Effect of smoke inhalation injury on thromboxane levels and platelet counts

Thirteen goats with chronic lung lymph fistula suffering from smoke inhalation injury were studied for a 6-h period. All animals were found to have acute respiratory failure after injury, the arterial TXA2 (thromboxane A2) levels had increased by 5 min after injury, they peaked at 2 h, and then subsequently declined. Peripheral platelet counts decreased progressively within 2 h, then gradually recovered but were still lower than baseline values at 6 h after injury. EVLW (extravascular lung water), Q1 (lung lymph flow rate) and L/P (total lymph protein/plasma protein concentration), all increased and peaked at 2 h after injury. A negative linear correlation was observed between the TXA2 levels and the platelet counts. Furthermore, differences between the venous and arterial platelet counts were markedly increased. All these observations suggested that the increased TXA2 triggered the formation of platelet microaggregates which were then trapped in the microvasculatures of viscera such as the lung. This might be one of the causes of the decreased platelet counts in peripheral blood. Both TXA2 levels and platelet counts were closely correlated with EVLW, suggesting that TXA2 may indirectly cause the increased pulmonary microvascular permeability by promoting platelet aggregation and microaggregate formation in the pulmonary microvasculature. This may be one of the reasons for the developing pulmonary oedema in goats following smoke inhalation injury.