title: Falsely elevated sodium levels during thiopental treatment in the ICU: technical interference on a laboratory device with important clinical relevance.
abstract: BACKGROUND
  Thiopental is a cornerstone in the treatment of refractory status epilepticus and intractable intracranial hypertension. In our center we observed that thiopental might cause falsely elevated serum sodium levels.
  
  
  METHODS
  Triggered by a recent case experience of extremely elevated serum sodium levels during thiopental treatment, we retrospectively identified 53 patients treated with thiopental in our intensive care unit between 2007 and 2011 and evaluated electrolyte changes. We differentiated the analysis before and after introduction of a new device for sodium assays (Dimension Vista, Siemens) in the central laboratory in April 2010. Standardized in vitro laboratory tests were performed to study the effect of thiopental on sodium analysis.
  
  
  RESULTS
  Before April 2010, serum sodium levels determined in the central laboratory showed a good agreement with the bedside point-of-care (POC) device during thiopental therapy with [sodium](laboratory) - [sodium](POC) of only 1.08 mmol/L (P = .0517). After April 2010, a strong discrepancy between laboratory values and POC values was observed with [sodium](laboratory) - [sodium](POC) = 11.57 mmol/L (P < .0001). Standardized in vitro testing confirmed that thiopental induced a dose-dependent false hypernatremia (P = .002).
  
  
  CONCLUSIONS
  Thiopental treatment can result in falsely elevated serum sodium. This is a critical finding since high sodium levels preclude administrating mannitol or hypertonic saline for the treatment of elevated intracranial pressure. Moreover, a false high sodium level might lead to the inappropriate administration of hypotonic fluids potentially resulting in increased brain edema and even higher intracranial pressure. To our knowledge, this is the first paper describing this clinically relevant phenomenon.
authors.affiliation: Department of Neurosurgery, Antwerp University Hospital, University of Antwerp, Wilrijkstraat 10, 2650, Edegem, Belgium. bart.feyen@uza.be
authors.forename: Bart F E
authors.initials: BF
authors.lastname: Feyen
authors.forename: Dries
authors.initials: D
authors.lastname: Coenen
authors.forename: Philippe G
authors.initials: PG
authors.lastname: Jorens
authors.forename: Kristien
authors.initials: K
authors.lastname: Wouters
authors.forename: Andrew I R
authors.initials: AI
authors.lastname: Maas
authors.forename: Viviane
authors.initials: V
authors.lastname: Van Hoof
authors.forename: Walter
authors.initials: W
authors.lastname: Verbrugghe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000009:adverse effects*; D001774:Blood Chemical Analysis / Q000295:instrumentation; D003951:Diagnostic Errors; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D006955:Hypernatremia / Q000175:diagnosis*; D007362:Intensive Care Units; D019586:Intracranial Hypertension / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D012189:Retrospective Studies; D012964:Sodium / Q000097:blood*; D013226:Status Epilepticus / Q000188:drug therapy*; D013874:Thiopental / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D000927:Anticonvulsants; D012964:Sodium; D013874:Thiopental