Introduction

Aim

Definition of Terms

Assessment

Management

Companion Documents

Evidence Table 

Introduction

Disorders of fluid and electrolyte imbalance are amongst the most common disorders encountered in unwell neonates (both term and preterm). The fluid and electrolyte requirements of the neonate are unique due to fluids shifts within the first few days and weeks of life. At birth, there is an excess of extracellular fluid which decreases over the first few days after birth; extracellular fluid and insensible water losses increase as weight and gestational age decrease. Therefore, appropriate management of fluid and electrolytes must take into consideration the birth weight, gestational age and corrected age. In addition, consideration needs to be given to the unwell term or preterm neonate as the disease pathophysiology may significantly influence fluid and electrolyte requirements.

Fluid management in the preterm neonate is specific and challenging due to increases in insensible water loss, reduced renal function and low birth weight. Please refer to the Neonatologist on duty or PIPER service for specific advice.

Aim

To maintain adequate hydration, fluid and sodium balance in the neonate admitted to the Butterfly Ward neonatal intensive care unit (NICU) or high dependency unit (HDU).

For intravenous fluid management of the neonate outside Butterfly ward please refer to Ward management of a neonate. 

Definition of Terms

Neonate                               A neonate less than 28 days of age

Term                                     A neonate born after 37 weeks of completed gestation

Preterm                               A neonate born before 37 weeks of completed gestation

Late Preterm                       A neonate born between 32 and 36+6 weeks of completed gestation

Very Preterm                       A neonate born between 28 and 31+6 weeks of completed gestation

Extremely Preterm             A neonate born before 28 weeks of completed gestation         

Assessment

Fluid balance is a function of the distribution of water in the body, water intake and water losses. Total body water (TBW) distribution gradually changes with increasing gestational age of the foetus, from the extreme preterm with TBW constituting 90% of body weight, to the term neonate with 75% TBW. In addition to this gradual reduction with gestational age is a more abrupt reduction of TBW that occurs approximately 48 to 72 hours after birth which is closely related to the cardiopulmonary adaption. 

INSENSIBLE WATER LOSS (IWL)

Insensible water loss occurs via the skin and mucous membrane (two thirds) and respiratory tract (one third). An important variable influencing IWL is the maturity of neonate skin, with greater IWL in preterm babies resulting from evaporation through the immature epithelial layer.

• Phototherapy may increase IWL and therefore fluid intake may need to be increased by 10 – 20 ml/kg/day

** Refer to Phototherapy for Neonatal Jaundice  RCH nursing guideline

** Refer to Environmental Humidity for Premature Neonates RCH nursing guideline

RENAL FUNCTION/URINE OUTPUT

Foetal urine flow steadily increases with gestational age reaching 25 – 50 mL/hr at term and dropping to 8 – 16mL/hr (1-3mL/kg/hr) at birth reflecting the large exchange of TBW during foetal life and the abrupt change occurring with cardiopulmonary adaption after birth. In addition, glomerular filtration rates (GFR) are low in utero and remain low at birth and gradually increase in the neonatal period. With a changing GFR and variable urine concentration, all newborns undergo a diuresis in the days following birth resulting from a reduction of TBW.

• Urine output should be 1 – 3 mL/kg/hr by the 3^rd day of life
• Urine electrolytes and osmolarity offer additional information as to urine concentrating ability. Although these can be difficult to interpret in preterm babies

BODY WEIGHT

Contraction of TBW accounts for early postnatal weight loss and results in a 10-15% weight loss in preterm babies and 5-10% weight loss in term babies.

Where clinically appropriate:

• All patients should have a baseline weight completed prior to commencement of IV Fluids (i.e. birth weight and/or admission weight)
• Patients should be weighed twice per week at a minimum (Sunday and Wednesday Day) and more frequently as ordered

PHYSICAL EXAMINATION

A number of physical signs can be used in the assessment of fluid status however they can be unreliable and therefore must be observed within the context of body weight, haemodynamic monitoring, haematocrit, serum chemistries, acid-base status and urine output.
Physical assessment of hydration status includes the assessment of:

• Presence and severity of oedema
• Skin turgor
• Mucous membranes
• Periorbital tissue
• Anterior fontanelle
• Altered conscious state

HAEMODYNAMIC MONITORING

All patients receiving IV fluids for acute conditions should have both oxygen saturation and cardiorespiratory monitoring. In addition, heart rate, pulse volumes, respiratory rate and capillary refill time should be assessed at hourly intervals. 

• HEART RATE is an early indicator of cardiovascular compromise/compensation
• BLOOD PRESSURE is an important indicator of intravascular volume however hypotension is usually a late sign of intravascular volume depletion
• PULSE VOLUMES are an important early indicator of intravascular volume loss. They will be decreased in the dehydrated neonate and coupled with tachycardia.
• TACHYPNOEA is an early sign of metabolic acidosis that may be the result of inadequate intravascular volume
• CAPILLARY REFILL TIME (CRT) is one factor measured when assessing overall perfusion, but by itself is not reliable.
• CRT > 3 in the term neonate may be indicative of a decreased intravascular volume or poor tissue perfusion

*** Monitoring may be ceased by order of the medical team in the patient receiving long term intravenous fluid with stable serum electrolytes***

HAEMATOCRIT

In the neonatal period, a physiologic increase in haematocrit occurs due to a fluid shift away from the intravascular compartment. An increase in haematocrit also occurs as a result of dehydration due to a decrease in plasma volume. 
Normal Haematocrit (Term Newborn) = 0.44 – 0.64 
Normal Haematocrit (3 months) = 0.32 – 0.44
RCH Laboratory = 0.31 – 0.55

SERUM BIOCHEMISTRY

The requirement of both sodium (Na⁺) and potassium (K⁺) is 2 – 4 mmoL/kg/24 hours. A sodium (Na⁺) value of 135 – 145 mEq/L is indicative of appropriate total body weight and sodium balance which are important factors in maintaining hydration status in the neonate. Changes in serum sodium concentration need to be assessed in the context of total body weight and any increase or decrease in weight.

