Single versus multiple pulmonary emboli: different haemodynamic and blood gas results

We evaluated haemodynamic and blood gas changes following the intravenous infusion of starch microemboli (63-74 mu). Comparisons were made between dogs receiving a single embolus and dogs receiving an equal quantity of embolus divided into small doses given at 30 minute intervals (multiple emboli). The most significant finding was that the same quantity of embolus produces different effects. In the dogs receiving a single embolus of 150 mg kg-1 of starch. Pao2 fell from 11.3 to 7.6 kPa (85 to 57 torr)(p less than 0.025) and Qs/Qt increased from 11 to 34 per cent (p less than 0.01). In the multiple emboli dogs, after a total dose of 150 mg kg-1 of starch, there was a small but not significant fall in Pao2 from 11.6 to 10.8 kPa (87 to 81 torr), and Qs/Qt did not change significantly. In the single embolus dogs Q increased significantly after an embolus of 100 mg kg-1 of starch (p less than 0.05). after a single embolus of 150 mg kg-1, Q was variable; 3 dogs showed a decrease, and 2 an increase, however the mean change was not significant. In the multiple emboli dogs, Q decreased significantly (p less than 0.005).