Postoperative nausea and vomiting (PONV) is one of the most common complications associated with surgery and anaesthesia and is defined as nausea and/or vomiting occurring within 24 hours after surgery.1,2 In the absence of pharmacological prophylaxis, its incidence ranges from 20–30% in the general surgical population and may increase to nearly 80% in high-risk patients.3,4 The etiology of PONV is complex and multifactorial and involves patient-, surgery-, anaesthesia-, and postoperative-related factors.5 Important patient-related risk factors include female gender, non-smoking status, previous history of motion sickness or PONV, obesity and anxiety, while anaesthetic drugs, type of surgery, postoperative pain, ambulation and opioid use also influence its occurrence.6,7 Prophylaxis is particularly important in high-risk patients, including females, patients receiving postoperative opioids and those with a previous history of motion sickness or PONV.8 PONV is frequently encountered following gynaecological, obstetric, ocular, breast and middle-ear surgeries.6 Patients undergoing major gynaecological procedures are particularly susceptible, with a reported incidence of approximately 50–75%.6,7 Besides causing considerable patient discomfort, PONV may prolong postoperative stay, delay discharge, result in unexpected hospital admission and increase healthcare costs.9 Persistent nausea and vomiting may also lead to dehydration, electrolyte imbalance, increased tension on surgical sutures, bleeding and an increased risk of pulmonary aspiration.6 Other reported complications include oesophageal rupture, subcutaneous emphysema and bilateral pneumothorax.10 No single antiemetic is completely effective in preventing PONV, particularly in high-risk patients.11 Serotonin 5-HT3 receptor antagonists, including ondansetron, granisetron, tropisetron and dolasetron, are widely used for the prevention and treatment of PONV and have fewer adverse effects than many traditional antiemetic agents.12 Since several receptor systems are involved in the pathogenesis of PONV, combining antiemetic drugs acting through different mechanisms may provide superior prophylaxis.11 Evidence increasingly supports a multimodal approach, with double or triple antiemetic combinations recommended for patients at high risk of PONV.11,13 Ondansetron, a 5-HT3 receptor antagonist, is commonly used for prophylaxis against PONV. Total abdominal hysterectomy is a frequently performed gynaecological procedure associated with a substantial risk of postoperative nausea and vomiting. Therefore, the present study was undertaken to compare the efficacy and safety of ondansetron alone with ondansetron in combination with dexamethasone for the prevention and reduction of PONV following elective abdominal hysterectomy under general anaesthesia, and to evaluate the role of dexamethasone as an adjuvant to ondansetron.

This prospective observational study was conducted in the Department of Anesthesiology and Critical Care, Sher-i-Kashmir Institute of Medical Sciences, from December 2019 to December 2021 after approval from the Institutional Ethics Committee. A total of 100 female patients aged 35–65 years, belonging to ASA physical status I or II and scheduled for elective total abdominal hysterectomy under general anaesthesia, were included after obtaining written informed consent. Patients with a history of smoking, drug or alcohol abuse, peptic ulcer disease, renal impairment, recent antiemetic use, pregnancy or lactation, menstruation, motion sickness, or previous postoperative nausea and vomiting were excluded. Patients were allocated into two groups of 50 each on the basis of days of the week. Group A received ondansetron 4 mg intravenously, while Group B received ondansetron 4 mg plus dexamethasone 8 mg intravenously. Study drugs were diluted with normal saline to a total volume of 5 mL and administered 5 minutes before induction of anaesthesia. General anaesthesia was standardized in all patients. Anaesthesia was induced with propofol 2 mg/kg and fentanyl 2 µg/kg, while rocuronium 0.5 mg/kg was used to facilitate endotracheal intubation. Anaesthesia was maintained with oxygen, nitrous oxide and isoflurane, with ventilation adjusted to maintain end-tidal CO₂ between 30 and 35 mmHg. At the end of surgery, residual neuromuscular blockade was reversed with neostigmine 60µg/kg and glycopyrrolate 10 µg/kg, followed by extubation after adequate recovery. The incidence of postoperative nausea and vomiting (PONV) was assessed during the first 24 hours after surgery at 0–6, 6–12, 12–18 and 18–24 hours. PONV severity was graded as: score 0, no nausea or vomiting; score 1, nausea only; and score 2, retching or vomiting. Complete response was defined as absence of nausea, retching or vomiting without the need for rescue antiemetic therapy. Intravenous metoclopramide 4 mg was administered as rescue antiemetic when clinically indicated. Data were entered into Microsoft Excel and analysed using SPSS version 20.0. Continuous variables were expressed as mean ± standard deviation, while categorical variables were presented as frequencies and percentages. Continuous variables were compared using the independent Student’s t-test or Mann–Whitney U test, as appropriate, whereas categorical variables were compared using the Chi-square test or Fisher’s exact test. A two-tailed p-value <0.05 was considered statistically significant.

