Signs of hypovolemia may also be present, including:ĭehydration is more clinically evident in the elderly, especially in hot weather, due to impaired thirst sensation. Symptoms of more severe dehydration include: Low urine volume (unless the cause of dehydration is polyuria).Most patients with dehydration present with: serum albumin), causes fluid to diffuse out of capillaries and venules and into the interstitial space, resulting in dependent pitting edema and body cavity effusions. An increase in plasma hydrostatic pressure or a decrease in plasma oncotic pressure (i.e.The net direction of fluid movement depends on which Starling pressure is dominant.Fluid movement across a capillary wall into the interstitial space is driven by Starling pressures (not osmosis).
EFFECT OF DEHYDRATION ON BODY FLUID COMPARTMENTS SKIN
Normal total body sodium is associated with normal skin turgor and hydration.An increase in total body sodium increases the weight of the patient and is the most common cause of weight gain in a hospitalized patient.An increase in total body sodium increases plasma hydrostatic pressure due to an increase in plasma volume.Starling pressures are altered to produce pitting edema and body effusions. The Starling equation describes the forces that regulate the production of interstitial fluid in the situation of increased total body sodium.Fluid obeys the law of gravity and moves to the most dependent portion of the body (ankles when standing).Caused by low protein content in edematous fluid.Dependent pitting edema is due to an excess of sodium-containing fluid in the interstitial space (over 2–3 L).Increased total body sodium may produce body cavity effusions (ascites) and pitting edema.Decreased blood pressure and increased pulse (reflex tachycardia) when sitting up from the supine position (i.e., positive tilt test).Decreased skin turgor (skin tenting when the skin is pinched).
Common causes of increased fluid loss include vomiting, diarrhea, diuresis, and sweating. In the elderly, impaired thirst sensation, chronic illness, fever, and sickness are common causes of decreased water intake. Fluid loss from the intracellular space results in cellular shrinkage and metabolic dysfunction.ĭehydration occurs because of decreased water intake, increased fluid loss, or both. In dehydration, fluid from the extracellular compartment is depleted first, followed by fluid from the intracellular space. The intracellular compartment contains two-thirds of the total body water and consists of the fluid inside the body’s cells. The extracellular compartment contains one-third of total body water and consists of the intravascular, interstitial, and transcellular spaces. Total body water is distributed into extracellular and intracellular compartments. Hypovolemia is defined as decreased circulatory volume due to blood or plasma loss. The severity of dehydration ranges from mild to severe, and dehydration can be fatal when fluid loss exceeds more than 15% of the total body water.
The balance between fluid intake and fluid loss from the body is greatly disproportionate in dehydration. Dehydration is defined as the excessive loss of water from the body.
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