Crush syndrome can develop when an area of the body is trapped for longer than how many hours?

• A. 2 hours
• B. 4 hours
• C. 6 hours
• D. 8 hours

Answer: (B)

The key idea here is the time threshold after which prolonged compression can cause systemic injury from the released muscle contents. When a body part is trapped, blood flow is cut off and muscle tissue becomes ischemic. After about four hours of continuous compression, enough muscle cells lyse to dump large amounts of potassium, myoglobin, and other intracellular substances into the circulation. This can lead to dangerous electrolyte imbalances, kidney injury from myoglobin, and other systemic effects — the scenario known as crush syndrome. Therefore, the strongest, most appropriate choice is four hours because the risk becomes significant after that point (and remains high with longer durations).