Plain D5W or Hypotonic Saline Solutions Post-op Could Result in Acute Hyponatremia and Death in Healthy Children

ISMP Medication Safety Alert 

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Hyponatremia and Water Intoxication

Hyponatremia is the most common electrolyte disorder,[15] particularly among hospitalized patients. Studies suggest that more than 4% of post-op patients develop clinically significant hyponatremia within 1 week of surgery, as do 30% of patients treated in intensive care units (ICUs).[15,16,17,18] In general, the causes of hyponatremia are varied, ranging from certain medications (e.g., diuretics, heparin, opiates, desmopressin, proton pump inhibitors) and disease states (e.g., renal and liver impairment, hypothyroidism or cortisol deficiency) to outpatient environmental conditions (e.g., prolonged exercise in a hot environment) and self-imposed conditions (e.g., psychogenic polydipsia, feeding infants tap water or formula that is too dilute). However, the causes of hospital-acquired hyponatremia most relevant to the events described above are twofold: administration of plain D5W or hypotonic saline parenteral solutions post-op, and failure to recognize the compromised ability of children to maintain water balance.[15]

Review of the literature suggests that administration of hypotonic saline or parenteral fluids without saline is physiologically unsound and potentially dangerous for hospitalized children.[1] A 2003 analysis[1] found more than 50 reported cases of neurologic morbidity and mortality, including 26 deaths, during a 10-year period resulting from hospital-acquired hyponatremia in children who were receiving hypotonic saline parenteral fluids.[1,2,3,4,5,6,7,8,9,10,11,12,13,14] More than half of these cases occurred in the postoperative setting in previously healthy children who underwent minor surgeries. Children are particularly vulnerable to water intoxication because they are prone to developing a syndrome of inappropriate antidiuretic hormone (SIADH).[1] Common childhood conditions requiring IV fluids, such as pulmonary and central nervous system infections, dehydration, and the postoperative state, are associated with a nonosmotic—and therefore inappropriate—stimulus for antidiuretic hormone (ADH) production.[1,14] The postoperative nonosmotic stimulus for ADH release typically resolves by the third postoperative day but can last until the fifth postoperative day.[1,18] Pain, nausea, stress, opiates, inhaled anesthetics, and the administration of hypotonic saline or solutions without saline also stimulate the excessive release of ADH in children.[1,14]

Children are also more vulnerable to the effects of cerebral swelling due to hyponatremia because they develop encephalopathy at less significant decreases in normal serum sodium levels than adults and have a poor prognosis if timely therapy is not instituted. In children, there is little room for brain expansion due to a higher brain-to-skull size ratio.[1,17,19] Children achieve adult brain size by 6 years of age, whereas full skull size is not achieved until 16 years of age.

Hyponatremic encephalopathy can be difficult to recognize in children, as the symptoms may be variable.[2,18] The most consistent symptoms include headache, nausea, vomiting, weakness, mental confusion, and lethargy. Advanced symptoms show signs of cerebral herniation, including seizures, respiratory arrest, noncardiogenic pulmonary edema, dilated pupils, and decorticate or decerebrate posturing.[1]

Irreparable harm can happen when low serum sodium levels are corrected too quickly or too slowly. Once the source of free water has been eliminated, the sodium level is typically increased by 4-6 mEq over the first 1-2 hours using an isotonic or near isotonic sodium chloride infusate.[15] Patients with seizures, severe confusion, coma, or signs of brainstem herniation may need hypertonic (3%) saline to correct sodium levels, but only enough to arrest the progression of symptoms. Formulas exist for determining the dose of hypertonic saline during replacement therapy.[14] Some clinicians believe that, in serious cases, treatment of hyponatremia should be rapid since the risk of treating too slowly—cerebral herniation—is felt to be greater than the risk of treating too quickly—osmotic demyelination syndrome, which has been associated with lesions in the white matter of the brainstem.[14] These lesions are more common in adults. ( Please note: The preceding information is in no way sufficient to guide the treatment of hyponatremia or suggested as an evidence-based standard of care. It was provided only to convey that expert opinions vary regarding prevention and treatment of hyponatremia and to encourage discussion among an interdisciplinary clinical team charged with developing electrolyte replacement protocols.)

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