Shock Flashcards
What is shock?
A state of inadequate oxygen delivery to tissues resulting in cellular dysoxia which is often accompanied by, but may be independent of a decreased systemic arterial BP
What is does oxygen delivery NOT equal?
Oxygen consumption
What are the three main types of shock?
1) Hypovolaemic
2) Distributive
3) Cardiogenic
What is cardiogenic shock subdivided into?
1) Obstructive (RV)
2) LV (cardiogenic?)
What are causes of hypovolaemic shock?
1) Haemorrhage
2) GI losses
3) Dehydration
4) Capillary leak
What are the causes of distributive shock?
1) Sepsis
2) Anaphylaxis
3) SIRS
4) Massive transfusion
5) Post-cardiac arrest
6) Adrenal crisis
7) Neurogenic
What are causes of obstructive shock?
1) Tamponade
2) Tension PTX
3) Massive PE
4) RV infarction
5) Cor pulmonale
6) Pulmonary HTN
What are causes of cardiogenic (LV) shock?
1) MI
2) Myocarditis
3) Septic cardiomyopathy
4) Arrhythmia
5) Acute mitral regurgitation
6) Critical aortic stenosis
What can shock in the RV lead to?
Shock in the LV
How does anaphylaxis cause low BP?
Vasodilation
What are the two most common causes of shock?
1) Sepsis
2) Anaphylaxis
What is tamponade?
Fluid in the cardiac sac
What is the symbol for oxygen delivery?
DO2
What is the long oxygen delivery equation?
DO2 = CO x (Hb x SaO2 x 1.34 + (PaO2 x 0.003))
What is the short oxygen delivery equation?
DO2 = CO x arterial oxygen content (CaO2)
What does a problem with any part of the oxygen delivery equation lead to?
Shock (impaired oxygen delivery)
What is the equation for the amount of oxygen dissolved in the blood?
PaO2 x 0.003
What is the equation for CO?
CO = SV x HR
What factors affect stroke volume?
1) Preload
2) Afterload
3) Contractility
What factors affect the arterial oxygen content?
1) Haemoglobin
2) SaO2 (arterial oxygen saturation)
3) PO2 (arterial oxygen tension)
Between what ranges of BP does the body compensate and what happens outside these ranges?
~ 55-250 mmHg → outside these ranges = shock
What is VO2?
Oxygen extraction from the blood
What is MRO2?
Metabolic requirement of oxygen in the cell
When does shock happen (at cellular level)?
VO2 < MRO2 → shock
What are the (non-specific) manifestations of shock?
1) Anxiety, restlessness, confusion, aggression, lethargy, coma → brain is being deprived of oxygen
2) Rapid shallow breathing
3) Nausea/vomiting
4) Rapid (weak) pulse
5) Low BP and pulse pressure
6) Pale, grey or cyanotic with clammy skin
7) Reduced urine output
8) Acidosis
9) Decreased coagulation time and increased neutrophils (after 2-5 hours)
10) Intense thirst
11) Delayed capillary refill (cold)
What can the neurological symptoms of stroke be mistaken for?
Being drunk
What is SVR?
Systemic vascular resistance (vasoconstriction)
What is the initial insult in hypovolaemic shock?
Decreased preload
What is the compensation in hypovolaemic shock?
Increased SVR
What are the key features of hypovolaemic shock?
- Cold
- Clammy
- Narrow pulse pressure
What is the initial insult in cardiogenic shock?
Decreased contractility
What is the compensation in cardiogenic shock?
Increased SVR
What are the key features of cardiogenic shock?
- Cold
- Clammy
- Increased JVP
- Narrow pulse pressure
- Often look well
What is the initial insult in obstructive shock?
Increased preload/PVR
What is the compensation in obstructive shock?
Increased/- SVR
What are the key features of obstructive shock?
- Cold
- Clammy
- Increased JVP
What is the initial insult in distributive shock?
Decreased SVR
What is the compensation in distributive shock?
Increased contractility
What are the key features of distributive shock?
- Warm
- Hyperdynamic → tachycardia
- Wide pulse pressure
What are possible causes of shock from a car accident?
Hypovolaemic or obstructive (tension PTX, tamponade)
What is cardiac contusion?
Blunt trauma to the heart and sternum
Which receptors are more sensitive and act first - baroreceptors or chemoreceptors?
Baroreceptors
Why do you not see a drop in BP in the original phase of shock?
Bc of compensatory mechanisms
What is the most sensitive signs to the severity of shock?
Tachypnoea and tachycardia (v unspecific)
How many classes of haemorrhagic shock are there?
4
Describe shock class I (blood loss, HR, BP, PP, RR, mental status)
- Blood loss < 750ml (15%)
- HR < 100 bpm
- BP normal
- PP normal
- RR 14-20
- Slightly anxious
Describe shock class II (blood loss, HR, BP, PP, RR, mental status)
- Blood loss 750-1500ml (15-30%)
- HR 100-120 bpm
- BP normal
- PP narrowed
- RR 20-30
- Mildly anxious
Describe shock class III (blood loss, HR, BP, PP, RR, mental status)
- Blood loss 1500-2000ml (15-30%)
- HR 120-140 bpm
- BP decreased
- PP narrowed
- RR 30-40
- Anxious, confused
Describe shock class IV (blood loss, HR, BP, PP, RR, mental status)
- Blood loss > 2000ml (>40%)
- HR >140 bpm
- BP decreased
- PP narrowed
- RR >35
- Confused, lethargic
What is a way to remember the % blood loss for the 4 classes of shock?
Tennis scores
What is the lethal triad in polytrauma?
Coagulopathy, acidosis and hypothermia (CAH)
Why does trauma lead to coagulopathy?
Bc the bleeding consumes the clotting factors
How do you give blood?
Give packed red cells in a 1:1:1 ratio with plasma and platelets
What is pathognomonic of MI on an ECG?
- ST elevation (bottom lead shows tombstone ST elevation)
How do you treat MI shock?
- Oxygen (if hypoxic?)
- Inotrope to improve SV e.g. adrenaline
- Cath lab
- Aspirin
What will you see on an echo of someone with a major PE?
The LV will be smaller than the RV → RV abnormally big so LV is smaller in contrast
Which ventricle is more sensitive?
RV
How does a major PE lead to shock?
Pressure on RH → RV decompensation → increased RV volume → decreased LV preload → decreased CO
What do you give to treat a PE?
- Thrombolysis (bc decompensated)
- If not shock → anticoagulants, heparin
What is neurogenic shock (rare) caused by?
Compression of the spinal cord e.g. after fall and unable to move limbs
What happens in neurogenic shock?
1) Spinal cord injury above T5 that interacts with both the parasympathetic and sympathetic system
2) Stimulates parasympathetic/inhibits sympathetic activity of vascular smooth muscle → widespread and massive vasodilation
What happens in spinal shock?
Injury to spinal cord → complete weakness, areflexia, lack of sensation below/at the lower cord/level of injury
What type of shock can pneumonia commonly lead to?
Septic shock
How would you treat a patient with septic shock resulting from pneumonia?
- Antibiotics (treat cause)
- Give fluid bolus to increase preload
- Increase BP by increasing SVR with medication (vasoconstriction)
