Fluid Resuscitation Flashcards
define hypotension
it is difficult to classify but generally
- a BP <90/60 mmHg
- >40 mmHg below normal
how does hypotension occur in sepsis
- bacteria produce toxins which stimulate the immune system to produce cytokines eg TNF alpha
- these increase NO production in vascular smooth muscle which causes vasodilation
- fall in TPR, leads to a fall in BP = TPR x CO(=HR x SV)
- endothelial dysfuntion and capillary leak leads to decreased intravascular volume
NO production
- continuously produced by vascular endothelium from amino acid L-arginine through NOS enzyme
- potent vasodilator, short action
- shear stress on vascular endothelium stimulates calcium release from vascular endothelial cells and activation of NOS
consequences of hypotension
- Leads to hypoperfusion in tissues which causes hypoxia and organ dysfunction
- Hypoxia leads to anaerobic metabolism, which produces lactic acid as a byproduct
- This causes a progressive metabolic acidosis with a raised anion gap, which leads to detrimental effects:
detrimental effects of metabolic acidosis
- exacerbates vasodilatation , reducing TPR further
- decreased myocardial contractility, reducing CO
- generalised impaired function of cells
what does hypoperfusion cause in kidneys
acute kidney injury
immediate fluid management - sepsis 6
- 500ml 0.9% saline STAT
- repeat boluses of fluid as required
signs of hypovolaemia
- Cool peripheries (though may be warm)
- Clammy
- Dry mucous membranes
- Decreased JVP
- Tachycardia
- Hypotension, postural drop is evident first
- Skin turgor
- Mottling of skin
- Poor urine output
monitoring of fluid
- HR, BP, RR
- Sepsis 6: serum lactate and urine output
what is the normal serum lactate level
<1.8 mmol/L
what does elevated lactate suggest
- tissue hypoperfusion/hypoxia - anaerobic metabolism
- in the context of sepsis, suggests severe illness or organ dysfunction as a result of tissue hypoperfusion
how is urine output best monitored
- urinary catheter - more accurate and can give hourly volumes
- also option of recording urine volume
normal urine output
should be at least 0.5ml/kg/hr
(heavier patients produce more)
anything less than this is oliguria
what does oliguria indicate in sepsis
renal hypoperfusion
crystalloid fluids
- eg 0.9% NaCl and Hartmanns solution
- cheap and widely available
Hartmanns solution
a crystalloid that contains additional electrolyes
generally only used for surgical procedures
colloids fluids
- eg Gelofusin
- theoretically, should maintain oncontic pressure, however this does not translate in practice
- expensive
which fluids carry a small risk of anaphylaxis
colloids and albumin (colloids>)
albumin
- a natural colloid that maintains oncotic pressure
- derived from donated blood samples
- there is a small risk of infection - HepC
where is albumin made
liver
blood as a fluid
- the most physiological colloid
- increases oxygen carrying capacity
- scarce resource
what is there a risk of with blood fluid replacement
- there is a risk of transfusion reaction - type II hypersensitivity
- Anti-blood group Ab bind to the surface of circulating donor RBCs
- There is an overwhelming systemic inflammatory response, which can occur after only 1ml of blood has been transfused
what should never be used in fluid resuscitation
dextrose 5% - exits the intravascular space took quickly to do any good
how much fluid do most patients require to restore euvolaemia
- 2l
- if in doubt, always give too much rather than too little
how can overload oedema be managed
- loop diuretic eg IV furosemide
- inhibit NaCl transporter in the Loop of Henle, decreasing blood volume
further management of a patient who is still hypotensive despite optimized fluid resuscitation/euvolaemia restored
- inotropic support/vasoconstrictors eg nor/adrenaline
- cause vasoconstriction ± increased myocardial contractility
- adminstered through a central venous catheter in HDU/ICU
