Introduction: Venous air-embolism can occur during general anesthesia, potentially leading to mortality and morbidity. Various detection methods have been advocated, with varying degrees of sensitivity (1). Observing nitrogen... [ view full abstract ]
Introduction: Venous air-embolism can occur during general anesthesia, potentially leading to mortality and morbidity. Various detection methods have been advocated, with varying degrees of sensitivity (1). Observing nitrogen in the expired air has been shown to be a simple and reliable test (1-3). Unfortunately, no dedicated expiratory nitrogen meters are available for use in the operating room at the present time. We attempted to ascertain if a commercially available nitrogen meter (PCT Proline Analyzer 61700- 8 Class 85, Ametex, Pittsburg PA 15238), employing mass spectrometry, could be used in an experimental setting using an anesthesia machine and “dummy lung."
Methods: A Drager Apollo™ anesthesia machine was used to ventilate a dummy lung (2 liter) with a minute ventilation of 6L (Vt 500 mL, RR 12/min). The following conditions were used: 1) 100% oxygen at 1L/min, 2) 1:1 nitrous oxide:oxygen with 1% isoflurane at 2L/min, and 3) 1% isoflurane with 100% oxygen at 1L/min. The nitrogen meter (sampling at 0.0004 atm-cc/sec) was attached to the vapor trap inlet of the Apollo™ gas analyzer, thereby capturing any nitrogen ‘exhaled’ from the dummy lung. A small volume of air (1, 2, 5 or 10 mL) was injected into the the distal portion of the dummy lung at different times to assess the detection capabilities of the nitrogen analyzer.
Results: The analyzer detected the presence of nitrogen at every volume when injected in pure oxygen. The amounts of nitrogen detected was proportional to the volume of air injected. Two puffs of albuterol sulfate inhalation aerosol into the dummy lung had no detectable effect on the measured nitrogen levels when the dummy lung was ventilated with 100% oxygen. However, the presence of both isoflurane and nitrous oxide significantly interfered with the measurement of expired nitrogen.
Conclusion: The Proline Nitrogen Analyzer accurately measured nitrogen introduced into a dummy lung ventilated with 100% oxygen. It also worked well if albuterol was present. The analyzer was not useful, however, in accurately detecting nitrogen in the presence of nitrous oxide or isoflurane. Unfortunately, in its present form, this nitrogen analyzer is unsuitable for detection of venous air embolism during anesthesia.
