shock

ShockDr. Deepak K. Gupta

Introduction

• Shock is a life-threatening clinical syndrome of cardiovascular collapse.

• Its characterised by:– an acute reduction of effective circulating blood

volume (hypotension);– Leading to an inadequate perfusion of cells and

tissues (hypoperfusion).

• These two effect initially causes only reversible cellular injury,

• But persistence of shock eventually causes irreversible tissue injury and may cause death

www.facebook.com/notesdental

Classification

• Based on etiology shock can be classified into– Hypovolaemic shock– Cardiogenic shock

• Deficient emptying• Deficient filling• Obstruction to the outflow

– Septic (Toxaemic) shock• Gram-negative septicaemia• Gram-positive septicaemia

– Other types• Traumatic shock• Neurogenic shock• Hypoadrenal shock


Pathophysiology

• All forms of shock involve following

– Reduced effective circulating blood volume.

– Reduced supply of oxygen to the cells and tissues with resultant anoxia.

– Inflammatory mediators and toxins released from shock induced cellular injury


PATHOGENESIS OF HYPOVOLAEMIC SHOCK

• Inadequate circulating blood volume due to various causes.– Acute haemorrhage– Dehydration from vomitings, diarrhoea– Burns– Excessive use of diuretics– Acute pancreatitis

• It may be again classified into 4 types, depending on the amount of blood loss– < 1000 ml: Compensated– 1000-1500 ml: Mild– 1500-2000 ml: Moderate– >2000 ml: Severe


PATHOGENESIS OF CARDIOGENIC SHOCK

• Results from failure of the cardiac pump - severe left ventricular dysfunction.

• This may be due to – Deficient emptying

• Myocardial infarction• Cardiomyopathies• Rupture of the heart, ventricle or papillary muscle• Cardiac arrhythmias

– Deficient filling: Cardiac temponade– Obstruction to the outflow

• Pulmonary embolism• Ball valve thrombus• Tension pneumothorax• Dissecting aortic aneurysm


PATHOGENESIS OF SEPTIC SHOCK

• Results from the host innate immune response to infectious organisms that may be blood borne or localized to a particular site– Most commonly due to gram-negative infections

(endotoxic shock) – 70 %• bacterial wall lipopolysaccharides (LPS) consisting of a toxic

fatty acid (lipid A) – common for all gram(+)

• complex polysaccharide coat (including O antigen) unique for each species

– But it can also occur with gram-positive (exotoxic shock) and fungal infections.• Analogous molecules in the walls



• Various immunological events takes place

– Activation of macrophage-monocytes

– Activation of other inflammatory responses.

• Complement pathway

• Mast cells

• Coagulation system

• Kinin system


PATHOGENESIS OF OTHER TYPES OF SHOCK

• Traumatic shock– Severe injuries– Surgery with marked blood

loss– Obstetrical trauma

• Neurogenic shock– High cervical spinal cord

injury– Accidental high spinal

anaesthesia– Severe head injury

• Hypoadrenal shock– Administration of high

doses of glucocorticoids– Secondary adrenal

insufficiency (e.g. in tuberculosis, metastatic disease, bilateral adrenal haemorrhage, idiopathic adrenal atrophy).

• Anaphylactic shock– systemic vasodilation– increased vascular

permeability– caused by an Ig E

hypersensitivity reaction


STAGES OF SHOCK


References

• Robbinson's basic pathology 8 ed

• Harsh Mohan - Textbook of Pathology 6th Ed.

• Color atlas of pathology


shock

Health & Medicine