Correlation and Interchangeability of Venous and Capillary Blood Gases in Non-Critically Ill Neonates

Venous blood gas (VBG) is frequently used in the neonatal unit as alternative for capillary blood gas (CBG). However, studies reporting correlation are conflicting and data on interchangeability in neonates are lacking. We investigated the correlation and interchangeability of the components between VBG and CBG in infants admitted to the neonatal intensive care unit. In a prospective study in the neonatal unit in Leiden University Medical Center (Netherlands), simultaneously VBG and CBG were withdrawn in neonates when both venous puncture and intravenous access as blood gas monitoring was indicated. From each blood gas analysis, a Pearson correlation, intraclass correlation, and Bland-Altman analysis was performed. Clinically acceptable difference for each blood gas value was defined up-front by means of an absolute difference: pH ± 0.05; partial pressure of carbon dioxide (pCO ) (±0.67 kPa = 5 mmHg); partial pressure of oxygen (pO ) (±0.67 kPa = 5 mmHg); base excess ± 3 mmol/l; and bicarbonate (HCO ) ± 3 mmol/l. In 93 patients [median gestational age 31 (IQR 29-34) weeks], 193 paired samples of VBG and CBG were collected. The Pearson correlation between VBG and CBG was very strong for pH ( = 0.79;