Surgery - Fluids & Electrolytes Flashcards
What are the physiological limits of normal blood gases?
pH = 7.35-7.45 PaO2 = >10.6kPa PaCO2 = 4.7-6.0kPa HCO3- = 22-26mmol/L BE = +/-2mmol/L
What are the electrolyte values in serum?
Na = 135-145 K = 3.5-5 Ca = 2.2-2.6 Cl = 94-111 Latate = 1-2
What proportion of an adult body is water?
60%
What proportion of body water is ICF/ECF?
ICF = 2/3 (40% mass) ECF = 1/3 (20% mass)
What proportion of ECF is IF/Plasma/TCF?
Interstitial Fluid = 3/4 (15% mass)
Plasma = 1/4 (5% mass)
Transcellular Fluid = <0.5L
What are sensible losses?
Urinary fluid losses
What are insensible losses?
Losses from sweat, lungs & faeces
What are additional losses?
Losses from NG tubes, drains, stomas, 3rd space losses
What is the MOVU and how is it calculated?
Minimum obligatory volume of urine
0.5ml/kg/hr (1L/day)
How much fluid is lost as insensible losses?
Lungs + Faeces = 500ml
Sweat = 500ml
What is the average fluid requirement for an adult patient?
3L/day
What is the average electrolyte loss per day?
Na = 2mmol/kg/day K = 1mmol/kg/day
What is the average electrolyte requirement per day?
Na = 100mmol/day K = 60mmol/day
What is the standard fluid maintenance regime?
1 SALTY 2 SWEET
1L normal saline w/ 20mmol KCL over 8h
1L 5% dextrose w/ 20mmol KCL over 8h
1L 5% dextrose w/ 20mmol KCL over 8h
How much fluid should be added to the standard regimen for pyrexic patients?
10% per degree of fever
What are the main endogenous factors controlling Na & water excretion?
RAAS
ADH secretion from post pituitary
Describe RAAS
Decreased EABV –> decreased renal blood flow at juxta-glomerular apparatus –> release of renin
Renin cleaves Angiotensinogen –> AT1 –> ATII via ACE
ATII
What are the effects of Angiotensinogen II?
Efferent renal artery constriction Peripheral vasoconstriction Proximal Na reabsorption SNS activation Aldosterone release Thirst + ADH release --> CD water reabsorption
What are the Sx of dehydration?
Mild - headache, lack of energy, tiredness
Mod - dry mouth, decreased alertness, sunken eyes, muscle cramps
Sev - confusion, disorientation, tachycardia, tachypnoea, low BP
What is the electrolyte composition of 0.9% saline?
Osmolarity = 208 Na = 154mmol/L Cl- = 154mmol/L
What is the electrolyte composition of Ringers lactate/Hartmann’s?
Osmolarity = 278 Na = 131mmol/L K = 5mmol/L Ca = 2mmol/L Cl = 111mmol/L Lactate = 29mmol/L
What is the electrolyte composition of 5% dextrose in water?
50g dextrose in 1L pure water
What is the electrolyte composition of dextrose saline?
4% dextrose/0.18% saline
Osmolarity = 283
Na = 30mmol/L
Cl=30mmol/L
What is the electrolyte composition of 5% albumin?
Osmolarity = 300 Na = 150mmol/L Cl = 150mmol/L