Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Ambulatory Anesthesia
Introduction: The effectiveness of transcutaneous electric nerve stimulation (TENS) at the P6 Neiguan point to prevent postoperative nausea and vomiting (PONV) is controversial . Middle ear surgery is associated with a high incidence of PONV . Therefore, we designed a study to compare the antiemetic efficacy of acupoint (P6) vs non-acupoint stimulation when administered perioperatively to outpatients undergoing middle ear surgery.
Methods: 54 consenting adult ASA I, II and III outpatients undergoing middle ear procedures were randomly assigned to one of two acustimulation groups, according to an IRB-approved, single-blind, placebo controlled protocol. All patients received TENS at a pulse repetition frequency of 8 Hz using a Reliefband[registered sign] (Maven Laboratories, Yuba City, CA) acustimulation device. In Group I, the stimulation device was applied at the P6 point located two inches proximal to the distal wrist crease on the anterior (palmar) surface of the forearm. In the control group (Group II), the device was applied to the dorsum of the wrist. The device was applied 30 min before induction of anesthesia and removed when the patient was ready for discharge from the day-surgery unit. All patients received a standardized general anesthetic consisting of midazolam (0.02 mg/kg), propofol (1.5 mg/kg), sufentanil (0.5 mg/kg), vecuronium (0.1 mg/kg), sevoflurane (1-2%) and nitrous oxide (N2 O), 50% in oxygen. At the end of the operation, all patients were administered ondansetron, 4 mg iv. Recovery times were determined from discontinuation of the volatile anesthetic to awakening, orientation and recovery room discharge. The incidence of PONV was evaluated during the first 24 hours after surgery. Data were analyzed using Student's t-test and Chi-square test with a p-value <0.05 considered statistically significant.
Results: The two groups were similar with respect to their demographic characteristics, anesthesia and surgery times, recovery profiles and postoperative analgesic requirements. There were no significant differences among groups with regard to PONV, requirements of postoperative antiemetic rescue medication, and unexpected overnight admissions to the hospital secondary to emetic symptoms (Table 1).
Conclusions: In outpatients undergoing middle ear surgery, P6 electrical stimulation provided by an acustimulation device failed to significantly decrease the incidence of PONV compared to stimulation at a non-acupoint.
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2. Br J Anaesth 1996; 76: 316-8