Overview of Shock

Lecturer: Michelle Hodgkiss2008

Aims of the Session

• Definition• Classification• Factors leading to the progression of shock

and tissue hypoperfusion• Description and discussion of the four

stages of shock• Assessment & systematic review• Overview and treatment of Shock

Definition of Shock“Shock is a condition in which the

cardiovascular system is no longer able to meet the body's metabolic and oxygen

needs. Note that this definition does notinclude blood pressure limits. Although

many practitioners believe that shock exists when the systolic blood pressure falls

below 80 mmHg, some patients will still be able to maintain relatively normal

metabolic function below this level.”Trauma Secrets 2nd ed 2003.

Shock

…Is potentially life threatening it can affect many organs and must be

reversed. Nurses need to be alerted to initial signs of shock to allow early intervention of treatment, prevent

deterioration or death.

Events leading to inadequate tissue perfusion

• Decreased cardiac output• Decreased blood volume• Pump failure• An increase in peripheral vasodilatation• Increased vascular permeability

Shock

Patient assessment

Accurate interpretationof situation

InstigateImmediate appropriate

action

Factors in the Progression of ShockHypovolaemic Shock Cardiogenic Shock

MIMyocarditis Tamponade

Decreased CO

Decreased Tissue

Perfusion

EndotoxaemiaBurns

TraumaAnaphylaxis

HaemorrhageDiarrhoea

Dehydration

Increased Vascular

permeability

DecreasedBlood

volume

Decreased VenousReturn

Endothelialdamage

AnoxicCell injury

Factors in the Progression of Shock

Decreased CO

Decreased tissue perfusion

Anoxic cellinjury

Metabolicacidosis

Renal Failure

AnaerobicGlycolysis in Muscle

Heart Failure

Four Stages of Shock

• Initial• Compensatory• Progressive• Refractory

Initial Phase

• Cardiac output , tissue perfusion , oxygen delivery and nutrients to cells aerobic metabolism is and anaerobic metabolism begins to take over.

Compensatory Stage

The body tries to overcome these effects with physiological adaptations

Neural Hormonal Chemical

Neural

• As C.O. & BP fall, Baroreceptors in the aorta & carotid arteries send a message to the medulla, stimulating the sympathetic nervous system, the adrenal medulla releases catecholamines – Adrenaline & noradrenaline.

• Increase in myocardial contractility, rate & vasoconstriction

Hormonal

• The sympathetic stimulation:• Renal & spanchnic blood flow decreased• Juxtaglomerular cells in nephron stimulated

to release renin• Renin-angiotensin-aldosterone system

activated.

Chemical

• Increased production of aldosterone by the adrenal cortex

• Increased production of catecholamines by the adrenal medulla

• Increased production of ADH by the pituitary gland

• Effects of acidosis, oxygenation and carbon dioxide.

Progressive Stage

Compensatory mechanisms begin to fail to perfuse vital organs

• Reduced Cardiac Output• Reduced coronary perfusion• Decreased filling pressure• Increased capillary permeability• K+ leaks out of the cells• Metabolic acidosis

Refractory Stage

Severe cell destruction Vital organs failedDeath imminent

Assessing the Shocked Patient

• Skin• Colour• Temperature• Conscious level• Respiratory rate & pattern• Heart rate & BP• Perfusion• Decreased urine output

Classification of Shock

• Hypovolaemic• Cardiogenic• Anaphylactic Shock• Septic Shock• Neurogenic Shock

Classifications of Shock

Hypovolaemic

Distributive

Cardiogenic

SepticNeurogenicAnaphylactic

Hypovolaemic Shock

• CausesCommonly due to sudden blood loss –Burns and Dehydration are the most common

forms of shock• Research of therapies vast

Clinical Findings Associated with Volume Loss

• < 500 mls = none• 500 – 1000 mls = HR, BP, Urine, Resp,

CO =, SVR• 1000 – 2000 mls = As above & worsening, O2

consumption , affected conscious level, skin perfusion, CO , SVR

• 2000 – 3000 mls = as above & worsening anuria, loss of consciousness, pulses, cold, pallor.

Management

• Replace loss• ?Crystalloid vs Colloid vs Blood• O2 Therapy• Observations• Monitor blood results

Cardiogenic shock

Definition“…is the result of the loss of critical contractile

function of the heart”(Hudak & Gallo 1997)

Causes• MI• Tamponade• Cardiomyopathy• Ventricular septal rupture

Cardiogenic Shock

A decrease in CO leads to compensatory measures to restore function. Cardiogenic

shock is a result of the cycle of progressive deterioration. A reduced cardiac output

leads to tissue hypoperfusion & increased myocardial workload leads to lactic acidosis then worsening contractility

Management

• Myocardial and tissue oxygenation• Increase contractility• Minimise risk of extension to injury• Reduce afterload• Possible surgery

Septic Shock

• Development of septicaemia usually bacterial, occasionally viral

• Immune and inflammatory response causing vasodilatation, reduced venous return, reduced cardiac output.

• Increased O2 requirements from anaerobic metabolism

• Cell damage as a result of released endotoxins –capillary permeability

Clinical Presentation

• Initially – may be pyrexial, flushed, tachycardic, tachypnoeic, ? Normal BP or slightly reduced, urine output.

• Cold, clammy, pallid, altered level of consciousness, cyanosed, hypoxic, acidotic, hypotensive, tachycardic, tachypnoeic/reparatory failure, oliguric, anuric

Anaphylactic Shock

An allergic reaction to an allergen.• Hypersensitivity leading to histamine

released causing to increased capillary permeability.

• Severe onslaught• Vasodilatation & reduced cardiac output.

Management

• Hydrocortisone• Adrenaline• Treat cause• Inotropes, fluids, etc

Neurogenic Shock

• Due to lack of neural control• Vasodilatation• As a result of loss of parasympathetic &

sympathetic nervous control

Causes

• Head injury• Spinal injury/shock• Iatrogenic• Pain• Stress/pain

Further reading

• Daily, E. K, & Schroeder,J.S. Techniques in Bedside Hemodynamic Monitoring. 5th Edition.1994. Mosby

• Gideon P. Naude, et al (2003) Trauma Secrets 2nd

Edition. Handley Belfus. Philadelphia.• Hudak & Gallo. CM (1994) Critical Care Nursing:

A Holistic Approach Lippincott Philadelphia

Any questions