QUESTIONS AND ANSWERS 101

were nine cardiac arrests. The total incidence of arrest in the patients receiving cold blood was 58.3 per cent. In 118 comparable patients receiving warm blood, there were only eight cardiac arrests (6.8 per cent).-E. W. S.

EXTRACORPOREAL CIRCULATION

Chemical and Hypothmic Inhibition of Intra- vascular Sludging in Extracorporeal Cir- culation. D. Sachs, G. H. Derry, D. Krum- haar, W. H. Lee, Jr. and J. V. Maloney, Jr. Department of Surgery, University of California Medical Center, Los An- geles. Ann. Surg. 160: 183, 1964.

THE authors contend that intravascular ag- gregation of erythrocytes (sludging) during extracorporeal circulation results from denatu- ration of plasma protein at an air-blood inter- face and subsequent coating of red cells with the denatured protein. An attempt was made to inhibit sludging by hypothermia and by the addition of various substances to the blood. Since profound hypothermia itself proved to produce severe degrees of sludging, it did not appear beneficial in this respect. Low molec- ular weight (40,000) dextran, Albumisol, Plas-

manate. and ascorbic acid appeared to be effective in preventing sludging, but their in- fluence was incomplete and transient.

The authors suggest that a more fruitful approach to prevention of protein denaturation and sludging lies in the design of new oxygen- ators which do not contain an air-blood inter- face.-E. W’. S.

The Prophylactic Use of Fresh Frozen Plasma aft= Extracorporeal Circulation. A. S. Trimble, J. J. Osborn, W. J. Kerth and F. Gerbode. Department of Surgery, Presbyterian Medical Center, San Fran- cisco, California. J. Thor. Cardiov. Surg. 48: 314, 1964.

IN PATIENTS who received fresh frozen plasma prophylactically (adults: 500 ml; children: 250 ml) after various open heart operations, the average postoperative blood loss was equivalent to that in a control group. The authors con- clude that such prophylactic use of fresh frozen plasma is of no value and suggest instead that patients in whom bleeding becomes excessive should be thoroughly investigated and given specific treatment.-E. W. S.

Questions and Answers

Mental Patients as Blood Donors Q. “I would like to have a legal opinion con-

cerning the use of the inmates of a mental insti- tution as blood donors.”-M.D., Bay City, Mich- igan

A. “I do feel it in order to note substantial legal objections to the use of these patients as donors. “As you know, except in extraordinary circum-

stances, any penetration of the tissues must be with the patient’s consent, express or implied. Penetration in the absence of consent will con- stitute assault and battery.

“As a general rule, a person whose mental condition is such that he is unable to exercise normal capacities of will and reasoning cannot grant binding consent. A release or consent executed by such a person is. at best, voidable.

“It is true that physicians attending the men- tally ill are empowered to penetrate the tissue without the patient’s consent. However, even in these circumstances, consent has been ob-

tained from a responsible relative or appro- priate court. I do not feel that the blanket consent to treat a patient includes the right to draw blood, when the drawing of blood is of no benefit to the patient.

“The mental patient may void and withdraw his prior consent to the drawing of his blood, alleging his mental condition. He may also urge that his consent was obtained through duress or unlawful advantage exercised by the persons charged with his care and custody. Either ground of avoidance would enable him to bring a civil action for assault and battery. Those persons who authorized or participated in the drawing of blood may thus be liable to the patient. Additionally, those persons who en- couraged, incited, aided, or abetted the act may also be liable. The liability of these indirectly-involved individuals may also be predicated on the conspiracy theory.

“For these reasons, and medical considera-

QUESTIONS AND ANSWERS 102

tions aside, I must advise against the participa- tion of the mental hospital patients in the hos- pital employees’ blood bank program.”-How- ard Hassard

RCF Used in Blood Bank Procedures Q. “We have noted that speeds of 1,000-2,000

rpm are specified for the various blood bank procedures in ‘Technical Methods and Proce- dures.’ The New York State Department of Health, in its ‘Methods for Approved Labora- tories,’ recommends speeds of 500-1.500 rpm (calculated rcf 50-440). In most instructions the relative centrifugal force (rcf) is not given. This is confusing and inaccurate considering the variety of centrifuges in use. Your sug- gestions will be appreciated.”-M.D., Middle- town, New York A. “Your question is highly pertinent. I fully

agree that there exists an extraordinary state of confusion and a multitude of discrepant state- ments throughout the literature on centrifuging speed and time in relation to the type of centri- fuge used.

“The problem can be stated in very simple terms. It is desired to apply a centrifugal field for the optimal period of time required to pro- duce complete sedimentation of red cells in a cell-serum mixture without permitting the de- velopment of nonspecific cohesion between the cells. Failure to achieve optimal conditions will lead, on the one hand, to the red cells not being brought into close proximity and. on the other .hand, to a degree of nonspecific cohesion which will require strong forces to redisperse the cells. Of the two possible extremes, the latter is both dangerous and undesirable. ‘Over-spinning’ is one of the most frequent causes of failure to observe minor degrees of specific agglutination because the amount of shaking necessary to dislodge the cells from the bottom of the tube also serves to break up the agglutinates. Fur- thermore, an ‘underspun’ tube is quite obvious even to the eye of a novice but an ‘overspun’ tube is by no means as apparent, even in ex- pert hands.

