What is the hematocrit (Hct) level in a trauma patient?

From the Guidelines

In trauma patients, a hematocrit level below 30% generally indicates significant blood loss and may require immediate intervention, with a transfusion threshold of 7 g/dL recommended to maintain a hematocrit level between 21% and 30% 1.

Key Considerations

• Normal hematocrit ranges are typically 38-52% for men and 36-48% for women.
• A drop in hematocrit of more than 10 percentage points from baseline suggests substantial hemorrhage.
• If hematocrit falls below 21%, consider blood transfusion, typically with packed red blood cells.
• During fluid resuscitation, expect some hemodilution, which can temporarily lower hematocrit.
• However, if hematocrit continues to drop despite fluid administration, suspect ongoing bleeding.

Transfusion Threshold

• A restrictive transfusion regimen with a hemoglobin transfusion trigger of less than 7.0 g/dL is recommended to maintain a hematocrit level between 21% and 30% 1.
• This approach is supported by the Surviving Sepsis Campaign guidelines, which recommend a transfusion threshold of 7 g/dL in critically ill patients 1.

Ongoing Management

• Closely monitor hematocrit levels as part of the initial assessment and ongoing management.
• Repeat measurements every 1-2 hours or more frequently if the patient is unstable.
• Interpret hematocrit levels in conjunction with other clinical signs, vital signs, and laboratory values to guide trauma management effectively.

Evidence-Based Practice

• The recommendation to maintain a hematocrit level between 21% and 30% is based on the highest quality evidence available, including the Surviving Sepsis Campaign guidelines 1 and other studies 1.

From the Research

Hematocrit Levels in Trauma Patients

• The optimal hematocrit level in trauma patients is a topic of debate, with various studies suggesting different values 2, 3, 4, 5.
• A study published in 1996 suggested that maintaining hemoglobin or hematocrit values around 11 g/dl or 33%, respectively, is one part of therapeutic interventions to improve survival in critically ill patients 2.
• Another study from 1987 found that patients with hematocrits maintained near 30% or 40% had no significant difference in cardiac index, heart rate, systemic vascular resistance, or left ventricular stroke work index, but oxygen delivery was lower at the lower hematocrit 3.
• A 2008 study on massive transfusion in trauma patients found that tissue hemoglobin oxygen saturation predicts poor outcome, but did not specify a particular hematocrit level 6.
• Optimum hematocrit levels are probably between 30% to 40%, according to a 1988 study on blood flow to organs in critical illness 4.
• A 1992 study suggested that the "critical hematocrit" differs from patient to patient, and that a hemoglobin or hematocrit within the normal range constitutes a natural buffer against encroachments upon the oxygen supply from non-Hb causes 5.

Key Findings

• Hematocrit levels between 30% to 40% are often cited as optimal in trauma patients 3, 4.
• Oxygen delivery is lower at hematocrit levels of 30% compared to 40% 3.
• Tissue hemoglobin oxygen saturation is a predictor of poor outcome in trauma patients requiring massive transfusion 6.
• The "critical hematocrit" is an individual value that differs from patient to patient 2, 5.