Two Little Water Cravers

Transcription

1 Two Little Water Cravers

2 Baby Mo (5mths/M) Chief complaint Repeated vomiting since 2 months old with poor weight gain PMH Gestation 40+6wks, BW 3.375kg Hx of fracture Rt clavicle at birth HbH disease on folic supplement Vaccine up to date NKDA No developmental concern

3 HPI Repeated vomiting since birth ~2-3x/day Moderate amount of undigested milk soon after feeding Non projectile, no bile stained On AF 5oz/feed, 5x/day Irritable, crying for milk Large amount of urine output ~ 7-8x/day BO 1x/day, YSS Failure to thrive BW 50% at 1mth BW 25% at 2mths BW 0.6kg below 3% at 5mths

4 HPI No recurrent febrile episodes No coryzal symptoms No urinary symptoms TOCC: lives in Mainland China Attended Hospital in China USG brain unremarkable Abnormal thyroid function test

5 Physical Exam Afebrile P 158/min; SpO2 100% in RA AFNT No dysmorphism CR<2s, warm peripheries but dry oral mucosa Chest no distress, clear, AE adequate HS normal, no murmur Abd not distended, no hepatosplenomegaly, BS +ve Generalized hypotonia with head lag Spont movement of 4 limbs, reflexes normal and symmetrical

6 Investigations on Admission Hb 8.7g/dL (hypochromic microcytic) WBC, Plt normal Glucose normal VBG no aciodsis LFT normal RFT Na 167 mmol/l K 4.4 mmol/l Urea 7.8mmol/L Cr 32 umol/l

7 Hypernatremia in Children Na >145mmol/L Dehydration FENa <1% Uosm > Posm FENa >1% Uosm>= Posm FENa <1% Uosm < Posm Extrarenal losses Diarrhea Skin loss Excessive sweat Fasting / thirst Osmotic Diuresis Diuretics Glycosuria Post-obstructive diuresis Non-oliguric ATN Urine Concentrating Defect Central DI Nephrogenic DI

8 Hypernatremia in Children Not dehydrated FENa>1% Uosm > Posm FENa variable Uosm < Posm Excess sodium Increase renal solute load Salt poisoning Central hypodipsia

9 Management of Baby Mo Treat as hypernatremic dehydration NS bolus 10ml/kg ½ NS D5 solution (as maintenance + deficit replacement) However Na 171 mmol/l 174 mmol/l 177mmol/L K normal Urea 7.3mmol/L 6.4mmol/L 4.7mmol/L Cr 31umol/L 25umol/L 19 umol/l Urine ~10ml/kg/hr Switched IVF Maintenance: D5 :1/4 NS Urine ml to ml replacement with D5 Gradual normalization of Na level to 155mmol/L

10 Polyuria

11 Back to Baby Mo

12 Further Investigations FENa 0.33% (hypovolemia) Plasma osmolality 336mOsm/kg (H) Urine osmolality 171mOsm/kg (L) Plasma ADH level: 30.7pg/mL (N: pg/mL) Water deprivation test given DDAVP (0.4mcg then 0.6mcg) Persistent high volume PU Urine osmol ~120mOsm/kg

13 Further Investigations Morning cortisol 307 (N) ACTH 4.4 (N) Low dose synacthen test: adequate cortisol response Growth hormone 1.9 (N) subclinical primary hypothyroidism: TSH 13.7 (H) ft (normal) Anti TG <20 (N); anti TPO 98 (mildly raised) Thyroid scan: bilateral thyroid lobes uptakes present Urgent CT brain: NAD

14 Nephrogenic Diabetes Insipidus

15 Genetic Study Heterozygous AQP2 NM_ :c. 3G>T p. (Met1?) Heterozygous AQP2 NM_ :c 140C>T p. (Arg47Val) Both pathogenic AVPR 2 normal Conclusion: AQP2 related nephrogenic diabetes insipidus

16 Management Allow adequate fluid intake both day and night Nocturnal milk drip Fluid offered at 2 hourly intervals Management of GERD Nexium Gastrostomy feeding Low threshold for admission and intravenous hydration IV fluid hypotonic to urine 5% dextrose or 1/5 NS solution Close monitoring of body weight / fluid balance / biochemistries

17 Management of Hypernatremic Dehydration Maintenance + Replacement of Loss Water + Sodium Replace over 48hrs Rate of correction of hypernatremia not to exceed 0.5mmol/L per hour Free water deficit (Measured Na x total body water) / (Desired Na) (Total body water)

18 Example of Calculation Body weight: 5 kg Estimated Dehydration: 10% Premorbid body weight: 5.5kg Plasma Na: 165mmol/L To correct over 48hrs Maintenance Replacement of Loss Total Requirement Water 100ml x 5.5 x 2 = 1100ml Sodium 3mmol/L x 5.5 x 2 = 33mmol/L Water 5.5 x 10% x 1000= 550ml (free water deficit = 455ml) (95ml loss as isotonic solution) Sodium loss 154 /1000x ( ) = 14mmol/L Water = 1100ml + 550ml = 1650ml Sodium = mmol/L = 47mmol/L 47mmol of Na in 1650ml to be given over 48hrs ie. 1/5 NS solution at 34ml/hr

19 Management Osmotic load reduction Consult dietician x renal solute load ~15mOsm/kg per day Diuretics Hydrochlorothiazide + amiloride (potassium sparing) Prostaglandin synthesis inhibitors Indomethacin Developmental Training

20 Renal Solute Load Osmotically active substances in diet Protein (1 gram protein yields 4 mmol Urea) Sodium Potassium Anions accompanying Na and K Renal solute load of diet = 2x (Na + K) + Protein(g) x 4 Optimal: <15mOsm/kg/day Fluid (ml) required to excrete the load: 15mOsm x kg / urine osmol x 1000 (i.e. a child with urine osmolality of 100mOsm need fluid intake of 150ml/kg/day to excrete that load) Carbohydrate and lipid will NOT increase osmotic load Metabolized without byproducts requiring renal excretion

21 Diuretics Thiazides Inhibit reabsorption of sodium and chloride in distal convoluted tubule Induce mild volume depletion and thus up regulation of proximal tubular reabsorption of salt and water Less volume delivered to colkecting duct and lost in urine Hydrochlorothiazide 1mg/kg/dose BD dose Amiloride Potassium sparing effect (K supplement increase osmotic load) mg/kg/day

22 Prostaglandin Synthesis Inhibitor Indomethacin Partial chemical nephrectomy to reduce GFR 1-3mg/kg/day in 3-4 divided doses S/E: deterioration of renal function / hematological / GI upset

23 Progress Catch up growth and development