“Relative centrifugal force (rcf) can be easily calculated from the following equation:

rcf = r n* x 1.18 X 10-5 where: r = radius to tip of tube in centimeters

“This equation does not give any information as to the rate at which a suspension is packed in a given centrifugal field. The principal parameters regulating this phenomenon are as follows:

n = revolutions per minute

1. The ratio of specific gravity between the dispersion medium and the dispersed phase.

2. The viscosity of the dispersion medium. 3. The volume-ratio of the dispersion medium

4. The mass/surface area ratio of the dis-

5. The ‘angle effect’ which is a special case

“As you can see, the calculation of optimal conditions for centrifugation for various cell- serum mixtures, although possible, would be very laborious and, therefore, the problem is best solved by iterative rather than computa- tional measures.

“I strongly believe that each laboratory should calibrate its own centrifuges. This is best done by recognizing, first of all, that the cell-serum mixtures which are to be centrifuged fall into various classes according to the param- eters defined above. For instance, a high pro- tein suspension of cells such as the ‘1, 2, 3’ mixture consisting of one part of 2 per cent cell suspension, two parts of patient’s serum and three parts of 30 per cent albumin will require different centrifuging times and speeds from the Coombs test in which the cells are suspended in a medium of low viscosity and specific gravity. If your laboratory habitually uses two or three main categories of cell-serum mixtures you may then proceed to determine, for each category of mixture, the mininium cen- trifuging time necessary to produce a clear supernatant. If the centrifuges are of the variable-speed type, the speed control should be set to produce a rotational velocity equivalent to 50-1,000 xg. The exact value is unimpor- tant but it must be reproduced each time the centrifuge is used and you should bear in mind the power function relationship between angu- lar velocity and rcf as defined in the above equation, i.e., twice the speed produces four times the rcf. As a general rule, angle-head centrifuges will be found to require about half the spinning time of horizontal head types. In making the calibration, be sure to use cell- serum mixtures in which agglutination will not occur since agglutinated cells sediment at a substantially higher rate than unagglutinated cells in a centrifugal field.

“I do hope this information is helpful to you. You will be interested to hear that the new AABB Technical Manual will have a section on this topic.”-A. Richardson Jones, M.D.

to the dispersed phase.

persed phase.

of the previous parameter.

QUESTIONS AND ANSWERS 103

Mixing Blood with Glucose Solutions Q. “In our hospital a few physicians start the

I.V. with glucose and then administer a unit of blood. What is your opinion about the effect of glucose solutions on red cells? Is it a possible explanation for ‘allergic’ reactions? What is the effect of glucose in physiologic saline solution on administered red cells?”-M.D., Michigan

A. “It is not advisable to mix whole blood transfusions with various types of glucose and water in saline solutions. If, for example, one part of whole blood is mixed with three parts of quarter strength saline and 5 gmo/, dextrose and allowed to stand at room temperature in vitro at least one hour, the survival of the red cells will be reduced to levels of approximately 20 per cent and it is possible for hemoglobinuria and hemoglobinemia to result. The results of mixing whole blood with 5 per cent glucose and normal saline do not apparently lead to decreased survival when exposed prior to trans- fusion for three hours at mom temperature. However, since this represents a markedly hyper- tonic solution causing a significant decrease in the red cell volume while in vitro with subse- quent rapid swelling after transfusion, it is not desirable on theoretical grounds to expose red cells to such osmotic trauma before transfusion. In general it is ill-advised to mix whole blood with any type of glucose solution before trans- fusion, since even though glucose crosses the red cell membrane, it does so much more slowly than does water. Therefore, in the concentra- tion ordinarily employed in intravenous solu- tions, it is an osmotically active substance.”- Franklin G. Ebaugh, Jr., M.D.

Use of Cde and cdE Blood for cde Recipients Q. “If a donor blood tests as D negative and

CD positive and, additionally, as strongly posi- tive with anti-C, may one safely assume that such blood does not carry the G antigen? Con- versely, if a donor blood is D negative and CD positive but reacts negatively or weakly with ant ic , may one assume that the antigen is pre- sumably G? What I am trying to determine is whether one can salvage most of the CD posi- tive bloods and safely use them in Rh negative recipients. If such recipients have anti-C plus

D. is this presumably chiefly anti-G or is there some admixture of pure anti-C? It has been proposed that those bloods which react strongly with anti-C may be indiscriminately used as Rh negative donor blood with little regard on a statistical basis for the G antigen, which I know is a potent antigen. This question may sound like a chestnut but it assumes some importance on our obstetrical service where about six 0, Rh-negative bloods are transfused yearly without a crossmatch. We have never paid any attention to the E antigen and I wonder if we can be as tolerant of the CD anti- gen under these circumstances.”-M.D., Boston, Massachusetts

A. “The answer to your first question is ‘no.’ If a person is C-positive you can assume that he is G-positive. There are no known exceptions up to the present time, although one person has been found who is D-positive, G-negative.

“The answer to your second question is ‘yes.’ If he is positive with anti-CD but negative or weak with ant ic , you can assume that he is G-posi tive. “So far as using G-positive bloods for Rh-

negative recipients, I don’t think there is quite enough information to give a very intelligent answer. I think somebody needs to give a large series of such bloods and see what happens. Until there is more information I certainly would hesitate to give bloods that were known to be G-positive to Rh-negative young women. There are a few cases on record of erythro- blastosis caused by anti-G alone, but there are a good many cases of course in which women have anti-D plus anti-G, the anti-G usually being in much lower titer than the anti-D. My feeling is that G is probably not sufficiently antigenic to worry much about even in women, but as I say more data must be collected.

“People who are sensitized to Rh and have what looks like anti-C plus D most often have anti-D plus anti-G; less often they have anti-D plus G plus C, sometimes they have anti-C plus anti-D and no anti-G and rarely they have anti-G alone. “You certainly don’t need to pay attention

routinely to the E antigen in either Rh-negative or Rh-positive donors.”-Fred H. Allen, Jr., M.D.