Neonatal Fluid and Electrolyte Balance

Nutrition, Fluid and Electrolyte

• Fluid and electrolyte management in newborns is crucial for their health and development.

Session Objectives

• By session end, participants should be able to describe neonatal transitions, explain fluid compartments, describe fluid ionic composition, describe acid-base disorders, calculate maintenance fluid needs, and analyze electrolyte disorders.

Introduction

• The fetus has high total body water (TBW), which decreases to approximately 75% body weight in term infants.
• Transition to neonatal life causes major changes in water and electrolyte regulation.
• Weight loss is mainly water loss, with term infants losing 10% and preterm infants losing 15% of birth weight in the first 10 days of life.
• Premature infants have a higher TBW than term infants.
• Water is the major constituent of body tissues.
• Newborns are susceptible to water and electrolyte derangements due to kidney immaturity, increased insensible water losses, postnatal body water changes, and inability to independently access water.
• Gestational age impacts TBW, with extreme preterms at 90% body weight and term neonates at 75% TBW.
• Postnatal renal function changes, including increased urine output and glomerular filtration rate (GFR), cause physiological diuresis.
• Preterm infants have high urinary sodium and bicarbonate loss.

Neonatal Management

• Neonatal fluid and electrolyte management is fundamental for neonatal care and requires careful monitoring and adjustments.
• It supports vital functions, promotes growth, and prevents complications like dehydration and organ dysfunction.
• It necessitates understanding neonatal renal and gastrointestinal systems.
• Responds to dynamic changes in early life.

Definitions

• Intracellular fluid is fluid within cells, whereas extracellular fluid is outside cells in interstitial and intravascular spaces.
• Interstitial fluid is between cells in tissue interspaces, and intravascular fluid is within vessels.
• Homeostasis is the maintenance of constant conditions in the internal environment.

Fluid Transport

• Diffusion is the movement of molecules/solutes from high to low concentration across a semipermeable membrane.
• Osmosis is the one-way passage of water from low to high particle concentration.
• Filtration is fluid movement through a filter under pressure, preventing passage of certain molecules.
• Active transport moves electrolytes from low to high concentration using ATP against the concentration gradient.

Body Fluid Composition

• TBW includes extracellular fluid (ECF), encompassing intravascular, interstitial, and intracellular fluid.
• Total body water (TBW) is the sum of intracellular fluid (ICF) plus extracellular fluid (ECF).
• The percentage of TBW to body weight and distribution across fluid compartments changes with gestational age (GA).
• As gestational age increases, TBW and ECF decrease, while ICF increases.
• TBW is 75% of body weight in term newborns and 80% in 27-week gestation infants with 45% and 70% ECF volumes, respectively.

Perinatal Changes in Total Body Water

• During the first 10 days of life, body weight decreases as the ECF reduces.
• Fluid loss comes from isotonic reduction in extracellular water.
• Diuresis magnitude and relative weight loss decrease alongside increases in gestational age (GA).
• Weight loss variations: Preterm infants lose 10-15% of birth weight while term breastfed infants lose 4-7% on day one.
• Postnatal diuresis ranges from 1-3 mL/kg per hour in term infants, with higher rates in preterm infants.

Three Phases of Water and Sodium Change

• Studies show preterm infants exhibit consistent fluid and sodium homeostasis.
• Three phases of water and sodium changes are seen in preterm neonates during the first 5-7 days.
• Prerenal issues reduce renal blood flow if level <1%.
• Acute kidney injury occurs with a level of 2.5%.

Phases

• Pre-diuretic phase (Day 1): Oliguria with low GFR and low fractional excretion of sodium (FENa), due to birth-associated renal nerve stimulation.
• Diuretic and natriuretic phase (Days 2-3): High urine output and sodium losses from increased GFR and FENa, lung fluid absorption causes extracellular volume increase and renal vascular resistance reduction.
• Post-diuretic phase (Days 4-5): Urine output depends on fluid intake, GFR and FENa are reduced compared to days 2-3.

