[Strategy for peroperative fluid therapy--balancing the central blood volume]

The strategy for preoperative volume treatment is not clear, partly because of the difficulty in monitoring the central blood volume (CBV). The cardiovascular responses to hypovolaemic shock are reviewed with emphasis on the often very low heart rate, which develops when the CBV is reduced by about 30%. A proposal has been put forward that normovolaemia is the CBV that does not limit cardiac output. The possibility of monitoring CBV by electrical impedance is also reviewed. It is concluded that the deviations reflect the CBV accurately in both experimental and clinical studies. A strategy that maintains the CBV ensures cerebral oxygenation even during extensive haemorrhage.