 mL kg-1) IP after linea alba incision. All OHE were performed by the same experienced surgeon. At completion of surgery, carprofen was administered IM at 4.4 mg kg-1. Pain was assessed using a mechanical nociceptive threshold (MNT) device before premedication, 30 minutes after premedication, as well as 2, 4 and 20 hours postextubation. Categorical data were analyzed using Fisher exact tests. Baseline quantitative data were compared between groups using Mann-Whitney U tests. Pain responses were compared between treatments using linear mixed models and post hoc comparisons were adjusted using Bonferroni correction of p-values. Results There were no significant differences (p>0.05) between the treatment groups regarding breed, age and weight. The effect of ropivacaine treatment to pressure required to elicit a pain response was not statistically significant different from saline. No adverse effects were observed following IP ropivacaine. Conclusions and clinical relevance IP administration of 1 mg kg-1 ropivacaine in conjunction with systemic analgesics did not improve postoperative analgesia following OHE in the dog.