Spinal Anesthesia with Targeted Sedation based on Bispectral Index Values Compared with General Anesthesia with Masked Bispectral Index Values to Reduce Delirium: The SHARP Randomized Controlled Trial

Abstract

Background: Reducing depth of anesthesia and anesthetic exposure may help prevent delirium, but trials have been conflicting. Most studies were conducted under general anesthesia or in cognitively impaired patients. It is unclear whether reducing depth of anesthesia beyond levels consistent with general anesthesia reduces delirium in cognitively intact patients. The authors' objective was to determine whether a bundled approach to reduce anesthetic agent exposure as determined by Bispectral Index (BIS) values (spinal anesthesia with targeted sedation based on BIS values) compared with general anesthesia (masked BIS) reduces delirium.

Methods: Important eligibility criteria for this parallel-arm randomized trial were patients 65 yr or greater undergoing lumbar spine fusion. The intervention group received spinal anesthesia with targeted sedation to BIS greater than 60 to 70. The control group received general anesthesia (masked BIS). The primary outcome was delirium using the Confusion Assessment Method daily through postoperative day 3, with blinded assessment.

Results: The median age of 217 patients in the analysis was 72 (interquartile range, 69 to 77). The median BIS value in the spinal anesthesia with targeted sedation based on BIS values group was 62 (interquartile range, 53 to 70) and in the general anesthesia with masked BIS values group was 45 (interquartile range, 41 to 50; P < 0.001). Incident delirium was not different in the spinal anesthesia with targeted sedation based on BIS values group (25.2% [28 of 111] vs. the general anesthesia with masked BIS values group (18.9% [20 of 106]; P = 0.259; relative risk, 1.22 [95% CI, 0.85 to 1.76]). In prespecified subgroup analyses, the effect of anesthetic strategy differed according to the Mini-Mental State Examination, but not the Charlson Comorbidity Index or age. Two strokes occurred among patients receiving spinal anesthesia and one death among patients receiving general anesthesia.

Conclusions: Spinal anesthesia with targeted sedation based on BIS values compared with general anesthesia with masked BIS values did not reduce delirium after lumbar fusion.

Figure 1

Consort Diagram A patient flow diagram is shown.

Figure 2

Subgroup Analyses of the Primary Outcome of Incident Delirium Subgroup analyses based on intention to treat analyses with the primary outcome of incident delirium. Pre-specified subgroup analyses were conducted based on stratification by age, Charlson Comorbidity Index, and baseline cognition. Post-hoc, four subgroups were identified based on differences in bivariate analyses. The effect of anesthetic approach (Relative Risk [95%CI]) is presented separately in each subgroup to define the effect of the intervention in that particular subgroup. The interaction term is a test of significance for whether the effect of anesthetic approach is statistically different between subgroups. Rapid release opioids refer to baseline opioids. Relative Risk <1 favors spinal anesthesia with targeted sedation based on BIS values. Relative Risk >1 favors general anesthesia with masked BIS values.