Advanced Approaches to Pediatric Fluid and Electrolyte Therapy: What Pharmacists Need to Know

Fluid and electrolyte therapy is an essential component of pediatric patient care. A multitude of factors contribute to the fluid and electrolyte needs of a pediatric patient throughout infancy, childhood, and adolescence. Meeting these needs requires a systematic approach that includes the important role of a pediatric pharmacist. Recognizing subcategories of fluid requirements while monitoring electrolyte status is a crucial part of managing pediatric patients across various health care settings.

Fluid therapy is divided into 3 categories: maintenance, deficit, and replacement. Maintenance fluids are indicated for the compensation of ongoing sensible or insensible losses, whereas deficit and replacement fluids are given to compensate for prior or ongoing losses, respectively.¹

Fluid Therapy

Maintenance

Maintenance fluids comprise 3 components. The first is a base solution given to compensate for normal, daily losses, as well as fluid loss that is difficult to measure. The second component is dextrose (typically dextrose 5% in water [D5W]), the primary source of calories. It is often added to the base solution (hypotonic or isotonic) to meet the patient’s caloric needs. The third component is electrolytes.

Most fluid loss occurs in urine and stool, but that is not all-inclusive of the pathways in which fluid can be lost. Insensible fluid loss is the amount of body fluid lost daily that is not easily measured, from the respiratory system, skin, and water in the excreted stool. Children have much higher fluid requirements due to a higher metabolic rate, a higher body surface area (BSA) to weight ratio, and a higher respiratory rate than adults. Maintenance intravenous (IV) fluids are required if sufficient fluid intake cannot be provided via the enteral route to meet the metabolic needs. Some reasons for excessive loss are gastrointestinal illness, perioperative setting (drains, blood loss, etc.), respiratory compromise, or neurologic impairment.¹

Historically, the choice of maintenance fluid has been a hypotonic fluid (eg, D5W, one-fourth normal saline [NS], or D5W one-half NS), which was based solely on theoretical grounds and not on evidence from clinical trials. This approach has resulted in a high incidence of hyponatremia in the acute care setting, prompting a switch to isotonic fluids (eg, NS, D5W, Lactated Ringer [LR], Plasma-Lyte). In patients who received isotonic fluid for maintenance IV hydration, compared with those who received hypotonic fluid, there was a substantially lower risk of hyponatremia.^1,2 The American Academy of Pediatrics (AAP) issued a statement in 2018 recommending that “Patients 28 days to 18 years of age requiring maintenance IV fluids should receive isotonic solutions with appropriate potassium chloride and dextrose because they significantly decrease the risk of developing hyponatremia.”¹ As a result of this statement, the preferred maintenance fluid is isotonic (ie, D5W NS) with the addition of potassium as appropriate. Table 1 lists the composition of commonly used maintenance IV fluids.¹

The foundation for the modern concept of maintenance fluid calculations emerged from the work of Holliday and Segar, who found that daily fluid requirements and losses, derived from energy consumption, urine production, and insensible losses, are directly correlated with caloric needs.³ As shown in Table 2,⁴ maintenance fluid calculations are still performed using the Holliday-Segar method, assuming that 100 kcal expended requires 100 mL of water.

Additionally, an alternative method for calculating maintenance fluids in pediatric patients is available. This calculation is based on the energy expenditure of children, assuming a child needs 1 mL of fluid for each kcal expended, or 1500 mL/m² per day. For example, for a child with a BSA of 0.8 m², their daily fluid requirement would be 1200 mL/day (0.8 m² x 1500 mL/m²/day).

Dehydration and Replacement

Dehydration is a condition caused by excessive loss of total body water, often leading to an imbalance in fluid and electrolyte levels. The most common cause of dehydration in pediatric patients is loss of fluids due to diarrhea and vomiting, commonly associated with gastrointestinal illnesses.⁵ Causes of dehydration in patients with cancer include drainage from wound or surgical sites, vomiting, diarrhea, and decreased fluid intake due to nausea, mucositis, or changes in appetite. Recognizing the symptoms and identifying the degree of dehydration is key to determining the route and amount of fluid replacement. As shown in Figure 1,⁴ the degree of dehydration can be calculated and serves as the first step in the process of repletion. Table 3^4,6 categorizes mild, moderate, and severe dehydration based on clinical signs upon patient presentation. 

The AAP recommends oral rehydration therapy (ORT) as the preferred treatment of fluid and electrolyte losses caused by diarrhea in children with mild to moderate dehydration.^4,7 Although oral rehydration is safe and effective, there are contraindications, including altered mental status with risk of aspiration, abdominal ileus, and underlying intestinal malabsorption.⁷ In these cases, IV hydration should be initiated.

