We would like to know the prophylactic anti-emetic effect of ramosetron compare to ondansetron in patient undergone total knee arthroplasty with spinal anesthesia and intrathecal morphine .

The patients were allocated into 2 groups by computerized block randomization according to a computer generated randomization. Treatment allocations were contained in sealed envelopes that were opened after patient enrollment. Patients received either 8 mg of intravenous (IV) ondansetron or 0.3 mg of IV ramosetron 10 minutes before spinal anesthesia and intrathecal morphine. All of the unilateral TKAs were done by one orthopedic surgeon using the same minimally invasive surgical technique and the same prosthesis.

Patients were monitored for incidence of Post Operative Nausea Vomiting(PONV) every 6 hours until 24 hours, and 24-48 hours postoperatively. Common adverse drug reactions associated with serotonin receptor antagonists (pruritus, dizziness, and headache) were also recorded.

The sample size calculation was based on the ability to detect a difference in incidence of postoperative nausea in between the two groups of 40% i.e. 50% in the ondansetron arm, and 30% in the ramosetron arm, consistent with a previous study. Using a power of 80% (β=0.2) and a two sided significance level(alpha) of 0.05, 45 patients in each group were required.

Inclusion Criteria:

• Patients aged 50-80 years with a diagnosis of primary OA undergoing unilateral TKA
• American Society of Anesthesiologist (ASA) physical status I-III
• Giving written informed consent

Exclusion Criteria:

• Body mass index (BMI) > 35 kg/m2
• Unable to undergo spinal anesthesia
• History of allergic to study drugs
• Impaired renal and/or hepatic function
• Use of systemic steroids and anti-emetics within 24 hours of operation