hypovolemic

Hypovolemia, or a hypovolemic state, refers to a decreased volume of circulating intravascular blood. It results from loss of whole blood or plasma fluid, or from redistribution of fluid into the interstitial space (relative hypovolemia). The most common causes are acute hemorrhage and external losses such as vomiting, diarrhea, excessive sweating, or burns. Relative hypovolemia can occur in conditions like sepsis or pancreatitis.

The reduced intravascular volume lowers venous return to the heart, decreasing preload, cardiac output, and tissue perfusion. The body mobilizes compensatory mechanisms, including increased heart rate and vasoconstriction, but these may be insufficient in severe cases. Prolonged hypoperfusion can lead to organ dysfunction and shock. Clinically, patients may be tachycardic, hypotensive, cool and clammy, with reduced urine output and altered mental status. Orthostatic changes and dry mucous membranes are common findings.

Diagnosis is clinical and supported by laboratory studies. History of fluid loss or bleeding, along with vital signs and examination, guides suspicion. Laboratory patterns may include elevated BUN to creatinine ratio, hemoconcentration, metabolic acidosis, or elevated lactate in shock. Urine output monitoring and imaging to identify ongoing losses or sources of bleeding are part of evaluation.

Management emphasizes rapid restoration of intravascular volume and prevention of further losses. Initial treatment typically involves isotonic crystalloids, stopping ongoing fluid losses, and addressing the underlying cause. Blood products may be required for hemorrhagic hypovolemia. In persistent hypotension despite fluids, vasopressors and advanced monitoring may be used. Prognosis depends on the cause, rapidity of recognition, and the adequacy of resuscitation.