Fluids & Electrolytes
Pediatric Emergency Medicine
Boston Medical Center
Boston University School of Medicine
Objectives
 To discuss:
 Maintenance
Fluids and Electrolyte Requirements

Types of Dehydration

Management of Dehydration

Electrolyte Abnormalities
Composition of Body
Compartments
 Total Body Water (TBW)= 50-75% of Total Body
Mass

TBW = Intracellular Fluid (ICF) + Extracellular Fluid (ECF)
 ICF = 2/3 of TBW
 ECF = 1/3 of TBW -- 25% of body weight

ECF = Plasma (intravascular) + Interstitial fluid
Body Water Compartments
Related to Age
80
70
60
50
TBW
ICF
ECF
40
30
20
10
0
0 years
1 year
10 years 20 years
Regulation of Body Fluids and
Electrolytes
 Mechanism to Regulate ECF volume

Anti-Diuretic Hormone (ADH)
•
•

Kidney = Increase water reabsorption
ADH secretion is regulated by tonicity of body
fluids
Thirst
•
Not physiological stimulated until plasma
osmolality is >290
Regulation of Body Fluids and
Electrolytes

Aldosterone
• Released from the adrenal cortex
– Decrease circulating volume
– Stimulation by Renin-Angiotensin Aldosterone axis
– Increase plasma K
• Enhanced renal reabsorption of Na in
exchange for K (>Na = expansion of ECF)

Atrial Natriuretic Factor
• Secreated by the cardiac atrium in response to
atrial dilatation (regulates blood volume)
• Inhibits Renin secretion
• Increase GFR and Na excretion
Daily Maintenance
Requirements
4cc, 2cc, 1cc rule



4 cc for the first 10 kg
2 cc for the next 10 kg
1 cc for each kg after

Example:
•
27 kg child
–
–
–
4 cc for the first 10 kg
2 cc for the next 10 kg
1 cc for each kg after
= 40cc
= 20cc
= 7 cc
67 cc/hr
Maintenance Requirements
 Maintenance Fluids: weight dependent
& age dependent:
 (NS =0.9% Saline =154 meq Na/liter)
 age
>2 -3 years: D5 0.5 NS + 20 meq
KCl/liter
 Up to age 2-3 years: D5 0.2 NS + 20 meq
KCl/liter
• D5 = 50 gm/liter = 5 g/dl
• Newborns often require D10 = 100 gm/liter = 10
gm/dl
Dehydration
 Epidemiology:

One of the most common medical problems

In the U.S. - 10% of all pediatric admissions

Worldwide, over 3 million children under 5
years die from dehydration
Estimation of Dehydration
Mild
Moderate
Severe
Weight Loss
3-5%
6-9%
>10%
Blood pressure
Normal
Orthostatic
Shock
Pulse
Normal
Increase
Tachycardic
Behavior
Normal
Irritable
Lethargic
Membranes
Moist
Dry
Parched
Tears
Present
Decrease
Absent
Cap. Refill
2 seconds
2-4 seconds
>4 seconds
Urine SG
>1.020
>1.030
Oliguria
Dehydration
 Classification

Isotonic
•

Serum Sodium 130-150 mEq
Hypotonic
•
Serum Sodium < 130 mEq
 Hypertonic
• Serum Sodium >150 mEq
Management of Dehydration
 General Principles:

Supply Maintenance Requirements

Correct volume and electrolyte deficit

Replace ongoing abnormal losses
Management of Dehydration
 Oral Rehydration:
 Effective for mild and some moderate
dehydrations
 Child may be able to tolerate PO intake
 Small aliquots as tolerated
•
•

Mild: 50 cc/kg over 4 hours
Moderate: 100 cc/kg over 4 hours
2 types of oral solution
•
•
Maintenance
Rehydration
Commercial Oral Solutions
Na mEq/L K mEq/L
Cl mEq/L Base
CHO %
Maintenance
 Reosol
50
20
50
Citrate
Glucose 2
 Ricelyte
50
25
45
Citrate
Rice syrup 3
 Pedialyte
45
20
35
Citrate
Glucose 2.5
Rehydration
 Rehydralyte
75
20
65
Citrate
Glucose 2.5
 W.H.O
90
20
80
HCO3
Glucose 2
For cholera use
Management of Dehydration:
IV
 Replacement of Fluid Deficit Based on %
Dehydration:
 Example: 5 kg child who is 6% dehydrated: 5 x
60cc/kg
• fluid deficit (cc) = wt x % dehydration
• fluid deficit (cc) = wt in kg (1000cc/kg) x (1/100)
estimate of dehydration
• fluid deficit (cc) = wt x 10 x estimate of dehydration
• fluid deficit (cc) = 5 x 10 x 6
• fluid deficit (cc) = 300 cc
Management of Dehydration:
IV
 Initial:
NS or LR 20 cc/kg Bolus in first hour
 Then Remainder of Deficit
• In previous example: total fluid deficit = 300cc
for 5 kg child who is 6% dehydrated = 60cc/kg
• Replacement:
– first hour: 20 cc/kg = 20 x 5 = 100 cc
– replace the rest: 40 cc/kg or 300 - 100 = 200 cc
– The type of fluid used and the rate of infusion
depends on the age and Na status of the patient:
» for isonatremic dehydration: correct deficits of
next 7 hours
» 200cc over 7 hours = 28 cc/hr
Hyponatremia
 Predisposing Factors







