MedWire News: Using light rather than deep propofol sedation in elderly patients undergoing spinal anesthesia could halve the rate of postoperative delirium, research suggests.
A total of 114 patients scheduled for hip fracture repair participated in the double-blind, randomized, controlled trial, the results of which appear in the Mayo Clinic Proceedings. The patients were at least 65 years old and were free of delirium or severe dementia prior to surgery.
Frederick Sieber (Johns Hopkins Medical Institutions, Baltimore, Maryland, USA) and co-workers assigned the patients to receive deep or light propofol sedation, defined as a bispectral index of about 50 or at least 80, respectively.
The team used the Confusion Assessment Method (CAM) and the Mini-Mental State Examination (MMSE) to gauge delirium in the patients on the second day after surgery, and the CAM to monitor them daily from the third day until discharge.
This strategy detected delirium in 40% of the deep sedation group but just 19% of the light sedation group. The corresponding rates were 44% versus 14% of patients with some pre-operative cognitive impairment (MMSE≥20), and 39% versus 11% of those without cognitive impairment (MMSE≥24).
After accounting for confounders, delirium risk was raised 2.69 fold by deep versus light sedation, 3.97 fold by pre-operative dementia, and 1.62 fold per unit of packed erythrocytes transfused. Among patients not already delirious on admission to intensive care, admission signaled a 3.69-fold increase in delirium risk.
Sieber and colleagues calculate that the number needed to treat to prevent one case of postoperative delirium is 4.7 overall and 3.5 for patients without baseline cognitive impairment.
In a related editorial, Gregory Crosby (Brigham and Women’s Hospital, Boston, Massachusetts, USA) and colleagues said that if the findings of Sieber et al are borne out, “the implications are enormous, because procedural sedation is widespread and controlling depth of sedation might be a simple, inexpensive way to reduce the incidence of this cognitive morbidity.”
The editorialists pointed out several caveats, including that the light sedation group appeared more functionally and cognitively active before surgery. However, they agreed that “in elderly patients it is time to move beyond the focus on cardiopulmonary risk alone and add cognitive risk to the equation.”
They concluded: “After all, the brain is the main target of sedative agents, and increasingly the brain that is being targeted is old and frail. Under those conditions, even sedation may have undesirable cognitive consequences.”
