| Why does arterial blood pressure fall generally in shock | This can because of decrease in cardiac output and decrease in total peripheral resistance |
| What can cause fall in cardiac output | Hypovolaemia
Loss of contractility
Reduced filling of the cardium |
| What causes the fall in Total Peripheral Resistance | Profound vasodilation |
| What are some causes of hypovolemic shock | Blood loss due to hemorrhage
Gastro-intestinal loss
Burns
Third space loss → fluid losses into spaces that are not visible, such as the bowel lumen (in bowel obstruction) |
| What is the pathophysiology behind hypovolemic shock | Decreased blood volume leads to fall in venous pressure leading to reduced end-diastolic volume so there is reduced stroke volume which leads to fall in CO so a fall in mean arterial blood pressure
Reduction in arterial BP is sensed by baroreceptors
Which triggers a number of compensatory mechanisms:
RAAS system
Sympathetic system
Internal transfusion |
| For the 3 compensatory mechanisms for hypovolemic shock, what is the pathophysiology behind that | Increased sympathetic activity --> Increase HR, Increase contractility, Vasoconstriction , Venoconstriction
RAAS --> angiotensin II leads to aldosterone release, Na+ reabsorption , vasoconstriction , releases noradrenaline to increase sympathetic activity and release of ADH from the anterior pituitary gland
Internal Transfusion --> Increase in TPR leads to decrease hydrostatic pressure of the capillary which leads to net flow of fluid into the capillaries |
| What can prolonged shock lead to | Imparied tissue perfusion
Tissue hypoxia
release of metabolic vasodilators
Fall in TPR
further fall in mean arterial BP
Vital organs are no longer perfused |
| What are some clinical features of hypovolemic shock | Tachycardia
Sweating
Weak peripheral pulses
Prolonged CRT
Pale skin
Cold / clammy extremities
Drowsiness / confusion / irritability
Tachypnoea → high resp rate |
| Management of hypovolemic shock | ABCDE management :
Give oxygen
Replace what is lost i.e. blood or fluid
Fix underlying cause e.g. surgery |
| If there is pulmonary embolism, how can that lead to shock | A massive, proximal pulmonary embolism can occlude a large pulmonary artery, which means
Right ventricle cannot empty
Reduced return of the blood onto the left side of the heart
Reduced left EDV
Reduced Stroke Volume
Reduced CO
Fall in mean arterial pressure |
| Clinical picture of PE and management | Shortness of Breath, Pleuritic chest pain, haemoptysis
Raised JVP
Tachycardia, hypotension, pale, sweaty
Management --> warfarin and other blood thinners , also any replace any fluid |
| What is cardiac tamponade | When the heart cannot fill because there is a buildup in the pericardial space restricting filling
Which leads to reduced EDV --> SV --> CO --> fall in Arterial BP |
| What are some causes of cardiac tamponade and clinical picture and also management | Causes --> Blunt / penetrating chest trauma or Myocardial rupture
Clinical picture --> Becks Triad: ↓ BP + ↑ JVP + Muffled heart sounds, Tachycardia, SOB etc – features of compensation
Management --> pericardiocentesis |
| What is cardiogenic shock/causes | Caused by a fall in contractility so the ventricles are unable to empty properly
Can be caused by :
MI
Acute worsening of heart failure
Arrhythmias ( loss of coordinated pump action ) |
| Pathophysiology of cardiogenic shock | Heart fills but fails to pump effectively which results in
Reduced SV
Reduced CO
fall in mean arterial BP
Central venous pressure could be raised or normal |
| What is septic shock | Circulating bacteria release endotoxins which stimulates a systemic inflammatory response, causing
Vasodilation which leads to fall in TPR
increased vascular permeability -> fall in intravascular fluid volume -> fall in CO
Leads to fall in mean Arterial BP
Baroreceptors detect drop in arterial pressure triggering increased SNS activity
Increased HR + SV
Vasoconstriction overridden by endotoxin effects
This could also be a cause of distributive shock |
| What is anaphylatic shock | Anaphylaxis = severe allergic reaction
Hypersensitive response from the immune system to usually harmless substances
Known as allergens e.g. peanuts etc.
Results in release of histamine from mast cells
Histamine is a potent vasodilator
Fall in TPR and fall in mean arterial BP
Histamine also causes bronchospasm and laryngeal oedema = difficulty breathing
This could also be a cause of distributive shock |
| Management of anaphylatic shock | ABCDE management
Adrenaline, hydrocortisone, chlorphenamine |
| What is cardiac arrest | Heart suddenly stops pumping effectively – loss of cardiac output
Due to a loss of effective electrical or mechanical activity
Patient presents with loss of consciousness, loss of pulse, loss of breathing |
| Management of cardiac arrest | CPR and defibrillation / drugs
electrical current delivered to the heart
depolarises all cells
potential for coordinated electric activity to restart
Drugs – adrenaline, amiodarone |
