A hypothesis has been developed by the team that a drug called acetazolamide may be of use when these scenarios are encountered. Acetazolamide (carbonic anhydrase inhibitor) is a conventional diuretic but is also a drug used by travellers to counteract mountain sickness and one of its effects is to reduce CSF production. A low-dose (250mg orally) of the drug has been shown to be effective as a prophylaxis method in acute mountain sickness 3. Its oral form has also been utilised to reduce shunt CSF volume in children4. Additionally, Acetazolamide has been suggested as a 'first-line treatment' in Idiopathic intracranial hypertension 9, 10. To date, we have used this drug intravenously in 7 thoracic-abdominal patients, off licence, and had encouraging results (SEE APPENDIX 1) with a reduction of intracranial pressure (ICP) in some but not all patients. At the moment however, this drug is only licenced (approved by the Medicines and Healthcare products Regulatory Agency (MHRA)) for use in glaucoma, epileptic patients and patients with abnormal fluid retention. We hypothesize that the use of acetazolamide post operatively, in the 5 scenarios just described, results in the reduction of CSF production and hence ICP. Following from this we believe there was a reduced need for vasopressors and improved spinal cord blood perfusion. Undoubtedly in some patients this drug has a dramatic effect on CSF production, ICP and the need for drainage and vasopressors, all potential beneficial consequences. We do not know however whether the drug works in all patients and whether there are consequences from the other effects of this drug such as acidosis, hypercapnia or diuresis. In addition, we do not know whether the drug is best given preoperatively, as a prophylactic measure, or whether the preoperative treatment will improve the response to the intravenous postoperative dose. In addition, we do not know whether these measures which intuitively should lower the risk of paraplegia, actually translate into a lowering of this complication.