Principles of fluid therapy Flashcards
Types of dehydration
Intravascular (hypovolaemia)
- Haemorrhage
- Vasculitis
Interstitial
- third space losses
- polyuria
- hypernatraemia
Intraellular
- hyperglycaemia/increased blood osmolarity
- loss of free water
Types of fluids
Hypotonic fluids
○ Fewer solutes than plasma, free water diffusing from plasma into RBCs
Isotonic fluids
○ Solutes concentration similar to that of plasma, RBCs size unchanged
Hypertonic fluids
○ Solutes concentration higher than that of plasma, water diffuses from RBCs to plasma (shrinking)
Crystalloid fluids
Contain solutes of small molecular weight
Solutes may be present at high concentrations and exert osmotic effects which can cause a signiicant water shift from one compartment to another
Biological memebranes are permeable to these solutes so the effects on the intravascular volumes are usually of short duration: one hour from infusion only 25% of the infused volume is retained into the vascular compartment - rest moved into interstitium
Can be used for replacement/resuscitation as well as maintenance
Different types of crystalloid fluids
Hartmann’s solution
Sodium choride (NaCl 0.9%)
Hypertonic sodium chloride (NaCl 7.2-7.3%)
NaCl 0.18% + Dextrose 4-5%
Hartmann’s solution
Concentrations of Na+ and K+ similar to that of plasma
Can be administered at large volumes and rates for the purpose of resuscitation and volume replacement
Slight alkinising effect (contains lactates)
Used for many purposes: hypovolaemia, interstitial dehydration, and peri-operatively fluid therapy
Sodium chloride (NaCl 0.9%)
Contains more Na+ and Cl- than plasma so not indicated for volume replacement
Use more conservative volumes and rates than Hartmann’s
Use cautiously in patients with heart and renal diseases
Acidifying solution
Hypertonic sodium chloride (NaCl 7.2-7.3%)
Produces a water shift from the red blood cells to plasma - they shrink - due to high concentration of solutes
Other effects:
- mild increase in cardia contractility
- decreased systemic vascular resistances
- potential impairment of coagulation
- anti-inflammatory properties
Used for small volumes sususcitation to produce large and rapid shifts from interstitial to the intravascular compartment
2-3ml/kg as boluses over 10-15 minutes
Effect will last 30-60 mins
NaCl 0.18% + Dextrose 4-5% (or glucose + H2O)
May be used for maintenance
Dextrose provides energy and calories
Once metabolised it releases water to restore cellular hydration
Crystalloids used for replacement/resuscitation
Hartmann’s
NaCl 0.9%
Acetate ringer
Plasma-lyte-R
Crystalloids used for resuscitation (small volumes)
NaCl 7.2%
Crystalloids used for maintenance
Plasma-lyte-M + dextrose 5%
NaCl 0.18% + Dextrose 5% + KCl 28 mEq/L
(Plasma)
Colloid fluids
Dextrane 40 (10%)
Dextrane 70 (6%)
Tetrastarch 6%
Succinilgelatines 4%
Colloids
Used to enhance circulating blood volume for a longer time than crystalloids
Longer lasting effect due to solutes with molecular weights high enough to prevent them from crossing the biological membranes
Natural or synthetic
Eventually will leave the bloostream after having been metabolised by the liver - 4-12 hours
Indication for colloid fluids
States of hypoproteinaemia and resulting low oncotic and colloid osmotic pressure
- protein losing enteropathy
- CKD
- liver dysfunction
- malnutrition
Can be used as surrogates for blood products
Succinyl gelatines
Most commonly used type of colloid
Derived from bovine bone marrow and well tolerated - rarely can get allergic reactions
For each ml infused, plasma vol increases by 2ml, usually lasts up to 4 hours
Possible hypocalcaemia
