What is one of the earliest signs of hypovolemic shock?

Increased respiratory rate is one of the earliest signs of hypovolemic shock because as the body experiences a decrease in blood volume, the tissues and organs begin to demand more oxygen. To compensate for the deficiency in blood flow and oxygenation, the respiratory system responds by increasing the rate of breathing. This heightened respiratory effort aims to enhance oxygen intake and carbon dioxide expulsion, which are critical during states of low perfusion and potential organ hypoxia.

The other options, while relevant in various contexts, do not represent early signs of hypovolemic shock. Hypertension is typically not expected in hypovolemic shock; rather, blood pressure often drops due to the loss of circulating volume. A decreased heart rate may occur in response to certain types of shock but is not characteristic of hypovolemic shock, where tachycardia is more common as the body attempts to compensate for low blood volume. An elevated temperature is not an early sign and could suggest an underlying infection rather than indicating the body's response to hypovolemic shock.