Why is D5NS (5% dextrose in normal saline) given to a pediatric patient with leukocytosis and thrombocytosis, likely due to a hematologic malignancy?

Why D5NS is Given in Pediatric Hematologic Malignancy with Hyperleukocytosis

D5NS (5% dextrose in normal saline) is given to provide aggressive hydration for tumor lysis syndrome (TLS) prophylaxis while maintaining euglycemia in pediatric patients with suspected hematologic malignancy and extreme leukocytosis. The dextrose component prevents hypoglycemia during aggressive fluid administration, while the normal saline provides the volume needed to maintain high urine output and prevent metabolic complications.

Primary Indication: Tumor Lysis Syndrome Prevention

Aggressive hydration is the cornerstone of TLS prevention and must be initiated immediately in any pediatric patient with leukocytosis and suspected hematologic malignancy. 1

Hydration Goals and Rationale

• Hydration should ideally start at least 48 hours before tumor-specific therapy to maximize renal protection and uric acid clearance 1
• Target urine output must be maintained at 3 mL/kg/hour in children <10 kg body weight, or at least 100 mL/hour in larger children to ensure adequate renal clearance of metabolites released from lysing tumor cells 1
• The goal is to prevent hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia that result from massive tumor cell lysis, which can lead to acute kidney injury, cardiac arrhythmias, seizures, and death 1, 2

Why D5NS Specifically

• Normal saline (0.9% NaCl) provides the isotonic volume expansion needed for aggressive hydration without causing electrolyte disturbances 1
• The 5% dextrose component prevents hypoglycemia that can occur during prolonged aggressive hydration, particularly important in pediatric patients who have limited glycogen stores 3
• D5NS maintains adequate glucose delivery while avoiding the complications of pure normal saline administration in children who may not be eating adequately due to illness 4

Risk Assessment Context

A pediatric patient with WBC >70,000/mm³ combined with constitutional symptoms (like decreased appetite) and thrombocytosis represents a hematologic emergency requiring immediate intervention. 4

• This presentation raises serious concern for acute leukemia or chronic myeloid leukemia (CML), both of which carry extremely high risk for TLS 4, 3
• Extreme hyperleukocytosis (WBC >100 × 10⁹/L) increases blood viscosity and causes microvascular sludging, leading to leukostasis with potential respiratory failure, altered mental status, and other life-threatening complications 3
• High tumor burden indicated by extreme leukocytosis places the patient at high risk for TLS when cytoreduction begins, whether from chemotherapy or even spontaneously 1, 2

Complete TLS Prophylaxis Protocol

Hydration alone is insufficient—it must be combined with uric acid management:

• High-risk pediatric patients should receive rasburicase in addition to aggressive hydration for optimal TLS prophylaxis 1
• Rasburicase is preferred over allopurinol in high tumor burden cases because it provides immediate uric acid degradation rather than just preventing new formation 1, 3
• Loop diuretics (or mannitol) may be required to maintain target urine output if hydration alone is insufficient, except in cases of obstructive uropathy or hypovolemia 1

Monitoring Requirements

Comprehensive metabolic panels must be obtained to assess for TLS parameters:

• Monitor electrolytes, uric acid, LDH, potassium, and phosphate every 6-8 hours during active cytoreduction in patients with extreme hyperleukocytosis 3, 5
• Pseudohyperkalemia should be considered in patients with extreme leukocytosis and confirmed with plasma potassium in a heparinized tube analyzed immediately 3, 6
• Platelet counts tend to rapidly reflect HLH or TLS activity, with drops indicating disease flares requiring intervention adjustment 1

Critical Pitfalls to Avoid

Several common errors can compromise outcomes:

• Never delay hydration waiting for definitive diagnosis—TLS prophylaxis must begin immediately upon suspicion of hematologic malignancy with high tumor burden 1, 4
• Alkalinization is NOT recommended despite historical use, as it increases calcium phosphate precipitation and reduces xanthine solubility without improving biochemical outcomes 1
• Do not correct mild asymptomatic hypocalcemia as calcium administration increases tissue and renal precipitation of calcium phosphate 1
• Avoid pure normal saline without dextrose in pediatric patients who may develop hypoglycemia during prolonged aggressive hydration 3

Timing Considerations

The use of rasburicase allows earlier administration of chemotherapy if needed because it provides rapid uric acid degradation, though ideally hydration should still precede therapy by 48 hours when possible 1