護理師評估低血容性休克病人，下列哪個代償機制最先出現？

當循環血量減少，壓力感受器（Baroreceptors）感測到血壓下降，會立即啟動交感神經系統，首要反應是心跳加速（Tachycardia）以維持心輸出量。隨後才會進入腎素-血管張力素系統以滯留水分，尿量減少是後續反應，而非最先出現的代償。

Tachycardia is the earliest compensatory mechanism in hypovolemic shock, triggered by baroreceptors sensing decreased blood pressure to maintain cardiac output via sympathetic nervous system activation. Peripheral vasoconstriction and decreased urine output occur subsequently as part of the renin-angiotensin-aldosterone system response.

美國 nursing school 考試常考早期與晚期休克區分；台灣臨床則多以生命徵象監測為主。