Outline the physiological responses to anaemia. (The specific physiological responses to
hypovolaemia are NOT required.)
It was expected candidates would expand on the central role haemoglobin has in oxygen delivery and that in the presence of reduced haemoglobin there are various efforts aimed at maintaining oxygen delivery. Cardiac output is increased, systemic vascular resistance is reduced, modifications are seen in regional circulations and as tissue oxygenation begins to falter then the end products of anaerobic metabolism provide a further stimulus to enhance cardiac out and tissue oxygen delivery. Better answers also included a mention of additional factors that enhance tolerance of chronic anaemia (e.g.angiogenesis).
Total blood oxygen delivery (DO2) = CO × CaO2,
and CaO2 = (sO2 × ceHb × BO2 ) + (PaO2 × 0.03)
Where the ceHb is in decline, the other variables which describe CaO2 are usually not susceptible to large-scale change, and therefor the cardiac output needs increase.
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