Effect of Intravenously Injected Iodinated Lipid Emulsions on the Liver

Iodinated lipid emulsions have been shown to have great potential as site specific contrast media for the liver and spleen. Because of unacceptable adverse reactions none of these emulsions has been adopted for clinical use. In an attempt to find an explanation for these adverse reactions we tested three iodinated lipid emulsions, EOE-13, AG 60.99 and AG 66.18. The following models were used: Computed tomography (CT) of the rabbit liver, in vivo microscopy and electron microscopy of the rat liver. The emulsions contained particles of different sizes and were used in varying doses. We found that the larger the emulsion particles, the more likely they were to be taken up by the Kupffer cells and thereby the higher the opacification of the liver achieved at CT. We also observed changes in the microcirculation of the liver when the emulsions were given in doses required to secure satisfactory opacification of the liver at CT. The main changes were 1) a marked increase in the size of the Kupffer cells, and 2) damage to the sinusoidal endothelium, both contributing to sinusoidal congestion. These changes strongly suggest activation of the macrophages and this in turn probably results in the release of toxic mediators. We suspect that the adverse reactions observed in patients when using iodinated lipid emulsions are due to these toxic mediators.

Clinical Trials with a New Iodinated Lipid Emulsion for Computed Tomography of the Liver

A new iodinated lipid emulsion, Intraiodol, for which animal studies have indicated better tolerance than for other iodinated lipid emulsions, was tested in 15 patients with malignant lesions, and in one patient with focal nodular hyperplasia. Repeated CT scans of the liver and spleen and blood tests were performed for 24 hours after intravenous injection of Intraiodol. The uptake of Intraiodol in the liver (peak mean 28.6 HU) was higher than in the spleen (peak mean 21.8 HU). The uptake of Intraiodol in malignant lesions was minimal (peak mean 2.8 HU). The detection rate of hepatic lesions was equal to or better than that achieved by US, CT, and/or CT angiography. However, liver uptake of Intraiodol was low in 2 patients with severe fatty infiltration. Intraiodol produced vascular enhancement up to one hour after injection since it was eliminated slowly from the circulation. The observed adverse reactions consisted of temporary metallic taste in 5 of the patients, fever and exacerbation of back pain in one patient, and transient thrombocytopenia in one patient. Alkaline phosphatase increased (17%, p<0.01) only at two hours, and erythrocyte count (6%, p<0.05) at 24 hours after injection. Our initial results indicate diagnostic advantages of Intraiodol without serious adverse reactions. Further clinical studies are required to confirm these findings.

Experimental Investigation of a New Iodinated Lipid Emulsion for Computed Tomography of the Liver

Iodinated lipid emulsions are highly efficient macrophage imaging agents. Nevertheless, none of them has been accepted for clinical use because of adverse reactions. We have tested a new iodinated lipid emulsion, Intraiodol. The size and surface properties of the particles of this emulsion are similar to those of Intralipid which in turn closely resemble the naturally occurring chylomicrons. Using computed tomography (CT) of the rabbit liver as well as vital microscopy and electron microscopy of the rat liver we found that Intraiodol has low efficiency as a liver-specific contrast medium because its particles are predominantly taken up by the hepatocytes and to a less extent by the Kupffer cells, as is Intralipid. The low efficiency of Intraiodol could be fully compensated by an increase in dosage without any significant effect on sinusoidal blood flow. This in turn suggests that the likelihood of release of toxic mediators (and thereby related adverse reactions from activated macrophages) is reduced. We believe that this new way of delivering iodinated lipid particles to the liver represents an important advance in the search for a non-toxic lipid emulsion for CT of the liver.

[Total parenteral nutrition. History. Present time. Future]

Total parenteral nutrition (TPN) has been available for only 30 years. However, history in this field goes back more than 350 years with the first landmark being the description of general blood circulation by William Harvey in 1628. His discovery is the anatomical basis for intravenous infusions. Many investigations were performed during the following centuries showing that solutions containing electrolytes and glucose could be given intravenously in man. The accumulated knowledge of protein metabolism formed the basis for studies on intravenous nutrition with protein hydrolysates, peptides and amino acids. The observation in the late 30-s by Robert Elman that amino acids in the form of protein hydrolysate could be safely administered intravenously in man was the first major step toward TPN. During the following years, major efforts were made to find methods to prepare infusion solutions with a high energy content and low osmotic pressure. The most realistic alternative seemed to be fat in the form of an emulsion. Many studies of a large number of various fat emulsions were made however, all of these emulsions caused severe adverse reactions in man. The first safe fat emulsion, intralipid, was made available in the early 60s. This was the second major step toward TPN. It was then no problem to include vitamins, electrolytes and trace elements in the fat emulsions and the solutions of amino acids and glucose. A few years later it was shown that a central venous catheter could be used to administer the infusion fluid intravenously. Many clinical investigations and reports have shown that the newly developed intravenous nutritional regimens are adequate alternatives to the ordinary diet. In this way it has been possible to maintain or obtain a good nutritional condition in most situations when oral or tube feeding can not be used. TPN has been shown to be of very great clinical importance to prevent and treat starvation often related to high morbidity and mortality.

