A client's serum sodium is 128 mEq/L (normal 135-145). They appear confused and report nausea and headache. What condition does this represent and what is the nursing priority?

HYPONATRAEMIA (Na <135 mEq/L): SEVERE (<125 mEq/L): Neurological symptoms — confusion, nausea, headache, seizures, and if untreated, cerebral oedema, herniation, and death; 128 mEq/L with symptoms = URGENT;

Causes: SIADH (syndrome of inappropriate ADH secretion); heart failure; cirrhosis; excessive hypotonic IV fluids; psychogenic polydipsia.

Critical nursing action: Do NOT give free water or hypotonic fluids (water moves into cells and worsens cerebral oedema); Notify RN immediately; seizure precautions; TREATMENT (physician-ordered): Fluid restriction (most common); hypertonic saline (3% NaCl) for severe symptomatic cases — given only in ICU with strict monitoring; rate of correction must be controlled (correcting too fast causes osmotic demyelination syndrome).

Monitoring: Neurological status (confusion, seizure activity); vital signs; serum sodium levels; strict I&O; safety measures (fall precautions for confusion).