Dosing of ORT

In those with mild dehydration, replacement dosing is 50 mL/kg of an oral rehydration solution (ORS), administered over 4 hours. For those with moderate dehydration, replacement dosing is 100 mL/kg of ORS, administered over 4 hours. Table 4 outlines the compositions of ORS and common beverages.

Severe dehydration requires rapid IV fluid repletion, with the goal of rehydration within 24 hours. The rehydration process is divided into 3 phases: rapid phase, replacement phase, and stabilization phase.^1,4,8 Phase 1, the rapid phase, is meant to restore circulation and consists of an IV bolus of 10 mL/kg to 20 mL/kg of an isotonic fluid such as NS over 30 to 60 minutes. This bolus can be repeated as needed in severe scenarios (ie, hypovolemic shock).

Phase 2, the replacement phase, aims to correct the fluid and electrolyte deficit. The amount administered in this phase should equal one-third of the daily maintenance dose plus one-half of the deficit over 8 hours. The choice of fluid in this phase is D5NS, with the addition of 20 mEq/L to 30 mEq/L of potassium chloride if the patient has voided and proved that the potassium added to the fluids can be excreted.^1,8

Phase 3, the stabilization phase, is the transition to maintenance fluids. This phase lasts over 16 hours and consists of two-thirds of daily maintenance fluids plus the remaining deficit, with fluids continued into the replacement phase.

The Pharmacist’s Role in Maintaining Euvolemia

Maintaining euvolemia in pediatric patients is crucial for ensuring optimal physiological function, supporting organ perfusion, and preventing complications such as dehydration or fluid overload. Monitoring the volume of IV compounded medications and the frequency of administration, recommending appropriate IV fluids, and understanding the pharmacokinetic parameters to adjust medication dosages based on fluid status are where pharmacists play a significant role in preventing overhydration or overt shifts in electrolytes.⁴

Electrolyte Management

Maintenance Electrolytes

Under normal physiological conditions, the kidneys regulate circulating volume and maintain electrolyte balance by adjusting the excretion of water and solutes. Recognizing a patient’s clinical status, particularly renal function, is an important step in assessing electrolyte requirements in children. Electrolyte replacement in maintenance IV fluids typically consists of sodium, potassium, and chloride. The sodium and chloride requirements range from 2 to 3 mEq per 100 mL of water per day, while potassium requirements range from 1 to 2 mEq per 100 mL of water per day. Children who weigh less than 10 kg with normal serum potassium levels and kidney function should receive 10 mEq/L of potassium, while children who weigh more than 10 kg should receive between 10 and 20 mEq/L.⁹

Replacement electrolyte therapy addresses disturbances resulting from conditions such as vomiting, diarrhea, or dehydration. General considerations for electrolyte replacement are the severity of the laboratory value and presence of symptoms, suspected cause of the electrolyte imbalance (ie, excess or inadequate intake, IV fluids, medications), and what sources of electrolytes the patient is receiving (ie, dietary intake, supplemental and medication effects).^4,7

Potassium

Potassium is an intracellular ion that establishes the resting membrane potential as an essential part of the sodium/potassium adenosine triphosphatase (ATPase) pump. The therapeutic range is 3.8 to 5.2 mEq/L. Both hypokalemia and hyperkalemia can cause cardiac arrhythmias, but hypokalemia results in weakness, fatigue, and muscle twitching, whereas hyperkalemia is associated with tachycardia and muscle weakness.¹⁰ IV or oral repletion depends on the degree of electrolyte abnormality. If the potassium level is less than 3 mEq/L or symptomatic, IV repletion should take place. Mild hypokalemia (>3 mEq/L) should be corrected orally. Potassium levels should be checked 1 hour after IV repletion and approximately 2 to 6 hours after oral repletion. When replenishing potassium for acute changes, potassium levels should be monitored prior to repeat doses. Table 5 reviews dosing and administration for potassium supplementation.

Magnesium

Magnesium (Mg) is an intracellular cation involved in protein synthesis, neurotransmitter release, and muscle/nerve function. The therapeutic range is 1.5 to 2.3 mg/dL. Hypomagnesemia is characterized by hyperirritability, tremors, cardiac dysrhythmias (torsades), and spasticity.¹⁰ Hypermagnesemia is characterized by lethargy, weakness, bradycardia/hypotension, and QT prolongation. If the magnesium level is less than 1 mg/dL and symptomatic, IV repletion should take place. Magnesium salts differ in the amount of elemental content per mg (range, 54-603 mg magnesium per 1 g salt). Monitor magnesium levels for at least 24 hours after IV or oral repletion due to incomplete tissue distribution before 36 to 48 hours after the repletion dose. Table 6 outlines dosing and administration for magnesium supplementation.

