Maintenance intravenous fluid therapy in children

INTRODUCTION — The goal of fluid therapy is to preserve the normal body water volume and its electrolyte composition:

●Maintenance fluid therapy replaces the ongoing daily losses of water and electrolytes occurring via physiologic processes (urine, sweat, respiration, and stool), which normally preserve homeostasis. Maintenance requirements vary depending on the patient's underlying clinical status and setting, especially in postoperative or hospitalized children, due to changes in their physiologic responses (eg, excess antidiuretic hormone [ADH] secretion).

●Repletion fluid therapy corrects water and acute electrolyte deficits that have accrued via illness or physiologic abnormality. Repletion returns the patient to a normal volume and electrolyte status.

Maintenance intravenous (IV) fluid therapy, including alterations in maintenance requirements, will be reviewed here. Assessment of hypovolemia and repletion therapy and management of fluid and electrolytes in neonates are discussed elsewhere. (See "Clinical assessment of hypovolemia (dehydration) in children" and "Treatment of hypovolemia (dehydration) in children in resource-abundant settings" and "Fluid and electrolyte therapy in newborns".)

COMPONENTS OF MAINTENANCE FLUID THERAPY — Maintenance therapy replaces the ongoing daily losses of water and electrolytes occurring via physiologic processes (urine, sweat, respiration, and stool), which normally preserve homeostasis. Historically, water and electrolyte requirements were initially directly derived from the caloric energy expenditures of hospitalized, normally healthy children on bed rest who were receiving intravenous (IV) fluids [1]. These data form the basis of IV maintenance fluid therapy in children that has undergone modifications based on clinical experience and observation and encompass these components:

●Water

●Electrolytes

•Cations – Typically sodium and potassium

•Anions – Usually chloride; occasionally bicarbonate, acetate, and lactate

●Dextrose

Water

Normal physiologic needs — Homeostatic control for water depends on antidiuretic hormone (ADH) release, the kidney's ability to regulate urinary water losses via its response to ADH, and water intake based on thirst (see "General principles of disorders of water balance (hyponatremia and hypernatremia) and sodium balance (hypovolemia and edema)", section on 'Regulation of water and sodium balance'). These regulatory mechanisms allow for variability in the daily water intake in healthy children without adverse effect.

Under normal physiologic conditions, combined daily insensible and sensible losses equal approximately 100 mL for every 100 kcal/kg of energy expended. This includes the minimal daily obligate urine volume of 25 mL for every 100 kcal of energy expenditure necessary to excrete the solutes generated by dietary intake and cell metabolism (table 1).

Daily caloric expenditure for healthy children varies directly with body weight, with the rate changing over several broad weight ranges.

●Weight <10 kg – 100 kcal/kg

●Weight >10 kg to 20 kg – 1000 kcal for first 10 kg of body weight plus 50 kcal/kg for any increment of weight above 10 kg

●Weight >20 kg to 80 kg – 1500 kcal for first 20 kg of body weight plus 20 kcal/kg for any increment of weight above 20 kg

●Weight >80 kg – 2700 kcal/day with adjustments made as clinically pertinent for either increased or decreased caloric needs to meet metabolic demands

Daily water needs replace insensible water losses from the respiratory tract and skin and sensible water losses in urine and stool output [2].

●Daily insensible losses (loss that is not perceived by the individual and cannot be usually measured) account for approximately 45 mL per 100 kcal of energy expended. In patients greater than 10 kg, the insensible needs are also often calculated based on body surface area at a rate of approximately 300 to 400 mL/m² per day. The insensible losses can be further delineated into skin or respiratory losses:

•Skin losses, due to evaporation from convection and conduction, account for two-thirds of the insensible losses (30 mL per 100 kcal). Infants and small children have a proportionally greater body surface area per unit of body weight than larger children and adults, resulting in a relatively higher insensible skin loss of water.

•Respiratory losses due to the warming and humidification of inspired air account for one-third of insensible losses (15 mL per 100 kcal).

