Electrolytes and pH disturbancies: clinical signs to make a correct diagnosis and an early treatment Alberto Bettinelli Departments of Pediatrics Leopoldo Mandic Hospital, Merate (LC) Italy

Case 1 An Albanese child…

Clinical presentation Male. 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 , lenght cm. 75 (< 3° percentile) Blood pressure 68/34 mmHg

Emergency measures - adequate periferal perfusion with administration of isotonic saline (20 ml/kg/h) - delivery of 02

First biochemical examinations venous pH plasma bicarbonates, 5.0 mmol/l pC mmHg

QUESTIONS ? 1)Is it a simple metabolic acidosis? 2)Is it a metabolic acidosis with normal plasmatic anion gap?

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: ) 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; pC mmHg bicarbonates: 25-5 = 20 pC02: 20 x 1.3 = = 14.0 = expected pC02 The respiratory compensation is appropriate = simple metabolic acidosis

After some hours Venous ph 7.150; plasma bicarbonate 8.7 mmol/l, pC 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 di bicarbonates)

Metabolic acidosis with normal anion gap - Losses of bicarbonate HCO3- - 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) - Failure to replenish HCO3- stores depleted by the daily production of fixed acids - 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, eplerenone, amiloride, triamterene) - Exogenous infusions - 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 = = + 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 Renal ecography demonstrated nephrocalcinosis Urinary pH; not very simple to detect with the usual methodology Our urinary pH (with a plasma venous pH between and 7.150): Diagnosis of DISTAL RENAL TUBULAR ACIDOSIS (DRTA, type 2)

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 Glucose 5% = 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; pC mmHg

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 2008; 23: ) - Laboratory investigations revealed proximal tubular dysfunction that disappeared some months after the beginning of the treatment

Case 2 The child was in apparent good health up to the age of 9 months when he was admitted to the Hospital for gastroenteritis In the urgency plasma Potassium was 1.7 mmol/l He presented a cardiac arrest followed by immediate reanimation. After this episode he did not present any cardiac or neurologic complications When he left the Hospital, the child was in good clinical conditions and his plasma K was between mmol/l

Interpretation The severe hypokalemia was considered the cause of cardiac arrest (probably associated with cardiac arrhythmias) Rotavirus was identified as the pathogenetic factor of the severe gastroenteritis

At 10 years of age He was admitted to the Hospital for a suspicious of appendicitis. His plasma potassium was 2.3 mmol/l After surgery his plasma potassium levels persisted at low levels (2.5 e 3.0 mmol/l ) In this case the origin of hypokalemia was investigated New hypothesis?? It appeared as a chronic condition of hypokalemia

How is blood pressure? His blood pressure was always normal: 90/60 mmHg = in the reference range We can exclude hypokalemia associated with high blood pressure (often linked with metabolic alkalosis; total K+ body content normal) - renin: primary aldosteronism (either hyperplasia or adenoma), apparent mineralocorticoid excess (= defect in 11- -hydroxysteroid-dehydrogenase), Liddle syndrome (congenitally increased function of the collecting tubule sodium channels), dexamethasone-responsive aldosteronism (synthesis of aldosterone promoted not only by renin but also by adrenocorticotropin), congenital adrenal hyperplasia (11- -hydroxylase or 17- -hydroxylase deficiency), Cushing disease, exogenous mineralocorticoids, licorice- ingestion (= 11- -hydroxysteroid-dehydrogenase blockade) - or renin: renal artery stenosis, malignant hypertension, renin producing tumor

