Fluids and Electrolyte Management in Neonates

Fluids and Electrolyte Management in Neonates

AHMED BAMAGAMBBSKAUH

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 fluidsThey 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 themSerious 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 IWL(ml/Kg/D)<1000gm 100

1000-1500gm

60

>1500 20

Factors raising IWL

Raised RRHigh body/ambient temp = 30%/CWarmers/PT incr IWL 50%Incr activity/cryingSkin loss, trauma, omphalocele,

neural tube defects

So more fluids required

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% lossThis is due to loss of ECW

and needs no replacement

Assessment of FE statusPhysical 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

outputHepatomegaly can occur with ECF excessBP 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 lossOn IV fluids solute load 15mOsm/KgWith urine osmolality 300,

urine=50ml/KgIWL = 20ml/kgWt loss = 10gm/KgReq.= 50 + 20 – 10 = 60ml/KgPT 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 problemsSodium:

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)

Increasesodium 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 potassiumCalcium gluconate 1-2 cc/kg (10%) IVSodium bicarbonate 1-2 mEq/kg IVGlucose-insulin combinationLasix (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