A 37-year-old woman presents to the emergency department in cardiac arrest. She was found to have altered mental status at home, and during transport to the hospital, she became pulseless. Cardiopulmonary resuscitation is ongoing and 2 intravenous lines are placed. The patient is obese, and her only medication is an oral contraceptive pill. She recently underwent Achilles tendon repair. She otherwise is known to smoke cigarettes on occasion. Physical exam is notable for a critically ill patient with chest compressions ongoing. The monitor shows pulseless electrical activity. Her right lower extremity is in a post-operative splint. The patient regains her pulse after several rounds of CPR and epinephrine. A bedside echocardiograph is notable for a dilated and hypokinetic right ventricle with septal bowing into a hyperkinetic left ventricle. Which of the following is the most likely diagnosis?
Obstructive shock
Hemorrhagic shock
Cardiogenic shock
Septic shock
Obstructive shock
This obese patient on oral contraceptive pills with recent orthopedic surgery (Achilles tendon repair) is presenting in cardiac arrest. Given the bedside echocardiograph that is notable for a dilated and hypokinetic right ventricle with septal bowing into a hyperkinetic left ventricle, the most likely diagnosis is a pulmonary embolism that is causing obstructive shock.

Pulmonary embolism is most commonly caused by a deep vein thrombosis in the veins of the lower extremity that travels to the pulmonary circulation. Patients will present with pleuritic chest pain, hypoxia, sinus tachycardia, and hemoptysis. Massive pulmonary emboli can cause hemodynamic instability. Patients may become hypotensive, tachycardic, and ultimately pulseless. The pulmonary embolism can obstruct blood flow from the right ventricle to the pulmonary artery, leading to a dilated and hypokinetic right ventricle with septal bowing and a hyperdynamic left ventricle. This is a type of obstructive shock. Treatment of a massive pulmonary embolism causing hemodynamic instability may involve thrombolytics or thrombectomy.

Standl et al. review obstructive shock. They note that obstructive shock is caused by an obstruction of blood flow out of (or in the case of tamponade, into) the heart. They recommend that treating the underlying cause is the only effective management option.

Incorrect Answers:
Answer A: Cardiogenic shock is caused by cardiac dysfunction in conditions such as myocardial infarction or heart failure. Cardiac dysfunction then leads to impaired systemic perfusion. Initial management includes treating the underlying cause (e.g., cardiac catheterization for an ST-elevation myocardial infarction) and vasopressors (e.g., norepinephrine) to maintain the patient’s blood pressure.

Answer B: Hemorrhagic shock is a common cause of shock in trauma and presents with hypotension and tachycardia secondary to blood loss. A narrowed pulse pressure may be the first sign of hemorrhagic shock. The mainstay of management is blood transfusion and an intervention to stop the bleeding.

Answer C: Neurogenic shock occurs when there is central nervous system trauma (often to the cervical spine) leading to decreased sympathetic tone systemically. Patients will present with hypotension and bradycardia (contrast with tachycardia in hemorrhagic shock), and management is centered on vasopressors to maintain blood pressure and neurosurgical intervention for the underlying etiology. IV fluids can also be given to maintain blood pressure.

Answer E: Septic shock occurs when a systemic infection leads to vasodilation and endothelial dysfunction with hypotension refractory to fluid resuscitation. The mainstay of management includes fluids, blood cultures, vasopressors, and broad-spectrum antibiotics. Early administration of antibiotics improves outcomes.

Bullet Summary:
Pulmonary embolism is a common cause of obstructive shock.