Description Hemorrhage is a major cause of hypovolemic shock. However, plasma loss/ dehydration and interstitial fluid accumulation (third spacing) adversely reduce circulating volume by decreasing tissue perfusion. The primary defect is decreased preload. Four classifications of hypovolemic shock based on the amount of fluid and blood loss: Class I: <750 ml, or ? 15% total circulating volume. Class II: 750 to 1000 ml, 05 15% to 30% total circulating volume Class III: 1500 to 2000 ml, or 30% to 40% total circulating volume Class IV: >2000 ml, or > 40% total circulating volume. The patient’s compensatory response intensifies as the