Classification of hemorrhage based on blood loss is as follows:

1. Class I: blood loss of up to 15% of blood volume—normal pulse and blood pressure

2. Class II: blood loss of up to 30% of blood volume—tachycardia, decreased urine output, and mild anxiety

3. Class III: blood loss of up to 40% of blood volume—significant tachycardia and hypotension with narrow pulse pressure; oliguria; development of a base deficit; and declining Glasgow Coma Scale score

4. Class IV: blood loss of more than 40% of blood volume—profound tachycardia and hypotension; delayed capillary refill; tachypnea; anuria; worsening base deficit; and confusion or lethargy

References

• Galvagno SM Jr, Nahmias JT, Young DA. Advanced Trauma Life support update 2019: management and applications for adults and special populations. Anesthesiol Clin. 2019;37:13-32.