Background: In vitro, air bubbles can induce platelet activation and platelet to air bubble binding. We therefore tested in vivo the hypothesis that venous air embolism (VAE) induces (1) platelet dysfunction and (2) thrombocytopenia.
Methods: Adult swine (60.8+/-3.9 kg; n=8) were anaesthetized, mechanically ventilated, and placed in a semi-upright position. Air boli (0.5-80 ml) were injected randomly via an ear vein, and arterial blood was sampled after cumulative air dosages of 0, 80, 160, and 240 ml. Coagulation was assessed by impedance aggregometry, rotational thrombelastometry, whole blood count, plasmatic coagulation variables, and fibrinogen, d-dimer, protein C, and antithrombin plasma concentrations, respectively.
Results: VAE induced a 47% decrease in platelet count (303 vs. 160 nl(-1); P<0.001) over the dose range assessed, with haematocrit being unaltered. Furthermore, VAE-impaired platelet aggregation induced by adenosine diphosphate, arachidonic acid, collagen, and the thromboxan analogue U46619 over the dose range assessed independent of thrombocytopenia. (P<0.05 vs. baseline). In contrast, rotational thrombelastometry alone was quite insensitive in detecting VAE-induced coagulation changes, showing only at near lethal air dosages a prolonged clot formation time following activation with tissue factor, contact activator, and during spontaneous coagulation (P<0.05 vs. baseline).
Conclusions: VAE induces both a dose-dependent decrease in platelet count and a marked decrease in platelet aggregation, independent of thrombocytopenia (P<0.05 vs. baseline).