Exceptional blood loss anemia is the loss of enough red blood cells to compromise sufficient oxygen delivery to the tissues in patients who cannot be transfused for medical or religious reasons. Medical reasons may include the threat of blood product incompatibility or concern for transmissible disease. Religious beliefs may prohibit the receipt of transfused blood products.
Red blood cells contain the respiratory pigment hemoglobin. Hemoglobin has the powerful ability to pick up oxygen as the red blood cells pass through the blood vessels of the lungs. Hemoglobin then off-loads oxygen into the tissues of the body’s organ systems. If plasma were the only vehicle to deliver dissolved oxygen, each 100 ml of blood flowing to an organ system would carry only 0.3 ml of gaseous oxygen. The consumption of oxygen by human tissues far exceeds this. For instance, for every 100 ml of blood which circulates through it, the kidney extracts approximately 2 ml of oxygen, the brain extracts approximately 6.5 ml of oxygen and the heart extracts 10.5 ml of oxygen.
In most instances, humans average 15 grams of hemoglobin per 100 cc of blood. Each gram of hemoglobin transports 1.34 ml of oxygen. This is in addition to the oxygen carried by plasma. Therefore, 100 ml of blood, containing 15 grams of hemoglobin, can carry approximately 20 ml of gaseous oxygen.
In the 1960s, the Dutch thoracic surgeon, Ite Boerema, demonstrated that one could transfuse piglets with a simulated plasma mixture of buffered normal saline (Ringer’s Lactate solution), dextrose and dextran. In this process, blood was removed from the blood vessels and the substitute liquid (without hemoglobin) replaced. He then pressurized the piglets in a hyperbaric chamber while the animals breathed 100 percent oxygen. By using pressurization, enough oxygen could be dissolved in the simulated plasma mixture to supply oxygen requirements of the tissues. This was enough to adequately sustain the animal. The animals survived and could be brought out of the chamber to be successfully transfused with their own blood.
As hyperbaric oxygen or even normal oxygen administered for long periods can become toxic, intermittent administration of hyperbaric oxygen is essential. This point has been demonstrated clinically by the American thoracic surgeon, George Hart. In 1974, he reported a series of 26 severe blood loss patients who were treated with hyperbaric oxygen as an alternative to otherwise disallowed red blood cell transfusions. The survival rate was 70 percent.
Alternative approaches include use of fluorocarbons or stroma-free hemoglobin. While potentially promising, these treatment solutions still pose uncertainties for their potential ability to unfavorably alter the immune system. While erythropoietin may be used to stimulate the bone marrow to produce red blood cells, hyperbaric oxygen therapy only complements its use in exceptional blood loss anemia.