Does acute anemia (lowered hemoglobin) alter limb blood flow and oxygen delivery during dynamic exercise in healthy men?
An acute reduction in hemoglobin concentration induces a compensatory elevation in submaximal muscle blood flow to maintain oxygen delivery, but this compensation fails at peak exercise despite available cardiac reserve.
We hypothesized that reducing arterial O2 content (CaO2) by lowering the hemoglobin concentration (Hb) would result in a higher blood flow, as observed with a low PO2, and maintenance of O2 delivery. Seven young healthy men were studied twice, at rest and during two-legged submaximal and peak dynamic knee extensor exercise in a control condition (mean control Hb 144 g/l) and after 1-1.5 liters of whole blood had been withdrawn and replaced with albumin mean drop in [Hb 29 g/l (range 19-38 g/l); low Hb]. Limb blood flow (LBF) was higher (P 75% of maximal cardiac output (approximately 26 l/min). It is concluded that a low CaO2 induces an elevation in submaximal muscle blood flow and that O2 delivery to contracting muscles is tightly regulated.
Koskolou et al. (1997) studied this question.