Nitrous oxide does not affect automated air tonometry in children: (Le protoxyde d'azote n'agit pas sur la tonometrie a l'air, automatisee, chez les enfants).

摘要

PURPOSE: To evaluate the effects of nitrous oxide on automated air tonometry in the clinical setting. Material and methods: With approval of the Hospital Ethical Committee and after obtaining informed parental consent, an 8-F tonometry catheter was inserted orogastrically in ten children aged one to three years scheduled for elective surgery with combined regional and general anesthesia. A standardized general anesthesia technique with tracheal intubation was used in all patients and consisted of sevoflurane in oxygenitrous oxide (30%/70%; n = 5 patients) or in oxygen/air (FIO(2) 0.3; n = 5 patients). After obtaining steady state gastric CO(2) values (PrCO(2)), fresh gas mixtures were rapidly changed from oxygenitrous oxide to oxygen/air (A) or vice versa (B). In addition, balloon pressures were recorded using a pressure transducer. Measurements were performed at intervals of ten minutes with recording of balloon pressures, end-tidal CO(2) (PETCO(2)) and PrCO(2) values. Pr-ETCO(2)-gap were calculated to eliminate influences of changes in PaCO(2). RESULTS: Changing the fresh gas mixture from N(2)O/O(2) to O(2)/air resulted in a decrease of balloon pressure of -10.4% (113.4 +/- 14.7 mmHg to 101.6 +/- 25.0 mmHg). Changing the fresh gas mixture from O(2)/air to N(2)O/O(2) resulted in an increase of balloon pressures of 6.4% (107.6 +/- 19.3 mmHg to 114.0 +/- 20.3 mmHg). During both fresh gas exchange experiments no significant changes (> 0.2 kPa) in calculated Pr-ETCO(2)-gaps were observed. CONCLUSIONS: Based on our in vivo data, nitrous oxide during general anesthesia can be used with automated air tonometry and does not affect air tonometric PrCO(2) reading in clinical practice.