Same-Day Surgery Reports: Current Concepts on Reducing Postoperative Nausea and Vomiting
Author: Alan P. Marco, MD, MMM, Associate Professor, Department of Anesthesiology, Medical College of Ohio, Toledo.
Peer Reviewer: Ronald B. Berggren, MD, FACS, Emeritus Professor of Surgery, College of Medicine and Public Health, Ohio State University, Columbus.
Introduction
Postoperative nausea and vomiting (PONV) has a significant impact on the patient and health care provider. The incidence varies between 20% and 30%, but has been reported to be as high as 60% or as low as 5%, depending on the mix of cases, treatment regimens, and definition of outcomes (nausea alone, retching, vomiting).1-3 High patient expectation in same-day surgery makes PONV an important issue. PONV causes distress to the patient, delays returning to normal activities, increases resource utilization in the post-anesthesia care unit (PACU), and may delay discharge even to the point of requiring admission.
In one study, patients desiring to avoid PONV were willing to spend up to $100 of their own money to avoid PONV.4 In another study, absence of PONV was almost twice as important to patients as absence of pain.5 While routine prophylaxis to prevent these complications may seem desirable, wide variations in efficacy and costs of treatment suggest that routine use is not warranted.
Physiology of PONV
Nausea is the feeling of impending vomiting that may or may not be associated with actual vomiting. Retching is a rhythmic activity of the respiratory muscles that typically precedes vomiting. Vomiting is the actual forceful expulsion of gastrointestinal contents.
Vomiting is a complex reflex that is coordinated by the vomiting center (VC) near the nucleus of the solitary tract, which receives input from the chemoreceptor trigger zone (CTZ) in the area postrema (AP). The VC also receives input from the vestibular apparatus, cerebellum, and higher cortical centers. Vomiting can be triggered by multiple factors, including unpleasant sights, smells, or ideas; pregnancy; pain; drugs; increased intracranial pressure; coronary artery occlusion with vasovagal syncope; or intra-abdominal pathology.
Distension and contraction of the gut can activate mechano-receptors there. Chemoreceptors in the gut are triggered by intraluminal toxins. Release of 5-hydroxytryptamine (5-HT) from enterochromaffin cells activates visceral afferents. Absorbed toxins also may be sensed in the area postrema, a vascular area on the floor of the fourth ventricle where the blood-brain barrier is incomplete. CTZ activity is affected by chemicals through the modulation of dopaminergic, histaminic, acetylcholinergic (muscarinic), and serotonergic receptors.
Pharmacology of PONV
The dopamine2 receptor is the classic receptor involved in emesis. Dopamine agonists, such as apomorphine and bromo-criptine, induce vomiting. Antagonists such as metoclopramide, droperidol, perphenazine, and perchloroperazine all have been used as antiemetics. However, side effects including extrapyramidal effects (akathisia and oculogyric crisis) or sedation, as well as cardiac effects may limit their utility. Droperidol is commonly used for PONV and is more effective against nausea than against vomiting. Metoclopramide is no more effective for PONV than placebo.6
Serotonin receptor antagonists (5-HT subtype 3 [5-HT3]) have become popular in the treatment PONV. 5-HT3 receptors are found in the AP, cerebral cortex, hippocampus, the gut mucosa, nerve endings, and primary afferent nerve fibers. Ondansetron, dolasetron, and granisetron have been found to be effective with minimal adverse effects. These three agents have equivalent safety and efficacy profiles. The serotonin antagonists are more effective against vomiting than nausea.7 Other serotonergic receptor antagonists such as those for the 5-HT1A subtype also hold promise as future antiemetic agents.8
Muscarinic antagonists that penetrate the blood-brain barrier can modulate centrally initiated vomiting as well as the peripheral gastrointestinal motor correlates of vomiting through a combination of central blockade of vestibular initiated motion sickness, peripheral reduction of salivary and gastric secretions, and prevention of relaxation of sphincters.
Atropine and scopolamine have been used in anesthetic practice for their antiemetic effects; glycopyrrolate does not cross the blood-brain barrier and has no antiemetic effect. The usefulness of scopolamine has been limited by its side effects, including drowsiness and confusion, especially in the elderly. However, it has received renewed interest since its availability in a new transdermal delivery system, especially for prolonged relief of PONV extending past discharge. In one meta-analysis, transdermal scopolamine has been shown to be effective compared to placebo, but the additional PONV relief is balanced by the incidence of side effects.9
Antihistaminics have been used to treat PONV. Many centrally acting antihistamines have anticholinergic activity, and it is unclear if their antagonism of histaminic or cholinergic receptors is responsible for their antiemetic action. Promethazine has anticholinergic, anti-5-HT, and antidopaminergic activity. Cyclizine also is effective, but its anticholinergic properties may contribute to sedation and dry mouth.
