Prevention and treatment of postoperative nausea and vomiting

Emetic effects of morphine and piritramide

BACKGROUND

Successful management of postoperative pain requires that adequate analgesia is achieved without excessive adverse effects. Opioid-induced nausea and vomiting is known to impair patients' satisfaction, but there are no studies providing sufficient power to test the hypothesis that the incidence of opioid-induced nausea and vomiting differs between micro -opioid receptor agonists. Thus, we tested the hypothesis that the incidence of vomiting and nausea differs between morphine and piritramide.

METHODS

In a prospective, randomized, double-blind fashion, we administered either morphine (n=250) or piritramide (n=250) by patient-controlled analgesia (PCA) for postoperative pain relief. We used a bolus dose of 1.5 mg with a lockout time of 10 min. Incidence and intensity (numerical rating scale) of postoperative nausea, vomiting, pain, patient satisfaction (score 0-10), side-effects (score 0-3) and drug consumption were measured.

RESULTS

Mean drug consumption did not differ between the piritramide and morphine groups (30.8 (SD 22.4) mg day(-1) vs 28.4 (21.8) mg day(-1)) during the first postoperative day and there were no significant differences in the overall incidence of nausea (30% vs 27%) and vomiting (19% vs 15%). Intensity of nausea correlated inversely (P=0.01) with morphine consumption but not with piritramide consumption. Pain scores both at rest (2.2 (1.9) vs 2.6 (2)) and during movement (4.4 (2.2) vs 4.9 (2.3)) were slightly but significantly less with morphine.

CONCLUSIONS

Opioid-induced emesis was observed in about one-third of the patients using morphine and piritramide for PCA and the incidence of vomiting was one-half of that. Potential differences in the incidence of vomiting during PCA therapy between these micro-opioid receptor agonists can be excluded.

Advances in office-based anesthesia

PURPOSE OF REVIEW

The practice of office-based anesthesia is quickly emerging as an important field for the anesthesia provider. The number of procedures being done in offices around the country has steadily increased, as has the invasiveness of these procedures. This creates new anesthetic considerations. To date most training programs have not addressed this area of practice. As practitioners enter the field, however, they should have information as to how to provide quality care in a location where very often they are completely alone. Many of the safety mechanisms we as anesthesia providers take for granted in a hospital setting are often not present in a surgical office, and it becomes our responsibility to help in establishing standards.

RECENT FINDINGS

Some questions exist as to the 'safety' of many surgical offices in which anesthesia care is provided. Many medical professional societies have begun issuing recommendations as to the standards of care that should exist. Different anesthetic techniques are also emerging that are appropriate to the office setting.

SUMMARY

As office-based anesthesia continues to mature as a specialty, we the anesthesia providers must be proactive in establishing guidelines and recommendations to make the practice safe. We should be informed of the rules and regulations that exist in our states, and we should provide a voice for the patients who put their faith in us.

Effect of supplemental pre-operative fluid on postoperative nausea and vomiting

In a prospective, double-blind, randomised controlled trial, we studied the effects of pre-operative fluid load on post-operative nausea and vomiting. Eighty patients attending for laparoscopic cholecystectomy or gynaecological surgery were randomly allocated to receive 2 ml.kg-1 (conservative) or 15 ml.kg-1 (supplemental) Hartmann's solution intravenously, shortly before induction of anaesthesia. During the operation, fluid management was identical in both groups. During the first post-operative 24 h, post-operative nausea and vomiting occurred in 29 patients (73%) in the conservative fluid group and nine patients (23%) in the supplemental fluid group (p = 0.01). Supplemental pre-operative fluid is an inexpensive and safe therapy for reducing post-operative nausea and vomiting.

Benefits and risks of newer treatments for chemotherapy-induced and postoperative nausea and vomiting

Nausea and vomiting are common adverse effects of chemotherapy, radiation therapy, anaesthesia and surgery. The incidence of chemotherapy-induced nausea and vomiting (CINV) is estimated to vary from 30 to 90%, depending on the type of chemotherapeutic agent used. Radiation-induced emesis varies with anatomical site radiated but is estimated to have an overall incidence of approximately 40%. The incidence of postoperative nausea and vomiting (PONV) depends on the type of anaesthesia and surgery, but overall is estimated to be 20-30%. Evidence-based medicine and meta-analysis have been used to direct medical therapy to help determine equivalence, optimal dose, timing, safety and efficacy of antiemetic medications. Concepts such as the number needed to treat and number needed to harm are helpful to guide the clinician regarding the benefits and risks of a particular treatment. The serotonin 5-HT(3) receptor antagonists ondansetron, granisetron, tropisetron and dolasetron have been important additions to the antiemetic armamentarium. The 5-HT(3) receptor antagonists are similar in chemical structure, efficacy and adverse effect profile. They appear to have no important differences among themselves in clinical outcomes for CINV and PONV. Headache, dizziness, constipation and diarrhoea are their most common adverse effects, and when they occur they are usually mild and easily managed. Haemodynamic changes and extrapyramidal adverse effects are uncommon. ECG changes such as prolonged corrected QT (QTc) interval are infrequent, dose-related and overall judged to be clinically insignificant. As most studies with the 5-HT(3) antagonists have been conducted on relatively healthy patients, caution should be exercised when these drugs are used in susceptible patients with co-morbidities. The clinician must weigh the benefit of administering an antiemetic for CINV or PONV against the risk of occurrence of an adverse event.

