shock medical

Shock – Definition, Type, Symptoms & Treatment.

Circulatory shock means generalized inadequacy of blood flow throughout the body to the extent that body tissues get damaged due to too little delivery of oxygen and nutrients.

Different types of shock and their causes.

Shock caused by reduced cardiac output

It is subdivided into:
(a) Cardiogenic shock, due to decreased pumping ability of the heart because of cardiac abnormalities, e.g. myocardial infarction, toxic states of heart, severe heart valve dysfunction, heart arrhythmias.

(b) Shock caused by decreased venous return:
Hypovolumic shock. There is decrease in blood volume due to any cause, e.g. external or internal haemorrhage (injury, fracture), fluid loss diarrhoea, vomiting, excess sweating, burns).

Decrease in vascular tone, especially of venous reservoirs as in —-

– Neurogenic shock, caused by general or spinal anaesthesia, brain damage,
emotional fainting.

– Anaphylactic shock, an allergic reaction which causes marked venous and
arteriolar dilatation and increased capillary permeability due to release of
histamine or histamine like substances.

– Obstructive shock, caused by obstructive blood fl ow, e.g. tension pneumothorax, pulmonary embolism, cardiac tumour, etc.

Shock occurring without decrease in cardiac output.

It is subdivided into:

(a) Excessive metabolism of the body due to which normal cardiac output is

(b) Septic shock. Abnormal tissue perfusion patterns so that most of the cardiac output is passing through blood vessels besides those that are supplying the local tissues with nutrition. It occurs due to blood borne infection, e.g. peritonitis. Usually there is high fever, vasodilation, high cardiac output and sludging of blood in septic shock.

What are signs and symptoms of circulatory shock?

Decreased blood pressure.- Tachycardia and therefore reduced stroke volume. Reduction in velocity of blood flow producing stagnant hypoxia and cyanosis. Pale and cold skin due to vasoconstriction.

Decreased urine output due to reduced renal blood flow and GFR. Blood flow to vital organs is affected. Reduced blood flow to brain causes fainting.

Due to tachycardia there is increase in work of heart but its blood flow is reduced. This leads to excessive production and collection of lactic acid.
Respiration becomes rapid. If patient is conscious, there is intense thirst.
Agitation, restlessness.

Stages of shock

Non-progressive stage (compensated stages). Normal circulatory compensatory mechanisms eventually cause full recovery without help of outside therapy.

Progressive stage. Shock becomes steadily worse until death.

Irreversible stage. Shock progresses to such an extent that all forms of known therapy are inadequate to save person’s life.

CNS ischemic response. When blood pressure falls below 50 mmHg this response is initiated. It causes more powerful sympathetic stimulation.

Reverse stress relaxation.

This causes blood vessels to constrict down around the diminished blood volume so that available blood volume is adequately circulated.

Release of epinephrine and norepinephrine. Hemorrhage is a potent stimulator of secretion of these hormones from adrenal medulla. Th e increase in blood levels of these hormones contribute relatively little to generalized vasoconstriction. They cause stimulation of reticular formation making patient restless and apprehensive.

Increase in circulating angiotensin II level. Due to ischaemia there is a secretion of renin from the kidneys which increases level of angiotensin II in blood.

The First Centre is stimulated which makes person drink more fl uid which helps to restore extracellular fluid (ECF). Increased angiotensin II causes vasoconstriction leading to rise in blood pressure. It also causes increased aldosterone secretion (after about 30 minutes) which in turn causes increased absorption of salt and water by kidneys which helps in restoring
extracellular fl uid volume. All these eff ects help in preventing progression of shock.

Release of excess vasopressin or ADH. Release of ADH causes retention of water by kidneys and helps in restoring ECF.

What is progressive shock?

When shock becomes severe enough structures of circulatory system begin to deteriorate and various types of positive feedback mechanisms develop. This cause vicious cycle of progressively decreasing cardiac output. This is called progressive shock.

What is irreversible shock?

After shock has progressed to a certain stage, transfusion or any other therapy becomes
incapable of saving the life of a person. Th is is irreversible shock.

What is the treatment of circulatory shock?

The treatment of shock is aimed at correcting the cause and helping physiological compensatory mechanisms.

  1. Fluid replacement therapy
    Blood or plasma transfusion. If the shock is due to haemorrhage transfusion of blood is the best therapy. If shock if due to plasma loss, plasma or appropriate electrolytic solution can correct the shock. Plasma substitute such as dextran can be used. Saline. Less effective.
  2. Sympathomimetic drugs
    They mimic sympathetic stimulation. They are most useful in neurogenic and anaphylactic shock. Th ey are not useful in haemorrhagic shock.
  3. Other therapy
    Head low position, Oxygen,
    : They are useful because they increase the strength of heart in last stages of shock, by stabilizing lysosomal membranes they prevent release of enzymes of cells and help in metabolism of glucose by the severely damaged cells.

Read Other posts – Infective Endocarditis-Cardiology

Tags: No tags

One Response

Add a Comment

Your email address will not be published. Required fields are marked *