Shock States PDF

Shock States EMERGENCY MEDICINE C E R T I F I C AT E Definition of shock Imbalance between oxygen demand and oxygen supply What is Shock? Characterized by… End organ dysfunction Altered hemodynamic parameters Abnormal oxygen metabolism EMERGENCY MEDICINE C E R T I F I C AT E Clinical Signs and Sympt...

Shock States EMERGENCY MEDICINE C E R T I F I C AT E Definition of shock Imbalance between oxygen demand and oxygen supply What is Shock? Characterized by… End organ dysfunction Altered hemodynamic parameters Abnormal oxygen metabolism EMERGENCY MEDICINE C E R T I F I C AT E Clinical Signs and Symptoms of Shock Altered mental status Weakness Dizziness Confusion Coma Cool, clammy skin Pallor Reduced urine output EMERGENCY MEDICINE C E R T I F I C AT E Laboratory Parameters Suggestive of Shock Increased sCr Increased aPTT, PT/INR Increased venous lactate Increased troponin EMERGENCY MEDICINE C E R T I F I C AT E Function of cardiac output and systemic vascular resistance BP = CO x SVR What is Blood Pressure? Cardiac output is a function of heart rate and stroke volume CO = HR x SV Systemic vascular resistance is a measure of vascular tone Requires measured central venous pressure or CO to calculate Not often used, but conceptually important EMERGENCY MEDICINE C E R T I F I C AT E Hemodynamic Parameters Consistent with Shock Decreased systolic blood pressure Decreased MAP Increased HR EMERGENCY MEDICINE C E R T I F I C AT E What is MAP? MAP = mean arterial pressure MAP = SBP + (2 x DBP) 3 Can be thought of as the perfusion pressure received by the organs Normal range is 80-100 mmHg EMERGENCY MEDICINE C E R T I F I C AT E How are BP and MAP Measured? Non-invasive BP cuff over brachial artery Directly measures SBP and DBP MAP can be calculated Invasive Arterial line Allows for direct measurement of MAP, SBP, DBP Allows for easier attainment of arterial blood samples for ABG monitoring EMERGENCY MEDICINE C E R T I F I C AT E Hypovolemic Hemorrhagic Dehydration Distributive What Causes Shock? Sepsis Anaphylactic Neurogenic Cardiogenic Heart failure Arrhythmias Obstructive Pulmonary embolism Pericardial tamponade Tension pneumothorax EMERGENCY MEDICINE C E R T I F I C AT E How Do We Treat Shock? Depends on the underlying cause! Hypovolemic shock Volume, volume, volume Distributive shock Volume, then vasoconstriction Cardiogenic shock Decrease cardiac workload, improve cardiac output Obstructive shock Remove the obstruction EMERGENCY MEDICINE C E R T I F I C AT E Hypovolemic Shock What causes hypovolemic shock? Hemorrhage Inadequate volume repletion Vomiting and diarrhea Third spacing EMERGENCY MEDICINE C E R T I F I C AT E Intracellular 2/3 of total body fluid volume Fluid Distribution Extracellular 1/3 of total body fluid volume Further divided into… Interstitial 3/4 of extracellular compartment Intravascular 1/4 of extracellular compartment EMERGENCY MEDICINE C E R T I F I C AT E Fluid Distribution Factors impacting how fluids distribute Osmolarity/osmolality Number of solutes in a solution Takes into consideration all solutes Tonicity Effective osmolality Solutes that cannot cross semipermeable membrane Oncotic pressure Formerly known as colloid osmotic pressure Osmotic pressure exerted by proteins Pulls fluid in EMERGENCY MEDICINE C E R T I F I C AT E Tonicity Isotonic fluids stay in the extracellular space Ionized molecules do not readily cross cell membrane Fluid distributes equally between intravascular and interstitial space If 1 L of LR or NS given 750 mL will distribute to interstitial space 3/4 of extracellular compartment 250 mL will remain intravascular 1/4 of extracellular compartment EMERGENCY MEDICINE C E R T I F I C AT E Tonicity Continued Hypotonic fluids distribute into intracellular and extracellular space Dextrose crosses cell membrane D5W considered hypotonic but iso-osmotic D5W distributes equally between intracellular and extracellular compartments If 1 L of D5W given… 666 mL will distribute to intracellular compartment 333 mL will distributed to extracellular compartment 250 mL will distribute to interstitial space 83 mL will distribute to intravascular space EMERGENCY MEDICINE C E R T I F I C AT E Tonicity Continued Hypertonic fluids stay in the extracellular space AND have the potential to pull fluid from intracellular to extracellular space