Postoperative Nausea and Vomiting in Adults
INTRODUCTION
At Winthrop University Hospital, we set out to determine the most cost-effective agent among three 5-hydroxy-tryptamine-3 (5-HT3) receptor antagonists—drug ondansetron (Zofran generic, GlaxoSmithKline), generic granisetron (Kytril generic, Roche), and dolasetron (Anzemet®, Aventis)—in preventing postoperative nausea and vomiting (PONV). PONV is a major complication for patients undergoing surgical procedures.
Four major risk factors influence the severity of PONV:
1. Patient characteristics. Younger age, female sex, obesity, a history of migraine, and gastroparesis are some patient-specific factors.
2. Duration and type of procedure. In general, the longer the surgical procedure, the greater the likelihood and severity of PONV. Gynecological, abdominal, laparoscopic, ophthalmic, and otolaryngological operations are associated with a higher incidence of PONV.
3. Type of anesthetic agent used. Anesthetics such as opioid analgesics, nitrous oxide, and inhalation agents are also known to increase the incidence of PONV. Patients who receive general anesthesia experience nausea and vomiting at rates of 37% and 20%, respectively.
4. Aspects associated with the postoperative recovery period. Postoperative risk factors include pain, dizziness, early ambulation, the use of opioids, hypotension, and premature oral intake. canadian antibiotics
Although the exact pathophysiology of PONV is not fully understood, it is believed to be the result of a compilation of several pathways in the vomiting center located in the brain. These include impulses from the chemoreceptor trigger zone (CTZ), the vestibular system associated with motion sickness; the higher cortical centers; the vagus nerve, which brings signals from the gastrointestinal tract; and the spino-reticular system, which triggers nausea related to physical injury.
Some causes of PONV include pharyngeal stimulation, gastrointestinal distention, abdominal surgery, anesthetic agents, opioid medications, and vestibular disturbances. Antiemetic agents are considered the first-line therapy in preventing and treating PONV. Prophylaxis is recommended in patients at moderate and high risk for developing PONV, but lower-risk patients do not need prophylactic agents.
The consequences of PONV include medical complications, such as muscular contractions associated with nausea and vomiting, which can cause damage to wound stitches, thus increasing the risk of bleeding. Other complications include esophageal tears, gastric herniation, muscular fatigue, and pulmonary aspiration of vomitus and regurgitation of stomach contents, resulting in respiratory obstruction, pulmonary inflammation, and aspiration pneumonia. Depending on the severity of PONV, patients may become dehydrated, and an electrolyte imbalance can develop.
Many studies have tried to quantify the costs associated with PONV. Hospitalization costs may increase by more than $400 per episode. Contributing factors include personnel time in caring for patients, the expense of disposable products, extra laundry, delayed hospital discharge, unanticipated re-admission, and potential reoperation.
The serotonin receptor antagonists ondansetron canadian, dolasetron, and granisetron canadian have been used in the prevention and treatment of PONV. They inhibit the action of serotonin at the 5-HT3 receptor peripherally in the gut, at the vagus nerve, and centrally in the CTZ, decreasing the stimulation of the medullary vomiting center. They have also become the first-line agents for preventing and treating PONV since the U.S. Food and Drug Administration (FDA) issued a black-box warning for droperidol (Inapsine®, Akorn) in 2001 because of the deaths associated with cardiac rhythm abnormalities secondary to its use.
Although these three agents are more expensive than other antiemetics such as metoclopramide (Reglan generic, Schwarz Pharma), promethazine (Phenergan®, Wyeth), prochlorperazine medication (Compazine drug, GlaxoSmithKline), and scopolamine (Transderm Scop®, Novartis), no other drugs have demonstrated efficacy to the extent of the serotonin antagonists while preventing the extrapyramidal side effects and sedation associated with the less expensive antiemetic agents. The side-effect profile of the serotonin antagonists includes headache, constipation, and elevated liver enzyme levels.
