12. Page 12
A 2 year old has a 4-day history of gastroenteritis, poor
fluid intake and infrequent urination.
On exam you find dryness of the mucous membranes,
sunken eyes with mild tenting of the skin.
The serum sodium is 137 mEq/L.
The weight is 10 kg.
You determine the child is suffering from about ????%
dehydration.
What are the fluid and electrolyte requirements?
Case 2
27. Page 27
Isonatremic Dehydration
Na+
= 135-145 mEq/L
Fluid deficit ?
Which parts of deficit come from ICF v. ECF ?
ECF Na+
loss = ECF Fluid deficit (L) X 145
ICF K+ loss = ICF Fluid deficit (L) X 150
28. Page 28
ECF and ICF Percentage of Loss
% fluid of deficit % fluid of deficit
Duration of illness from ECF from ICF
<3 days 80 20
>3days 60 40
29. Page 29
H2O Na K Cl
(ml) (mEq) (mEq) (mEq)
Maintenance
Total deficit = 1000 ml
Extracellular fluid deficit
(60% of total)
Intracellular fluid deficit
(40% of total)
Total
1000 30 20 40
600 87 - 60
400 - 60 -
2000 117 80 100
Isonatremic Dehydration
30. Page 30
Phase Approach
PHASE 1
– Emergency restoration of circulation if patient is hypovolemic
– 10-20 ml/kg of isotonic fluids only 40ml/kg
– No response 10ml/kg albumin/plasma/blood
PHASE 2
– Replacement of ½ of the fluid loss (deficit and maintenance) in
first 8 hours
– Replacement of ongoing loss
PHASE 3
– Replacement of remaining ½ of the fluid loss (maintenance
and remaining deficit) in next 16 hours
– Replacement of potassium after voids
32. Page 32
You see a 3 year old who has had diarrhea and been
vomiting for 3 days. She has been drinking tap water
most of this time.
Examination shows sunken eyes and marked tenting of
the skin but the child is not in shock.
The serum Na+
is 120 mEq/L.
The weight 14 kg.
You estimate the deficit as 7%.
What are the fluid and electrolyte requirements for this
patient?
Case 3
39. Page 39
You see a 6 month old suffering for 4 days from
severe diarrhea.
The mucous membranes are dry, skin feels doughy
and the child is somnolent and lethargic.
The serum Na+
is 165 mEq/L.
The child weighs 5 kg and you assume the fluid
deficit is at least 10%.
What are the fluid and electrolyte requirements?
Case 4
44. Page 44
case 5
• A 7 year old boy presented with at least a weeks
history of abdominal pain and vomiting and
polyuria . He was mildly confused. BP= Nr., wt=25
kg
– PH=7.52 Na=137
– PCO2=44.6 K= 2.2
– HCO3= 38 Cl=91
– How do you approach to this patient?
– How do you treat ?
– What is the cause of hypokalemia?
47. Page 47
Treatment
– Oral
• Safest, although solutions may cause diarrhea
– IV
• Peripheral: do not exceed 40-50 mEq/L potassium - Avoid
temptation to rapidly bolus
• Central: 0.5 -1 mEq/kg over 1-3 hours, depending on
severity
– Replace magnesium also if low
• (25-50 mg/kg MgSO4)
49. Page 49
Case 6
– 8 month old infant with ARPKD presents with
irritability. She is on nightly peritoneal dialysis
at home.
– The lab calls a panic potassium value of 7.1
meq/L.
– The tech says it is not hemolyzed.
What do you do now?
51. Page 51
TTKG
• The transtubular potassium gradient in the cortical
collecting duct is an index reflecting conservation of
potassium.
• A normal TTKG on normal diets is 8-9. in normal
subjects
• With a potassium load the TTKG may rise to 11.
• In the face of Hyperkalemia, a low TTKG (<7) may
indicate hypoaldosteronism.
• Without other disease, hypokalemia should produce
a TTKG <3 (some authors say TTKG <2.) The
expected TTKG in hyperkalemia is >10.
•
54. Page 54
The goals of therapy, in chronologic order
1. Antagonize the effect of K on excitable cell
membranes.
2. Redistribute extracellular K into cells.
3. Enhance elimination of K from the body.
