Document 8VmJjO0EDR4Go00vkLrnQ9Vga

Jtme 15* mi Dr.Kenneth D# Blackfan Harvard Medical School Childrenfs Hospital JOO Longt?God Avemi Boston, Mass. Dear Doctor Blackfan* I have at present a considerable mass of data which Have been accumulating ovdr a period of a year or more, and which I am non ready to work up* When I have completed the study of these data, ! shall be able to answer the question in your letter of June ?th more accurately than I can do offhand* As to the lead concentrations in the blood of normal poisons, and in persons exposed to lead, I am sure I shall be able to give you very satis factory figures* I am not quit so certain in the case of the spinal fluid for we have: not studied enough either normals or exposed to be quite sure of the range of varia bility. The blood levels of normal persons range from *01 to *05 milligrams per 100 graas of blood# The mean is somewhere between *02 and *055 {Some time ago we published figures slightly higher than these, but sine m have been studying samples obtained only by ourselves and analysed in a laboratory which is free of outside atmospheric air, we have found the figures to be slightly lower#) 1 have a large enough series of results here that any slight errors in analysis cancel each other, so that there can be no question as to the accuracy of these results* During the past 6 months, w have been doing analyses on blood by two methods operating in parallel, the one our Spectrographic Method as described by Cholak,and the other a modification of the Dithizone Method as originally described by PisCher and Leopold!. We have seen lead in the blood in various types of plumbIsm In concentrations extending from slightly in excess of a milligram per 100 grams of blood down to on tenth of a milligram per 100 grams of blood* Xngeneral, two factors appear to determine the height of the lead concentration} one, the severity of exposure} and two, the time interval between the .cessation of exposure and the taking of the blood sample. Generally, th severity of the symptoms correlate with the height of the lead coneen t ra"Ion, hut this Is sot always true# I think it is quite safe to say that the presence of one tenth, of' a milligram of lead per 100 grams of blood Is indicative of a recent significant exposure to lead# and although symptoms may not be present at this concentration# the existence of symptoms resembling those of plumbism may be adequately explained* X should be inclined,# at present# to regard, values under one . tenth of a milligram of blood as significant only if repeated observations confirm this as the basic level of lead concentration rather than a chance high..value.,.. The lead values in the spinal fluid are much lower* Prom our present data# which are Incomplete# X am disposed to regard values in excess of .01 milligrams per 100 oc of spinal fluid as doubtfully significantj values In excess of *02 milligrams per 100 cc of spinal fluid as almost certainly significant! and values above *03 as definitely indicative of recent significant lead exposure* I believe when we have sifted the thing as carefully in the case of spinal fluid as we have In the case of blood# we shall probably find the normal values to range between *001 and *01 milligrams per 100 cc. In acute lead cases, we have found values as high as .1 milligrams per 100 cc* I believe# without referring at this time to my records# that this occurred in only one case in which the diagnosis was at no time a matter of conjecture This will require confirmation through observations on similar oases# since you will realize# I am sure# that there are numerous opportunities for slight contamination# particularly at the bedside* As a matter of fact# we make it a point at present not to make analyses of spinal fluid# or of blood either# unless the samples ar collected by means of our own needles# into our own containers# and by a technique which we describe in detail* The us of the qrdinary hospital spihal, fluid needle1 is almost* certain to result in confcsisiination since the construction of the needle is such that the fluid may come in contact with lead^bearing material* X trust this will give you the information you require# and I shall be pleased to give you eny additional information a s a refinement of this when I have completed the study of our data* ' Cordially yours# ' RAKiIs ' Robert A. kehoe# M.D* ^ 0020096