BACKGROUND: Although pulmonary artery catheters are useful to monitor hydration, these devices may be associated with severe morbidity and are not routinely used in kidney transplantation. A central venous pressure (CVP) catheter is preferred rather than a pulmonary artery catheter. Noninvasive continuous blood pressure monitors may substitute for intraarterial catheters, thereby preserving the radial artery in kidney transplantation patients should it be needed later to create an arteriovenous fistula. If there is a relationship between central venous and radial arterial blood for acid-base (pH, BE, HCO3(-)), we can use the blood sample from a CVP catheter instead of arterial blood from aradial artery catheter for testing acid-base and it can help patients. METHODS: A central venous catheter and radial artery catheter was inserted in 67 patients while undergoing kidney transplantation. To assess arteriovenous differences in acid-base status at operation start, before reperfusion of the transplanted kidney, after reperfusion, we measured the pH, BE and HCO3(-) simultaneously from the arterial and central venous circulation. RESULTS: Aacid-base using arterial and central venous samples at operation start, before reperfusion and after reperfusionb was evaluated. We found the relationship as follows: pH between arterial (pHa) and central venous blood (pHcv) in each: linear regression equation; pHcv = 0.668 + (0.906 X pHa), pHcv = 0.225 + (0.965 X pHa), pHcv = 0.646 + (0.908 X pHa), determination coefficient; 0.908, 0.926, 0.888, P values < 0.001 in each period. Base excess (BE) between BEa and BEcv in each period: linear regression equation; BEcv = 0.483 + (0.952 X BEa), BEcv = 0.032 + (0.939 X BEa), BEcv = 0.008 + (0.954 X BEa), determination coefficient; 0.844, 0.954, 0.962 P values < 0.001 in each period. HCO3(-) concentration between HCO3(-)a and HCO3(-)cv in each period: linear regression equation; HCO3(-)cv = 2.434 + (0.937 X HCO3(-)a), HCO3(-)cv = 2.093 + (0.942 X HCO3(-)a), HCO3(-)cv = 1.755 + (0.954 X HCO3 a), determination coefficient; 0.950, 0.925, 0.932 P values < 0.001 in each period. CONCLUSIONS: The acid base status of arterial blood is similar to that of central venous blood. Central venous blood gas values (pH, BE, HCO3(-)) may be an acceptable alternative to arterial blood gas values in kidney transplantation patients.