Lecture 18- Haemodynamic Shock Flashcards
How is mean arterial Bp calculated?
Co by TPR
Diastolic BP + 1/3 pulse pressure
Sv X HR X TPR
What is haemodynamic shock?
Acute condition of inadequate blood flow throughout the body
What can cause shock?
Either a fall in CO or fall in TPR
CO: mechanical
Cardiogenic
Hypovolaemic
TPR: vasodilation
What is cardiogenic shock?
When heart fills ok but can not pump adequately (pump failure)
Causes include myocardial infarction, arrythmias
Poor perfusion of coronary arteries can worsen
Poor kidney perfusion oliguria
What is cardiac arrest?
Unresponsive ness with absence of pulse
Asystole (loss of mechanical and electrical activity)
Can also get pulseless electrical activity (PEA)
Ventricular fibrillation
Cardiac arrest treatment?
Basic life support (CPR)
Defibrillation to put cardiomyocytes into refraction and allow coordinated electrical activity to restart
Adrenaline
Mechanical shock?
Can be caused by cardiac tamponade or PE
Cardiac tamponade- blood build up in pericardial space restricts ventricular filling. Get high venous pressure and low arterial pressure
Get rapid HR
PE- large embolus blocks pulmonary artery reduces return of blood to left side of heart. Low left atrial pressure and high right ventricular pressure. Causes dyspnoea
Hypovolaemic shock?
20% blood loss no symptoms and volume should return in 3 days through RAAS and ADH
20-30% some signs of shock response
30_40% serious shock response
What happens in hypovolaemic shock?
Lowered Bp detected by baroreceptors leading to sympathetic response. Vasoconstriction with tachycardia and increased force of contraction
net Movement of fluid reverses into capillaries instead of out due to increased oncotic pressure and decreased hydrostatic pressure
Signs of hypovolaemic shock?
Cold and clammy extremities
Tachycardia and weak pulse
Pale skin
Low CVp
Other causes of hypovolaemic shock?
Vomiting, diarrhoea and burns
What happens with decompensation and hypovolaemic shock?
Sudden worsening of symptoms of heart failure.
Get peripheral vasoconstriction
Hypoxic tissue damage and falling TPR due to release of chemical mediators. Fall in BP and multi system failure
What is distributive shock?
Shock due to low resistance rather than hypovolaemia
Can be caused by sepsis or anaphylaxis
Septic shock?
Causes distributive shock.
Infection releases endotoxins causing vasodilation get red hot extremities and leaky capillaries.
Get tachycardia also. Later stages get vasoconstriction resulting in localised hypo perfusion
Anaphylactic shock?
Other cause of distributive shock. Release of histamine from mast cells.
Vasodilation cannot be overcome by sympathetic innervation.
Also get bronchoconstriction and breathing difficulty. Rapid heart rate and collapse with warm extremities
