A systematic approach to the management of postoperative nausea and vomiting.

Postoperative nausea and vomiting (PONV), a common complication after anesthesia and surgery, often results in delayed discharge with the patient's unpleasant symptoms continuing at home. To effectively prevent and treat PONV, it is important to understand the factors implicated in PONV, the mechanisms of PONV, the pharmacology of the antiemetic agents, and the nonpharmacologic measures that have been shown to be effective. The cause of PONV is likely to be multifactorial, with important predictors being female gender, history of PONV, and history of motion sickness. The vomiting center can be triggered by activation of dopamine, serotonin (type 3), histamine (type 1), and muscarinic cholingergic receptors in the chemoreceptor trigger zone and the nucleus tractus solitarus, as well as acetylcholine receptors in the vestibular apparatus, vagal afferents from the periphery, and the endocrine environment. Antiemetic agents such as the serotonin antagonists (eg, ondansetron, dolasetron), droperidol, antihistamines (eg, diphenhydramine, dimenhydrinate), and promethazine can prevent and treat PONV effectively. Transdermal scopolamine and dexamethasone have a role in the prevention of PONV, particularly for certain high-risk patients. Nonpharmacologic measures and alternative treatments such as hydration, maintaining blood pressure, acupressure techniques, trancutaneous acupoint stimulation, and isopropyl alcohol must not be overlooked. Finally, an evidence-based algorithm for the prevention and treatment of PONV in adults is presented.

Allergic reactions to drugs: implications for perioperative care.

Clinically, one must be able to differentiate between an allergic reaction and an adverse reaction. Clinical manifestations of allergic reactions range from urticaria and rash to bronchoconstriction, laryngeal edema, hematologic disorders, and other serious reactions. Many drugs administered in the perioperative setting can cause allergic reactions. Antibiotics such as penicillins, beta-lactam antibiotics, and sulfonamides are the most common class of drugs that produce allergic reactions. A detailed allergy history is important when deciding if a patient can receive a drug that may cross-react (eg, a cephalosporin in a patient with a penicillin allergy). Vancomycin can cause a reaction that ranges from erythema and pruritus to clinically significant hypotension. Proper dilution and rate of administration are essential in minimizing the histamine from vancomycin that is thought to produce this reaction. "Sulfa allergy" describes an allergy to sulfonamide antibiotics; a patient with a "sulfa allergy" is not allergic to drugs containing sulfur, sulfites, or sulfates. Although true allergic reactions to opioids are rare, naturally occurring compounds like morphine and codeine can cause allergic reactions. After stopping the offending drug, mild allergic reactions can be managed with diphenhydramine, with or without a steroid. Significant allergic reactions require more aggressive management with oxygen, intravenous fluids, epinephrine, and histamine blockers.