1. FLUIDS AND ELECTROLYTES

2. INTRODUCTION
The kidneys are responsible for maintaining plasma osmolality within a narrow range.
Water is the most important solvent in the composition of the living systems.
Total body water is a percentage of the body weight.
TBW decreases with age.
TBW consists of the ICF and ECF.

3. INTRODUCTION CTD At birth TBW is 78% of body wt
Drops dramatically within 1st month of life
Equals adult level of 55%-60% at 1yr
ECF drops after birth due to neonatal diuresis.
ICF increases to achieve adult ratio.
Obligatory water loss refers to the minimum intake necessary to maintain fluid balance.

4. TBW AND AGE Age Body water % ECF% ICF% Term 75 35-44 33 4-6mo 60 23 37
Puberty
Adult

5. ECF Constitutes 20-25% of body wt Consists of
plasma water which is 5% of body wt
interstitial water dat is 15% of body wt
Differs btw males and females at puberty
Monitored by low( cardiac atria) and high pressure (aortic arch, carotid sinus,JGA)
Regulated by the RAA,ANF,ADH.

6. ICF Represents the difference btw TBW and ECF Forms 30-40% of body wt
It is the sum of fluids in different locations of the body with different functions.

7. OTHERS
Trans-cellular and other slowly exchangable compartments are of lesser importance under normal conditions.
Forms 8-10% of body wt
Found in the bone, connective tissue and cartilage
It is not accessible to body fluid regulatory mechanism

8. OTHERS CTD
Trans-cellular fluid are located in the cerebrospinal, intra-occular, pleural, peritoneal and synovial fluids
Transcellular fluid is influenced by trans epithelial transport.
Also described as extracoporeal.

9. REGULATION OF BODY WATER
Body water balance is regulated by intake and excretion
Excretion is the most important in the regulatory mechanism
Plasma osmolality is mosmo/kg H20 is the concentration of solute particles and this is constant irrespective of fluctuation of solutes and water intake

10. INTAKE REGULATION Thirst is a major defense against fluid depletion.
Regulated by a center in the mid
hypothalamus
Change in plasma osmolality as littlle as 1-2% or ECF depletion by 10% stimulates thirst
Osmoreceptors located in the hypothalamus, pancreas and hepatic portal vein but the mechanism by which volume depletion induces thirst are not understood.

11. EXCRETION Losses of water occurs thru lungs ,skin, git, kidneys.
Insensible loss are those lost thru evaporation and is proportionate to the surface area of the body and influenced by enviromental temp, resp
Insensible loss must be taken into consideration in fluid management in children
Urinary water excretion is an obligatory one that is needed in body homeostasis
Obligatory loss is important in osmolality regulation.

12. EXCRETION CTD
Urinary loss is regulated by ADH and its receptors activity in the collecting duct and the medullary concentration gradient where there is passive re-absorption of water
ADH is an octapeptide released from the posterior pitutary fossa in response to stimuli from the hypothalamus.

13. FLUID THERAPY
Fluid therapy when employed orally or parenterally is to maintain or restore volume or composition of body fluids.
The goal of fluid therapy is to normalize the ICF and ECF chemical environment for cell and organ to function well.
Fluid requirement consists of three categories viz
i) maintenance
ii) deficit
iii) supplementary or ongoing loss

14. MAINTENANCE THERAPY
This is a function of metabolic rate changes of which affect h20 production.
It replaces usual body losses of fluid and electrolyte.
Includes usual insensible loss and the urinary output ml for ml
Calculation is based on 100ml/100 cal on the assumption of negligible fecal loss .
It is also assumed dat this will also address the renal water loss.

15. MAINTENANCE CTD Requirement is as follows
Body wt in kg Fluid requirement/day
ml/kg
ml/kg+50ml/kg
Above ml/kg+50ml/kg+
20ml/kg
*** any wt above 20kg subsequently needs 20ml/kg in addition.

16. EXAMPLE
What is the maintenance fluid requirement of a 2year old with a weight of 20kg
1st 10kg =100*10……1000ml
+2nd 10kg = 50*10……..500ml
Total fluid = ml

17. EXAMPLE CTD
Calculate the fluid requirement of a child with a weight of 30kg
1st 10kg=100*10=1000ml
2nd 10kg= 50*10= 500ml
3rd 10kg= 20*10= 200ml
Total = 1700ml

18. DEFICIT THERAPY
This includes losses due to disease e.g vomiting ,diarrhea
Calculation is based on body weight loss
This loss is based on clinical assessment.

19. DEGREE OF LOSS Mild dehydration loss of 3% - 5% of body weight
loss of 30ml/kg - 50ml/kg of body weight
Moderate dehydration
loss of 7%-10% of body weight
loss of 70ml/kg – 100ml/kg of body weight

20. DEGREE OF LOSS Severe dehydration loss of 10%-15% of body weight
loss of 100ml/kg-150ml/kg of body weight

21. CLINICAL FEATURES OF FLUID DEFICIT
MILD DEHYDRATION
Loss of 3-5% body weight
There is mild thirst
Dry mucus membrane
No sunken eyes
Skin tugor returns normally
BP, HR normal
Mental status intact
Urine output normal

22. MODERATE DEHYDRATION Loss of 7-10% of body weight Thirst is marked
Absence of tears
Dry mucus membrane
Sunken eyes and fontanelle
Skin tugor goes back slowly
Reduced urine output
HR ↑,BP↓
Irritable mental state

23. SEVERE DEHYDRATION Loss of 10-15% of body weight Severe thirst
Parched mucus membrane
Very sunken fontanelle
Anuria
Hypotension
Delayed capillary refill
Lethargy or coma

24. MANAGEMENT OF DEHYDRATION
Mild and moderate dehydration can be corrected orally.
Severe dehydration however needs parenteral therapy cos the patient will be to weak to take enough orally and may even be in shock so iv or intra-osseous transfusion or even intraperitoneal
Parenteral is also needed to prevent renal failure.

