Midazolam Adjunct Therapy for Prevention of PONV in Gynecological Laparoscopy (MIDOD)

Postoperative nausea and vomiting (PONV) is one of the most frequent and distressing complications following general anesthesia, particularly in patients undergoing laparoscopic and gynecological surgical procedures. Despite advances in anesthetic techniques and routine use of prophylactic antiemetic agents, PONV continues to affect a significant proportion of surgical patients. It is associated with considerable discomfort, delayed recovery, prolonged post-anesthesia care unit (PACU) stay, increased healthcare utilization, risk of dehydration and electrolyte imbalance, and in severe cases may lead to aspiration, wound complications, or disruption of surgical repair. The multifactorial nature of PONV involves patient-related, anesthetic-related, and surgical factors. Female gender, non-smoking status, use of volatile anesthetics, perioperative opioid administration, and laparoscopic procedures are well-established risk factors, making gynecological laparoscopic surgery one of the highest-risk categories for PONV.

Even though dual prophylaxis using dexamethasone and ondansetron has become a widely accepted standard regimen due to their complementary mechanisms of action, complete prevention of PONV is still not achieved in a substantial subset of patients. Dexamethasone exerts its antiemetic effect through anti-inflammatory action and possible central inhibition of prostaglandin synthesis, while ondansetron acts as a selective 5-HT3 receptor antagonist blocking serotonin-mediated emetogenic pathways in both the central nervous system and gastrointestinal tract. However, because PONV is mediated through multiple overlapping pathways including dopaminergic, histaminergic, cholinergic, and neurokinin systems, targeting only two pathways may not provide sufficient protection in high-risk individuals.

This limitation has led to increasing interest in multimodal antiemetic strategies incorporating drugs with different pharmacological mechanisms. Midazolam, a short-acting benzodiazepine, is primarily used for anxiolysis, sedation, and induction of anesthesia through potentiation of gamma-aminobutyric acid (GABA) receptors in the central nervous system. In addition to its sedative properties, emerging evidence suggests that midazolam may possess antiemetic effects. The proposed mechanisms include reduction of preoperative anxiety, modulation of central dopaminergic pathways, inhibition of cortical and vestibular input to the vomiting center, and attenuation of the emotional component of nausea perception. Some studies also suggest that benzodiazepines may reduce dopamine release in the chemoreceptor trigger zone, thereby contributing to antiemetic action. However, clinical evidence remains inconsistent, with some trials demonstrating significant reductions in PONV incidence and others showing only marginal or statistically non-significant effects.

Given these conflicting findings, the present randomized controlled trial was designed to evaluate whether adding midazolam to standard dual prophylaxis with dexamethasone and ondansetron provides superior protection against postoperative nausea and vomiting in patients undergoing elective gynecological laparoscopic surgery. The study was conducted at the Department of Anesthesiology, Hameed Latif Hospital, Lahore, over a period of six months from 02-12-2025 to 01-06-2026 after obtaining ethical approval from the institutional ethics committee.

A total of 300 female patients aged between 19 and 65 years with American Society of Anesthesiologists (ASA) physical status I and II scheduled for elective gynecological laparoscopic procedures were enrolled in the study after obtaining written informed consent. Patients with significant comorbidities that could influence PONV assessment or drug metabolism were excluded. Exclusion criteria included a history of chemotherapy, chronic opioid use, recent antiemetic administration within 24 hours, known allergy to study drugs, hepatic dysfunction defined as liver enzymes greater than twice the normal upper limit, renal impairment with serum creatinine greater than 1.6 mg/dl, pregnancy or lactation, conversion to laparotomy during surgery, BMI greater than 35 kg/m², QTc prolongation above 450 ms, alcohol or substance abuse, and inability to reliably assess postoperative nausea and vomiting.

The sample size of 300 patients (150 in each group) was calculated using 80% statistical power and a 95% confidence interval, assuming an expected efficacy rate of 65% in the control group and 78% in the intervention group based on previously published literature. This ensured adequate power to detect a clinically meaningful difference between groups.

Randomization was performed using a computer-generated random number sequence in a 1:1 allocation ratio. Allocation concealment was ensured using sealed opaque envelopes that were opened just before drug administration. Patients were assigned to either Group A or Group B accordingly. Group A received standard dual prophylaxis consisting of dexamethasone (0.1 mg/kg intravenously after induction of anesthesia) and ondansetron (0.1 mg/kg intravenously at the end of surgery) along with normal saline placebo administered after preoxygenation. Group B received the same dual prophylaxis with the addition of intravenous midazolam at a dose of 0.05 mg/kg administered after preoxygenation and prior to induction of anesthesia. Identical syringes were used for midazolam and placebo to ensure blinding of both patients and outcome assessors. Drug preparation and administration were performed by an anesthesiologist not involved in data collection or postoperative assessment.

All patients received a standardized general anesthesia protocol to minimize confounding variables. Preoxygenation was performed for three minutes prior to induction. Anesthesia was induced with intravenous propofol at 2 mg/kg, fentanyl at 1 µg/kg, and atracurium at 0.5 mg/kg to facilitate tracheal intubation. Following intubation, anesthesia was maintained using isoflurane in a mixture of oxygen and air (approximately 40% oxygen). Mechanical ventilation was adjusted to maintain end-tidal carbon dioxide between 35 and 40 mmHg throughout the procedure. Hemodynamic parameters were monitored continuously, and anesthetic depth was adjusted as required. Neuromuscular blockade was reversed at the end of surgery using pyridostigmine and glycopyrrolate in appropriate doses. Patients were extubated once standard recovery criteria were met and then transferred to the post-anesthesia care unit for monitoring.

Postoperative management was standardized for all patients. Pain management protocols were kept consistent to avoid confounding effects of analgesics on nausea and vomiting. Patients were observed in PACU and later transferred to the ward once they achieved a modified Aldrete score indicating adequate recovery. No additional sedative or antiemetic medications were given unless required as rescue therapy according to protocol.

Postoperative nausea and vomiting was assessed using an 11-point visual numeric rating scale (VNRS), where 0 represented no nausea and 10 represented the worst possible nausea. Scores were categorized as mild (1-3), moderate (4-6), and severe (7-10). A VNRS score of 4 or more was considered clinically significant PONV. Assessments were conducted at predefined time intervals: immediately in the post-anesthesia care unit (0 hours), at 6 hours, 12 hours, and 24 hours postoperatively. The highest VNRS score recorded during each time period was used for statistical analysis. Vomiting episodes and retching were also recorded separately. Rescue antiemetic therapy was administered according to protocol, including metoclopramide 10 mg intravenously as first-line rescue treatment, and chlorpheniramine 4 mg intravenously as second-line therapy if symptoms persisted or recurred.

Data were entered and analyzed using SPSS version 26.0. Continuous variables were expressed as mean ± standard deviation, while categorical variables were presented as frequencies and percentages. Normality of continuous data such as age and body mass index was assessed using the Shapiro-Wilk test, which confirmed that the data were normally distributed. Independent sample t-test was applied for continuous variables, while Chi-square test or Fisher's exact test was used for comparison of categorical variables. A p-value of less than or equal to 0.05 was considered statistically significant. Stratified analysis was performed to control for potential confounders including age groups, body mass index categories, ASA physical status, and type of surgical procedure.