7. Haemodynamic Shock Flashcards
What is haemodynamic shock?
Acute condition of inadequate blood flow throughout the body
What leads to circulatory shock?
Catastrophic fall in BP
What can shock be due to?
Fall in cardiac output or total peripheral resistance beyond the capacity of the heart to cope
What is cardiogenic shock?
Pump failure - heart fills but fails to pump effectively
Give 3 causes of cardiogenic shock
Following an MI where there is damage to the LV
Serious arrhythmias
Acute worsening of heart failure
What would you see clinically with cardiogenic shock?
Central venous pressure normal or raised.
Dramatic drop in arterial BP.
Tissues poorly perfused - eg coronary arteries, making problem worse, and kidneys, leading to oliguria
What is a cardiac arrest?
Unresponsiveness associated with lack of pulse - heart has stopped
What 3 things can cause a cardiac arrest?
Asystole (loss of electrical and mechanical activity). Pulseless electrical activity (PEA). Ventricular fibrillation (uncoordinated electrical activity) - most common, often following MI, electrolyte imbalance or some arrhythmias.
What should be done in a cardiac arrest?
Basic life support - chest compressions and external ventilation.
Advanced life support - defibrillation depolarises all cells putting them into the refractory period.
Adrenaline - enhances myocardial function and increases peripheral resistance.
What type of haemodynamic shock do cardiac tamponade and pulmonary embolisms cause?
Mechanical shock
What is cardiac tamponade?
Blood or fluid build up in pericardial space, restricts filling of heart
What would you see clinically in mechanical shock caused by cardiac tamponade?
High central venous pressure
Low arterial blood pressure
Continued electrical activity
What is a pulmonary embolism?
Embolus concluding a large pulmonary artery
How does a pulmonary embolism lead to mechanical shock?
Pulmonary artery pressure high, reduced return of blood to left heart, left atrial pressure low, arterial blood pressure low
What other symptoms are present in a pulmonary embolism?
Chest pain and dyspnoea
How does an embolus normall reach the lungs?.
DVT, some of thrombus breaks off, travels in venous system to right side of heart, pumped out via pulmonary artery to lungs
What is hypovolaemic shock?
Reduced blood volume leading to inadequate venous return
What is mechanical shock?
Ventricle cannot fill properly
What is hypovolaemic shock most commonly due to?
Haemorrhage
What is the severity of hypovolaemic shock related to?
Amount and speed of blood loss
What would you see clinically in a patient with hypovolaemic shock?
Tachycardia (increased sympathetic stimulation due to decreased BP being detected by baroreceptors), increased force of contraction, peripheral vasoconstriction and venoconstriction
Weak pulse
Pale skin
Cold, clammy extremities
What is internal transfusion?
Increased peripheral resistance reduces capillary hydrostatic pressure in hypovolaemic shock, and so there is net movement of fluid into capillaries
What can hypovolaemic shock result from other than haemorrhage?
Severe burns
Severe diarrhoea or visiting and therefore loss of Na+
What is it called in hypovolaemia where BP can maintain high despite blood loss?
Decompensation
