This document summarizes fluid and electrolyte management. It provides normal ranges for electrolytes in plasma, interstitial, and intracellular spaces. It also outlines daily fluid requirements based on weight, maintenance IV fluids for postoperative patients, electrolyte concentrations in various secretions, and how to correct ongoing GI losses. As an example, it calculates the maintenance IV fluid order for a 70kg man on the first postoperative day requiring 500ml.

1. Fluid management

3. plasma interstitial intracellular
Cations
Na 140 146 12
K 4 4 150
Ca 5 3 10
Mg 2 1 7
Anions
Cl 103 104 3
HCO 24 27 10
SO4 1 1 -
HPO4 2 2 116
Protein 16 5 40

5. • Potassium ~50 - 60 meq (1meq/kg/day)
• Magnesium – 8-20 meq
• Sodium – ~100-120 meq (2meq/kg/day)
Fluid requirements
per day
Fluid
requirements per
hour
First 10kg 100 ml/kg 4 ml/kg
Second 10kg 50 ml/kg 2 ml/kg
Subsequent kgs 20 ml/kg 1 ml/kg
Adults ~ 1.5ml/kg per hour

7. Maintenace fluids in post operative
patients.
• 1st post op day – only 5% D
• 2nd post op day – add Na+
• 3rd post op day – add K+
Daily requirements = Normal maintenance + Abnormal losses
+ Pre-existing deficits

8. Secretions
Sodium
(mmol/L)
Potassium(m
mol/L)
Chloride
(mmol/L)
Bicarbonate
(mmol/L)
Salivary 50 20 40 50
Gastric 50 15 120 20
Duodenal 140 5 80 -
Biliary 140 10 100 40
Pancreatic 140 10 80 80
Jejuno-ileal 130 20 105 30
Faeces 80 10 100 25
Diarrhoea 100 30 50 60
Approximate electrolyte concentrations

9. • On going GI loss
• CORRECT WITH 0.9% NS and 20 meq K+
(1g=13 mEq)

10. • What will be the maintainance IV fluid order
for a 70 kg man. POD1. Ng=500ml.