Opioid administration has been associated with many adverse effects in dogs, including vomiting.1–4 Vomiting can lead to other adverse sequelae, such as gastric content aspiration, esophagitis and resultant stricture, tension on suture lines, venous blood pressure increase, subcutaneous bleeding, and prolonged hospitalization.5 Indeed, hydromorphone administration during the postanesthetic period in dogs with intervertebral disk disease is a risk factor for pneumonia.6
Hydromorphone is a synthetic opioid μ-receptor agonist with 5 times the potency of morphine and is the most commonly used preemptive and postoperative analgesic in the authors’ hospital.3,7 The hospital's typical protocol is for dogs undergoing orthopedic surgery to receive 0.1 mg/kg (0.05 mg/lb) of hydromorphone IV or IM as a premedication to provide intraoperative analgesia. After surgery, hydromorphone is administered IV every 4 hours for 8 to 24 hours to continue that analgesia, after which time orally and transdermally administered analgesics are used. Vomiting is occasionally observed in these dogs when hydromorphone is administered before surgery and, less commonly, when it is administered after surgery.
Emetic and antiemetic effects of opioids have been recognized in dogs, cats, ferrets, and humans.8–10 The emetic effects are a result of stimulation of the μ-opioid receptors in the CRTZ of the brain. On the other hand, the antiemetic effects are from stimulating μ-opioid receptors in the vomiting center of the brain.8–10 Studies1–3 have been conducted to characterize the frequency of vomiting associated with opioids administered at various doses and routes, with or without phenothiazines, in healthy, sedated dogs. Studies1,2,4,11 have also been performed to assess the frequency of vomiting in dogs after IM opioid administration. To the authors’ knowledge, the incidence of postoperative vomiting in dogs treated with hydromorphone has not yet been evaluated.
The purpose of the study reported here was to determine the frequency of vomiting during the postoperative period in dogs that underwent orthopedic surgery and received hydromorphone for analgesia. A second objective was to identify the route of hydromorphone administration (IM or IV) associated with a lower incidence of vomiting. We hypothesized that because drug absorption is generally slower with IM administration than with IV administration, the CRTZ might be stimulated before the vomiting center of the brain, resulting in a higher likelihood of vomiting in dogs treated IV versus IM.
Chemoreceptor trigger zone
JMP, version 7, SAS Institute Inc, Cary, NC.
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