Background
Postoperative nausea and vomiting (PONV) is a common and unpleasant side-effect of anesthesia which negatively affects patient satisfaction and length of stay in the postanesthesia care unit (PACU). Repeated administration of ondansetron as a rescue antiemetic after intraoperative prophylactic dosing has been shown to be ineffective in treating PONV [1]. The current guidelines from the Society for Ambulatory Anesthesiology (SAMBA) recommend that, if a prophylactic antiemetic fails, an antiemetic from another class should be given [2]. SAMBA guidelines also recommend that antiemetics given as prophylaxis should not be repeated within 6 hours. However, many providers give ondansetron both as prophylaxis and as treatment for PONV. Although ondansetron is generally well-tolerated, adverse effects include headache, elevated liver enzymes, constipation, and QT prolongation. Our study sets out to determine the rate at which antiemetics given as prophylaxis are repeated as treatment for PONV, and to explore why this occurs.
Methods
All anesthesia residents received lectures on PONV and SAMBA guidelines, and key recommendations were reiterated in July 2016. We retrospectively reviewed 5485 general anesthesia cases at the UCSF Medical Center, between July 1, 2016, and February 28, 2017. Inclusion criteria included patients >18 years old, administration of inhaled anesthetic or nitrous oxide >30 minutes, and having resident involvement in the case. Frequency of combined prophylactic and rescue ondansetron administration in the PACU was determined from the electronic medical record (EMR). This was followed by an anonymous survey sent to all UCSF anesthesia residents, focusing on attitudes toward prescribing antiemetics both as prophylaxis and as treatment for PONV.
Results
362 (87.9%) of the 412 ondansetron administrations in the PACU were inappropriately given after ondansetron had already been administered prophylactically. Of the 71 anesthesia residents surveyed, 43 responded, of whom 35 (81.4%) listed the limited PACU order set (i.e. the only antiemetic on the PACU order set is ondansetron) as a barrier to prescribing an alternative antiemetic after ondansetron was already administered prophylactically, 55.8% reported prescribing ondansetron repeatedly for patients with allergies or contraindications to alternative antiemetics, and 37.2% said the difficulty and inconvenience of adding alternative orders to the order set (due to time constraints and EMR unwieldiness) was a barrier to prescribing alternative antiemetics.
Conclusions
Despite education on PONV guidelines, many providers prescribe the same class of antiemetics (particularly ondansetron) as both prophylaxis and treatment. Understanding barriers to optimizing antiemetic therapy is a critical first step in improving patient outcomes and potentially decreasing costs of receiving medications that confer no additional benefits. To address the barriers identified, a number of interventions, including an order set listing several options for antiemetic treatment and the addition of new classes of antiemetics to the anesthesia cart, will be enacted. Future directions involve examining the effects of these interventions, and exploring the optimal timing of ondansetron (i.e. prophylaxis vs. treatment of PONV) and efficacy of repeatedly administering antiemetics other than ondansetron.
References
- Kovac et al. J Clin Anesth. 1999 Sep;11(6):453-9.
- Tan TJ et al. Anesth Analg 2014; 118(1): 85-113.