• All patients receiving IV Fluids for acute conditions should have serum electrolytes and glucose checked before commencing the infusion (where possible) and again within 24 hours or sooner if clinically indicated
• Serum electrolytes and glucose should be checked at a minimum every 24 – 48 hours thereafter
• Serum osmolarity is an important consideration in the assessment of hydration; 285 mOsm/L is the normal value.

ACID-BASE STATUS

A metabolic acidosis can be suggestive of decreased intravascular volume and hypersomolarity.

• A decreasing base excess (BE) in the context of decreased urine output, decreased mean arterial pressure and a prolonged CRT is suggestive of dehydration
  • Normal base excess (BE)     =              -3 to +3 mEq/L
• A widening anion gap is reflective of dehydration with a deceased intravascular volume as lactic academia follows poor tissue perfusion.
  • Normal anion gap                 =              8 – 16 mEq/L

Management

GENERAL CONSIDERATIONS

• If a neonate weighs less than birth weight, utilise birth weight in all fluid calculations, unless specified by the medical team
• 500 mL fluids bags should be used within the neonatal population – both term and preterm
• Intravenous Fluids +/- additives should be changed every 24 hours including patient stock bags
• 3-way taps should be attached to each infusion delivered via a syringe; these are placed at the end of the syringe before attachment of the minimum volume extension tubing allowing for access to withdraw boluses etc.
• Every hour the volume infused (VI) is to be cleared, documented and a new volume to be infused (VTBI) set 
• The concentration of glucose and/or amino acids in the intravenous solution MUST BE CONSIDERED in determining appropriate site for infusion (i.e. central or peripheral)
  • Glucose concentrations more than 12.5 % Glucose require central venous access
  • Amino acid concentrations more than or equal to 50g/L require central venous access
  • Inotropes require central venous access, preferably via an inotrope dedicated line. Low dose dobutamine may run peripherally whilst central venous access is being obtained.

LABELLING

All patients with intravenous fluids require labels on 1) the fluid bag/syringe, 2) the IV line (closest to the patient), and 3) the pump.

In all circumstances, intravenous fluid bags and syringes should be labelled with a fluid label printed via EMR.

All labels, handwritten or printed via EMR, require the following:

Infusions with no additives:

• Date
• Time
• Patient MRN
• Patient Name
  • Signatures of both nurses who prepared and checked the fluid

Infusions with additives:

• Additive
• Date
• Time
• Patient Name
•  Patient MRN
• Signatures of both nurses who prepared and checked the fluid

TYPE OF FLUID

As described above (Assessment – RENAL FUNCTION), neonates undergo a diuresis within the first 24hours after birth and therefore electrolyte additives are not required within the first 24 hours of life unless clinically indicated. 

** Refer to EMR MAR Product Instructions/Mixture Components for preparation instructions

Total parenteral nutrition (TPN) is usually commenced if the neonate is not likely to be fed for longer than 3 days. It is prescribed by the Medical Staff in conjunction with the Pharmacist and Clinical Nutrition team.

Standard solutions used in Butterfly Ward:

INTRAVENOUS FLUID and PARENTERAL REQUIREMENTS (mL/Kg/Day)

Butterfly TPN Guide Card (2017)

** A ‘side arm’ of 10% Glucose +/- additives may be required on days 1 – 4 of treatment with N2 and N3 to reach an appropriate total fluid intake (TFI).

GLUCOSE INTAKE

The neonatal liver normally produces 6 – 8mg/kg/min of glucose – this is the approximate basal requirement of a newborn neonate.

Glucose intake (mg/kg/min)               =              % Glucose x volume (ml/kg/day)

                                                                                                        144

                                                                OR

Glucose intake (mg/kg/min)               =              % Glucose x hourly rate

                                                                                       Weight (Kg) x 6 

** Refer to NICU Tools: Glucose Delivery Calculator for further guidance 

GASTROINTESTINAL LOSSES

Gastrointestinal losses (e.g. nasogastric, ileostomy) of more than 20 mL/kg require mL for mL replacement.

Standard Replacement Fluid:            0.9% Sodium Chloride (500 mL) + 10 mmoL Potassium Chloride

**Refer to Replacement of Neonatal Gastrointestinal Losses clinical practice guidelines

RENAL IMPAIRMENT

In neonates with renal impairment, special consideration needs to be given to fluid management. Fluid restriction will often be required as will replacement of urinary losses in the neonate with polyuria. These patients also require a strict fluid balance record, regular urea and electrolytes and frequent weighs (as often as twice daily).

** Refer to Replacement of Renal Losses in NICU clinical practice guideline

RESUSCITATION

10 – 20 mL/Kg of 0.9% normal saline given as rapidly as possible (may be repeated as necessary)

**Refer to Butterfly Neonatal BLS Algorithm Learning Package for further information

Companion Documents

• Central Venous Access Device – RCH Policy 
• Peripheral intravenous (IV) device management– RCH Nursing Guideline
• Peripheral Intravenous Cannulation (see >> Intravenous access - Peripheral) – RCH Clinical Practice Guideline

Evidence Table

The evidence table for this guideline can be viewed here. 

Please remember to read the disclaimer.

The development of this nursing guideline was coordinated by Ryan Sendall, RN Neonatal Nursing, and approved by the Nursing Clinical Effectiveness Committee. Updated October 2021.