title: Performance of automated air tonometry under hypothermia.
abstract: Intestinal tonometry is used during hypothermic cardio-pulmonary bypass surgery to assess splanchnic perfusion. In an in vitro set-up the performance of automated air tonometry (TONOCAP) was tested for normo- and hypothermia. A 14-FG tonometry catheter was built into a testing chamber (100 cm(3)) perfused with blood from a cardio-pulmonary bypass circuit with P(a)co(2) held at 5.6-5.8 kPa (alpha-stat). P(r)co(2) from the balloon of the tonometry catheter was measured at intervals of 10 min at 37 degrees C and at 25 degrees C by the TONOCAP. Bias (precision) of P(r)co(2) - P(a)co(2 alpha-stat) and P(r)co(2) -P(a)co(2 pH-stat) at 37 degrees C blood temperature were low at 0.23 kPa (0.21) each. Tonometrically measured P(r)co(2) at 25 degrees C significantly differed from P(a)co(2 alpha-stat) bias (precision) of 2.00 kPa (0.11) but was similar to P(a)co(2 pH-stat) (0.30 kPa (0.11)). P(r)co(2) values as measured by the TONOCAP represent pH-stat approach. Identical blood gas management (pH- or alpha-stat) should be used for calculation of mucosal-arterial CO(2) difference (P(r-a)co(2) gap) or calculation of intramucosal pH.
authors.affiliation: Department of Anaesthesia, University Children's Hospital, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Weiss
authors.forename: A
authors.initials: A
authors.lastname: Dullenkopf
authors.forename: P
authors.initials: P
authors.lastname: Hasenclever
mesh_terms: D000388:Air; D001831:Body Temperature; D002245:Carbon Dioxide / Q000097:blood; D002315:Cardiopulmonary Bypass; D005753:Gastric Mucosa / Q000098:blood supply; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D008365:Manometry / Q000295:instrumentation / Q000379:methods*; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D010313:Partial Pressure; D012039:Regional Blood Flow; D013152:Splanchnic Circulation
chemical_list: D002245:Carbon Dioxide