Physiology and pharmacology of nausea and vomiting

Nausea and vomiting are both very unpleasant experiences. The physiology is poorly understood; however, understanding what we do know is key to tailoring a preventative or therapeutic antiemetic regime. There are two key sites in the central nervous system implicated in the organization of the vomiting reflex: the vomiting centre and the chemoreceptor trigger zone. There are five key neurotransmitters involved in afferent feedback to these areas. These are histamine (H₁ receptors), dopamine (D₂), serotonin (5-HT₃), acetyl choline (muscarinic) and neurokinin (substance P). Postoperative nausea and vomiting will occur in around one-third of elective patients who have no prophylaxis. This can result in many detrimental effects including patient dissatisfaction, unplanned admission and prolonged recovery. It is therefore essential that clinicians understand how they can prevent and treat nausea and vomiting using either a single agent or a combination of antiemetics to target relevant receptors. Commonly used drugs include antihistamines, dopamine antagonists, serotonin antagonists and steroids. More novel agents are being developed such as aprepitant, a neurokinin receptor antagonist, palonosetron, a 5HT₃ receptor antagonist, and nabilone, a synthetic cannabinoid.     

Physiology and pharmacology of nausea and vomiting

The physiology of nausea and vomiting is poorly understood. The initiation of vomiting varies and may be due to motion, pregnancy, chemotherapy, gastric irritation or postoperative causes. Once initiated, vomiting occurs in two stages, retching and expulsion. The muscles responsible for this sequence of events are controlled by either a vomiting centre or a central pattern generator, probably in the area postrema and the nearby nucleus tractus solitarius. Drugs which induce vomiting include ipecacuanha, a gastric irritant, and apomorphine, a dopamine-receptor agonist. Opioid drugs also induce vomiting, but opioid antagonists are not useful to treat nausea and vomiting. Anti-emetic drugs consist of a variety of neurotransmitter antagonists and may act in the periphery, the central nervous system or both sites. The most important drugs are antagonists at muscarinic, dopamine D₂, 5-HT₃, histamine H₁ and neurokinin NK₁ receptors. These drugs are discussed with particular attention to post-operative nausea and vomiting (PONV).     

Incidence of nausea and vomiting in children after strabismus surgery following desflurane anaesthesia

In a prospective, randomized parallel study, 60 ASA I-III children aged 1-17 years, scheduled for elective strabismus surgery, were anaesthetized with desflurane without prophylactic antiemetic medication. The objective of the study was to determine the incidence of postoperative nausea and vomiting after general anaesthesia with desflurane. To decide whether nitrous oxide further influences these symptoms, the patients were randomly assigned to two groups of 30 patients each. One group received desflurane in oxygen/air and a second group received desflurane in oxygen/nitrous oxide. In all children, after intravenous induction and tracheal intubation, anaesthesia was administered as minimal flow anaesthesia with oxygen and nitrous oxide or air according to the random plan. The patients were observed for 48 postoperative hours until their discharge from the ward. The overall incidence of nausea was found to be 37%, and vomiting was seen in 32% of all patients. No statistical correlation was found between the incidence of postoperative emesis and the administration of nitrous oxide or the duration of general anaesthesia. Instead, the incidence of vomiting was 2.5-fold higher when surgery was performed on both eyes compared with one eye. The relatively low incidence of postoperative nausea and vomiting, as well as the quick recovery from anaesthesia, permitting an early discharge from the postoperative care unit to the ward, show desflurane to be a suitable volatile anaesthetic in strabismus surgery in children.     

Prevention and control of postoperative nausea and vomiting in post-craniotomy patients

