Table of Contents
Hyponatremic Dehydration (Na <130 mEq/L)
Here you calculate sodium deficit explicitly:Na⁺ deficit (mEq)=(135−Serum Na)×0.6×weight (kg)\textbf{Na⁺ deficit (mEq)} = (135 – \text{Serum Na}) \times 0.6 \times \text{weight (kg)}Na⁺ deficit (mEq)=(135−Serum Na)×0.6×weight (kg)
👉 135 mEq/L is taken as desired Na
Example
10 kg child, Na = 125 mEq/L(135−125)×0.6×10=10×6=60 mEq(135 – 125) \times 0.6 \times 10 = 10 \times 6 = \textbf{60 mEq}(135−125)×0.6×10=10×6=60 mEq
Important
- Correct slowly over 24–48 hrs
- Max rise: ≤8–10 mEq/L/day
- Give via DNS / NS + added Na as needed
Isonatremic Dehydration (Na 130–150)
No sodium deficit calculation needed
Instead calculate:
- Fluid deficit = % dehydration × weight × 10
Example:
- 10% dehydration in 10 kg child →
= 10 × 10 × 10 = 1000 mL deficit
Give:
- Deficit + maintenance + ongoing loss
- Usually NS / RL initially
Hypernatremic Dehydration (Na >150)
👉 Do NOT calculate sodium deficit
Instead calculate free water deficit:Water deficit (L)=0.6×wt×(Na145−1)\textbf{Water deficit (L)} = 0.6 \times \text{wt} \times \left(\frac{\text{Na}}{145} – 1\right)Water deficit (L)=0.6×wt×(145Na−1)
Example
10 kg child, Na = 1600.6×10×(160/145−1)≈6×0.103=0.62 L0.6 \times 10 \times (160/145 – 1) \approx 6 \times 0.103 = \textbf{0.62 L}0.6×10×(160/145−1)≈6×0.103=0.62 L
Key Pediatric Pearls (Exam Gold)
- Hyponatremia → calculate Na deficit
- Hypernatremia → calculate water deficit
- Isonatremia → calculate fluid deficit only
Correction Rules
- Hyponatremia: ↑ Na ≤8 mEq/day
- Hypernatremia: ↓ Na ≤10–12 mEq/day
- Rapid correction → ODS (hypo) / cerebral edema (hyper)
