Such ratio value is clinically employed to determine the scope or emergence of shock. The SI correlates with the extent of hypovolemia and thus may facilitate the early identification of severely injured patients threatened by complications due to blood loss and therefore need urgent treatment, i.e. blood transfusion. Data presented as n (%), mean ± standard deviation or median (interquartile range (IQR)). n = 21,853; P <0.001 for all parameters. ED Emergency department, GCS Glasgow coma scale, HR Heart rate, SBP Systolic blood pressure, SI = Shock index. Bleeding
Recognizing the degree of blood loss via vital sign and mental status abnormalities is important. The American College of Surgeons Advanced Trauma Life Support (ATLS) hemorrhagic shock classification links the amount of blood loss to expected physiologic responses in a healthy 70 kg patient. As total circulating blood volume accounts for approximately 7% of total body weight, this equals approximately five liters in the average 70 kg male patient. Class 1: Volume loss up to 15% of total blood volume, approximately 750 mL. Heart rate is minimally elevated or normal. Typically, there is no change in blood pressure, pulse pressure, or respiratory rate. Class 2: Volume loss from 15% to 30% of total blood volume, from 750 mL to 1500 mL. Heart rate and respiratory rate become elevated (100 BPM to 120 BPM, 20 RR to 24 RR). Pulse pressure begins to narrow, but systolic blood pressure may be unchanged to slightly decreased.
Kidneys
Renal losses of salt and fluid can lead to hypovolemic shock. The kidneys usually excrete sodium and water in a manner that matches sodium intake and water intake.Diuretic therapy and osmotic diuresis from hyperglycemia can lead to excessive renal sodium and volume loss. In addition, there are several tubular and interstitial diseases beyond the scope of this article that cause severe salt-wasting nephropathy. Skin
Fluid loss also can occur from the skin. In a hot and dry climate, skin fluid losses can be as high as 1 to 2 liters/hour. Patients with a skin barrier interrupted by burns or other skin lesions also can experience large fluid losses that lead to hypovolemic shock. Third-spacing
Sequestration of fluid into a third space also can lead to volume loss and hypovolemic shock. Third-spacing of fluid can occur in intestinal obstruction, pancreatitis, obstruction of a major venous system, vascular endothelium or any other pathological condition that results in a massive inflammatory response. Pathophysiology
Blood loss
Hemorrhagic shock is due to the depletion of intravascular volume through blood loss to the point of being unable to match the tissues demand for oxygen. As a result, mitochondria are no longer able to sustain aerobic metabolism for the production of oxygen and switch to the less efficient anaerobic metabolism to meet the cellular demand for adenosine triphosphate.