The Efficacy of P6 Acupressure in Reducing Postoperative Nausea and Vomiting in Patients Undergoing Craniotomy

The primary aim of this study is to investigate if P6 acupressure can reduce postoperative nausea after craniotomy. Calculation of sample size was based on the assumptions to detect at difference of 20% between the patients (38% in the control group vs 18% in the acupressure group) for the primary endpoint; incidence of nausea during the first 24 hours postoperatively, with a significance level 5% and a power of 80%, guided by an earlier study with a similar population (Wang et. al. 2010) and the assumption that 38% of our patients suffer from nausea. These assumptions suggested a sample size of 78 patients (39 patients / group) that resulted in a sample size of 80 patients for covering attrition. Secondary aims are to investigate if the frequency of vomiting and the need for antiemetic can be reduced with P6 acupressure.

Patients are randomly assigned into one of two treatment groups using a computer-generated random number table, either P6 acupressure group or placebo group. Randomization and sealing of the study envelopes, containing all study material and following the patients all through the study, are performed by persons from the research department, who is not involved in the data collection. Information and study protocol are included in the envelope. The randomization is taking place preoperatively. Sea-Band®, a single-sized elastic acupressure band with a plastic button placed at P6 to apply pressure is used. One group will receive an active acupressure band and the other an identical placebo band without any button. Before entering the operation ward both wrists are marked at the place for P6, performed by staff at the neurosurgical ward. The active acupressure bands and the placebo bands are administered at the end of surgery. They are placed unilaterally at the wrist by the nurse anesthetist who performs the patient's anesthesia. The manufacturer's guidelines of where and how to place the band are included in the envelope with study material. Both the P6 acupressure bands and the placebo bands are covered with a bandage to ensure blinding to the patients and the nursing staff involved in the postoperative care. Both the P6 acupressure bands and the placebo bands will be removed 48 hours postoperatively. If the bands cause discomfort, they can be removed for 30 minutes every two hours, performed by staff not involved in the postoperative care, with instructions to cover the wrist with a cotton roll while airing the arm, this for ensuring further blinding if the acupressure has caused any betrayal marks.

At the end of the surgery all patients receive ondansetron 4mg IV. Droperidol IV is administered as additional perioperative antiemetic if considered necessary. Postoperatively rescue antiemetics are administrated according to current routines. The administered drugs are 0,625-1,25mg droperidol and 1-4mg ondansetron, either alone or in combination. Postoperative opioid administration (morphine and ketobemidone) are also recorded during the time of the study

Before operation all patients are filling in a health declare formula as a routine in the anesthetic preparation. This formula includes the four risk factors for PONV, according to Apfel and colleagues (Apfel et al. 1999). To clarify earlier PONV there is a specific question about this issue on the formula of written consent.

During 48 hours postoperatively the patients are evaluating their nausea which is registered on the same formula as the frequencies of vomiting. The first evaluation is taking part when arriving to the postoperative care unit and then every hour for the first six hours, every third hour until hour 24 and thereafter every sixth hour from hour 25-48. A Numerical Rating Scale (NRS) from 0-10 is used, where 0 mean no nausea at all and 10 the worst nausea possible. The patients are asked about whether they have experienced any nausea within the previous period of time. Assessment of nausea and registration of the vomiting frequency are performed by staff unaware of the patient's group in the postoperative care unit/neurosurgical ward and by the patients themselves when possible.

After discharge the data from the NRS formula are collected. The patients' journals are screened for administrated antiemetic and opioids, for potential risk factors for PONV and for other demographics relevant to the study outcome. All data are saved anonymously in the software Statistical Package for Social Sciences (SPSS).

Overall PONV is defined as at least one episode of nausea or vomiting during the observation time of 48 h. Rescue therapy is defined as at least one dosage of either droperidol or ondansetron during the observation time of 48 h. Early PONV is defined as PONV occurring up to 6 hours postoperatively and late PONV 7-48 hours postoperatively.