Fluids and Electrolyte Management in Neonates AHMED BAMAGA

Fluids and Electrolyte Management in Neonates AHMED BAMAGA MBBS KAUH

FE Management in NB z. Essentials of life: y. Food (Nutrition) y. Water (Fluid/electrolyte) y. Shelter (environment control - temperature etc) z. Essentials of neonatal care: y. Fluid, electrolyte, nutrition management (All babies) y. Control of environment (All babies) y. Respiratory /CVS/CNS management (some babies) y. Infection management (some babies)

Why is FE management important? z. Many babies in NICU need IV fluids z. They all don’t need the same IV fluids (either in quantity or composition) z. If wrong fluids are given, NB kidneys are not well equipped to handle them z. Serious morbidity can result from fluid and electrolyte imbalance

Fluids and Electrolytes z. Priniciples: y. Total body water (TBW) = Intracellular fluid (ICF) + Extracellular fluid (ECF) y. Extracellular fluid (ECF) = Intravascular fluid (in vessels : plasma, lymph - IVF) + Interstitial fluid (between cells - IF) z. Goals: y. Maintain appropriate ECF volume, y. Maintain appropriate ECF and ICF osmolality and ionic concentrations

Things to consider: Normal changes in TBW, ECF z. All babies are born with an excess of TBW, mainly ECF, which needs to be removed y. Adults are 60% water (20% ECF, 40% ICF) y. Term neonates are 75% water (40% ECF, 35% ICF) : lose 5 -10 % of weight in first week y. 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 z. Neonates are not able to concentrate or dilute urine as well as adults - at risk for dehydration or fluid overload z. Solute conc in urine ranges 50 -800 m. Osm/L in terms, 50 -600 in PT z. Renal function matures with increasing: gestational age & postnatal age

Things to consider: “Insensible” water loss (IWL) z. IWL not obvious: Skin (2/3) or Resp tract (1/3). Depends on: ygestational age (more PT: more IWL) ypostnatal age (skin thickens with age) yalso 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 <1000 gm IWL(ml/Kg/D) 1000 -1500 gm 60 >1500 20

Factors raising IWL So more fluids required z. Raised RR z. High body/ambient temp = 30%/C z. Warmers/PT incr IWL 50% z. Incr activity/crying z. Skin loss, trauma, omphalocele, neural tube defects

Factors reducing IWL z. Incubators / humidified inspired gases z. Plexiglass heat shield z. Transparent plastic barriers – do not interfere in warmer functions reduce water loss 30%

Assessment of FE status z History: baby’s F&E status partially reflects mom’s F&E status (Excessive use of oxytocin, hypotonic IV fluid hyponatremia) z Physical Examination: y. Weight: reflects TBW but not intravascular volume (eg. Long term paralysis and peritonitis incr BW and incr IF but decreased intravascular volume. y. Moral : a puffy baby may or may not have adequate fluid where it counts in his blood vessels)

Weight loss z. Term 1 -2%/D total 10% loss z. PT 2 -3%/D total 15% loss z. This is due to loss of ECW and needs no replacement

Assessment of FE status Physical examination (Contd) y. Skin/Mucosa: Altered skin turgor, sunken AF, dry mucosa, edema etc are not sensitive indicators in babies y. Cardiovascular: x. Tachycardia too much (ECF excess in CHF) or too little ECF (hypovolemia) x. Delayed capillary refill low cardiac output x. Hepatomegaly can occur with ECF excess x. BP changes very late y. Urine output

Assessment of FE status Lab evaluation y. Serum electrolytes and plasma osmolarity y. Urine electrolytes, specific gravity (not very useful if the baby is on diuretics - lasix etc), FENa y. Blood urea, serum creatinine (values in the first few days reflect mom’s values, not baby’s) y. ABG (low p. H and bicarb may indicate poor perfusion)

Management of F&E z. 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, p. H). Subsequently, maintain water and electrolyte balance, including requirements for body growth. z. Individualize approach (no “cook book” is good enough!)

