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بسم هللا الرحمن الرحيم ﴿و ما أوتيتم من العلم إال قليال﴾ صدق هللا العظيم االسراء اية 58 Dr abdelaziz Hussein, Mansoura Faculty of Medicine By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology Member of American Society of Physiology Dr abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Def, • Shock means inadequate tissue perfusion. ◊ Types of shock: 1.Spinal shock. 2.Electric shock. 3.Thermal shock caused by severe cold or severe heat. 4.Metabolic shock, e.g.: • Hepatic failure. • Renal failure. • Diabetic coma. • Toxic shock. Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Types of shock: 5. Circulatory shock, e.g.: • Hypovolemic shock. • Low-resistance shock. • Cardiogenic shock. Dr abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Manifestation: • Hypovolemic shock is characterized by: 1. Hypotension. 2. Rapid weak pulse. 3. Pale, cold, sweaty skin. 4. Rapid respiration. 5. Intense sense of thirst. 6. Anxiety and restlessness. Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Causes : •1. Haemorhagic shock: •It is a hypovolemic shock caused by blood loss. •Haemorrhage ↓es the mean systemic filling pressure →↓es the VR→ ↓es COP below normal, and shock occurs. Dr abdelaziz Hussein, Mansoura Faculty of Medicine 2. Hypovolemic shock caused by plasma loss: • It is due to severe loss of plasma without loss of whole blood. • This occurs in the following conditions: a. Intestinal obstruction: • Distension of the intestine causes fluid to leak from the intestinal capillaries into the intestinal walls and intestinal lumen→ marked ↓ of plasma volume. Dr abdelaziz Hussein, Mansoura Faculty of Medicine 2. Hypovolemic shock caused by plasma loss: b. Severe burns: • Extensive burns cause severe loss of plasma through the burned areas→ marked ↓ of plasma volume. c. Trauma • Trauma or contusion to the body causes damage the capillaries → excessive loss of plasma into the tissues. d. Dehydration: • Dehydration means loss of fluid from all fluid compartments of the body e.g. in: 1. Excessive sweating. 2. Severe diarrhea or vomiting. 3. Nephrotic kidney. Dr abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine • It is caused by widespread VD which markedly ↑es the capacity of the CVS. • The blood volume is normal but, the mean circulatory pressure is ↓ed→ ↓ VR, the COP and the ABP → shock. • High blood flow in the skin and makes it warm, so it is called warm shock. ◊ Manifestation: • The same manifestations of hypovolemic shock except the skin is warm Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊Types of low-resistance shock: • a) Neurogenic shock: • It occurs by strong emotions, severe pain and irritation of the trigger zones which leads to: 1. Inhibition of VCC → VD and ↓ ABP. 2. Inhibition of CAC → tachycardia. 3. VD of blood vessels of skeletal ms and diffuse discharge of the symp VD fibers and generalized VD. 4. ↓ed COP, ABP and fainting due to ↓ed cerebral blood flow which worsen shock. Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊Types of low-resistance shock: b) Anaphylactic shock: • It is a severe allergic reaction which releases large amounts of histamine → causes massive VD. c) Septic (endotoxin) shock: • It is due to invasion of the blood by bacteria or their toxins (endotoxin). • The infection may be transmitted to the blood from, e.g. peritonitis, generalized skin infection, gangrenous area or from kidney, urinary tract, or GIT infection. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊Types of low-resistance shock: c) Septic (endotoxin) shock: manifested by; 1. High fever 2. Marked VD throughout the body due to excessive release of nitric oxide (NO) (in infected tissues) 3. Development of microclots in widespread areas of the body→ disseminated intravascular coagulation. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine • This shock is caused by severe depression of the pumping action of the heart as in myocardial infarction → marked ↓ of COP and ABP. • It is suggested that certain chemical agents (e.g. serotonin) released from the diseased myocardium stimulates the ventricular baroreceptors causing reflex inhibition of the VMC leading to VD which worsens the shock. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Manifestations: • As hypovolemic shock plus the manifestations of acute heart failure and congestion of the lungs (congested shock). Dr Abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Def, • It is a type of hypovolemic shock due to blood loss. ◊ Manifestations: • See before ◊ Stages: • Its severity depends off the amount and the rate of blood loss. • It may be either: Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Stages: 1) Reversible shock: • It occurs if the amount of blood loss is less than 20% of total blood volume. • The compensatory mechanisms succeed to restore the ABP to its normal level with the help of appropriate treatment by vasopressors and blood transfusion. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Stages: 2) Irreversible shock: • It occurs if the amount of blood loss is more than 30% of total blood volume. • The compensatory mechanisms failed to restore the ABP to its normal level. • The patient may: 1. Die soon after haemorrhage. 2. Recover with treatment. 3. Persist shock for 3-5 h and can't respond to vasopressor drugs, so COP and ABP ↓→ this state is called irreversible shock which usually ends with death. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: A) +ve feed-back death cycles: • These are dangerous cycles that eventually lead to circulatory failure and death → death cycle: Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: A) +ve feed-back death cycles: a. Cerebral ischemia: • Hge → results in hypotension and cerebral ischemia → results in depression of the VMC and cardiac centers→ bradycardia and VD→ further drop of ABP that leads to more ischemia with more depression and so on. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: A) +ve feed-back death cycles: •b. Myocardial depression: •Hge → results in hypotension, tachycardia, ↓ed coronary blood flow→ myocardial ischemia→ ↓ed force of contraction, ↓ed COP, and hypotension and so on. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: A) +ve feed-back death cycles: •c. Ischemia to the GIT; •When the blood flow to the GIT mucosa is inadequate→ injury and subsequent breakdown of the gut mucosal barrier. •This allows translocation of bacteria and endotoxin to enter the systemic circulation. Endotoxin stimulates nitric oxide (NO) synthesis→ VD and drop of ABP. •This worsens the condition and so on. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: • B) Relaxation of the precapillary sphincter: • At the beginning of shock there is spasm in the precapillary sphincter and venules especially in the splanchnic area. • This leads to hypoxia and tissue damage within 3-5 hours. • The precapillary sphincters then dilatation of the venules leading to: Dr Abdelaziz Hussein, Mansoura Faculty of Medicine dilate without Dr abdelaziz Hussein, Mansoura Faculty of Medicine ◊ Mechanisms: • B) Relaxation of the precapillary sphincter: • 1. Stagnation of blood in the capillaries (stagnant hypoxia) → more tissue damage occurs including the capillary walls→ marked ↓ in VR, COP and ABP. • 2. Damage of the capillary wall leads to escape of plasma protein and of the whole blood out of the vascular system. • At this stage the shock becomes irreversible and administration of fluid or blood is useless. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine Dr abdelaziz Hussein, Mansoura Faculty of Medicine • 1. Treatment of the cause of shock. • 2. General measures: • a. Warming the patient, but avoid over-heating as it causes VD → further drop of ABP. • b. Raising the foot of the bed to help the VR and improves the cerebral blood flow. • 3. Restoration of adequate level of tissue perfusion by transfusion of blood, plasma or saline as early and rapidly as possible to provide adequate blood flow to the vital organs i.e. brain, heart. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine • 4. Drugs used in the treatment of shock: • - Adrenaline and noradrenaline to produce arterial VC and to ↑ the force of ventricular contraction. • - Glucocorticoids as they decrease the permeability of the capillaries. • -Sedatives should be given in small doses as they inhibit the VC and CAC. Dr Abdelaziz Hussein, Mansoura Faculty of Medicine THANKS Dr abdelaziz Hussein, Mansoura Faculty of Medicine