Postoperative nausea and vomiting (PONV) are among the more common adverse events related to both inpatient and outpatient surgical procedures. On average, 20-30% of surgical patients suffer from nausea and vomiting postoperatively. The incidence is dependent on a variety of factors, including gender, type of surgery and anesthetic drugs used. The medical consequences of postoperative nausea and vomiting are usually minor, but the impact on patient comfort and on medical resources can be significant.

The recent Food and Drug Administration change in the labeling requirements for droperidol (the so-called "Black Box" warning) highlighting the risks of QT interval prolongation and torsades de pointes provides an opportunity to reassess how PONV is managed. It is important to note that, despite the somewhat unprecedented FDA actions, the medical literature strongly suggests that the use of droperidol is associated with a very low risk of complications. The severe restrictions placed on the use of droperidol now effectively limits the options available to clinicians to manage and prevent PONV. As a result, a greater emphasis has been placed on the use of ondansetron (Zofran) as a primary drug for both prevention and treatment of PONV. The reality is, when given as a single agent for prevention or treatment, ondansetron decreases the incidence of PONV by 20-30% compared to placebo.

Here are the combined results of the clinical trials of ondansetron in the treatment of PONV:

There is no statistical difference in the effectiveness of the 1mg, 4mg or 8mg dose of ondansetron. The clinical implication of this finding is that repeated doses of ondansetron above the 2mg dose in a 24-hour period will not add to patient management. If patients fail to respond or respond incompletely to a total of 2mg of ondansetron, other drugs should be used. Doses in excess of 2mg in a 24-hour period will not provide any additional relief of symptoms and may expose patients to an unnecessary risk of drug side effects.

These additional measures include the use of droperidol, metoclopramide, ephedrine, dexamethasone, and others in addition to a maximum dose of 2mg of ondansetron.

Important points to remember in the treatment of PONV include:

• No single treatment is effective in more than a minority of patients. If patients do not adequately respond to the recommended dose, combination therapy is necessary
• There is little to be gained clinically in administering ondansetron in doses above 2mg in a 24 hour period
• Patients who fail to respond to a total of 2 mg of ondansetron should be treated with other drug therapies

Selected Bibliography:

1. Tramer MR. A rational approach to the control of postoperative nausea and vomiting: evidence from systematic reviews. Part 1. Efficacy and harm of antiemetic interventions and methodological issues. Acta Anaesthesiol Scand 2001; 45(1):4-13.
2. Tramer MR, Moore AR, Reynolds JM, McQuay HJ.A quantitative systematic review of ondansetron in the treatment of established postoperative nausea and vomiting. BMJ 1997; 314(7087):1088-1092.

PONV Treatment Pathway

Step 1.

Ondansetron 2 mg IV and dexamethasone 4 mg IV as a single dose

If nausea and vomiting continues to be problematic after 30 minutes, proceed to step 2:

Step 2.

For the MGH only:

Haloperidol 0.25mg IV, may repeat times one in 30 minutes, or
Ephedrine 50 mg IM (35 mg for patients < 50 Kg). May be repeated x1 in 4 hours
*contraindicated in patients with cardiovascular or hypertensive disease*

and

Metoclopramide 20 mg IV. May be repeated x1 in 4 hours

If nausea and vomiting continues to be problematic after 30 minutes, proceed to step 3:

Step 3.

Promethazine 12.5 -25 mg IV q 4 h. or
Meclizine 25mg orally q 8 h. or
Prochlorperazine suppository 25 mg per rectum q 12 h.

If nausea and vomiting continues to be problematic, proceed to step 4:

Step 4.

Droperidol
Prior to prescribing droperidol, physician must determine that pre-administration EKG QTc interval is < 440 msec [males] or <450 msec [females]. If within guidelines, then
*Give droperidol 1.25 mg IV x 1 dose only
*Patient's EKG must be monitored for 2-3 hr post-dose.

Note: These guidelines were developed by an interdisciplinary group of clinicians from the BWH and MGH Pharmacy and Anesthesia Departments.