Common causes of hypovolemia are.
- Loss of blood (external or internal bleeding or blood donation)
- Loss of plasma (severe burns and lesions discharging fluid)
- Loss of body sodium and consequent intravascular water; e. G. Diarrhea or vomitin.
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).
There should be considered possible mechanisms of injury that may have caused internal bleeding, such as ruptured or bruised internal organs. If trained to do so and if the situation permits, there should be conducted a secondary survey and checked the chest and abdomen for pain, deformity, guarding, discoloration or swelling. Bleeding into the abdominal cavity can cause the classical bruising patterns of Grey Turner's sign or Cullen's sign.
Usually referred to as a "class" of shock. Most sources state that there are 4 stages of hypovolemic shock; however, a number of other systems exist with as many as 6 stages.
The 4 stages are sometimes known as the "Tennis" staging of hypovolemic shock, as the stages of blood loss (under 15% of volume, 15–30% of volume, 30–40% of volume and above 40% of volume) mimic the scores in a game of tennis: 15,15–30,30–40 and 40. It is basically the same as used in classifying bleeding by blood loss.
The signs and symptoms of the major stages of hypovolemic shock include:
Stage 1 Stage 2 Stage 3 Stage 4 headingBody Blood loss Up to 15% (750 mL) 15–30% (750–1500 mL) 30–40% (1500–2000 mL) Over 40% (over 2000 mL) Blood pressure Normal (Maintained by vasoconstriction) Increased diastolic BP Systolic BP < 100 Systolic BP < 70 Heart rate Normal Slight tachycardia (> 100 bpm) Tachycardia (> 120 bpm) Extreme tachycardia (> 140 bpm) with weak pulse Respiratory rate Normal Increased (> 20) Tachypneic (> 30) Extreme tachypnea Mental status Normal Slight anxiety, restless Altered, confused Decreased LOC, lethargy, coma Skin Pallor Pale, cool, clammy Increased diaphoresis Extreme diaphoresis; mottling possible Capillary refill Normal Delayed Delayed Absent Urine output Normal 20–30 mL/h 20 mL/h Negligible