You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

[ Complaints in the postoperative phase related to anesthetics ] . In two prospective , randomized studies the frequency of headache , nausea , vomiting , and analgesic requirement during the first postoperative 24 h was observed in order to study differences between the sexes and the inhalation anesthetics halothane , enflurane , isoflurane , or balanced anesthesia with enflurane/alfentanil . Nausea and vomiting were more frequent after enflurane than after halothane or isoflurane . There was no significant difference between anesthetics and frequency of headache , but there were significant differences in postoperative analgesic requirements which were highest after halothane and lowest after isoflurane . Postoperative complaints were always significantly greater among women than among men . The second study indicated that balanced anesthesia did not reduce the analgesic requirement compared to enflurane without alfentanil , but lead to a higher incidence of vomiting . After premedication with flunitrazepam and atropine and combined with 70 % N2O/30 % O2 , isoflurane was the most favorable anesthetic agent with regard to the parameters studied . Balanced anesthesia with enflurane/alfentanil did not show any advantages for patients in the postoperative phase under the given conditions .
{"Intervention": ["anesthetics halothane", "alfentanil", "halothane", "enflurane", "balanced anesthesia with enflurane/alfentanil", "Balanced anesthesia with enflurane/alfentanil", "isoflurane"], "Outcome": ["frequency of headache", "Nausea and vomiting", "vomiting", "Postoperative complaints", "frequency of headache , nausea , vomiting , and analgesic requirement", "postoperative analgesic requirements", "analgesic requirement"], "Participant": ["women", "men", "anesthetics", "postoperative phase"]}