Haemodynamic Shock Flashcards
What is haemodynamic shock?
Acute condition of inadequate blood flow throughout the body
*a catastrophic fall in arterial blood pressure leads to circulatory shock
What types of shocks are there due to fall in cardiac output?
Cardiogenic shock (pump failure)-V dont empty properly
Mechanical shock (obstructive)- v cannot fill properly
Hypovolaemic shock -reduced blood volume leads to poir venous return
What is cardiogenic shock?
Acute failure of the heart to maintain cardiac output - pump failure
Similar to heart failure but different in that is it an acute condition
What are the potential causes of cardiogenic shock?
- MI causing damage to left ventricle, part of myocardial has died therefore cannot pump enough blood to maintain BP
- serious arrhythmias-heartmight be pumping too slowly (bradycardia) or too fast (tachycardia) which might mean the ventricle isn’t able to fill
- acute worsening of heart failure
What issues does cardiogenic shock produce?
Raised CVP
Dramatic drop in arterial BP
Poorly perfused tissues (if the coronary arteries are affected it can exacerbate the problem, if the kidneys are poorly perfused it may result in poor urine production- oliguria)
What is cardiac arrest?
Unresponsiveness associated with lack of pulse
Heart has stopped or ceased to pump effectively
Asystole, pulseness electircal activity (no pulse but there is still electively activity- appears normal on ECG), ventricular fibrillation (can cause asystole)
How do you treat cardiac arrest?
Basic life support- chest compression and external ventilation
Advances life support- defibrillation- puts all cells in refractory period allowing the pacemaker cells to start setting the pace again
Adrenaline- enhances myocardial function,increase peripheral resistance (acts on a1 receptors)
What is mechanical shock?
When the ventricle cannot fill properly
Ie Cardiac tamponade
-blood or fluid builds up in pericardial space, restricts filling of the heart- limits end diastolic volume
What does mechanical shock cause?
High central venous pressure (blood returns to heart but cant get in )
Low arterial blood pressure (very little cardiac output due to low stroke volume)
During mechanical shock the heart will continue to beat and will attempt to increase the cardiac output. If stroke volume is being limited how can the heart do this?
Increase heart rate
How can a massive pulmonary embolism cause mechanical shock?
- Embolus occludes large pulmonary artery
- Pulmonary artery pressure rises
- Relight ventricle cannot empty
- Central venous pressure rises
- Reduced return of blood to left heart
- Limits filling of the left side of the heart
- Left atrial pressure is low
- Arterial pressure is low
- Shock
What are the other side effects of PE aside from mechanical shock?
Chest pain, dyspnoea
What is hypovolaemic shock?
Haemodynamic shock due to Reduced blood volume
(Most commonly due to haemorrhage, but can also be caused by severe burns, severe diarrhoea or vomiting and loss of Na+)
Severity of shock is related to amount and speed of blood loss
How does the body attempt to counteract hypovolaemic shock caused by a haemorrhage. How it is detected in the first place?
Haemorrhage Venous pressure falls (fall in stroke volume) Cardiac output falls Arterial reassure falls Detected by baroreceptors
Increased sympathetic stimulation
Cause; tachycardia, increased inotropy, peripheral vasoconstriction (NA acting on A1 receptors), venoconstriction
How does internal transfusion occur during hypovolaemic shock?
Increased peripheral resistance reduced the capillary hydrostatic pressure causing net movement of fluid into capillaries
