Anemia

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