Hypovolaemia is commonly inferred indirectly from
measurements of arterial pressure, heart rate, urinary
output and haematocrit. However, for the critically ill
patient, alteration of these measurements may not
indicate blood loss
15 and cardiac monitoring with right heart catheterisation and estimation of CVP, PAoP and
cardiac output may be required. Normal blood volume is
approximately 75 mL/kg for males and 70 mL/kg for
females, although during resuscitation from haemorrhage,
trauma or sepsis, patients may do better with 500
mL blood volume in excess of these normal values, to
compensate for maldistributions such as pooling of
blood in the splanchnic area.