Which of the following statement(s) is/are true concerning the Advanced Trauma Life Support (ATLS) classification system of hemorrhagic shock?

a. Class I shock is equivalent to voluntary blood donation

d. Class IV hemorrhage involves loss of over 40% of blood volume loss and can be classified as life-threatening

The classification of hemorrhagic shock as defined by the ATLS classification system of the American College of Surgeons is useful in comprehending the manifestations and physiologic changes associated with shock. Mild hemorrhage, up to 15% of total blood volume, is exemplified by voluntary blood donation. In the supine position, there are no measurable changes in heart or respiratory rates, blood pressure or pulse pressure. Class II hemorrhage involves loss of 15% to 30% of volume loss. Clinical signs include tachycardia and tachypnea. The systolic blood pressure may be only slightly decreased, especially in the supine position, but the pulse pressure is narrowed. Patients with Class II hemorrhage can generally be resuscitated with crystalloid solutions but some may require blood transfusions. With Class III hemorrhage, 30% to 40% of total body volume is lost. Patients with Class III hemorrhage present with obviously inadequate perfusion; marked tachycardia and tachypnea, cool, clammy extremities with significant delayed capillary refill; hypotension; and significant changes in mental status. Class III hemorrhage represents the smallest volume of blood loss that consistently produces a decrease in systolic blood pressure. The resuscitation of these patients requires blood transfusion in addition to crystalloid administration. Class IV hemorrhage involves loss of greater than 40% of blood volume. This represents life-threatening hemorrhage. These patients require immediate transfusion for resuscitation and frequently require immediate surgical intervention.