General anesthesia for developmentally disabled dental care patients: a comparison of reinforced laryngeal mask airway and endotracheal intubation anesthesia

Providing dental care for developmentally disabled patients who require general anesthesia is challenging for both and dentists and anesthesiologists. This study aimed to compare the efficacy of two anesthetic methods for dental care. The researchers retrospectively analyzed morbidity data following anesthesia using either a reinforced laryngeal mask airway (LMA) or endotracheal intubation anesthesia for a two-year time period. The subjects were developmentally disabled patients receiving dental care. Statistical analyses were by unpaired student t-tests and chi-square tests. Patients were who anesthetized with a reinforced laryngeal mask airway had a significantly shorter recovery period and lower postanesthetic complication rates when compared to patients undergoing endotracheal intubation anesthesia. Although hypoxemia (SPO2 < 90%) during dental care occurred more frequently when using the reinforced laryngeal mask airway, the difference was not significant. Nausea and vomiting were the major complications in the postanesthetic care unit and after discharge. When complication rates were compared in the two patient groups, nausea and vomiting were significantly higher during postanesthetic care and after discharge in the intubated group. In conclusion, reinforced laryngeal mask airway provides general anesthesia with less risk of side effects for developmentally disabled patients undergoing dental care.

Dolasetron for the prevention of postoperative vomiting in children undergoing strabismus surgery

BACKGROUND

Children undergoing strabismus surgery have a high incidence of postoperative vomiting (POV). The purpose of this study was to assess the efficacy and safety of dolasetron for the prevention of emesis comparing a single 0.35 mg.kg-1 or 12.5 mg dose with placebo.

METHODS

Children aged 2-12 years with an ASA status of 1 or 2 undergoing strabismus surgery were randomized in a double-blind manner to one of three treatment groups. Patients were excluded with a history of previous postoperative vomiting or motion sickness, allergy to serotonin receptor antagonists or previous antiemetic administration within 24 h prior to enrollment. General anaesthesia was induced with sevoflurane and N2O/O2 and maintained with isoflurane and N2O/O2. The study medication was administered 15 min prior to the end of surgery. Patients experiencing two or more episodes of vomiting were rescued in the postanaesthesia care unit (PACU) with metoclopramide 0.15 mg.kg-1. A total of 118 patients were enrolled with documentation of the number and severity of vomiting episodes, time to awakening, PACU length of stay and postoperative agitation.

RESULTS

Patients with an acute complete response (ACR), defined as no emetic episodes and no rescue medication within 24 h of study drug administration were 62% (weight dose), 64% (fixed dose) and 33% (placebo, P < 0.05).

CONCLUSIONS

There was no statistical difference between the 0.35 mg.kg-1 dose and the fixed 12.5 mg dose of dolasetron with both reducing the incidence of POV.

Postoperative recovery and discharge

Ambulatory surgery provides quality care that is cost-effective. The use of innovative surgical and anesthetic techniques will allow larger numbers of patients to take advantage of the benefits of undergoing an elective operation on an ambulatory basis. Anesthesiologists will be faced with more complex surgery, which will require careful selection and assessment of patients to ensure continuity of the excellent safety record of ambulatory anesthesia. Minor adverse events, such as pain and PONV, are still common. The occurrence of these minor adverse advents is now the major area of quality assessment and an area where improvement could be targeted. Fast tracking facilitates earlier discharge, but we must ensure this has benefit to the patient as speedy discharge may mask the true incidence of adverse minor symptoms. This can lead to patient dissatisfaction and a poor impression of ambulatory surgery.

Management of postoperative nausea and vomiting in ambulatory surgery

The management of PONV has improved significantly over the years but remains a frequent occurrence in postoperative patients. Evaluation of individual patient risk and the consideration for prophylactic antiemetic in high-risk populations should reduce these unpleasant symptoms and help direct appropriate clinical strategies. Treatment following failure of prophylactic antiemetic therapy requires knowledge of previously used antiemetics and the time of their administration.

Management of postoperative nausea and vomiting in children

In spite of improvements in anesthesia techniques, the 'big little problem' of postoperative nausea and vomiting (PONV) still exists. PONV can prolong recovery room stay and hospitalization, and is one of the most common causes of hospital readmission after day surgery. While there is little evidence to support prophylactic administration of antiemetics in patients at low risk of PONV, the higher risk population could benefit from the use of adequate antiemetic drugs. A wide variety of pharmacological approaches have been reported to be effective, as well as some nonpharmacological approaches. Antiemetic drugs available to treat or prevent PONV include phenothiazines, antihistamines, anticholinergics, benzamides, butyrophenones and 5-HT(3) antagonists. Since available drugs still present undesired adverse effects and are not completely able to control PONV, clinical investigations are ongoing for more effective and better tolerated agents; indeed, the ideal antiemetic drug might be cost-effective for routine use.

