4d452296-78f6-40ae-8c52-8c99311f9acd.jpeg
c2796578-bae3-4ccf-a967-1906bd84c9e3.jpeg
Pls help me to understand this example of hypernatremia correction
analyse_media
analyse_media
Here is a full, step-by-step breakdown of the example from the Pediatric Intensive Care Protocols of AIIMS.
The Patient
- Weight: 10 kg child
- Dehydration: 10% (= 1000 mL total fluid deficit)
- Serum sodium: 156 mEq/L (normal target = 140 mEq/L)
Step 1 - Calculate the Free Water Deficit
The formula used is:
Free Water Deficit = Total Body Water (TBW) × [(Actual Na / Target Na) - 1]
- TBW in a child = ~0.6 × body weight = 0.6 × 10 kg = 6 L
- Free Water Deficit = 6 L × [(156/140) - 1]
- = 6 × [1.114 - 1]
- = 6 × 0.114
- = ~686 mL
This 686 mL is pure water that has been lost in excess of sodium - it is the reason the sodium is high.
Step 2 - Calculate the Isotonic Fluid Loss
The total 1000 mL deficit is made up of two components:
- Free water deficit (hypotonic loss) = 686 mL
- Isotonic fluid loss = Total deficit - Water deficit = 1000 - 686 = 314 mL
Think of it this way: some of the dehydration is due to pure water loss (raising sodium), and the rest is isotonic salt + water loss (not affecting sodium concentration).
Step 3 - Resuscitation Bolus
If the child is haemodynamically unstable (shocked), resuscitation comes first:
- 20 mL/kg × 10 kg = 200 mL of normal saline was given as an initial bolus.
This bolus replaces isotonic fluid. So:
- Remaining isotonic deficit = 314 - 200 = 114 mL
The free water deficit of 686 mL is untouched by this bolus (normal saline doesn't correct the water deficit).
Step 4 - Plan the Rehydration (The Critical Part)
In hypernatremia, you cannot correct sodium faster than 0.5 mEq/L per hour (or ~10-12 mEq/L per day). Correcting too fast causes brain cells to swell, leading to cerebral oedema and seizures.
The strategy is to replace the free water deficit over at least 36 hours:
- First 24 hours: Replace 2/3 of the free water deficit
- Next 12+ hours: Replace the remaining 1/3
Step 5 - First 24-Hour Fluid Plan
Three components go into the first 24 hours:
| Component | Volume | Sodium |
|---|---|---|
| Free water deficit (2/3 of 686 mL) | 460 mL | 0 mEq |
| Remaining isotonic deficit | 114 mL | ~17 mEq |
| Daily maintenance (N/2 saline for 10 kg) | 1000 mL | ~30 mEq |
| TOTAL | 1574 mL | ~47 mEq |
- Rate = 1574 mL ÷ 24 hours = ~65 mL/hour
- Fluid chosen: 1/4 isotonic saline (N/4 saline)
Why N/4 saline? Because you need to deliver a large volume of mostly free water with just enough sodium to cover maintenance and the isotonic deficit - N/4 saline is dilute enough to do this while keeping the sodium correction rate safely below 0.5 mEq/L/hour.
Step 6 - Remaining 1/3 of Water Deficit (Next 12+ Hours)
- Remaining free water = 686 - 460 = 226 mL, given slowly over the next 12+ hours.
Key Safety Points
- Never correct sodium faster than 0.5 mEq/L/hour - too rapid correction causes cerebral oedema.
- Monitor serum sodium frequently during rehydration to titrate the infusion rate.
- If serum Na drops too fast and the child seizes, give 3-5 mL/kg of 3% saline slowly to raise sodium back up a little and protect the brain.
- Hypocalcaemia can occur during treatment - monitor calcium and give calcium gluconate if needed.
- In mild cases, oral rehydration works just as well - give twice the estimated deficit as WHO-ORS (or ORS:water 2:1) over 12-24 hours.
Summary in One Line
You split the deficit into free water (fixes high Na) and isotonic fluid (fixes volume), give the isotonic part quickly (bolus), then drip the free water in slowly over 36+ hours via dilute IV fluid (N/4 saline at ~65 mL/hr) to avoid overcorrecting the sodium too fast.
How to know how much percentage of dehydration
Reading File
Finding Sources
Finding Sources
Finding Sources
Reading File
Finding Sources
Finding Sources
Finding Sources
Reading File
Reading File
Reading File
Excellent - rich content retrieved. Here is the full breakdown:
How to Estimate the Percentage of Dehydration
The percentage is estimated clinically using symptoms, signs, and weight loss. There is no single lab test that reliably tells you the percentage.
The Gold Standard - Weight Loss
"The magnitude of acute weight loss reflects the amount of water loss and is the best clinical indicator of the degree of dehydration." - Brenner & Rector's The Kidney
If you know the child's recent well weight:
% Dehydration = [(Pre-illness weight - Current weight) / Pre-illness weight] × 100
Example: Child was 10 kg, now weighs 9 kg → (10 - 9) / 10 × 100 = 10% dehydrated
In practice, you rarely know the exact pre-illness weight, so you rely on clinical signs.
