SHOCK

Lecture - 12Lecture - 12

DR ZAHOOR ALI SHAIKHDR ZAHOOR ALI SHAIKH

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We will discuss SHOCK under the following headings - DEFINATION - CLASSIFICATION - CLINICAL PRESENTATION - COMPENSATORY MECHANISM BY BODY - STAGES OF SHOCK - TREATMENT

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Define Circulatory ShockWhen Blood Pressure falls so low that there is

inadequate tissue perfusion(less blood flow to tissues) therefore decreased oxygen supply with inadequate cardiac output.

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Types of Shock- Hypovolemic shock- Septic shock- Anaphylactic shock- Neurogenic shock- Cardiogenic shock

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GENERAL MECHANISM

HYPOVOLEMIC SHOCKWe will discuss in detail HYPOVOLEMIC

SHOCKIt is also called COLD shock

Causes of Hypovolemic shock(Decreased Blood volume) Hemorrhage Surgery Trauma Burns ( loss of plasma ) Fluid loss e.g.: Vomiting, Diarrhea

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Signs of Hypovolemic shock

Patient is paleCold clamy skin

Hypotension

Increased pulse rate

Increased respiratory rate

(Vasoconstriction due to increased sympathetic stimulation )

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Sweating

Increased thirst

Decreased urinary output

Metabolic Acidosis

Restlessness

Signs of Hypovolemic shock--- Continued

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Clinical Presentation

Hemorrhagic ShockHemorrhagic Shock is hypovolemic shock

due to blood loss There is decreased venous return and

decreased cardiac output.Inadequate perfusion of the tissues leads to

Anaerobic glycolysis therefore increased production of lactic acid.

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Compensatory ReactionsCompensatory Reactions Activated By

Hemorrhage (Blood Loss)Rapid compensatory reaction ---

Barorecepreflex—when BP is decreased Increased secretion of norepinephrine and

ephinephrine ( vasoconstriction,tachycardia) Increased secretion of vasopressin(ADH) Increased Renin-Angiotensin-Aldosterone

mechanism

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Compensatory Mechanism----cont

Increased secretion of Glucocorticoids

Extra-cellular Fluid shift from Interstitial fluid

to plasma to increase Plasma volume

Over a longer period [1 week] there is

- Increased secretion of Erythropoietin

- Increased synthesis of plasma protein

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Stages of Shock1. Non progessive stage or Compensated stage

Here circulatory compensatory mechnism cause Full recovery without help from outside therapy

2. Progressive stage-Decreased BP AND COP. Here without therapy ,shock gets worse

3. Refractory shock or Irreversible stage (called before) Here patient does not respond to Treament .

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Refractory ShockRefractory Shock

In some patients shock persists for Hours and progresses to a state where there is no response to drugs and COP remains low. Blood pressure continues to drop inspite of therapy. This is called Refractory Shock.

CAUSES:

1.Cerebral ischemia therefore depression of Vasomotor center---vasodilatation , decreased BP, decreased HR

2. Myocardial depression due to Acidosis causes decreased COP

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IMPORTANT NOTEIf 10% of Total Blood volume is lost---There is

no effect on arterial BP andCOP If more than 10% of Blood volume is lost ---

There is decreased arterial BP and COP If 35%-45% of Total Blood volume is lost---

Arterial BP and COP will fall to Zero Therefore depending on Blood loss, some

patients Recover, other may die.

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Hemorrhagic Shock

Parameter I II III IV

Blood loss (ml) <750 750–1500 1500–2000 >2000

Blood loss (%) <15% 15–30% 30–40% >40%

Pulse rate (beats/min) <100 >100 >120 >140

Blood pressure Normal Decreased Decreased Decreased

Respiratory rate (bpm) 14–20 20–30 30–40 >35

Urine output (ml/hour) >30 20–30 5–15 Negligible

CNS symptoms Normal Anxious Confused Lethargic

Crit Care. 2004; 8(5): 373–381.

HYPOVOLUMIC SHOCK

SEPTIC SHOCKUsually due to gram-negative bacteria Endotoxins released by gram-negative

Bacteria—cause VASODILATATION(Skin is warmTherefore called WARM SHOCK).

High fever Increased capillary permeability with loss of

plasma in tissues Mortality is 30-50%

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Causes of Septic shock Bacterial Infection

--Trauma– wound infection --Diabetes Mellitus-Gangrene --Abortion- septic

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GENERAL MECHANISM

ANAPHYLACTIC SHOCKDue to Allergic reaction to Drugs eg pencillin

injection, Vaccine, Food allergyThere is antigen-antibody reaction,large

quantities of Histamine are released causing

Vasodilatation therefore decreased BP

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Anaphylactic Shock Cont….Decreased venous return(due to increased

vascular capacity)Increased capillary permeability,therefore

loss of fluid.Sometimes decreased venous return can

cause death in minutes

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Cardiogenic shockCause---Myocardial Infarction(pump failure)Causes symptoms of shock and congestion in

the lungs ( Pulmonary oedema).Note—In Myocardial Infarction, shock occurs

in 10% and has mortality of 60-90%.

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GENERAL MECHANISM

Neurogenic shockIn Neurogenic shock, there is decreased

sympathetic activity, therefore, increased vascular capacity.

Reason—Sudden loss of Vasomoter Tone resulting in massive dilation of veins therefore Venous pooling of blood and decreased venous return to heart.

Causes of Neurogenic shock -General Anesthesia, Spinal Anesthesia -Brain damage

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Fainting and SyncopeFainting--Feeling of dizziness due to

decreased cerebral perfusion but not sufficient to cause loss of consciousness.

Syncope—Temporary impairment of consciousness due to reduction in cerebral blood flow

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Vasovagal FaintingVasovagal attacks---Increased Vagal

activity,ANS Disturbance-- It causes vasodilatation therefore pooling of

blood in extermities and Fainting.

--Bradycardia--It is short lived and Benign.Cause---Fear, Pain

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Other Form of SyncopePostural Syncope

- Pooling of blood in legs on standing

Carotid sinus syncope- Pressure on carotid sinus due to Tight Collar causes Vasodilatation and Bradycardia, that causes

Fainting.

Cough syncope - Due to increased Intrathoracic pressure there

is decreased venous return

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Physiology of Treatment in Shock

Treat the cause

Hemorrhagic shock---Give Blood Transfusion

Burn shock----Plasma Transfusion

Fluid loss(vomting and Diarrhea)—I/V Fluids

(0.9%Saline)

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Physiology of Treatment in Shock Cont … Anaphylatic shock—Epinephrine,Antihistamine

Septic shock– Antibiotics

Other Therpy Eg: Vasovagal syncope—Put the

patient in supine position,raise the foot end of the

bed

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THANK YOU

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