Fluids and Electrolyte Management in Neonates Arun Manglik, MD, DNB Shishu Sanjivan Hospital for Children, Kolkata.
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Fluids and Electrolyte Management in Neonates Arun Manglik, MD, DNB Shishu Sanjivan Hospital for Children, Kolkata FE Management in NB Essentials of life: Food (Nutrition) Water (Fluid/electrolyte) Shelter (environment control - temperature etc) Essentials of neonatal care: Fluid, electrolyte, nutrition management (All babies) Control of environment (All babies) Respiratory /CVS/CNS management (some babies) Infection management (some babies) Why is FE management important? Many babies in NICU need IV fluids They all don’t need the same IV fluids (either in quantity or composition) If wrong fluids are given, NB kidneys are not well equipped to handle them Serious morbidity can result from fluid and electrolyte imbalance Fluids and Electrolytes Priniciples: Total body water (TBW) = Intracellular fluid (ICF) + Extracellular fluid (ECF) Extracellular fluid (ECF) = Intravascular fluid (in vessels : plasma, lymph - IVF) + Interstitial fluid (between cells - IF) Goals: Maintain appropriate ECF volume, Maintain appropriate ECF and ICF osmolality and ionic concentrations Things to consider: Normal changes in TBW, ECF All babies are born with an excess of TBW, mainly ECF, which needs to be removed Adults are 60% water (20% ECF, 40% ICF) Term neonates are 75% water (40% ECF, 35% ICF) : lose 5-10 % of weight in first week Preterm neonates have more water (24 wks: 85%, 60% ECF, 25% ICF): lose 5-15% of weight in first week Things to consider: Normal changes in Renal Function Neonates are not able to concentrate or dilute urine as well as adults - at risk for dehydration or fluid overload Solute conc in urine ranges 50-800 mOsm/L in terms, 50-600 in PT Renal function matures with increasing: gestational age & postnatal age Things to consider: “Insensible” water loss (IWL) IWL not obvious: Skin (2/3) or Resp tract (1/3). Depends on: gestational age (more PT: more IWL) postnatal age (skin thickens with age) also consider losses of other fluids: Stool (diarrhea/ostomy), NG/OG drainage, CSF (ventricular drainage). SWL that seen = urine+stool “Insensible” water loss (IWL) Birth wt <1000gm IWL(ml/Kg/D) 100 1000-1500gm 60 >1500 20 Factors raising IWL So more fluids required Raised RR High body/ambient temp = 30%/C Warmers/PT incr IWL 50% Incr activity/crying Skin loss, trauma, omphalocele, neural tube defects Factors reducing IWL Incubators / humidified inspired gases Plexiglass heat shield Transparent plastic barriers – do not interfere in warmer functions reduce water loss 30% Assessment of FE status History: baby’s F&E status partially reflects mom’s F&E status (Excessive use of oxytocin, hypotonic IV fluid hyponatremia) Physical Examination: Weight: reflects TBW but not intravascular volume (eg. Long term paralysis and peritonitis incr BW and incr IF but decreased intravascular volume. Moral : a puffy baby may or may not have adequate fluid where it counts in his blood vessels) Weight loss Term 1-2%/D total 10% loss PT 2-3%/D total 15% loss This is due to loss of ECW and needs no replacement Assessment of FE status Physical examination (Contd) Skin/Mucosa: Altered skin turgor, sunken AF, dry mucosa, edema etc are not sensitive indicators in babies Cardiovascular: Tachycardia too much (ECF excess in CHF) or too little ECF (hypovolemia) Delayed capillary refill low cardiac output Hepatomegaly can occur with ECF excess BP changes very late Urine output Assessment of FE status Lab evaluation Serum electrolytes and plasma osmolarity Urine electrolytes, specific gravity (not very useful if the baby is on diuretics - lasix etc), FENa Blood urea, serum creatinine (values in the first few days reflect mom’s values, not baby’s) ABG (low pH and bicarb may indicate poor perfusion) Management of F&E Goal: Allow initial loss of ECT over first week (as reflected by wt loss), while maintaining normal intravascular volume and tonicity (as reflected by HR, UOP, lytes, pH). Subsequently, maintain water and electrolyte balance, including requirements for body growth. Individualize approach (no “cook book” is good enough!) Management of F&E - D1 Term Req.