1. Fluids and Electrolytes in Pediatrics
Kathleen Asas, MD.MPH
Inpatient Pediatrics
Jan 2011

2. Objectives
To review basics of maintenance fluid and electrolyte requirements
To gain comfort in classification of dehydration and options for fluid support
To perform case-based practice!

3. Back to Basics….Fluid compartments
Total body water= ICF + ECF
Total body water =
60-75 % of Body weight

4. Important Concepts
Plasma Osmolality= Concentration of solutes in blood
Plasma Osmolality= 2 x plasma (Na)
Change in plasma osmolality --> change in ECF osmolality with water movement across cell membranes
Remember: The body has an immediate need to restore intravascular volume over osmolality.

5. Total Body Water Composition by Age

6. Concepts Maintenance: Normal ongoing losses of fluids and electrolytes
Deficit: Losses of fluids and electrolytes resulting from an illness
On-going Losses: Requirement of fluids and electrolytes to replace ongoing losses

7. Factors Increasing Maintenance Fluid Requirements
Factors Decreasing Maintenance Fluid Requirements
Fever-each 1 degree Celcius over 38 degrees increases maintenance fluid requirements by 12%
Hyperventilation
Increased temperature of the environment
Burns
Ongoing losses-diarrhea, vomiting, NG tube output
Skin: Mist tent, incubator (premature infants)
Lungs: Humidified ventilator
Mist tent
Renal: Oliguria, anuria
Misc: Hypothyroidism

8. Goal of Fluid Therapy To prevent dehydration
To prevent electrolyte abnormalities
To prevent protein degradation
To prevent acidosis and circulatory collapse

9. Calculation of Maintenance Fluid Requirements…the Holliday-Segar Method
Example:
A 30-kg child would require (100 × 10) + (50 × 10) + (20 × 10) = 1,700 cc/day
or (4 × 10) + (2 × 10) + (1 × 10) = 70 cc/h.

10. Maintenance Electrolyte Requirements
Na and K are the primary electrolytes that govern ECF and ICF osmolality.
[Na] in ECF = mEq/L, negligible in ICF [K] in ICF = 150 mEq/L, negligible in ECF
Maintenance Electrolyte Requirements:
Na: 2-3 mEq/100ml water /day
OR 2-3 mEq/kg/day K: 1-2 mEq/100ml of water/day
OR 1-2mEq/kg/day
Chloride: 2 mEq/100ml of water /day

11. Choosing the Appropriate IVF…let’s practice

12. Choosing MIVF..these are best estimates…
8kg infant: 8kg x 4ml/kg/hr 32 ml/hr
Na: 15-30mEq/L K: 8-15 mEq/L
D5 ¼ NS + 10meq 32 ml/hr
Wt-55 kg: Rate 95ml/hr
Na: mEq/L K: mEq/L
IVF: D5 ½ NS + 20 mEq 95ml/hr
3. Wt-80kg: Rate 120ml/hr
Na: mEq/L K: mEq/L
IVF: D5 ½ NS + 20mEq KCl/L @ 120ml/hr
Standard Na content in IVF:
NS (0.9% NaCl) = 154 mEq/l Na
½ NS (0.45% NaCl) = 77 mEq/l Na
1/3 NS (0.33% NaCl) = 51 mEq/l Na
¼ NS (0.25% NaCl) = 39 mEq/l Na
1/5 NS (0.2% NaCl) = 31 mEq/l Na
Standard K content in IVF:
10mEq KCl/L
20 mEq KCl/L
40 mEq KCl/L

13. DEHYDRATION…. Calculating Deficits

14. Concepts in Dehydration
Initial loss of fluid from the body depletes the extracellular fluid (ECF).
Gradually, water shifts from the intracellular space to maintain the ECF, and this fluid is lost if dehydration persists.
Acute Illness (<3 days ): 80% of the fluid loss is from the ECF and 20% is from the intracellular fluid (ICF).
Prolonged Illness (> 3 days): 60% fluid loss from ECF and 40% loss from ICF.

