SEPT 13 Built from the handwritten pages you uploaded on 13 September 2026.

Nutrition, IV fluids & refeeding

Daily requirements, calculating a feed for a 70 kg adult, refeeding syndrome, and the tonicity and composition of common IV fluids.

Daily requirements — adult

Item	Requirement	Note
Water	100 ml/kg first 10 kg · 50 ml/kg next 10 kg · 20 ml/kg thereafter, per day	Holliday–Segar. 70 kg → 1000 + 500 + 1000 = 2500 ml/day (≈ 30–35 ml/kg)
Energy	25 kcal/kg/day	70 kg → 1750 kcal
Protein	1.0–1.5 g/kg/day	Upper end in critical illness
Nitrogen	0.13–0.24 g/kg/day	1 g nitrogen = 6.25 g protein
Glucose	≈ 2 g/kg/day	Target blood glucose 6–10 mmol/L (108–180 mg/dL)
Fat	Up to 2 g/kg/day	About 40% of total calories
Na⁺ · Cl⁻	1.0–2.0 mmol/kg/day each	Roughly 1 mmol/kg in practice
K⁺	0.7–1.0 mmol/kg/day	Roughly 1 mmol/kg in practice
Ca²⁺ · Mg²⁺	0.1 mmol/kg/day each	≈ 10–15 mmol/day
PO₄³⁻	20–30 mmol/day	The one refeeding drops fastest

Substrate	kcal/g	Note
Carbohydrate	3.7	Dextrose monohydrate in IV fluids gives ≈ 3.4
Protein	5.1 on your page · 4 in most texts	Burned in a calorimeter, protein gives ≈ 5.3; the body gets only ≈ 4 because urea is excreted unburned. Use 4 unless your source says otherwise.
Fat	9	The most energy-dense

1
Total energy
70 × 25 = 1750 kcal/day
2
Protein
70 × 1.5 = 105 g → 105 × 5.1 = 535 kcal
3
Fat — 40% of calories
0.4 × 1750 = 700 kcal → 700 ÷ 9 = ≈ 78 g
4
Carbohydrate — the remainder
1750 − (535 + 700) = 515 kcal → 515 ÷ 3.7 = ≈ 139 g

Your page calls 25 kcal/kg the Harris–Benedict equation. Strictly, Harris–Benedict estimates basal metabolic rate from sex, weight, height and age; 25 kcal/kg/day is the simpler weight-based estimate used on ICU.

The burns and fever figures match standard teaching. Many texts give higher figures for sepsis and major surgery (roughly +20–50% for sepsis), so check against your source before relying on 9% and 6%.

Starvation depletes intracellular electrolytes, but serum levels stay normal.
Carbohydrate is restarted → insulin surges → phosphate, potassium and magnesium are driven into cells → serum phosphate, potassium and magnesium fall.
Carbohydrate metabolism also consumes thiamine, which can precipitate Wernicke's.
Starvation also causes intestinal villous atrophy — one reason to restart the gut early.

Hypophosphataemia is the hallmark → respiratory muscle weakness and respiratory failure, cardiac failure, arrhythmias, seizures, rhabdomyolysis, haemolysis.
Hypomagnesaemia and hypokalaemia add to the weakness and arrhythmias.
Sodium and fluid retention → oedema, cardiac failure. At worst, death.

Start at 25–50% of calculated requirement and build up over 3–4 days. (NICE: no more than 10 kcal/kg/day in high risk, 5 kcal/kg/day in extreme risk.)
Thiamine and vitamin B supplementation — before feeding and for the first days.
Replace phosphate, potassium and magnesium, checking levels daily.

Osmolarity in the bag. Roughly: hypotonic < 250, isotonic ≈ 280, hypertonic > 315 mOsm/L.

5% dextrose is isotonic in the bag but hypotonic in the body — the glucose is metabolised and leaves free water.
Likewise dextrose–saline mixtures are hypertonic in the bag but behave according to their saline content once the glucose is used. Your page lists 5% dextrose in 0.225% saline as isotonic — that is how it behaves in the body, not in the bag.

Fluid	Na⁺	Cl⁻	K⁺	Ca²⁺	Lactate	mOsm/L
0.9% NaCl	154	154	0	0	0	308
Ringer's lactate	130	109	4	1.4–2	28	273
Plasma, for comparison	140	100	4	2.2 total	< 2	285–295

Saline has no K⁺ and no lactate, and its chloride of 154 is why large volumes cause a hyperchloraemic acidosis.
Ringer's contains calcium, so avoid running it through the same line as citrated blood.

100/50/20 ml/kg/day water

25 kcal/kg/day

1–1.5 g/kg protein

6.25 g protein per g N

9 / 4 / 3.7 fat · protein · carb

PO₄ refeeding hallmark

Thiamine before feeding

308 · 273 NS · RL