Randomized, double-blinded comparison of tropisetron and placebo for prevention of postoperative nausea and vomiting after supratentorial craniotomy

This prospective, randomized, placebo-controlled, double-blinded study was designed to evaluate the efficacy of tropisetron in preventing postoperative nausea and vomiting after elective supratentorial craniotomy in adult patients. We studied 65 ASA physical status I-III patients aged 18 to 76 years who were undergoing elective craniotomy for resection of various supratentorial tumors. Patients were divided into two groups and received either 2 mg of tropisetron (group T) or saline placebo (group P) intravenously at the time of dural closure. A standard general anesthetic technique was used. Episodes of nausea and vomiting and the need for rescue antiemetic medication were recorded during 24 hours postoperatively. Demographic data, duration of surgery and anesthesia, and sedation scores were comparable in both groups. Nausea occurred in 30% of group T patients and in 46.7% of group P patients (P >.05). The incidence of emetic episodes was 26.7% and 56.7% in the two groups (P <.05). Rescue antiemetic medication was needed in 26.7% and 60% of the patients (P <.05). Administration of a single dose of tropisetron (2 mg intravenously) given at the time of dural closure was effective in reducing postoperative nausea and vomiting after elective craniotomy for supratentorial tumor resection in adult patients.

Pharmacotherapy of postoperative nausea and vomiting

Postoperative nausea and vomiting (PONV) are two of the most common and unpleasant side effects following anaesthesia and surgery. Despite the development of new anti-emetics and a vast amount of published research, PONV continues to be a problem, especially in high-risk patients. Recent interest has focused on the use of a combination of agents, acting on different receptors and the adoption of a multimodal approach to tackle this problem. The search for the most cost-effective strategy has also been a major goal. This article will discuss the risk factors and physiology of PONV, currently available therapies, the use of a multimodal approach and the cost-effectiveness of PONV management. Finally, recommendations for the prophylaxis and treatment of PONV will be discussed.

[Postoperative nausea and vomiting in adult patients]

OBJECTIVE

Identifying risk factors and predictive models for Postoperative Nausea and Vomiting (PONV) and developing antiemetic guidelines for its prevention and treatment.

DATA SOURCES

Medline (1997-2002) searches, using "postoperative nausea and vomiting" [MESH], complemented by handsearch.

STUDY SELECTION AND DATA EXTRACTION

Published randomised controlled trials, systematic reviews and multivariable analysis of large cohort studies were evaluated.

DATA SYNTHESIS

Avoiding PONV seems to be one of the highest priority for most patients. Its most important risk factors are volatile anaesthetics and opioids. If these are given to susceptible patients such as female, those with previous history of PONV or motion sickness and non-smoker, this is likely to result in PONV. For patients receiving volatile anaesthesia, simplified risk scores are available to estimate the individual risk of PONV. Patients at high risk for PONV may benefit from a multimodal approach which involves a) lowering the baseline risk (e.g. by total intravenous anaesthesia with propofol) with b) prophylactically given antiemetics such as droperidol, dexamethasone and serotonin antagonists, alone or in combination. In these selected patients, antiemetics are cost effective.

CONCLUSIONS

A strategy to prevent and treat PONV should depend on the individuals risk. However, its clinical usefulness and economic implications needs to be validated.

A systematic approach to the management of postoperative nausea and vomiting

Postoperative nausea and vomiting (PONV), a common complication after anesthesia and surgery, often results in delayed discharge with the patient's unpleasant symptoms continuing at home. To effectively prevent and treat PONV, it is important to understand the factors implicated in PONV, the mechanisms of PONV, the pharmacology of the antiemetic agents, and the nonpharmacologic measures that have been shown to be effective. The cause of PONV is likely to be multifactorial, with important predictors being female gender, history of PONV, and history of motion sickness. The vomiting center can be triggered by activation of dopamine, serotonin (type 3), histamine (type 1), and muscarinic cholingergic receptors in the chemoreceptor trigger zone and the nucleus tractus solitarus, as well as acetylcholine receptors in the vestibular apparatus, vagal afferents from the periphery, and the endocrine environment. Antiemetic agents such as the serotonin antagonists (eg, ondansetron, dolasetron), droperidol, antihistamines (eg, diphenhydramine, dimenhydrinate), and promethazine can prevent and treat PONV effectively. Transdermal scopolamine and dexamethasone have a role in the prevention of PONV, particularly for certain high-risk patients. Nonpharmacologic measures and alternative treatments such as hydration, maintaining blood pressure, acupressure techniques, trancutaneous acupoint stimulation, and isopropyl alcohol must not be overlooked. Finally, an evidence-based algorithm for the prevention and treatment of PONV in adults is presented.

