CCRN Notes

Cardiogenic Shock

Definition & Causes

  • Heart fails as a pump - inadequate tissue perfusion

  • Most common cause: Large MI (>40% LV involvement)

  • Other causes: Cardiomyopathy, valvular dysfunction, arrhythmias, mechanical complications

  • Mechanical complications: Papillary muscle rupture, VSD, free wall rupture

Hemodynamic Profile

  • Decreased CO/CI (<2.2 L/min/m²)

  • Elevated PAOP (>18 mmHg)

  • Elevated SVR (compensatory vasoconstriction)

  • Hypotension: SBP <90 mmHg or MAP <65 mmHg

  • Low SvO2 (<60%) indicating increased oxygen extraction

Clinical Presentation

  • Cold, clammy skin (poor perfusion)

  • Altered mental status

  • Oliguria (<0.5 mL/kg/hr)

  • Elevated lactate (tissue hypoperfusion)

  • Pulmonary congestion (crackles, dyspnea)

Management

  • Optimize oxygenation - may need mechanical ventilation

  • Inotropes: Dobutamine (increases contractility, vasodilation)

  • Vasopressors: Norepinephrine if severely hypotensive

  • Avoid excessive fluids - already volume overloaded

  • Mechanical support: IABP, Impella, LVAD, ECMO

  • Treat underlying cause: Revascularization for MI

Shock Categories & Classification

Overview of Shock

  • Definition: Inadequate tissue perfusion leading to cellular hypoxia

  • Four main categories: Distributive, Cardiogenic, Hypovolemic, Obstructive

  • Common endpoint: End-organ dysfunction from oxygen supply-demand mismatch

  • Early recognition and treatment essential to prevent irreversible damage

Distributive Shock

  • Characterized by widespread vasodilation and loss of vascular tone

  • SEPTIC: Most common - caused by infection (Gram+, Gram-, fungal, viral)

  • NEUROGENIC: Spinal cord injury disrupts sympathetic tone (bradycardia + hypotension)

  • ANAPHYLACTIC: Severe allergic reaction causing massive histamine release

  • Other causes: Liver failure, SIRS, toxic shock syndrome, transfusion reactions

  • Hemodynamics: Low SVR, high CO (warm shock initially), elevated or normal PAOP

Cardiogenic Shock

  • Primary pump failure - heart cannot maintain adequate cardiac output

  • Cardiomyopathic causes: MI, RV infarct, heart failure exacerbation, myocarditis

  • Drug-induced: Beta-blocker overdose, calcium channel blocker toxicity

  • Stunned myocardium: Post-arrest, post-cardiopulmonary bypass

  • Hemodynamics: Low CO/CI, elevated PAOP, elevated SVR

  • Clinical: Cold extremities, pulmonary edema, oliguria

Hypovolemic Shock

  • Inadequate circulating volume leading to decreased preload

  • HEMORRHAGIC: Trauma, GI bleeding, surgical blood loss, retroperitoneal bleed

  • NON-HEMORRHAGIC: Severe dehydration, vomiting/diarrhea, burns, third-spacing

  • Hemodynamics: Low CO, low PAOP/CVP, elevated SVR (compensatory)

  • Treatment: Volume resuscitation - crystalloids, blood products for hemorrhagic

  • Massive transfusion protocol: 1:1:1 ratio PRBC:FFP:Platelets

Obstructive Shock

  • Mechanical obstruction to blood flow impairs cardiac output

  • PULMONARY VASCULAR: Massive PE, severe pulmonary hypertension, air embolism

  • MECHANICAL: Tension pneumothorax, cardiac tamponade, constrictive pericarditis

  • Key feature: JVD with hypotension (blood cannot enter or leave heart)

  • Treatment: Relieve obstruction (needle decompression, pericardiocentesis, thrombolytics)

  • Hemodynamics: Low CO, elevated CVP, variable SVR

Shock Differentiation by Hemodynamics

  • Distributive: ↓SVR, ↑CO (early), normal/low PAOP

  • Cardiogenic: ↑SVR, ↓CO, ↑PAOP

  • Hypovolemic: ↑SVR, ↓CO, ↓PAOP

  • Obstructive: Variable SVR, ↓CO, ↑CVP

  • SvO2 <60% in all types indicates inadequate oxygen delivery

  • Lactate elevation indicates tissue hypoperfusion regardless of type