Evaluating Antegrade Cerebral Perfusion Flow Rates for Neuroprotection During Hypothermic Circulatory Arrest

Hypothermia is used to reduce metabolic demand and ischemic neurologic injury during cardiac surgery requiring circulatory arrest. However, adverse effects of hypothermia limit safe arrest times. Antegrade cerebral perfusion (ACP) may allow longer arrest; however, randomized data are lacking to inform optimal operative strategies. We hypothesized that an ideal ACP flow rate could be determined that would provide neurocognitive protection during hypothermic circulatory arrest (HCA).

Eighteen animals underwent HCA (90 minutes) and unilateral ACP through the carotid artery at 2.5, 5, or 10 mL/kg per minute. Animals were compared with controls that received intravenous ketamine (potentially neuroprotective) but no ACP. Animals were survived and assessed for 3 days. Outcomes included behavior deficit scores, cognition (novel object recognition), neuropathologic injury, inflammatory response, and neurologic injury biomarkers.

No differences in postoperative behavioral deficit scores, cognition, or neuropathologic injury were observed in animals receiving ACP at any rate. ACP animals demonstrated improved behavioral scores vs controls on postoperative days 1 and 2 (both P values < .05). Cognition was preserved in ACP-treated animals, with the 10 mL/kg per minute group demonstrating postoperative preference for the novel object (P < .05), consistent with intact cognition. Neuropathologic analysis demonstrated a trend toward lower global brain injury scores in ACP-treated animals compared with controls (P = .06). Neurologic injury biomarkers and inflammatory markers were attenuated with high-flow ACP relative to lower flow groups (P < .05).

Our findings support the use of ACP as a neuroprotection strategy and suggest that increased flow rates within the studied range could be beneficial in patients undergoing HCA.