Caffeine for the prevention of postoperative nausea and vomiting - Few comments.

Sir,

We found the article “caffeine for the prevention of postoperative nausea and vomiting (PONV)”[1] by Steinbrook et al. interesting as well as pleasing because of authors’ humility to report a finding which may not fit into popular belief (read: Increased incidence of PONV after intravenous caffeine). Not to take away the credit from authors but as critics, we would like to raise few comments, which we consider relevant.

The readers would benefit if authors could clearly state whether the type of surgeries considered as surgical risk factors for PONV were included in the study, e.g., laparoscopy, laparotomy, maxillofacial surgeries etc.[2] Authors have rightly chosen propofol as an induction agent and administered routine as well as additional antiemetic prophylaxis for patients at high risk for PONV. In fact, patients with two of the four risk factors for PONV as per Apfel score were included in the study. Additional strategies to reduce baseline risk — use of propofol for maintenance of anesthesia, avoidance of nitrous oxide, avoidance of volatile anesthetics,[3] use of nonsteroidal antiinflammatory drugs[4] to spare opioids, etc., as suggested in the “Society for Ambulatory Anesthesia Guidelines for the Management of PONV” — If adopted, would probably influence the outcome. In addition, the emetogenic effect of inhaled anesthetics appears to be dose related.[3] Hence, a comment regarding comparability of volatile anesthetic consumption between the groups would be relevant. Lastly, a comment about intraoperative hydration would be apt as it has been found to have a bearing on PONV.[5]