Advanced Trauma Life Support ATLS Student Course Manual 2018

HEMORRHAGIC SHOCK 49
of obese adults is estimated based on their ideal body
weight, because calculation based on actual weight can
result in significant overestimation. The blood volume
for a child is calculated as 8% to 9% of body weight
(70–80 mL/kg). (See Chapter 10: Pediatric Trauma.)
Physiologic Classification
The physiologic effects of hemorrhage are divided
into four classes, based on clinical signs, which are
useful for estimating the percentage of acute blood loss.
The clinical signs represent a continuum of ongoing
hemorrhage and serve only to guide initial therapy.
Subsequent volume replacement is determined by
the patient’s response to therapy. The following
classification system is useful in emphasizing the early
signs and pathophysiology of the shock state:
••
Class I hemorrhage is exemplified by the condition
of an individual who has donated 1 unit of blood.
••
Class II hemorrhage is uncomplicated
hemorrhage for which crystalloid fluid
resuscitation is required.
••
Class III hemorrhage is a complicated hemorrhagic
state in which at least crystalloid infusion is
required and perhaps also blood replacement.
••
Class IV hemorrhage is considered a
preterminal event; unless aggressive measures
are taken, the patient will die within minutes.
Blood transfusion is required.
n TABLE 3-1 outlines the estimated blood loss and other
critical measures for patients in each classification
of shock.
Class I Hemorrhage: