D. JOHN DOYLE, MD, Ph.D., FRCPC UNIVERSITY OF TORONTO / THE TORONTO HOSPITAL
Although much has been made about a medical rethinking of the risk/benefit properties of blood transfusions as a result of HIV and AIDS, blood transfusions remain essential to life in a large number of clinical situations. Patients who refuse a blood transfusion deemed absolutely medically necessary by a physician put themselves at risk of dying from severe anemia. For example Carson et al. studied 125 surgical patients who were Jehovah’s Witnesses and thus refused blood transfusion. It was found that over 60% of patients whose preoperative hemoglobin fell below 6 g/dL died following the surgery. [1] Full data is given below:
| Preoperative Hemoglobin | Mortality |
| < 6 g/dL | 61.5% |
| 6.1- 8 g/dL | 33% |
| 8/1-10 g/dL | 0% |
| > 10 g/dL | 7.1% |
When is a transfusion “necessary?” A reasonable answer might be whenever failure to transfuse puts the patient at “high risk” of injury when transfusion itself is not highly risky. For example, if the risk of getting a heart attack (myocardial infarct) or stroke (cerebrovascular accident) or similar complication from severe anemia is, say, 15% while the risk of transmitting a blood borne pathogen is, say, 0.5%, many physicians would regard the risk/benefit ratio as quite acceptable. However, in real life specific numbers are generally not available, which is why in practice one must rely on clinical judgement and published guidelines. For example, Carson (American Journal of Surgery 1995;170(6A supp): 325) suggests that patients with cardiopulmonary disease should have their hemoglobins kept at or above 10 g/dL while otherwise health patients should be kept at or above 7 g/dL (see full chart below).
| Keep Hb > 10 g/dL | Keep Hb 7-10 g/dL |
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| SummaryPatients should ordinarily have their hemoglobin maintained above 7 g/dL if they are healthy, with a threshold of 10 g/dL applying in patients with significant cardiopulmonary disease. Should a severely anemic patient undergo surgery without blood, the mortality rate is high (over 60% mortality rate for patients with a preoperative hemoglobin below 6 g/dL). |
1 Lancet 1988 Apr 2;1(8588):727-9 Severity of anaemia and operative mortality and morbidity. Carson JL, Poses RM, Spence RK, Bonavita G. Department of Medicine, University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School, New Brunswick.
“In a case-control study of 125 surgical patients who declined blood transfusions for religious reasons operative mortality was inversely related to the preoperative haemoglobin level, rising from 7.1% for patients with levels above 10 g/dl to 61.5% for those with levels below 6 g/dl. Mortality rates were also related to blood loss during surgery, rising from 8% for patients who lost less than 500 ml to 42.9% for those who lost more than 2000 ml. Both preoperative haemoglobin level and operative blood loss should be considered in assessing the need for preoperative transfusion. In our study no patient with a haemoglobin level above 8 g/dl and operative blood loss below 500 ml died.”
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