Fluids and Electrolytes in Pediatrics 1/7/11

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Kathleen Asas, MD.MPH
Inpatient Pediatrics
Jan 2011
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!
Back to Basics….Fluid compartments
 Total body water=
ICF + ECF
 Total body water =
60-75 % of Body
weight
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.
Total Body Water Composition
by Age
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
Factors Increasing
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
Factors Decreasing
Maintenance Fluid
Requirements
 Skin: Mist tent, incubator




(premature infants)
Lungs: Humidified ventilator
Mist tent
Renal: Oliguria, anuria
Misc: Hypothyroidism
Goal of Fluid Therapy
 To prevent dehydration
 To prevent electrolyte abnormalities
 To prevent protein degradation
 To prevent acidosis and circulatory collapse
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.
Maintenance Electrolyte Requirements
 Na and K are the primary electrolytes that govern ECF
and ICF osmolality.
[Na] in ECF = 135-145 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
Choosing MIVF..these are best estimates…
1.
2.
8kg infant: 8kg x 4ml/kg/hr 32
ml/hr
Na: 15-30mEq/L K: 8-15 mEq/L
D5 ¼ NS + 10meq KCl/L @ 32 ml/hr
Wt-55 kg: Rate 95ml/hr
Na: 45-68 mEq/L K: 22-45 mEq/L
IVF: D5 ½ NS + 20 mEq KCl/L @
95ml/hr
3. Wt-80kg: Rate 120ml/hr
Na: 57.6-85 mEq/L K: 28.8-58 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
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.
Pre-Illness Weight Estimate of Dehydration
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)
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
Maintenance Electrolytes
Oral Rehydration vs IVF…the Big Debate
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.
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
Developing a Plan of Action
 Determine degree of dehydration
 Establish phases (total of 3 phases- Resuscitation,
Replacement, and Stabilization)
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
Hypotonic
Na <130
Determine if Isotonic, Hypotonic or
Hypertonic Dehydration
Isotonic
130< Na <150
Hypertonic
Na >150
Replace fluids
over 48hrs**
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)
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
1/2
Hypertonic Dehydration
Phase 2: Replacement Phase
 Goal: Replace deficit of fluids and electrolytes
and daily maintenance
 Amount: Deficits + daily maintenance Fluid:
 Give over 24-48 hours
 IMPORTANT: Lower serum Na by no more than
10-12 mEq/L per day or <0.5mEq/L/hr
Hypertonic Dehydration
Phase 3: Stabilization Phase
 Goal: Replace ongoing losses and transition towards
maintenance therapy
 Amount: Replacement + daily maintenance
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 10-12 meq/L per 24hrs. Why?
Central pontine myelinosis: rapid brain cell shrinkage with rapid
increase in ECF Na
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
Exceptions: Treatment of Hypernatremic
Dehydration
 Restore intravascular volume.
 Determine time for correction based on initial [Na]:
[Na] 145-157 mEq/L : 24 hr
[Na] 158-170 mEq/L: 48 hr
[Na] 171-183 mEq/L: 72 hr
[Na] 184-196 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 10-12 mEq/L per day
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.
Case:
 A 12 month old male is made NPO for surgery,
wt-10 kg.
 What would be his maintenance fluid and electrolyte
requirement?
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
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.
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

 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.
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 0.180 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 270ml
K: 7mEq + 14mEq 21mEq/735 28mEq/L K
st
1 8hrs: 735 ml of D5 1/3 NS + 25mEq KCl/L @ 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
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.
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: (125-118) x 16 x 0.6L/kg 134ml of 3% NaCl over 3-4 hrs
0.5 mEq/L
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
[Na] in ECF x propor. Loss x fluid deficit +
[obs Na-desired Na x wt x prop Na loss]:
[K] in ICF x prop loss x
fluid deficit:
150 x 0.2L  30 mEq K
[ECF] loss 0.6
(500ml) 300ml
[ ICF] loss  0.4
(500ml) 200ml
135 x 0.3L + [135-128x 5 x 0.6]
40mEq + 21 mEq 61 mEq
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
1000ml
61 + 15 = 76 mEq Na
40 mEq K
1st 8hrs:
165ml + 250ml:
~ 400ml
600ml
5mEq + 30mEq  35mEq Na/400ml:
165 ml 250ml
87 mEq Na/L
18 mEq KCl/L
Next 16 hrs:
23 mEq KCl/L
10mEq Na + 30 mEq Na 40 mEq Na/600ml
66mEq Na/L
1st 8hrs:
D5 ½ NS + 20 mEq K/L @ 50ml/hr
Next 16hrs
D5 ½ NS + 20mEq/L KCl @ 35-40ml/hr
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 Nadesired Na] 420ml
Na: [Na in ECF] x prop Na loss x [Solute deficit]
[135 x 0.6] x [1050-420]=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:
700 + 210+ 630
1540ml
Maint Na + Def Na
21mEq + 51 mEq 72 mEq
14mEq
Solute Fluid + Elect
Deficits
Total
Fluid Order:
Next 24hrs
24-hr maint + ½ FWD
700ml + 210ml->
910ml
38mEq
72mEq/1.54L 47 mEq Na/L
D5 1/3 NS + 30mEq KCl/L @ 64ml/hr
52mEq/1.54L34mEq K/L
21mEq Na/0.91L 23mEq Na/L
14mEq/0.91ml 15mEq K/L
D5 ¼ NS + 15mEq KCL/L @ 38ml/hr
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.157-163.
 Robertson, J. & Shilfoski, N. (2005). Fluids and Electrolytes. The
Harriet Lane Handbook. (pp. 287-300).
 Sykes, R. (2007). Pediatric Fluids and Electrolytes. [PowerPoint slides].
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