Hypercarbia induced by detachment of inner fresh gas delivery tube of the bain circuit--a case report.

Semi-open system such as Bain circuit is occasionally used in general anesthesia. The system has many advantages such as use of a single, light weight tube which is adaptable to both adult and pediatric patients and bypass of the carbon dioxide absorber. It is especially useful in procedures on the head, face and neck. The main disadvantage of Bain circuit is the difficulty in testing the inner tube. We encountered a case of hypercarbia due to detachment of the inner fresh gas delivery tube of the Bain circuit. The whole outer tube became a dead space and as a consequence, hypercapnia was unavoidable due to the "to and fro" mechanism of rebreathing. Adequate gas flow and manual hyperventilation would not correct the situation. After changing the tube CO2 tension gradually returned to normal. Many methods for testing of the Bain circuit have been published. Pethick technique, Foëx and Crampton Smith test and test adaptor are useful. Hypercarbia is difficult to detect under general anesthesia. It is often misdiagnosed due to its similarity to other stress responses. Therefore, it is necessary to check ABG's in patients with unexplained tachycardia and/or in those who fight the ventilator even with sufficient amount of muscle relaxant. For quality assurance, use of capnography is recommended for routine use in anesthesia.