Entonox as a sedative for bone marrow aspiration and biopsy

Bone marrow aspiration and biopsy can be a painful procedure. Sedation techniques may make this investigation more acceptable to patients, but have the potential to cause life-threatening complications, as well as requiring additional staff and equipment for safe administration. We assessed the use of Entonox, a 50 : 50 mix of nitrous oxide and oxygen, as a sedation and analgesic agent, and compared it to previous experience with the intravenous (i.v.) benzodiazepine midazolam. Patients' perception of pain, and both the operator and patient's views on the ease of the procedure and safety factors were recorded. Twenty-two patients who had previously required i.v. midazolam sedation (16), or who requested sedation (6) were studied. Fifteen of 16 (94%) found Entonox better or equal to midazolam, and only one patient (6%) found it worse. There were no serious adverse events due to Entonox. We have shown, in this small group of patients, that Entonox is an effective, safe alternative to intravenous midazolam for sedation during bone marrow biopsy, and is considered acceptable by both patients and staff. It has the major advantage that no additional staff or facilities are required for safe administration or monitoring the patient during or after the procedure.