ABSTRACT
Using the clamping method (closing and opening the flap feeding artery) and continuous
laser Doppler flowmetry, the effects of blood withdrawals on flap blood flow and on
active and passive mechanisms regulating it were investigated in 12 Sprague-Dawley
rats. Measurements were made during stable normovolemic conditions, during hypovolemia
(after 3 ml/kg and after 6 ml/kg blood withdrawal), and after retransfusion of the
shed blood. The continuous blood flow responses during and after the clamping procedure
were analyzed. After clamp release, the increase in blood flow, duration of overshoot,
and peak flow of overshoot were significantly greater (the level of significance was
set equal to 0.05) in the registrations performed after blood withdrawals than before
them. The post-ischemic response curves indicating significantly increased flap hyperemia
during reperfusion in the registrations after blood withdrawals may be associated
with decreased vascular resistance in the flap. Thus, the authors conclude that a
short-term decrease in blood pressure caused by blood loss may prepare the flap microcirculation
for tolerating more ischemia.
KEYWORDS
Hemodynamics - blood loss - blood pressure - blood flow - laser doppler flowmetry
- free flap - microsurgery - vascular responsiveness
