Regional capnometry with air-automated tonometry detects circulatory failure earlier than conventional hemodynamics after cardiac surgery

Gastrointestinal automated online air tonometry has been proposed for monit oring gastric perfusion in patients at risk of circulatory failure (CF) aft er cardiopulmonary bypass. In this study, CF was prospectively defined as t he requirement for vasoactive support to maintain mean arterial pressure gr eater than or equal to 70 mm Hg after optimization of preload. Hemodynamic variables-oxygen O-2) delivery (Do(2)), O-2 uptake (Vo(2)), venous-to-arter ial [P(v-a)co(2)], gastric-to-arterial [P(r-a)co(2)], and gastric-to-end-ti dal [P(r-et)co(2)]Pco(2) gap-were retrospectively compared in 14 patients w ith or without CF during a 12-hr postbypass period (H0-H12). In contrast to patients without CF(n = 7), in patients with CF (n = 7) increased Vo2 was not associated with an increase in Do(2). P(r-a)co(2) was larger at H0 in C F patients and was the only variable that differed between the two groups. P(v-a)co(2) did not vary significantly in both groups, whereas P(r-a)co(2) increased to a larger extent from H0 to H12 in patients with CF, suggesting selective gastrointestinal hypoperfusion in this group. P(r-et)co(2) provi ded comparable information to P(r-a)co(2). Hospital length of stay was 9 da ys longer (P ( 0.05) in patients with CF. Increased P(r-a)co(2) and P(r-et) co(2) as monitored with automated air tonometry, were associated with rapid occurrence of CF and prolonged hospital stay after cardiac surgery. Implic ations: Regional and automated capnometry may be used noninvasively to iden tify patients at risk of circulatory failure after cardiopulmonary bypass e arlier than with conventional variables.