What are the different types of shock, including hypovolemic (low blood volume) shock, cardiogenic (heart-related) shock, distributive (circulatory) shock, and obstructive (blockage-related) shock?

From the Guidelines

Shock is a life-threatening condition that can be classified into four main types: hypovolemic, cardiogenic, distributive, and obstructive shock, each requiring immediate recognition and intervention to prevent multi-organ failure and death. The different types of shock include:

• Hypovolemic shock, which results from significant fluid loss, such as through hemorrhage, severe dehydration, or burns, leading to decreased circulating blood volume.
• Cardiogenic shock, which occurs when the heart fails to pump effectively, often due to myocardial infarction, cardiomyopathy, or severe arrhythmias, and is defined as hypotension (SBP < 90 mmHg) despite adequate filling status with signs of hypoperfusion 1.
• Distributive shock, which involves abnormal vasodilation and includes septic shock (from infection), anaphylactic shock (severe allergic reaction), and neurogenic shock (from spinal cord injury).
• Obstructive shock, which happens when blood flow is physically blocked, as in pulmonary embolism, cardiac tamponade, or tension pneumothorax.

Treatment of shock depends on the specific type but generally focuses on addressing the underlying cause while supporting circulation with fluids, vasopressors like norepinephrine (starting at 0.05-0.1 mcg/kg/min), or inotropes such as dobutamine (2.5-10 mcg/kg/min) when appropriate 1. The use of norepinephrine as a vasopressor is recommended when mean arterial pressure needs pharmacologic support, and dobutamine may be used as an inotropic agent in patients with low cardiac output. The pathophysiology of shock involves a cascade of compensatory mechanisms that eventually become harmful, including release of inflammatory mediators, endothelial damage, and microcirculatory dysfunction.

In the management of cardiogenic shock, immediate comprehensive assessment, including ECG and echocardiography, is required, and invasive monitoring with an arterial line should be considered 1. Pharmacologic therapy aims to improve organ perfusion by increasing cardiac output and blood pressure, and treatment is guided by the continuous monitoring of organ perfusion and hemodynamics. The routine use of intra-aortic balloon pump (IABP) cannot be recommended based on the current evidence, and device therapy should be considered when there is inadequate response to pharmacologic management 1.

Age is a nonmodifiable risk factor for mortality in patients with cardiogenic shock, and older adults are associated with higher in-hospital mortality across all stages of shock severity 1. Therefore, the management of cardiogenic shock in older adults requires careful consideration of the patient's underlying health status, comorbidities, and potential benefits and risks of different treatment strategies.

From the Research

Types of Shock

The different types of shock are categorized into four main categories:

• Hypovolemic shock: due to intravascular volume loss, treated by fluid replacement with balanced crystalloids 2
• Distributive shock: a state of relative hypovolemia resulting from pathological redistribution of the absolute intravascular volume, treated with a combination of vasoconstrictors and fluid replacement 2
• Cardiogenic shock: due to inadequate function of the heart, treated with drugs, surgery, or other interventional procedures depending on the situation 2, 3
• Obstructive shock: hypoperfusion due to elevated resistance, treated with an immediate life-saving intervention 2

Characteristics of Each Type of Shock

Each type of shock has distinct characteristics, including:

• Hypovolemic shock: relates to the blood and fluids compartment, due to intravascular volume loss 2
• Distributive shock: relates to the vascular system, resulting from pathological redistribution of the absolute intravascular volume 2
• Cardiogenic shock: arises from primary cardiac dysfunction, often secondary to an acute myocardial infarction 3
• Obstructive shock: arises from a blockage of the circulation, requiring immediate life-saving intervention 2

Diagnosis and Management

Diagnosis and management of shock involve:

• Identifying the need for critical interventions such as intubation, mechanical ventilation, or obtaining vascular access 4
• Prompt workup with laboratory testing and imaging, as indicated 4
• Determining the intravascular volume status of patients in shock to categorize and inform treatment decisions 4
• Continual re-assessment to differentiate between shock states, as one shock state may convert to another 5