Shock and Hypotension

Shock is a life-threatening condition of circulatory failure manifesting as hypotension and causing hypoxia injury of cells and tissues.

The hallmark of shock is hypoperfusion.

It can be classified [SEE BELOW] as to its types and causes, but at the end of the day the cascade of effects is the same:

► HYPOPERFUSION → hypoxia of tissue → tissue ischemia → tissue death → organ failure → death.

 

Shock Classifications

There are four classes of shock:

1. Distributive: Shock that has severe peripheral vasodilation (vasodilatory shock). Included are

• septic shock,
• systemic inflammatory response syndrome,
• neurogenic shock,
• anaphylactic shock,
• toxic shock,
• end-stage liver disease,
• endocrine shock.

► HYPOPERFUSION: from lack of an adequate intravascular pressure head that drives blood and maintains the interacting pressures between intravascular and extravascular that makes respiration (in with O2, out with CO2) possible. 

2. Cardiogenic: Shock due to failure of the heart to act as a pump. It includes

• myocardial infarction,
• atrial and ventricular arrhythmias,
• valve or ventricle septal rupture.

► HYPOPERFUSION: from not enough force from the main pump (heart) to enable adequate blood flow to reach the cellular areas of respiration. 

3. Hypovolemic: Shock from reduced intravascular volume. Examples are

• hemorrhagic and
• non-hemorrhagic fluid losses.

► HYPOPERFUSION: from not enough volume to maintain the intravascular pressure necessary for equilibrium with the intracellular compartment that allows respiration exchange. 

4. Obstructive: Shock from cardiac pump failure not related directly to the heart. It includes

• pulmonary embolism,
• pulmonary hypertension,
• tension pneumothorax,
• constrictive pericarditis, and
• restrictive cardiomyopathy.

► HYPOPERFUSION: like cardiogenic shock, from not enough force from the main pump (heart) to enable adequate blood flow to reach the cellular areas of respiration. It doesn't matter whether the pump is broken or something else causes the pump to "act" broken.

 

Signs and Symptoms

The signs and symptoms of shock are highly dependent on how far the condition has progressed and the type of shock that is present. 

The universal signs of early/mid-stage shock are tachycardia (rarely bradycardia), oliguria, tachypnea, excessively cool or excessively warm skin, cyanosis, and narrow pulse pressure. Hypotension ironically may or may not be present depending on the patients resting blood pressure and stage of shock, mental status may or may not be unchanged. 

Patients in late-stage shock can have any number of signs and symptoms, but they are generally unconscious, appear extremely ill, and tend to have severe vital sign abnormalities. 

Management

Shock management is based on correcting the underlying problem while maintaining the ABC's through airway positioning/intubation, nonrebreather/bag-valve-mask use, and AED/defibrillator placement. All available monitors should be used if you feel the patient is at risk of acute decompensation. 

Correcting the problem depends upon the type of shock present, some are obvious: traumatic blood loss/sepsis requires fluids, anaphylaxis requires epinephrine, and spinal injuries require fluids/pressor agents. A key point in management is to identify cardiogenic shock (reviewed in later sections), giving fluids to a patient in cardiogenic shock will make the problem worse.

 

Cheat Sheet

Although there are exceptions to these, especially as shock progresses from early to severe, for testing purposes, this is a useful breakdown: 

CARDIOGENIC	HYPOVOLEMIC	NEUROGENIC	DISTRIBUTIVE
Hypotension	Hypotension (orthostatic first) Narrow pulse pressure	Hypotension	Hypotension Widened pulse pressure
Arrhythmia	Tachycardia	Bradycardia	Tachycardia
Cold, clammy skin	Cool extremities	Warm, dry skin	Pale, cool, diaphoretic skin
Pulmonary Edema	Deep, tachypnea.	Tachypnea	Shortness of breath

Note that neurogenic/septic/anaphylactic shock is are all types of distributive shock, neurogenic is separate due to its unique findings.