Fluid And Electrolyte Balance And Fluid Therapy: Xiaoli Zhang The Third Affiliated Hospital Of Zhengzhou University

Fluid and Electrolyte Balance and Fluid Therapy

Xiaoli Zhang The third affiliated hospital of zhengzhou university

Characteristics of Fluid and Electrolyte Balance

in Children

Body fluid volume and distribution 

  

The percentage of fluid in the body varies with age. The younger children have more body fluid than older children. The plasma portion of ECF remains relatively constant. The major difference is in interstitial fluid . Body fluid distribution for infants and children at various age is listed in table.

Total body water & its distribution Body water compartments related to age (total body mass%)

Age Newborn infant 1 year 2 ～ 14 years Adult

TBW

ECF

ICF

Plasma

ISF

80

5

40

35

70 65

5 5

25 20

40 40

55 ～ 60

5

TBW: total body water ICF: intracellular fluid

10 ～ 15 40 ～ 45 ECF: extracellular fluid ISF: interstitial fluid

Regulation of fluids and electrolytes 

Despite wide variations in the dietary intake ,volume and composition of body fluids are maintained in an extremely narrow range as excretion is adjusted to match intake.



1 skin and lung regulation 2 gastrointestinal regulation 3 renal regulation

 

(Ⅰ) dehydration 

It is defined as decrease of gross body fluid or extracellular fluid especially.



Dehydration contains losses of sodium, potassium and other electrolyte in addition to water loss.

A.

Degree of dehydration

Dehydration

Mild

Moderate

Severe

weigh loss(%)

3~5 ％

5 ～ 10 ％

>10 ％

General appearance

Alert, restless

Lethargic, irritable

comatose

Anterior fontanelles

Flat

Slight sunken

Sunken

Skin elasticity

Decreased

Moderately decreased

Markedly decrease

Tears

Present

reduced

Absent

Thirst

Slight

Moderate

Severe

Mucous membranes

Dry

Very dry

Severely dry

Urine output

Decresed

oliguria

severe oliguria

Blood pressure

Normal

Normal or lowered

Lowered

pulse

Normal or increased

increased

Rapid, thready

Estimated fluid deficit(ml/kg)

30~50

50-100

100-120

B. Type of dehydration  Isotonic

dehydration  hypotonic dehydration  hypertonic dehydration

①Isotonic dehydration 

electrolyte and water are lost in the same proportion



serum sodium concentration remains ① normal, between 130 to 150mmol/l



the major loss is from the ECF



clinical manifestations include sunken eyes, lack of tears, dry mucosa, loss of elasticity and decreased urine output

②hypotonic dehydration 

The electrolyte deficit exceeds the water deficit.



Plasma sodium concentration is less than 130mmol/l.



Water transfers from the ECF to the ICF to establish osmotic equilibrium.



This movement further increases the ECF volume loss . Easily shock

③hypertonic dehydration 

Water loss in excess of electrolyte loss.



Plasma sodium concentration is greater than 150mmol/l.



Fluid shifts from the ICF to the ECF.



Shock is less apparent. However, neurologic disturbances ,such as seizures, are more likely to occur



because rapid dehydration may cause significant fluid shift and brain cells to dehydrate.

Type of dehydration Type of dehydration Isotonic

Hypotonic

Pathogeny

Serum sodium

Pathophysiology & clinical characteristic

Acute 130 ～ 150 ECF: decrease, gastrointe- mmol / L (intracellular = extracellular) Dehydrant volume accord with stinal fluid dehydrant physical sign lose Chronic <130 gastrointe- mmol / L stinal fluid lose

ECF: severely decrease, Easily shock ， Severer dehydrant sign than the other two kinds

Hypertonic High grade >150 fever, mmol / L Infection

ICF: severely decrease, Milder dehydrant sign than the other two kinds

(Ⅱ) Hypokalemia (<3.5mmol/l) Pathogeny

1. Lack of intake

( poor food intake over an extended period or administration of IV fluids without added K )

2. Excessive loss from kidneys or gastrointestinal tract ( vomiting,diarrhea 3. A shift from extracellular to the intracellular spaces ( occurs with

)

alkalosis,insulin administration and periodic paralysis)

Clinical manifestation 

Nervous and Muscles——drowsiness , musle weakness, hyporeflexia, abdominal distention



Heart—— heart rate increasing, arrhythmia, heart sound lowering ECG(electrocardiograph) : amplitude or inversion of T wave, ST segment depression, prolonged QT interval, and increased height of U wave

Therapeutic managment  Determine and treat cause  Supply potassium  Renew normal diet as soon as possible

noticed  Daily dosage of supplemental potassium is 3~4mmol/kg(200~300mg/kg)  Concentration less than 0.3% by IV  Transfusion duration more than 8 hours daily  Avoiding IV push  Supplement lasting 4 to 6 days  Normal renal function (Supply kalium after urination 6 hours of preadmission)

Disturbances of acid-base banlance 

The pH value is determined by taking the negative logarithm of the H+ concentration.



