title: Pseudohypernatremia secondary to trisodium citrate (Citra-LockTM).
abstract: BACKGROUND
  Hypernatremia is common among hospitalized patients especially in the intensive care units and presents an independent risk factor for mortality. Mild hypernatremia is often asymptomatic but severe hypernatremia causes central nervous system dysfunction with initial non-specific symptoms of encephalopathy that may progress to seizures, coma and death, if left untreated. Severe hypernatremia is a medical emergency and requires emergent medical attention.
  
  
  METHODS
  A haemodialysis patient who arrived for his scheduled haemodialysis treatment had monthly blood work drawn and was reported to have severe hypernatremia with serum sodium concentration of 183 mmol/L. The possibility of technique or laboratory error was considered and systematically evaluated.
  
  
  RESULTS
  The serum sodium measurement using another analyser showed similar value of 182 mmolL. A repeat serum sodium level on a sample drawn 2 h later showed normal value of 139-140 mmol/L. A step-wise evaluation of the complete procedure from blood collection to analysis of the sample revealed this to be spuriously elevated serum sodium concentration secondary to contamination of the sample during sample collection with trisodium citrate, a catheter-lock solution, commonly used in dialysis units to maintain patency of dialysis catheters.
  
  
  CONCLUSIONS
  Spuriously elevated plasma sodium concentration (pseudohypernatremia) of mild degree is common but severe pseudohypernatremia is rare and the possibility of sample contaminations or laboratory error should be considered. Vigilance is required by both the medical and the laboratory staff to resolve such issues in a timely fashion to avoid unintended consequences.
authors.affiliation: Timmins and District Hospital.
authors.forename: Janice
authors.initials: J
authors.lastname: Milliere
authors.affiliation: Timmins and District Hospital.
authors.forename: Daryl
authors.initials: D
authors.lastname: Corriveau
authors.affiliation: Timmins and District Hospital; Northern Ontario Medical School of Medicine.
authors.forename: Malvinder S
authors.initials: MS
authors.lastname: Parmar
mesh_terms: D055499:Catheter-Related Infections / Q000097:blood / Q000473:pathology; D002951:Citrates / Q000009:adverse effects* / Q000737:chemistry; D006801:Humans; D006955:Hypernatremia / Q000097:blood* / Q000473:pathology; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000009:adverse effects*; D012189:Retrospective Studies
chemical_list: D002951:Citrates; C514290:trisodium citrate
keywords: Citra-Lock; assay interference; dialysis catheter; hypernatremia; pseudohypernatremia