Postoperative nausea and emesis

Watcha and White [51] have made recommendations for antiemetic therapy and prophylaxis based on published peer-reviewed studies. They range from no prophylaxis for patients at low risk to "multimodal" antiemetic therapy for those at the highest risk (Fig. 1) [10]. Recommendations for rescue therapy of breakthrough PONV are also provided. With this approach, it should be possible [figure: see text] to individualize prophylaxis and rescue therapy to achieve an optimal cost-effective management strategy for this uncomfortable postoperative complication.

How to study postoperative nausea and vomiting

Anesthesiological journals are flooded by innumerable studies of postoperative nausea and vomiting (PONV). Nevertheless, PONV remains a continuing problem with an average incidence of 20-30%. This paper should provide essential information for the design, conduct, and presentation of these studies. It should also increase comparability among future studies and help clinicians in assessing and reading the literature on PONV. First, future studies should address new and relevant questions instead of repeatedly investigating prophylactically given antiemetics whose main results are predictable (e.g. already proven by meta-analysis). Second, group comparability should be based on well-proven risk factors and a simplified risk score for predicting PONV. Endless listings of doubtful risk factors should be avoided. Third, a realistic sample size estimation should be performed, i.e. in most cases at least 100 patients per group are necessary. Fourth, nausea, vomiting and rescue medication should be recorded and reported separately with the corresponding incidences (and number of patients with these separate symptoms), and the main end-point should be PONV. The entire observation period should cover 24 h. Additional reporting of the early (0-2 h) and delayed (2-24 h) postoperative period is desirable and should consider single and cumulative incidences. Lastly, interpretation of results should take into account the study hypothesis, sources of potential bias or imprecision, and the difficulties associated with multiplicity of analysis and outcomes.

The economic impact of opioids on postoperative pain management

STUDY OBJECTIVE

To evaluate the consequences of opioid use for postoperative pain management and the degree to which these consequences may be reduced or minimized with opioid-sparing or opioid-replacement techniques.

DESIGN

Literature review relating to the economics of postoperative pain management. Comparisons between opioids and opioid-sparing techniques were identified and selected for study.

MEASUREMENTS AND MAIN RESULTS

Studies evaluating overall economic impacts or surrogate outcomes (e.g., resource use or recovery milestones) showed benefits with opioid-sparing therapies.

CONCLUSIONS

Opioids will likely remain an integral part of postoperative pain management, but side effects increase the costs of care. The challenge is to identify situations where opioid-sparing techniques improve surrogate economic measurements and decrease overall hospital costs.

Small-dose dexamethasone reduces nausea and vomiting after laparoscopic cholecystectomy: a comparison of tropisetron with saline

Dexamethasone is an effective antiemetic drug, but the efficacy of small-dose dexamethasone 5 mg on the prophylaxis of postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic cholecystectomy has not been evaluated. We, therefore, evaluated the prophylactic effect of small-dose dexamethasone (5 mg) on PONV in patients undergoing laparoscopic cholecystectomy. Tropisetron and saline served as controls. One-hundred-twenty patients scheduled for laparoscopic cholecystectomy were enrolled in a randomized, double-blinded, placebo-controlled study. At the induction of anesthesia, the Dexamethasone group received IV dexamethasone 5 mg, the Tropisetron group received IV tropisetron 2 mg, and the Placebo group received IV saline. We found that both dexamethasone and tropisetron significantly decreased the following variables: the total incidence of PONV (P < 0.01), more than four vomiting episodes (P < 0.05), and the proportions of patients requiring rescue antiemetics (P < 0.05). The differences between the Dexamethasone and Tropisetron groups were not significant. We conclude that prophylactic IV dexamethasone 5 mg significantly reduces the incidence of PONV in patients undergoing laparoscopic cholecystectomy. At this dose, dexamethasone is as effective as tropisetron 2 mg and is more effective than placebo.

IMPLICATIONS

We evaluated the prophylactic effect of small-dose dexamethasone (5 mg) on postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic cholecystectomy. Tropisetron (2 mg) and saline served as controls. We found that dexamethasone 5 mg (IV) significantly reduced the incidence of PONV in these patients, and, at this dose, dexamethasone was as effective as tropisetron and was more effective than placebo.

Antiemetic effects of granisetron, droperidol and dexamethasone in otologic surgery

The objective was to assess the antiemetic activity of granisetron, dexamethasone and droperidol in the otologic surgeries. Sixty patients in ASA (American Society of Anesthesiologists) I and II risk groups who underwent surgery for chronic otitis media were assessed in a double blind and randomized trial. The patients were divided into three equal groups. Single intravenous dose of granisetron (3 mg), granisetron (3 mg) plus dexamethasone (8 mg) and droperidol (1.25 mg) were prophylactically administered to the patients in group 1, group 2 and group 3, respectively, and their antiemetic actions were compared. The antiemetic effects of the drugs were not significantly different between the groups (P>0.05). The antiemetic effects also did not differ significantly in the early and late postoperative periods (P>0.05). In conclusion, the results of prophylactic use or side effects of granisetron, granisetron plus dexamethasone or droperidol are similar in middle ear surgery. Therefore, cost effectivity of the antiemetic prophylaxis should be reconsidered in otologic surgery in the light of the results of this study.