Electrolyte Composition

• Solute compositions differ significantly between the ICF and ECF.
• Sodium (Na) and chloride (Cl) are the dominant cation and anion in ECF, respectively.
• Sodium and chloride concentrations ([Na], [CI]) are lower in the ICF.
• Potassium (K) is the most abundant ICF cation, and its concentration ([K+]) within cells is approximately 30 times higher than in the ECF.
• Proteins, organic anions, and phosphate are the most plentiful anions in the ICF.
• Anion dissimilarity between ICF and ECF depends on impermeable intracellular molecules.
• Cation distribution (Na+ and K+) relies on the Na+, K+-adenosine triphosphatase (ATPase) pump and membrane ion channels.
• Serum electrolyte concentrations ([Na+], [K+], and [Cl-]) do not always reflect total body content.
• Intracellular [K+] is higher than serum concentration.
• K+ shift from the intracellular space (ICS) maintains possible elevated serum [K+] despite K+ losses.

Electrolytes

• Electrolytes conduct electric current.
• Cations in the body equal anions.

Fluid Homeostasis Mechanisms

• Neonates maintain fluid homeostasis through the Renin-Angiotensin-Aldosterone system (RAAS).
• They also use the Arginine vasopressin system (antidiuretic hormone (ADH)).
• The Atrial natriuretic peptide (ANP) system also plays a part.

Renin-Angiotensin-Aldosterone System (RAAS)

• Renin is secreted by the juxtaglomerular apparatus.
• Angiotensin I is produced when renin acts on angiotensinogen.
• Angiotensin II (AII) is converted from Angiotensin I in the lungs via ACE.
• Vasoconstriction happens in the afferent and efferent arterioles, increasing glomerular hydraulic pressure.
• Decreased renal blood flow raises the rate of tubular injury and uremic toxin retention.

Hypothalamus

• The hypothalamus produces AVP, stored in the pituitary gland; stimulated by baroreceptors or osmoreceptors.
• The pituitary gland releases AVP into the bloodstream.
• AVP binds kidney receptors, increasing aquaporin production for water reabsorption in the collecting duct.
• This is antidiuresis, less urine and more concentrated urine as a result.

Atrial Natriuretic Peptide (ANP) System

• Atria release ANP, which enters the bloodstream during atrial stretch from increased blood volume.
• The heart releases ANP in response to increasing hypertension and blood volume.
• ANP lowers blood pressure by increasing sodium and water excretion.
• ANP also relaxes blood vessels, and blocks both aldosterones.
• ANP binds receptors that activate guanylyl cyclase, converting GTP to cGMP.
• CGMP activates cGMP-dependent protein kinases modulating ion channel opening.

Renal Function

• Neonatal renal function varies due to increasing gestational age (GA) and postnatal hemodynamic changes.
• Developmental immaturity, especially in preterm infants, can cause water and electrolyte imbalance, particularly in ability to concentrate urine, the reabsorption of sodium and bicarbonate and secretion of potassium and hydrogen.
• Premature GA has lower glomerular filtration rate (GFR).
• Full-term infants GFR of approximately 26 mL/min per 1.73 m².
• 27 week preterm infants have a GFR of 13.4 mL/min per 1.73 m².
• At birth, GFR increases due to superficial nephron recruitment and increased renal blood flow (RBF) from renal vascular resistance reduction and systemic blood pressure increase.
• After two weeks, GFR of term infants doubles to 54 mL/min per 1.73 m² compared to 16.2 mL/min per 1.73 m² in 27-week neonates.
• Clinically, serum creatinine (SCr) indicates estimate of GFR that varies with gestational age
• Newborns have reduced GFR and decreased early distal tubule activity to concentrate or dilute urine.
• This may cause dehydration or fluid overload.
• Gestational and postnatal age matures renal function.

