CONTINUOUS INTRAARTERIAL BLOOD-GAS MONITORING DURING ESOPHAGECTOMY

Purpose: To evaluate the clinical usefulness of the continuous intra-a rterial blood gas (CIABG) monitoring system, Paratrend 7 (TM), during differential lung ventilation (DLV) in 12 patients undergoing oesophag ectomy. Methods: Anaesthesia was induced with propofol and was maintai ned with isoflurane, oxygen and air, supplemented by an epidural infus ion of mepivacaine. Arterial samples for estimation of blood gases (AB G) were taken just before and 5, 10, 20, 30, 60, and 90 min after the pleura was opened. The pH, PO2, and PCO2 values displayed by the CIABG monitor, which were recorded prior to the arterial blood sampling, we re compared with the results of ABG analysis. Results: Eighty-four blo od samples were obtained and the ranges for the measured variables wer e PCO2 24.8-57.4 mmHg, PO2 47-449 mmHg, and pH 7.30-7.49. The correlat ion between CIABG and ABG measurements was strong and significant (r v alues: PCO2 0.80, PO2 0.93, pH 0.94). The overall bias +/- precision b etween the two methods was PCO2 0.9 +/- 3.1 mmHg, PO2 -1 +/- 40 mmHg, %PO2 0.8 +/- 21.6%, pH 0.00 +/- 0.02. For PO2 values < 150 mmHg, the b iases +/- precision were PO2-5 +/- 17 mmHg, %PO2 -2.1 +/- 20.7%. Concl usion: The agreement between CIABG and ABG measurements was better for PCO2 and pH than for PO2. Although the CIABG system is clinically use ful for monitoring trends in blood gas changes, the accuracy of the PO 2 value may be unacceptable during DLV because the error is theoretica lly < 34 mmHg with 95% reliability in the clinically important range o f PO2, < 150 mmHg.