Phosphorus

Phosphorus is an extracellular cation that plays a role in metabolic pathways. The therapeutic range is 2.5 mg/dL to 4.5 mg/dL. Hypophosphatemia is characterized by seizures, altered mental status, and muscle/nerve dysfunction. Hyperphosphatemia is characterized by calcification, prolonged QT, and muscle cramping.¹⁰ If patients are symptomatic with moderate (1-2 mg/dL) or severe
(< 1 mg/dL) hypophosphatemia, IV repletion should be initiated. Phosphorus levels should be monitored 6 to 12 hours after IV or oral repletion. Table 7 reviews dosing and administration guidelines for phosphorus supplementation.

When selecting an agent for repletion, it is imperative to consider other electrolyte levels, such as potassium, in the body. With IV repletion, if the potassium level is greater than 4 mEq/L, sodium phosphate might be the preferred agent, whereas if the potassium level is less than 4 mEq/L, potassium phosphate would be the agent of choice. In oral repletion, if a patient is hyperkalemic or has impaired renal function, consider sodium phosphate or K-Phos Neutral for less potassium content. Refer to Table 8 for electrolyte content of available products.

Calcium

Calcium is an extracellular cation that is essential in the contraction of muscles, bone growth, and the transmission of nerve impulses. The therapeutic range is 8.8 to 10.4 mg/dL. Hypercalcemia is characterized by muscle weakness, shortened QT interval, and hypertension, while hypocalcemia is characterized by muscle cramps, QT prolongation, and seizures. IV repletion is recommended for severe or symptomatic hypocalcemia. Calcium levels can be checked every 4 to 8 hours for IV repletion and daily or as needed for oral repletion.¹⁰ Table 9 outlines dosing and administration guidelines for calcium supplementation.

Conclusion

The approach to fluid therapy is systematic, highlighting the distinction between maintenance, deficit, and replacement requirements. Pediatric pharmacists play an important role in identifying the appropriate fluid, understanding the pharmacokinetics of commonly used medications that can be affected by a shift in volume status, and providing sound recommendations for electrolyte replacement based on lab values. Applying knowledge of fluid composition and the rationale behind electrolyte formulation and dosing based on the degree of derangement helps create an individualized approach for each patient.  

References

1. Feld LG, Neuspiel DR, Foster BA, et al; Subcommittee on fluid and Electrolyte Therapy. Clinical practice guideline: maintenance intravenous fluids in children. Pediatrics. 2018;142(6):e20183083. doi:10.1542/peds.2018-3083

2. McNab S, Ware RS, Neville KA, et al. Isotonic versus hypotonic solutions for maintenance intravenous fluid administration in children. Cochrane Database Syst Rev. 2014;2014(12):CD009457. doi:10.1002/14651858.CD009457.pub2

3. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832. doi:10.1542/peds.19.5.823

4. Meyers RS. Pediatric fluid and electrolyte therapy. J Pediatr Pharmacol Ther. 2009;14(4):204-211. doi:10.5863/1551-6776-14.4.204

5. Mahajan P, Mclerny TK, Adam H, et al. Dehydration. In: McInerny TK, Adam HM, Campbell DE, DeWitt TG, Meschan Foy J, Kamat DM, eds. American Academy of Pediatrics Textbook of Pediatric Care. 2nd ed. American Academy of Pediatrics; 2016.

6. Practice parameter: the management of acute gastroenteritis in young children: American Academy of Pediatrics, Provisional Committee on Quality Improvement, Subcommittee on Acute Gastroenteritis. Pediatrics. 1996;97(3):424-435. Accessed February 23, 2026. https://pubmed.ncbi.nlm.nih.gov/8604285/

7. Canavan A, Arant BS Jr. Diagnosis and management of dehydration in children. Am Fam Physician. 2009;80(7):692-696.

8. Jospe N, Forbes G. Fluids and electrolytes—clinical aspects. Pediatr Rev. 1996;17(11):395-404. doi:10.1542/pir.17-11-395

9. Lehtiranta S, Honkila M, Kallio M, et al. Risk of electrolyte disorders in acutely ill children receiving commercially available plasmalike isotonic fluids: a randomized clinical trial. JAMA Pediatr. 2021;175(1):28-35. doi:10.1001/jamapediatrics.2020.3383

10. Blackmer AB. Fluids and electrolytes. In: PedSAP 2018 Book 2, Fluids, Electrolytes, and Nutrition. ACCP; 2018:7-25.