12 - Shock Flashcards
What types of shock are the result of a drop in cardiac output?
Cardiogenic
Mechanical
Hypovalaemic
What is Shock?
Catastrophic drop in mean arterial BP
Mean Arterial BP = CO x TPR
So shock is the result in a drop in CO or in TPR that the system cannot cope with
What types of shock are the result of changes to total peripheral resistance?
Septic
Anaphylactic
What is Cardiogenic shock?
acute failure of the heart to maintain cardiac output
When can Cardiogenic shock occur?
Following an MI
As a result of a serious arrhythmias
Acute worsening of heart failure
Describe what happens in Cardiogenic shock
CVP is normal or raised so the heart is able to fill properly but it does not pump effectively
Decreased Arterial Blood Pressure
Tissues are poorly perfumed, particularly the coronary arteries and kidney
What is oliguria?
Reduced urine production as a result of Cardiogenic shock
What is mechanical shock?
When there is an obstruction that prevents the ventricle from filling properly
What are the two situations in which mechanical shock can occur?
Cardiac Tamponade
Pulmonary Embolism
Describe how cardiac Tamponade causes mechanical shock
Fluid in the pericardial sac reduces filling of the heart
Reduced end diastolic volume
Increase CVP and decreased ABP
Electrical activity is normal
Describe how a pulmonary embolism can cause mechanical schock
Only occurs if massive PE and occlusion of a large pulmonary artery
Increased pulmonary artery pressure
RV doesn’t empty properly so increased CVP
Decreased blood return to the heart so limited filling = lower LV pressure
Reduced AP
What are some signs of mechanical shock as the result of pulmonary embolism
Chest pain
Dyspnoea
What is hypovalaemic shock?
Shock caused by as severe loss to blood volume (>20%)
What are some causes of hypovalaemic shock?
Haemorrhage
Severe burns
Severe diarrhoea or vomiting
Describe hypovalaemic shock as the result of haemorrhage
Reduced VP = reduced CO = reduced AP which is detected by Baroreceptors = increased sympathetic drive
Leads to increased force of contraction, peripheral vasoconstriction and venoconstriction
What are some signs of hypovalaemic shock?
Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities
How do you treat hypovalaemic shock?
Treat with internal transfusion
- increased peripheral resistance = decreased hydrostatic pressure = net movement of water into the capillaries
What is decompression?
Peripheral vasoconstriction = tissue damage by hypoxia = release of chemical mediators = decreased TPR = decreased BP = multi-system failure
What is septic shock?
Shock that occurs due to the release of endotoxins by circulating bacteria
Describe what happens in septic shock
Release of endotoxins = profound vasodilation = decreased TPR = reduce AP = impaired perfusion and leaky blood vessels so reduced blood volume
Baroreceptors detect drop in AP so stimulate sympathetic NS = increased heart rate and stroke volume
Despite the activation of the sympathetic nervous system there is still vasodilation, why?
The vasoconstriction effects of the sympathetic NS are overridden by the vasodilator mediators released by the bacteria
What are some signs of septic shock?
Tachycardia
Warm, red extremities
What is anaphylactic shock?
Shock that is the result of a severe allergic reaction
Describe what happens in anaphylactic shock
Release of histamines = profound vasodilation = reduced TPR = reduced AP = stimulation of sympathetic NS = increased CO
- impaired perfusion
- brochoconstriction and laryngeal odema