25. SEVERE DEHYDRATION Therapy is in stages A --- Initial therapy
B----Subsequent therapy
C----Final

26. MX OF SEVERE DEHYDRATION CTD
The goal of the initial therapy is to expand the ECF rapidly
The patient needs 100ml/kg
20ml -30ml/kg of IVF is given rapidly this may be repeated if need be this is given over 30minutes or 1Hr or even longer in malnourished children

27. The goal of the second or subsequent stage is to complete the existing deficit
Require 70-80ml /kg and this is given over 5hr
The on going loss in the case of diarrhea is commenced after completing the lost fluid.

28. When the patient is able to take again then you commence the maintenance therapy.

29. ELECTROLYTES
Osmolality of the body is accounted for by the electrolytes in the body.
The electrolytes are Na, K, Cl, Hco3, urea,glucose.
Na is the main electrolyte in the ECF alongside the Cl,Hco3, glucose urea as the anions
K is the main electrolyte in the ICF.

30. ELECTROLYTES CTD Tonicity efers to the effective osmolality
Also reflects the concentration of impermeable solutes in fluid.( Na, glucose)
Normal tonicity is mmol/kg
Tonicity is important in diseases where there is inter-compartmental fluid shift
Neurologic problems are often associated with the fluid shift.
Urea and ethanol affect osmolality while mannitol and glycerol affects both osmolality and tonicity.

31. MAINTENANCE REQUIREMENTS OF ELECTROLYTES
ELECTROLYTES REQUIREMENT
Na mmol/kg/day
K mmol/kg/day
Cl mmol/kg/day
Hco3
*** New borns do not require Na,K,Cl in the 1st 24hrs

32. SODIUM Sodium is the major cation in the ECF
Responsible for maintaining intravascular and interstitial volumes
11% is in the plasma pool,29% in the interstitial lymph fluid 2.55 in the icf
43% of total sodium is in the bone and only 1/3 of this is exchangeable
ICF Na is maintained at 10meq/l while ECF is140meq/l
Function includes nerve conduction,cellular nutrition and BP maintenance

33. SODIUM REGULATION
The amt of Na in the body is dependent on the intake and excretion.
Regulation of Na intake is poorly understood
Different sources of intake which depends on the source as well as age
Absorption occurs throughout the git minimally in the stomach and maximally in the jejunum
Absorption is aided by Na-k ATPase.

34. Na REGULATION CTD Excretion of Na occurs thru sweat, urine, feces
Kidney is the principal organ regulatig Na excretion.
The above is dependent on the glomerular filtration and the tubular reaborption.
67% of tub eab takes place in the PT and LOH ,20% in the asc limb of LOH, 7% in the DT,6% in the CD
Regulation occurs mainly thru the RAA

35. HYPONATREMIA Refers to serum conc <130meq/l
Can occur when the intake of of fluid exceeds the excretory capacity of the kidney.
Causes are as follows
decreased ADH
reduced gfr,polydipsia, malnutrition, thiazide.

36. Increased ADH
hypovolemia---- mineralocorticoid def, excess diuretic,dehydration,cappilary leak syndrome
glucocorticoid def, hypothyroidism,
NS, CCF, hepatic cirrhosis
SIADH

37. CF N MX OF HYPONATREMIA Can be either symptomatic or asymptomatic
Often times occurs along with dehydration when it is referred to as hypotonic dehydration
Includes nausea, vomiting,muscle twitching
Na replacement using the formular
wt* deficit *0.6
Correction done over 24hrs ½ in the 1st 8hrs and the other ½ next 16hrs.

38. HYPERNATREMIA Serum Na >150meq/l
Results when there is excessive gain of Na usually iatrogenic in improper mixing of infant formula
Excessive loss of body water in diarrhea, fever
Causes include
low ADH activity as seen in central DI, nephrogenic DI
high ADH activity as seen in excessive intake, excessive loss thru sweat,adipsia

39. CF N MX OF HYPERNATREMIA
**HYPERNATREMIA IS AN EMERGENCY
Lethargy ,confusion, seizures, ICH, irritability, hypertonia, hyperreflexia,coma
ECF is preserved due to shift of water from ICF.
***DO NOT CORRECT RAPIDLY AS RAPID INTERCOMPARTMENTAL SHIFT IS DANGEROUS
Rate of Na lowering is at 12meq/l/day
Correction of fluid deficit is done over hrs.
Choice of IVF is ½ normal saline

40. POTASSIUM Potassium is the major intracellular cation
Essential for cardiac and skeletal muscle
contraction
Balance is dependent on intake, renal and git excretion
ECF value of Kis meq/l
Difference in K btw the two compartments is maintained by Na-K ATPase

41. K REGULATION Regulate by two main processes
1) mechanism which responds to within minutes to plasma changes thus promoting import or export from the icf this include insulin,βadrenergic agonist, acidosis, alkalosis, aldosterone and hyper-osmolality. This they do by inducing a secondary messenger which alters Na-K ATPase
2) mechanism responding within hrs to regulate excretion from the body.