Myth or reality: hematocrit and hemoglobin differ in trauma

Area of Science:

• Traumatology
• Clinical Chemistry
• Laboratory Medicine

Background:

• Estimating blood loss in trauma patients typically involves hematocrit (Ht) or hemoglobin (Hb) measurements.
• A common practice in trauma care is to measure both Ht and Hb, assuming they offer distinct information for acute blood loss assessment.
• Literature suggests a strong association between trauma and Ht determination, prompting investigation into potential differences between Ht and Hb in this patient group.

Purpose of the Study:

• To investigate whether hematocrit (Ht) and hemoglobin (Hb) provide different information in trauma patients.
• To determine the relationship between Ht and Hb measurements in patients with severe trauma.

Main Methods:

• Analysis of paired Ht and Hb blood samples from trauma patients (Injury Severity Score > 15) admitted between 1996 and 2004.
• Measurements of Ht and Hb using a Coulter Counter.
• Linear regression analysis to determine the relationship between Ht and Hb; lactate dehydrogenase levels were analyzed to assess hemolysis.

Main Results:

• A total of 2,461 paired Ht and Hb measurements were obtained from 671 trauma patients.
• A strong correlation was observed between Ht and Hb (Pearson's R = 0.99), with established conversion formulas.
• Lactate dehydrogenase levels did not correlate with Ht or Hb, ruling out significant hemolysis as a confounding factor.

Conclusions:

• Hematocrit (Ht) and hemoglobin (Hb) function as interchangeable parameters in trauma patients.
• The belief that Ht offers different or superior information compared to Hb in trauma is a misconception.
• There is no clinical justification for performing both Ht and Hb tests when assessing acute blood loss in trauma patients.