Sources of Water Loss

• Sensible water loss is measured from urine, stool, and cerebrospinal fluid (CSF), while insensible water loss (IWL) is not easily measured, it occurs through skin (66%) and respiratory pathways (34%).
• Lower gestational age equals greater IWL from immature skin.
• Factors increasing IWL include premature skin, phototherapy, skin defects, radiant warmers, and fever.
• Mature skin, heat shields, increased humidity are factors that decrease IWL.
• Low urinary volume is produced by Neonates initially after which it increases to 45 mL/kg per day.
• Significant insensible water loss can lead to significant insensible water loss due to evaporation through the skin.
• Those most at risk are extremely low birth weight (ELBW) infants.
• Surface area-to-volume ratio increases alongside decreasing gestational age (GA).
• Term infants lose about half of insensible losses through the respiratory system.
• Higher water loss occurs with rates and decreases in humidified air.
• Preterm infant skin losses of water are respiratory.
• Antenatal glucocorticoids promote lung maturation, leading to better skin and kidney maturation plus less hypernatremia, and earlier diuresis and natriuresis.
• Losses vary from age/conditions, impacting water and sodium balance in neonates.

Fluid and Electrolyte Status

• Newborns' fluid/electrolyte balance reflects maternal hydration. Oxytocin/diuetics can cause hyponatremia, while steroids may increase skin maturity and decrease IWL.
• Oligohydramnios can indicate congenital renal dysfunction whereas in-utero hypoxemia acute tubular necrosis
• Changes in an infant's weight reflect TBW changes, depending on factors like gestational age and the compartment affected.
• Paralytic treatments and peritonitis raise interstitial fluid volume and body weight; daily weight checks for age newborns.
• Altered skin turgor, fontanelle, mucous, can indicate electrolyte/imbalance but are not sensitive.

Assessment

• An expected reduction of weight occurs 10 to 12% during the first week (normal reduction of TBW)
• Examine the skin and any mucosal manifestations that arise
• All newborns require baseline admission weight and should be taken every week and Wednesday if requested
• Weigh preterm (< 28 weeks gestation) intensive newborns every day.
• As a result of hypovolemia, tachycardia and capillary time may be delayed.
• Hepatomegaly is also a side effect that occurs with increased ECF
• Drop in blood pressure and increased oxygen saturation is also possible
• Decreased output means input balance and measurements must be observed
• Low balance may also mean electrolyte deficiencies.

Laboratory Studies

• Serum electrolyte and a sample of plasma can also be taken to reflect fluid and electrolyte balance
• Expected output is 1 to 3 mL/kg/hour
• Urine measures are a viable option for accurate water output or dilute measures
• Fraction of sodium indicates reabsorption (FENa) if high

Assessmenent continued

• Blood urea nitrogen can indicate kidney deficiencies in preterm infants
• Arterial blood measurements can show data volume
• Allow physiological ECF while monitoring

Management Goals

• Management goals: minimize weight loss by managing ICF/ECF volumes and electrolyte concentrations to monitor and manage growth and adequate growth
• Total fluids (Maintenance * Growth)
• Maintenance (SWL + IWL
• Infant is expected to decrease 3% to 5% in its first day
• Small increments and clinical water levels to monitor
• Na supplements needed for smaller-age babies

Premature Infant Goals

• Anticipate losses during the first few days with adjustments until growth stable
• Assess electrolytes in urine/plasma to have to reassess after 2 days
• Examine SG depending of what they measure every 6 hours
• Use Sodium to adjust fluid intake to a volume of 5% per day

Electrolyte Requirement

• No routine electrolytes except Ca2+: 1 mmol/kg/day and add calcium routinely to less than 1500gm, PNA, infant of Diabetic mother
• Add electrolytes such as Na+: 3 mmol/kg/day if very preterm and may need more and K+: 2 mmol/kg/day after 48hours and and Ca2 1 mmol/kg/day
• Maintenance includes the following combination of sodium and glucose combined with glucose to treat, or rehydrate neonates

