Friday, January 20, 2012

Iatrogenic Anemia - The Hospital Vampire Saga

The gist:  Healthcare professionals in hospitals draw excessive blood for most tests that are ordered on inpatients.  This may cause iatrogenic anemia in an already vulnerable population.  Thoughtful ordering, proper nutrition and adjunct support, as well as use of small volume or pediatric tubes may mitigate this problem.

We draw copious quantities of blood in the hospital, apparently enough to actually make patients anemic.  As a medical student, I likely fall into the category of worst offenders (feeling particularly guilty when I recall ordering serial C-reactive proteins for a particular pediatrics attending); however, there are very real complications of ordering these tests.  As a public health student, I nearly always feel compelled to advocate for less testing.  However, although I discourage redundant testing that is not likely to change management for a patient, my nerdy curiosity is often not sated without absolutely knowing certain things about patients (be it the trend of their creatinine or their anti-proteinase3/anti-myeloperoxidase status...depending on the patient, naturally).  Thankfully, there is another solution to the problem of anemia caused by excessive blood draws in the hospital!

What's the actual problem?
  • A study published in the Annals of Internal Medicine (2011) of 17, 676 inpatients in 57 US hospitals demonstrated an incidence of moderate to severe hospital acquired anemia in 20% of acute myocardial infarction (AMI) inpatients that was independently associated with phlebotomy.
    • This is especially concerning in AMI patients when we remember that Cardiac Output (CO) is the product of Stroke Volume (SV) and Heart Rate (HR).  With intravascular volume depletion, the HR will increase to maintain CO.  Thus, in patients with AMI, the already damaged myocardium is having to work much harder (and potentially getting less oxygenation).  Furthermore, the decreased hemoglobin may lead to decreased oxygen delivery to tissues...all bad things in AMI patients (and sick patients in general). 
    • Note:  The studies I found don't track morbidity/mortality outcomes in these patients who get hospital acquired anemia, rather this is inferred in a rather unscientific yet logical way by assuming we often treat people who get anemic with blood transfusions (which have side effects) or by extrapolating existing literature documenting the morbidity/mortality associated with anemia in inpatient/sick populations.
The Simple Solution
  • Order only necessary tests and order blood draws together
  • Ensure the patient is nutritionally set up for success (iron, no GI bleeding, etc)
  • Pediatric Tubes
  • Small Volume Tubes (SVT)
    • Studies have repeatedly demonstrated that the SVTs and pediatric tubes provide ample blood quantity for nearly all tests ordered (most studies are of ICU patients)
    • These studies also demonstrate that this is effective in reducing the total volume of blood lost from the patient to a degree of statistical significance.
      • Sanchez-Giron paper in 2008 demonstrated that blood loss from lab testing was reduced by 73% per patient (on average) through the use of SVTs (n = 227), although the interquartile range was rather large (2.3-10.9 mL in the ICU cohort) and the methodology and reporting of their statistics is a little...murky.  However, their reports are in line with many other studies.
The Down Side
  • SVTs may require special laboratory equipment/adaptations
References:
Adam C. Salisbury, MD, MScKimberly J. Reid, MSKaren P. Alexander, MD; et al Diagnostic Blood Loss From Phlebotomy and Hospital-Acquired Anemia During Acute Myocardial Infarction Arch Intern Med. 2011;171(18):1646-1653. doi:10.1001/archinternmed.2011.361
Jane C. Dale and Stephen G. Ruby (2003) Specimen Collection Volumes for Laboratory Tests. Archives of Pathology & Laboratory Medicine: February 2003, Vol. 127, No. 2, pp. 162-168.
Francisco Sanchez-Giron and Francisco Alvarez-Mora.  Reduction of Blood Loss From Laboratory Testing in Hospitalized Adult Patients Using Small-Volume (Pediatric) Tubes. Archives of Pathology & Laboratory Medicine: December 2008, Vol. 132, No. 12, pp. 1916-1919.
Fowler RABerenson M.   Blood conservation in the intensive care unit. Crit Care Med. 2003 Dec;31(12 Suppl):S715-20.
Chant, C. , G. Wilson , and J. O. Friedrich . Anemia, transfusion, and phlebotomy practices in critically ill patients with prolonged ICU length of stay: a cohort study. Crit Care 2006. 10:R140.

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