Comparison of effects of Amisulpride and Dexamethasone vs Ondansetron and Dexamethasone on post-operative nausea and vomiting in patients of middle ear surgery- A randomised, double blinded study

The term postoperative nausea and vomiting (PONV) is typically used to describe nausea and/or vomiting or retching in the first 24 h postoperatively. As a patient-specific concern, it has been reported to increase patient dissatisfaction and postoperative pain thus prolonging the stay in hospital. The overall incidence of Postoperative nausea and vomiting (PONV) is about 25-30% after general anesthesia and surgery.1 In particular, middle ear surgery under general anaesthesia is associated with a high incidence of PONV, accounting for 62-80%.2

Risk factors which contribute to increasing the incidence of postoperative nausea and vomiting, are younger age group (<50 years), female patients, history of motion sickness and postoperative nausea and vomiting, non-smokers and use of opioids3.

PONV, if not treated, may cause dehydration electrolyte imbalance as well as other complications such as incisional pain, wound dehiscence, aspiration pneumonitis, increased intracranial pressure.4

Various drugs have been used to prevent and treat the PONV like dexamethasone, metoclopramide, ondansetron, droperidol, granisetron etc, but none of them provide complete relief to all patients. A significant number of patients develop PONV even after getting the preventive drugs.5

Middle ear surgery may disturb the vestibular system, and opioids increase vestibular sensitivity. Vestibular stimulation increases the incidence of nausea and vomiting caused by opioids. Ondansetron is said to have a significant antiemetic effect on patients suffering from opioid-induced emesis. The site of inhibitory action of ondansetron on PONV after middle ear surgery might be the nucleus tractus solitarius which has a high concentration of 5-HT3 receptors. The prophylactic use of ondansetron on PONV in middle ear surgery has been studied previously with reduction in incidence of PONV as compared to control group.6

Recently, an injectable form of amisulpride (low single dose 5 mg IV) was shown to be effective at preventing PONV. This low dose neither show toxicity as compared to placebo and nor prolonged the QT interval enough to be clinically relevant in a randomized, double-blinded, placebo-controlled, multi-centered study.7

Dexamethasone for the prevention of PONV has been used 5–10 mg intravenously in adults. It is effective in preventing a late onset of PONV, as the onset of the effect of dexamethasone usually takes much longer time. For this reason, dexamethasone is not considered as an effective drug for immediate relief of existing PONV. So, a combination of dexamethasone and serotonin antagonist (ondansetron) may be the most effective treatment for preventing PONV. 8

It has been seen that a combination of dexamethasone and ondansetron is more effective in reducing PONV in middle ear surgery as compared to individual drug therapy.9

The fourth consensus guidelines for the management of post-operative nausea and vomiting (PONV) recommends a combination of two or more drugs acting through different mechanisms for the prophylaxis of PONV, as the etiology of PONV is complex and multi-factorial10.

No study was found in literature showing comparison of effects of amisulpride and dexamethasone vs ondansetron and dexamethasone on PONV.

Therefore,in the present study, effects of amisulpride and dexamethasone will be compared with the effects ondansetron and dexamethasone on incidence of PONV in the patients of middle ear surgery.