Direct measurement of arteriovenous anastomotic blood flow in the septic canine hindlimb.

Absolute blood flow through hindlimb capillaries and arteriovenous anastomoses (AVA) was determined by the radioactive microsphere technique of relative shunt measurement combined with direct (electromagnetic) measurement of femoral artery blood flow. Studies were performed before and 72 hours after infection was created in six dogs by implanting fecal-contaminated wicks in one hindlimb. Three control dogs had sterile wicks implanted. Septic dogs demonstrated decreased arterial pressure and increased core temperature with no change in mean cardiac index. Infected legs had increased total femoral blood flow, decreased peripheral resistance, decreased arteriovenous (A-V) O2 difference, but unchanged oxygen consumption, Paw temperature increased in both infected and normal contralateral limbs. Muscle blood flow (MBF) (Xe133 clearance) increased only in infected legs. A-V shunting increased five-fold and AVA flow increased seven-fold in infected hindlimbs, significantly more than that in contralateral or control limbs. Increased A-V shunting correlated highly (r=0.95) with increased total femoral blood flow in infected legs, but increased MBF was not correlated (r=0.05). Despite increased MBF, increased AVA flow occurs in septic canine hindlimbs and contributes to the low-resistance, high-flow, but unchanged oxygen consumption described in this model.