Circulatory shock It is a syndrome characterized by serious reduction of tissue perfusion with inadequate cardiac output. Shock is a condition characterized by inadequate delivery of oxygen and nutrients to critical organs such as heart, brain, liver, kidney and GIT. Types and causes of shock Depending upon cause of inadequate cardiac output the circulatory shock is divided into 4 types: Hypovolaemic shock Vasogenic shock Cardiogenic shock Obstructive shock
1. Hypovolaemic shock: It occurs due to low blood volume resulting in decreased cardiac output. Depending on causes this shock is divided into following types: Haemorrhagic shock: result as a internal or external blood loss due to ruptured blood vessels. Dehydration shock: due to dehydration circulatory blood volume reduces. Traumatic shock: trauma or injury which produce severe pain which inhibits vasomotor center in medulla oblongata.
2. Vasogenic shock: It occurs due to toxic substances released by pathogens which leads to excessive vasodilation within the vessels. Depending upon causes vasogenic shock is divided in to following types: Neurogenic shock: occurs when nerves decreases sympathetic vasomotor tone and increase in vagal tone. Anaphylactic shock: it refers to acute allergic reaction in which large quantities of histamine releases. This histamine causes vasodilation of blood vessels leads to shock. Septicaemic shock: it is a condition in which bacteria circulate and multiply in the blood and form toxic products and cause high fever and vasodilation.
3. Cardiogenic shock: It occurs due to decreased pumping ability of the heart because of cardiac abnormality. Causes of this shock are: Myocardial Infarction Cardiac arrhythmia Congestive Cardiac Failure
4. Obstructive shock: It occurs due to impairment of ventricular filling during diastole due to some external pressure on the heart. Due to decreased ventricular filling stroke volume and hence cardiac output decreases. Causes of this shock are: Pericardial cardiac temponade means bleeding into the pericardium with external pressure on the heart. Pulmonary embolism: embolus formation occurs in the pulmonary vein so that no blood reaches to left heart.
Stages and clinical features of the shock: Depending upon severity circulatory shock is divided into 3 categories: First stage or non-progressive shock:it is also known as compensatory shock in which body try to compensate the loss of blood to vital organs with few mechanisms like: Rapid compensatory mechanism – baroreceptor reflex, chemoreceptor reflex, CNS ischemic response. Inter-mediate compensatory mechanism – renin angiotensin system, capillary fluid shift mechanism Long term compensatory mechanism – restoration of plasma volume and proteins, restoration of red cell mass. 2.Second stage or progressive shock: here compensatory mechanisms are not able to stop progression of shock and some positive feedback mechanism occurs which can lead to serious damage. 3. Third stage or irreversible shock: all treatment becomes ineffective and patient dies due to severe tissue damage to the vital organs of the body.
Treatment of shock General treatment: Patient should be kept in cold because exposed to warmth can cause sweating which can lead to hypovolemia and aggravate shock. Raising foot end of the patient bed by 6 to 12” which helps in promoting venous return and cardiac output increases. Replacement therapy: In hemorrhagic shock and burns whole blood or plasma or plasma substitute like dextran can be transfused. In hypovolemic shock due to dehydration balanced electrolyte solution (Intravenous Ringer Lactate solution) can be given. Sympathomimetic drugs: Helpful in neurogenic and anaphylactic shock where either sympathetic tone is low or vasodilation is present. Drugs like dopamine should be used if it is not available epinephrine and norepinephrine can also be used. Oxygen therapy: Little bit helpful because it relieves hypoxia