Post-operative nausea and vomiting (PONV) remain one of the most frequent and burdensome complications after surgery, with a reported incidence of 20% - 80% depending on patient susceptibility, the surgical procedure and, critically, the anesthetic technique used [1] - [4] . Beyond discomfort, PONV may prolong hospital stays, raise costs, and jeopardise patient satisfaction; in severe cases it can precipitate wound dehiscence, delayed mobilisation and bronchial aspiration with potentially serious respiratory sequelae [2] [5] .

Rationale for dexamethasone: Although several anti-emetics are available (ondansetron, droperidol, metoclopramide, neurokinin-1 antagonists), dexamethasone is widely recommended as first-line prophylaxis because it is inexpensive, has a long duration of action (6 - 10 h), and is usually administered as a single intra-operative dose (4 - 8 mg) with a favourable safety profile [6] - [8] . Meta-analyses have shown that dexamethasone reduces the relative risk of early and late PONV by ≈40% without increasing postoperative bleeding or infection [6] [9] . However, its effectiveness may vary when combined with different anesthetic agents, especially volatile anesthetics (e.g. halothane, isoflurane) and potent opioids (e.g. fentanyl), which themselves are potent emetogens [3] [10] . Clarifying these interactions is clinically relevant in settings where resource constraints dictate judicious drug selection.

Research gap and hypothesis: Current guidelines recommend multimodal pro-phylaxis tailored to individual risk, yet data directly comparing the impact of dexamethasone across distinct anesthetic regimens are scarce [5] [11] . We therefore posed the following research question:

Does intra-operative dexamethasone prophylaxis confer the same reduction in PONV when used with intravenous agents (propofol, thiopental, ketamine) as when used with volatile anesthetics (isoflurane)?

We hypothesised that (H₀) dexamethasone would reduce the incidence of PONV regardless of the anesthetic agent employed, and (H₁) that the magnitude of this reduction would be greater in patients receiving total intravenous anesthesia (TIVA) than in those exposed to volatile agents.

Objective: To test this hypothesis, our study analysed the association between the choice of anesthetic agent, adjunctive dexamethasone prophylaxis, and the occurrence of PONV in adult surgical patients.

The present study shows that dexamethasone-based anti-emetic prophylaxis (DAP) is associated with a marked reduction in postoperative nausea and vomiting (PONV) during the first 48 hours after surgery, with a PONV rate of 13% in the dexamethasone group versus 35.2% in the control group [8] .

This efficacy can be explained by several physiological mechanisms. Dexamethasone modulates the release of pro-inflammatory cytokines and dampens the inflammatory response that triggers nausea reflexes [11] [12] . It also exerts an anti-edematous effect on neurons within the vomiting center, preventing excessive activation of vagal and sympathetic afferent pathways [7] , and may stabilize the blood-brain barrier, reducing its permeability to circulating emetogenic substances [8] . Together, these actions account for dexamethasone’s central role—often alongside 5-HT₃ antagonists—in multimodal PONV-prevention protocols [9] .

Analysis of the an aesthetic regimen revealed a significant association between PONV and the use of fentanyl and halothane. Opioids with high µ-receptor affinity, such as fentanyl, stimulate the chemoreceptor trigger zone and potentiate the vomiting center, increasing the likelihood of PONV, especially at high cumulative doses or without prophylaxis [1] [9] . Halothane, a highly blood-soluble volatile agent, persists after discontinuation and can irritate the respiratory mucosa and impair gastrointestinal motility, further elevating PONV risk [13] [14] . Although its use has declined in favor of more modern agents, halothane remains common in resource-constrained settings for economic reasons.

By contrast, no significant association was found with thiopental, propofol, ketamine or isoflurane, findings consistent with previous work [6] . Propofol possesses intrinsic anti-emetic properties attributed to inhibition of serotonin release in the gut and reduced excitability of the chemoreceptor trigger zone [9] . Thiopental primarily acts on GABAergic pathways and does not markedly influence emetic circuits [15] . Ketamine, when used at low induction or analgesic doses, rarely increases PONV, and isoflurane has a more favorable elimination profile and less impact on gastrointestinal motility than halothane [6] [7] .

Optimal PONV prevention therefore requires combining pharmacological prophylaxis with dexamethasone (and, when indicated, 5-HT₃ antagonists), careful selection of an aesthetic agents to limit highly emetogenic opioids or volatile agents, and systematic consideration of individual risk factors such as female sex, prior PONV and surgical type [7] .

The study’s limitations include a small sample size and short inclusion period, which may reduce statistical power to detect additional associations. Real-world anesthesia is inherently multimodal, complicating isolation of individual drug effects, and unmeasured confounders such as patient comorbidities, provider experience and surgical duration can influence outcomes [11] [13] . Larger prospective, randomized trials with longer follow-up and detailed patient-centered assessments are warranted [9] .

Our findings confirm the pivotal role of dexamethasone prophylaxis in reducing PONV and highlight the importance of selecting less emetogenic anesthetic agents, particularly avoiding halothane when possible and minimizing opioid exposure. Implementing these strategies can enhance postoperative comfort and overall quality of care in contemporary anesthetic practice.

We extend our thanks to all the patients who voluntarily agreed to participate in the study.

Ethical approval was obtained from the Ethics Committee of the University of Douala, Cameroon (No. 2337 CEI_UDo/02/2024/T) and authorized by the management of Laquintinie Hospital in Douala (No. 487/AR/MINSANTE/DHL).

All participants provided informed consent before their inclusion in the study. The consent process ensured that participants fully understood the purpose of the research, their role in the study, and their rights, including the right to withdraw at any time without any negative consequences.

The privacy and confidentiality of all participants were safeguarded throughout the study. Data were anonymized to ensure that no participant could be identified.

The data used in this study can be made available upon request by the reviewers.

NPC, AL, conceptualised the study, designed the experimental approach, and developed the writing plan. NPC, MBJ and ZMJ were responsible for participant recruitment and laboratory analyses. Statistical analysis was performed by, NPC and NTF. NPC, drafted the initial manuscript, while ZMJ and BF critically reviewed and revised it. All authors made substantial, direct, and intellectual contributions to the work and approved the final version of the manuscript for publication.

During the preparation of this work, the author used ChatGPT to translate the manuscript into English. After using this tool/service, the author reviewed and edited the content as needed and takes full responsibility for the content of the published article.