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Shock. Stephanie N. Sudikoff, MD Pediatric Critical Care Yale School of Medicine. Learning Objectives. Understand the pathophysiology of shock Understand the principles of treatment of shock Examine septic shock as one example.
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Shock Stephanie N. Sudikoff, MD Pediatric Critical Care Yale School of Medicine
Learning Objectives • Understand the pathophysiology of shock • Understand the principles of treatment of shock • Examine septic shock as one example
“The reason you get up in the morning is to deliver oxygen to the cells.” Mark Mercurio, MD
Oxygen Consumption vs. Delivery • Oxygen consumption (DEMAND) • VO2 = CO x (CaO2-CvO2) • Oxygen delivery (SUPPLY) • DO2 = CO x CaO2
Preload • PreloadLV = (EDPLV)(EDrLV)/2tLV where, LV = left ventricle ED = end diastole • Represents all the factors that contribute to passive ventricular wall stress at the end of diastole
Factors affecting venous return • Decrease in intravascular volume • Increase in venous capacitance • Increase in right atrial pressure • Increase in venous resistance
Afterload • AfterloadLV = (SPLV)(SrLV)/2tLV where, LV = left ventricle S = systole • Represents all the factors that contribute to total myocardial wall stress during systolic ejection
Heart rate • HR CO • At high HR, diastolic filling is impaired • Atrial contraction accounts for up to 30% of Stroke Volume
Systemic response to low perfusion • Increase CO • Increase preload • Aldosterone • Na reabsorption • Interstitial fluid reabsorption • ADH secretion • Venoconstriction
Systemic response to low perfusion • Increase CO • Increase contractility • Sympathetics • Increase afterload • Vasoconstriction • Increase HR • Sympathetics
Systemic response to low perfusion • Increase CO • Increase contractility • Sympathetics • Increase HR • Sympathetics • Increase SVR • Vasoconstriction • Increase blood volume
Local response to low perfusion • Increase O2ER • Opening of previously closed capillaries • Increased surface area for diffusion • Shortened diffusion distance • Increased transit time
Objective monitors • Systemic perfusion • base deficit • lactate
Objective monitors • Systemic perfusion • ABG • lactate • CO • PA catheter • Arterio-venous oxygen difference • Preload • CVP • Echo • Myocardial contractility • Echo • Afterload • PA catheter • Invasive or noninvasive BP • HR • EKG • CaO2 • Hb • ABG
Goals of therapy • Treat underlying cause
Reduction of demands for CO • Treat hyperthermia aggressively
Reduction of demands for CO • Treat hyperthermia • Reduce work of breathing • As much as 20% of CO goes to respiratory muscles
PPV and CO Advantages • Decreases work of breathing • Improves acidosis • Decreases PVR • Decreases LV afterload • Improves oxygenation
Reduction of demands for CO • Treat hyperthermia • Reduce work of breathing • Sedation • Seizure control • Paralysis
Increase supply:Restoration of perfusion • Preload • Fluid resuscitation • Colloids vs. crystalloids
Increase supply:Restoration of perfusion • Preload • Fluid resuscitation • Colloids vs. crystalloids • Myocardial contractility • Inotropic support • ECMO • Other mechanical support
Increase supply:Restoration of perfusion • Preload • Fluid resuscitation • Colloids vs. crystalloids • Myocardial contractility • Inotropic support • ECMO • Other mechanical support • Afterload • Vasopressors • Vasodilators
Increase supply:Restoration of perfusion • Preload • Fluid resuscitation • Colloids vs. crystalloids • Myocardial contractility • Inotropic support • ECMO • Other mechanical support • Afterload • Vasopressors • Vasodilators • HR • Anti-arrhythmics • Pacer
Increase supply:Restoration of perfusion • Preload • Fluid resuscitation • Colloids vs. crystalloids • Myocardial contractility • Inotropic support • ECMO • Other mechanical support • Afterload • Vasopressors • Vasodilators • HR • Anti-arrhythmics • Pacer • Beta-blockers? • CaO2 • Blood transfusion • Oxygen support
Types of septic shock • Cold shock • ↓ CO, ↑ SVR (60% pediatric) • Narrow pulse pressure, thready pulses, delayed capillary refill
Phases of septic shock • Warm shock (“early”) • ↑ CO, ↓ SVR • ↓ CO, ↓ SVR • Wide pulse pressure, bounding pulses, brisk capillary refill • Cold shock (“late”) • ↓ CO, ↑ SVR • Narrow pulse pressure, weak pulses, delayed capillary refill
Increase preload • Aggressive fluid resuscitation
Increase preload • Aggressive fluid resuscitation • Usually requires 40-60 mL/kg but can be as much as 200 mL/kg • 20 mL/kg IV push titrated to clinical monitors