Impact of nitrous oxide on the haemodynamic consequences of venous carbon dioxide embolism

BACKGROUND Nitrous oxide (N 2 O) is still considered an important component of general anaesthesia. However, should gas embolisation occur as result of carbon dioxide (CO 2) pneumoperitoneum, N 2 O may compromise safety, as the consequences of a gas embolus consisting of a combination of CO 2 and N 2 O may be more severe than CO 2 alone. OBJECTIVE This experimental study was designed to compare the cardiopulmonary consequences of gas embolisation with a N 2 O/CO 2 mixture, or CO 2 alone. DESIGN Experimental study. SETTING Research Institute Against Digestive Cancer laboratory, Strasbourg, France. ANIMALS Seven Large-White pigs receiving standardised inhalation anaesthesia. INTERVENTIONS Each animal, acting as its own control, was studied in two successive experimental conditions - intravenous gas injections of 2-ml-kg -1 of 100% CO 2 and 2-ml-kg -1 of a gas mixture consisting of 10% N 2 O and 90% CO 2. MAIN OUTCOMES MEASURES Haemodynamic and ventilatory consequences of embolisation with the gases. RESULTS We found that the haemodynamic (heart rate, mean arterial blood pressure, central venous pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure and transoesophageal echocardiography parameters) and ventilatory (arterial oxygen saturation, end-tidal CO 2 concentration and mixed venous oxygen saturation) consequences of embolisation with either 100% CO 2 or 10% N 2 O with 90% CO 2 were similar. CONCLUSION The findings of this study may alleviate concerns that the use of N 2 O, as a part of a balanced general anaesthesia technique, may have greater adverse consequences should embolisation of pneumoperitoneal gas containing N 2 O occur.