Background The measurement of gastric–arterial partial CO2 pressure difference (PgCO2–PaCO2 = PCO2 gap) with gastric tonometry may help us to monitor the stability of circulation. However, it is very difficult to follow up the condition with frequent acid-base examinations, especially in the case of neonates. In our present examinations we wanted to compare the conventional PCO2 gap with alternative gaps of PETCO2 gap (PgCO2–end-tidal carbon dioxide) and tCO2 gap (PgCO2–transcutaneous CO2).
Methods Gastric tonometric examinations were performed with a new, balloon-free tool developed at our department. PaCO2 was determined with an acid-base automate, PETCO2 and PgCO2 were measured with a side stream capnograph and tCO2 was determined with a Radiometer Copenhagen transcutaneous blood gas monitor. We performed prospective pilot studies on ventilated neonates requiring intensive care (PETCO2 gap study: n = 24, 14 surviving, seven non-surviving patients, weight: 1930 ± 1136 g; tCO2 gap study: n = 10, weight: 2471 ± 774 g, all surviving patients). Student’s t test and Pearson’s correlation were applied as statistical methods.
Results The PETCO2 gap was higher than conventional PCO2 gap (12.0 ± 9.9 versus 6.1 ± 9.9 mm Hg, p<0.01) whereas there was no significant difference between the tCO2 and conventional PCO2 gaps (1.1 ± 5.8 versus 0.1 ± 7.7 mm Hg). There were significant correlations (p<0.01, r = 0.58) between any two of the four PCO2 parameters.
Conclusions According to our findings the PETCO2 and possibly also tCO2 gaps may be used as methods of continuous estimation of splanchnic perfusion. However, because of the difficulties in the technique of the measurement of tCO2 and PETCO2 in neonates, the conventional PCO2 gap should not be abandoned.