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Antiemetics
Case Synopsis
A 30-year-old female patient was scheduled for hysteroscopy as a day-case procedure. She has no past medical history of relevance. Metoclopramide 10 mg and ondansetron 4 mg were administered followed by propofol/fentanyl via intravenous induction and sevoflurane for maintenance of anesthesia. Postoperatively she had intractable vomiting that delayed her discharge from the postanesthesia care unit and was only controlled through the use of a combination of around-the-clock antiemetics for the following 48 hours, resulting in unplanned hospital admission.
Problem Analysis
Definition
One in three patients suffers postoperative nausea and vomiting (PONV). The incidence is higher for certain procedures (45% of gynecologic procedures and 80% in high-risk groups). PONV is rated by most surgical patients as the worst aspect of their perioperative experience (pain was second on the list). In the era of day-case surgery, the logistic and financial implications of unplanned overnight stay/readmission caused by severe PONV can be significant. Approaches to prophylactic and therapeutic measures are both inconsistent and of varying effectiveness.
Recognition
Nonanesthetic factors, such as mechanical bowel obstruction, pharmacologic agents, and increased intracranial pressure, can cause nausea and/or vomiting in the perioperative period. These factors should be considered independently as their pathophysiology and therapeutic approach are different.
Prevention and control of PONV has both prophylactic and therapeutic aspects and entails pharmacologic and nonpharmacologic measures. Almost all antiemetics are receptor agonists/antagonists that act centrally (and peripherally in case of metoclopramide).
Understanding their mechanism of action is crucial to appreciating the repertoire of their side effects.
Risk Assessment
Recent literature review has changed the perception of “traditional” risk factors for PONV.
Patient-Related Factors
Strong association exists between the patient age group (<50 years, >3 years) and PONV. There is sufficient evidence to indicate that female sex and history of PONV are considerable risk factors. The risk is reduced in smokers.
Historically, a number of factors were perceived to be significant contributors to the risk of PONV. Recent literature reviews have shed doubt on them, such as American Society of Anesthesiologists physical status, duration of perioperative fasting, use of nasogastric tube, early enteral intake/duration of fasting, anxiety, migraine, body mass index, and menstrual cycle phase.
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