Fluids and Electrolytes

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Fluids and Electrolytes

• TUMS-III Lecture Series
• M. Kwan Chan-House, MD

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Objectives

• Learn to calculate maintenance fluids
• Learn maintenance electrolyte needs
• Learn the signs and symptoms of dehydration
• Learn to calculate replacement fluids for
  isonatremic/hyponatremic/hypernatremic
  dehydration
• Oral Rehydration Therapy

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Just Start Maintenance

• Maintenance fluid provide the water and
  electrolytes equal to those lost simply for being
  alive and having a basal metabolic rate
• Metabolism makes heat and solute that you need to
  get rid of to maintain homeostasis
• Insensible fluid loss dissipates heat by
  evaporation of water from skin and URT (50 of
  maintenance needs)
• Soluble waste is excreted in urine (50 of
  maintenance needs)

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Some Conversions

• 1 mL 1 cc
• 30 cc 1 ounce

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Calculating Maintenance Fluids

• The Holliday-Segar Formula
• (Burn these numbers into your mind)
• 100-50-20
• 4-2-1

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Calculating Maintenance Fluids

• The Holliday-Segar Formula
• Based on calorie expenditure
• 1 mL of water needed for each kcal used

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Calculating Maintenance Fluids

• The Holliday-Segar Formula
• Case 1
• An 32 kg girl is admitted for elective surgery
  and is NPO. She has normal renal function, no
  diarrhea and no fever. What would her
  maintenance fluids be?

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Calculating Maintenance Fluids

• The Holliday-Segar Formula
• First 10 kg ? 100 ml/kg/day x 10
  1000 ml
• Second 10 kg ? 50 ml/kg/day x 10 500
  ml
• Last 12 kg ? 20 ml/kg/day x 12
  240 ml
• ________________________________________
• Total 32 kg
  1740 ml/day
• or
• 72.5 ml/hr

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Calculating Maintenance Fluids

• The Holliday-Segar Formula
• First 10 kg ? 4 ml/hr x 10 40
  ml
• Second 10 kg ? 2 ml/hr x 10 20 ml
• Last 12 kg ? 1 ml/hr x 12 12 ml
• ___________________________________
• Total 32 kg
  72 ml/hr

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Maintenance Electrolytes

• Electrolyte loss can all be considered urinary

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We all need some Sugar

• Glucose is added to
• Prevent ketosis
• Limit protein catabolism
• 20 of caloric need made up of glucose is
  sufficient to prevent severe catabolism
• 5 grams glucose for every 100 cal
• D5W (5 dextrose water) is an appropriate base
  for electrolyte solutions

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Putting it Together

• Maintenance IVF will need
• Water
• Glucose
• Sodium
• Potassium
• Chloride
• Your choices
• D5 0.2 NS with 20 mEq KCl/L (lt18 month old)
• D5 0.45 NS with 20 mEq KCl/L
• (PEARL Do not add KCl until after first void
  and potassium level is known)

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Dehydration

• Any combination of abnl intake and/or abnl losses
  can lead to dehydration
• Most common cause in pediatrics is diarrhea
• Types of dehydration
• Isonatremic
• Hyponatremic
• Hypernatremic

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Taking the History

• Vomiting
• Diarrhea
• Urine output (number of wet diapers)
• Decreased po intake
• Weight changes (acute)
• Fever
• Length of illness

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The Physical Exam

• Fever
• Elevated HR
• Orthostatic changes (?10 mmHg Diastolic BP and/or
  ?10 bpm from lying to standing)
• Sunken fotanelle
• Sunken eyes
• Lack of tears
• Dry lips/mucosal membranes
• Poor skin tugor (tenting)
• Prolonged capillary refill time/Skin color

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The Labs

• Lytes (Na, K, Cl, HCO3)
• BUN/Cr (ratio gt 20)
• Urine specific gravity
• Elevated hematocrit (hemoconcentration)
• FeNa

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Degree of Dehydration
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How dry are you?

• Only with accurate weights can you be precise
  how often does that happen?
• Level of dehydration can be estimated using the
  HP and labs

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A Case of Dehydration

• A 10 kg infant has had severe diarrhea for the
  past 2 days, decreased formula intake, a sunken
  fontenelle, no tears and oliguria.
• How dehydrated is this infant?
• What laboratory values do you want to obtain?
• How do you want to manage this infant?

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Management of Dehydration

• Step 1 Determine the presence and degree of
  dehydration
• Step 2 Obtain appropriate laboratory data
  (iso/hypo/hyper-natremia)
• Step 3 Bolus 20 mL/kg of NS (isotonic and will
  stay in the intravascular space)
• Step 4 Determine patients needs for next 24 to
  48 hours
• Maintenance Deficit On-going losses

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A Case of Dehydration

• This infant is 10 dehydrated given the history
  and PE findings
• Na 140, K 3.7, Cl 107, HCO3 22
• Bolus 20 mL/kg NS ? improved urine output
• Still refusing po intake and still stooling at a
  rate of 20 mL/hr
• Now what?

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A Case of Dehydration

• PEARL ? 1000 mL (1L) 1000 gm (1 kg)
• Maintenance 1000 mL (100 mL/kg/day)
• Deficit 1000 mL (10 of a 10 kg infant)
• 1000 mL 200 mL (bolus given) 800 mL remains
  to be given
• On-going losses 20 mL/hr ? 480 mL/day

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A Case of Dehydration

• For isonatremic and hyponatremic dehydration
• Give HALF of Maintenance and Deficit in first 8
  hours and remainder over the next 16 hours
• (Maintenance Deficit) Bolus 1800 mL
• Therefore Run 900 mL over 8 hours at 112 mL/hr
• Then, 900 mL over 16 hours at 56 mL/hr

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Hypernatremic Dehydration

• Total body water losses in excess of sodium
  losses
• Hypernatremia must be corrected SLOWLY
• Hyperosmolality causes cells to shrink
  especially in the CNS
• Correcting too quickly will cause fluid to be
  rapidly drawn into brain cells
• Cerebral edema is BAD

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Hypernatremic Dehydration

• A Case
• A 5 kg infant presents with a 5 day history of
  viral syndrome with fever, vomiting and diarrhea.
  Signs and symptoms reveal an infant who is 10
  dehydrated. Laboratory data reveals a Na of 160.

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Hypernatremic Dehydration

• Hypernatremic dehydration is corrected EVENLY
  over 48 hours
• Bolus 20 mL/kg to restore intravascular volume
• Maintenance 100 mL/kg x 5 kg 500ml/day
• 48 hours of maintenance 1000 mL
• Deficit 0.5 kg 500 mL
• 500 mL 100 mL (bolus given) 400 mL remain to
  be given
• Total fluids over a 48 hour period is 1400 mL or
• 29 mL/hr

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Oral Rehydration Therapy

• Indications
• lt10 dehydrated
• Following initial volume resuscitation
• Contraindications
• gt10 dehydrated/circulatory instability
• Severe vomiting
• Abdominal distention/ absent bowel sounds
• Severe hypo- or hyper- natremia

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Oral Rehydration Therapy

• Examples Pedialyte, Infalyte, WHO rehydration
  solution
• Administration
• 25 mL/kg/hr of deficit over the first 6 hours
• Then 10 mL/kg/hr over the next 6 hours (if
  needed)
• When repleted then maintenance volumes can be
  given

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ANY QUESTIONS ??