Fluids & Electrolytes

Dr Ahmed SafwatNeonatology department

Objectives

To discuss:

♦ Physiology of body fluid compartments

♦ Maintenance IV fluid requirements

♦ Types of Dehydration

♦ Management of Dehydration

♦ Electrolyte Abnormalities

Composition of Body Compartments

Total Body Water represents 50 - 75% of Total Body

Mass• ICF: 2/3 of TBW

• ECF (Plasma - intravascular + Interstitial fluid ): 1/3 of TBW

Body Water Compartments Related to Age

0

10

20

30

40

50

60

70

80

0 years 1 year 10 years 20 years

TBW

ICF

ECF

Distribution of Body Water

Intravavascular

Interstitial

IntracellularICF

ECF

K+

Na+

CL-

Extracellular Intracellular

Cations (+) Anions (-) Cations (+) Anions (-)

Na (99%) CL (70%) K (78%) PO4/Org (56%)

K (3%) HCO3 (16%) Mg (12%) Proteins (37%)

Ca (3%) Proteins( 10%) Na (7%) Hco3: (5%)

Mg (2%) PO4/Org (4%) Ca (3%) Cl (2%)

Regulation of Body Fluids and Electrolytes

♦ Anti-Diuretic Hormone (ADH)• Secretion is regulated by tonicity of body fluids• Increases water reabsorption by the kidneys

♦ Thirst • Physiological stimulation only occurs when plasma

osmolality is 290 mosmol/lit>

♦ Aldosterone• Released from the adrenal cortex

– Stimulation by Renin-Angiotensin - Aldosterone axis– ,, ,, Decrease circulating volume– ,, ,, Increase plasma K

• Action: Enhanced renal reabsorption of Na in exchange for K ( Na = expansion of ECF)>

♦ Atrial Natriuretic Factor• Secreted by the cardiac atrium in response to atrial dilatation • Action: Regulates blood volume by reducing water, sodium in

the circulatory system by inhibition of Renin & vasopressin secretion & by Increasing GFR and Na excretion

• Plasma Osmolality = Concentration of solutes in blood

• Normal plasma osmolarity = 280 - 295 mosmol/lit.

• Calculated Plasma Osmolality = 2 x (Na + K) + Glucose + Urea

• Causes of Hyperosmolarity :- Hypernatremia- Hyperglycemia- Uremia• Effects of Hyperosmolarity:- Cellular disruption- Systemic acidosis - Cytotoxic brain edema- Renal failure

Commonly Used IV Fluid Solutions

Solution Electrolyte Content (mEq/lit)Na CL K Ca Lactate

Glucose (gm/lit)/ Osomlarity

Ringer’s Lactate

130 109 4 2.7 27.7 273 mosmol/lit

Sodium Chlor ide 3% 300 616 mosmol/lit

Normal Saline 0.9% 154 154 308 mosmol/lit

I/2 Normal Saline 0.45% 77 77 154 mosmol/lit

D5: Saline 0.45% 77 77 5.5gm 431 mosmol/lit

D5: Saline 0.225% 38.5 38.5 5.5gm 354 mosmol/lit

D5: Saline 0.18% 30.8 30.8 5.5gm 339 mosmol/lit

D10% 11gm 555 mosmol/lit

D5% 5.5gm 277 mosmol/lit

Daily Maintenance Requirements Body Weight:

0-10 kg 10-20 kg >20 kg

Total Water Volume:

100 ml/kg/d 1000 ml + 50 ml/kg for each kg above 10 kg

1500 ml + 20 ml/kg for each Kg above 20 kg

Sodium: 3 meq/kg/d 3 meq/kg/d 3 meq/kg/d

Potassium: 2 meq/kg/d 2 meq/kg/d 2 meq/kg/d

Chloride: 5 meq/kg/d 5 meq/kg/d 5 meq/kg/d

For quick calculations: Rate of Infusion :(4cc, 2cc, 1cc ) X BW

• 4 ml for the first 10 kg• 2 ml for the next 10 kg• 1 ml for each kg after

Example:27 kg child

– 4 cc for the first 10 kg = 40ml– 2 cc for the next 10 kg = 20ml– 1 cc for each kg after = 7 ml

Rate of IVFs = 67 ml/hr

Maintenance Fluids Weight & age dependent:

Age 2 - 3 years: >D5: NS (0.45 sol) + 20 mEq KCl/liter½(add 1ml KCL to each 100ml IVFs)

Up to age 2 - 3 years: D5:1/4 NS (0.225 sol) + 20 mEq KCl/liter(add 1ml KCL to each 100ml IVFs)

NB: - The amount of KCL in IV solution should not exceed 35 - 40mEq/lit- KCL should not be added to patients with suspected renal failure except

after adequate urine flow is obtained.