A total of 100 patients undergoing elective total abdominal hysterectomy under general anaesthesia were evaluated, with 50 patients each in Group A (ondansetron 4 mg) and Group B (ondansetron 4 mg + dexamethasone 8 mg). The two groups were comparable with respect to age, body weight and duration of surgery, indicating similar baseline characteristics. The principal findings were a significantly lower incidence and severity of PONV with the ondansetron–dexamethasone combination during the early postoperative period, particularly during the first 12 hours. The requirement for rescue antiemetic was also lower in Group B, and the mean amount of rescue metoclopramide required over 24 hours was significantly reduced with combination therapy. Table 1: Baseline characteristics of the study groups Characteristic Group A (n=50) Group B (n=50) P-value Age, years (Mean ± SD) 45.5 ± 7.69 46.4 ± 7.79 0.545 Weight, kg (Mean ± SD) 60.1 ± 5.18 59.2 ± 5.31 0.373 Duration of surgery, min (Mean ± SD) 69.6 ± 15.35 70.8 ± 14.26 0.686 The two groups were comparable with respect to baseline characteristics. The mean age was 45.5 ± 7.69 years in Group A and 46.4 ± 7.79 years in Group B (p=0.545). The mean body weight was 60.1 ± 5.18 kg in Group A and 59.2 ± 5.31 kg in Group B (p=0.373). The mean duration of surgery was 69.6 ± 15.35 minutes in Group A and 70.8 ± 14.26 minutes in Group B (p=0.686). None of these differences were statistically significant, indicating that both groups were well matched for age, weight, and duration of surgery. Table 2: Incidence and severity of PONV during the first 24 postoperative hours Postoperative interval Outcome Group A n (%) Group B n (%) P-value 0–6 h No PONV 37 (74) 46 (92) 0.043 Nausea only 7 (14) 3 (6) Retching/vomiting 6 (12) 1 (2) 6–12 h No PONV 41 (82) 48 (96) 0.041 Nausea only 6 (12) 2 (4) Retching/vomiting 3 (6) 0 (0) 12–18 h No PONV 47 (94) 49 (98) 0.503 Nausea only 2 (4) 1 (2) Retching/vomiting 1 (2) 0 (0) 18–24 h No PONV 48 (96) 50 (100) 0.153 Nausea only 2 (4) 0 (0) Retching/vomiting 0 (0) 0 (0) During the first 0–6 hours, complete response with no PONV was observed in 37 patients (74%) in Group A compared with 46 patients (92%) in Group B. Nausea occurred in 7 (14%) versus 3 (6%), while retching/vomiting occurred in 6 (12%) versus 1 (2%), respectively. The difference between the groups was statistically significant (p=0.043). During 6–12 hours, no PONV was seen in 41 patients (82%) in Group A and 48 patients (96%) in Group B. Nausea was reported in 6 (12%) versus 2 (4%), and retching/vomiting in 3 (6%) versus 0 (0%), respectively. This difference was also statistically significant (p=0.041). During 12–18 hours, no PONV was observed in 47 (94%) patients in Group A and 49 (98%) in Group B; the difference was not statistically significant (p=0.503). Similarly, during 18–24 hours, no PONV was seen in 48 (96%) patients in Group A and 50 (100%) in Group B, with no significant difference (p=0.153). Table 3: Requirement for rescue antiemetic during the postoperative period Postoperative interval Group A n (%) Group B n (%) P-value 0–6 h 9 (18) 2 (4) 0.025 6–12 h 4 (8) 1 (2) 0.362 12–18 h 1 (2) 0 (0) 1.000 18–24 h 1 (2) 0 (0) 1.000 The requirement for rescue antiemetic was consistently lower in Group B than in Group A throughout the 24-hour postoperative period. During the first 0–6 hours, rescue antiemetic was required in 9 patients (18%) in Group A compared with 2 patients (4%) in Group B, and this difference was statistically significant (p=0.025). During 6–12 hours, rescue antiemetic was required in 4 patients (8%) in Group A and 1 patient (2%) in Group B; however, the difference was not statistically significant (p=0.362). During both 12–18 hours and 18–24 hours, rescue antiemetic was required in 1 patient (2%) in Group A and in none of the patients in Group B, with no statistically significant difference (p=1.000 for both intervals). Table 4: Amount of rescue antiemetic required over 24 hours Group Patients requiring rescue antiemetic (n) Mean dose (mg) SD Range (mg) P-value Group A 15 16.8 2.24 12–20 0.027 Group B 3 13.3 2.31 12–16 Over the first 24 postoperative hours, rescue antiemetic was required in 15 patients in Group A compared with only 3 patients in Group B. Among those requiring rescue therapy, the mean dose was 16.8 ± 2.24 mg in Group A and 13.3 ± 2.31 mg in Group B, with dose ranges of 12–20 mg and 12–16 mg, respectively. The difference in the amount of rescue antiemetic required between the two groups was statistically significant (p=0.027).

