USEFULNESS OF CONTINUOUS AIR TONOMETRY FOR EVALUATION OF SPLANCHNIC PERFUSION DURING CARDIOPULMONARY BYPASS

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Although gastric mucosal tonometry has been reported as a useful method to assess splanchnic perfusion during cardiovascular surgery, conventional discontinuous method of tonometry (saline tonometry) was laborious, cumbersorne and prone to systematic errors. A new automated system of air tonometry (Tonocap, Datex Ohmeda, Helsinki Finland) allows for frequent (every 10 min) measurement of gastric regional-CO2 (PrCO2) and may be more suitable as a monitoring system in cardiac patients. We evaluated the usefulness of continuous air tonometry as a marker of splanchnic perfusion during cardiopulmonary bypass (CPB). Method: In 12 patients (53–77yrs, mean 66) who underwent cardiovascular surgery with CPB from January to May 2001, the PrCO2 and calculated intramucosal pH (pHi) of gastric tonometry was monitored using Tonocap and their relation to postoperative (PO) visceral organ function was evaluated. Results: The pHi significantly increased after initiation of CPB from 7.31 ± 0.06 to 7.47 ± 0.05 (p < 0.05) and then consistently decreased in all patients to 7.33 ± 0.03 at the end of CPB. The lowest value of pHi during CPB was significantly related to BUN (r=0.84, p < 0.05), Cr (r=0.92, p < 0.05) and CCr (r = 0.96, p < 0.01) on the 1 st PO day. In contrast, arterial base excess, arterial blood lactate level, venous oxygen saturation and routinely measured hemodynamics (e.g., pump flow, blood pressure) during CPB were unrelated to the postoperative visceral organ function. Conclusion: These results suggest that continuous monitoring of gastric pHi by air tonometry system is useful for the evaluation of splanchnic perfusion during CPB and may contribute to improve CPB technique by allowing the early detection of visceral malperfusion.

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