What is the first step in treating a casualty with an open fracture?

Covering the wound with a sterile dressing is the first step in treating a casualty with an open fracture because it helps to protect the exposed bone and tissues from contamination and potential infection. This action is crucial as open fractures are at a higher risk for infection due to their direct communication with the external environment. By securing a sterile dressing over the wound, you create a barrier that minimizes the risk of pathogens entering the injury site.

Moreover, addressing wound protection is a priority in trauma care. Once the wound is properly covered, other steps, such as immobilization with a splint, checking for pulse, and managing pain, can follow. These actions are important but secondary to ensuring that the immediate risk of contamination is mitigated by covering the wound adequately.