Session 11- Haemodynamic shock Flashcards
(26 cards)
How do yo calculate mean arterial blood pressure
CO x TPR
SV x HR x TPR
Diastolic pressure + 1/3 pulse pressure
What is haemodynamic shock
Acute condition of inadequate blood floe throughout the body
A catastrophic fall in arterial blood pressure leads to circulatory shock
What can cause shock
A fall in cardiac output
Fall in TPR beyond capacity of the heart to cope
How can a fall in CO cause shock
Fall in CO can be due to-
Mechanical- pump cannot fill
Loss of blood volume
Pump failure
What is cardiogenic shock
Acute failure of the heart to maintain cardiac output- pump failure
Heart fills but fails to pump
CVP raised because EDV is raised so EDP is raised to heart is harder to fill
Dramatic drop in arterial BP due to drop in CO
Causes of cardiogenic shock
Following myocardial infarction
-damage to left ventricle
Serious arrhythmia
Acute worsening of heart failure
Consequences of cardiogenic shock
Tissues portly perfused
- coronary arteries may be poorly perfused which exacerbates problem
- kidney may be poorly perfused- reduced urine production (oliguria)
What is cardiac arrest
Unresponsiveness associated with lack of pulse
Heart has stopped or has ceased to pump effectively
Types of cardiac arrest
Asystole
Ventricular fibrillation
Pulseless electrical activity
How do you treat cardiac arrest
Basic life support
Advanced life support
- defibrillator
- electrical current delivered to heart
- depolarises al the cells- puls them into refractory period
- allows coordinated electrical activity to restart
Adrenaline
What if mechanical shock- cardiac tamponade
- Blood of fluid build up in pericardial space
- restricts filling of the heart- limits end diastolic volume
- affects both sides of heart
High CVP- heart harder to fill
Low arterial blood pressure- always low in shock
Mechanical shock - pulmonary embolism
Embolus occuldes large pulmonary artery
RV cant empty
CVP is high
Reduced return of blood to left heart - limited filling of left heart
Low arterial pressure- low SV
Symptoms pulmonary embolism
Chest pain
Dyspnoea
Difficulty breathing
How might an embolus reach the lungs
DVT
Portion of thrombus breaks off
Travels in venous system to right side of heart
Pumped out pulmonary artery to lungs
What is hypovolaemic shock
Reduced blood volume mostly due to haemorrhage
30-40% substantial decrease in mean aBP and serious shock response
What happens in haemorrhage
Venous pressure falls
Cardiac output falls
Arterial pressure falls
Detected by baroreceptors
Compensatory resposne of hypovoloemic shock
– increased sympathetic stimulation – tachycardia – increased force of contraction – peripheral vasoconstriction -venoconstriction
Symptoms of hypovolaemic shock
Tachycardia
Weak pulse- decrease in Sv due to decrease in blood volume
Pale skin
Cold, clammy extremities
What is decomposition
Peripheral vasoconstriction impairs tissue perfusion
- release of vasodilators
- TPR falls
- blood pressure falls
- vital organs can no longer be perfused
- multi system failure
What is distributive shock
Uncontrolled falls in peripheral resistance
Profound peripheral vasodilation- decrease in TPR therefore ABP
What is toxic septic shock
Endotoxins released by circulating bacteria
- profound inflammatory response
- profound vasodilation
- dramatic fall in TPR
- fall in arterial pressure
- impaired perfusion of vital organs
- capillaries become leaky therefore blood volume is reduced
- increased coagulation and localised hypo-perfusion in extremities
Symptoms of septic shock
Tachycardia
Warm, red extremities initially but later stages of sepsis- vasoconstriction- localised hypoperfusion
What is anaphylactic shock
Severe allergic reaction causes release of histamine from mast cells which has a powerful vasodilator effect which causes a fall in TPR
Drop in arterial pressure causes increased sympathies response- increase in CO but can’t overcome vasodilation
Consequences of anaphylaxis
Impaired vital organ perfusion
Bronconstricipn and laryngeal oedema
-difficulty breathing