16. Pre-Illness Weight Estimate of Dehydration
Scenario 2: (In ER)
Need illness wt
% DHN based on exam
Step 1:
Calculate pre-illness wt (PIW):
Current wt = PIW wt
(1-% DHN)
Step 2: Calculate wt loss and respective deficit fluid volume
PIW-IW = wt loss
Note:
1kg ~ 1000ml fluid deficit
Deficit Fluid volume= 100cc/kg wt loss
Scenario 1 (if pre-illness wt known)
Need to accurately monitor patient weights frequently
Fluid deficit (L) = PIW (kg) – IW (kg)
(Generally 100cc/kg)
PIW = Pre-illness weight
IW = Illness weight
% Dehydration = PIW (kg) – IW (kg) x 100%
PIW (kg)

17. Maintenance Electrolytes

18. Oral Rehydration vs IVF…the Big Debate

19. Oral Rehydration: Key Concepts
Mild to moderate dehydration may be managed successfully with oral rehydration in the majority of cases.
Oral rehydration solutions should contain glucose and sodium in a ratio not to exceed 2:1
Amount of rehydration solution to be given is based on the estimated percentage of dehydration by weight.

20. Oral Rehydration Patient vomiting
– 5-10mL Q 5-10 minutes and increase as tolerated
Mild Dehydration
– Deficit replacement: 50 mL/kg over 4 hours
Moderate Dehydration
– Deficit replacement: 100 mL/kg over 4 hours

21. Developing a Plan of Action
Determine degree of dehydration
Establish phases (total of 3 phases- Resuscitation, Replacement, and Stabilization)

22. Phase II: Calculate maintenance & deficit fluid
Phase I: Resuscitation using Isotonic Fluids (NS/LR) at 20ml/kg.
Re-evaluation until urine output and dehydration signs improved
Phase II: Calculate maintenance & deficit fluid
Determine if Isotonic, Hypotonic or Hypertonic Dehydration
Hypertonic
Na >150
Replace fluids over 48hrs**
Hypotonic
Na <130
Isotonic
130< Na <150

23. Phase I – Resuscitation phase
Goal: Restore circulation, re-perfuse brain, kidneys
Mild-Moderate
 20 mL/kg bolus given over 30 – 60 minutes
Severe
May repeat bolus as needed (ideally up to 60ml/kg)
Fluids – something isotonic such as NS or lactated ringers (LR)

24. Phase II: Replacement Phase Phase III: Stabilization Phase (For Isotonic/Hypotonic Dehydration)
Goal: Replace deficit of fluids and electrolytes
Replacement Phase
1st 8 hrs
Stabilization Phase
Next 16 hrs
MIVF and
Maint Na
1/3
2/3
Deficit Fluid & Deficit Na
1/2

25. Hypertonic Dehydration Phase 2: Replacement Phase
Goal: Replace deficit of fluids and electrolytes
and daily maintenance
Amount: Deficits + daily maintenance Fluid:
Give over hours
IMPORTANT: Lower serum Na by no more than
10-12 mEq/L per day or <0.5mEq/L/hr

26. Hypertonic Dehydration
Phase 3: Stabilization Phase
Goal: Replace ongoing losses and transition towards maintenance therapy
Amount: Replacement + daily maintenance

27. Exceptions: Severe Hyponatremia
Serum Na < 120, CNS symptoms
Amount of 3# NaCl: (Desired Na-observed Na) x wt x 0.6L/kg
0.5mEq/L
Remember 3% NaCl (0.5mEq Na/ml)
The infusion should be given at a rate to increase the serum sodium by no more than 5 mEq/L/h and is often given more slowly over the course of 3–4 h
Do not replace Na faster than meq/L per 24hrs. Why?
Central pontine myelinosis: rapid brain cell shrinkage with rapid increase in ECF Na

28. Steps in Fluid Replacement
A. Phase I: Rapid Phase Restore intravascular volume a) Use Isotonic Fluid (NS/LR) b) Replace other components (Ca/glucose) separately based on documented deficit c) Volume: 10-20cc/kg; repeat up to 60cc/kg then re-evaluate B. Phase 2: Replacement Phase Determine type of dehydration based on Na-level (Isotonic, Hypotonic, or Hypertonic) a) Calculate 24-hr water needs Calculate maintenance water Calculate deficit water b) Calculate 24-hr electrolyte needs Calculate maintenance sodium and potassium Calculate deficit sodium and potassium c) Select an appropriate fluid (based on total water and electrolyte needs) Hypotonic and Isotonic Dehydration: Administer ½ calculated fluid during the 1st 8 hrs. Administer remainder over the next 16 hrs. C. Phase 3: Stabilization Replace ongoing losses as they occur (ex: diarrhea) a) Measure every 4-6 hrs and replace with appropriate fluids

