Shock

Shock is defined as a state of cellular and tissue hypoxia due to either reduced oxygen delivery, increased oxygen consumption, inadequate oxygen utilization, or a combination of these processes.

Shock is the state in which the oxygen and metabolic demands of the body are not met by the cardiac output.

Classification of shock 

1.Cardiogenic shock :- 

2.Hypovolemic shock

3.Distributive shock 

a.Neurogenic shock 

b.Anaphylactic shock 

c.Septic shock 

Stages of shock :- 

1.Compensatory stage :- 

• When arterial pressure and tissue perfusion are reduced, compensatory mechanisms are activated to maintain perfusion to the heart and brain.
•  As the baroreceptors in the carotid sinus and aortic arch sense a drop in blood pressure, epinephrine and norepinephrine are secreted to increase peripheral resistance, blood pressure, and myocardial contractility. 
• Reduced blood flow to the kidney activates the renin-angiotensin-aldosterone system, causing vasoconstriction and sodium and water retention, leading to increased blood volume and venous return. 
• As a result of these compensatory mechanisms, cardiac output and tissue perfusion are maintained.

2.Progressive stage:- 

• This stage of shock begins as compensatory mechanisms fail to maintain cardiac output. 
• Tissues become hypoxic because of poor perfusion. 
• As cells switch to anaerobic metabolism, lactic acid builds up, producing metabolic acidosis. 
• This acidotic state depresses myocardial function. 
• Tissue hypoxia also promotes the release of endothelial mediators, which produce vasodilation and endothelial abnormalities, leading to venous pooling and increased capillary permeability
• Sluggish blood flow increases the risk of disseminated intravascular coagulation.

3.Irreversible (refractory) stage :-

• As the shock syndrome progresses, permanent organ damage occurs as compensatory mechanisms can no longer maintain cardiac output. 
• Reduced perfusion damages cell membranes, lysosomal enzymes are released, and energy stores are depleted, possibly leading to cell death. 
• As cells use anaerobic metabolism, lactic acid accumulates, increasing capillary permeability and the movement of fluid out of the vascular space. 
• This loss of intravascular fluid further contributes to hypotension. 
• Perfusion to the coronary arteries is reduced, causing myocardial depression and a further reduction in cardiac output. Eventually, circulatory and respiratory failure occur. 
• Death is inevitable.

Diagnostic Evaluation :- 

• Blood,urine and sputum culture 
• Coagulation study
• Blood test
• ABG analysis
• Urine test
• Chest X-Ray
• Electrocardiography
• Echocardiography

MANAGEMENT FOR SHOCK 

• Maintains A,B,C 
• Supplemental oxygen 
• Continuous cardiac monitoring to detect change in heart rate and rhythm , administration of antiarrhythmics.
• Initiating and maintaining at least two iv lines with large gauge needles for fluid and drug administration b
• IV fluids ,crystalloids ,colloids or blood products as necessary to maintain iv volume.

HYPOVOLEMIC SHOCK :- 

Hypovolemic shock occurs from inadequate fluid volume in the intravascular space .The lack of adequate circulating volume to decreased tissue perfusion of general shock response .

Causes 

1. Loss of whole blood due to trauma ,surgery, gastrointestinal bleeding

2.Loss of plasma :thermal injuries ,large lesions

3.Loss of other body fluids :severe vomiting,severe diarrhoea, massive diuretics

4.Loss of intravascular integrity

5. Increased capillary membrane permeability

6.Decreased colloid osmotic 

Pathophysiology 

Clinical manifestation :- 

• Decreased preload
• Decreased stroke volume
• Tachypnea lead bradypnea 
• Decreased urine output
• Pallor 
• Cool,clamy
• Anxiety
• Confusion

Management 

• Pneumatic antishock garments ,although controversial which may be applied to control both internal and external hemorrhage by direct pressure.
• Fluids such as normal saline or lactated Ringers solutions initially to restore filling pressure
• Packed RBCs in hemorrhagic shock to restore blood loss and improve oxygen carrying capacity of the blood 

CARDIOGENIC SHOCK 

Cardiogenic shock is the result of failure of the heart to pump blood forward effectively.it can occur with dysfunction of either the right or left ventricle or both .the lack of adequate pumping function leads to decreased cardiac output and decreased tissue perfusion.