Postoperative nausea and vomiting (PONV) remains a common and distressing complication after anaesthesia, with a reported incidence ranging from 20% to 80%.14 Female sex is an established risk factor, and women undergoing total abdominal hysterectomy are considered particularly susceptible to PONV.7,15 Although prophylactic antiemetics reduce its incidence, no single agent provides complete prevention.16 In the present study, the two groups were comparable with respect to age, weight and duration of surgery. During the first 0–6 hours, PONV occurred in 26% of Group A compared with 8% of Group B, and the difference was statistically significant (p=0.043). Similar findings were reported by D'souza N et al., (2010)17, who observed lower early PONV with dexamethasone-containing prophylaxis, and by Dhawale RN et al., (2019)18, who found ondansetron with dexamethasone more effective than ondansetron alone in reducing early postoperative nausea. During 6–12 hours, PONV occurred in 18% of Group A and 4% of Group B (p=0.041). These findings were comparable to those of Rajeeva V et al.,19 who reported significantly lower PONV with the ondansetron–dexamethasone combination, and Oloando LL et al., who also found combination therapy more effective than ondansetron alone.20 During 12–18 hours, PONV occurred in 6% of Group A and 2% of Group B (p=0.503), while during 18–24 hours it occurred in 4% and 0%, respectively (p=0.153). These differences were not statistically significant. Similar observations were reported by Elhakim M et al.,21 who found no significant difference in antiemetic effect during the later postoperative period, and by Thomas R and Jones N.22 The requirement for rescue antiemetic was also lower with combination therapy. During 0–6 hours, rescue antiemetic was required in 18% of Group A compared with 4% of Group B (p=0.025). Similar findings were reported by Elhakim M et al.21 and D'souza N et al.,17 During 6–12 hours, rescue antiemetic was required in 8% versus 2% (p=0.362), while during both 12–18 hours and 18–24 hours, it was required in 2% of Group A and none of Group B. These differences were not statistically significant and were comparable with previous observations. The mean amount of rescue antiemetic required over 24 hours was significantly greater in Group A than Group B (16.8 ± 2.24 mg vs 13.3 ± 2.31 mg; p=0.027). This finding agrees with Gautam B et al.,23 who reported reduced rescue antiemetic requirement with ondansetron–dexamethasone combination therapy, and with Bhattarai B et al.,24 Overall, the addition of dexamethasone to ondansetron significantly reduced the incidence and severity of PONV, particularly during the first 12 postoperative hours, and reduced the requirement for rescue antiemetic. The antiemetic action of dexamethasone may be related to inhibition of prostaglandin synthesis, reduction in serotonin turnover and potentiation of other antiemetic agents.

Ondansetron in combination with dexamethasone is more effective in preventing postoperative nausea and vomiting, in patients undergoing elective total abdominal hysterectomy under general anesthesia. The need for rescue antiemetic in early postoperative period is reduced with combination of ondansetron and dexamethasone. The amount of rescue antiemetic needed is less with ondansetron/dexamethasone combination as compared to ondansetron alone in postoperative period. No significant adverse effects were noted in either of the groups with the use of ondansetron alone or in combination with dexamethasone.

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