Class 3: Volume loss from 30% to 40% of total blood volume, from 1500 mL to 2000 mL. A significant drop in blood pressure and changes in mental status occur. Heart rate and respiratory rate are significantly elevated (more than 120 BPM). Urine output declines. Capillary refill is delayed. Class 4: Volume loss over 40% of total blood volume. Hypotension with narrow pulse pressure (less than 25 mmHg). Tachycardia becomes more pronounced (more than 120 BPM), and mental status becomes increasingly altered. Urine output is minimal or absent. Capillary refill is delayed.Again, the above is outlined for a healthy 70 kg individual. Clinical factors must be taken into account when assessing patients. For example, elderly patients taking beta blockers can alter the patients physiologic response to decreased blood volume by inhibiting mechanism to increase heart rate. As another, patients with baseline hypertension may be functionally hypotensive with a systolic blood pressure of 110 mmHg. Non-bleeding
Various laboratory values can be abnormal in hypovolemic shock. Patients can have increased BUN and serum creatinine as a result of pre-renal kidney failure. Hypernatremia or hyponatremia can result, as can hyperkalemia or hypokalemia.Lactic acidosis can result from increased anaerobic metabolism. However, the effect of acid–base balance can be variable as patients with large GI losses can become alkalotic. In cases of hemorrhagic shock, hematocrit and hemoglobin can be severely decreased.
The remaining cases are divided among cardiovascular surgery, critical care, cardiology, obstetrics, and general surgery, with trauma utilizing over 75% of the blood products.As patients age, physiological reserves decrease the likelihood of anticoagulant use increases and the number of comorbidities increases. Due to this, elderly patients are less likely to handle the physiological stresses of hemorrhagic shock and may decompensate more quickly. Fluid loss
While the incidence of hypovolemic shock from extracellular fluid loss is difficult to quantify, it is known that hemorrhagic shock is most commonly due to trauma. In one study, 62.2% of massive transfusions at a level 1 trauma center were due to traumatic injury. In this study, 75% of the blood products used were related to traumatic injury. Elderly patients are more likely to experience hypovolemic shock due to fluid losses as they have a less physiologic reserve.Hypovolemia secondary to diarrhea and/or dehydration is thought to be predominant in low-income countries. See also
Adipsia
Anemia
Cardiac index
Heart murmur


== References ==