Hypernatremia

Abstract

Hypernatremia is biochemically defined by a blood sodium concentration ([Na+]) above the normal reference range for the laboratory performing the test (typically >145 mmol/L). The clinical relevance of an above normal blood [Na+] is largely determined by the severity of the clinical signs and symptoms associated with cellular shrinkage (crenation). High blood sodium concentrations are largely caused by: 1) excessive water loss with inadequate fluid replacement (thirsting); 2) excessive salt ingestion; or a likely combination of too little fluid with too much salt. Morbidity and mortality from hypernatremia has been documented in infants accidentally poisoned with salt or having difficulties breastfeeding, children ingesting excessive amounts of salt as an emetic or punishment, mentally or physically disabled individuals (often living in nursing homes) who cannot express thirst or have free access to fluids, athletes who refrain from drinking during heavy exercise in hot conditions, and hospitalized patients with under-replaced fluid or over-replaced sodium administration. Poor clinical outcomes and delayed recovery have been documented in hospitalized patients with hypernatremia, compared with patients who are admitted and remain normonatremic throughout their hospital stay. Clinically significant hypernatremia in free living humans is extremely rare, with “salt poisoning” often an indicator of abuse, neglect, or mental illness. Thus, the secret stories of hypernatremia often whisper tales of suicide from soy sauce, death by exorcism and salting rituals, extreme parental punishment, hunger strikes, getting lost in the sea or desert, and mass accidental poisonings whereas salt is mistaken for sugar. ABBREVIATIONS: [Na+] – sodium concentration, ICP – intracranial pressure, ICU – intensive care unit, TBI - traumatic brain injury