What is hypovolemic shock primarily caused by?

Hypovolemic shock occurs primarily due to significant blood or fluid loss, which leads to a decrease in the volume of blood circulating in the body. This reduction in blood volume results in inadequate perfusion of tissues and organs, compromising oxygen delivery and leading to potential organ failure if not promptly addressed. Common causes of such fluid loss can include severe bleeding from trauma, gastrointestinal bleeding, or excessive fluid loss due to severe dehydration from vomiting, diarrhea, or excessive sweating.

In contrast, excessive fluid intake does not lead to hypovolemic shock; instead, it may result in conditions like fluid overload or heart failure. Pulmonary embolism is a condition where a blood vessel in the lungs becomes blocked, affecting blood flow but not directly causing hypovolemic shock. Severe allergic reactions can lead to anaphylactic shock, which is characterized by systemic vasodilation and bronchoconstriction, rather than the fluid loss seen in hypovolemic shock. Thus, the primary cause of hypovolemic shock is indeed significant blood or fluid loss leading to hypoperfusion.