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Anemia is a topic covered in the Pocket ICU Management.

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First Things First (assess & treat for the following)

  • Prevalence in critical care is so common (>90%) that volume status or polycythemia should be considered in a pt with “normal” Hct.
  • At least 2 large-bore IVs, fluid resuscitation and blood products
  • Find source.
  • Recent guidelines suggest transfusion for Hb < 7 mg/dL.
    • This threshold may be lower for active ischemic heart disease in older pts.
    • Each case needs to be uniquely considered based on clinical presentation.
  • Look at palms/soles; if creases are lighter than skin, the Hb is usually < 8 mg/dL.
  • When lower GI blood loss is noted, insert NGT to determine if upper source exists.
    • Make sure bile or blood is noted in NGT output before pulling tube.
  • Development of anemia while in the ICU is most often a combination of blood loss, followed by anemia of acute inflammatory illness.
    • ICU pts lose on average 25-50 mL/day of blood from iatrogenic causes.
    • The greatest amount of diagnostic blood loss occurs on the day of admission (~30-70 mL). This amounts to ~15-20% of total blood loss per unit stay.
    • Average loss from arterial catheter sampling alone is ~900 mL.
    • Pts with normal H/H on admission can develop “anemia” if volume resuscitated.
    • 70% of pts admitted have baseline Hb < 12 mg/dL (mean ~11).
    • 30% of these will have Hb < 10 mg/dL at admission.
    • Mean Hb of average ICU pts who received transfusion is ~8.5 mg/dL.
    • Of those who received transfusion, LOS increased ~5 days.
    • 85% of pts with ICU LOS >7 days receive at least 1 unit of PRBCs.
  • Check OR reports and records for I/Os.
  • Intraoperative blood loss is usually poorly estimated and should be used only as an estimate in resuscitation of a patient. Treat the anemia and the pathophysiologic state, not the stated blood loss.
  • Check OR, trauma, and procedural records for IOs, type of resuscitation fluids.
  • In anemia, reticulocyte index (RI) or reticulocyte production index (RPI) should be ≥2-3% if adequate synthetic function and substrates are intact.
    • This is not your standard reticulocyte count (see below).
  • Technical definition for anemia is reduction 2 SD below mean.
    • Female < 12 mg/dL; HCT < 36%
    • Male < 13.5/; 41%
    • WHO: < 13 in males, < 12 in females
  • Range in normal allows for unrecognized blood loss.
    • With a normal Hb of 13.5-18 mg/dL, a pt can lose 2-4 grams of blood (reduction in Hct by 6-15%, 750 mL) and still have “normal” levels.
  • NHANES II group also considers race in definition of anemia.
    • Black male: < 12.7 mg/dL; female: < 11.5
  • Remember that “normal” is not always “normal”:
    • Pts with chronic hypoxia should have secondary polycythemia.
    • H/H may be surreptitiously elevated in first few hours of acute blood loss.
    • Blood pressure for pts with HTN may be “normal,” but not for them.
    • Pts living in high-altitude regions should have higher H/H.
    • Although there is concomitant increase in RBC mass, pregnant patients will have lower H/H (25-50%) secondary to expanded plasma volume, depending on gestational age.
    • Lower H/H seen in hypervolemic states like CHF, cirrhosis, nephrotic syndromes or iatrogenic dilutional effects
  • Anemias that prompt ICU admission and anemias prompted by ICU admission can have distinctly different approaches.
    • Pts admitted with anemia usually have defined diagnoses, treatments, and prognoses.
    • Pts whose anemia develops in the ICU often have complicated differentials and multiple confounding factors.
  • Most common causes prompting admission to critical care for anemia are blood loss-related:
    • GI bleed, trauma, OB/GYN
    • Followed by anemias from malignancies, bleeding disorders, marrow failure
  • Most common causes of anemia prompted by ICU admission are acute/subacute blood loss, hemolysis, phlebotomy and medications.
  • Look for hidden blood loss (anatomical anemia): retroperitoneal bleeds from procedures involving femoral vessels, hemothorax from procedures and trauma, esp in pts on anticoagulation.
  • Intracerebral hemorrhage does not cause significant anemia.
  • Low MCV (Hypochromic, Microcytic)
    • Acute inflammatory
    • Chronic disease
    • Iron deficiency (blood loss predominate, acute inflammation of SIRS)
    • Thalassemias
    • Lead intoxication
    • Sideroblastic anemia
    • Hemoglobinopathies
  • Normal MCV (Normochromic, Normocytic) (by retic count)
  • Low Retic % (< 3%): Assumes marrow failure
    • Infection/inflammation > acute blood loss with dysfunctional erythropoiesis > drugs > renal disease > hypoplastic anemia, malignancy, spleen sequestration
  • High Retic % (>3%): Assumes marrow functional 
    • Acute blood loss, bleeding disorders, DIC
    • Pathologic Hb (G6PD, PKD, spherocytosis, sickle cell)
    • Hemolysis: autoimmune and microangiopathic diseases, mechanical shear from heart valves and pumps
  • Macrocytic (High MCV)
    • Megaloblastic disease (B12, folate, meds)
    • Normoblastic (hypothyroid, myelodysplasia, aplastic states)
  • Patients with cirrhosis, HIV/AIDS and other chronic diseases may have a low MCV (microcytic) anemia from poor nutrition or chronic blood loss; normocytic anemia from chronic illness and sequestration, low erythropoietin levels; or macrocytic from B12, folate deficiency, malabsorption and medications.
  • Zieve’s syndrome: severe alcoholic hepatitis with hemolytic anemia, spur cells and acanthocytes

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Last updated: April 17, 2010


"Anemia." Pocket ICU Management, PocketMedicine.com, Inc, 2010. Anesthesia Central, anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534093/all/Anemia.
Anemia. Pocket ICU Management. PocketMedicine.com, Inc; 2010. https://anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534093/all/Anemia. Accessed April 20, 2019.
Anemia. (2010). In Pocket ICU Management. Available from https://anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534093/all/Anemia
Anemia [Internet]. In: Pocket ICU Management. PocketMedicine.com, Inc; 2010. [cited 2019 April 20]. Available from: https://anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534093/all/Anemia.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Anemia ID - 534093 Y1 - 2010/04/17/ BT - Pocket ICU Management UR - https://anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534093/all/Anemia PB - PocketMedicine.com, Inc DB - Anesthesia Central DP - Unbound Medicine ER -