Shock

Differential Diagnosis and Hemodynamic Monitoring

Andrew Watt

SICU CONFERENCE

ShockShock is a Cardiovascular Derangement.

1. Deliver Oxygen and Metabolic Substrates

2. Remove Products of Cellular Metabolism

3. Thermoregulation

Definition:

A physiological state characterized by a significant, systemic reduction in tissue perfusion, resulting in decreased tissue oxygen delivery and insufficient removal of cellular metabolic products, resulting in tissue injury.

Classification of Shock

•Hypovolemic

•Septic/Inflammatory

•Cardiogenic (Intrinsic, compressive & Obstructive)

•Neurogenic

•Anaphylactic

Clinical Markers of Shock

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•Brachial systolic blood pressure: <110mmHg

•Sinus tachycardia: >90 beats/min

•Respiratory rate: <7 or >29 breaths/min

•Urine Output: <0.5cc/kg/hr

•Metabolic acidemia: [HCO3]<31mEq/L or base deficit>3mEq/L

•Hypoxemia: 0-50yr: <90mmHg; 51-70yr: <80mmHg; >71yo<70mmHg;

•Cutaneous vasoconstriction vs. vasodilation.

•Mental Changes: anxiousness, agitation, indifference, lethargy, obtundation

Etiology & Hemodynamic Changes in Shock

Etiology of shock

example CVP CO SVR VO2 sat

preload hypovolemic low low high low

contractility cardiogenic high low high low

afterload distributive

Etiology & Hemodynamic Changes in Shock (Afterload)

ETIOLOGY OF SHOCK

EXAMPLE CVP CO SVR VO2 SAT

AFTERLOAD DISTRIBUTIVE

Hyperdynamic Septic Low/High High Low High

Hypodynamic Septic

Low/High Low High Low/High

Neurogenic Low Low Low Low

Anaphylactic Low Low Low Low

Hypovolemic Shock

•Decreased preload->small ventricular end-diastolic volumes -> inadequate cardiac generation of pressure and flow

•Causes:

-- bleeding: trauma, GI bleeding, ruptured aneurysms, hemorrhagic pancreatitis

-- protracted vomiting or diarrhea

-- adrenal insufficiency; diabetes insipidus

-- dehydration

-- third spacing: intestinal obstruction, pancreatitis, cirrhosis

Hypovolemic Shock• Signs & Symptoms: Hypotension, Tachycardia, MS

change, Oliguria, Deminished Pulses.

• Markers: monitor UOP,CVP, BP, HR, Hct, MS, CO, lactic acid and PCWP

• Treatment: ABCs, IVF (crystalloid), Trasfusion Stem ongoing Blood Loss

• Patients on β-blockers, w/ spinal shock & athletes may not be tachycardic

Septic/Inflammatory Shock

Mechanism: release of inflammatory mediators leading to

1. Disruption of the microvascular endothelium

2. Cutaneous arteriolar dilation and sequestration of blood in cutaneous venules and small veins

Causes:

1. Anaphylaxis, drug, toxin reactions

2. Trauma: crush injuries, major fractures, major burns.

3. infection/sepsis: G(-/+ ) speticemia, pneumonia, peritonitis, meningitis, cholangitis, pyelonephritis, necrotic tissue, pancreatitis, wet gangrene, toxic shock syndrome, etc.

Septic/Inflammatory ShockSigns: Early– warm w/ vasodilation, often adequate urine output, febrile, tachypneic. Late-- vasoconstriction, hypotension, oliguria, altered mental status.

Monitor/findings: Early—hyperglycemia, respiratory alkylosis, hemoconcentration, WBC typically normal or low. Late – Leukocytosis, lactic acidosis Very Late– Disseminated Intravascular Coagulation & Multi-Organ System Failure.

Tx : ABCs, IVF, Blood cx, ABX, Drainage (ie abscess) pressors.