The amount is increased in the following conditions

The amount is decreased in the following conditions

1. Fever: Add 10% for each degree above 38%

1. CNS infection or brain edema: Subtract 30%

2. Phototherapy: Add 10%

2. Heart failure: Subtract 30%

3. Infants placed under radiant warmer: Add 20%

3. Mechanical ventilation: Subtract 10%

4. Continued losses as diarrhea: Add 30%

5. Burns

4. Severe oligurea or anuria: Give only the insensible water losses = (300ml/m2)

Body surface area calculation

( BW x 4 ) + 7BW + 90

E.g.: Body surface area for a 10 kg child = 0.47m2

Practical Examples

A 2.5 years old child ,15 Kg was kept NPO after tonsillectomy operation?

• Solution used: D5:1/4 NS (0.25%) + KCL

• Amount/day: (10 x 100) + (5 x 50) = 1250ml/day Add KCL 1ml for each 100ml (add 12ml KCL over the solution).

A 10 kg infant with Severe acute congestive heart failure?

• Solution used: D5 :1/4 NS (0.25%)+ KCL

• Amount/day: (10 x 100) =1000ml/day Add KCL 1ml for each 100ml (add 1ml KCL over the solution).

• Subtract 30% (300ml) from the total amount, so the amount is 700 ml/day.

DehydrationEpidemiology:

♦ One of the most common medical problems

♦ Worldwide, over 3 million children under 5 years die

from dehydration

Fluid Losses in Infants

LUNGS

URINE, FEACES, Vomiting SKIN

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

DehydrationClassification:

♦ Isotonic

Serum Sodium 130 -150 mEq

♦ Hypotonic

Serum Sodium 130 mEq<

♦ Hypertonic

Serum Sodium 150 mEq>

Assessment of dehydration

• Vital signs• Weight

• Urine output.• Behavior—changed—Response to stimuli• Skin changes• General Body assessment—sunken eyes,

no tears, sunken fontanel

Management of Dehydration

General Pr inciples:

♦ 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 is able to tolerate oral intake♦ Small amounts 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 For cholera use

90 20 80 HCO3 Glucose 2

Management of Dehydration: By IV infusion

1. Replacement of Fluid Deficit Based on % Dehydration.

2. Initial: NS or LR 20 cc/kg Bolus in first hour3. Then Remainder of Deficit

The IV amount needed for deficit therapyThe type of fluid used and the rate of infusion depends on the age and Na

status of the patient

In a child with body weight less than 10kg:• In Mild dehydration: 40 – 60 ml/kg..• In Moderate dehydration: 80 ml/kg..• In Severe dehydration: 120 ml/kg..

In a child with body weight more than 10kg:• In Mild dehydration: Maintenance x 0.4• In Moderate dehydration: Maintenance x 0.8• In Severe dehydration: Maintenance x 1.2

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) Calculate maintenance needs Calculate deficit needs Calculate 24 - hr electrolyte needs

Hypotonic and Isotonic Dehydration: Administer ½ calculated fluid during the 1 st 8 hrs. Administer remainder over the next 16 hrs.C. Phase 3: Stabilization Replace ongoing losses (eg: diarrhea) Measure every 4-6 hrs and replace with appropriate fluids

Practical example

5 kg child who is 8% dehydrated what is the amount of fluids to be used?

Replacement: total replacement: 80ml/kg– first hour: 20 cc/kg = 20 x 5 = 100 cc – Replace the rest: 30 cc/kg (Over 6-8 hours)– 30 cc/kg (Over 12 hours)

Hyponatremia

(Serum Sodium concentration below 130mEq/L)

Mild: 120 – 130 mEq/L

Moderate: 110 – 120 mEq/L

Severe: Below 110 mEq/L

Hyponatremia

Predisposing Factors:♦ Diabetes mellitus (hyperglycemia)♦ Cystic fibrosis♦ CNS disorders ( SIADH)♦ Gastroenteritis♦ Excessive water intake (formula dilution)♦ Diuretics (thiazides and furosemide)♦ Renal disease

Hyponatremic Dehydration♦ Hypovolemic Hyponatremic Dehydration

• High urine output and Na excretion• Increase in atrial natriuretic factor

♦ Euvolemic Hyponatremic Dehydration• ADH mediated water retention

♦ Hypervolemic Hyponatremic Dehydration• Edematous disorder (nephrotic syndrome, CHF, cirrhosis)• Water intoxication

Hyponatremia

♦ Early Onset (Serum Sodium 120 meq/L) <• Nausea • Vomiting • Headache

♦ Later or Severe (Serum Sodium 120 meq/L) <• Seizure • Coma • Respiratory arrest

Management of Hyponatremia

♦ Treatment of Asymptomatic hyponatremia can be made by increasing the Saline content in IVFs or by IV infusion of normal Saline.

