Deep hypothermic circulatory arrest (“circ arrest”) is often required for partial or total aortic arch reconstructions. At this point in the surgery, there is no blood flow anywhere. Because of systemic cooling to ~18°C, we mitigate the anaerobic and calcium-mediated apoptotic pathways that are implicated in neuronal dysfunction and can safely perform surgery for short circ arrest periods.
If a longer circ arrest period is expected, unilateral antegrade cerebral perfusion (ACP) is a technique that maintains brain perfusion and relies on collateralization through the Circle of Willis to perfuse the contralateral left brain. In one approach, a chimney graft (ie, 8 mm Gelweave) is sewn to the right axillary artery and perfused with an arterial cannula that connects to the cardiopulmonary bypass (CPB) circuit. Initially, this cannula perfuses the entire body through the graft with ~50 cc/kg/min of flow.
After the heart is arrested with cardioplegia and moderate systemic hypothermia is obtained, a clamp is placed proximally on the innominate artery and flow is lowered to ~ 10 cc/kg/min. Now the arterial cannula is only able to perfuse down the right arm and up the right vertebral/carotid systems into the brain. For this reason, a right radial arterial line pressure serves as a surrogate for cerebral perfusion pressure.
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