Clinical Grading by Age Group
Infants (under ~2 years)
| Grade | % Fluid Lost | Volume Lost |
|---|---|---|
| Mild | 5% | 50 mL/kg |
| Moderate | 10% | 100 mL/kg |
| Severe | 15% | 150 mL/kg |
Older Children and Adults
| Grade | % Fluid Lost | Volume Lost |
|---|---|---|
| Mild | 3% | - |
| Moderate | 6% | - |
| Severe | 9% | - |
Why lower thresholds in older children? Because they have relatively smaller TBW and ECF, so they manifest symptoms at a lower degree of fluid loss - Brenner & Rector's The Kidney
The Clinical Signs to Look For
Mild Dehydration
- Thirsty
- Slightly dry mucous membranes
- Otherwise normal exam
Moderate Dehydration
- Absent tears when crying
- Decreased urine output
- Tachycardia (earliest vital sign change)
- Capillary refill > 2 seconds
- Dry mucous membranes
- Sunken eyes
- Weak pulse
- Abnormal respirations
Severe Dehydration
- Abnormal mental status / lethargy / hypotonia
- Abnormal skin turgor (skin tenting - pinch the skin and it stays tented)
- Sunken anterior fontanelle (in infants)
- Hypotension
- Cool, mottled, cyanotic skin
- Absent urine output
- Shock
The 3 Most Reliable Clinical Signs (Evidence-Based)
According to a literature review cited in Brenner & Rector's, the 3 most predictive signs of 5% or more dehydration are:
- Delayed capillary refill time (> 2 seconds)
- Reduced skin turgor (decreased elasticity / tenting)
- Deep respirations (with or without increased rate - from metabolic acidosis)
A simpler bedside rule from Roberts & Hedges (2015 paper):
- 2 of 4 factors = at least 5% dehydration
- 3 or 4 factors = at least 10% dehydration
The 4 factors are: sunken eyes, decreased skin elasticity, weak radial pulse, abnormal general appearance.
A Useful Scoring Tool - Clinical Dehydration Scale (CDS)
Uses 4 features, each scored 0-2:
| Feature | 0 | 1 | 2 |
|---|---|---|---|
| General appearance | Normal | Thirsty, restless | Drowsy/limp |
| Eyes | Normal | Slightly sunken | Very sunken |
| Mucous membranes | Moist | Sticky | Dry |
| Tears | Present | Decreased | Absent |
- Score 0 = no dehydration
- Score 1-4 = mild dehydration
- Score 5-8 = moderate to severe dehydration
Important Caveat for Hypernatremic Dehydration
In hypernatremia specifically (like the example in your book), clinical signs underestimate the degree of dehydration. Water shifts from ICF to ECF to maintain the circulating volume, so the child may look less sick than they actually are. The skin turgor may even feel doughy or "thick" rather than dry. This is why the AIIMS book says the 10 kg child had 10% dehydration even though the signs may be less dramatic.
Summary
| Approach | Use when |
|---|---|
| Weight loss calculation | You have a known pre-illness weight |
| Clinical signs (3-point: CRT, turgor, respirations) | Bedside, no prior weight |
| Clinical Dehydration Scale | Systematic scoring in children |
| Lab (bicarb < 17 = moderate/severe) | Adjunct only, not primary |
Picture of sunken eyes
Finding Sources
Searching the Web
sunken eyes dehydration clinical photo child
Loading Image
Finding Sources
Here is a clinical photo of sunken eyes in a dehydrated infant:
What You Are Seeing
In this photo, notice:
- The eye sockets appear hollow and recessed - the eyes sit deeper than normal in the orbital cavity
- The upper eyelids look slightly droopy and the area around the orbit looks "caved in"
- The periorbital tissue has lost its normal fullness because the fat pads and surrounding tissues have lost water
Why Sunken Eyes Happen in Dehydration
When the body loses water:
- The orbital fat pads that normally cushion and support the eyeball become depleted of fluid
- The soft tissues around the orbit shrink
- This causes the eyeball to appear to recede backwards into the socket
Clinical Grading of Eye Sinking (WHO/CDS Scale)
| Eyes | Score | Dehydration Grade |
|---|---|---|
| Normal, full | 0 | No dehydration |
| Slightly sunken | 1 | Mild dehydration (~5%) |
| Very sunken and dry | 2 | Moderate-Severe dehydration (≥6-10%) |
As per the WHO IMCI guidelines, sunken eyes + skin pinch going back slowly = "Some Dehydration" (Plan B treatment), which corresponds to approximately 5-10% dehydration in an infant.
Bedside Tip
To assess eyes properly:
- Look at the child face-on at eye level
- Look for a shadow or hollow around the orbit
- Compare with a normal child - the eyes should look "forward-set" and full, not recessed
This is a shared conversation. Sign in to Orris to start your own chat.