Word of shock


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Word of shock

  1. 1. A SEMINAR ON “SHOCK” by, Dr.Prasanna Kumar Y.S Post-Graduate student Department of Preventive and Community dentistry
  2. 2. SHOCK… Various attempts to define shock are; “ It is a condition in which circulation fails to meet the nutritional needs of the cells and at the same time fails to remove the metabolic waste products” “ It is a clinical condition characterised by signs and symptoms arising when the cardiac output is insufficient to fill the arterial tree with blood under sufficient pressure to provide all the organs with adequate blood flow” Shock is classified into various types depending on the Causes.They are:  Haematogenic shock  Traumatic shock  Neurogenic shock àVasovagal shock àPsychogenic shock  Cardiogenic shock  Septic shock  Miscellaneous types àAnaphylactic shock àInsulin shock
  3. 3. Haematogenic or Hypovolaemic shock: Pathophysiology: Such shock is usually due to sudden loss of blood volume or loss of fluid from the vascular space.Most common causes include hemorrhage,vomiting and other states of dehydration. In case of hemorrhagic shock there is loss of blood resulting in decreased filling to the right heart. The decreased filling results in an a drop of arterial pressure and thus consequential hypotension. The compensatory mechanisms put forth by the body are: 1.Adrenergic discharge 2. Hyperventilation 3. Release of vasoactive amines 4. Collapse 5. Resorption of fluid from the intracellular and extracellular space 6. Renal conservation of body water and electrolytes 1. ADRENERGIC DISCHARGE It starts within 60 seconds of blood loss.The constriction of venules and small veins displaces blood to the right atrium and ventricle.This causes an increase in the diastolic blood pressure and stroke volume thus compensating the systemic hypotension.
  4. 4. Adrenergic discharge constricts sphincters in the splanchic viscera,kidneys and the skin.This selective vasoconstriction improves filling of the right heart and increases cardiac output. 2.HYPERVENTILATION This occurs in response to metabolic acidaemia that develops shortly after haemorrhage. Spontaneous deep breathing sucks blood from extrathoracic sites to the heart and lungs.This results in increased filling to the left ventricle. “Both adrenergic discharge and hyperventilation occur within one minute of blood loss” 3.RELEASE OF VASOACTIVE AMINES A hormone known as RENIN is released from the kidney in response to low perfusion.Renin releases AngiotensinI from the liver which is converted to Angiotensin II in the lungs.This Angiotensin II is a potential vasoconstrictor. Another hormone of importance is VASOPRESSIN. It is released in response to the stimulation of baroreceptors situated in the Carotid bodies of the aortic arch.It acts as a systemic vasoconstrictor and diverts the blood flow towards the brain and heart increases cardiac output.
  5. 5. EPINEPHRINE is also a vasoactive hormone released from the aderenal medulla as a consequence of discharge from the adrenergic nervous system. “The release of vasoactive amines usually occurs after 1 to 2 minutes of Haemorrhage” 4.COLLAPSE “Assumption of the recumbent posture due to collapse automatically displaces blood from the lower part of the body to the heart and increases cardiac output” 5.RESORPTION OF FLUID FROM THE INTRACELLULAR AND THE EXTRACELLULAR SPACE Release of epinephrine from the adrenal medulla,cortisol from the adrenal cortexand glucagons from the pancrease results in high extracellular glucose concentration.This causes hyperosmolarity of the extracellular tissue which draws water out of the Cells.Interstitial pressure increases as a result water,sodium and chloride are forced into the vascular space. 6.RENAL CONSERVATION OF BODY WATER AND ELECTROLYTES Adrenocorticotropic hormone is release by any stress or shock.This along with AngiotensinII stimulate the synthesis and
  6. 6. release of hormone Aldosterone which helps in resorption of sodium and water by the Kidneys. CLINICAL FEATURES OF HYPOVOLAEMIC SHOCK Based on the degree of loss of blood volume and the duration(time elapsed) the clinical features can be described under 3 Phases.  MILD SHOCK  MODERATE SHOCK  SEVERE SHOCK 1.MILD SHOCK Loss of less than 20% of blood volume is included under this category.The clinical findings include:  Paleness of extremities which become cool-due to peripheral vasoconstriction which in turn is due to theaction of adrenergic discharge  There is sweating in the forehead and palms again due to adrenergic discharge.  Urinary output and pulse rate and BP remain normal  Patient feels thirsty and cold 2.MODERATE SHOCK Loss of blood volume from 20% to 40% is seen. In consistence with the features of mild shock what is seen here is OLIGURIA.
  7. 7. “Oliguria is due to adrenergic discharge along with the effects of circulating aldosterone and vasopressin.” The pulse beats is around 100 beats per min. Initially the BP will be normal but progressively falls later on. 3.SEVERE SHOCK Loss of blood volume more than 40% usually causes this form of shock. Characterized by: 1.Palor(paleness of skin and extrmities) 2.Low urinary output 3.Rapid pulse 4.Low BP CLINICAL MONITORING:  Measurement of BP  By measuring respiratory rate  Urine output  Measuring central venous pressure. TREATMENT 1.RESUSCICATION 2.IMMEDIATE CONTROL OF BLEEDING 3.EXTRACELLULAR FLUID REPLACEMENT - Usually Normal saline supplemented with 1 or 2 ampules of Sodium bicarbonate.
