Continuous assessment of oxygen saturation and subcutaneous oxygen tension after abdominal operations

Ten patients undergoing abdominal operations had oxygen saturation (SpO2) and transcutaneous (PtcO2) and subcutaneous (PscO2) oxygen tensions monitored continuously during the second and third postoperative nights from 11 pm to 7 am. At the end of the second postoperative night an oxygen stimulation test (10 l/min by face mask) was carried out in eight of the 10. Median SpO2 was 91% (range 82-95) on the second, and 91% (86-95) on the third, postoperative nights, respectively. Six patients had intermittent episodes of desaturation to less than 80%, each of less than one minute's duration. PtcO2, but not PscO2, followed the episodic variations in SpO2. PscO2 was 58 mmHg (46-69) on the second postoperative night and 61 mmHg (48-71) on the third postoperative night. PscO2 correlated with SpO2 in all but one patient who had lower PscO2 than expected from the measured SpO2 and estimated PaO2. Oxygen treatment increased individual PscO2 by 14 mmHg (9-49), PtcO2 by 38 mmHg (10-104), and SpO2 to 99% (95-100), but stable PscO2 was not achieved within the 20 minute period of treatment. These results obtained during continuous measurements show pronounced intersubject differences in oxygen tensions near the surgical wound in the late postoperative period. The results suggest that pulmonary oxygenation is the most important determinant of mean subcutaneous oxygen tension after uncomplicated elective abdominal operations.