Clonidine in paediatric anaesthesia

PURPOSE OF REVIEW

This review aims to summarize results of recently published studies concerning clonidine application in paediatric anaesthesia, to analyse trends in these studies, and to discuss perspectives of the perioperative use of clonidine for children.

RECENT FINDINGS

Reassessment of clonidine premedication has revealed that oral clonidine is inferior to midazolam for preoperative sedation. Oral or intravenous clonidine has been successfully used for the prevention of sevoflurane-induced agitation during emergence from anaesthesia. Peripheral injection or caudal (epidural) administration of clonidine prolonged the duration and enhanced the quality of postoperative analgesia by local anaesthetics without severe side effects. However, some negative results concerning potentiation of postoperative analgesia with clonidine have been reported.

SUMMARY

Clonidine may be less favored than midazolam as premedication for children because of inferior clonidine-induced sedation. Additional comparative studies are required, however, to confirm this finding. On the other hand, clonidine-induced analgesia may well be useful and find wide application in paediatric anaesthesia. Prospective multicentre trials using a larger number of patients will be needed to verify the usefulness of caudal clonidine for postoperative pain relief. Prophylactic use of clonidine against sevoflurane-induced agitation may represent a new and promising application. Assessment of the efficacy of clonidine in potentiating regional anaesthesia/analgesia by local anaesthetics in children also needs more investigation. Moreover, it may be worthwhile to try new successful applications demonstrated in adults for paediatric anaesthesia.

Postoperative nausea and vomiting: understanding the enigma

Postoperative nausea and vomiting (PONV) remains one of the most common complications related to surgery and anesthesia. Referred to as the "big little problem," PONV complications range from minor patient discomfort to gastric aspiration or death. There are multiple contributing factors that stimulate the vomiting reflex in PONV; yet, no single component is typically the causative factor. It usually is a variety of factors that trigger this response. Because the causes of PONV are multifactorial, no single antiemetic medication has been 100% effective for its prevention. A thorough understanding of these factors and the pharmacology related to PONV is essential for the effective management of this common postoperative complication.

Volatile anaesthetics may be the main cause of early but not delayed postoperative vomiting: a randomized controlled trial of factorial design

BACKGROUND

Despite intensive research, the main causes of postoperative nausea and vomiting (PONV) remain unclear. We sought to quantify the relative importance of operative, anaesthetic and patient-specific risk factors to the development of PONV.

METHODS

We conducted a randomized controlled trial of 1180 children and adults at high risk for PONV scheduled for elective surgery. Using a five-way factorial design, we randomly assigned subjects by gender who were undergoing specific operative procedures, to receive various combinations of anaesthetics, opioids, and prophylactic antiemetics.

RESULTS

Of the 1180 patients, 355 (30.1% 95% CI (27.5-32.7%)) had at least one episode of postoperative vomiting (PV) within 24 h post-anaesthesia. In the early postoperative period (0-2 h), the leading risk factor for vomiting was the use of volatile anaesthetics, with similar odds ratios (OR (95% CI)) being found for isoflurane (19.8 (7.7-51.2)), enflurane (16.1 (6.2-41.8)) and sevoflurane (14.5 (5.6-37.4)). A dose-response relationship was present for the use of volatile anaesthetics. In contrast, no dose response existed for propofol anaesthesia. In the delayed postoperative period (2-24 h), the main predictors were being a child (5.7 (3.0-10.9)), PONV in the early period (3.4 (2.4-4.7)) and the use of postoperative opioids (2.5 (1.7-3.7)). The influence of the antiemetics was considerably smaller and did not interact with anaesthetic or surgical variables.

CONCLUSION

Volatile anaesthetics were the leading cause of early postoperative vomiting. The pro-emetic effect was larger than other risk factors. In patients at high risk for PONV, it would therefore make better sense to avoid inhalational anaesthesia rather than simply to add an antiemetic, which may still be needed to prevent or treat delayed vomiting.

Oral ondansetron, tropisetron or metoclopramide to prevent postoperative nausea and vomiting: a comparison in high-risk patients undergoing thyroid or parathyroid surgery

BACKGROUND

Oral antiemetic prophylaxis may be a practical alternative to intravenous administration. Intravenous ondansetron and tropisetron prevent postoperative nausea and vomiting (PONV) at least as efficiently as traditional antiemetics, droperidol and metoclopramide. We tested the hypothesis that the incidence of PONV after oral ondansetron or tropisetron prophylaxis is lower compared with metoclopramide among high-risk patients.