  8. 8. 4.DRUGS-In this case usually only in the form of sedatives. TRAUMATIC SHOCK Pathophysiology: The peculiarity of this type of shock is that the traumatised tissues activate the co-agulation system and release MICROTHROMBI into circulation. These occlude the pulmonary Microvasculature. The humoral products of the thrombi increase the capillary permeability resulting in depletion of vascular volume. CLINICAL FEATURES The features are very much similar to that of hypovolaemic shock except there are two differentiating features.  Presence of pulmonary and peripheral oedema in this type of shock  Infusion of large volumes sufficient for hypovolaemic type is not sufficient for traumatic shock TREATMENT 1.Resuscitation 2.Local treatment of trauma and control of bleeding à usually by surgical debridement of ischaemic and dead tissues 3.Fluid replacement
  9. 9. 4.Use of anticoagulant therapy-One intravenous dose of 10,000 units of heparin. CARDIOGENIC SHOCK PATHOPHYSIOLOGY: This type of shock is primarily due to dysfunction of one of the ventricles.It may be because of myocardial infarction,chronic congestive heart failure,cardiac arrythmias or pulmonary embolism. “In cardiac compressive shock there is compression on the heart from outside resulting in decreased output. Causes may be tension pneumothorax and pericardial tamponade” CLINICAL FEATURES  In the beginning the skin is pale and the urinary output is low.  Gradually the pulse becomes rapid and the arterial pressure falls.  In case of right ventricular dysfunction the neck veins become distended and the liver is also enlarged  In left ventricular dysfunction the characteristic third heart sound is heard and presence of Bronchial rales. TREATMENT The treatment of cardiogenic shock involves; 1.Airway clearance for adequate oxygenation
  10. 10. 2.In case of massive pulmonary embolus-Large doses of Heparin is given intravenously 3.Pain is dealt with by Morphine 4. Persistent pulmonary oedema should be treated with a Diuretic NEUROGENIC SHOCK CAUSES: 1.Trauma to the spinal cord such as in crush injuries 2.Any blockade to the sympathetic nervous system wherein there is loss of arterial and venous tone resulting in peripheral pooling of blood. 3.Paraplegia and quadriplegia also have been known to be involved Two types of Neurogenic shock are seen: 1.Vasogenic type: It occurs in case of peripheral dilatation of blood vessel resulting in reduced blood flow to the brainàCerebral hypoxiaàUnconciousness 2.Psychogenic type: It follows sudden fright or unexpected bad news In the psychogenic type there is dilatation of the systemic vasculature which lowers the systemic arterial pressure. CLINICAL FEATURES
  11. 11. “The peculiar feature is that the skin remains warm,pink and well perfused.Urine output is also normal but the Heart rate is rapid and the BP is low” TREATMENT 1.Assuming the TRENDELENBURG position is an important aspect so as to displace blood from the systemic venules and thus increase the cardiac filling. 2.Use of Vasoconstrictors saves the patient from sudden low BP and low cardiac output thus savin organs such as Brain,kidney and heart from ischaemic damage. SEPTIC SHOCK Such a type of shock is usually due to Gramnegative septicemia. The common organisms responsible for it are: 1.E.Coli 2.Klebsiella aerobacter 3.Proteus 4.Pseudomonas PATHOPHYSIOLOGY In this type of shock there is wide spread dissemination of the exotoxin elaborated by the organism.Sometimes Gram positive such as Clostridium tetani infections result in fulminating infections and sepsis.Here there is massive fluid loss resulting in progressive hypotension
  12. 12. CLINICAL FEATURES It is often recognised by: 1. Development of chills 2. Elevated temp.above 100 C There are two types here:  Early warm shock-Cutaneous vasodilation  Late cold shock- increased vascular permiability due to persistence of septic focus. TREATMENT Here there are two lines of treatment: 1. Treatment of infection by early surgical debridement or drainage and use of antibiotics 2.Use of fluid replacement for shock followed by steroid therapy and administration of vasoconstrictors if necessary COMMON EVENTS OF SHOCK ENCOUNTERED IN CLINICAL PRACTICE The incidence of shock like features or shock itself in clinical practice should always be anticipated. These include in order of common occurrence: 1.Nausea 2.Perspiration 3.Apprehension
  13. 13. These features may subside or herald the onset of further complications. The complications include;  Syncope  Hypertension followed by hypotension  Peripheral loss of color and generalised paleness later on.  Visual disturbances followed by dizziness The features as mentioned are basically due to APPREHENSION precipitated by PAIN AND STRESS MEASURES TO BE TAKEN: 1.The patient should first be placed in TRENDELENBURG position so as to increase the blood flow to the heart and to the brain. In case of pregnancy the patient should be in LEFT LATERAL DECUBITUS POSITION. 2.Secondly monitoring of BP,pulse and respiratory rate should be done. If the patient still continues to have Bradycardia Then: ATROPINE-0.5 to 1 mg should be administered and repeated every 5 minutes to a maximum dose of 3mg.
  14. 14. Full recovery in this case should occur after in 20 minutes.If loss of conciousness takes longer than 20 minutes then Emergency Medical service should be called upon (Priorly informed!!) Finally what can be said is that the very word SHOCK creates an impression of a Life threatening procedure. It is so….but what is needed is more of a preventive based approach keeping in mind the factors related to shock that may be encountered in day today events.A calm and calculated approach from the Clinician as a result of previous training for such situations goes a long way in saving lives.