Fluid Resuscitation Principles and Monitoring

Fluid resuscitation is intended to improve effective circulating volume and tissue perfusion, not simply to increase the amount of water in the body. When circulating volume falls, venous return decreases, cardiac output can drop, and organs receive less oxygenated blood. The kidneys respond early to this reduction by conserving sodium and water, so falling urine output may be an early sign that perfusion is inadequate. The cause of poor perfusion determines whether fluid will help. Haemorrhage, gastrointestinal losses, burns, and severe dehydration can produce true volume loss. Sepsis is different: vasodilation and capillary leak make the circulating volume functionally inadequate even when total body water is not low. In cardiogenic shock, however, the failing heart may be unable to handle additional volume. More fluid can then raise pulmonary congestion without meaningfully improving cardiac output. This is why fluid is given as a monitored trial rather than as an automatic response to every low blood pressure reading. The nurse asks two questions at the same time: Is the patient showing signs of inadequate perfusion, and can the heart and lungs tolerate...