Anemia of Hospitalization - Pathophysiology Why does the Hgb/Hct drop in the first two days during hospitalization? Interestingly, anemia of hospitalization is commonly thought to be due to: phlebotomy, IVF invasive procedures/ bleeding etc. However, prolonged bed rest can contribute to a drop in your pts blood count! Another reason to get our patient's out of bed if possible! Until the mid-20th century, bedrest was considered a benefit that helped people heal. Hippocrates had already noted the risk of loss of muscle, bone and tooth (Chadwick and Mann, 1950). Today, there is recognition of bedrest’s negative effects on body and the blood volume. In WW2, when forced to mobilize quickly soldiers recovered more quickly from injuries and infections. Aeronautics research confirmed that prolonged immobility/weightlessness was detrimental to health, adversely affecting all major organs. Over 120 years ago, Ernest Starling demonstrated that fluids and other molecules move back and forward from blood to the extravascular space. This movement is determined by the balance between hydrostatic and oncotic pressures acting within capillaries and interstitial spaces. In 1928, a 32-page long paper in the Journal of Clinical Investigation ( https://www.ncbi.nlm.nih.gov/pmc/ar ) elegantly demonstrated that total plasma volume decreases on average 11% after 30 min standing still, compared to the recumbent position, and that hematocrit increased proportionally. 30 years later, another study described a decrease in plasma volume of 10.8% (equivalent to around 500 mL in a 70 kg adult) after 15 min. This change was completely reversed after lying down again, with a mean increase in total plasma volume of 12.5% in healthy subjects. These shifts of total plasma volume were accompanied by inverse changes in hematocrit, which increased 6.6% after one hour of standing, and decreased 7.0% after resuming the horizontal position. ( https://www.ncbi.nlm.nih.gov/pmc/ar ) Other reasons for Hg drop on the first hospital day was due to admission phlebotomy/ blood work, hemoconcentration/volume depletion in acutely ill people, and the initiation of IVF ( https://www.ncbi.nlm.nih.gov/pmc/ar ) Therefore, the knowledge that up to 30% of variations in total plasma volume can be attributed solely to lying down should certainly influence our posture and our reasoning during clinical evaluations. In conclusion, prolonged rest can cause a Hg drop and contribute to anemia of hospitalization. Unfortunately, even today, patients aged 65 years and over can spend 71-83% of their time in hospital lying down (Fox et al, 2018). It's time to end this ‘pajama paralysis’! Postural Pseudoanemia: • Postural pseudoanemia is a normal physiological response to a change in position from standing to lying • A patient’s plasma volume can increase with lying down and can cause a 3-6% drop in Hg/Hct in the first 2 days of hospitalization • Changes in posture can lead to substantial changes in hematocrit, which may be attributed mistakenly to blood loss or acute anemia and may result in a cascade of unnecessary diagnostic costs Lying Down: • Increase movement of water and other diffusible solutes through the capillary wall into capillary • Volume increases 11% after 30 min and Hg/Hct decreased Standing: • Increased hydrostatic pressure and decreased plasma volume by 11% thus concentrating Hg/Hct Other Explanations for Decrease of Hg/Hct During Hospitalization: Mechanisms: • Admission phlebotomy • Hemoconcentration/volume depletion - corrected with hydration • Initiation of IV hydration • Blood loss due to invasive procedures • Iron, folic acid, cobalamine deficiencies • Renal, liver, or endocrine issues • Anemia of inflammation • Anemia of renal disease • Blood discarded from accessing port caths, PICC, and mid lines Drop in Hg was 1.45g/dL between days 3-4 due to issues other than GI bleeding in general ward patients #Anemia #Pseudoanemia #Hospitalization #causes #pathophysiology #differential #diagnosis
