Entwicklung einer Erhebungsstrategie zur Erfassung von Übelkeit in der frühen postoperativen Phase

Postoperative nausea and vomiting is a serious compliant following general anaesthesia. In recent years, an incidence of about 20-30% is stated in different studies, whereat there is a large variance. Clinical studies are often hardly comparable regarding the measured incidence because there is no standardized assessment of PONV. Furthermore, the complex of problems when assessing nausea in the early postoperative period have barely been investigated. In the first two hours after the operation and anaesthesia, many patients suffer from drug accumulation and a large spectrum of different disorders. In this situation it is likely possible, that patients who are asked about acute nausea, unwittingly mistake their general displeasing condition for nausea and give unreliable information. The objective of this study was the development of a feasible instrument for assessing nausea in the early postoperative period and its particular circumstances. Therefore, this study compared a commonly used 100 mm visual analogue scale with a binary upstream question for the presence or absence of nausea in combination with a 10-point NRS. These instruments were compared in regard to clinical applicability and specificity. In addition it was investigated, if the mean age and sex of patients have an influence on the level of errors, and if the necessity of an antiemetic treatment in the early postoperative period is a feasible additional criterion for assured nausea. Three hundred and sixty five patients, undergoing various surgical procedures, were enrolled. They were randomly divided into two study-groups, and were questioned about their nausea three times in the early postoperative period. Depending on the study group, the questioning started with the combined instrument or the VAS, and rotated every time, so that each patient was questioned with every instrument at least once. 24 hours postoperatively, a retrospective questioning was conducted. This time, the “PONV Intensity scale” and the “Simplified postoperative impact scale” were used to validate the measuring instruments. Criteria were developed to form a positive- and a negative-group for assured nausea and patients were assigned to the groups 62 according to their statements in the retrospective questioning. It was shown that the combined instrument possessed a significantly higher specificity than the VAS at all measuring points according to the determined cut-off-value. In addition, the combination was easier to administer and understandable by the patients. Patients of the negative-group for assured nausea, who lay above the cut-off value on the VAS, were significantly older than the comparison group, and even older if they lay above the cut-off value twice. This confirms results from earlier studies. There was no influence of the sex on the level of errors. The necessity of an antiemetic treatment in the early postoperative period emerged as a feasible additional criterion for the determination of assured nausea. The affected patient suffered more from their nausea than patients without antiemetic treatment, and were mostly assigned to the preassigned positive-group. But it has to be mentioned that it can only be an additional criterion, because a large number of patients with assured nausea needed no treatment and would therefore be overlooked if it would be the sole criterion. In a second analysing of the data, the cut-off value for nausea in the measuring tools was raised. Under these conditions, the combined instrument and the VAS provided equally precise data. Therefore, it was reasoned that both instruments are able to differentiate between clinical relevant nausea and mild episodes. From the study on hand emanates, that the combined instrument in connection with the additional criterion of the necessity of antiemetic treatment is feasible as a standardized assessment tool for nausea in the early postoperative period. However, according to the study design, there was no possibility to evaluate the sensitivity of this tool. Therefore, there should be further investigations on this matter. For clinical studies, it is recommended to add a retrospective interview on nausea after six or 24 hours, because the combined instrument is not able to assess the complex phenomenon of nausea completely. It is rather mend as an assistance in a period, which is of great importance when assessing nausea, but were complex questionnaires are limited in use.