Hypokalemia associated with normal-low blood pressure True potassium depletion (= total K+ body content reduced) Extrarenal conditions - Prolonged poor potassium intake, protein-energy malnutrition - Gastrointestinal conditions: gastric (associated with alkalosis), vomiting, nasogastric suction; small bowel ; associated with acidosis: biliary drainage, intestinal fistula, malabsorption, diarrhea, congenital chloride diarrhea - Acid-base balance unpredictable: bowel cleansing agents, laxatives, clay ingestion, potassium binding resin ingestion - Sweating, full thickness burns Renal conditions - Interstitial nephritis, post-obstructive diuresis, recovery from acute renal failure - With metabolic acidosis: renal tubular acidosis (type I or II), carbonic anhydrase inhibitors (e.g.: acetazolamide), amphotericin B, outdated tetracyclines - With metabolic alkalosis: - Inherited conditions: Bartter syndromes, Gitelman syndrome, and related syndromes - Acquired conditions: normotensive primary aldosteronism, loop and thiazide diuretics, high dose antibiotics (penicillin, naficillin, ampicillin, carbenicillin)

Main investigations The child was in good clinical conditions; his growth was between the 30-50° percentile Main biochemical data: - plasma K, mmol/l ; FeK 39-45% - plasma bicarbonates mmol/l - plasma Na, mmol/l; FeNa % - plasma Cl, mmol/l; FeCl plasma Mg mmol/l ; FeMg % - urinary calcium/creatinine mg/mg - plasma renin activity, ng/ml /h (ref. < 5) - plasma aldosterone, pg/ml (ref )

Main probable diagnosis GITELMAN SYNDROME: - hypokalemia with increased FeK and increased FeCl - metabolic alkalosis - hypomagnesemia - hypocalciuria - hyper-reninemia associated with normal blood pressure - usually diagnosis during schoolife and young adults - some patients with growth failure

Differential diagnosis BARTTER SYNDROME TYPE III: - hypokalemia with increased FeK and increased FeCl - metabolic alkalosis - NORMO-MAGNESIEMIA (sometimes hypomagnesemia, 39% of cases*) - VARIABLE CALCIURIA (sometimes hypocalciuria 8% of cases*) - hyper-reninemia associated with normal blood pressure - usually diagnosis during early childhood - half of the patients with growth failure *Konrad M et al; J Am Soc Nephrol 2000; 11:

Thiazide test (Colussi G, Bettinelli A, 2007) A wash out period of at least 7 days was allowed between withdrawal of any therapy and thiazide test; however, oral KCl and Mg salts, if already in use, were maintained and stopped the day before the test Thiazide test: after un overnight fast, the patients were invited to drink tap water (10 ml/kg b.w.) to facilitate spontaneous voiding

Plasma Na, K, Cl and creatinine Hydrochlorothiazide (HCT) 1 mg/kg b.w. Mean of the two urinary values Maximum urinary value obtained after HCT

FE Cl maximal excretion of FE Cl at any time after HTC administration minus the mean of the two basal FE Cl FE Cl : 0.60%

Control Subjects Bartter Syndrome Gitelman Syndrome AdultsChildren Fractional Chloride Excretion, %

Molecular evaluation The child presented two heterozigous mutations on the gene SLC12 A3 Therapy consisted of oral KCl supplementation QTc was 0.44 No other cardiac complication was reported

Mutations in the SLC12A3 gene found in the Italian population NH 2 R COOH Mutations demonstrated in patients subjected to HCT test

Severe syncope and sudden death in children with inborn salt-losing hypokalaemic tuulopathies. Cortesi C, Bettinelli A, Bianchetti M.; Nephrol Dial Transplant 2005; 20: children were evaluated with inborn salt- losing hypokalaemic tubulopathies - 19 European paediatric kidney disease specialists - Four patients died suddendly and 3 had severe syncope - These episodes occurred in the context of severe chronic hypokalemia (< 2.5 mmol/l) or were precipitated by acute diseases, which exacerbated hypokalemia (< 2.0 mmol/l)

Chronic treatment - KCl supplementation - Antialdosteronic drugs (Spironolactone, amiloride)

Final message In patients with inborn salt-losing tubulopathies, diarrhoea or vomiting may cause severe, hazardous hypokalemia (< 2.0 mmol/l) A prompt electrolyte and fluid repair is of paramount importance