●Daily sensible water losses (losses that are perceived by the senses and can be measured) account for approximately 55 mL per 100 kcal of energy expenditure. Since water loss from stool is negligible in healthy children, sensible water loss is primarily due to the daily urinary water losses required to excrete the solute load generated from typical dietary intake and cellular metabolism. This estimate is based on a few assumptions:

•A normal and age-appropriate dietary solute load and urine that is isosmotic to plasma (approximately 290 mosmol/L).

•Normal urinary concentrating mechanisms in terms of both ADH release from the pituitary and kidney response to ADH availability. Thus, maximal stimulation of ADH release accompanied by a maximal kidney concentrating response (urine osmolality of 1200 to 1400 mosmol/L) are required to excrete the daily solute load in a minimal daily obligate urine volume. Patients with a diminished ability to concentrate urine due to low release or kidney response to ADH require a larger urine volume for excretion of daily solute load. Inadequate ADH release or kidney responsiveness to ADH may result in dehydration and hypernatremia, and inappropriate (excessive) release of ADH results in free water retention and hyponatremia.

Methods for calculation — The two methods that are routinely used to prescribe parenteral fluid therapy assume that approximately 100 mL of exogenous water is needed to replace insensible and sensible losses for every 100 kcal/kg of energy expended. Both methods take into account the relationship between caloric expenditure and total body weight based on three broad weight ranges, as noted above. These calculations also assume urinary losses are isosmotic to plasma and that there is no ongoing aberrant physiologic process such as inappropriate ADH release (see 'Changes in normal maintenance needs' below). Since the normal kidney can both concentrate and dilute the urine, healthy children generally tolerate fluid volumes below or above these calculated values, but these calculations serve as a starting point to prescribe maintenance fluid volume.

One method calculates a total daily volume of water, and the other provides fluid needs based on an hourly rate.

●Method 1 – Maintenance fluid needed on an hourly basis (calculator 1):

•Weight 3 to ≤10 kg – 4 mL/kg per hour

•Weight >10 kg to ≤20 kg – 40 mL/hour for first 10 kg of body weight plus 2 mL/kg per hour for any increment of weight over 10 kg

•Weight >20 kg to ≤80 kg – 60 mL/hour for first 20 kg of body weight plus 1 mL/kg per hour for any increment of weight over 20 kg, to a maximum of 100 mL/hour (up to a maximum of 2400 mL daily)

●Method 2 – Maintenance fluid volume for a 24-hour period (calculator 2):

•Weight >3 to ≤10 kg – 100 mL/kg

•Weight >10 kg to ≤20 kg – 1000 mL for first 10 kg of body weight plus 50 mL/kg for any increment of weight over 10 kg

•Weight >20 kg to ≤80 kg – 1500 mL plus 20 mL/kg for every kg over 20 (up to a maximum of 2400 mL daily)

At body weights >65 kg, water requirements do not show the same incremental increase as with lower weights. As a result, for individuals with a body weight >65 kg, total maintenance water needs are generally capped at 2400 mL daily for each method. Infants weighing <3 kg may require lower or higher maintenance fluids, depending on their gestational and chronologic age and other medical conditions. (See "Fluid and electrolyte therapy in newborns".)

The total daily volume of water prescribed by the hourly format is a bit lower than the daily format, but the difference is almost always of no clinical significance. For example, the maintenance water needs for a 12-kg child are calculated using both methods as follows:

●Utilizing the hourly method, the maintenance needs would be 44 mL per hour or 1056 mL for 24 hours (40 mL/hour for the first 10 kg of body weight, plus 4 mL/hour for the next 2 kg [2 mL/kg per hour for each kg of body weight between 10 and 20 kg]).

●Utilizing the 24-hour method, the maintenance needs would be slightly higher at 1100 mL for 24 hours (1000 mL for the first 10 kg, plus 100 mL for the next 2 kg [50 mL/kg per day for each kg of body weight between 10 and 20 kg]).

In children who are hospitalized or who are postoperative, the risk for inappropriate (excessive) ADH release is high. As a result, a routine calculation of maintenance water volumes in hospitalized or postoperative children may predispose to hyponatremia if water or sodium replacement is not adjusted. (See 'Alterations of therapy' below.)

