title: Electrolyte-balanced heparin in blood gas syringes can introduce a significant bias in the measurement of positively charged electrolytes.
abstract: BACKGROUND
  Heparin binds positively charged electrolytes. In blood gas syringes, electrolyte-balanced heparin is used to prevent a negative bias in electrolyte concentrations. The potential pre-analytical errors introduced by blood gas syringes are largely unknown. Here, we evaluate electrolyte concentrations in non-anticoagulated blood compared with concentrations measured in electrolyte-balanced blood gas syringes.
  
  
  METHODS
  Venous blood was collected into plain tubes. Ionized calcium, potassium, sodium and hydrogen ions were analyzed directly using a blood gas analyzer and the remaining blood was collected into different blood gas syringes in random order: Preset (Becton Dickinson), Monovette (Sarstedt) and Pico 50-2 (Radiometer).
  
  
  RESULTS
  Ionized calcium and sodium concentrations were significantly lower in blood collected in Becton Dickinson and Sarstedt syringes compared to non-heparinized (NH) blood. The mean bias exceeded biological variation-based total allowable error, which in most cases leads to clinically misleading individual results. In contrast, ionized calcium concentrations in blood collected in Pico 50-2 syringes were identical to values obtained from NH blood. Sodium showed a minor, yet statistically significant, bias.
  
  
  CONCLUSIONS
  Despite the fact that blood gas syringes now contain electrolyte-balanced heparin, one should be aware of the fact that these syringes can introduce pre-analytical bias in electrolyte concentrations. The extent of the bias differs between syringes.
authors.affiliation: Clinical Laboratory, Catharina Hospital Eindhoven, Eindhoven, The Netherlands.
authors.forename: Miranda
authors.initials: M
authors.lastname: van Berkel
authors.forename: Volkher
authors.initials: V
authors.lastname: Scharnhorst
mesh_terms: D016477:Artifacts; D001784:Blood Gas Analysis / Q000295:instrumentation*; D004573:Electrolytes / Q000097:blood* / Q000737:chemistry / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D013594:Syringes
chemical_list: D004573:Electrolytes; D006493:Heparin