Anion-gap & Osmolar gap

HAGMA;  ↑ unmeasured acids (Lactate, ketones, ols, salicylate)

NAGMA: Bicarbonate loss (diarrhoea, RTA)

if(ratio) delta AG > delta HCO3; mixed Acidosis + Alkalosis

if(ratio) delta AG < delta HCO3; Acidosis + NAGMA

Osmolar gap:

Calculated osmolality = 2(Na) + Glucose/18 + Urea/2.8

Osmolar gap high → toxic alcohol 

High AG + High osmolar gap = Toxic alcohol ingestion until proven otherwise

Transfusion-related Electrolyte Disturbances:

1. Hypocalcemia - Citrate binds Ca2+

2. Hyperkalemia - Stored RBCs leak K+

3. Hypothermia worsens all: 

   1. • The liver metabolises citrate and frees calcium. Hypothermia slows liver metabolism (worsening hypocalcemia)

      • Warm circulation normally redistributes K⁺. Hypothermia decreases Na⁺/K⁺-ATPase activity

→ less potassium is driven into cells (worsens hyperkalemia)

• Hypothermia depresses cardiac conduction, --> susceptible to arrhythmia from K⁺ or Ca²⁺ imbalance, which becomes dramatically higher

Refeeding syndrome:

• Starvation → low intracellular ATP

• When carbs started → insulin surge pushes K⁺, Mg²⁺, PO₄³⁻ into cells

• Consequences 

  • ↓ PO₄³⁻ Respiratory failure

  • ↓ Mg²⁺ Arrhythmia, seizures

  • ↓ K⁺ Paralysis, VT

Prevention: Administer thiamine, PO₄, Mg, and K before feeding.

In starvation: 

• Low insulin

• Low intracellular glucose uptake

• Cell pumps downregulated

• Lower ATP demand

"Starvation does not preserve phosphate — it hides phosphate deficiency. When insulin returns, the deficiency becomes fatal"

Starvation → fat metabolism → low phosphate use but continued losses → total body phosphate depletion (masked in blood tests). Refeeding → insulin surge → inc cellular phosphate demand → phosphate shift into cells + no total stores → ATP synthesis fails → organ failure