Tag Archives: hematocrit

Does Initial Hematocrit Predict Shock?

Everything you know is WRONG!

The classic textbook teaching is that trauma patients bleed whole blood. And that if you measure the hematocrit (or hemoglobin) on arrival, it will approximate their baseline value because not enough time has passed for equilibration and hemodilution. As I’ve said before, you’ve got to be willing to question dogma!

The trauma group at Ryder in Miami took a good look at this assumption. They drew initial labs on all patients requiring emergency surgery within 4 hours of presentation to the trauma center. They also estimated blood loss in the resuscitation room and OR and compared it to the initial hematocrit. They also compared the hematocrit to the amount of crystalloid and blood transfused in those areas.

Patients with lower initial hematocrits had significantly higher blood loss and fluid and blood replacement during the initial treatment period. Some of this effect may be due to the fact that blood loss was underestimated, or that prehospital IV fluids diluted the patient’s blood counts. However, this study appears sound and should prompt us to question the “facts” we hear every day.

Bottom line: Starling was right! Fluid shifts occur rapidly, and initial hematocrit or hemoglobin may very well reflect the volume status of patients who are bleeding rapidly. If the blood counts you obtain in the resuscitation room come back low, believe it! You must presume your patient is bleeding to death until proven otherwise.

Reference: Initial hematocrit in trauma: A paradigm shift? J Trauma 72(1):54-60, 2012.

AAST 2011: The Initial Hematocrit Matters

Traditional teaching is that we bleed whole blood, and it takes time to pull volume out of the interstitial space to replace it. Therefore, the initial hematocrit should be normal when a fresh, bleeding trauma patient rolls through the doors.

An observation I have made over the years is that this is not necessarily so. A few patients have low initial hemoglobin or hematocrit readings, and they tend to be bleeding briskly from somewhere. A paper to be presented at next week’s AAST meeting in Chicago shows just that.

The authors retrospectively reviewed 198 trauma patients requiring emergency surgery at a Level I trauma center. Patients with lower initial hematocrits tended to have lower systolic blood pressure, lower GCS, lose more blood, and require infusion of more blood products during surgery. They also had a higher ISS and mortality. The biggest jump in these indicators occurred when the Hct dropped below 37.

Bottom line: A low hematocrit on the first blood drawn during trauma resuscitation is more helpful that previously thought. Be sure to check those lab values early, and if the hematocrit value is in the mid-30s or lower, start looking for significant sources of bleeding.

Reference: The initial hematocrit matters in trauma: a paradigm shift? AAST 2011 Annual Meeting, Paper 38.