Collapse Flashcards
What is the main pathophysiology characteristic of shock?
Low oxygen delivery to mitochondria.
O2 delivery requires an intact respiratory system, vascular system, heart, and enough haemoglobin-rich blood.
What is the formula for oxygen delivery
O2 delivery = blood flow * [Hb] * O2 saturation
What are the different types of shock?
Hypovolaemic shock
Cardiogenic shock
Obstructive shock
Maldstributive shock
What is hypovolaemic shock?
Shock caused by a sharp decline in cardiac output due to the circulation being empty, i.e. input < output
characteristic: evidence of fluid loss, and dry, empty circulation
What is cardiogenic shock?
Shock caused by failure of the heart itself.
Common causes include:
- ischaemic heart disease
- dysrythmias
- valvular disease
- inflammation of the heartmuscle
Raised venous pressure cause oedema in lungs and elsewhere
Characterised by: chest pain, ECG changes, ↑ upstream pressure, pulmonary + peripheral oedema
What is obstructive shock?
Shock caused by a reduction in cardiac output due to a blockage to the heart or major vessels
characterised by: similar to cardiogenic without signs of MI, may be PE, cardiac tamponad, tension pneumothorax, thoracic injury etc.
What is maldistributive shock?
Shock caused by abnormal dilatation of small arteries leading to a drop in BP, commonly due to infections (septic shock) or allergy (anaphylactic shock)
characterised by: signs of infection, and a warm, dilated circulation (unless severe)
What is the formula for Blood Pressure?
BP = Cardiac output * vascular resistance
What can a lack of vascualar tone cause?
Hypotension
Give examples which may trigger a cascade of events leading to septic shock.
Infection
Trauma
Burns
Pancreatitis
Describe the processes relating to septic shock?
Bacterial toxins or over-activation of immune response can lead to septic shock by:
Vessels become leaky => hypovolaemia => ↓CO until fluid replaced
Cardiac muscles suffer due to cytokine storm => ↓ CO
Tissue Hypoxia due to microvascular changes and intravascular coagulation
- even if corrected may => mitochondrial failure => cell death
Note: endothelial cells is where process goes awry causing secondary problems throughout the body
Describe some of the secondary problems caused by endothelium changes in septic shock?
CNS: encepolopathy
RS: ARDS (=non-cardiac pulmonary oedema)
CVS: hypotension, capillary leak
GI: leakage of bacteria into blood stream
GU: acute tubular necrosis, renal failure
Haematology: DIC, platelet and WBC deficiency, coagulopathy
Encodcrine: failure of hypopituitary-adrenal axis resulting in steroid deficiency
Describe the process relating to anaphylactic shock
Extreme type I hypersensitivity reaction to previously met antigen => massive degranulation of mast cells with release of histamine and other vaso-active substances
Systemic problem affects endothelium causing cap leak and decreased vascular tone.
Oedema and bronchospasm causes wheeze.
What are the characteristics of shock?
Collapse/prostration (lying flat on ground) Altered conscious level Tachypnoea Tachycardia Hypotension Poor peripheral perfusion, i.e. ↓CRT Low urine flow
Blood lactate levels will ↑ due to anaerobic metabolism
How should shock be treated?
Get help!
A - maintain and augment if required B - give O2 at 15L/min C - give ~1.5L Hartmann's bolus or 0.5L in cardiogenic shock D - don't forget glucose E - have a good look around
Inrease monitoring: pulse, BP, O2 sats, RR, Urine flow, fluid balance, conscious level
Antibiotics: urgent if infection suspected - high dose broad spectrum IV
Source control - fix iatrogenic causes of infection
IM adrenaline if anaphylaxis
Ensure good handover of care
