Is bupivacaine A-OK for feline OVHs?
Kathryn Primm, DVM, owns Applebrook Animal Hospital in Ooltewah, Tennessee, but has a growing career as a writer, a speaker and an online voice for veterinarians and pet owners alike.
Two recent studies indicate that the local anesthetic is effective for postoperative analgesia and seems to lack toxic effects in cats.
Can veterinarians add something to our feline pain control protocols that balances cost to pet owner as well as safety and efficacy for the patient? (Photo Getty Images)Controlling feline patients' pain can be especially challenging because of their special metabolism of certain compounds. Is there something we can add to our protocol that can balance cost to the client as well as safety and efficacy for the patient?
Local anesthetics have promise for stopping the wind-up of pain and improving overall recovery. These are appealing because they're cheaper and easy to administer, but there haven't been many studies on safety and efficacy. We know that intraperitoneal (IP) administration of local anesthetics, such as bupivacaine, reduces early postoperative analgesic requirements, pain scores and time to first-intervention analgesia after abdominal surgery in people.1-6 And in dogs undergoing ovariohysterectomy (OVH), pain scores after IP administration of bupivacaine were lower compared with a control group.7,8 Recently, two studies looked into whether IP bupivacaine might be beneficial in cats as well.
Study 1: Bupivacaine showed effective postop analgesia for cats
A study in in the Journal of Feline Medicine and Surgery evaluated the efficacy of IP bupivacaine (in combination with the opioid buprenorphine) in client-owned cats undergoing OVH. The study included 45 cats, which were anesthetized with acepromazine, propofol and isoflurane and also received buprenorphine. They were divided into three groups of 15 cats each, and a standard ventral midline approach for OVH was performed. The cats in the first group served as the control group and were given IP 0.9% saline solution. The positive control group received IP saline solution and meloxicam (0.2 mg/kg subcutaneously). The final group received IP bupivacaine (2 mg/kg).
Postoperative pain was evaluated by blinded observers who used three different scales: 1) a dynamic and interactive visual analog scale (DIVAS), 2) mechanical nociceptive thresholds, and 3) the UNESP-Botucatu multidimensional composite pain scale. Any cat that needed rescue analgesia was provided buprenorphine, meloxicam or both.
The findings suggested that cats treated with bupivacaine did get effective postoperative analgesia. The prevalence of rescue analgesia was comparable for the group treated with bupivacaine and buprenorphine to the positive control group (meloxicam and buprenorphine) and lower when compared with the opioid-only group.
Study 2: Bupivacaine used in cats wasn't toxic
A second study in the American Journal of Veterinary Research looked at the pharmacokinetics and safety following such IP use of bupivacaine. The researchers hypothesized that there would be detectable bupivacaine concentrations in the blood after IP administration, but thought that the toxicity would be low. Their study used eight cats and was set up similarly with the cats scheduled for routine OVH.
All cats were anesthetized with propofol and maintained with isoflurane. The cats were also given buprenorphine and meloxicam. Then a solution of 0.5% bupivacaine (2 mg/kg) was diluted with an equal volume of 0.9% saline solution, resulting in concentration of 0.25% bupivacaine. The solution was split into three parts so that it could be applied to three different areas of the peritoneal space: over the right and left ovarian pedicles and the caudal aspect of the uterus. Blood samples were evaluated for the plasma bupivacaine concentrations at different intervals after administration, and the cats were observed for signs of toxicosis, such as cardiovascular depression.9
In this study, IP administration of 0.25% bupivacaine (2 mg/kg) resulted in plasma concentrations that did not result in signs of bupivacaine toxicosis.
Because bupivacaine is affordable and now has been found to be safe and effective, we should all consider adding it to our pain protocols for routine OVH.
Benito J, Monteiro B, Lavoie AM, et al. Analgesic efficacy of intraperitoneal administration of bupivacaine in cats. J Feline Med Surg 2015; Epub ahead of print.
Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/26467541
Benito J, Monteiro BP, Beaudry F, et al. Pharmacokinetics of bupivacaine after intraperitoneal administration to cats undergoing ovariohysterectomy. Am J Vet Res 2016;77:641-645.
Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/27227503
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