Management of Electrolytes

The management of fluid and electrolyte imbalances is a crucial aspect of caring for pediatric oncology patients. While certain issues are unique to patients with malignancies, their treatment adheres to the general principles of paediatrics.

Causes of electrolyte imbalance

Pediatric oncology patients are at high risk of developing fluid balance abnormalities:

• During hyper-hydration given as part of standard chemotherapy regimens.
• During induction chemotherapy for acute leukemia, where hyper-hydration is essential for the prevention of acute tumour lysis syndrome.
• As part of treatment of tumour lysis syndrome.
• Following nephrotoxic chemotherapy (e.g. cisplatin, ifosfamide), which may cause a renal tubular leak, resulting in renal loss of electrolytes, particularly sodium, potassium, magnesium and phosphate.
• As a result of chemotherapy causing vomiting, diarrhea or mucositis, leading to dehydration, hypokalemia, hypo- or hypernatremia, or hypomagnesaemia.
• In post-stem cell transplant patients with gastrointestinal graft-vs-host disease, where fluid and electrolyte loss from the gut may be severe and prolonged.
• In septic shock where profound hypotension requires significant fluid resuscitation.
• In febrile patients, in whom insensible fluid losses may be increased.
• In patients with central diabetes insipidus e.g. as a result of a brain tumour (especially craniopharyngioma) or Langerhans Cell Histiocytosis.
• In patients with veno-occlusive disease (VOD) of the liver, most common after stem cell transplant using busulphan-containing conditioning regimens.
• In patients with disseminated malignancy who are at risk of hypercalcemia.
• Some drugs can cause a syndrome of anti-diuretic hormone secretion (SIADH), with hyponatremia, e.g. vincristine, carbamazepine.

Hyponatremia

Definition

Na < 135mmol/l (mild 130-134mmol/l; moderate 127-129mmol/l; severe < 126mmol/l)

Clinical features

Asymptomatic in mild and sometimes moderate cases; nausea, lethargy, headache, altered level of consciousness, seizures.

Causes

Management

Hypernatremia

Definition

Na >145 mmol/l (and usually not symptomatic/problematic >150 mmol/l).

Clinical features

Symptoms and signs of dehydration; altered level of consciousness, seizures.

Causes

Usually due to water loss rather than sodium excess:

• Diarrhoea
• High insensible fluid losses
• Water deprivation
• Diabetes insipidus (central or nephrogenic), omission of desmopressin (DDAVP)
• Obstructive uropathy
• Excess sodium administration / iatrogenic

Management

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