Treatment and Cholride Balance

• Type of fluid used (IV required = need for fluid intake and volume)
• Rapid fluid transfer is used as bolus
• Formula calculation = Weight and clinical state
• High percentage may lead to reduced volume or dehydration
• Moderate values may lead to reduced skin levels Composition
• Maintain water formula and glucose values If 1000gm add gluconate to control flow

Treatment for Day 2

• Use Glucose at 5% daily
• Electrolyte solution

Fluid Intake

• Extra to intake may be bad in heat or low water

Fluid Restriction

• In Dep/As ATN
• 2/3 OF MAINTAnence will help fix the volume, urine

Replacement Therapy

• If you are concerned about the weight
• Divide it

Fluid Preparation.

• 5% DW and 40-9% General Solution formula Needed
• Formula is as follows

Common neonatal conditions to consider

If in RDS

• Need to much fluid for it to turn the electrolyte levels to change Low need in rocket fuel PDD overload

Specific neonatal fluids and electrolytes

• Asphyxia: May have renal injury or SIADH; use K and challenge is urine is clear
• NEC: Need more at 200 mL/kg
• Give high water over urin

Water Balance

• If imbalance occurs then you have to keep a close check
• Electrolyte change or high increase

Balance.

• Dependant on the newborne
• High low fluid will lead to the same problems/issue or over

Fluid Imbalance

• For the isotonics one there are some side effects like vomiting and loss of water VLBW will need to be tested to ensure proper balancing
• Symptoms may mean less urine or more SG
• A low FENa level is common for 32 weekers gestational age.
• If a isonatremic or water

Side effects such as Edemas which lead to the following side effects and diagnoses include

Include

• Congenial loss
• Pulmonis
• Or Dyspnea Includes volume management and restriction.
• All treatments must use the scale before use or if the pt is pregnant.

Hyponatremia

Can be made from osmotic balances and fluids. Is caused by excessive intake.

• If found increase sodium intake and follow

Diagnosis

Increased electrolytes decrease SG if that’s known increase to the proper ratios

• A decrease if function/activity balance and test for it.

Therapy

• Test for the fluid and balance test, to meet proper ratios
• Check after. Use electrolytes

Hyponatremia Causes by Factors

• Osmotics . VLBW can cause loss _Arenal tubulars if no proper
• This can also lead to EC which skin, skin and ETC losses in these

Hypovolemic.

Decreased levels need to be taken into consideration

• Urine imbalances and recheck and water levels

Euvolemic Levels

• It's important to have hormone testing.

In these cases we use testing in this case and electrolytes. (ADH) hormones

Excess volume and imbalances, etc

Excess Factor Causes.

Sepsis, abornomal conditions like imbalances and electrolyte imbalances Treat

• Make sure they are following the right

Hypernatremia

• High levels in some cases, such as 145 - 160

Pre.

• Most likely to show up early. Improper preparation and other factors and or issues within body

• Symptoms include Poor speech Or other major deficiencies

Theat

• Increase and track fluids

Potassium

• K can not affect PH
• 0- .06 will be excreted

A: Hyperkalemia

If that occurs in the test need to adjust the solution test, A+ loss diuretics. This needs constant care to retest Abraham

Hyperkarleimia symptoms

VLBW may not show and symptoms before and after Or medication error can cause the issues

• Make sure these are tracked properly.

Tests.

QRS V-Fib

Hyperkelmia

• High if no major ECG changes, adjust with Stop K/ check solutions Then adjust when the result

Salbumatol has proven to stabilize glucose to treat high levels.

ECG

Can help stabilize the heart

Make sure to stabilize before doing anything drastic Always consult. A + B - this can be corrected by electrolytes Can be from kidney and low hydration. Make sure you are checking for this in the fluid balances. Rehydrate as need.

Nursing

• Monitor for any test levels or changes and follow the proper guide.

This quiz covers key concepts related to neonatal fluid and electrolyte balance, including insensible water loss, the impact of antenatal glucocorticoids, and complications arising from oligohydramnios. It also addresses urine output ranges and the function of electrolytes in newborns.