Postoperative nausea and vomiting (PONV) are the most frequent side-effects in the postoperative period, impairing subjective well-being and having economic impact due to delayed discharge. However, emetic symptoms can also cause major medical complications, and post-craniotomy patients may be at an increased risk. A review and critical appraisal of the existing literature on PONV in post-craniotomy patients, and a comparison of these findings with the current knowledge on PONV in the general surgical population, leads to the following conclusions: (1) Despite the lack of a documented case of harm caused by retching or vomiting in a post-craniotomy patient, the potential risk caused by arterial hypertension and high intra-abdominal/intra-thoracic pressure leading to high intracranial pressure, forces to avoid PONV in these patients. (2) There is unclarity about a specifically increased (or decreased) risk for PONV in post-craniotomy patients compared with other surgical procedures. (3) The decision whether or not to administer an antiemetic should not be based primarily on risk scores for PONV but on the likelihood for potential catastrophic consequences of PONV. If such a risk cannot be ruled out, a multimodal antiemetic approach should be considered regardless of the individual risk. (4) Randomized controlled trials with antiemetics in post-craniotomy patients are limited with respect to sample size and methodological quality. This also impacts upon the meaning of meta-analyses performed with trials that showed marked heterogeneity and inconclusive results. (5) No studies on the treatment of established PONV are available. This highlights the need to transfer knowledge about PONV treatment from other surgical procedures. (6) Despite the possibility that PONV in post-craniotomy patients can be triggered by specific conditions (e.g. surgery near the area postrema at the floor of the fourth ventricle with the vomiting centre located nearby), recommendations based on trials in post-craniotomy patients may be flawed. Thus, general knowledge on prevention and treatment of PONV must adopted for craniotomy settings.     

Simplified algorithm for the prevention of postoperative nausea and vomiting: a before-and-after study

Background

Poor adherence to guidelines aimed at reducing the incidence of postoperative nausea and vomiting (PONV) is well known. In a before-and-after study, we tested the effectiveness of a simplified algorithm for PONV prophylaxis on the incidence of PONV.

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.     

术后恶心呕吐的风险评估及防治方法

术后恶心呕吐是最常见的术后并发症之一,防治其发生有重要的临床意义。现就近几年来关于术后恶心呕吐的风险因素、评估方法以及防治方面的研究进展作一综述。     

The effect of smoking on postoperative nausea and vomiting

In an attempt to quantify the postoperative effects of smoking, 327 consecutive patients undergoing arthroscopic day case knee surgery were given a standard anaesthetic consisting of an intravenous induction with propofol and fentanyl followed by inhalational maintenance using isoflurane in an oxygen and nitrous oxide mixture. Pre-operatively, patients were asked inter alia to give details of social smoking habits. Postoperatively, patients were given standard analgesic and anti-emetic drugs. Prior to discharge patients were asked to give details of postoperative nausea and vomiting together with details of the severity of postoperative pain. There were 85 smokers and 242 nonsmokers. Of the 327 patients, a total of 42 (13%) complained of postoperative nausea and vomiting. Of the smokers, only 6% complained of postoperative nausea and vomiting in contrast to 15% of the nonsmokers (p < 0.05). It is postulated that enzyme induction is the most likely reason for this anti-emetic effect. Possible ways in which this clinically beneficial mechanism can be utilised to improve outcome after anaesthesia are discussed.     

A prospective randomized blinded study of the effect of intravenous fluid therapy on postoperative nausea and vomiting in children undergoing strabismus surgery

BACKGROUND: Nausea and vomiting is a common postoperative complication that often necessitates the use of antiemetic agents. METHODS: In a prospective, randomized, double blind trial, the effect of perioperative fluid administration on postoperative adverse outcomes following anesthesia was studied. One hundred children undergoing strabismus repair were randomly assigned to receive 10 ml x kg(-1) x h(-1) (control group) or 30 ml x kg(-1) x h(-1) (superhydration group) of lactated Ringer's solution during the operation. During the first 24 h postoperatively, nausea and vomiting, thirst, pain, and fever were evaluated. RESULTS: Groups were similar with respect to demographic data, surgical procedures and baseline hemodynamic variables. In the first 24 h postoperatively, nausea and vomiting occurred in 27 patients (54%) of the control group and 11 (22%) of patients in the superhydration group (P = 0.001). Comparison of the superhydration group with the control group also showed a statistically significant benefit of superhydration on postoperative thirst (P = 0.0002) and fever (P = 0.02). The differences in nausea and vomiting, thirst, and fever remained significant after adjustment for age, gender, weight, and duration of surgery. There was no significant difference between the two groups in postoperative pain. CONCLUSIONS: Intravenous superhydration administration is an inexpensive and safe therapy for reducing postoperative nausea and vomiting and discomfort.     