♦ Symptomatic hyponatremia necessitates therapy with hypertonic Saline ( Sodium Chloride 3% solution)

Rise in serum Na should not exceed 2 mEq/L/h toprevent Central Pontine Myelinolysis.

In Severe symptomatic Hyponatremia

Give slow IV infusion of hypertonic saline solution (NaCl 3% solution) in a dose which raises the serum sodium level to 125 mEq/L.

As 1 ml/Kg of this solution will increase the serum sodium level by about 1 mEq/L.The required dose in ml/kg = (125 – actual serum sodium level)..

Two precautions are important:1.The maximum dose per time is 10ml/kg2.The rate of infusion should not exceed 60ml/hr

The dose should be given over 2 - 4 hours & Serum sodium level should be measured after each dose

Practical example

A child 10kg is presenting with seizers, dehydration, Serum Na level 115mEq/L?

treatment: (125 - 115)= 10ml/kg (100ml NaCl 3% solution over 2 hours)

Hypernatremia

(Serum Sodium concentration above 150mEq/L)

Mild: 150 - 160mEq/L

Moderate: 160 - 170mEq/L

Severe: Above 170mEq/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

HypernatremiaEtiology

♦ Pure water depletion • Diabetes insipidus (Central or Nephrogenic)

♦ Sodium excess• Salt poisoning (PO or IV)

♦ Water depletion exceeding Na depletion• 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)

Drop in serum Na should not exceed 10-12 mEq/L per day or 0.5mEq/L/hr < to prevent brain edema.

• Goal: Replace deficit of fluids and electrolytes and daily maintenance

• Amount: Deficits + daily maintenance Fluid: Give over 24-48 hours

• Administer fluid at a constant rate over the time for correction

• Typical fluids: D5 NS or D5 NS (with 20mEq/L KCl unless contraindicated)¼ ½

• Follow serum Na level: (Decrease Na concentration at a rate of 0.5 mEq/hr or 10 mEq/day)

If Sodium decreases too rapidly: (Increase [Na] content of IVF or decrease rate of IVF)

If Sodium decreased too slowly: (Decrease [Na] of IVF or increase rate of IVF)

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

HypokalemiaDiagnosis : Serum K 3mEq/L<♦ Symptoms

• Arrhythmias• Neuromuscular excitability (hyporreflexia, paralysis)• Gastrointestinal (decreased peristalsis or ileus)

♦ ECG:• Flat T waves• Short P-R interval and QRS• U waves

Causes of Hypokalemia

Nutritional GI Loss Renal Loss Endocr inePoor intake Diarrhea Renal tubular acidosis Insulin therapy IVF low in K Vomiting Chronic renal disease Glucose therapy Malabsorption Fanconi's syndrome DKA

Intestinal fistula Gentamicin, Hyperaldosteronism Laxatives Amphotericin Adrenal adenomas Enemas Diuretics Mineralocorticoids

Bartter's syndrome

Hypokalemia

Management:♦ Cardiac Arrhythmias or Muscle Weakness

• KCl IV 35mEq/Liter (cardiac monitor is essential)♦ PO K - Depend of etiology

• Hypophoshatemia = KPO4• Renal tubular acidosis = K citrate

HyperkalemiaDifferential 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

HyperkalemiaDiagnosis:

♦ 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 • IV NaHCO3 , glucose and insulin infusion

♦ Ion exchange resins• Sodium polystyrene sulfonate (Kayexelate)

– PO or Enema

♦ Haemodyalisis

Management of hyperkalemia

• Calcium gluconate 10%: 0.5ml/kg• Sodium bicarbonate 5%: 4ml/kg IV over 10

minutes• Glucose & Insulin infusion: Glucose 50%

(1ml/kg) with regular Insulin (1U for each 10ml glucose 50%)

• Peritoneal dialysis

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.

• Deficit fluid requirements are based on classification of dehydration.

• Hypotonic and isotonic dehydration are corrected in 8-hr and 16-hrs.

• Hypertonic dehydration is corrected based on Na level (usually over 48hrs).

• Slow correction of both hyponatremia and hypernatremia.

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]• Dr Mohamed El Najar , Pediatric Critical Care, Third edition: Chapter

11 PP. 287- 292