Lecture 12 - IV fluids Flashcards
TBW percentage in men
60% - 42L
TBW percentage in women
55%
Less muscle mass and more fat
TBW percentage in elderly
50%
Less muscles mass
Decreased regulation of fluid
TBW percentage in babies
75% - dehydrate quicker
Hypotonic
Less solutes in ECF therefore water diffuses into cells causing swelling
Hypertonic
More solutes in ECF therefore water diffuses out of the cell causing lysis
Hypernatraemia presentation
Confusion
Seizures
Cell shrinkage as ECF is hypertonic so water moves out of cells
Hyponatraemia presentation
Cerebral oedema
Headaches
Seizures
Cell swelling as ECF is hypotonic so water moves into cell
Worse for neurones
Dextrose osmotic and tonic activity
Isosmotic but not isotonic
- Glucose is metabolised by cells therefore cell becomes more hypotonic as water left behind
In which compartments does glucose get taken up in?
All compartments
0.9% saline osmotic and tonic activity
Not isosmotic as slightly higher osmolarity but considered isosmotic
Isotonic
In which compartments does Na+ get taken up in?
ECF only
0.9% saline
Used in fluid resuscitation
5% dextrose
Used as maintanence
Hartman’s
Isotonic and Isomotic
Better reflection of blood
Lactate is metabolised to bicarbonate
In which compartments does Hartman’s get taken up in?
ECF only
4% dextrose/ 0.18 saline - mixed
800ml - 5% dextrose
200ml - Saline
Isosmotic not isotonic
In which compartments does 4% dextrose /0.18% saline taken up in?
800 ml - Spread across all compartments
200 ml - ECF only
Why do patients need IV?
Nill by mouth Dehydration Fluid loss Abnormal electrolytes can be correctly quickly with IV GIT defect
Hospitalised patients
Increased ADH stimulated by:
- pain
- nausea
- drugs (morphine)
- low effective circulating volume
Generally do not sweat excessively
RAAS and catecholamines activated - stress response increasing water retention
Reduced calorie expenditure - inactive
Daily losses
Urine - 1- 2.5 L
Water - 30ml/kg
Sodium - 1-2mmol/kg
Potassium - 0.5 - 1 mmol/kg
Chloride - 1 mmol/kg
Glucose - 50 - 100g (1L)
Considerations for daily losses
Age - elderly lose less
Size
Vomiting
Loses a lot of Cl- ions
Diarrhoea
Loses a lot of HCO3- , K+ and Na+
