david i driver basics of shock

8/7/2019 David i Driver Basics of Shock

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Overview:Overview: Shock (in adults)Shock (in adults)

By:By:David I. Driver, MS IIIDavid I. Driver, MS III


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IntroductionIntroduction

Shock is a physiologic state characterized by asignificant, systemic reduction in tissue perfusion,thereby resulting in decreased tissue oxygen delivery.

Prolonged oxygen deprivation leads to generalized

cellular hypoxia and the derangement of criticalbiochemical processes: Cell membrane ion pump dysfunction

Intracellular edema

Leakage of intracellular contents into the extracellular space Inadequate regulation of intracellular pH

High Mortality Hypovolemic 35-40%

Cardiogenic 60-90%


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Stages of ShockStages of Shock

The shock syndrome is characterized by a temporalcontinuum of physiologic stages beginning with an

initial inciting event which causes a systemic circulatorydisturbance; shock may subsequently progress throughthree stages, culminating in irreversible end-organdamage and death.

Preshock

Shock

End-organ dysfunction


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Stages of Shock IIStages of Shock II

Preshock Preshock is also known as warm shock or compensated shock. During

this stage, the body's homeostatic mechanisms rapidly compensate fordiminished perfusion. Despite a 10 percent reduction in total effectiveblood volume, for example, a previously healthy adult may beasymptomatic.

Shock During this stage, the regulatory mechanisms are overwhelmed and signs

and symptoms of organ dysfunction appear, including tachycardia,tachypnea, metabolic acidosis, oliguria, and cool and clammy skin.

End-organ dysfunction During this stage, progressive end-organ dysfunction leads to irreversible

organ damage and death: Urine output may decline, culminating in anuria.

Restlessness evolves into agitation, obtundation, and coma.

Acidosis further decreases cardiac output and alters cellular metabolicprocesses.

Multiple organ system failure proceeds to cause the demise of the patient.


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Physiologic DeterminantsPhysiologic Determinants

Global tissue perfusion is determined bysystemic vascular resistance (SVR) and cardiac

output (CO) SVR is governed by vessel length, blood viscosity,

and the inverse of vessel diameter.

CO is the product of heart rate and stroke volume;

in turn, stroke volume depends upon preload,myocardial contractility, and afterload (impedance toblood flow).


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Classification of ShockClassification of Shock

Any classification scheme simplifies the complexpathophysiology underlying the many individual causes

of shock states. Three broad types of shock states are recognized. Each

type is characterized by one primary physiologicderangement:

Hypovolemic

Cardiogenic

Distributive or vasodilatory


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Hypovolemic ShockHypovolemic Shock

Hypovolemic shock results from decreased preload.

Two broad etiology based categories:

Hemorrhage

trauma, upper and lower gastrointestinal bleeding, ruptured aortic orventricular aneurysm, ruptured hematoma, hemorrhagic pancreatitis,and fractures.

Fluid loss diarrhea, vomiting, heat stroke, inadequate repletion of insensible

losses, burns, and "third spacing"


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Distributive (vasodilatory) ShockDistributive (vasodilatory) Shock Distributive or vasodilatory shock results from a severe decrease

in SVR, often associated with an increased cardiac output. Septic shock

Activation of the systemic inflammatory response

Toxic shock syndrome Anaphylaxis and anaphylactoid reactions

Drug or toxin reactions, including insect bites, transfusion reactions, andheavy metal poisoning

Addisonian crisis

Myxedema coma Neurogenic shock after a central nervous system or spinal cord injury

Some patients after acute myocardial infarction who develop cardiogenicshock accompanied by a systemic inflammatory state

Post-cardiopulmonary bypass


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Cardiogenic ShockCardiogenic Shock

Cardiogenic shock results from pump failure,manifested physiologically as decreased systolic

function and cardiac output. Four broad categories:

Myopathic

Arrhythmic Mechanical

Extracardiac (obstructive)


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Common Features of ShockCommon Features of Shock

The clinical presentation of shock varies both with thetype and the cause, but several features are very

common. Assessment for each of the following fivemajor features should be done immediately in anypatient suspected of developing shock. Hypotension

Cool, clammy skin

Oligouria

Change in mental status

Metabolic acidosis


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Initial ExamInitial Exam

History The patient rarely provides any history; instead, historical data are usually

obtained from relatives or available medical records. The patient's general

condition, recent complaints, and activities prior to presentation may holdvaluable information about the primary cause of shock.

Physical Exam The physical examination should be performed rapidly and efficiently,

with efforts directed toward uncovering the most likely causes of shock.

Labs laboratory tests helps to identify potential causes for shock and early signs

of organ failure


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Pulmonary Artery CatheterizationPulmonary Artery Catheterization

Pulmonary artery catheterization is frequently

used to provide hemodynamic measurements in

shock patients, including CO, pulmonary arterywedge (pulmonary capillary wedge) pressure,and SVR. These values may help distinguish

which type of shock is affecting a patient andcan aid in identifying a specific diagnosisamongst an extensive differential.


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ReferencesReferences

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17. Hochman, JS. Cardiogenic shock complicating acute myocardial infarction: expanding the paradigm. Circulation 2003; 107:2998. 18. Bouachour, G, et al. Hemodynamic changes in acute adrenal insufficiency. Intensive Care Med 1994; 20:138. 19. Levraut, J, Ciebiera, JP, Chave, S, et al. Mild hyperlactatemia in stable septic patients is due to impaired lactate clearance rather than overproduction. Am

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20. Mimoz, O, et al. Pulmonary artery catheterization in critically ill patients. Crit Care Med 1994; 22:573. 21. Robin, ED. The cult of the Swan-Ganz catheter. Overuse and abuse of pulmonary flow catheters. Ann Intern Med 1985; 103:445.

22. Connors, AF Jr, Speroff, T, Dawson, NV, et al. The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORTInvestigators. JAMA 1996; 276:889.

23. Harvey, S, Harrison, DA, Singer, M, et al. Assessment of the clinical effectiveness of pulmonary artery catheters in management of patients in intensivecare (PAC-Man): a randomised controlled trial. Lancet 2005; 366:472.

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david i driver basics of shock

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