CAUSES 

• Acute MI
• Cardiopulmonary arrest
• Open heart surgery structural problem
• Septal rupture 
• Ventricular aneurysm
• Intracardiac tumor 
• Cardiac tamponade dysrhythmias
• Valvular dysfunction

Clinical manifestations 

• Heart rate >100bpm
• Weak thready pulse 
• Diminished heart sound 
• Chnage in sensorium 
• Dysrhythmias
• Decreased cardiac output

Management

• Ionotropic drugs such as dopamine,dobutamine ,amrinone ,and epinephrine to increase contractility of the heart and increase cardiac output .
• Vasodilator such as nitroglycerin or nitroprusside given with a vasopressor to reduce the workload of left ventricule.
• Diuretics to reduce preload if patiet has fluid volume overload 
• Intraaortic balloon pump therapy to educe the work of the left ventricle by decreasing systematic vascular resistance . diastolic pressure is increased resulting in improved coronary artery perfusion.
• Thrombolytic therapy or coronary artery revascularization to restore coronary artery blood flow if cardiogenic shock is due to acute myocardial infarction.

ANAPHYLACTIC SHOCK 

Anaphylactic shock a type of distributive is the result of an immediate hypersensitivity reactions .it is a life threatening event that requires prompt intervention .

Cause 

• Foods such as :- Egg and milk ,fish and fish oil, chocolate nuts and seeds

 

• Food additives :- Food colouring , preservatives

• Diagnostic agents :- Iodinated contrast dye ,Iopanoic acid

 

• Biologic Agent :- Blood and blood components , insulin seminal plasma ,vaccines and antitoxins

• Drugs :- Antibiotics, aspirin,narcotics ,local anaesthesia

• Venoms :- Bees and wasps ,snakes ,jelly fish ,spider 

Pathophysiology 

Clinical manifestations 

• Hypertension
• Tachycardia
• Lump in throat 
• Stridor 
• Wheezing 
• Rhonchi sound
• Restlessness
• Nausea
• Vomiting

Management 

1. Preservation and support of airway and ventilation

2.Intubation

3.Bronchodilator

NEUROGENIC SHOCK 

Neurogenic shock a type of distributive shock is the result of the loss of suppression of sympathetic tone it onset occurs within minutes and it may last for days ,weeks or month depending on the cause .

Causes 

1 .Spinal cord injury above level of T6 this is known as spinal shock 

2. Spinal anaesthesia drugs 

3.Emotinal stress 

4.Pain and central nervous system dysfunction

Pathophysiology

Clinical manifestations

1.Hypotension 

2.Bradycardia 

3.Hypothermia 

4.Warm ,dry skin

5.Decreased heart rate 

6.Flaccid and paralysis

7. Loss of reflex activity

8. Bowel dysfunction

Management

1.Vasopressor drugs to raise blood pressure by vasoconstriction

2. Fluid replacement to maintain blood pressure and cardiac output.

SEPTIC SHOCK 

Septic shock is the form of distributive shock occurs when microorganisms invade the body .

Causes

 

Septic shock is caused by a wide variety of microorganisms including gram negative and gram positive aerobes ,anaerobes ,fungi and viruses.

Precipitating factors 

• Intrinsic factors 

1.Extreme of age 

2.Coexisting disease such as malignancies ,burns ,AIDS , diabetes,substance abuse 

3.Malnutrition

• Extrinsic factors

1. Invasive device 

2.Drug therapy 

3.Fluid therapy

4.Surgical and traumatic wounds 

Pathophysiology 

Management

1.Antibiotic therapy to eradicate the causative organism

2.Inotropic and vasopressor drugs such as dopamine, dobutamine,and norepinephrine,to improve perfusion and maintain blood pressure