Transcript electrolytes and PH - Pan-Arab Pediatric Nephrology Association

Electrolytes and pH
disturbances: Case report
Chebl Mourani
Pediatric Nephrogist Ass Professor
President of PAPNA
Head of Ped hemodialysis Unit HDF
Update in Pediatric Nephrology
7 May 2009
Maximum Urinary
concentrating capacity
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400 mosm/Kg H2O in the preterm baby
600 – 800 mosm/Kg H2O in the newborn
> 1200 mosm/Kg H2O in child > 1 year
DDAVP test nl >/= 807mosm/Kg H2O
Serum anion gap Na+ - (Cl- + HCO3-)
= 12 meq/l differentiates bicarbonate loss
from net acid gain.
In the presence of acidosis, anion gap >
normal is considered to be net
acid gained.
If the anion gap is nl, bicarbonate loss
by GI tract or kidneys.
NH4 measuring
Urinary anion gap
Na+ + K+ < Cl- = nl
Na + K- > Cl- ~ impaired
NH4+ excretion
impaired distal
acidification
Case 1
Metabolic Acidosis
Clinical presentation
• female. Age: 2 years and 3 months
• Poor clinical condition with signs of dehydration
and chronic malnutrition (hypotrophia of muscles
with abdominal protrusion, hypotonia,
psychomotor retardation)
• Polypnea, 60/min
• Weight Kg. 7.610, length cm. 75 (< 3° percentile)
• Blood pressure 68/34 mmHg
Emergency measures
• - adequate peripheral perfusion with
administration of isotonic saline (20
ml/kg/h)
• - delivery of 02
First biochemical
examinations
• venous pH: 7.101
• plasma bicarbonates: 5.0
mmol/l
• pC02 :16.2 mmHg
QUESTIONS ?
1) Is it a metabolic acidosis with
normal plasmatic anion gap?
2) Is it a simple metabolic
acidosis?
After some hours
• Venous ph 7.150; plasma bicarbonate 8.7
mmol/l, pC02 26.9 mmHg
• Plasma Na 135, K 4.3, Cl 116 mmol/l
• Plasma anion gap:
• (Nap + Kp) – (Clp + Bicarbonate) = 14.6
• (Ref values 8-18; If you do not include K = 4-14)
• Plasma anion gap is normal: the major cause
of metabolic acidosis with normal anion gap was
excluded (gastrointestinal loss of bicarbonates)
Is it a simple metabolic
acidosis?
• Predicted metabolic and respiratory compensations
to simple primary acid-base disturbances
• (Bianchetti MG and Bettinelli A in Comprehensive
Pediatric Nephrology, Geary DF and Schaefer F Ed;
Mosby Elsevier 2008:395-432)
• Metabolic Acidosis: Primary Change  HCO3• Compensatory response:  pCO2 by 1.3∆ mm Hg 
for  1.0 mmol/L* in HCO3• ∆ range approximately ± 3 mm Hg; * from 25 mmol/L;
range approximately ± 2.0 mmol/L;  from 40 mm Hg.
First biochemical examinations
• Venous ph 7.101; plasma bicarbonates
5.0 mmol/l; pC02 16.2 mmHg
• ∆bicarbonates: 25-5 = 20
• ∆pC02: 20 x 1.3 = 26.0
• 40-26.0 = 14.0 = expected pC02
• The respiratory compensation is
appropriate = simple metabolic acidosis
Metabolic acidosis with normal anion gap
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- Losses of bicarbonate HCO3-
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- intestinal: diarrhea, surgical drainage of the intestinal tract, gastrointestinal fistulas
resulting in losses of fluid rich in HCO3-, patients whose ureters have been attached
to the intestinal tract
- urinary: carbonic anhydrase inhibitors (e.g.: acetazolamide), proximal renal tubular
acidosis (= type 2)
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•
- Failure to replenish HCO3- stores depleted by the daily production of
fixed acids
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- distal renal tubular acidosis (either classic, also called type 1 or type 4)
- diminished mineralocorticoid (or glucocorticoid) activity (adrenal insufficiency,
selective hypoaldosteronism, aldosterone resistance)
- administration of potassium sparing diuretics (spironolactone , amiloride,
triamterene)
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- Exogenous infusions
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- Amino acids like L-arginine and L-lysine (during parenteral nutrition)
- HCl or NH4Cl
- Rapid administration of normal saline (= NaCl 9 g/L) solution (= “dilutional”
metabolic acidosis)
•
Other questions
3) How is the urinary ammonium (urinary
anion gap)?
4) Can you perform some simple
investigations?
Response: question 3
3) How is the urinary ammonium
(urinary anion gap) ?
