In my last post, I waxed theoretical. I discussed the potential reasons for measuring serial hemoglobin or hematocrit levels and the limitations imposed by the rate of change in these values. I conjectured about how often they should be drawn.

And now, how about something more practical? How about some actual research? One of the more common situations for ordering serial hemoglobin draws is in the management of solid organ injury. The vast majority of the practice guidelines I’ve seen call for repeating blood draws about every six hours. The trauma group at the University of Florida in Jacksonville decided to review their experience in patients with liver and spleen injuries. They hypothesized that hemodynamic changes would be more likely to prompt changes in management than lab value changes.

They conducted a retrospective review of their experience with these patients over one year. Patients with higher-grade solid organ injury (Grades III, IV, V), either isolated or in combination with other trauma, were included. Patients on anticoagulants or antiplatelet agents, as well as those who were hemodynamically unstable and were immediately operated on, were excluded.

Here are the factoids:

• A total of 138 patients were included, and were separated into a group who required an urgent or unplanned intervention (35), and a group who did not (103)
• The intervention group had a higher ISS (27 vs 22), and their solid organ injury was about 1.5 grades higher
• Initial Hgb levels were the same for the two groups (13 for the intervention group vs 12)
• The number of blood draws was the same for the two groups (10 vs 9), as was the mean decrease in Hgb (3.7 vs 3.5 gm/dl)
• Only the grade of spleen laceration predicted the need for an urgent procedure, not the decrease in Hgb

Bottom line: This is an elegant little study that examined the utility of serial hemoglobin draws for determining the need for more aggressive interventions in patients with solid organ injury. First, recognize that this is a single-institution, retrospective study. This just makes it a bit harder to get good results. But the authors conducted a power analysis to ensure enough patients were enrolled to detect a 20% difference in outcomes (intervention vs no intervention). 

Basically, they found that everyone’s Hgb started out about the same and drifted downward by roughly the same amount. But the group that required intervention was defined by the severity of the solid organ injury, not by any change in Hgb.

I’ve been preaching this concept for more than 20 years. I remember hovering over a patient with a high-grade spleen injury in whom I had just sent off the requisite q6-hour Hgb as he became hemodynamically unstable. Once I finished the laparotomy, I had a chance to pull up the result: 11 g/dL! 

Humans bleed whole blood. It takes a finite amount of time to pull fluid from the interstitium to “refill the tank” and dilute the Hgb value. For this reason, hemodynamics will always trump hemoglobin levels for making decisions regarding further intervention. So why get them?

Have a look at the Regions Hospital solid organ injury protocol using the link below. It has not included serial hemoglobin levels for 18 years, since it was written. Take care to look at the little NO box on the left side of the page.

I’d love to hear from anyone who has also abandoned this little remnant of the past. Unfortunately, I think you are in the minority!

Reference: Serial hemoglobin monitoring in adult patients with blunt solid organ injury: less is more. J Trauma Acute Care Open 5:3000446, 2020.