Neurokinin (NK1) receptors are widely distributed in the central and peripheral nervous systems. The first NK1 agonist to be identified was Substance P. Central NK1 receptors in the AP have a role in vomiting. Studies in an animal model as well as human studies suggest that NK1 receptor antagonism may have a role in the treatment of PONV in the future.10,11
Cannabiniods have been touted for the treatment of chemotherapy-induced nausea and vomiting. Their mechanism of action may be inhibition of the emetic pattern generator via descending pathways. They are similar in effectiveness to metoclopramide in PONV. Side effects such as dizziness, sedation, and dysphoria limit their usefulness.
Corticosteroids have been suggested for the prevention of PONV. Their mechanism of action in antiemesis is unknown. Reduction in inflammatory processes could lead to reduced stimuli from the operative site. While they have been used as monotherapy for chemotherapy and PONV, their efficacy is improved when used in combination with a 5-HT3 antagonist.12 Single doses of corticosteroids at the doses used for PONV (4 mg to 8 mg of dexamethasone in adults and 0.5 mg kg-1 in children) have few side effects.
Droperidol and the Black Box’ Warning
In December 2001, the Food and Drug Administration (FDA) issued a black box warning (the most serious warning for an FDA-approved drug set off in the text of the package insert by a black box as opposed to merely being listed in the Warning section) stating that droperidol, even at the low doses typically used for antiemesis, has been associated with prolongation of the QT interval or torsades de pointes, potentially resulting in death.13
However, the FDA failed to provide statistical information.14 The warning stated that a 12-lead ECG should be obtained to determine pre-existing QT prolongation prior to droperidol being used and that ECG monitoring should be continued for several hours after administration. Clearly, this additional monitoring would eliminate droperidol’s cost-effectiveness and would be unwieldy in the fast-paced outpatient setting.
Even if the monitoring is performed, it isn’t clear that it would detect patients at risk or prevent complications.15 Others have expressed doubt that the evidence supports the avoidance of such a widely used and effective drug.16,17 There were 12 adverse cardiac events associated with droperidol doses of 2.5 mg or less (five at doses of less than 1 mg), but more than 25 million doses of generic droperidol were sold in 2000 alone. Clearly, the incidence of such adverse events, even if truly caused by droperidol, is extremely low. Even large-scale studies have failed to show safety or efficacy advantages of ondansetron over droperidol. The 5-HT3 antagonists also may cause prolongation of the QT interval, and yet no "black box" warning has been issued for these drugs.
The main dilemma for clinicians is whether they should practice evidence-based medicine, which supports the use of droperidol as a cost-effective and safe therapy, or give in to the fear of lawsuits should an adverse event (related or not to droperidol) occur.
Risk Factors for PONV
Patient risk factors for PONV include age, gender (women are more prone to experiencing PONV than are men), phase of the menstrual cycle, obesity, anxiety, history of motion sickness, history of PONV, gastroparesis (e.g. diabetes or bowel obstruction), and full stomach. Genetics such as differences in metabolism that effect plasma concentrations of antiemetics also may be a factor.18,19
Several surgical procedures have been found to correlate with increased PONV. These include laparoscopic (especially gynecologic), strabismus repair, middle ear procedures, orchiopexy, stomach, duodenal, and gallbladder surgeries. Increased duration of surgery also correlates with increased PONV risk, but this is confounded by the increased duration of anesthesia.
