Decreased peripheral perfusion
| Shock | |
|---|---|
| Synonyms | Circulatory shock |
| Specialty | Cardiology, critical care medicine |
| Types | Hypovolemic, cardiogenic, obstructive, distributive |
| Classification | |
|---|---|
| External resources |
Shock is the state of low blood perfusion to tissues resulting in cellular injury and inadequate tissue function. The typical signs of shock are low blood pressure, rapid heart rate, signs of poor end-organ perfusion (e.g., low urine output, confusion, or loss of consciousness), and weak pulses.
Shock is divided into four main types based on the underlying cause: hypovolemic, cardiogenic, obstructive, and distributive shock. The shock index (SI), defined as heart rate divided by systolic blood pressure, is an accurate diagnostic measure that is more useful than hypotension and tachycardia in isolation. Under normal conditions, a number between 0.5 and 0.8 is typically seen. Should that number increase, so does suspicion of an underlying state of shock.
Circulatory shock is not related to the emotional state of shock. Circulatory shock is a life-threatening medical emergency and one of the most common causes of death. Shock can have a variety of effects, all with similar outcomes, but all relate to a problem with the body's circulatory system. For example, shock may lead to a lack of oxygen, cardiac, or respiratory arrest.
The presentation of shock is variable with some people having only minimal symptoms such as confusion and weakness. While the general signs for all types of shock are low blood pressure, decreased urine output, and confusion, these may not always be present. While a fast heart rate is common, those on β-blockers, those who are athletic and in 30% of cases of those with shock due to intra abdominal bleeding may have a normal or slow heart rate. Specific subtypes of shock may have additional symptoms.
Hypovolemia is a direct loss of effective circulating blood volume leading to:
The severity of hemorrhagic shock can be graded on a 1–4 scale on the physical signs. This approximates to the effective loss of blood volume. The shock index (heart rate divided by systolic blood pressure) is a stronger predictor of the impact of blood loss than heart rate and blood pressure alone. This relationship has not been well established in pregnancy-related bleeding.
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