Current status of some aspects of parenteral nutrition

Abstract

I T was at the Boston City HospitaI that I first became interested in the nutritiona probIems of seriousIy iI and injured patients. 1 went there in November, 1942 as a Research Associate on the Burn Service. Five days after I came, we admitted 130 patients with burns as a resuIt of the Coconut Grove fire. Most of these patients were heahhy men and women at the time of the fire; we were startIed by the rapidity with which those severeIy burned persons became maInourished. Some Iost as much as forty pounds in three weeks. During the past thrity years, beginning with the studies of Cuthbertson in EngIand, innumerabIe studies of the metaboIic disturbances which foIIow severe injury have been presented. In Boston, Massachusetts, Dr. Moore at the Peter Bent Brigham HospitaI, Dr. Cope at the Genera1 HospitaI and Drs. Lund, Davidson and the Iate F. H. L. TayIor at the City HospitaI have contributed significantIy to our understanding of these probIems. I wiI1 not attempt a comprehensive report on this subject. We know, though, that prolonged inadequate food intake in the face of increased nutrient needs, reflecting the severity of the injury and its complications, is often the important factor underIying postinjury maInutrition. AI1 are agreed that whenever possibIe, eating is the best way the patient has to meet his nutritiona1 needs. But, at times, parentera dietary suppIementation is needed and, occasionaIIy, feeding by the intravenous route is the onIy effective way of supplying food to the patient. I wiI1 not discuss the reasons for this; I’m certain that they are we11 known to aII. When intravenous feeding is undertaken, the same genera1 principIes which underIie effective ora feeding must be foIIowed. In fact, these principIes, such as the proper time reIationship in which nutrients are suppIied, are most often brought into sharpest focus during intravenous feeding. Paramount among these is the necessity of suppIying enough nonprotein caIories to meet the patient’s caIoric demands so that the amino acids, peptides and proteins, which are infused, can be used for tissue protein synthesis. When the caIoric requirements are high, it is not generaIIy possible to meet them with carbohydrates. The intravenous infusions of gIucose, fructose and invert sugar are Iimited by their osmotic pressure effects. Five per cent gIucose is isotonic but I L. suppIies onIy about 200 ca1. A L. of 25 per cent gIucose could suppIy about 1,000 ca1. but such a soIution is very hypertonic, is irritating to the veins and must be given sIowIy to prevent excessive urinary 10s~. AIcohoI offers 6 ca1. per ml. if it is infused, but its depressing and intoxicating effects and possibIe Iiver toxicity are drawbacks to its use in adequate amounts. Fat provides about 9 ca1. per gm. and has the potentia1 of being the intravenous nutrient which can meet the patient’s caIoric needs even when these are considerabIy higher than normaI. Fat, in an emuIsion, has the happy property of not being hypertonic even in high concentrations and it is not excreted by the kidney. An emuIsion containing 15 per cent fat and 5 per cent gIucose suppIies about 1,500 cal. per L. which is far different from the 400 cal. per L. suppIied by IO per cent gIucose soIution. The idea of injecting fat intravenousIy is physioIogicaIIy sound. AI1 of us get intravenous infusions of fat every day. Fat, after digestion and absorption enters the intestina1 Iymphatics and then the thoracic duct as an emuIsion of chyIomicra. The contents of the thoracic duct empty into the subcIavian vein. The probIem is