Postoperative risk factors include pain. The relief of pain may relieve nausea, but opioids used for analgesia may increase the risk of PONV. Dizziness and early ambulation have been associated with PONV, especially in patients who have received opioids (which may confound this observation). Hypotension can lead to nausea, and in some cases, vasopressors such as ephedrine may be effective. Lastly, forcing oral intake may provoke PONV and delay discharge, especially in children.20
Anesthetic choices also can affect the incidence of PONV. The use of opioids frequently leads to increased PONV. However, opioids continue to be a mainstay of analgesia in medical care. The use of opioid-sparing techniques, such as the concomitant use of nonsteroidal anti-inflammatory drugs (NSAIDS), may help reduce the incidence of opioid-associated PONV. Propofol probably is most useful if given as a continuous infusion rather than a bolus at induction, especially for cases exceeding one hour.21,22
When using propofol during total intravenous anesthesia (TIVA), the choice of opioid does not significantly affect the risk of PONV.23 Some authors advocate the avoidance of opioids altogether and suggest local anesthesia combined with propofol for hypnosis and ketamine to cover the discomfort of the initial injection. In procedures where this technique can be used, such as cosmetic surgery, the incidence of PONV has been reduced drastically.24 However, this technique did not improve PONV when used for outpatient laparoscopy cases.25
Etomidate and ketamine are associated with PONV. Intubation and cricoid pressure also may cause vomiting by stimulating the gag reflex. The use of preoperative benzodiazepines to treat anxiety reduces the incidence of early PONV.26 Antagonism of neuromuscular block with cholinesterase inhibitors may promote muscarinic effects on the gastrointestinal tract and increase PONV. The concomitant use of anticholinergics may help offset this effect.
Inhalational agents have been associated with PONV. In some studies, nitrous oxide (N2O) has been associated with PONV, perhaps through gastric distention or vestibular stimulation from the diffusion of N2O into these gas-containing spaces. PONV has been associated with the use of N2O in gynecologic laparoscopy, so it may be prudent to avoid its use there. However, for short office-based surgical procedures, N2O does not have a significant effect on the incidence of PONV.27
Combinations of Antiemetics
Single agent therapy can reduce the incidence of PONV by 30%. Rather than give higher doses of the same agent, giving additional types of receptor antagonists may be more effective.28 The most common pairings have been dopamine antagonists with a 5-HT3 antagonist or dexamethasone. These combinations can yield a significant reduction in the incidence of PONV compared to either agent alone.29
Recent investigations suggest that targeting multiple receptors may be even more effective. One study showed that a multidrug regimen of dexamethasone, ondansetron, droperidol, and metoclopramide decreased PONV for 24 hours compared to both placebo and an propofol infusion that was continued four hours postoperatively.30 The combination of propofol, droperidol, and ondansetron also may be more effective than droperidol and ondansetron combined with a traditional anesthetic of isoflurane and N2O in oxygen.31
Nonpharmacologic Techniques
Traditionally, anesthesiologists turn to medications to treat PONV. However, drug therapy is not completely effective in eliminating PONV.
There is a growing trend toward complementary medicine in general, and several complementary techniques hold promise for the treatment of PONV.
Therapeutic suggestions given during anesthesia have been shown to decrease PONV.32 Supplemental oxygen (80%) has been shown to reduce the incidence of PONV in bowel surgery, possibly by reducing subclinical bowel ischemia.33 Increasing intravenous fluids during the procedure also can reduce the incidence of PONV, perhaps by increasing perfusion of the gut and reducing intestinal ischemia.34,35 Acupressure at the Pericardium 6 (P.6, Nei-Guan) point has been shown to be effective in adults, but not in children.36,37,38 Transcutaneous electrical stimulation at the P.6 point decreases nausea, but not vomiting after laparoscopic cholecystectomy.39
A postulated mechanism for the action of acupuncture is the release of beta endorphin that potentiates the endogenous antiemetic actions at the mu-opioid receptor.40 Also, there may be activation of serotonergic and norepinephrinergic fibers, thus changing serotonin transmission.41 Acupuncture and related techniques were comparable in efficacy to antiemetics (metoclopramide, cyclizine, droperidol, prochlorperazine) in adults for the prevention of early and late PONV. 42
In a study of transcutaneous electrical stimulation vs. ondansetron in combination with droperidol, transcutaneous electrical stimulation improved the efficacy of the combination therapy in this outpatient setting.43
Avoiding provoking PONV can be accomplished by slow transport of patients to the PACU (especially when turning corners) and transporting them feet first. A nontraditional (but not truly nonpharmacologic) treatment for transportation-related PONV is the inhalation of isopropyl alcohol vapors.44 This technique was shown to be effective in adults, but only transiently in children.45,46
Cost-effectiveness of Antiemetic Treatment
To optimize care, clinicians must be able to consider the risk factors and overall situation to decide who should be treated. While it is appealing to simply treat all patients, economic considerations as well as good medical care suggest that a more rational approach should be used. Some authors have attempted to develop risk scores for prediction of PONV.2 These can be assessed manually or by automated information systems.47 Patient risk factors can be put into a mathematical formula to develop a prediction score. A simple version of this is available on the Internet, although this tool has not been validated.48
Other authors have developed algorithms based on the identification of risk factors.49 (See Tables 1 and 2, above.)