Diabetes mellitus (hyperglycemia)
Cystic fibrosis
CNS disorders ( SIADH)
Gastroenteritis
Excessive water intake (formula dilution)
Diuretics (thiazides and furosemide)
Renal disease
Hyponatremia
 Hyponatremic Dehydration

Hypovolemic Hyponatremic Dehydration
•
•

Euvolemic Hyponatremic Dehydration
•

High urine output and Na excretion
Increase in atrial natriuretic factor
ADH mediated water retention
Hypervolemic Hyponatremic Dehydration
•
•
Edematous disorder (nephrotic syndrome, CHF,
cirrhosis)
Water intoxication
Hyponatremia
 Acute Hyponatremia (<24 hours)

Early Onset (Serum Sodium <125 meq/L)
•
•
•

Nausea
Vomiting
Headache
Later or Severe (Serum Sodium <120 meq/L)
•
•
•
Seizure
Coma
Respiratory arrest
Hyponatremia

Chronic Hyponatremia (>48 hours)

Lethargy

Confusion

Muscle cramps

Neurologic Impairment
Hyponatremia
 Management




Na Deficit:
• Na Deficit = (Na Desired - Na observed) x 0.6
x body weight(kg)
Replace half in first 8 hours and the rest in the
following 16 hours
Rise in serum Na should not exceed 2 mEq/L/h to
prevent Central Pontine Myelinolysis (? Existence
in children)
In cases of severe hyponatremia (<120 mEq) with
CNS symptoms:
• 3% NaCl 3-5 ml/kg IV push for hyponatremia
induced seizures
– 6 ml/kg of NaCl will raise serum Na by 5 mEq/L
Hypernatremia

Hypernatremia leads to hypertonicity
Increase secretion of ADH
 Increase thirst


Patients at risk
Inability to secrete or respond to ADH
 No access to water

Hypernatremia

Etiology

Pure water depletion
•

Sodium excess
•

Salt poisoning (PO or IV)
Water depletion exceeding Na depletion
•

Diabetes insipidus (Central or Nephrogenic)
Diarrhea, vomiting, decrease fluid intake
Pharmacologic agents
•
Lithium, Cyclophosphamide, Cisplatin
Hypernatremia
 Signs and symptoms

Disturbances of consciousness
•

Lethargy or Confusion
Neuromuscular Irritability
•
Muscle twitching, hyperreflexia
Convulsions
 Hyperthermia

•
Skin may feel thick or doughy
Hypernatremia

Management


Normal Saline or Ringer lactate to restore volume
Hypotonic solution (D5 1/4 NS) to correct calculated
deficit over 48 hours
•
Water Deficit
–
•
Current body water
–
•
0.6 x body weight (kg) x Normal Na/Observed Na
Normal Body water
–

Normal body H20 - Current body H20
0.6 x body weight (kg)
Decrease Na concentration at a rate of 0.5 mEq/hr
or ~ 10 mEq/day: Faster correction can result in
Cerebral Edema
Potassium
 Most abundant intracellular cation
 Normal serum values 3.5-5.5 mEq
 Abnormalities of serum K are potentially life-
threatening due to effect in cardiac function
Hypokalemia

Diagnosis

Symptoms
•
•
•
Arrhythmias
Neuromuscular excitability (hyporreflexia, paralysis)
Gastrointestinal (decreased peristalsis or ileus)
Serum K < 3mEq/L
 ECG:

•
•
•
Flat T waves
Short P-R interval and QRS
U waves
Hypokalemia
Nutritional
GI Loss
Renal Loss
Poor intake
IVF low in K
Anorexia
Diarrhea
Vomiting
Malabsorbtion
Intestinal fistula
Laxatives
Enemas
Renal tubular acidosis
Chronic renal disease
Fanconi's syndrome
Gentamicin,
Amphotericin
Diuretics
Bartter's syndrome
Endocrine
Insulin therapy
Glucose therapy
DKA
Hyperaldosteronism
Adrenal adenomas
Mineralocorticoids
Bartter’s syndrome: Hypereninemia and hyperaldosteronism
Hypokalemia

Management:

Cardiac Arrhythmias or Muscle Weakness
•

KCl IV (cardiac monitor)
PO K - Depend of etiology
•
•
•
Hypophoshatemia = KPO4
Metabolic acidosis = KCl
Renal tubular acidosis = K citrate
Hyperkalemia
 Differential Diagnosis
Pseudohyperkalemia - from blood hemolysis
 Metabolic Acidosis
 Chronic Renal Failure
 Congenital Adrenal Hyperplasia

•
•

Females = Usually Dx at birth - Ambiguous
Genitalia
Males = Dehydration, hyponatremia, hyperkalemia
Medications
•
ACE inhibitors and NSAID’s
Hyperkalemia

Diagnosis:

Symptoms
•
•
•

Cardiac Arrhythmias
Paresthesias
Muscle weakness or paralysis
ECG
•
•
•
•
Peaked T waves
Short QT interval (K>6 mEq)
Depressed ST segment
Wide QRS (K>8 mEq)
Hyperkalemia

Management
Close cardiac monitoring
 Life -threatening hyperkalmia

•
•

Intravenous Calcium - rapid onset, duration< 30 min
NaHCO3 or glucose and insulin
Ion exchange resins
•
Sodium polystyrene sulfonate (Kayexelate)
–

PO or Enema
Hemodyalisis