Cardiogenic and Obstructive Shock

The pump has failed, or something outside it is stopping it filling: how to tell them apart at the bedside and why the treatments are opposite.

CEN Content Outline, Cardiovascular Emergencies L. Both give you a patient who is hypotensive, cold and shut down. The difference is whether the pump is broken or blocked, and the treatments diverge immediately.

Cardiogenic Shock

The heart cannot generate enough output. Most often a large myocardial infarction, particularly anterior; also end-stage heart failure, fulminant myocarditis, severe valve failure, dysrhythmia, or drug overdose with a beta blocker or calcium channel blocker.

What it looks like

• Hypotension with a narrow pulse pressure. • Cold, mottled, clammy skin. Weak thready pulses. Delayed capillary refill. • Altered mental status, falling urine output. • Signs of congestion at the same time: crackles, jugular venous distension, hypoxia. Wet and cold — that combination is the fingerprint. • Rising lactate.

Treatment

• Find and treat the cause. If it is an MI, the answer is the cath lab, and quickly. • Fluids only cautiously, in small challenges, and only if the patient is not already congested. This is not a volume problem. • Inotropes to make the pump work: dobutamine, or milrinone. Vasopressors — norepinephrine is usually first — to hold a perfusing pressure. • No beta blockers, no nitroglycerin, no diuretics while the patient is shocked. All of them make it worse. • Mechanical support — intra-aortic balloon pump, Impella, ECMO — in centres that have it. • Non-invasive ventilation or intubation for the work of breathing, remembering that induction drops the pressure further.

Obstructive Shock

The pump is working. Something is stopping it filling or ejecting. There are four to recognise, and each has a mechanical fix.

Tension pneumothorax

Absent breath sounds and hyperresonance on one side, distended neck veins, hypotension, tracheal deviation as a late sign. Needle decompression followed by a chest tube. Do not wait for a chest X-ray.

Cardiac tamponade

Hypotension, distended neck veins, muffled heart sounds; narrowing pulse pressure and pulsus paradoxus. Pericardiocentesis.

Massive pulmonary embolism

Hypotension with a dilated right ventricle on echo, hypoxia, clear chest. Thrombolysis or embolectomy.

Auto-PEEP in a ventilated patient

Breath stacking in obstructive lung disease traps air, raises intrathoracic pressure and stops venous return. Disconnect the circuit and let them exhale; the pressure often returns within seconds. Then reduce the rate and lengthen expiratory time.

Telling Them Apart at the Bedside

• Neck veins are the quickest discriminator. Flat in hypovolemic and distributive shock; distended in cardiogenic and obstructive. • Lungs: crackles point to cardiogenic. A clear chest with severe hypoxia points to pulmonary embolism. Absent unilateral sounds point to tension pneumothorax. • Bedside ultrasound answers most of it in under a minute: the ventricle, the pericardium, lung sliding, the inferior vena cava.

Nursing Priorities

• The mistake to avoid is a fluid bolus by reflex. In cardiogenic shock it worsens the congestion; in tamponade it helps briefly; in tension pneumothorax it does nothing while the patient dies of something a needle would fix. • Get an early lactate and repeat it. Clearance is the measure of whether treatment is working. • Vasopressors through the largest, most reliable access available, and a central line as soon as practical; watch peripheral sites for extravasation. • Arterial line for anyone on titrated pressors — a cuff on a shut-down limb is not measuring what you think. • Keep the patient warm. Hypothermia worsens coagulopathy and acidosis. Topic list from the CEN Examination Content Outline effective July 2026 (BCEN, public document). This chapter was written for this app as study material and is not from any BCEN course.

Cardiogenic and Obstructive Shock