Food by Vein

　　Hospitals are beginning to use the new method of supplying food to those who cannot eat … the expectations are auspicious

By Barclay Moon Newman

　　An important new way to prolong life has just been discovered. Food is now being given by vein to patients who cannot eat—because of excessive weakness at the time of operation or because the surgeon must cut some portion of the alimentary tract, as in removing a tumor. The new method is already being used in hospitals and enables patients to survive digestive crises hitherto often fatal.

　　Of course, calories for heat energy have long been given by vein in the form of a solution of the simple sugar dextrose, and the body is thus supplied with a priceless source of immediate energy with which to run the human mechanism. The indispensable carbohydrate component of the diet is taken care of in this way.

　　Salt solutions also have long been provided by vein, and the mineral component of the diet is accounted for. Existence for weeks is possible without vitamins, although they have in many cases been found to mean the difference between death and continued life. Now a number of pure vitamins—including vitamin A, thiamin, ascorbic acid, riboflavin, nicotinic acid, B6, D, E, and K—are commercially available and are injected as a common practice. Some are safely given by vein, others by administration under the skin so that they are only very slowly absorbed into the blood. Ultra-violet rays synthesize small quantities of vitamin D in the skin upon which such light is made to fall. So the vitamin problem has not been a major obstacle to successful surgery and convalescence.

　　The fat component of the diet can be dispensed with, for many days at least, if not weeks. But even fat has been provided by injection. In 1935, Dr. Emmett Holt, Jr., and his associates at Johns Hopkins Hospital made exceedingly fine emulsions of fat—olive oil—and injected the preparation into dying patients. Improvement followed. Inasmuch as fat is not only an essential nutrient and must eventually be taken if the patient is to remain alive but also a more efficient source of energy, weight for weight, than carbohydrate, future developments in fat administration will be important and should bring new successes that will permit the patient to recover more rapidly.

　　Water, sugar, mineral salt, vitamin, and fat are five of the six nutrients known to be indispensable in human nutrition. The sixth is protein, until recently the main obstacle in the way of perfecting the administration of food by vein, through an extended period.

　　Now, for the first time in medical history, there is a satisfactory substitute for protein-by-mouth. Bases for the complete solution of the problem of intravenous feeding—of food by vein—have been established. The digestive tract can be completely dispensed with for weeks. Meanwhile, it can in many cases be restored to approximately normal activity. Thus the patient balks death.

　　Credit goes to Doctors Robert Elman and D. O. Weiner, of the Department of Surgery, Washington University School of Medicine, and of the St. Louis City , the St. Louis Children's, and the Barnes hospitals, St. Louis .

　　These doctors knew that it would be dangerous to try to inject into the veins even the most carefully purified protein, such as casein from milk. The blood and tissues of the body cannot cope with foods so intricate, for protein is the most complex chemical structure in the world. A first injection of casein would sensitize the body so that a second injection would result in a terrific shock, very likely to be fatal. This sensitization to protein is an unavoidable, normal body reaction; a condition like that of allergy is set up. It is the work, instead, of the digestive tract to break down proteins so that only fragments of the former huge molecules are made available for absorption.

　　The ferments of the digestive juices are the catalysts that bring about this cracking of the protein molecule into its main constituents or component units, known as amino acids. Following such decomposition, absorption of these simple chemical structures, the amino acids, occurs. These building blocks of the proteins thus arrive in the blood stream, which transports them to tissues that in turn absorb them. Once in the tissues throughout the body, the amino acids are, in utterly unknown chemical reactions, put together so that new protein, the chief basis of living tissue, is synthesized. Without a steady supply of amino acids, tissues degenerate and die, and the body dies. With a steady supply of amino acids, usually derived from food protein, tissue is constantly regenerated to replace that which is lost in those activities which we call life.

　　Tissues starving for protein become pathologically swollen with excess water; but when protein-building units are supplied, the swelling subsides. Other less obvious changes take place, and the patient grows stronger with the trend back to normal.

　　To a limited extent, serum from a blood donor may be used to supply amino acids. But even a quart of serum a day will not yield enough building blocks to construct the large numbers of protein molecules required throughout the tissues.

　　Doctors Elman and Weiner had learned that, in 1913, two other scientists, Henrique and Andersen, had kept a goat alive and gaining weight by food via vein. The source of protein building blocks, the amino acids, was meat whose protein had been digested in the test tube. Also, Van Slyke and Myer had sent digested protein coursing through the blood vessels of dogs, and no harm had been done.

　　With these favorable discoveries in mind, Doctors Elman and Weiner digested casein with acid, and so prepared a mixture of most of the indispensable building blocks of protein. The acid, however, decomposed one of the amino acid units known as tryptophane, and casein, to begin with, is low in another, called cystine, an invaluable source of sulfur for protein; therefore the mixture was fortified with a small percentage of tryptophane and a little cystine—amino acids which can be bought on the market.

