CVS 12 Shock, Review and Hypertension Flashcards
What can cause poor regional perfusion?
arterial occlusion- peripheral artery disease, coronary artery disease
venous congestion- varicose veins, DVT
In which direction do veins drain?
Superficial to deep
What constitutes a positive exercise stress test for ischaemic heart disease?
If there is chest discomfort or ECG changes
What ECG abnormality is seen in angina?
ST segment depression
What is stable angina treated with?
Nitrates
Beta- blockers
Calcium channel antagonists
What is the principle action of nitrates in angina relief?
Venodilation causing decreased preload to heart to reduce workload
What abnormalities are see in an ECG with unstable angina?
ST depression and/or T wave inversion
What ECG changes are seen with a STEMI?
ST elevation
T wave inversion
Pathological Q waves
What feature of a STEMI ECG persists even weeks after recovery?
Pathological Q waves
What is troponin and which isoforms are used to detect MI?
Regulatory protein that is bound on tropomysosin, involved in muscle contraction
Troponin I and Troponin T
What is cardiac arrest?
Unresponsiveness associated with lack of pulse
Heart has either stopped or ceased to pump effectively
What is asystole?
Loss of electrical and mechanical activity
What is the most common form of cardiac arrest and when does it occur?
Ventricular fibrillation
May occur following MI or electrolyte imbalance or some arrhythmias (e.g long QT and Torsades de Pointes)
What is pulseless electrical activity?
Form of cardiac arrest where ECG looks normal but there is no pulse
What basic life support is used to treat cardiac arrest?
Chest compression and external ventillation
How does defibrillation work?
Electrical current delivered to heart
Depolarises all cells and puts them in the refractory period
Allows coordinated electrical activity to restart
Why is adrenaline used in cardiac arrest?
Enhances myocardial function and increases peripheral resistance
What is shock?
Acute condition of inadequate blood flow throughout body
What causes circulatory shock?
Catastrophic fall in arterial blood pressure due to a fall in CO or TPR
How is mean arterial BP calculated from cardiac output and TPR?
Mean arterial BP=COxTPR
In what ways can CO fall to cause shock?
Mechanical- pump can’t fill
Pump failure
Loss of blood volume
What causes a fall in peripheral resistance?
Excessive vasodilation
What is cardiogenic shock?
Acute pump failure causing a drop in CO
Following MI, serious arrythmias or ACUTE WORSENING of heart failure (standard heart failure is not cadiogenic shock, it is chronic)
What is oliguria?
Reduced urine production
Occurs when poor kidney perfusion
What kind of shock can cardiac tamponade cause?
Mechanical
How does cardiac tamponade cause shock?
Blood or fluid fills the pericardial space
Restricts filling of the heart- limits end diastolic volume and so STROKE VOLUME
Affects both sides of heart
High CVP
Low arterial BP
Heart still attempts to beat so continued electrical activity
What kind of shock does a pulmonary embolism cause?
Mechanical
How does a pulmonary embolism cause shock?
Embolus occludes a large pulmonary artery PA pressure HIGH right ventricle can't empty CVP high Reduced return of blood to left heart limiting filling LA pressure low Arterial blood pressure low CO lowered due to reduced SV
What other symptoms are felt with pulmonary embolism?
Chest pain, dyspnoea (SOB)
How many litres of blood are in a normal man?
5l
What is the most common cause of hypovolaemic shock?
Haemorrhage
How much blood loss causes a shock response?
20-30% some signs of shock response
30-40% serious shock response
What happens to pressures during Haemhorrage?
Venous pressure falls
Cardiac output falls (starling’s law)
Arterial pressure falls
Detected by baroceptors
What happens in the compensatory response to haemorrhage?
Increased sympathetic stimulation Tachycardia Inc force of contraction Peripheral vasoconstrcition VENOCONSTRICTION- inc VP and so venous return
How does the patient present when in hypovolaemic shock?
Tachycardia, weak pulse, pale skin, cold, clammy extremeties
What other causes of hypovolaemic shock are there?
Severe burns
Severe diarrhoea or vomiting and loss of Na+
What is decompensation?
Failure of a system to adapt and compensate for stressors
What happens in decompensation in hypovolaemic shock?
Peripheral vasoconstriction causes tissue damage due to hypoxia
Chemical mediators released in response causing vasodilation
TPR falls
Blood pressure falls dramatically
Vital organs no longer perfused
Multi system failure
What is distributive shock?
Low resistance (normovolaemic) shocl where profound peripheral vasodilation causes a decrease in TPR and BP
What are two types of distributive shock?
Toxic shock
Anaphylactic shock
What happens in toxic (septic) shock?
Septicaemia
Endotoxins released by circulationg bacteria
Cause profound vasodilation
Dramatic fall in TPR
Fall in arterial pressure
Inpaired perfusion of vital organs
Capillaries become leaky and reduce blood volume
What happens to compensate in toxic shock?
Low arterial pressure detected by baroceptors
Increased sympathetic output
Vasoconstrictor affect overriden by mediators of vasodilation
HR and SV increase
How will a person in toxic shock present?
Tachycardia, warm, red extremities (initial vasodilation)
What happens in anaphylactic shock?
Histamine released from mast cells due to allergen
(other mediators too)
Powerful vasodilator- fall in TPR
Dramatic drop in arterial pressure
Impaired perfusion of vital organs
Mediators cause bronchoconstricition and laryngeal oedema
What is the compensatory response in anaphylactic shock?
Increased sympathetic drive increases CO but this cant overcome the vasodilation
How will a patient with anaphylactic shock present?
Difficulty breathing
Collapsed
Tachycardia
Red warm extremities
How is anaphylactic shock treated?
Adrenaline injection
High adrenaline conc above physiological levels activates a1 receptors causing vasoconstriction
What BP classes as hypertensive?
140/90mmHg
At what three sites is blood pressure regulated?
Kidneys- regulates blood vol which alters SV
Heart- rate and force of contraction
Vasculature- TPR
What does long standing hypertension cause in the heart?
LV hypertrophy and risk of heart failure
What does long standing hypertension cause in the arteries?
Arterial disease: Coronary arteries- MI, angina Cerebrovascular system- stroke Renal vasculature- kidney failure Retina Aorta
In what non-pharmological ways can hypertension be treated?
Weight loss, exercise, reduced salt intake
In what pharmological ways can hypertension be treated?
Duiretics
Vasodilators
ACE inhibitors
Beta blockers