Electrolytes — In children, the daily sodium, chloride, and potassium requirements can be related to daily water needs as follows:

●Sodium and chloride – 2 to 3 mEq/100 mL of water per day

●Potassium – 1 to 2 mEq/100 mL of water per day

Urinary electrolyte losses account for the majority of maintenance electrolyte needs, with fewer electrolyte losses normally accompanying the typical insensible water losses in sweat and stool. As is the case with water balance, maintenance electrolyte intake may vary from day to day, depending on clinical circumstance. For example, sodium and potassium intake may need to be reduced in patients with oliguric kidney failure to prevent volume expansion and hyperkalemia; conversely, their intake may need to be increased in patients with diarrhea or burns to prevent volume depletion and hypokalemia.

Dextrose — Dextrose is generally added to maintenance fluids, especially if the child is likely to be fasting for a lengthy period of time or if there are clinical concerns for hypoglycemia. This is particularly pertinent with smaller and younger children who have higher relative glucose requirements compared with older children. Under normal circumstances, 5 to 10 percent dextrose solution administered at a maintenance rate is safe as this amount of dextrose is taken up rapidly by cells and metabolized. Therefore, dextrose remains only for a short time in the intravascular space and is not a relevant factor when considering tonicity of IV fluid, especially when compared with sodium. As a result, in this topic, references to isotonic fluid only apply to the sodium content even if the fluid contains dextrose.

Patients with type 1 diabetes mellitus who are receiving IV hydration with dextrose-containing fluids should have frequent blood glucose monitoring. Management of patients with type 1 diabetes in the settings of acute illness, medical procedures, or diabetic ketoacidosis is discussed in greater detail separately. (See "Diabetic ketoacidosis in children: Treatment and complications".)

CHANGES IN NORMAL MAINTENANCE NEEDS — Most children who are hospitalized are acutely ill, and adjustments in fluid therapy maintenance are required due to alterations of water losses or the normal homeostatic mechanisms for water balance (eg, inappropriate antidiuretic hormone [ADH] release).

Changes in water loss — The following clinical conditions can affect maintenance water needs due to changes with insensible or sensible water losses (table 2):

●Increased water needs:

•Preterm birth – Preterm infants have increased insensible water losses from the skin due to an increased surface area for mass and a thinner dermis. Water losses from the skin are also accentuated if the infant is cared for in an open radiant heater or is receiving phototherapy. (See "Fluid and electrolyte therapy in newborns".)

•Burns – Patients with burns will have increased insensible water and electrolyte losses from areas of affected skin.

•Fever – Patients with fever will also have increased insensible water losses from skin and respiratory tract.

•Gastrointestinal illness – Diarrhea will increase sensible stool fluid losses. Emesis will increase sensible water loss, and losses from a colostomy or ileostomy also will increase sensible stool water losses due to an inability to reabsorb intestinal fluid that is usually presented to more distal regions of the digestive tract.

•Sweating – Sweating due to intense exercise or exertion results in increased fluid loss from the skin.

•Polyuria – Patients with polyuria have excessive urinary water loss.

●Decreased water needs:

•Mechanical ventilation – Patients on ventilators with prehumidified air will have decreased insensible water losses, which normally occur with respiration.

•Oliguria – Patients with oliguric kidney failure will have decreased urinary water losses and thus may have little or no sensible water losses since urine output comprises almost all sensible output.

Changes in water homeostasis — Most children with an imbalance between daily water intake and losses are able to maintain overall body water balance by regulating urinary water loss via ADH and thirst mechanisms through osmoreceptors. The threshold for physiologic ADH release is approximately 280 to 290 mosmol/kg (figure 1). However, the normal physiologic osmotic release and response to ADH may be impaired in a variety of clinical settings, particularly in children who are hospitalized (table 3). (See "General principles of disorders of water balance (hyponatremia and hypernatremia) and sodium balance (hypovolemia and edema)", section on 'Regulation of water and sodium balance'.)

