We aimed to study the relationship between the anaesthetic manoeuvres and the appearance of Cerebral salt wasting syndrome (CSWS) in neurosurgical patients. One hundred and twenty-one consecutive craniotomies were studied, excluding those related to the hypothalamus, IIIrd ventricle and pituitary and those with kidney troubles. Factors studied: fluid intake, diuresis, intracranial hypertension, corticoids, furosemide, mannitol, hypnotic agents, opioids, anaesthetic gases, duration of surgery, and time to extubation. Thirty-two cases (6,14%) of CSWS were seen. Its appearance was related only to opioid administration. Thirty of the cases had received fentanyl > 0125 mg plus morphine > 5 mg and the other two fentanyl 0,20 mg plus morphine 5 mg. None of the 93 patients managed with fentanyl < 0,15 mg and no morphine at all developed CSWS. Conclusion: The administration of medium/large doses of opioids (fentanyl > 0,25 mg and morphine > 5 mg) during brain surgery seems to somehow predispose to CSWS.
