The whole blood volume is used as a general guide in estimating reasonable volumes of blood that can be removed safely.
The table below shows values for mean blood volume in children, men and women (Geigy Scientific Tables, 7th Ed; 1971):
|Whole Blood Volume||(ml/kg Body Weight)|
|Newborn, 15-30 minutes of age||76.5|
|Newborn, 24 hours||83.3|
|Children, 3 months||87|
|Children, 6 months||86|
|Children, 1 year||80|
|Children, 6 years||80|
|Children, 10 years||75|
|Children, 15 years||71|
Blood banks consider that 7-9% of whole blood volume can be removed safely on a single occasion in a person in good health and with a hematocrit level not less than 38 volume%. For this purpose, guidelines have been developed that are based on body weight, starting at 41 lb. Available data suggest that similar criteria can be applied also to children weighing less than 41 lb, and to infants and newborn.
The IRBMED has modified and extended the criteria of blood banks, and recommends that they be followed in removing blood from human subjects for research purposes:
1. In human subjects in good health, and a hematocrit of not less than 38 volume%, the following volumes of blood may be removed over a 3-month period, on a single occasion or in divided portions:
Body Weight (lb) Blood Volume (ml) 0-10 20 11-20 30 21-30 50 31-40 100 *41-51 164 *52-63 214 *64-74 260 *75-85 308 *86-97 355 *98-109 403 *>110 450
Body Weight (kg) Blood Volume (ml) 0-5 20 6-10 30 11-15 50 16-20 100 21-25 150 26-30 200 31-35 250 36-40 300 41-45 350 46-50 400 >50 450
* Specified by Blood Banks
2. Additional volumes of blood may be removed in subsequent 3-month periods using the same criteria, as long as the subject remains in good health and maintains a hematocrit level of not less than 38 volume%.
3. If a subject may not be in good health, and in particular may have a cardiovascular, pulmonary or hematopoietic problem, the volume of blood to be removed should be reduced appropriately.
4. If the study protocol necessitates that the volume of blood to be removed exceeds the above criteria recommended for subjects in good health, or that the volume cannot be reduced in consideration of poor health or low hematocrit level, IRBMED may consider approving the project only if the added risk can be justified by the expected direct benefit to the subjects.
5. Whenever the volume of blood to be removed will exceed 1% of whole blood volume of the subject, hematocrit should be determined in advance, to ascertain that it is not <38%. The frequency of monitoring hematocrit levels should be commensurate with the volume of blood to be removed, and the estimated vulnerability of the subject to blood loss.
6. The estimated volume and frequency of blood to be removed, risks associated with blood removal, and the measures to be taken to minimize those risks should be included in the information to be given to the subject in a written informed consent document.