Obstructive shock

Obstructive shock is one of the four types of shock, caused by a physical obstruction in the flow of blood. Obstruction can occur at the level of the great vessels or the heart itself. Causes include pulmonary embolism, cardiac tamponade, and tension pneumothorax. These are all life-threatening. Symptoms may include shortness of breath, weakness, or altered mental status. Low blood pressure and tachycardia are often seen in shock. Other symptoms depend on the underlying cause. The physiology of obstructive shock is similar to cardiogenic shock. In both types, the heart's output of blood (cardiac output) is decreased. This causes a back-up of blood into the veins entering the right atrium. Jugular venous distension can be observed in the neck. This finding can be seen in obstructive and cardiogenic shock. With the decrease cardiac output, blood flow to vital tissues is decreased. Poor perfusion to organs leads to shock. Due to these similarities, some sources place obstructive shock under the category of cardiogenic shock. However, it is important to distinguish between the two types, because treatment is different. In cardiogenic shock, the problem is in the function of the heart itself. In obstructive shock, the underlying problem is not the pump.…

Obstructive shock is one of the four types of shock, caused by a physical obstruction in the flow of blood. Obstruction can occur at the level of the great vessels or the heart itself. Causes include pulmonary embolism, cardiac tamponade, and tension pneumothorax. These are all life-threatening. Symptoms may include shortness of breath, weakness, or altered mental status. Low blood pressure and tachycardia are often seen in shock. Other symptoms depend on the underlying cause. The physiology of obstructive shock is similar to cardiogenic shock. In both types, the heart's output of blood (cardiac output) is decreased. This causes a back-up of blood into the veins entering the right atrium. Jugular venous distension can be observed in the neck. This finding can be seen in obstructive and cardiogenic shock. With the decrease cardiac output, blood flow to vital tissues is decreased. Poor perfusion to organs leads to shock. Due to these similarities, some sources place obstructive shock under the category of cardiogenic shock. However, it is important to distinguish between the two types, because treatment is different. In cardiogenic shock, the problem is in the function of the heart itself. In obstructive shock, the underlying problem is not the pump. Rather, the input into the heart (venous return) is decreased or the pressure against which the heart is pumping (afterload) is higher than normal. Treating the underlying cause can reverse the shock. For example, tension pneumothorax needs rapid needle decompression. This decreases the pressure in the chest. Blood flow to and from the heart is restored, and shock resolves. __TOC__

Causes

l and mediastinal shift from the patient's left to right.]] Causes include any obstruction of blood flow to and from the heart. There are multiple, including pulmonary embolism, cardiac tamponade, and tension pneumothorax. Other causes include abdominal compartment syndrome, Hiatal hernia, severe aortic valve stenosis, and disorders of the aorta. Constrictive pericarditis is a rare cause. Masses can grow to press on major blood vessels causing shock.

Diagnosis

Rapid evaluation of shock is essential given its life-threatening nature. Diagnosis requires a thorough history, physical exam, and additional tests. One must also consider the possibility of multiple types of shock being present. For example, a trauma patient may be hypovolemic from blood loss. This patient could also have tension pneumothorax due to trauma to the chest. Vital signs in obstructive shock may show hypotension, tachycardia, and/or hypoxia. A physical exam include be thorough, including jugular vein exam, cardiac and lung exams, and assessing skin tone and temperature. Response to fluids may aid in diagnosis. Labs including a metabolic panel can assess electrolytes and kidney and liver function. Lactic acid rises due to poor tissue perfusion. This may even be an initial sign of shock and rise before blood pressure decreases. Lactic acid should lower with appropriate treatment of shock. EKG should also be performed. Tachycardia is often present, but other specific findings may be present based on the underlying cause. At the bedside, point-of-care echocardiography should be used. This is non-invasive and can help diagnose the four types of shock. Echocardiography can look for ventricular dysfunction, effusions, or valve dysfunction. Measurement of the vena cava during the breathing cycle can help assess volume status. A point-of-care echocardiogram can also assess for causes of obstructive shock. The vena cava would be dilated due to the obstruction. In pulmonary embolism, the right ventricle will be dilated. Other findings include paradoxical septal motion or clots in the right heart or pulmonary artery. Echocardiography can assess for pericardial effusion. In tamponade, collapse of the right atrium and ventricle would be seen due to pressure in the pericardial sac. A chest X-ray can rapidly identify a pneumothorax, seen as absence of lung markings. Ultrasound can show the lack of lung sliding. However, imaging should not delay treatment. CT angiography is the standard of diagnosis of pulmonary embolism. Clots appear in the vasculature as filling defects.

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