Agreement of Measurement between Arterial and Venous Electrolyte Levels in Neonates in a Tertiary Care Hospital.

 Venous or arterial blood is used for the estimation of electrolytes in neonates in neonatal intensive care unit (NICU). In addition to the measurement of blood gases and bicarbonate in the arterial blood, arterial blood gas analysis also estimates electrolytes thus circumventing the need to collect a venous sample for electrolytes. The literature survey revealed studies comparing the electrolyte levels in arterial and venous blood in adults and older children, but to our knowledge none were found in neonates, hence the study.  The aim of the study is to compare the electrolytes in arterial and venous samples in neonates in a critical care set up and derive in-house prediction equation to correlate the arterial and venous electrolytes.  Hospital-based, retrospective cross-sectional study done in critically ill neonates.  All the newborns (age ≤28 days) admitted in NICU from July 2016 to June 2018 were selected for the study and data collected with the help of Hospital Information System.  MedCalc and NCSS 12 (trial version) software was used. Deming Regression and Bland Altman analysis were performed.  A strong positive correlation between the arterial and venous blood electrolytes observed. An in-house prediction equation was derived for the venous electrolytes. Deming regression analysis showed that only potassium levels are statistically equivalent between the instruments and the sample type. Bland Altman Analysis between the arterial and venous electrolytes showed a mean difference which was well within the accepted Clinical Laboratory Improvement Amendment guidelines.  The electrolyte levels estimated by arterial blood in neonates can be used in an interchangeable manner only for potassium levels, whereas sodium and chloride estimation necessitates one to be cautious.