●Syndrome of inappropriate ADH release (SIADH) is caused by nonphysiologic increased release of ADH that commonly occurs in hospitalized children who were previously healthy. This results in diminished free water excretion and potential hypo-osmolality (hyponatremia). In particular, children who are postoperative or immobilized; have central nervous system or pulmonary disease; or have significant pain, stress, and anxiety are at risk for SIADH. In this setting of transient SIADH, initial fluid therapy consists of isotonic solution and some patients may require fluid restriction.

Although less common, there are children with chronic neurologic disorders that have a lower threshold for ADH release, referred to as "reset osmostat." (See "Hyponatremia in children: Etiology and clinical manifestations", section on 'Reset osmostat'.)

●Arginine vasopressin deficiency (AVP-D; previously called central diabetes insipidus) is caused by the lack of appropriate release of ADH resulting in polyuria and potential serum hyperosmolality (hypernatremia) due to hypovolemia. Children with central nervous system tumors or injury, congenital brain abnormalities, certain genetic disorders or syndromes, and anorexia nervosa may present with AVP-D. The clinical manifestations and management of children with AVP-D are discussed separately. (See "Arginine vasopressin deficiency (central diabetes insipidus): Etiology, clinical manifestations, and postdiagnostic evaluation" and "Arginine vasopressin deficiency (central diabetes insipidus): Treatment", section on 'Children'.)

●Arginine vasopressin resistance (AVP-R; previously called nephrogenic diabetes insipidus) is caused by impaired kidney response to ADH resulting in polyuria and hyperosmolality (hypernatremia). Pediatric causes of AVP-R include genetic mutations of the genes for the vasopressin receptor in the distal renal tubule and disorders that result in renal tubular injury. The clinical manifestations and management of AVP-R are discussed separately. (See "Arginine vasopressin resistance (nephrogenic diabetes insipidus): Clinical manifestations and causes", section on 'Causes' and "Arginine vasopressin resistance (nephrogenic diabetes insipidus): Treatment", section on 'Treatment'.)

●Nephrogenic or hereditary SIADH is extremely rare and is caused by an enhanced kidney response to ADH due to a gain-of-function mutation in the genes for the vasopressin receptor in the distal renal tubule. (See "Pathophysiology and etiology of the syndrome of inappropriate antidiuretic hormone secretion (SIADH)", section on 'Hereditary SIADH'.)

PRESCRIBING MAINTENANCE INTRAVENOUS FLUID THERAPY

Goal — Maintenance intravenous (IV; parenteral) fluid therapy is provided to hospitalized children who are not expected to be able to adequately take in enteral (oral) fluids. The goal of IV maintenance fluid therapy is to preserve water and electrolyte balance in the euvolemic patient and to avoid hypoglycemia by providing sufficient glucose (dextrose). In our practice, the general principles outlined in the following sections are used when prescribing maintenance IV fluid therapy for children. These principles are in agreement with the practice guidelines of the National Institute for Health and Care Excellence and the 2018 American Academy of Pediatrics (AAP) clinical practice guidelines [3,4].

Composition of initial fluid

Isotonic solutions — For most pediatric patients, the preferred initial fluid is an isotonic solution (normal saline or lactated Ringer's solution), consistent with clinical practice guidelines published by the AAP [4]. This represents a shift away from the historical use of hypotonic solutions [5]. This change is based on the increasing awareness and evidence demonstrating the increased risk of hyponatremia with the use of hypotonic solution because hospitalized children are commonly at risk for inappropriate antidiuretic hormone (ADH) release, resulting in free water retention (table 3) [4,6-13]. (See 'Evidence' below and "Hyponatremia in children: Etiology and clinical manifestations", section on 'Hypotonic hyponatremia'.)

Exceptions — The AAP guidelines do not apply to subsets of children who were not included in the prospective studies that support the recommendation of isotonic solution as the preferred initial choice for maintenance IV fluid therapy. These include individuals with neurosurgical disorders, congenital or acquired cardiac disease, hepatic disease, cancer, kidney dysfunction, diabetes insipidus, voluminous watery diarrhea, or severe burns; neonates who are younger than 28 days old or in the neonatal intensive care unit; or adolescents older than 18 years of age [4].