Distribute equally between intravascular and interstitial space If 1 L of 3% NaCl given 750 mL will distribute to interstitial space and may pull fluid from other compartments 250 mL will remain intravascular and may pull fluid from other compartments EMERGENCY MEDICINE C E R T I F I C AT E Are Isotonic Fluids All the Same? Normal saline Not quite normal 154 mEq Na per L 154 mEq Cl per L Balanced salt solutions Lactated Ringer’s solution Plasmalyte A EMERGENCY MEDICINE C E R T I F I C AT E NS vs BSS SMART trial NS vs BSS in critically ill adults 15,802 patients cluster-randomized to either NS or BSS Primary outcome was major adverse kidney event within 30 days Composite of 30 day mortality, persistent renal dysfunction, or need for new renal-replacement therapy 14.3% in BSS group vs 15.4% in NS group (p=0.04) No significant difference between groups for components of composite endpoint EMERGENCY MEDICINE C E R T I F I C AT E Concerns with BSS Things you should probably be concerned about… Compatibility issues LR contains Ca2+ Plasmalyte contains Mg2+, acetate, and gluconate Less data available for LR and Plasmalyte Myths you can help bust… LR contains lactate, can’t use in lactic acidosis LR/Plasmalyte contain K, can’t use in renal dysfunction EMERGENCY MEDICINE C E R T I F I C AT E What About Colloids? Large molecules that remain in the intravascular space Oncotic force may pull fluid into the intravascular space If 1 L of 5% albumin given… 100% will remain in intravascular space A variety of options available Starches Dextrans Albumin So why don’t we use colloids more frequently? EMERGENCY MEDICINE C E R T I F I C AT E Colloids Hydroxyethyl starch CHEST study in 2012 No difference in outcomes Increased overall adverse events Increased need for renal replacement therapy Increased AKI Dextrans Significant toxicities Anaphylactoid/anaphylactic reactions, renal dysfunction, coagulopathies EMERGENCY MEDICINE C E R T I F I C AT E Colloids Albumin Theoretically appealing but… Leaks into extravascular space soon after administration Leakage will pull fluid into extravascular space Large studies found no difference in outcomes compared to NS SAFE trial evaluated 4% albumin vs NS in 6997 patients No difference in outcomes No difference in ADEs Huge difference in cost EMERGENCY MEDICINE C E R T I F I C AT E Preferred for volume expansion in mod to severe hemorrhagic shock Remain in the vasculature providing volume expansion Blood Products Provide physiologic benefits beyond volume expansion PRBCs improve oxygen carrying capacity FFP provides clotting factors Platelets Cryoprecipitate provides fibrinogen, von Willebrand factor, and other clotting factors EMERGENCY MEDICINE C E R T I F I C AT E Hemorrhage control Permissive hypotension Prevention of trauma induced coagulopathy Hemorrhagic Shock Prevention of trauma induced hypothermia Administration of blood products preferred for moderate to severe hemorrhagic shock Massive transfusion protocols Combination of PRBCs, FFP, and platelets Blood products contain citrate based anticoagulant Can bind endogenous calcium EMERGENCY MEDICINE C E R T I F I C AT E If hemodynamically unstable, start with isotonic fluids Dehydration Hypotonic fluids for replacement Estimate total body water (TBW) Approximately 50% of lean body weight Use caution in hypernatremia/hyperosmolar states Maximum sodium correction = 10 mEq in first 24 hours Calculate expected change in serum sodium per L infused Change in serum Na per L = (Infusate Na – Serum Na) (TBW + 1) Calculate volume required to correct by 10 mEq in first 24 hours 10 mEq / change in serum Na per L = volume required Add maintenance fluid requirement, divide by 24 hr for rate EMERGENCY MEDICINE C E R T I F I C AT E Fluid shifts/third spacing due to capillary leakage Intravascular depletion, edema Skin is primary barrier to external fluid losses Burns Burn patients require large volume resuscitation initially Parkland equation 4 mL/kg x BSA burned = fluid requirement for first 24 hours 50% administered in first 8 hours, remainder over next 16 hours EMERGENCY MEDICINE C E R T I F I C AT E Alpha 1 receptor Causes vasoconstriction, increases SVR Sites of Action for Vasopressors Beta 1 receptor Increases HR (chronotropy), cardiac contractility (inotropy) Beta 2 receptor Decreases SVR (vasodilation), bronchodilation