• Urinary anion gap: in non renal metabolic
acidosis urinary Cl>Na+K; this is because
urinary ammonium accompanies Cl
• In this case: Cl 23; Na 20; K 11.4 mmol/l
• Na + K – Cl = 31.4 -23 = + 8.4; a positive net
charge indicates an impaired ammonium
secretion and, therefore, impaired distal
acidification of renal tubule
Response to question 4)
4) Can you perform some simple
investigations?
Other investigations
• Urinary pH; not very simple to detect with
the usual methodology
• Our urinary pH (with a plasma venous pH
between 7.101 and 7.150): 7.248-7.456
• Diagnosis of DISTAL RENAL TUBULAR
ACIDOSIS (DRTA, type 1)
• Renal echography demonstrated
nephrocalcinosis
Administration of bicarbonate?
• - Possible benefits: metabolic advantage of faster
glycolysis with better availability of adenosine
triphosphate in vital organs, and improved cardiac action
• - Risks: extracellular fluid volume expansion, tendency
towards hypernatremia and devolepement of
hypokalemia and hypocalcemia
• - In this case a correction was started slowly:
• Body weight x 0.5 (desired bicarbonate - current
bicarbonate): 7.6 x 0.5 (9-5) = 15.2 mmol in some
hours in normal saline
Treatment
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Glucose 5% = 1.800 ml/mq/day
NaCl = 60 mEq/mq/day
KCl = 40 mEq/day
NaHC03- = 20 mEq/day
• - Than orally: NaHC03-, 1 gr/kg/day + potassium
citrate 1 mEq/kg/die
• After 7 days: venous pH 7.310; plasma
bicarbonates 21.3 mmol/l; pC02 43.6 mmHg
The inherited renal tubular acidosis (1)
The inherited renal tubular acidosis (2)
Audiometry evaluation
• The first investigation (the test tones were
warble tones) was in the normal range.
• Further audiometry evaluations are
required
Molecular diagnosis
• the molecular diagnosis was of distal renal tubular
acidosis due to an homozygous mutation in the
ATP6V1B1 gene ( homozygous L81P mutation)
• This mutation is known to be associated with
neurosensorial deafness
(Tasic V et al: Atypical presentation of DRTA in two
siblings. Pediatr Nephrol 2006; 23:1177-81)
- Laboratory investigations revealed proximal tubular
dysfunction that disappeared some months after the
beginning of the treatment
Case 2
Metabolic Alcalosis
Case 2
• One month old boy admitted because of failure to
thrive, vomiting, weight loss in the last 2 weeks.
• Uncomplicated gestation BW: 3300 g
• Family history: his brother died 3 years ago at the
age of 6 month. He suffered from postnatal hypoxia,
followed by ’’salt loosing kidney” and electrolyte
inbalance
• Physical exam: severly dehydrated
– Fontanelle, tongue
– Alert, reacts to painful stimuly
Laboratory data
• pH: 7.59, pCO2: 34
• The dehydrated child
has metabolic
NaHCO3: 36.7 mmol/l
alkalosis with
BE: +12.9 mmol/l
• Na: 102, K: 2.1, Cl: 74
– hyponatranemia,
mmol/l,
– Hypochloremia
• Ca: 2.67, P: 1.2 mmol/l
– hypokalemia
• Crea:48 micromol/l
TP:55 alb:38g/l urine
osmolarity:243
mosmol/l
Differential diagnosis
• 1. Pylorus stenosis
– Usually less severe; physical and US examination
• 2. Salt loosing kidney (ex: tubular dysfunction due to
hydronephrosis, ATN, metabolic disease).
– Alkalosis?
• 3. Salt loosing form of adrenogenital syndrome
– But: Functional mineralocorticoid deficiency causes
hyperkalemia
• 4. Hyponatremic, hypokalemic, hypochloremic
alkalosis:
– Bartter syndromes
Pathophysiology of Bartter syndrome
Decreased Na+Cl reabsorption at the ascending part of the
loop of Henle
Na-reabsorption and - increased K and H secretion
at the distal tubule
Hypo-K, (hypo-Cl, alkalosis)
renal PG E2
vascular PGI2
plasma bradykinine
renin
angiotensin II
pressor activity.
depressor activity
normal blood pressure
pressor activity
aldosterone
kallikrein
JGA hypertrophy
noradrenalin
Ion transport at the loop of Henle
Treatment
•
NaCl (10-15 mmol/kg/day)
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KCl (10mmol/kg/day)
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Indomethacin (2 mg/kg/day)
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Spironolacton (5 mg/kg/day)
• His somatic and mental development is
normal
• Repeated need of hospitalization due to
acute metabolic derailements following
gastrointestinal and respiratory tract
infections. Transient need of parenteral
supplementation
Classification of the different subtypes of Bartter’s and Gitelman’s
syndromes, with the responsible genes, the resulting transport proteins,
their localization and function
Clinical presentation and biochemical alterations in Bartter’s and
Gitelman’s syndromes
Specific
transport
defects in some
renal tubular
disorders