Kathleen Asas, MD.MPH Inpatient Pediatrics Jan 2011.

Kathleen Asas, MD.MPHInpatient Pediatrics

Jan 2011

ObjectivesTo review basics of maintenance fluid and

electrolyte requirementsTo gain comfort in classification of

dehydration and options for fluid supportTo perform case-based practice!

Back to Basics….Fluid compartments

Total body water= ICF + ECF

Total body water = 60-75 % of Body weight

Important ConceptsPlasma 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

ConceptsMaintenance: 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

Factors Decreasing Maintenance Fluid Requirements

Fever-each 1 degree Celcius over 38 degrees increases maintenance fluid requirements by 12%

HyperventilationIncreased temperature

of the environmentBurnsOngoing losses-diarrhea,

vomiting, NG tube output

Skin: Mist tent, incubator (premature infants)

Lungs: Humidified ventilator

Mist tentRenal: Oliguria, anuriaMisc: Hypothyroidism

Goal of Fluid TherapyTo prevent dehydration To prevent electrolyte abnormalitiesTo prevent protein degradationTo 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/dayor (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/dayK: 1-2 mEq/100ml of water/day

OR 1-2mEq/kg/dayChloride: 2 mEq/100ml of water /day

1. 8kg infant: 8kg x 4ml/kg/hr 32 ml/hrNa: 15-30mEq/L K: 8-15

mEq/LD5 ¼ NS + 10meq KCl/L @ 32

ml/hr

2. Wt-55 kg: Rate 95ml/hr Na: 45-68 mEq/L K: 22-45

mEq/LIVF: D5 ½ NS + 20 mEq KCl/L @ 95ml/hr

3. Wt-80kg: Rate 120ml/hrNa: 57.6-85 mEq/L K: 28.8-58

mEq/LIVF: 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/L20 mEq KCl/L40 mEq KCl/L

Choosing MIVF..these are best estimates…

Concepts in DehydrationInitial 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 DehydrationScenario 1 (if pre-illness wt

known)Need to accurately monitor

patient weights frequentlyFluid 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 examStep 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 deficitDeficit Fluid volume= 100cc/kg wt loss

Maintenance Electrolytes

Oral Rehydration vs IVF…the Big Debate

Oral Rehydration: Key ConceptsMild 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 RehydrationPatient 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 ActionDetermine degree of dehydrationEstablish 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

Determine if Isotonic, Hypotonic or Hypertonic

Dehydration

HypotonicNa <130

Isotonic130< Na

<150

HypertonicNa >150Replace

fluids over 48hrs**

Phase I – Resuscitation phaseGoal: Restore circulation, re-perfuse brain,

kidneysMild-Moderate

20 mL/kg bolus given over 30 – 60 minutesSevere

May repeat bolus as needed (ideally up to 60ml/kg)

Fluids – something isotonic such as NS or lactated ringers (LR)

Phase II: Replacement PhasePhase III: Stabilization Phase

(For Isotonic/Hypotonic Dehydration)

Goal: Replace deficit of fluids and electrolytes

Replacement Phase1st 8 hrs

Stabilization PhaseNext 16 hrs

MIVF and Maint Na

1/3 2/3

Deficit Fluid & Deficit Na

1/2 1/2

Hypertonic DehydrationPhase 2: Replacement Phase

Goal: Replace deficit of fluids and electrolytesand daily maintenance

Amount: Deficits + daily maintenance Fluid:Give over 24-48 hoursIMPORTANT: Lower serum Na by no more

than10-12 mEq/L per day or <0.5mEq/L/hr

Hypertonic DehydrationPhase 3: Stabilization Phase Goal: Replace ongoing losses and transition

towards maintenance therapyAmount: Replacement + daily maintenance

• Serum Na < 120, CNS symptomsAmount 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 ReplacementA. Phase I: Rapid Phase Restore intravascular volume

a) Use Isotonic Fluid (NS/LR)b) Replace other components (Ca/glucose) separately based on documented deficitc) Volume: 10-20cc/kg; repeat up to 60cc/kg then re-evaluate

B. Phase 2: Replacement PhaseDetermine type of dehydration based on Na-level (Isotonic, Hypotonic, or Hypertonic)a) Calculate 24-hr water needs Calculate maintenance water Calculate deficit waterb) Calculate 24-hr electrolyte needsCalculate maintenance sodium and potassiumCalculate deficit sodium and potassiumc) 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 correctionTypical 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 MessageOral 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: 10kgPhase 1 (resuscitation): No resuscitation phase

requiredPhase 2 (replacement): Maintenance Fluid: 10 x

4cc/hr 40ml/hr (or 1000ml/day)Maintenance Na:

2-3 mEq/100cc fluid 30 mEq Na/LD5 ¼ NSMaintenance K: 1-2 mEq/100 cc fluid 10 mEq/L

KClMaintenance fluid choice:

D5 ¼ NS + 10mEq KCl/L at 40ml/hr

Case 2A 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 NaMaint K: 2 mEq/100ml 28mEq K/1400ml-> 20mEq/L KDeficit 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 deficit150 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 270mlK: 7mEq + 14mEq 21mEq/735 28mEq/L K

1st 8hrs: 735 ml of D5 1/3 NS + 25mEq KCl/L @ 92ml/hrNext 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 NSK: 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.

AnswerAmount 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

[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 + [135-128x 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:~ 400ml600ml

61 + 15 = 76 mEq Na

5mEq + 30mEq 35mEq Na/400ml: 165 ml 250ml 87 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

1st 8hrs:

Next 16hrs

D5 ½ NS + 20 mEq K/L @ 50ml/hr

D5 ½ NS + 20mEq/L KCl @ 35-40ml/hr

Determine adequate fluids for 7-kg child with 15%, Na=160Fluid 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= 630mlFWD-420 ml

Free H20 deficit: 7kg x 4ml/kg x [Serum Na-desired Na] 420mlNa: [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

Solute Fluid + Elect DeficitsTotalFluid Order:

Maint Na + Def Na21mEq + 51 mEq 72 mEq

72mEq/1.54L 47 mEq Na/LD5 1/3 NS + 30mEq KCl/L @ 64ml/hr

14mEq

38mEq

52mEq/1.54L34mEq K/L

Next 24hrs 24-hr maint + ½ FWD700ml + 210ml-> 910ml

21mEq Na/0.91L 23mEq Na/L

D5 ¼ NS + 15mEq KCL/L @ 38ml/hr

14mEq/0.91ml 15mEq K/L

ReferencesFleisher, 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].