Low-dose haloperidol is known to be effective for the treatment of postoperative nausea and vomiting (PONV). However, precise dose-response studies have not been completed, especially in patients at high risk for PONV who require combination therapy. This study sought to identify the optimal dose of haloperidol that could be combined with dexamethasone without adverse effects in high-risk PONV patients receiving intravenous patient-controlled anesthesia (IV PCA) after gynecological laparoscopic surgery.

Female adults with three established PONV risk factors based on Apfel's score were randomised into one of three study groups. At the end of anaesthesia, groups H0, H1, and H2 were given intravenous (IV) saline, haloperidol 1 mg, and haloperidol 2 mg, respectively. All patients were given dexamethasone during the induction of anaesthesia. The overall early (0-2 h) and late (2-24 h) incidences of nausea, vomiting, rescue anti-emetic administration, pain, and adverse effects (cardiac arrhythmias and extrapyramidal effects) were assessed postoperatively. The sedation score was recorded in the postanaesthesia care unit (PACU).

Inclusion Criteria:

• ASA physical status I or II women
• Aged 20 65 years, and scheduled for gynecologic laparoscopic surgery and IV patient-controlled analgesia (PCA) for postoperative pain control.

Exclusion Criteria:

• Known allergy or intolerance to the study drug
• History of cardiac arrhythmia
• Psychiatric illness
• Chronic treatment with a dopamine antagonist
• Use of opioids or steroids within one week of surgery
• Use of antiemetic within 24 hours before the study
• No ability to use the PCA device
• Gastrointestinal, renal, or hepatic disease
• Insulin-dependent diabetes or obesity with a body mass index > 35 kg/m2.