Falsely Elevated Sodium Levels During Thiopental Treatment in the ICU: Technical Interference on a Laboratory Device with Important Clinical Relevance

Introduction 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