Because physicians cannot predict with certainty which patients will suffer from PONV or which ones will benefit from treatment, some patients will receive unnecessary treatment and others will receive treatment that is ineffective. Both of these will result in cost to society in the form of increased medical expenditures. However, the practitioner cannot confine the examination of cost solely to drug acquisition costs.
There are other costs that are direct (such as nursing labor costs and supplies) and indirect (such as decreased patient satisfaction and delayed return to normal functioning).50
One of the problems with assessing the efficacy is that many researchers use surrogate outcomes (number of PONV episodes) rather than true outcomes (length of stay in the recovery room, unplanned hospital admissions, and decreased patient satisfaction).51 When the efficacy of antiemetic prophylaxis on surrogate outcomes or on true outcomes is considered, routine prophylactic administration of antiemetic medications results in little difference.52
Hospital-based operating rooms may have different concerns than ambulatory surgery centers or office-based practices. In the office-based setting, an extended stay in the PACU may be more directly linked to nursing labor costs than in the inpatient setting. When the full spectrum of costs is considered, prophylactic treatment of high-risk patients with antiemetics is more cost effective than placebo.53
The addition of metoclopramide, dolasetron, or ondansetron to a baseline therapy of droperidol and dexamethasone in an office-based setting did not improve outcomes, but they did significantly increase the direct cost of care.54 Thus, selective administration of antiemetics is needed to reduce overall costs, even though acquisition costs may be increased.
Some anesthetic regimens may be more effective than others at reducing the incidence of PONV and its associated costs. In one study, the use of total intravenous anesthesia with propofol-alfentanil was more cost effective than low flow desflurane with tropisetron in moderate risk patients.55 The choice of treatment drug also is important.
While ondansetron may be more effective than metoclopramide or droperidol at treating PONV, droperidol is more cost-effective even when costs of treatment failure (but not side effects of droperidol) are considered.56
For continued treatment of PONV in the postoperative period, prochlorperazine is more cost effective than ondansetron for inpatients after total hip or knee replacement procedures.57 Continued PONV after discharge from the ambulatory facility remains a problem.
Over-the-counter treatments are not consistently effective and unlike inpatients, outpatients cannot readily ask health care providers for treatment. Therapies to consider include the use of an ondansetron orally disintegrating tablet, transcutaneous acupoint electrical stimulation, or a transdermal scopolamine patch.58
Conclusion
PONV is still a frequent occurrence despite recent advances in therapy.
Cost-effective practice mandates the consideration of direct, indirect, and intangible costs of therapy. Focusing prophylaxis on those patients identified as being high risk should be routine in current practice. A multimodal approach of identifying preoperative risk factors, targeting different receptors, avoiding PONV triggers, and incorporating nonpharmacologic techniques should be used to minimize the impact of PONV on patients.
References
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18. Kaise R, Sezer O, Papies A, et al. Patient-tailored antiemetic treatment with 5-Hydroxytryptamine Type 3 receptor antagonists according to cytochrome P-450 2D6 genotypes. J Clin Oncol 2002; 20:2,805-2,811.
19. Oddby-Muhrbeck E, Eksborg S, Helander A, et al. Specific platelet characteristics in women experiencing postoperative nausea and vomiting after breast cancer surgery. Abstract presented at SFAI-veckan, Universitetssjukhuset Örebro; August 2001.
20. Schreiner MS, Nicolson SC, Martin T, et al. Should children drink before discharge from day surgery? Anesthesiology 1992; 76; 4:528-533.
21. Tramer M, Moore A, McQuay H. Propofol anaesthesia and postoperative nausea and vomiting: Quantitative systemic review of randomized controlled studies. Br J Anaesth 1997; 78:247-255.
22. Soppitt AJ, Glass PSA, Howell S, et al. The use of propofol; for its antiemetic effect: A survey of clinical practice in the United States. J Clin Anesth 2000; 12:265-269.
