Haemoglobin dilution from epidural‐induced hypotension with and without fluid loading

The blood haemoglobin concentration (B-Hb) was measured repeatedly to reflect dilution or concentration changes of the blood during onset of lumbar epidural anaesthesia in 90 elderly men. With crystalloid volume loading (10 ml.kg-1 b.w.), the decrease in B-Hb was twice as great for those who developed hypotension during the onset of the blockade as for patients whose arterial pressure remained normal (P less than 0.001), both when epidural anaesthesia was induced with plain mepivacaine, and when mepivacaine plus adrenaline was used. In a control group where no fluid loading was performed, there was no consistent change in the haemoglobin level, irrespective of blood pressure reaction to the blockade. The results suggest that crystalloid fluid loading allows an increase in blood volume in epidural-induced hypotension.