Analysis of collateral blood flow to the lower body during selective cerebral perfusion: is three-vessel perfusion better than two-vessel perfusion?

OBJECTIVE During selective cerebral perfusion (SCP), only the upper body is perfused. However, blood actually returns into the descending aorta through collaterals during SCP. This collateral blood flow (CBF) is thought to be important to protect the visceral organs and spinal cord from ischemia. The left subclavian artery is postulated to be important as a collateral source to the lower body. Therefore, we measured CBF and examined whether a perfusion technique (three- or two-vessel perfusion) affects CBF to the lower body during SCP. METHODS CBF was measured in 49 patients who underwent aortic arch surgery with SCP between August 2006 and July 2008. CBF, the amount of blood returning into the descending aorta during SCP, was measured under conditions of constant flow during SCP, with three-vessel cannulation that included the left subclavian artery, or with two-vessel cannulation that excluded the left subclavian artery. To prove visceral perfusion during SCP, hepatic (n=22) and stomach (n=5) tissue blood flows were measured using a laser-Doppler flowmeter. RESULTS The mean perfusion flow rate during SCP was 804+/-91ml/min. The mean CBF under three-vessel perfusion (53+/-34ml/min, 6.5+/-3.8% of SCP) was significantly (p<0.0001) higher compared with that under two-vessel perfusion (43+/-29ml/min, 5.3+/-3.1% of SCP). There was substantial perfusion in the visceral organs during SCP as determined by laser-Doppler flowmeter. CONCLUSION Visceral organs were perfused to some extent through collaterals and protected from ischemia during SCP. Left subclavian arterial perfusion enabled significant CBF to the lower body. Considering this CBF, three-vessel perfusion appears to be better than two-vessel perfusion during SCP; however, the choice of perfusion technique may not be so important under conditions of hypothermia because the difference in CBF between the two methods was small.