Automated detection of gastric luminal partial pressure of carbon dioxide during cardiovascular surgery using the Tonocap

Background: A new automated system of air tonometry (Tonocap; Datex Ohmeda, Helsinki, Finland) allows for frequent (every 15 min) measurement of gastr ic luminal partial pressure of carbon dioxide. Its use has not been describ ed in cardiac surgical patients. Methods: One hundred patients undergoing coronary artery bypass graft or ca rdiac valve surgery were enrolled in a prospective cohort study. After anes thetic induction and insertion of a TRIP NGS Catheter (Datex Ohmeda), measu rements of gastric luminal partial pressure of carbon dioxide were obtained using the Tonocap, and gastric mucosal pH (pHi) was calculated. The main o utcome measure was postoperative complication, defined as either in-hospita l death or prolonged postoperative hospitalization (> 14 days). Results: Four patients (4%) died, all of multiple-system organ failure, one each on postoperative days 9, 26, 46, and 121, Postoperative complication occurred in 18 patients (18%), all of whom exhibited persistent dysfunction of at least one organ system, Perioperatively, an abnormal pHi (< 7.32) an d gastric luminal minus arterial partial pressure of carbon dioxide gap (> 8 mmHg) occurred in 66% and 70% of patients, respectively. Predictors of po stoperative complication included postoperative pHi (P = 0.001), gastric lu minal partial pressure of carbon dioxide (P = 0.022), and gastric luminal m inus arterial partial pressure of carbon dioxide gap (P = 0.013). In contra st, arterial base excess (P > 0.4) and routinely measured hemodynamic varia bles (e.g., heart rate, blood pressure) were either less predictive compare d with Tonocap-derived variables or not predictive, Conclusions: Despite a low mortality rate, patients undergoing cardiac surg ery exhibited high incidences of prolonged hospitalization and postoperativ e morbidity. The Tonocap was easy to use, particularly compared with saline tonometry, Several Tonocap-derived variables were predictive of postoperat ive complications consistent with previously published data using saline to nometry.