= Urine + IWL – Wt loss On IV fluids solute load 15mOsm/Kg With urine osmolality 300, urine=50ml/Kg IWL = 20ml/kg Wt loss = 10gm/Kg Req.= 50 + 20 – 10 = 60ml/Kg PT more IWL Guidelines for FE Birth wt Fluid Day1 Day2 onwards 1500+ 10D 60 75 Add 15ml/D 1000 – 1500 10D 80 95 Add 15ml/D <1000 5-10D + Na/K 100 115 Add 15ml/D Let there be lytes! Electrolyte requirements: For the first 1-3 days, sodium, potassium, or chloride are not generally required Later in the first week, needs are 1-2 mEq/kg/day (1 L of NS = 150+ mEq; 150 cc/kg/day of 1/4 NS = 5.9 mEq/kg/day which is too much) After the first week, during growth, needs are 2-3 or even 4 mEq/kg/day F&E in common neonatal conditions RDS: Adequate but not too much fluid. Excess leads to hyponatremia, risk of BPD. Too little leads to hypernatremia, dehydration BPD: Need more calories but fluids are usually restricted: hence the need for “rocket fuel”. If diuretics are used, w/f ‘lyte problems. May need extra calcium. PDA: Avoid fluid overload. Keep at 120ml/Kg. If indocin is used, monitor urine output. F&E in common neonatal conditions Asphyxia: May have renal injury or SIADH. Restrict fluids initially, avoid potassium. May need fluid challenge if cause of oliguria is not clear. NEC: Need more fluids. May go into shock. Give 200ml/Kg ARF:Give 400ml/sq m/D + urine output Common ‘lyte problems Sodium: Hypo (<130 mEq/L; worry if <125) Hyper (>150 mEq/L; worry if >150) Potassium: Hypo (<3.5 mEq/L; worry if <3.0) Hyper > 6 mEq/L (non-hemolyzed) (worry if >6.5 or if ECG changes ) Calcium: Hypo (total<7 mg/dL; ion<4) Hyper (total>11; ion>5) Hyponatremia Sodium levels often reflect fluid status rather than sodium intake ECF Excess Excess IVF, CHF, Sepsis, Paralysis Restrict fluids ECF Normal Excess IVF, SIADH, Pain, Opiates Restrict fluids ECF Deficit Diuretics, CAH, NEC (third spacing) Increase sodium intake Hypernatremia Hypernatremia is usually due to excessive IWL in first few days in VLBW infants (micropremies). Increase fluid intake and decrease IWL. Rarely due to excessive hypertonic fluids (sod bicarb in babies with PPHN). Decrease sodium intake. Potassium stuff Potassium is mostly intracellular: blood levels do not usually indicate total-body potassium pH affects K+: 0.1 pH change=>0.3-0.6 K+ change (More acid, more K; less acid, less K) ECG affected by both HypoK and HyperK: Hypok:flat T, prolonged QT, U waves HyperK: peaked T waves, widened QRS, bradycardia, tachycardia, SVT, V tach, V fib Hypo- and Hyper-K Hypokalemia: Leads to arrhythmias, ileus, lethargy Due to chronic diuretic use, NG drainage Treat by giving more potassium slowly Hyperkalemia: Increased K release from cells following IVH, asphyxia, trauma, IV hemolysis Decreased K excretion with renal failure, CAH Medication error very common Management of Hyperkalemia Stop all fluids with potassium Calcium gluconate 1-2 cc/kg (10%) IV Sodium bicarbonate 1-2 mEq/kg IV Glucose-insulin combination Lasix (increases excretion over hours) Kayexelate 1 g/kg PR (not with sorbitol! Not to give PO for premies!) Dialysis/ Exchange transfusion Calcium At birth, levels are 10-11 mg/dL. Drop normally over 1-2 days to 7.5-8.5 in term babies. Hypocalcemia: Early onset (first 3 days):Premies, IDM, Asphyxia If asymptomatic, >6.5: Wait it out. Supplement calcium if <6.5 Late onset (usually end of first week)”High Phosphate” type: Hypoparathyroidism, maternal anticonvulsants, vit. D deficiency etc. Reduce renal phosphate load Monitoring fluid therapy • Wt loss 1% /d ( loss > 2% /d = dehydration / gain > 1% /d = overhydration) • Urine : 1-3ml/kg/hr (< 1: dehydration , > 4 : overhydration / diuresis) • Na : 135-145 mEq/L / K : 4-5 mEq/ L • Osmolality : 270-285 mosm/L • Urine sp.gr. : 1005-1015 • Blood glucose: 60-100 mg/dl Common fluid problems Oliguria : UOP< 1cc/kg/hr. Prerenal, Renal, or Postrenal causes. Most normal term babies pee by 24-48 hrs. Don’t wait that long in sick l’il babies! Check Baby, urine, FBP. Try fluid challenge, then lasix. Get USG if no response Dehydration: Wt loss, oliguria+, urine sp. gravity >1.012. Correct deficits, then maintenance + ongoing losses Fluid overload: Wt gain, often hyponatremia. Fluid+ sodium restriction