PH concentration is maintained between 7.35-7.45 by the kidneys, the lungs, a variety of chemical buffers, and some metabolic processes.



[HCO3-] : [H2CO3] = 20:1



Acid- base disturbances fall into four major categories:

metabolic acidosis / alkalosis respiratory acidosis / alkalosis

(Ⅲ)

Metabolic acidosis Pathogeny

1. The lose of large amount of basic substances （ gastrointestinal tract, kidneys ） 2. Increased Acid production (including hungriness, diabetes, renal failure, hypoxia ） 3. Too much acid substance intake （ such as salicylate poisoning ）

The most common cause of metabolic acidosis in children is diarrhea.

Degree Mild acidosis

HCO3-

13~18

mmol / L

Moderate acidosis HCO3-

9~13

mmol / L

Severe acidosis

<9

mmol / L

HCO3-

Clinical manifestation 

Deep and rapid respirations



Decrease peripheral vascular resistance and cardiac ventricular function, resulting in tachycardia, arrhythmias, hypotension, and tissue hypoxia



Cherryred lips, anorexia, nausea, muscle weakness, listlessness and even lethargy and coma

Therapeutic management Correcting the primary cause ---- mild acidosis Replacing the excessive losses of HCO3with sodium or potassium bicarbonate ----moderate and severe acidosis 5%NaHCO3(mmol)=(22- HCO3- mmol/l) Х 0.5 Х Weight (Kg) 5%NaHCO3(ml)=(22- HCO3- mmol/l) Х 0.5 Х Weight (Kg) / 0.6 =(-BE) Х 0.5 Х Weight (Kg) # half amount

Common Solution of Liquid Therapy A. Nonelectrolytical solution

5 ％ glucose 10 ％ glucose

B. Electrolytical solution 0.9 ％ NaCl

103 ％ 1.4 ％ NaHCO

3 ％ 、 10%NaCl

5 ％ NaHCO3

C. Mixed solutions

refer to the following table

KCl

Common mixed solution

5/10% G.S

0.9% NaCl

1.4% osmolality NaHCO3

2:1

－

2

1

isotonic

3:2:1

3

2

1

1/2

3:4:2

3

4

2

2/3

6:2:1

6

2

1

1/3

The therapy has three categories • Deficit replacement • Supplemental replacement of ongoing losses • Maintenance

A Deficit replacement There are three essential components of administering the therapy: volume, Component and rapidity.

1)Volume in principle ,the fluid supplements: Mild dehydration 50ml/kg Moderate dehydration 50~100ml/kg Severe dehydration 100~120ml/kg

2)Component: determined by the types of dehydration

Hypotonic

Hyperosmolar solution

Isotonic

isotosmolar solution

Hypertonic

hyposmolar solution

3)rapidity 

In the first 8-12 hours of thansfusion



Severe dehydration : to restore circulatory status 20ml/kg of isotonic sodium solution (<300ml totally) 30~60minutes

B Supplemental replacement of ongoing losses 

estimate



1/3~1/2 isotonic sodium solution

Given equably within 24 hours  (In the other 12~16 hours) 

C Maintenance (physiological need) 

About 60~80ml/kg daily



1/5~1/4 isotonic sodium solution



Given equably within 24 hours

In summary    

   

Total volume Mild 90~120 ml/kg Moderate 120~150 ml/kg Severe 150~180 ml/kg Components Hypotonic hypertonic (2/3 isotonic) Isotoic isotonic (1/2 isotonic) Hypertonic hypotonic (1/3 isotonic)

ORs(oral rehydration salts) (The world health organization recommended)



Composition: 

sodium chloride 3.5g



Bicarbonate sodium 2.5g



Potassium chloride 1.5g



glucose 20.0g



And water 1000ml to dissolve



2/3 isotonic



The concentration of potassium is 0.15%

HAPPY PIG YEAR