29. Exceptions: Treatment of Hypernatremic Dehydration
Restore intravascular volume.
Determine time for correction based on initial [Na]:
[Na] mEq/L : 24 hr
[Na] mEq/L: 48 hr
[Na] mEq/L: 72 hr
[Na] mEq/L: 84 hr
Administer fluid at a constant rate over the time for correction
Typical fluids: D5¼ NS or D5 ½ NS (with 20mEq/L KCl unless contraindicated)
Follow serum Na
Sodium decreases too rapidly- Increase [Na] of IVF or decrease rate of IVF
Sodium decreased too slowly-Decrease [Na] of IVF or increase rate of IVF
***Lower serum Na by no more than mEq/L per day

30. Take Home Message
Oral rehydration is a safe and effective intervention in patients with mild-to-moderate dehydration who are able to tolerate oral regimen.
Fluid calculations are “best estimates.” Always monitor the effects of your interventions.
Deficit fluid requirements are based on classification of dehydration.
Hypotonic and isotonic dehydration are corrected in 8-hr and 16-hr blocks.
Hypertonic dehydration is corrected based on Na level (usually over 48hrs).
Slow correction of both hyponatremia and hypernatremia.

31. Let’s Practice!

32. Case: A 12 month old male is made NPO for surgery, wt-10 kg.
What would be his maintenance fluid and electrolyte requirement?

33. Case 1:
Wt: 10kg
Phase 1 (resuscitation): No resuscitation phase required
Phase 2 (replacement): Maintenance Fluid: 10 x 4cc/hr 40ml/hr (or 1000ml/day)
Maintenance Na:
2-3 mEq/100cc fluid 30 mEq Na/LD5 ¼ NS
Maintenance K: 1-2 mEq/100 cc fluid 10 mEq/L KCl
Maintenance fluid choice:
D5 ¼ NS + 10mEq KCl/L at 40ml/hr

34. Case 2
A 4 year old male presents with a history of vomiting and diarrhea. He has had 10 episodes of vomiting (clear then yellow tinged) and 8 episodes of diarrhea. The diarrhea is now watery and the last few episodes have been red in color. The diarrhea odor is very foul. He feels weak.
Exam: VS T 38.2 degrees (oral), P 110, R45, BP 90/65, oxygen saturation 100% in room air. Wt- 18 kg.
He is alert and cooperative, but not very active. He is not toxic or irritable. His eyes are not sunken. TMs are normal. His oral mucosa is moist but he just vomited. His neck is supple. Tachycardic, Bowel sounds are normoactive.
His overall color is slightly pale, his capillary refill time is 2 seconds over his chest, and his skin turgor feels somewhat diminished.

35. Questions Based on clinical criteria, what is his % dehydration?
Option 1 (Calculate PIW) 18kg/(1-0.05)= 18.9 (PIW)
18.9kg – 18kg= 0.9 (100ml x 0.9)
What method of fluid administration would you choose?
The parents are insistent on IV fluids. What would be your steps in fluid administration?
-Bolus of 20ml/kg
-Re-assessment
- IVF vs oral rehydration

36. An IV is started and a chemistry panel is drawn.
Phase I: resuscitation completed w/NS bolus
Phase II: Determined Isotonic Dehydration
Maint fluid: 1400ml
Maint Na: 3 mEq/100ml 42 mEq Na/1400ml 30mEq/L Na
Maint K: 2 mEq/100ml 28mEq K/1400ml-> 20mEq/L K
Deficit fluid in 5% DHN: 18 x 0.05 x 1000-> 900ml -360ml  540ml
< 3 days illness; 0.8 (900ml) 720ml (loss from ECF)
0.2 (900lm) 180ml (loss from ICF)
Deficit Na: [Na] in ECF × vol deficit [ECF}
135 x 0.720L  97 mEq Na – 55mEq Na (received) 42 mEq Na
Deficit K: [K] in ICF x proportion of fluid loss from ICF x deficit
150 x L  27 mEq K
1st Phase: NS bolus (360ml, 55mEq Na received)
2nd phase:
1st 8 hr: Replace 1/3 of maintenance Na + H20 + ½ deficit Na and H20:
Na: 10 mEq + 21 mEq-> 31mEq/735ml -> 42 mEq Na/L
465ml ml
K: 7mEq + 14mEq 21mEq/735 28mEq/L K
1st 8hrs: 735 ml of D5 1/3 NS + 25mEq 92ml/hr
Next 16hrs: Replace 2/3 maint Na + H20 AND ½ deficit Na + H20:
Na-> 20mEq+ 21mEq-> 41mEq Na/1205 ml 34mEq/L Na
D5 1/4 NS
K: 26mEq/1205ml 21mEq/L K
Next 16hrs: 1205 ml of D5 1/4 NS + 20mEq K/L at 75ml/hr
Oral versus IV rehydration is discussed with his parents who indicate that they have tried oral hydration and are not happy with the results so they would like
the IV for him.
An IV is started and a chemistry panel is drawn.
Na 135, K3.4, Cl 99, bicarb 15.
Wt-18kg.

