Remote ischemic preconditioning prevents deterioration of short-term postoperative cognitive function after cardiac surgery using cardiopulmonary bypass: results of a pilot investigation

Abstract

Objective: Remote ischemic preconditioning (RIPC) exerts neuroprotective effects in models of cerebral ischemia-reperfusion injury. The authors tested the hypothesis that RIPC decreases the incidence of postoperative delirium and prevents deterioration of short-term postoperative cognitive function in isoflurane-fentanyl-anesthetized patients undergoing cardiac surgery using cardiopulmonary bypass (CPB).

Design: Randomized, blinded, single-center pilot investigation.

Setting: Veterans Affairs Medical Center.

Participants: Thirty age- and education-matched men≥55 years of age undergoing elective coronary artery or valve surgery using CPB. Fifteen nonsurgical patients also were enrolled.

Interventions: RIPC was produced after induction of anesthesia using 4 cycles of brief (5 minutes) upper extremity ischemia (tourniquet inflation to 200 mmHg) interspersed with 5-minute periods of reperfusion (tourniquet deflation).

Measurements and main results: The Intensive Care Delirium Screening Checklist was used to assess delirium before and each day after surgery for as many as 5 consecutive days. Recent verbal and nonverbal memory and executive functions were assessed before and 1 week after surgery using a standard neuropsychometric test battery or at 1-week intervals in nonsurgical controls. The Geriatric Depression and the Hachinski Ischemia scales were used to identify the presence of clinical depression and vascular dementia, respectively. No differences in delirium scores were observed between RIPC and control groups (p=0.54). Baseline neurocognitive scores were similar in patients with versus without RIPC in all 3 cognitive domains. Significant declines in performance on 2 nonverbal memory tests (figure reconstruction and delayed figure reproduction; p=0.001 and p=0.003, respectively) and 1 verbal memory test (delayed story recall; p=0.0004) were observed 1 week after surgery in patients who were not treated with RIPC. There were no changes in performance of measures of executive function in this group. In contrast, performance on all cognitive tests was unchanged after compared with before surgery in patients receiving RIPC. At least a 1-standard deviation decline from baseline in cognitive performance was detected in figure reconstruction, delayed figure reproduction, immediate story recall, and delayed story recall in patients who were not exposed to RIPC. The incidence of at least a 1-standard deviation decline in neuropsychometric tests was observed in significantly fewer (1 v 9; p<0.0001) patients with versus without RIPC treatment based on composite Z-scores. Overall cognitive performance after surgery was better in patients treated with versus without RIPC (p=0.002). Clinical depression and vascular dementia were not detected in either group.

Conclusion: The results of this pilot investigation indicated that RIPC prevented deterioration of short-term postoperative cognitive function but were unable to detect any difference in delirium in isoflurane-fentanyl-anesthetized patients undergoing cardiac surgery using CPB.

Keywords: cardiac surgery; cardiopulmonary bypass; delirium; isoflurane; neuroprotection; postoperative cognitive impairment; remote ischemic preconditioning.