Shock Flashcards
Where does peripheral vascular disease most commonly affect?
The legs
What can poor regional perfusion be caused by?
Arterial occlusion
Venous congestion
What percentage of blood volume to veins contain?
70%
What can varicose veins lead to?
Venous ulcers
What are varicose veins?
Dilated, torturous superficial veins
What is cardiac arrest?
When the heart has stopped or ceased to pump effectively
Patient is unresponsive and has a lack of pulse
What are the two types of cardiac arrest?
Asystole - where there is a loss of electrical and mechanical activity
Ventricular fibrillation - uncoordinated electrical activity
When may ventricular fibrillation happen?
Following an MI
Electrolyte imbalance
Arrhythmias such as long QT or Torsades de Pointes
Treatment of cardiac arrest?
Basic life support - chest compression and external ventilation
Advanced life support - defibrillation
Adrenaline
What does defibrillation do?
Electric current delivered to the heart
Depolarises cells putting them into the refractory period
Allows coordinated electrical activity to restart
What does administration of adrenaline do in cardiac arrest?
Enhances myocardial function
Increases peripheral resistance
What is shock?
An acute condition of inadequate blood flow throughout the body. There is a catastrophic fall in arterial blood pressure leading to circulatory shock
Equation to find mean arterial blood pressure?
Mean arterial BP = CO x TPR
What can a fall in cardiac output be due to?q
Mechanical where the pump cannot fill
Pump failure
Loss of blood volume
What can a fall in peripheral resistance be due to?
Excessive vasodilation
What is cardiogenic shock?
Acute failure of the heart to maintain cardiac out out - pump failure
What can cardiogenic shock be due to?
Myocardial infarction where there is damage to the left ventricle
Serious arrhythmias
Acute worsening of heart failure
What happens to arterial and venous blood pressure in cardiogenic shock?
Arterial - drops
CVP - normal or raised
What is cardiac tamponade?
Blood or fluid build up in pericardial space
What happens to CVP and arterial blood pressure in mechanical shock?
Arterial is low
CVP is high
What can mechanical shock be due to?
Cardiac tamponade
Pulmonary embolism
What is mechanical shock?
When the ventricle cannot fill properly
Explain how a pulmonary embolism can lead to shock and leads to high CVP
Embolus occludes a large pulmonary artery Pulmonary artery pressure is high Right ventricle cannot empty CVP is high Reduced return of blood to left heart
Causes of hypovolaemic shock?
Haemorrhage
Severe burns
Severe diarrhoea or vomiting and loss of Na
How much blood do you need to show some signs of shock and then serious shock?
20-30% - some signs
30-40% - serious
What initially happens to blood pressure and cardiac output when there is a haemorrhage?
Venous pressure falls
Cardiac output falls due to Starling’s law
Arterial pressure falls
What is the compensatory response to haemorrhage?
Arterial pressure drop is detected by baroreceptors Increased sympathetic stimulation Tachycardia Increased force of contraction Peripheral vasoconstriction Venoconstriction
Signs of hypovolaemic shock?
Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities
What does peripheral vasoconstriction lead to?
Impaired tissue function Tissue damage due to hypoxia Release of vasodilators Fall in TPR Drop in blood pressure Vital organs no longer perfused
What is distributive shock?
When the blood volume is constant, but volume of the circlulation has increased due to a drop in total peripheral resistance
What type of shock is toxic and anaphylactic shock?
Distributive
What happens in toxic shock?
Endotoxins are released by circulating bacteria
Cause profound vasodilation
Fall in TPR
Fall in arterial pressure
Impaired perfusion of vital organs
Capillaries become leaky, reducing blood volume
Signs of toxic shock?
Tachycardia
Warm, red extremities
Vasoconstriction in later stages
What happens in anaphylactic shock?
Release of histamine from mast cells
Powerful vasodilator - fall in TPR
Drop in arterial pressure
Increased sympathetic response but cannot overcome vasodilation
Impaired perfusion of vital organs
Bronchoconstriction and laryngeal oedema caused by mediators
Signs of anaphylactic shock?
Difficulty breathing
Collapsed
Tachycardia
Red, warm extremities
What is administered in anaphylactic shock and what is its effect?
Adrenaline
Vasoconstriction via action at α1 receptors
Which types of shock lead to a decrease in total peripheral resistance?
Distributive shock
- anaphylactic
- toxic
Which types of shock lead to a decrease in cardiac output?
Hypovolaemic
Cardiogenic
Mechanical
What are the three sites of regulation of blood pressure? How do each of these sites regulate it?
Kidneys - regulate blood volume
Heart - alter rate and force of contraction
Vasculature - regulate TPR
What can hypertension lead to?
Left ventricular hypertrophy
-risk of heart failure
Arterial disease
- coronary arteries ➡️ MI/angina
- cerebrovascular system ➡️ stroke
- renal vasculature ➡️ kidney failure
- retina
- aorta
Treatment of hypertension?
Diuretics
Vasodilators
ACE inhibitors
Beta blockers
