Classes of hemorrhage

What are the classes of hemorrhage?

Hemorrhage is divided into four classes based on the amount of blood loss. Class I hemorrhage produces the least amount of blood loss, and class IV, the greatest.

  • • Class I hemorrhage: The patient has lost up to 15% of his or her blood volume. Otherwise healthy patients are likely to have minimal tachycardia and no other symptoms. Unless there is ongoing hemorrhage, the patient should require no treatment.
  • • Class II hemorrhage: The patient has lost 15% to 30% of his or her blood volume. Loss of this amount of blood stimulates the compensatory mechanisms usually associated with early, compensated shock. Tachycardia, increased respiratory rate, and narrowed pulse pressure are seen. Urine output is usually maintained, but the patient may have signs of early central nervous system impairment. Such signs may include fright or anxiety.
  • • Class III hemorrhage: The patient has lost 30% to 40% of his or her blood volume. This amount of blood loss is clearly associated with signs of compensated shock but may also be associated with uncompensated shock. Even healthy individuals may have a drop in systolic blood pressure with this degree of blood loss. Urine output is likely to be decreased, and the patient may be very anxious or confused.
  • • Class IV hemorrhage: This represents loss of more than 40% of the circulating blood volume. This degree of hemorrhage is uniformly fatal if untreated. The shock state may, in some cases, be irreversible. The patient has a markedly decreased blood pressure. He or she can be expected to have complete peripheral vasoconstriction, extreme tachycardia, and little or no urinary output. Mental status is very depressed, and the patient may be unconscious.

How do the classes of hemorrhage relate to shock? 

There is no direct relationship. In fact, a patient can experience class I hemorrhage without demonstrating signs of shock. However, as patients experience greater degrees of hemorrhage, they are more likely to have symptoms of shock.


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