FENTANYL ANn DROPFRIDOL, adrainistered either separately or combined in a fixed ratio of 1:50 as "Innovar," have been recommended as adjuncts to local anaesthesia for a wide variety of procedures. 1~ These have included diagnostic procedures, such as cerebral angiography a.~ on neurosurgieal patients, despite the well documented respiratory depression 6,7 associated with "Innovar" and fentanil. Whereas the effects of meperidine s and morphine ' on the cerebrospinal fluid (c.s.f.) pressure of conscious neurosurgical patients breathing air have long been known, the effects of fentanyl have received little attention when used in these circumstances, although they have been studied extensively in nomaocarbid ~ or hypocarbic 11 anaesthetized patients. It has been assumed that small doses of "Innovar" or fentanyl had little effect on the intracranial pressure of neurosurgical patients, with or without space occupying lesions, provided that the intracranial pressure was not elevated. 12 We have administered "Innovar" prior to induction of anaesthesia to patients about to undergo craniotomy, to facilitate the insertion of intra-arterial and central venous lines and to produce tranquil patients. This study was prompted by a chance observation on a patient with established lumbar spinal drainage to control intractable raised intra-cranial pressure following a subaractmoid haemorrhage. Administration of "Innovar" resulted in a dramatic rise of e.s.f, pressure. The purpose of this study was to investigate the effects of "Innovar", fentanyl and droperidol on the c.s.f, pressure of neurosurgical patients being prepared for craniotomy and so to evaluate the suitability of these agents for neuroradiological procedures performed without general anaesthesia. Twenty-five adult patients about to undergo craniotomy for tumour or aneurysm were studied. Patients with clinical features suggestive of raised intracranial pressure were excluded as were those with a history of a previous craniotomy or an operation on the spine. All patients were premedicated with quinalbarbitone 100 mg and atropine 0.4 mg one hour preoperatively. E.C.G. leads were attached, intraarterial and intravenous lines set up and the patient turned into the left lateral position with the head and spine horizontal. An 18-gauge malleable needle was then inserted into the lumbar subdural space and connected to a water manometer, care being taken to avoid any loss of fluid. After the c.s.f, pressure had stabilized the lowest level of the oscillating column relative to the level of dural puncture was noted. The mean blood pressure was also recorded and arterial blood was withdrawn for blood gas analysis. Eleven patients (Group I) were then given 2 ml of "Innovar" (droperidol 5 nag and fentanyl 0.1 mg) intra