37. Question 5:
DR is a 4 year old girl (16kg) who presents to the emergency room with fatigue,headache, generalized malaise, and severe gastrointestinal distress. The ER team gets a chem-7 and discovers her sodium to be 118. They would like to give 3% NaCl and ask you for a recommendation on how much to give, and at what rate.

38. Answer Amount of 3# NaCl: (Desired Na-observed Na) x wt x 0.6L/kg
0.5mEq/L
Remember 3% NaCl (0.5mEq Na/ml)
Goal to increase Na by no more than 5mEq/L
Calculation: ( ) x 16 x 0.6L/kg 134ml of 3% NaCl over 3-4 hrs
0.5 mEq/L

39. 5 kg child with 4-day h/o vomiting/diarrhea, 10% dehydration, [Na] of 128 mEq/L
Fluid volume Na
K (replacement over 2 days)
Maintenance
5 x 100= 500ml
3mEq/100ml fluid 15 mEq
2mEq/100ml
10 mEq K
Deficit
5 x 0.1 500ml
[ECF] loss 0.6 (500ml) 300ml
[ ICF] loss  0.4 (500ml) 200ml
[Na] in ECF x propor. Loss x fluid deficit +
[obs Na-desired Na x wt x prop Na loss]:
135 x 0.3L + [ x 5 x 0.6]
40mEq + 21 mEq 61 mEq
[K] in ICF x prop loss x fluid deficit:
150 x 0.2L  30 mEq K
Ongoing Losses
Replace cc: cc
Add Na in proportion to expected concentration in lost fluid (e.g., stool, gastric contents)
Add K in proportion to expected concentration in lost fluid (e.g., stool, gastric contents
Total
1st 8hrs:
Next 16 hrs:
1000ml
165ml + 250ml:
~ 400ml
600ml
= 76 mEq Na
5mEq mEq  35mEq Na/400ml:
165 ml ml mEq Na/L
10mEq Na + 30 mEq Na 40 mEq Na/600ml 66mEq Na/L
40 mEq K
18 mEq KCl/L
23 mEq KCl/L
Next 16hrs
D5 ½ NS + 20 mEq 50ml/hr
D5 ½ NS + 20mEq/L 35-40ml/hr

40. Determine adequate fluids for 7-kg child with 15%, Na=160
Fluid volume Na
K (replacement over 2 days)
Maintenance
700ml/day
3mEq/100ml fluid 21mEq Na
2mEq/100ml 14mEq K
Deficit
7 x 0.15= 1050ml
SFD= 630ml
FWD-420 ml
Free H20 deficit: 7kg x 4ml/kg x [Serum Na-desired Na] 420ml
Na: [Na in ECF] x prop Na loss x [Solute deficit]
[135 x 0.6] x [ ]=51 mEq Na
[K] in ICF x prop loss x fluid deficit 38mEq
Ongoing Losses
Replace cc: cc
Add Na in proportion to expected concentration in lost fluid (e.g., stool, gastric contents)
Add K in proportion to expected concentration in lost fluid (e.g., stool, gastric contents
1st 24hr
24-hr maint + ½ Free H20 deficit + SFD:
 1540ml
Solute Fluid + Elect Deficits
Total
Fluid Order:
Maint Na + Def Na
21mEq mEq 72 mEq
72mEq/1.54L 47 mEq Na/L
D5 1/3 NS + 30mEq 64ml/hr
14mEq
38mEq
52mEq/1.54L34mEq K/L
Next 24hrs
24-hr maint + ½ FWD
700ml + 210ml-> 910ml
21mEq Na/0.91L 23mEq Na/L
D5 ¼ NS + 15mEq 38ml/hr
14mEq/0.91ml 15mEq K/L

41. References
Fleisher, G. et al. (2005). Renal and Electrolyte Emergencies. In Cronan, K. & Kost (Eds), Textbook of Pediatric Emergency Medicine.
Kleigman, R. et al. Nelson Essentials of Pediatrics. Chapter 32: Fluids and Electrolytes. 5th edition. pp
Robertson, J. & Shilfoski, N. (2005). Fluids and Electrolytes. The Harriet Lane Handbook. (pp ).
Sykes, R. (2007). Pediatric Fluids and Electrolytes. [PowerPoint slides].