Vasopressin receptor Causes vasoconstriction, increases SVR Angiotensin receptor Causes vasoconstriction, increases SVR EMERGENCY MEDICINE C E R T I F I C AT E Alpha 1 (↑ SVR) Phenylephrine Beta 1 (↑ HR) Beta 2 (↓ SVR) ↑↑↑ ↑ Dopamine ↑↑↑ Isoproterenol Norepinephrine ↑↑↑ ↑ Epinephrine ↑↑↑ ↑↑↑ Dopamine High dose (>10 mcg/kg/min) Medium dose (5-10 mcg/kg/min) ↑↑↑ Low dose (< 3 mcg/kg/min) ↑↑↑ Vasopressin Dobutamine V1 (↑ SVR) ↑↑↑ ↑↑ EMERGENCY MEDICINE C E R T I F I C AT E Sepsis Key concept! Covered in more detail in sepsis module Distributive Shock Neurogenic Dysregulation of autonomic nervous system due to injury Anaphylactic Widespread vasodilation due to histamine release from mast cells EMERGENCY MEDICINE C E R T I F I C AT E Dysregulation of autonomic nervous system due to injury Typically occurs with injury at or above T6 Neurogenic Shock Decreased sympathetic outflow leads to… Decreased vascular tone  hypotension (common) Unopposed vagal stimulation of heart  bradycardia (less common, late) Management strategy Fluid resuscitation to ensure vascular repletion Initiation of vasopressors If hypotensive and normal HR  norepinephrine If hypotensive and bradycardic  dopamine or epinephrine EMERGENCY MEDICINE C E R T I F I C AT E Anaphylaxis “Anaphylaxis is a serious reaction causing a combination of characteristic findings, and which is rapid in onset and may cause death. It is usually due to an allergic reaction, but can be non-allergic” EMERGENCY MEDICINE C E R T I F I C AT E Anaphylaxis Mechanism Typically IgE mediated IgE stimulation of mast cells  activation and degranulation Mast cells release histamine, proteases Stimulates de novo synthesis of leukotrienes, prostaglandins, cytokines EMERGENCY MEDICINE C E R T I F I C AT E Anaphylaxis Signs and Symptoms Constellation of symptoms including… Skin or mucosa Pruritus, flushing, hives, angioedema Respiratory compromise Dyspnea, wheeze, bronchospasm, reduced peak expiratory flow, stridor, hypoxemia Reduced BP or end organ dysfunction Collapse, syncope, incontinence Persistent GI symptoms Vomiting, abdominal pain, diarrhea EMERGENCY MEDICINE C E R T I F I C AT E Diagnosis of Anaphylaxis Three ways to diagnose anaphylaxis Skin/mucosa involvement and… Respiratory compromise OR hemodynamic instability 2 or more of the following occur rapidly after exposure to likely allergen Skin/mucosa involvement, respiratory compromise, hemodynamic instability, or GI symptoms After exposure to known allergen for that patient Hemodynamic instability EMERGENCY MEDICINE C E R T I F I C AT E Management of Anaphylaxis EPINEPHRINE!!! No contraindications to epinephrine in the treatment of anaphylaxis Alpha-1 effects counteract vasodilation Beta-1 effects increase heart rate and cardiac contractility Beta-2 effects dilate the airways and reduce further mass cell degranulation Other agents are adjuncts to epinephrine in anaphylaxis EMERGENCY MEDICINE C E R T I F I C AT E Management of Anaphylaxis Epinephrine dosing and administration 0.5 mg IM epinephrine (1:1000, 1 mg/mL) every 5-15 minutes as needed 0.01 mg/kg/dose, max. of 0.3 mg for pediatrics, 0.5 for adults IM administration in anterolateral aspect of the thigh preferred If unresponsive to IM epinephrine IV fluids IV epinephrine infusion If unresponsive to IV epinephrine and beta blocker suspected Consider IV glucagon infusion EMERGENCY MEDICINE C E R T I F I C AT E Adjunct Medications in Anaphylaxis After epinephrine has been administered, consider adding… Antihistamines H1 blocker such as diphenhydramine H2 blocker such as famotidine Corticosteroids EMERGENCY MEDICINE C E R T I F I C AT E Obstructive Shock Occurs due to an obstruction of blood flow or cardiac wall motion Cardiac tamponade Tension pneumothorax Inferior vena cava compression in pregnancy Pulmonary embolism Fluid resuscitation and vasopressors rarely helpful Requires correction of the obstruction EMERGENCY MEDICINE C E R T I F I C AT E Cardiogenic Shock Acute decompensated heart failure Covered elsewhere… EMERGENCY MEDICINE C E R T I F I C AT E Choose fluids wisely Different fluids distribute differently Resuscitation strategy depends on indication Conclusions Choose vasopressors wisely Consider patient presentation, hemodynamic parameters Pharmacodynamic effects stem from pharmacologic activity EMERGENCY MEDICINE C E R T I F I C AT E