Background: Severe injury is often complicated by the development of sepsis and the adult respiratory distress syndrome. Since the outcome from severe injury also correlates with changes in monocyte human leukocyte antigen (HLA)-DR expression in such patients, the present study aimed to determine whether or not there was a relationship between monocyte HLA-DR expression and indicators of early pulmonary dysfunction.

Methods: Monocyte HLA-DR expression and serum interleukin (IL)-6 were measured on admission and then again on days 1, 3, 5, and 7 after major injury in 29 patients admitted for the management of trauma with an injury severity score of 9 or more. Noninvasive intrapulmonary shunt measurement was also performed in all these patients within 6 hours of emergency surgery in all patients.

Results: Monocyte HLA-DR followed the characteristic suppression followed by recovery in those who followed an uncomplicated course but progressively declined in those who suffered septic complications. The degree of intrapulmonary shunting observed 6 hours after injury in the patients who developed sepsis was significantly higher than that in the uncomplicated group. Peak monocyte HLA-DR expression during the recovery phase correlated inversely with the degree of intrapulmonary shunting.

Conclusions: The degree of intrapulmonary shunting observed following severe trauma correlates with the failure of circulating monocytes to re-express HLA-DR antigen, and this may provide some insights into the early events that result in the adult respiratory distress syndrome after major injury.