Cardiogenic ShockMechanism: Intrinsic abnormality of heart -> inability to deliver blood into the vasculature with adequate power

Causes:

1. Cardiomyopathies: myocardial ischemia, myocardial infarction, cardiomyopathy, myocardiditis, myocardial contusion

2. Mechanical: cardiac valvular insufficiency, papillary muscle rupture, septal defects, aortic stenosis

3. Arrythmias: bradyarrythmias (heart block), tachyarrythmias (atrial fibrillation, atrial flutter, ventricular fibrillation)

4. Obstructive disorders: PE, tension peneumothorax, pericardial tamponade, constrictive pericaditis, severe pulmonary hypertension

Cardiogenic Shock

• Characterized by high preload (CVP) with low CO• Signs/SXS: Dyspnea, rales, loud P2 gallop, low BP,

oliguria• Monitor/findings: CXR pulm venous congestion, elevated

CVP, Low CO.• Tx: CHF– diuretics & vasodilators +/- pressors. LV failure – pressors, decrease afterload, intraaortic ballon pump & ventricular assist device.

Neurogenic Shock

Causes:

1. Spinal cord injury

2. Regional anesthesia

3. Drugs

4. Neurological disorders

Mechanism: Loss of autonomic innervation of the cardiovascular system (arterioles, venules, small veins, including the heart)

Neurogenic Shock

• Characterized by loss of vascular tone & reflexes.

• Signs: Hypotension, Bradycardia, Accompanying Neurological deficits.

• Monitor/findings: hemodynamic instability, test bulbo-carvernous reflex

• Tx: IVF, vasoactive medications if refractory

Monitoring Adjuncts in Shock

• Sphyngomanometry

• Pulse Oximeter

• Arterial Line

• Central Venous Line (Cordice, Triple Lumen, Pulmonary Artery Catheter)

Pulmonary Artery Catheterization

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Allows for accurate and continuous hemodynamic monitoring in shock patients

1. Evaluate Fluid Resuscitation

2. Titration of Vasoactive Medications

3. Allows for Assessment of Cardiovascular

Performance.

4. Monitor the Effects of Changes in Mechanical

Ventilation.

Pulmonary Artery Catheterization

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Pulmonary Artery Catheterization: cardiovascular

performance

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Central Venous Pressure (CVP):

CVP = right atrial pressure (RAP) = right-ventricular end-diastolic pressure (RVEDP) (Right Ventricular Preload)

Pulmonary Capillary Wedge Pressure (PCWP)

PCWP = left atrial pressure (LAP) = left-ventricular end-diastolic pressure (LVEDP) (Left Ventricular Preload)

Cardiovascular Performance

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Cardiac Output (CO) = HR x SV (L/min)Normal CO = 4 to 8 L/min

Cardiac Index (CI) = CO/BSA (L/min/m2) Normal CI = 2.5-4.2 L/min/m2

Stroke Volume Index (SVI): CI/HR (ml/beat/m2)

Normal SVI = 40-85 ml/beat/m2

Systemic Vascular Resistance = MAP – CVP / CO x 80 Normal SVR = 900-1600 dynes/sec/cm-5

Systemic Vascular Resistance Index = MAP – CVP / CI x 80 Normal SVRI = 1970-2390 dynes/sec/cm-5

Pulmonary Artery Catheterization: systemic oxygen

transport

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Oxygen Delivery (DO2) [520-570 mL/min x m2]: rate of oxygen transport in arterial blood

DO2= CI x 13.4 x Hb x SaO2

Oxygen Uptake (VO2) [110-160 ml/min x m2]: rate of oxygen taken up from the systemic microcirculation

VO2 = CI x 13.4 x Hb x (SaO2 – SvO2)

Hemodynamic Profiles

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PCWP CVP CO/CI SVR/I

Hypovolemic Low Low Low High

Cardiogenic High High Low High

Inflammatory Low / N Low/N High Low

Neurogenic Low Low Low Low

Shock