When the Cure Contributes to the Problem: Iatrogenic Anemia in Critical Care

In the intensive care unit, we often reach for blood tests as our window into the body’s response to critical illness. But what happens when the very tests we order begin to chip away at the patient’s ability to recover?

Iatrogenic anemia—anemia caused or worsened by medical intervention, particularly diagnostic blood draws—is a well-documented but underappreciated complication of hospitalization, especially in critically ill patients. And while transfusion can be life-saving, it comes with its own risks, costs, and carbon footprint. Preventing the anemia in the first place is often safer, cheaper, and more sustainable.

The Scope of the Problem

In one large observational cohort from a U.S. academic medical center, critically ill patients underwent a median of 41 laboratory draws per hospitalization, with a median blood loss of 232 mL per patient—about half a unit of red cells (Luke et al., 2023). Daily losses in some ICUs approached 29 mL, and discard volumes—blood drawn but not analyzed—accounted for more than 10% of this loss.

The consequences are not benign. Hemoglobin levels decline in proportion to phlebotomy intensity, and each 100 mL of blood drawn was associated with a 1.15x increase in red cell transfusion use. Patients with the highest cumulative blood loss had the lowest nadir hemoglobin values, longest hospital stays, and highest transfusion requirements.

In neonatal ICU patients, the burden is even more staggering: up to 90% of circulating blood volume can be removed in the first two weeks of life alone (Widness et al., 1996).

Strategies to Reduce Iatrogenic Blood Loss

Patient Blood Management (PBM) strategies focus on three pillars:

1. Optimizing anemia management

2. Reducing iatrogenic blood loss

3. Enhancing tolerance of anemia

   
   

This post focuses on the second pillar—particularly blood-sparing techniques like:

• Small volume tubes (SVT)

• Closed blood sampling devices (CBSD)

• Point-of-care testing (POCT)

• Educational and policy interventions

• Bundled strategies combining the above

  
  

Systematic reviews consistently show that SVT and CBSD both reduce blood draw volumes, but the data are mixed regarding their ability to reduce transfusion rates or prevent hemoglobin decline (Whitehead et al., 2019; François et al., 2022; Keogh et al., 2023). The most substantial blood conservation has been achieved through CBSD, which returns unused blood to the circuit, eliminating discard volume altogether.

Yet one tool in particular—point-of-care testing—offers an especially compelling combination of blood conservation, clinical responsiveness, and workflow efficiency.

Point-of-Care Testing: High Impact, Low Volume

Unlike conventional lab draws, POCT uses minimal sample volumes—often 100–250 µL—and delivers results in minutes. While often framed as a convenience tool, POCT may play a crucial role in blood conservation strategies.

In a NICU cohort, Madan et al. found that switching to a bedside POCT analyzer for blood gas and electrolyte testing resulted in a 46% reduction in transfusions and a 43% reduction in total transfused volume among extremely low birth weight infants (Madan et al., 2005). Notably, the frequency of testing remained unchanged, suggesting the volume savings alone made the difference.

Mahieu et al. similarly observed a 48% reduction in transfusion volume among very low birth weight infants following the introduction of a POCT analyzer (Mahieu et al., 2017). Blood loss per test was significantly reduced, and the intervention was cost-saving for the national health system.

In an adult ICU cohort, Salem et al. demonstrated that POCT instruments provided accurate analyte results while using only 250 µL of blood. They highlighted the role of microchemistry technology in reducing blood loss, particularly in high-acuity settings like emergency departments and operating rooms.

Despite differences in study populations and methodologies, these studies converge on one key finding: POCT can reduce diagnostic blood loss and transfusion needs without compromising care.

The Benefits and Risks of POCT

The benefits of POCT in critical care go beyond sample volume:

• Faster turnaround times allow more rapid clinical decisions.

• Less blood drawn per test reduces the risk of phlebotomy-induced anemia.

• Testing at the bedside minimizes pre-analytical errors (like transport delays or sample degradation).

• Capillary sampling options may eliminate the need for venipuncture entirely in some cases.

  
  

But there are trade-offs to consider:

• Differences between capillary and venous/arterial blood can affect interpretability, especially for certain analytes.

• Some devices have lower throughput and limited test menus compared to central labs.

• Repeat testing or confirmation may still be necessary, particularly for critical or unexpected values.

• Integration into clinical workflows—from staff training to EMR connectivity—requires planning.

  
  

POCT is not a replacement for central labs, but a complementary tool. When deployed strategically—especially in high-volume testing environments like the ICU—it offers a meaningful reduction in both blood volume drawn and time to actionable data.

Implementing Change: More Than Just Tubes

While no single intervention prevents iatrogenic anemia on its own, the evidence supports integrating POCT and other blood-sparing strategies into routine practice, especially for ICU patients with prolonged stays or at high risk of transfusion.

Barriers remain—cost, workflow adaptation, and concerns about test redundancy or accuracy—but as the data accumulate, so does the imperative to act. This is not just a patient safety issue; it’s also a sustainability issue. As one review noted, each routine lab test generates measurable carbon emissions, with full blood counts producing the equivalent of 770 meters of car travel (McAlister et al., 2022).

Conclusion

Iatrogenic anemia is not an inevitable side effect of ICU care—it’s a modifiable risk. By leveraging technologies like POCT, rethinking default test ordering, and aligning with PBM principles, we can reduce unnecessary blood loss, avoid transfusions, and improve outcomes for some of our sickest patients.

Because sometimes, doing less really is doing more.