A 64 year old hypertensive obsese female was undergoing surgery for fracture femur under general anaesthesia. Intra-operatively her end-tidal carbon dioxide decreased to 20 from 40 mm of Hg, followed by hypotension and oxygen saturation of 85%. What could be the most probable cause?

"Arterial blood gas analysis reveals hypoxemia and hypocapnia, with subsequent metabolic acidosis in severe pulmonary embolism. During anaesthesia, end tidal CO2 concentration may fall dramatically because of increased dead space and reduced cardiac output". _________ Anesthesia & Intensive care Note : Fat embolism can present as pulmonary embolism when an extensive fat embolism of lung is present.