Shock is the state of insufficient blood flow to the tissues of the body as a result of problems with the circulatory system. Initial symptoms of shock may include weakness, fast heart rate, fast breathing, sweating, anxiety, and increased thirst. This may be followed by confusion, unconsciousness, or cardiac arrest, as complications worsen.Shock is divided into four main types based on the underlying cause: low volume, cardiogenic, obstructive, and distributive shock. Low volume shock, also known as hypovolemic shock, may be from bleeding, diarrhea, or vomiting. Cardiogenic shock may be due to a heart attack or cardiac contusion. Obstructive shock may be due to cardiac tamponade or a tension pneumothorax. Distributive shock may be due to sepsis, anaphylaxis, injury to the upper spinal cord, or certain overdoses.The diagnosis is generally based on a combination of symptoms, physical examination, and laboratory tests. A decreased pulse pressure (systolic blood pressure minus diastolic blood pressure) or a fast heart rate raises concerns. The heart rate divided by systolic blood pressure, known as the shock index (SI), of greater than 0.8 supports the diagnosis more than low blood pressure or a fast heart rate in isolation.Treatment of shock is based on the likely underlying cause. An open airway and sufficient breathing should be established. Any ongoing bleeding should be stopped, which may require surgery or embolization. Intravenous fluid, such as Ringers lactate or packed red blood cells, is often given. Efforts to maintain a normal body temperature are also important. Vasopressors may be useful in certain cases.
Other causes include burns, as well as excess urine loss due to diabetic ketoacidosis and diabetes insipidus.Signs and symptoms of hypovolemic shock include:

A rapid, weak, thready pulse due to decreased blood flow combined with tachycardia
Cool skin due to vasoconstriction and stimulation of vasoconstriction
Rapid and shallow breathing due to sympathetic nervous system stimulation and acidosis
Hypothermia due to decreased perfusion and evaporation of sweat
Thirst and dry mouth, due to fluid depletion
Cold and mottled skin (livedo reticularis), especially extremities, due to insufficient perfusion of the skinThe severity of hemorrhagic shock can be graded on a 1–4 scale on the physical signs. 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. Cardiogenic
Cardiogenic shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include dysrhythmias, cardiomyopathy/myocarditis, congestive heart failure (CHF), myocardial contusion, or valvular heart disease problems.Symptoms of cardiogenic shock include:

Distended jugular veins due to increased jugular venous pressure
Weak or absent pulse
Abnormal heart rhythms, often a fast heart rate
Pulsus paradoxus in case of tamponade
Reduced blood pressure
Shortness of breath, due to pulmonary congestion

Obstructive
Obstructive shock is a form of shock associated with physical obstruction of the great vessels of the systemic or pulmonary circulation. Several conditions can result in this form of shock.