In addition, children with excessive water loss may require a hypotonic solution for maintenance therapy. These include children with polyuria due to renal concentrating defects (eg, arginine vasopressin resistance [AVP-R]) or inability to release ADH (arginine vasopressin deficiency [AVP-D]) and those with nonrenal causes of abnormally large ongoing water loss (individual with severe burns or severe watery diarrhea). For these patients who require free water to replace their losses, the use of isotonic solutions may result in hypertonicity. (See 'Changes in water homeostasis' above and "Hypernatremia in children", section on 'Excess water losses'.)

Potassium — In children with normal serum potassium levels and kidney function, potassium chloride is usually added to maintenance fluids at a concentration of 10 mEq/L for small children with weights <10 kg and, for larger children with weights ≥10 kg, a concentration of 10 to 20 mEq/L is provided. This will generally ensure the provision of maintenance potassium needed to prevent evolving hypokalemia over time.

In children who are considered potassium replete and for whom the duration of IV fluid administration will be brief prior to allowing intake of potassium-containing fluids or solids, potassium-free fluids can be considered. However, if there is a delay in restarting oral intake, fluid therapy should be changed. Children with abnormal potassium levels or impaired kidney function require more individualized potassium prescription. (See "Management of hyperkalemia in children" and "Hypokalemia in children", section on 'Management'.)

Dextrose — Dextrose is typically added as a 5 percent solution to provide sufficient glucose to avoid hypoglycemia while IV fluids are administered. The dextrose concentration can be increased to 10 percent for patients who develop hypoglycemia or are at risk for hypoglycemia (eg, infants) or for additional caloric intake for patients in whom there is an expectation of prolonged IV fluid therapy.

Evidence — The data supporting isotonic solutions include several meta-analyses based on small clinical trials [6-8,12]. A subsequent trial of fluid maintenance in 690 hospitalized children also reported that patients treated with isotonic solutions were less likely to develop hyponatremia than children who received a hypotonic solution containing 77 mEq/L of sodium (4 versus 11 percent; odds ratio 0.31, 95% CI 0.16-0.61) [9].

Support for fluid therapy containing at least 10 mEq/L of potassium is based on a clinical trial of 614 acutely ill children cared for in the emergency department setting who required hospitalization that reported a higher rate of electrolyte abnormalities associated with a commercially available isotonic solution (140 mEq/L of sodium and 5 mEq/L of potassium in 5 percent dextrose) compared with a hypotonic solution (80 mmol/L sodium and 20 mmol/L potassium in 5 percent dextrose) [14]. In this cohort, the most frequent disorder was hypokalemia, defined as a serum potassium <3.5 mEq/L (19 versus 2.9 percent; relative risk [RR] 6.3, 95% CI 3.2-12), followed by hypernatremia, defined as a serum sodium >148 mEq/L (1.3 versus 0 percent; RR 0.6, 95% CI 0.3-1.6). There were no reports of hyponatremia. These results highlight the need for adequate potassium supplementation but also, in contrast with the above data, question the safety of isotonic versus hypotonic solution.

Rate of initial fluid therapy — The initial rate of fluid therapy is based on the usual daily energy expenditure of the child, which varies with body weight (table 1). Two calculators are typically used in determining the initial rate of IV maintenance fluid therapy (calculator 2). (See 'Methods for calculation' above.)

In the majority of hospitalized children with acute medical or surgical conditions, the initial use of isotonic saline at a maintenance rate reduces the risk of hyponatremia and hypovolemia [11]. Despite the observation that many hospitalized children have transient inappropriate ADH release, assessment for inappropriate ADH release is not typically performed. As a result, the traditional approach of fluid restriction is usually not initiated and appears not to be needed to maintain serum sodium levels in most children with acute illnesses or postoperative children who are expected to fully recover in a timely manner [11]. Nevertheless, ongoing assessment is needed to determine whether the rate of therapy requires modification as discussed below.

