Session 12 - Shock Flashcards by Jodie Murdoch

What is the main cause of peripheral vascular disease?

-Partial occlusion of arteries due to atheromatous plaque

How well did you know this?

Not at all

Perfectly

What is intermittent claudication?

Intermittent calf pain due to limited bloodflow at rest causing downstream vasodilation
Upon exercise vessels cannot dilate anymore and BF cannot be increased resulting in the accumulation of toxic metabolites

How well did you know this?

Not at all

Perfectly

How does peripheral vascular disease present in the veins?

Varicose veins

- Deep vein thrombosis

How well did you know this?

Not at all

Perfectly

At what point does coronary artery occlusion become problematic?

->70% occlusion

How well did you know this?

Not at all

Perfectly

At what point does coronary occlusion produce pain on rest?

-90%

How well did you know this?

Not at all

Perfectly

What is the difference between stable angina and unstable angina?

-Unstable angina can be present at rest

How well did you know this?

Not at all

Perfectly

How does unstable angina present differently from MI?

Does not radiate as much

- Limited duration and smaller obstruction

How well did you know this?

Not at all

Perfectly

What is the usual cause of progression from stable angina to unstable angina?

-Disruption of atherosclerotic plaque and thrombus formation

How well did you know this?

Not at all

Perfectly

How is unstable angina separable from NSTEMI clinically?

-No detectable necrosis in unstable angina ie no cardiac enzymes or troponin elevation

How well did you know this?

Not at all

Perfectly

What is the difference between NSTEMI and STEMI?

STEMI is full thickness of myocardial wall

- NSTEMI is more limited

How well did you know this?

Not at all

Perfectly

How is an STEMI different from STEMI on ECG?

-NSTEMI has ST depression

How well did you know this?

Not at all

Perfectly

Describe the ECG changes of a STEMI

ST elevation
Pathological Q waves
Twave inversion

How well did you know this?

Not at all

Perfectly

When is a Q wave pathological?

-Greater then 1mm in width and 2 small squares in height

How well did you know this?

Not at all

Perfectly

Define cardiac arrest

-Unresponsiveness associated with a lack of pulse due to the heart stopping or ceasing to pump effectively

How well did you know this?

Not at all

Perfectly

What is asystole?

-Loss of electrical and mechanical activity

How well did you know this?

Not at all

Perfectly

What is ventricular fibrillation?

-A form of cardiac arrest where there is asynchronous contraction of ventricles

How well did you know this?

Not at all

Perfectly

What are the main causes of ventricular fibrillation?

Following an MI
Electrolyte imbalance
Some arrythmias

How well did you know this?

Not at all

Perfectly

Name an arrhythmia which develops to ventricular fibrillation

-Long QT syndrome and Torsades de pointes

How well did you know this?

Not at all

Perfectly

What are the modes of treatment for cardiac arrect?

Basic life support -> chest compressions and external ventilation
Advanced life support -> defibrillation
Adrenaline

How well did you know this?

Not at all

Perfectly

How does defibrillation work in ventricular fibrillation?

Electrical current delivered to the heart
Depolarises all the cells and puts them into refractory period
Allows coordinated electrical activity to restart

How well did you know this?

Not at all

Perfectly

How does adrenaline help treat cardiac arrest?

Increases total peripheral resistance

- Enhances myocardial function

How well did you know this?

Not at all

Perfectly

What is the equation to calculate MABP?

-COxTPR

How well did you know this?

Not at all

Perfectly

What are the two groups of causes of shock?

Decrease CO

- Decrease TPR

Define shock

-Circulatory collapse when the arterial blood pressure is too low to maintain adequate perfusion

What are the three causes of decreased CO leading to shock?

- Mechanical -> pump cannot fill - Pump failure - Loss of blood volume

What is the main cause of a decrease in peripheral resistance?

-Excessive vasodilation

Name the 3 types of shock due to falls in CO

- Cardiogenic shock - Mechanical shock - Hypovalaemic shock

Define cardiogenic shock

-Acute failure of the heart to maintain cardiac output

What are the main causes of cardiogenic shock?

- Following MI due to damage to LV - Serious arrhythmias - Acute worsening HF

How is the CVP effected in cardiogenic shock?

-Can be normal or raised as heart fills but fails to pump effectively

What are the main issues in cardiogenic shock?

- Drop in arterial BP - Poor perfusion to coronary arteries -> makes pump failure worse - Poor perfusion to kidneys -> oliguria

What are the main causes of mechanical shock?

- Cardiac tamponade | - Pulmonary embolism

What is a cardiac tamponade?

- Blood or fluid build up in pericardial space | - Restricts filling of the heart -> limits end diastolic volume

What are the clinical features of mechanical shock?

- High central venous pressure | - Low arterial blood pressure

Is the electrical activity of the heart effected in mechanical shock?

-No

Describe the effect of a pulmonary embolus occluding a large pulmonary artery

- Pulmonary artery pressure high - RV cannot empty - High CVP - Reduced flow to left heart - Limits filling of heart

How could you tell the difference clinically between mechanical shock caused by cardiac tamponade and that caused by PE?

- PE will have chest pain and dyspnoea | - Cardiac tamponade will have muffled heart sounds

What is hypovolaemic shock?

-Shock caused by a reduced blood volume

What is the most common cause of hypovolaemic shock?

-Haemorrhage

Over what % loss does hypovolaemic shock occur?

-20%

What are the clinical signs of hypovolaemic shock?

- Tachycardia - Weak pulse - Pale skin - Cold, clammy extremities

Besides haemorrhage, name 2 other causes of hypovolaemic shock

- Severe burns | - Severe diarrhoea or vomiting and loss of Na+

What decompensative mechanism occurs in hypovolaemic shock?

- Peripheral vasoconstriction impairs tissue perfusion - >tissue damage due to hypoxia - > release of chemical mediator causes vasodilation and TPR falls - > AP falls dramatically - > Vital organs no longer pefused

What is distributive shock?

-Shock caused by profound peripheral vasodilaiton

Name 2 types of distributive shock

- Anaphylactic | - Toxic

What causes toxic shock?

- Septicaemia caused by endotoxins being released by circulating bacteria causes profound vasodilation - Dramatic fall in TPR followed by a fall in AP as CO cannot compensate

What are the clinical signs of toxic shock?

- Tachycardia | - Warm, red extremities

How is CO attemted to be increased in toxic shock?

- Drop in AP detected by baroreceptors - Increased sympathetic output - Heart rate and SV increased

In toxic shock, if vasoconstriction is stimulated by the sympathetic nervous system, why does vasodilation occur?

-Vasoconstrictor effect overridden by mediators of vasodilation

What is the cause of anaphylactic shock?

- Severe allergic reaction causes release of histamine from mast cells - Histamine is a powerful vasodilator which causes a dramatic fall in TPR - Dramatic drop in BP which cannot be overcome by sympathetic response

Why do people in anaphylactic shock have difficulty breathing?

-Mediators also cause bronchoconstriction and laryngeal oedema

What are the clinical signs of anaphylactic shock?

- Difficulty breathing - Collapsed - Rapid heart rate - Warm red extremities

Define hypertension

-Consistent BP over 140/90

What are the three key sites of BP regulation?

- Kidneys - Heart - Vasculature

What are the possible consequences of longstanding hypertension?

- LV hypertrophy and risk of HF - Risk of arterial disease - > coronary arteries (MI/angina) - >cerebral (stroke) - >renal (kidney failure)

What are the two main causes of poor regional perfusion?

- Arterial occlusion | - Venous congestion