Abstract

Many patients, especially those in certain "high risk " groups, undergo operative procedures under regional analgesia in the belief that this approach is safer than general anaesthesia; this is particularly the case for patients with coexistent lung disease. During the procedure, sedation is often provided with an i.v. agent, for example midazolam, diazepam or propofol. It seems (from personal observation) that administration of oxygen to the patient in this situation is not routine in current European practice. There is only equivocal guidance on this topic from reference works on local anaesthesia [1,2] and most do not mention the use of oxygen, except to treat the complications of regional anaesthesia [3-5]. We decided to study the effects of sedation with midazolam on oxygen saturation (5a0j) as meas-ured by pulse oximetry in patients undergoing surgery under regional conduction block. PATIENTS AND METHODS A study was planned of 100 patients aged 20-85 yr and in ASA categories I—III. Patients were randomly allocated to one of two groups according to the last digit of the hospital number: the first group (odd digit) received oxygen 2 litre min~l via a 12-French gauge nasal catheter (without foam nostril plug) during surgery, the second group (even digit) received no additional oxygen unless.SaOj decreased to less than 90%. All patients underwent surgery under regional conduction block in combination with sedation using incre-ments of midazolam 1.0-2.5 mg i.v. as required.