芳香疗法缓解麻醉术后恶心呕吐的Meta分析

目的评价芳香疗法缓解麻醉术后恶心呕吐的效果,为临床护理提供参考。方法检索国内外相关数据库从建库至2017年12月纳入的麻醉术后采用芳香疗法的随机对照试验文献9篇,共计851例患者(芳香疗法组431例,对照组420例)。采用Cochrane协作网Revman5.1软件进行Meta分析。结果术后恶心呕吐VAS评分、术后恶心呕吐发生率,两组合并效应量比较,差异有统计学意义(均P<0.01)。结论芳香疗法缓解麻醉术后恶心呕吐具有良好的效果,推荐临床护理中应用。     

Postoperative nausea and vomiting

Postoperative nausea and vomiting (PONV) remains a common clinical problem that increases patient morbidity, healthcare costs and affects patient satisfaction. This article outlines the physiology, reviews the available drugs and suggests a structure using risk stratification that helps to plan sensible clinical management.     

Postoperative nausea and vomiting

Postoperative nausea and vomiting (PONV) remains a common clinical problem that increases healthcare costs and affects patient satisfaction and morbidity. This article outlines the physiology, reviews the available drugs and suggests a structure using risk stratification that helps to plan sensible clinical management.     

Impact of an antiemetic protocol on postoperative nausea and vomiting in children

The objective of the study was to demonstrate a decreased incidence of postoperative nausea and vomiting (PONV) in children through the use of an antiemetic protocol. PONV was recorded in children (1.5-15 years) after inpatient surgery under general anaesthesia in a prospective, interview based survey. Group 1 consisted of children having surgery 1 month before the introduction of a formalized antiemetic protocol and group 2, 2 months after its introduction. Data were collected over a 1-month period in each group. Outcome measures of nausea, emesis, antiemetic requirement and patient satisfaction were monitored for the first 24-h postoperative period. There were 272 children enrolled: 138 in group 1 and 134 in group 2. There was a difference between the two groups for gender (P=0.03), type of surgery (P=0.017), perioperative opioid (P=0.003) and perioperative antiemetic use (P=0.024). However, multivariate analysis did not demonstrate an impact on outcome from these factors. The incidence of postoperative nausea (PON) and postoperative vomiting (POV) following the introduction of the protocol was 36% and 34%, respectively. Moderate to severe nausea was decreased after introduction of the protocol (18% versus 9%, P=0.028) but moderate to severe vomiting failed to reach significance (19% versus 11%, P=0.078). The proportion of children who had repeated nausea decreased after the introduction of the protocol (17% versus 8%, P=0.02) but repeated episodes of vomiting remained unchanged (19% versus 14%). This was attributed to a significant increase in antiemetic prescribing by protocol in group 2 (10% versus 59%, P < 0.001). Patient satisfaction was high in both groups (85% versus 90%). The introduction of a postoperative antiemetic protocol improved prescribing frequency. This resulted in a decreased incidence of moderate to severe PON and a reduction in the number of patients with repeated nausea.     

Dexamethasone is as effective as ondansetron for the prevention of postoperative nausea and vomiting following breast surgery

INTRODUCTION: Postoperative nausea and vomiting remain a common problem following breast surgery. This study assesses whether dexamethasone is as effective as ondansetron in the control of postoperative nausea and vomiting (PONV). METHODS: Eighty ASA I-III patients undergoing breast surgery for carcinoma of the breast were included in the study. Following premedication with diazepam 5-10 mg, patients were induced with fentanyl 50 micro g and propofol 2-2.5 mg kg-1. A larynx mask was inserted and anesthesia maintained with sevoflurane in oxygen and nitrous oxide. Patients were then randomly divided into two groups: Group D (dexamethasone) was given 4 mg dexamethasone i.v. after induction and Group O (ondansetron) was given 4 mg ondansetron at the same time point. Postoperatively, nausea, vomiting and pain were recorded at 1-h intervals during 4 h, and thereafter every 4 h during 24 h. RESULTS: The incidence of PONV during 24 h was 37% and 33% in Group D and Group O, respectively (NS). No differences were found between the groups in the incidence of postoperative nausea, vomiting or pain at the different time intervals. No differences were found in the incidence of PONV in smokers vs. non-smokers. No side-effects of these drugs were observed. CONCLUSIONS: Ondansetron 4 mg or dexamethasone 4 mg are equally effective in the prevention of postoperative nausea and vomiting following breast surgery. Other factors being similar, the difference in cost between these drugs would favor the use of dexamethasone instead of ondansetron when monotherapy against PONV is used.