METHODS

In a prospective, double-blind study we studied 179 high-risk patients who received either ondansetron 16 mg, tropisetron 5 mg, or metoclopramide 10 mg orally 1 h before the operation. A standard general anesthetic technique and postoperative analgesia were used. The incidence of PONV and the need for rescue antiemetic medication was recorded for 24 h.

RESULTS

In the postanesthesia care unit, the incidence of PONV was lower after premedication with tropisetron compared with ondansetron and metoclopramide (15%, 32% and 39%, respectively). The incidence of PONV during 0-24 h was the same in each group (68%, 58% and 75% in the ondansetron, tropisetron and metoclopramide group, respectively), but the incidence of vomiting was significantly lower after ondansetron (34%) and tropisetron (22%) prophylaxis compared with metoclopramide (53%). The need for additional antiemetics was significantly lower after tropisetron prophylaxis compared with metoclopramide. Patient satisfaction was significantly higher after tropisetron than after metoclopramide.

CONCLUSIONS

In the initial period, the incidence of PONV was lower after premedication with oral tropisetron than after ondansetron or metoclopramide. Considering the entire 24-h postoperative period, the incidence of PONV was the same after all three premedications, but the incidence of vomiting was lower after oral ondansetron and tropisetron than after metoclopramide.

Comparison of predictive models for postoperative nausea and vomiting

BACKGROUND

In order to identify patients who would benefit from prophylactic amtiemetics, six predictive models have been described for the risk assessment of postoperative nausea and vomiting (PONV). This study compared the validity and practicability of these models in patients undergoing general anaesthesia.

METHODS

Data were analysed from 1566 patients who underwent balanced anaesthesia without prophylactic antiemetic treatment for various types of surgery. A systematic literature search identified six predictive models for PONV. These models were compared with respect to validity (discriminating power and calibration characteristics) and practicability. Discriminating power was measured by the area under the receiver operating characteristic curve (AUC) and calibration was assessed by weighted linear regression analysis between predicted and actual incidences of PONV. Practicability was assessed according to the number of factors to be considered for the model (the fewer factors the better), and whether the score could be used in combination with a previously applied cost-effective concept.

RESULTS

The incidence of PONV was 600/1566 (38.1%). The discriminating power (AUC) obtained by the models (named according to the first author) using the risk classes from the recommended prophylactic concept were as follows: Apfel, 0.68; Koivuranta, 0.66; Sinclair, 0.66; Palazzo, 0.63; Gan, 0.61; Scholz, 0.61. For four models, the following calibration curves (expressed as the slope and the offset) were plotted: Apfel, y=0.82x+0.01, r2=0.995; Koivuranta, y=1.13x-0.10, r2=0.999; Sinclair, y=0.49x+0.29, r2=0.789; Palazzo, y=0.30x+0.30, r2=0.763. The numbers of parameters to be considered were as follows: Apfel, 4; Koivuranta, 5; Palazzo, 5; Scholz, 9; Sinclair, 12; Gan, 14.

CONCLUSION

The simplified risk scores provided better discrimination and calibration properties compared with the more complex risk scores. Therefore, simplified risk scores can be recommended for antiemetic strategies in clinical practice as well as for group comparisons in randomized controlled antiemetic trials.

Influence of standardized orders on postoperative nausea and vomiting after gynecologic surgery

OBJECTIVE

The risk of postoperative nausea and vomiting (PONV) after gynecologic surgery remains high, despite effective prophylactic medications. Thus, the objectives of this study were to determine whether standardized orders for the prophylaxis and treatment of PONV in gynecologic surgery patients (1) reduce PONV occurrence, (2) reduce total costs, and (3) influence the choice of medications used for PONV prophylaxis and treatment.

METHODS

A retrospective design was employed in which a random sample of 200 patients was selected from each of the two 6-month phases before (pre) and after (post) the implementation of standardized orders for PONV prophylaxis and treatment. The primary outcome was the occurrence of any PONV episode. Logistic regression was used to adjust for potential confounding factors. All costs were in 1999 Canadian dollars (Canadian dollar = US$0.673 in 1999).

RESULTS

Characteristics were similar except for surgical and anesthesia length between phases. The proportion of patients who received PONV prophylaxis increased from 31% (pre) to 47% (post; p = 0.002). There was a reduction in the risk of a PONV event in the post-phase (odds ratio [OR] 0.67, 95% CI 0.67 to 0.97; p = 0.04). The risk of PONV was significantly reduced with the administration of prophylactic medications (OR 0.46, 95% CI 0.46 to 0.67; p = 0.001). There was a reduction in the mean number of PONV episodes in the post-phase (1.47 events) versus the pre-phase (1.81 events; p = 0.02). A reduction in mean PONV management costs was observed in the post-phase ($8.31, SD +/- 8.50) compared with the pre-phase ($10.23, SD +/- 8.25; p = 0.02). For mean prophylactic costs, these were significantly higher in the postimplementation phase compared with the preimplementation phase ($1.64, SD +/- 3.36 vs. $0.91, SD +/- 2.43; p = 0.013). For mean total PONV costs (prophylaxis plus management costs), there was a nonsignificant reduction in the postimplementation phase compared with the preimplementation phase ($9.95, SD +/- 9.20 vs. $11.15, SD +/- 8.51, respectively; p = 0.18). Univariate sensitivity analyses revealed that the economic results were sensitive to several parameters.

