CVS: Heamodynamic Shock Flashcards
Give 3 equations for mean arterial blood pressure.
CO*TPR
2/3 diastoli c+ 1/3 systolic
Diastolic pressure + 1/3 pulse pressure
Name 3 types of shock due to a fall in cardiac output.
- Cardiogenic shock (pump failure)
- Mechanical shock (obstructive)
- Hypovolamic shock (reduced blood volume leading to poor venous return)
Name some potential causes of cardiogenic shock.
- MI
- Serious arrthymias (e.g. Tachycardia, bradycardia)
- Acute worsening heart failure
What is cardiac arrest?
An unresponsiveness associated with lack of pulse. The heart has stopped or has ceased to pump effectively.
Are some potential causes of mechanical shock.
- Cardiac tamponade
- Pulmonary embolism
Which side of the heart does cardiac tamponade affect?
Both
Which side of the heart does a pulmonary embolism affect?
Left
How does cardiac tamponade affect central venous pressure and arterial blood pressure?
- Central venous pressure will be higher as blood that is returning to the Wharton cannot fill the heart
- Arterial blood pressure will be low as the heart can not produce the same CO due to prevention of diastole from lack of space
What percentage of blood would have to be lost in order to induce hypovolaemic shock?
20-30% blood lost would show some signs of shock response
30-40% results in a substantial decrease in mean aBP and a serious shock response
Name some potential causes of hypovolaemic shock.
- Heamorrhage
- Severe Burns
- Severe diarrhoea or vomiting
How does haemorrhage result in hypovolaemic shock?
- Venous pressure falls causing CO to fall
- This results in aBP falling which is detected by baroreceptors
How does a patient with hypovolaemic shock present?
- Tachycardia
- Weak pulse
- Pale skin
- Cold, clammy extremities
Describe the danger associated with decompensation following hypovolaemic shock.
- Peripheral vasoconstrictors impairs tissue diffusion
- Following tissue damage due to hypoxia, chemical mediators are released causing vasodilation
- TPR falls therefore BP falls dramatically
- Vital organs can no longer be perfumed leading to multi system failure
Name 2 causes of distributive shock.
- Toxic (septic) shock
2. Anaphylactic shock
How does septic (toxic) shock lead to a impaired perfusion of vital organs?
- Endotoxins released by circulating bacteria cause a profound inflammatory response
- This causes profound vasodilation causing a dramatic fall in aBP
- This leads to impaired perfusion of vital organs
How does a patient with septic (toxic) shock present?
- Tachycardia
- Warm, red extremities initially (however later stages of sepsis-vasoconstriction- result in localised hypo-perfusion)
How does a patient with anaphylactic shock present?
- Difficulty breathing
- Collapsed
- Rapid heart rate
- Red warm extremities
How do you treat patients with anaphylactic shock and how does it work?
Adrenaline: Vasoconstriction via action at alpha-1 adrenoreceptors
