SHOCK Flashcards
INDIRECT MEASUREMENTS OF PERFUSION
BLOOD pressure
consciousness - brain perfusion
urine output - renal perfusion
lactate - general tissue perfusion
how can Mean arterial pressure be calculated (MAP)
cardiac output (CO) X Systemic Vascular Resistance (SVR)
classifying shock
cardiogenic - pump issue
distributive - pipe problem
–> commonest, septic
hypovolaemic - filling problem
obstructive - blockage
hypovolaemic shock
acute haemrrhage
fluid depleted states - severe dehydration, burns
volume depletion leads to reduced SVR
- reduced volume returning to heart - (compensatory vasoconstriction) reduced pre-load + hence reduced CO
cardiogenic shock
“pump failure” - reduced CO
- reduced contractility -> reduced stroke volume
unless correctable pathology (valvular) - mortlity >75%
types of distributive shock
septic
anaphylaxis
neurogenic
obstructive shock
Mechanical obstruction to normal cardiac output in an otherwise normal heart
Direct obstruction to cardiac output
o PE
o Air/fat/amniotic fluid embolism
Restriction of cardiac fillung
o Tamponade
o Tension pneumothorax
gold standard monitoring of cardiac output
thermodulution with a PA catheter
- rarely used outside of specialised units
phase focus: salvage, optimisation, stabilisation, de-escalation
target MAP in treatment of shock
65-75mmHg
but relative to clinical picture
Hypertensive patients
Ongoing haemorrhage
choice of fluids
Crystalloids
o Convenient, cheap, safe
o Rapidly lost from circulation to extravascular spaces, significantly larger volumes needed
Colloids
o Cheap ish, reduce volumes requires
Can cause anaphylaxis, no evidence of benefit (Can cause harm)
Blood
o Oxygen carrying capacity, will stay in circulation
o Scarce resource, risks (immunogenic)
next line treatment when fluids don’t/stop working
need admit in critical care environment
vasopressors
- noradrenaline
- adrenaline
- vasopressin
de-esclation in hypovolaemic shock
- Remove extra fluid once shock has resolved
- Mortality benefit in getting patients “dry” as early as possible
- Various means – spontaneous, diuretic, dialysis
side effect of fluid resus
Ass with significant fluid admin + positive balance
Volume delivered never remains intravascular
o Extravascular overload in a intravascular “dry” patient
o Subcutaneous oedema obviously
Others – “wet” lungs/ARDS, bowel oedema, brain
reversible causes of shock
4Hs + 4Ts
hypoxia
hypovolaemia
hypo/hyperkalaemia
hypothermia
thrombosis
tamponade
tension pnuemothoraw
toxins
causes of obstructive shock
massive PE
cardiac tamponade
tension pneumothorax - pressure creates kink in aorta/vena cava
constrictive pericarditis
aortic stenosis
abdominal compartment syndrome
(recent thoracotomy, chest wall trauma, evidence of DVT)
management of obstructive shock
relieve obstructions
- thrombolysis / thrombectomy
- pericardiocentesis
distributive shock
umbrella term (septic, anaphylactic + neurogenic) where uncontrolled vasodilation overcomes the compensatory mechanism od increased CO
-> blood going but to wrong place
- Due to disruption of normal vascular autoregulation + profound vasodilatation
- Poor perfusion – despite increased cardiac output
- Regional perfusion differences
- Alteration of oxygen extraction
neurogenic shock
(NOT spinal)
loss of sympathetic nervous system tone
cord injury above T6 (below unlikely to get neurogenic shock) leading to lack of feedback
- sympathetic all way down spine, para just at top
bradycardia (uncontrolled vagal tone)
Mx hypovolaemic shock
Fluid and blood replacement
* DON’T give dextrose unless hypoglycaemic
* High flow o2
Stop the losses
* Haemorrhage control
* Treat the diarhoea
* Wrap the burns
Mx of cardiogenic shock
Careful fluid management, inotropes (eg. Dobutamine) vasopressors (eg noradrenaline) and treatment of the underlying cause eg PCI
Underlying cause
* PCI, thrombolysis thrombolysis if >2hrs
* Antiarrhythmias
Supportive measures
* Inotropes - increase contractility (how hard heart pumps)
* Vassopressors - vasoconstriction
* Mechanical
o Balloon pumps
o Ventricular assist devices
Cautious with fluids
mx of neurogenic shock
vasopressors