CONCLUSIONS

The implementation of preprinted order forms for PONV prophylaxis and treatment appears to be an effective and economically attractive strategy.

Ondansetron: a review of its use as an antiemetic in children

Ondansetron, a selective serotonin (5-hydroxytryptamine; 5-HT) 5-HT3 receptor antagonist, is an antiemetic agent available for use in adults and children. In children receiving ondansetron (multiple 5 mg/m2 or 0.15 mg/kg intravenous and/or oral doses) in addition to chemotherapy in 2 large (n > 100) non-comparative analyses, < or =2 emetic episodes were observed in 33 and 40% of cisplatin recipients, 48 and 68% of ifosfamide recipients, and 70 and 72% of patients receiving other chemotherapeutic regimens. In comparative trials, ondansetron was significantly more effective at reducing nausea and vomiting than metoclopramide or chlorpromazine (both combined with dexamethasone), although the incidence of delayed symptoms were similar between children receiving ondansetron and metoclopramide. In addition, dexamethasone significantly improved the antiemetic efficacy of ondansetron in 1 randomised trial. When used in children undergoing conditioning therapy (including total body irradiation) prior to bone marrow transplantation, ondansetron was significantly better at controlling nausea and vomiting than combined perphenazine and diphenhydramine therapy. In dose-ranging and large placebo-controlled trials, intravenous (0.075 to 0.15 mg/kg) or oral (0.1 mg/kg) ondansetron was significantly more effective than placebo in preventing emesis in children undergoing surgery associated with a high risk of postoperative nausea and vomiting (PONV) including tonsillectomy or strabismus repair. In comparative studies, intravenous administration of ondansetron 0.1 to 0.15 mg/kg was significantly superior to droperidol 0.02 to 0.075 mg/kg or metoclopramide 0.2 to 0.25 mg/kg in preventing emesis in children undergoing various surgical procedures. In comparison with other antiemetics, including prochlorperazine and dimenhydrinate, ondansetron generally showed greater prophylactic antiemetic efficacy. Ondansetron combined with dexamethasone was significantly more effective than ondansetron or dexamethasone alone, as was the combination of ondansetron with a propofol-based anaesthetic compared with either agent alone. Ondansetron is generally well tolerated in children, rarely necessitating treatment withdrawal. The most frequently reported adverse events were mild to moderate headache, constipation and diarrhoea in patients receiving chemotherapy. Wound problems, anxiety, headache, drowsiness and pyrexia were reported most frequently in patients postsurgery.

CONCLUSIONS

Ondansetron has shown good efficacy in the prevention of acute nausea and vomiting in children receiving moderately or highly emetogenic chemotherapy and/or irradiation, particularly when combined with dexamethasone. In the chemotherapy setting, ondansetron is significantly better than metoclopramide and chlorpromazine and has a more favourable tolerability profile. In children undergoing surgery, ondansetron demonstrated superior prophylactic antiemetic efficacy compared with placebo, droperidol and metoclopramide, and was relatively free of adverse events. Ondansetron is thus an effective first-line antiemetic in children undergoing chemotherapy, radiotherapy and surgery.

Pulmonary aspiration risk during emergency department procedural sedation--an examination of the role of fasting and sedation depth

The assessment of pre-procedure fasting and control of sedation depth are prominent elements of widely disseminated procedural sedation guidelines and of the Joint Commission on Accreditation of Healthcare Organizations' standards. Both exist primarily to minimize the risk of pulmonary aspiration of gastric contents. This paper critically examines the literature on pre-procedure fasting and controlling sedation depth in association with pulmonary aspiration, and interprets this evidence in the context of modern emergency medicine practice. The article reviews the pathophysiology of aspiration and changing concepts regarding aspiration risk over the last decade. After reviewing studies on aspiration risk during general anesthesia, the paper reviews the risk of aspiration during labor and delivery as a more appropriate comparison group for aspiration risk during emergency department procedural sedation and analgesia (ED PSA). It is noted that aspiration during ED PSA has not been reported in the medical literature and that aspiration during general anesthesia and labor and delivery is uncommon. The literature provides no compelling evidence to support specific fasting periods for either liquids or solids prior to PSA, and existing guidelines for elective patients are of necessity arbitrary and based upon consensus opinion. The article discusses the implications in the areas of training and preparedness, monitoring, and research for the emergency physician practicing PSA.

Combination therapy for postoperative nausea and vomiting - a more effective prophylaxis?