23. Dershwitz M, Michalowski P, Chang Y, et al. Postoperative nausea and vomiting after total intravenous anesthesia with propofol and remifentanil or alfentanil: How important is the opioid? J Clin Anesth 2002; 14:275-278.
24. Friedberg BL. Propofol-Ketamine technique: Dissociative anesthesia for office surgery (a five-year review of 1,264 cases). Aesth Plast Surg 1999; 23:70-75.
25. Vallejo MC, Romeo RC, Davis DJ, et al. Propofolketamine versus propofol-fentanyl for outpatient laparoscopy: Comparison of postoperative nausea, emesis, analgesia, and recovery. J Clin Anesth 2002. 14: 426-431.
26. Lessmann J, Heckhoff A, Vettermann J. Oral benzodiazepine premedication reduces postoperative nausea and vomiting. Anesthesiology 2002; 96:A33.
27. Tang J, Chen L, White PF, et al. Use of propofol for office-based anesthesia: Effect of nitrous oxide on recovery profile. J Clin Anesth 1999 11:226-230.
28. Habib AS, Gan TJ. Combination therapy for postoperative nausea and vomiting — a more effective prophylaxis? Ambulatory Surgery 2001; 9:59-71.
29. Shende D, Bharti N, Kathirvel S, et al. Combination of droperidol and ondansetron reduces PONV after pediatric strabismus surgery more than single drug therapy. Acta Anaesthesiol Scand 2001; 45:756-760.
30. Hammas B, Thorn S-E, Wattwil M. Superior prolonged antiemetic prophylaxis with a four-drug multimodal regimen- comparison with propofol or placebo. Acta Anaesthesiol Scand 2002; 46:232-237.
31. Gan TJ, Hill RP, Moretti E, et al. Triple antiemetic prophylaxis involving propofol, droperidol, and ondansetron is highly effective in preventing PONV. Anesth Analg 2000; 90:S4.
32. Eberhart LHJ, Döring H-J, Holzrichter P, et al. Therapeutic suggestions given during neuroleptanaesthesia decrease post-operative nausea and vomiting. European J Anaesthesiol 1998; 15:446-452.
33. Greif R, Laciny S, Rapf B, et al. Supplemental oxygen reduces the incidence of postoperative nausea and vomiting. Anesthesiology 1999; 91:1,246-1,252.
34. Elhakim M, El-Sebiae S, Kaschef N, et al. Intravenous fluid and postoperative nausea and vomiting after day-case termination of pregnancy. Acta Anaesthesiol Scand (Denmark). 1998; 42:216-219.
35. Ali SZ, Holtmann B, Taguchi A, et al. The effect of preoperative crystalloid fluid bolus on postoperative nausea and vomiting. Anesthesiology 2001; 95:A45.
36. Alkaissi A, Stalnert M, Kalman S. Effect and placebo effect of accupressure (p6) on nausea and vomiting after outpatient gynaecological surgery. Acta Anaesthesiol Scand 1999; 43;3:270-274.
37. Fan CF, Tanhui E, Joshi S, et al. Acupressure treatment for prevention of postoperative nausea and vomiting. Anesth Analg 1997; 84:821-825.
38. Shenkman Z, Holzman RS, Kim C, et al. Acupressure-acupuncture antiemetic prophylaxis in children undergoing tonsillectomy. Anesthesiology 1999; 90:1,311-1,326.
39. Zarate E, Mingus M, White PF, et al. The use of transcutaneous acupoint electrical stimulation for preventing nausea and vomiting after laparoscopic surgery. Anesth Analg 2001; 92:629-635.
40. Al-Sadi M, Newman B, Julious SA. Acupuncture in the prevention of postoperative nausea and vomiting. Anaesthesia 1997; 52:658-661.
41. Stein DJ, Birnbach DJ, Danzer BI, et al. Acupressure versus intravenous metoclopramide to prevent nausea and vomiting during spinal anesthesia for cesarean section. Anesth Analg 1997; 84:342-345.
42. Lee A, Done ML. The use of nonpharmacologic techniques to prevent postoperative nausea and vomiting: A meta-analysis. Anesth Analg 1999; 88:1,362-1,369.
43. White PF, Issioui T, Hu J, et al. Comparitive efficacy of acustimulation (ReliefBand) versus Ondansetron (Zofran) in combination with droperidol for preventing nausea and vomiting. Anesthesiology 2002; 97:1,075-1,081.