　　The preparation was tried first on rats. They grew and thrived. Further experimenting showed that the preparation was free from dangerous, undigested protein. In this test, guinea pigs were used. Repeated injection did not bring about a sensitized condition, and no shock resulted.

　　Next came the dog, into which the amber solution of amino acids plus some sugar was injected. Careful measurements of the level of amino acids in the dog's blood were then made, and it was found that the injected nutrients rapidly and safely disappeared from the blood, certainly to go into the tissues, there to be caught up in the swirl of life's chemical laboratories and made into canine protein. Little of it seemed to be wasted by way of the kidneys. The method appeared to be efficient.

　　In one set of experiments, the dogs were allowed to fast, and a certain quantity of blood was drawn, to reduce the quantity of protein in the blood serum. Then amino acids were given by vein. Re-synthesis of lost protein occurred within six hours after the injection of these protein-building blocks.

　　In another series of experiments, dogs were fed a diet free of protein, for several weeks. Serum protein was observed to sink to lower and lower levels, and characteristic accumulation of water due to protein deficiency began to swell the tissues. But when amber-colored amino acid-dextrose solution was administered by vein, the amount of protein in the dogs' blood serum rose toward the normal level. The most careful examination, moreover, showed no damage to liver or kidney or other organ. Now for human beings.

　　"Our first concern," the two pioneers report, "in giving digested casein to patients was, of course, the possibility of untoward reactions, even though none had occurred in dogs. At first, small doses were injected; they produced no demonstrable effect, so that eventually we administered what was thought to be a full daily quota of amino acids, that is, from one half to two grams per kilogram of body weight."

　　A sense of warmth was noticed by one patient; a slight chill was felt by another, but the temperature remained normal. A child had a slight, transient rash after one of the injections.

　　In practically every instance, benefit came from amino acids by vein, and water-logging of tissues was diminished. No injurious after-effect whatsoever could be seen. All the tests gave proof of the body's use of amino acids to build up new molecules in tissues that had been starving for protein.

　　Still, the substitute for food by mouth is only a temporary measure. The present limit of food by vein is a few weeks at most. One vein cannot be used continuously, so vein after vein must be subjected to the inflow of fluid, and generally the first vein has not recovered sufficiently by the time all the veins have been used.

　　We do, however, have a great beginning. Deeper blood vessels may turn out to be available for use, when better techniques have been devised. When more is learned about protein-building amino acids, probably some of the less important ones can be temporarily dispensed with, and the injected quantity kept at a minimum.

　　Practical possibilities are increasing as amino acids become cheaper through improved commercial syntheses. Drug manufacturers already have placed predigested casein preparations on the market, and with such solutions universally available for research, we can expect further notable developments.

　　Perhaps we can look forward to a considerable extension of the periods during which patients can be kept alive though their digestive tracts are not working. Approximately seven percent of all deaths after the age of 45 is caused by disease of the digestive system. This mortality should be reduced as the use of food by vein is increased through the development of refinements both from the nutritional side and from the mechanical side, where better methods of forcing fluids into veins are concerned. The fluid undoubtedly will be made nutritionally more valuable. The vein through which the fluid is forced will surely be more satisfactorily guarded against possible injury. The stomach, the intestines, the liver and the pancreas will be given longer periods of rest and a greater opportunity to return to health.

　　Fifty percent of cancer deaths is traceable to cancer originating in the digestive system. Already, through the contributions of Doctors Elman and Weiner, a practical step has been taken toward helping the cancer specialist in his vast labors; operation is safer, because there is less danger of starvation following surgery of the digestive tract.

　　Undoubtedly, the main dietary components are known to nutritionists and, by one method or another, injection has been made practical, at least to a degree. But none would assert that the optimum proportions of the various food factors have been determined; for one thing, age will have to be considered more carefully. What percentages of what amino acids are best for the year-old, the decade-old, the semi-centenarian, or the aged? Here a vast research for the future looms. And, even if we now know enough about the main essential items of diet to keep a person alive with food by vein over a period of weeks, no scientist would state that other factors, yet undiscovered, do not after a while become indispensable for longer life.

　　Most experts believe that several additional vitamins are to be turned up, perhaps including vitamins M, P, and factors U and W, the evidence at present pointing to the existence of these and others.

　　Not long ago, copper was added to the list of indispensable metallic elements included in the group termed "mineral salts." Some think that cobalt and zinc, perhaps other metals, in ultra-visible quantities will turn out to be necessary.

　　There are excellent indications also that dextrose does not altogether satisfy the body's demand for sugar. There are other sugars, including the most remarkable of all, galactose, which is one half of the molecule of milk sugar, dextrose being the other half. Galactose is abundant in brain and nerve tissue and present in considerable quantities in every tissue of the body. No tissue (except that of the lactating mammary gland) is known to be able to synthesize galactose.

　　None can ever say how far medical science will go. Research brings astonishing powers to delay death. Food by vein is a major advance in the science of prolonging life. The future of this system can certainly be awaited with high hopes.

　　Source: Reprinted with permission. Copyright ? April 1940 by Scientific American, Inc. All rights reserved.