Management of F&E - D 1 Term z. Req. = Urine + IWL – Wt loss z. On IV fluids solute load 15 m. Osm/Kg z. With urine osmolality 300, urine=50 ml/Kg z. IWL = 20 ml/kg z. Wt loss = 10 gm/Kg z. Req. = 50 + 20 – 10 = 60 ml/Kg z. PT more IWL

Guidelines for FE Birth wt Fluid Day 1 Day 2 onwards 1500+ 10 D 60 75 Add 15 ml/D 1000 – 1500 10 D 80 95 Add 15 ml/D <1000 5 -10 D + Na/K 100 115 Add 15 ml/D

Let there be lytes! z. Electrolyte requirements: y. For the first 1 -3 days, sodium, potassium, or chloride are not generally required y. Later in the first week, needs are 1 -2 m. Eq/kg/day (1 L of NS = 150+ m. Eq; 150 cc/kg/day of 1/4 NS = 5. 9 m. Eq/kg/day which is too much) y. After the first week, during growth, needs are 2 -3 or even 4 m. Eq/kg/day

F&E in common neonatal conditions z. RDS: Adequate but not too much fluid. Excess leads to hyponatremia, risk of BPD. Too little leads to hypernatremia, dehydration z. 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. z. PDA: Avoid fluid overload. Keep at 120 ml/Kg. If indocin is used, monitor urine output.

F&E in common neonatal conditions z. Asphyxia: May have renal injury or SIADH. Restrict fluids initially, avoid potassium. May need fluid challenge if cause of oliguria is not clear. z. NEC: Need more fluids. May go into shock. Give 200 ml/Kg z. ARF: Give 400 ml/sq m/D + urine output

Common ‘lyte problems z Sodium: y. Hypo (<130 m. Eq/L; worry if <125) y. Hyper (>150 m. Eq/L; worry if >150) z Potassium: y. Hypo (<3. 5 m. Eq/L; worry if <3. 0) y. Hyper > 6 m. Eq/L (non-hemolyzed) (worry if >6. 5 or if ECG changes ) z Calcium: y. Hypo (total<7 mg/d. L; ion<4) y. Hyper (total>11; ion>5)

Hyponatremia z. Sodium levels often reflect fluid status rather than sodium intake

Hypernatremia z. Hypernatremia is usually due to excessive IWL in first few days in VLBW infants (micropremies). Increase fluid intake and decrease IWL. z. Rarely due to excessive hypertonic fluids (sod bicarb in babies with PPHN). Decrease sodium intake.

Potassium stuff z. Potassium is mostly intracellular: blood levels do not usually indicate total-body potassium zp. H affects K+: 0. 1 p. H change=>0. 3 -0. 6 K+ change (More acid, more K; less acid, less K) z ECG affected by both Hypo. K and Hyper. K: y. Hypok: flat T, prolonged QT, U waves y. Hyper. K: peaked T waves, widened QRS, bradycardia, tachycardia, SVT, V tach, V fib

Hypo- and Hyper-K z. Hypokalemia: y. Leads to arrhythmias, ileus, lethargy y. Due to chronic diuretic use, NG drainage y. Treat by giving more potassium slowly z. Hyperkalemia: y. Increased K release from cells following IVH, asphyxia, trauma, IV hemolysis y. Decreased K excretion with renal failure, CAH y. Medication error very common

Management of Hyperkalemia z. Stop all fluids with potassium z. Calcium gluconate 1 -2 cc/kg (10%) IV z. Sodium bicarbonate 1 -2 m. Eq/kg IV z. Glucose-insulin combination z. Lasix (increases excretion over hours) z. Kayexelate 1 g/kg PR (not with sorbitol! Not to give PO for premies!) z. Dialysis/ Exchange transfusion

Calcium z At birth, levels are 10 -11 mg/d. L. Drop normally over 1 -2 days to 7. 5 -8. 5 in term babies. z Hypocalcemia: y. Early onset (first 3 days): Premies, IDM, Asphyxia If asymptomatic, >6. 5: Wait it out. Supplement calcium if <6. 5 y. 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 -3 ml/kg/hr (< 1: dehydration , > 4 : overhydration / diuresis) • Na : 135 -145 m. Eq/L / K : 4 -5 m. Eq/ L • Osmolality : 270 -285 mosm/L • Urine sp. gr. : 1005 -1015 • Blood glucose: 60 -100 mg/dl

Common fluid problems z. Oliguria : UOP< 1 cc/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 z. Dehydration: Wt loss, oliguria+, urine sp. gravity >1. 012. Correct deficits, then maintenance + ongoing losses z. Fluid overload: Wt gain, often hyponatremia. Fluid+ sodium restriction