44. Smiler BG, Srock M. Isopropyl alcohol for transport-related nausea. Anesth Analg 1998. 87:1,214.
45. Merrit BA, Okyere CP, Jasinski DM. Isopropyl alcohol inhalation: Alternative treatment of postoperative nausea and vomiting. Nursing Research 2002; 51:125-128.
46. Wang S-M, Hofstadter MB, Kain ZN. An alternative method to alleviate postoperative nausea and vomiting in children. J Clin Anesth 1999; 11:231-234.
47. Junger A, Hartmann B, Benson M, et al. The use of an anesthesia information management system for prediction of antiemetic rescue treatment at the postanesthesia care unit. Anesth Analg 2001; 92:1,203-1,209.
48. Case Western University. Computer-based decision tool. Web site: http://www.anesth.com/; "Palm-based version."
49. Gan TJ. Postoperative nausea and vomiting- Can it be eliminated? JAMA 2002; 287:1,233-1,236.
50. Kovac A, Mingus M, Sung Y-F, et al. Reduced resource utilization in patients treated for postoperative nausea and vomiting with dolasetron mesylate. J Clin Anesth 1999; 11:235-241.
51. Fisher DM. Surrogate outcomes: Meaningful not! Anesthesiology 1999; 90;353-359.
52. Scuderi PE, James, RL, Harris L, et al. Antiemetic prophylaxis does not improve outcomes after outpatient surgery when compared to symptomatic treatment. Anesthesiology 1999; 90:360-371.
53. Hill RP, Lubarsky DA, Phillips-Bute B, et al. Cost-effectiveness of prophylactic antiemetic therapy with ondansetron, droperidol, or placebo. Anesthesiology 2000; 92:958-967.
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55. Eberhart LHJ, Bernert S, Wulf H, et al. Pharmacoeconomical model for cost calculation using a study on prophylaxis of nausea and vomiting in the postoperative phase as an example. Cost effectiveness analysis of a tropisetron supplemented desflurane anaesthesia in comparison to a propofol total intravenous anaesthesia (TIVA). Der Anaesthesist 2002; 51:475-481.
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CE/CME Objectives
This program is intended for surgeons, anesthetists, physician assistants, nurses, and other staff. This material is authorized for CME and CE credits beginning February 2003 and expiring February 2004.
Physicians and nurses participate in this continuing medical education/continuing education program by reading the article, using the provided references for further research, and studying the questions at the end of the article. To clarify confusion surrounding any questions answered incorrectly, please consult the source material.
After participating in this CE/CME activity, the learner will be able to:
- identify the portion of the brain that processes triggers of postoperative nausea and vomiting (PONV);
- list where antiemetic drugs such as ondansetron, dolasetron, and granisetron act primarily;
- identify which patients have the highest risk of PONV;
- list the combination therapy most likely to be effective for treating high-risk patients.
CE/CME Questions
1. Triggers of PONV come from many sources and these inputs are processed in the portion of the brain known as the:
A. peri-aqueductal grey (PG).
B. the chemoreceptor trigger zone (CTZ).
C. vomiting center (VC).
D. area postrema (AP).
E. choroid plexus (CP).
2. Antiemetic drugs such as ondansetron, dolasetron, and granisetron act primarily at:
A. dopaminergic receptors.
B. histaminergic receptors.
C. serotonergic receptors.
D. adrenergic receptors.
E. muscarinic receptors.
3. Which of the following patients has the highest risk of PONV?
A. 42-year-old anxious male smoker for carpal tunnel release
B. 79-year-old female smoker with hypertension for cataract extraction
C. 22-year-old male nonsmoker for knee arthroscopy under general anesthesia
D. 28-year-old female nonsmoker with a history of motion sickness for gynecologic laparoscopy
E. 23-year-old female smoker roller coaster aficionado for tubal ligation
4. Combination therapy has been proposed for treating high-risk patients. Which of these combinations is most likely to be effective?
A. Droperidol, ondansetron, metoclopramide
B. Ondansetron, tropisetron, granisetron
C. Metoclopramide, atropine, droperidol
D. Propofol, isoflurane, metoclopramide
E. Propofol, droperidol, ondansetron, dexamethasone
Postoperative nausea and vomiting (PONV) has a significant impact on the patient and health care provider. While routine prophylaxis to prevent PONV may seem desirable, wide variations in efficacy and costs of treatment suggest that routine use is not warranted.
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