Hypovolemic shock

Hypovolemia
Classification and external resources
Specialty	Emergency medicine
ICD-10	E86, R57.1, T81.1
ICD-9-CM	276.52
MedlinePlus	000167
MeSH	D020896
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Hypovolemia, or oligemia, (also hypovolaemia or oligaemia) is a state of decreased blood volume; more specifically, decrease in volume of blood plasma. It is thus the intravascular component of volume contraction (or loss of blood volume due to things such as bleeding or dehydration), but, as it also is the most essential one, hypovolemia and volume contraction are sometimes used synonymously.

Hypovolemia is characterized by sodium depletion (salt depletion) and thus differs from dehydration, which is defined as excessive loss of body water.

Common causes of hypovolemia are

Excessive sweating is not a cause of hypovolemia, because the body eliminates significantly more water than sodium.

Clinical symptoms may not be present until 10–20% of total whole-blood volume is lost.

Hypovolemia can be recognized by tachycardia, diminished blood pressure, and the absence of perfusion as assessed by skin signs (skin turning pale) and/or capillary refill on forehead, lips and nail beds. The patient may feel dizzy, faint, nauseated, or very thirsty. These signs are also characteristic of most types of shock.

Note that in children compensation can result in an artificially high blood pressure despite hypovolemia. Children will typically compensate (maintain blood pressure despite loss of blood volume) for a longer period than adults, but will deteriorate rapidly and severely once they do begin to decompensate. This is another reason (aside from initial lower blood volume) that even the possibility of internal bleeding in children should almost always be treated aggressively.

Obvious signs of external bleeding should be noted while remembering that people can bleed to death internally without any external blood loss. ("Blood on the floor, plus 4 more" = intrathoracic, intraperitoneal, retroperitoneal, pelvis/thigh)

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