The problem of postoperative nausea and vomiting (PONV) remains far from being resolved. Despite the introduction of new classes of antiemetics and a vast amount of published research, there is a general impression that there has been little progress in this area. The multifactorial etiology of PONV might be better addressed using a combination of drugs acting at different receptor sites. This approach of balanced antiemesis may be the answer towards achieving a significant improvement in the management of PONV. This article will cover the different strategies used to prevent PONV with particular emphasis on combination antiemetics. A review of the currently available methods to manage PONV as well as the physiological and pharmacological basis of combination therapy is presented.

Efficacy of single-dose intravenous dolasetron versus ondansetron in the prevention of postoperative nausea and vomiting

BACKGROUND

Postoperative nausea and vomiting (PONV) is a significant problem in surgical patients. The 5-hydroxytryptamine3-receptor antagonists ondansetron, dolasetron, and granisetron are being used to prevent PONV and avoid the adverse events associated with traditional antiemetics such as antihistaminic agents, anticholinergic agents, and dopamine antagonists.

OBJECTIVE

Because practitioners have taken widely differing approaches to the selection and dosing of agents in this class, this retrospective study assessed the relative efficacy of i.v. dolasetron and ondansetron in preventing PONV when used according to their approved labeling.

METHODS

The medical charts of patients who underwent total abdominal hysterectomy or laparoscopic cholecystectomy and received either dolasetron 12.5 mg or ondansetron 4 mg were reviewed. Efficacy was assessed based on the number of episodes of PONV and time to the occurrence of PONV in the 24 hours after surgery.

RESULTS

Of 75 medical records reviewed, 59 met the criteria for inclusion in the efficacy analysis. There were no statistically significant between-group differences in demographic or baseline clinical characteristics. The majority of patients were obese (body mass index > or = 27 kg/m2), had no history of either PONV or motion sickness, and underwent total abdominal hysterectomy. PONV occurred in 11 of 25 (44%) patients receiving dolasetron and 18 of 34 (53%) patients receiving ondansetron. Four patients receiving dolasetron experienced PONV in the first 2 hours after surgery, compared with 7 patients receiving ondansetron.

CONCLUSION

There were no significant differences in efficacy between single doses of i.v. dolasetron 12.5 mg and i.v. ondansetron 4 mg in the prevention of PONV.

What can be expected from risk scores for predicting postoperative nausea and vomiting?

Several risk scores have been developed to calculate the probability of postoperative nausea and vomiting (PONV). However, the power to discriminate which individual will suffer from PONV is still limited. Thus, we wondered how the number of predictors in a score affects the discriminating power and how the characteristics of a population--which is needed to measure the power of a score--may affect the results. For ethical reasons and to be independent from centre specific populations, we developed a computer model to simulate virtual populations. Four populations were created according to number, frequency, and odds ratio of predictors. Population I: parameters were derived from a previously published paper to verify whether calculated and reported values are in accordance. Population II: a gynaecological population was created to investigate the impact of the study setting. Populations III and IV: to meet ideal assumptions a model with up to seven predictors with an odds ratio of 2 and 3 was tested, respectively. The discriminating power of a risk score was measured by the area under a receiver operating characteristic curve (AUC) and an increase of more than 0.025 per predictor was considered to be clinically relevant. The AUC of population I was similar to those reported in clinical investigations (0.72). The study setting had a considerable impact on the discriminating power since the AUC decreased to 0.65 in a gynaecological setting. The AUC with the 'idealized' populations III and IV was at best in the range of 0.7-0.8. The inclusion of more than five predictors did not lead to a clinically relevant improvement. The currently available simplified risk scores (with four or five predictors) are useful both as a method to estimate individual risk of PONV and as a method for comparing groups of patients for antiemetic trials. They are also superior to single predictor models which are just using the patients' history of PONV or female gender alone. However, our analysis suggests that the power to discriminate which indvidual will suffer from PONV will remain imperfect, even when more predictors are considered.

Ondansetron: a selective 5-HT(3) receptor antagonist and its applications in CNS-related disorders

Ondansetron is a selective 5-hydroxytryptamine(3) (5-HT(3)) receptor antagonist that has been introduced to clinical practice as an antiemetic for cancer treatment-induced and anesthesia-related nausea and vomiting. Its use under these circumstances is both prophylactic and therapeutic. It has a superior efficacy, safety and pharmacoeconomic profile compared with other groups of antiemetics, namely antidopaminergics, antihistamines and anticholinergics. However, its place in the management of anticipatory and delayed vomiting in cancer treatment and as a rescue antiemetic in surgical patients needs to be further explored. Furthermore, recent animal and human research also reflects its possible novel application in the treatment of other disease states, such as alcoholism, cocaine addiction, opioid withdrawal syndrome, anxiety disorders, gastrointestinal motility disorders, Tourette's syndrome and pruritus. This review revisits the widespread physiological and pathological effects of 5-HT and discusses both the basic science literature and the clinical developments responsible for the conventional and novel uses of ondansetron. In addition, new discoveries relating to the effects of ondansetron on other receptors/channels and their possible therapeutic applications are presented.