Anesthetic Management Using Multiple Closed-loop Systems and Delayed Neurocognitive Recovery: A Randomized Controlled Trial.

BACKGROUND: Cognitive changes after anesthesia and surgery represent a significant public health concern. We tested the hypothesis that, in patients 60 yr or older scheduled for noncardiac surgery, automated management of anesthetic depth, cardiac blood flow, and protective lung ventilation using three independent controllers would outperform manual control of these variables. Additionally, as a result of the improved management, patients in the automated group would experience less postoperative neurocognitive impairment compared to patients having standard, manually adjusted anesthesia. METHODS: In this single-center, patient-and-evaluator-blinded, two-arm, parallel, randomized controlled, superiority study, 90 patients having noncardiac surgery under general anesthesia were randomly assigned to one of two groups. In the control group, anesthesia management was performed manually while in the closed-loop group, the titration of anesthesia, analgesia, fluids, and ventilation was performed by three independent controllers. The primary outcome was a change in a cognition score (the 30-item Montreal Cognitive Assessment) from preoperative values to those measures 1 week postsurgery. Secondary outcomes included a battery of neurocognitive tests completed at both 1 week and 3 months postsurgery as well as 30-day postsurgical outcomes. RESULTS: Forty-three controls and 44 closed-loop patients were assessed for the primary outcome. There was a difference in the cognition score compared to baseline in the control group versus the closed-loop group 1 week postsurgery (-1 [-2 to 0] vs. 0 [-1 to 1]; difference 1 [95% CI, 0 to 3], P = 0.033). Patients in the closed-loop group spent less time during surgery with a Bispectral Index less than 40, had less end-tidal hypocapnia, and had a lower fluid balance compared to the control group. CONCLUSIONS: Automated anesthetic management using the combination of three controllers outperforms manual control and may have an impact on delayed neurocognitive recovery. However, given the study design, it is not possible to determine the relative contribution of each controller on the cognition score.

Blood pressure variability in surgical and intensive care patients: Is there a potential for closed-loop vasopressor administration?

Blood pressure management in the operating rooms (OR) and intensive care units (ICU) frequently involves manually titrated vasopressor therapy to an optimal range of mean arterial pressure (MAP). Ideally, changes in vasopressor infusion rates have to quickly follow variations in blood pressure measurements. However, such a tightly controlled feedback loop is difficult to achieve. Few studies have examined blood pressure control when vasopressor therapy is administered manually in OR and ICU patients. We extracted MAP data from 3623 patients (2530 from the ORs and 1093 from the ICU) on vasopressors from our electronic medical records. Coefficient of variation (= standard deviation/mean value) *100) was calculated and the values were additionally categorized into different MAP ranges (MAP < 60 mmHg, 60 < MAP < 80 and MAP > 80 mmHg). There was no statistically significant difference between both centres for MAP across all time points (80 ± 12 vs. 80 ± 16, P = 0.996, 95% CI -6 to 6). The coefficients of variation of MAP were 13.7 ± 5.4% and 18.4 ± 9.8% in the OR and in ICU respectively. Patients on vasopressors spent 48.8% treatment time with a MAP between 60 and 80 mmHg (11.2% time with MAP < 60 mmHg, and 40% with MAP > 80 mmHg). These results provide a reasonable baseline from which to establish whether 'reduced variability' may be achieved with a closed-loop vasopressor administration system.