In determining a child's full daily volume, all sources of fluid intake need to be considered, including parenteral medications and blood products and oral intake for children who are able to eat and drink. In these settings, the volume and rate of IV fluid administration must be adjusted to account for these alternate sources of fluids.

Alterations of therapy — The initial assumptions of the appropriateness of initial fluid therapy need to be confirmed as clinical conditions may alter water loss (table 2). In some cases, this may be due to impaired release of ADH and kidney response to ADH (table 3). Management is altered when the initial therapy does not maintain a stable euvolemic state based on ongoing assessment that monitors volume status (ie, net fluid balance and changes in body weight and serum sodium). (See 'Monitoring' below.)

●Euvolemia – The appropriateness of the choice of initial therapy (isotonic solution and initial maintenance rate) is confirmed for the stable euvolemic patient. These patients have no change in serum sodium or body weight and have a neutral net volume balance. No modification of therapy is needed if these parameters remain stable and the child continues to require maintenance IV fluid.

●Hypovolemia – Children with unreplaced increased water losses (eg, watery diarrhea) leading to volume depletion (hypovolemia) present with an increase in serum sodium, negative net volume balance, and decrease in body weight. For these patients, alterations based on the clinical setting include change from isotonic to hypotonic solution and/or increase in the rate of therapy, resulting in the administration of more water. Initially unanticipated water losses may be seen in patients with fever, watery diarrhea, and burns, as well as those with significant drainage from nasogastric tube.

●Hypervolemia – Children with a decrease in water loss (eg, syndrome of inappropriate secretion of ADH [SIADH] resulting in decrease urinary volume) leading to water retention (hypervolemia) present with a decrease in serum sodium, positive net volume balance, and increase in body weight. For these patients, isotonic solution is continued at a decreased rate (fluid restriction). Water retention may be observed in children with SIADH, significant renal impairment, heart failure, cirrhosis, and nephrotic syndrome.

Monitoring — As mentioned above, assessment of fluid therapy is based on monitoring the child's volume status that includes ongoing evaluation of changes in serum sodium and body weight, as well as assessing net fluid balance. The frequency of assessment is based on the severity of illness, vulnerability of the child to fluid fluctuations, and need to alter fluid therapy.

●Serial sodium measurements assess the changes in free water. Increases in serum sodium represent decreases in total body water and a need to replace water losses, whereas decreases in serum sodium represent water retention and a need for fluid restriction. Serum sodium is typically obtained initially and between 6 to 12 hours after the initiation of IV fluid therapy [4]. The frequency of subsequent measurements depends on whether there are ongoing changes in fluid therapy based on unanticipated changes to water losses, and the severity of illness. For patients who are critically ill with ongoing changes, serial sodium may be obtained as frequently as every four to six hours. In contrast, serum sodium may be obtained daily for patients who are stable on IV fluid therapy.

●To maintain euvolemia, this net difference reflects the volume of insensible fluid loss resulting in no change in fluid balance (neutral net fluid balance) and no change in weight. For patients who are cared for in a critical care setting, assessment of the net fluid balance may be as frequent as three times a day. For less ill patients, assessment may be made on a daily basis.

●Initial weights on admission and then daily for the first 48 hours can complement clinical assessment of volume changes. Acute increases in body weight are indicative of water retention, whereas decreases suggest loss of free water that has not been adequately replaced. Ongoing daily body weights are usually obtained for hospitalized patients who remain on IV fluid therapy for a more extensive period of time (greater than 48 hours).

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Fluid and electrolyte disorders in children".)

SUMMARY AND RECOMMENDATIONS

●Definition and homeostasis ‒ Maintenance fluid therapy replaces the ongoing losses of water and electrolytes occurring via normal physiologic processes with a goal of preserving water and electrolyte balance in the euvolemic patient. Homeostatic control for water is dependent on antidiuretic hormone (ADH) release, the kidney's ability to regulate urinary water losses via its response to ADH, and water intake based on thirst. (See 'Components of maintenance fluid therapy' above and 'Normal physiologic needs' above.)

