Is liquid heparin comparable to dry balanced heparin for blood gas sampling in intensive care unit?

Blood gas (BG) analysis is required for management of critically ill patients in emergency and intensive care units. BG parameters can be affected by the type of heparin formulations used-liquid heparin (LH) or dry balanced heparin (DBH). This study was conducted to determine whether blood gas, electrolyte, and metabolite estimations performed by using DBH and LH are comparable.

A prospective study was conducted at pediatric intensive care unit (PICU) of a tertiary care hospital. Paired venous samples were collected from 35 consecutive children in commercially prepared DBH syringes and custom-prepared LH syringes. Samples were immediately analyzed by blood gas analyzer and compared for pH, pCO2, pO2, HCO3 (-), Na(+), K(+), Cl(-), and lactate. Paired comparisons were done and agreement was assessed by Bland-Altman difference plots. The 95% limits of absolute agreement (LOA) were compared with the specifications for total allowable error (TEa).

The P values were significant for all measured parameters, with the exception of pCO2 and K +. Bland-Altman difference plots showed wide LOA for pCO2, pO2, HCO3 (-), Na(+), K(+), and Cl(-) when compared against TEa. For pCO2, HCO3 (-), Na(+), K(+), and Cl(-), 40%, 23%, 77%, 34%, and 54% of samples were outside the TEa limits, respectively, with LH.

Our study showed that there is poor agreement between LH and DBH for the BG parameters pCO2, pO2, HCO3(-), K(+), Na(+), and Cl(-) and, thus, are not comparable. But for pH and lactate, LH and DBH can be used interchangeably.