Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.

I was given heparin injections after my last two operations for three days - no idea if it was the heparin or something else they were giving me but I was vomiting and had nasty nausea on that last day in hospital - felt so much better once I got home and off their drugs.