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Delirium is a disturbance of consciousness, with an acute onset, a fluctuating course and is accompanied by inattention and disorganized thinking [1]. It occurs in 5-15% of postsurgical patients, although certain high-risk groups, such as hip fracture patients, have rates of up to 60% [2]. Delirium is a significant contributor to longer hospitalizations, higher costs, prolonged cognitive impairment and even mortality [3-7]. Unfortunately, the causes of delirium are multi-factorial (Table 1), with risk factors specific to the host and to critical illness. However, iatrogenic risk factors exist and are potentially modifiable targets [2,8-10].
Methods & results
The double-blind randomized trial by Sieber et al. evaluating the role of sedation during spinal anesthesia on delirium rates [11], adds to a growing body of literature regarding this brain organ dysfunction and interventions that may help reduce its incidence. The authors included elderly patients (≥65 years) undergoing surgical repair of hip fractures under a spinal anesthetic. Exclusion criteria were severe preoperative cognitive impairment (Mini-Mental State Examination [MMSE] <15] or preoperative delirium as determined by the Confusion Assessment Method (CAM), contraindications to spinal anesthesia, prior hip surgery, congestive heart failure (New York Heart Association [NYHA] class IV), severe chronic obstructive pulmonary disease and mental or language barriers that would make assessment for delirium difficult. Patients were randomized to receive either light levels of sedation using propofol or midazolam, or deep levels of sedation with propofol infusions. Randomization was carried out using permuted blocks and stratified for age and preoperative cognitive impairment. A Bispectral Index (BIS) monitor was used to achieve separation of the groups with a BIS level of less than 50 targeted for the deep sedation group and greater than 80 in the light sedation group. More sedatives were administered to the light sedation group only if clinically indicated during surgery. All patients received oxygen by nonrebreather and hypotension (as defined by study protocol) was treated aggressively with fluid and vasopressors. Postoperatively, patients were managed in either the postanesthesia care unit or intensive care unit (ICU) at the discretion of the physicians. Postoperative analgesic management was standardized to intravenous bolus dosing of hydromorphone, and patient-controlled analgesia morphine for those patients deemed competent enough to use them. On the second postoperative day, delirium was assessed using CAM and...