What is the primary cause of hypovolemia during orthopedic surgery?

The primary cause of hypovolemia during orthopedic surgery is surgical blood loss. During surgical procedures, especially those involving significant manipulation of tissues, there can be substantial bleeding. Orthopedic surgeries often involve the cutting and repositioning of muscles, bones, and other tissues, leading to a risk of hemorrhage. This blood loss can lead to a decreased volume of circulating blood, resulting in hypovolemia.

In the context of orthopedic surgery, while fluid retention, excessive urinary output, and dehydration are important factors to consider in patient management, they are generally not as significant a cause of hypovolemia during the procedure itself. Surgical interventions involve bleeding that overshadows these other factors, making surgical blood loss a primary concern in maintaining adequate blood volume and ensuring patient stability throughout the operation.