●Components ‒ Components of maintenance fluid therapy are water, electrolytes, and dextrose. (See 'Components of maintenance fluid therapy' above.)

•Normal water requirements are estimated in direct relation to caloric energy expenditures, which vary directly with body weight. Daily water needs replace insensible water losses from the respiratory tract and skin and sensible water losses in urine and stool output.

In children, specific water requirements change over three broad weight ranges. Two methods based on the child's weight are generally used by clinicians to calculate maintenance water (calculator 2). (See 'Methods for calculation' above.)

•Electrolyte maintenance is also based on caloric energy expenditures and includes sodium and chloride requirements of 2 to 3 mEq/100 mL of water and potassium requirements of 1 to 2 mEq/100 mL of water. (See 'Electrolytes' above.)

•Dextrose is added usually as a 5 percent solution to avoid hypoglycemia in children who are likely to be fasting for a lengthy period of time. (See 'Dextrose' above.)

●Hospitalized children ‒ Most children who are hospitalized are acutely ill, and adjustments in fluid therapy maintenance are required due to alterations of water losses (table 2) or the normal homeostatic mechanisms for water balance (eg, inappropriate release of ADH) (table 3). (See 'Changes in normal maintenance needs' above.)

●Prescribing maintenance fluid ‒ The management of maintenance fluid therapy in children include the following and are consistent with the practice guidelines of the National Institute for Health and Care Excellence and the American Academy of Pediatrics (AAP):

•Choice of initial fluid – For most hospitalized children, we recommend the initial use of isotonic fluid (eg, normal saline or lactated Ringer's) as maintenance fluid therapy (Grade 1B). The risk of hyponatremia is increased with the use of hypotonic solution because increased ADH release is a common occurrence in hospitalized children (table 3). (See 'Isotonic solutions' above.)

-Exceptions – Exceptions to the use of isotonic solutions as initial fluid therapy include groups who were not included in the studies, including infants in a neonatal intensive care unit. Other exceptions are children with polyuria due to renal concentrating defects (eg, arginine vasopressin resistance [AVP-R]) or inability to release ADH (arginine vasopressin deficiency [AVP-D]) and those with nonrenal causes of abnormally large ongoing water loss (individual with severe burns or severe watery diarrhea). In these patients, a hypotonic solution may be more appropriate to replace excess water loss. (See 'Exceptions' above.)

-Potassium – In children with normal serum potassium levels and normal renal function, potassium chloride is usually added to maintenance fluids at a concentration of 10 mEq/L for small children with weights <10 kg and, for larger children with weights ≥10 kg, a concentration of 10 to 20 mEq/L. (See 'Potassium' above.)

-Dextrose – Dextrose is typically added as a 5 percent solution to provide sufficient glucose to avoid hypoglycemia while intravenous [IV] fluids are administered. (See 'Dextrose' above.)

•Infusion rate ‒ The initial rate of fluid therapy is calculated based on the weight of the child (table 1) (calculator 2). (See 'Methods for calculation' above.)

•Subsequent adjustments ‒ The rate and tonicity of therapy are readjusted as needed based on ongoing and frequent clinical assessment of the child's fluid and electrolyte status. Management is altered when the initial therapy does not maintain a stable euvolemic state, based on ongoing assessment that monitors net volume balance and changes in body weight and serum sodium (measure of tonicity). (See 'Alterations of therapy' above and 'Monitoring' above.)

-Euvolemia – No change in therapy is required for patients who remain euvolemic, as manifested by stable serum sodium, net neutral fluid balance, and no change in weight.

-Hypovolemia – Changes that increase free water delivery are needed for children who are volume depleted due to unreplaced water losses resulting in an increase in serum sodium, negative net fluid balance, and decrease in body weight.

-Hypervolemia – Rate of fluid therapy is decreased (fluid restriction) for children with evidence of water retention with a lower serum sodium, positive net fluid balance, and increase in body weight.