During the ethanol sclerotherapy procedure, the investigators will record doses of and time of ethanol injections and record ethanol concentrations in endtidal breath every 5 minutes. Furthermore after every ethanol injection the concentration will be measured every minute for 5 minutes. To do so, the investigators will attach a breath alcohol testing device to the expiratory carbon dioxide measuring unit. Since this is the new standard of the university hospital Berne all patients undergo the same procedure. There is no study specific intervention. In this study the investigators will only document the breath alcohol levels, doses and timing of ethanol injections. All other data will be obtained from the anesthesia information system. During the two months of the study, the investigators will also record endtidal ethanol concentration after anesthesia in the postoperative care unit discharge from the unit.