Abstract

Fluid is continually being exchanged between the vascular space and the interstitium, and is returned to the vascular space via the lymph. The net balance of this movement determines the amount of fluid in the tissue. If there is too little fluid in the tissue, it becomes dehydrated, while excessive fluid collection causes oedema. Knowledge of the forces governing this movement, and the ability to define the alteration that has occurred, increases our understanding of the patient's condition and enables the response to treatment to be predicted.Fluid is continually being exchanged between the vascular space and the interstitium, and is returned to the vascular space via the lymph. The net balance of this movement determines the amount of fluid in the tissue. If there is too little fluid in the tissue, it becomes dehydrated, while excessive fluid collection causes oedema. Knowledge of the forces governing this movement, and the ability to define the alteration that has occurred, increases our understanding of the patient's condition and enables the response to treatment to be predicted.