Lipid mediated modification of rat heart allograft survival

The effect on allograft survival of intravenous fat emulsions that differed in the ratio of functionally important n-3 and n-6 fatty acids was studied in a heterotopic cardiac transplant model in rats. Twenty percent fat emulsions were administered by continuous infusion at a dosage of 9 g fat/kg body weight per day, starting immediately after transplantation and continuing until complete rejection. The n-6 and n-3 fatty acids represent 75%, 43%, 60%, and 59% of all fatty acids in safflower oil, fish oil, soybean oil, and a 1:1 mixture of safflower and fish oil, respectively. The n-6 fatty acids predominate in safflower oil (370/1) and soybean oil (6.5/1), while the n-3 fatty acids dominate in the fish oil (7.6/1). The 1:1 mixture of safflower and fish oil has the balanced composition (n-6/n-3 = 2.1/1) recommended by Kinsella and served as oil-treated controls. Continuous infusion of safflower oil, fish oil, and soybean oil prolonged graft survival time to 13.3, 12.3, and 10.4 days, respectively, compared to 6.8 days in the oil-treated controls (P < 0.01 for all comparisons). Another control group infused with saline rejected the allografts after 7.8 days (P = NS compared to oil-treated controls; P < 0.01 for all other comparisons). The data suggest that intravenous administration of polyunsaturated fat emulsions results in an immunosuppressive effect that seems to be dependent on the n-3/n-6 fatty acid ratio of the fat emulsion.(ABSTRACT TRUNCATED AT 250 WORDS)

Recollections of pioneers in nutrition: landmarks in the development of parenteral nutrition

Total parenteral nutrition (TPN) has been available for only 30 years. The successful development of this therapy, in a modern sense, was initiated in the late 30s. However, history in this field goes back more than 350 years, with the first landmark being the description of general blood circulation by William Harvey in 1628. His discovery is the anatomical basis for intravenous infusions. Many investigations were performed during the following centuries showing that solutions containing electrolytes and glucose could be given intravenously in man. The accumulated knowledge of protein metabolism formed the basis for studies on intravenous nutrition with protein hydrolysates, peptides and amino acids. The observation in the late 30s by Robert Elman that amino acids in the form of protein hydrolysate could be administered safely in man was the first major step toward TPN. During the following years, major efforts were made to find methods to prepare infusion solutions with a high energy content and low osmotic pressure. The most realistic alternative seemed to be fat in the form of an emulsion. Many studies of a large number of various fat emulsions were made from the 20s until the end of the 50s. However, all of these emulsions caused severe adverse reactions in man. The first safe fat emulsion, Intralipid, was made available in the early 60s. This was the second major step toward TPN. It was then no problem to include vitamins, electrolytes and trace elements in the fat emulsions and the solutions of amino acids and glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

[Future perspectives in parenteral nutrition]

Some of the future perspectives of parenteral nutrition will most likely be related to the possibilities of improving the infusion solutions used. There are studies indicating that intravenous amino acid mixtures may produce better biochemical and clinical effects either by increasing the content of histidin, arginine, tyrosine, cysteine/cystine and branched chain amino acids or by adding glutamine, ornithin, ornithin-ketoglutaric acid, taurine and glutathion. Several possibilities of improving the intravenous fat emulsions have been studied and discussed. The use of medium chain fatty acid glycerides (MCT) instead of long chain fatty acid glycerides (LCT) may be of some value. Physical mixtures of LCT and MCT have been studied. Glycerides of both medium chain and long chain fatty acids of the same glycerol molecule ('structured lipids') have also been investigated. The omega-3-fatty acids (alfalinolenic, eicosapentaenoic and docosahexaenoic acid) have unique biochemical properties which may be beneficial in various clinical situations when parenteral nutrition is indicated. Intravenous fat emulsions containing triglycerides of these fatty acids are now being extensively investigated. The omega-3-fatty acids will change the pattern of eicosanoids formed, reduce the tendency to platelet aggregation, increase the resistance to endotoxins, and reduce the viscosity of the blood. Triglycerides of gamma linolenic acid have been considered to be of value in situations when there may be a reduced activity of delta-6-desaturase to transform linoleic acid to arachidonic acid. Many other known (carnitine, non-protein sources, vitamins and trace elements) or unknown nutrients may be found to be useful in order to improve the infusion solutions used in parenteral nutrition.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical trials with a new iodinated lipid emulsion for computed tomography of the liver

A new iodinated lipid emulsion, Intraiodol, for which animal studies have indicated better tolerance than for other iodinated lipid emulsions, was tested in 15 patients with malignant lesions, and in one patient with focal nodular hyperplasia. Repeated CT scans of the liver and spleen and blood tests were performed for 24 hours after intravenous injection of Intraiodol. The uptake of Intraiodol in the liver (peak mean 28.6 HU) was higher than in the spleen (peak mean 21.8 HU). The uptake of Intraiodol in malignant lesions was minimal (peak mean 2.8 HU). The detection rate of hepatic lesions was equal to or better than that achieved by US, CT, and/or CT angiography. However, liver uptake of Intraiodol was low in 2 patients with severe fatty infiltration. Intraiodol produced vascular enhancement up to one hour after injection since it was eliminated slowly from the circulation. The observed adverse reactions consisted of temporary metallic taste in 5 of the patients, fever and exacerbation of back pain in one patient, and transient thrombocytopenia in one patient. Alkaline phosphatase increased (17%, p less than 0.01) only at two hours, and erythrocyte count (6%, p less than 0.05) at 24 hours after injection. Our initial results indicate diagnostic advantages of Intraiodol without serious adverse reactions. Further clinical studies are required to confirm these findings.

Experimental investigation of a new iodinated lipid emulsion for computed tomography of the liver

Iodinated lipid emulsions are highly efficient macrophage imaging agents. Nevertheless, none of them has been accepted for clinical use because of adverse reactions. We have tested a new iodinated lipid emulsion, Intraiodol. The size and surface properties of the particles of this emulsion are similar to those of Intralipid which in turn closely resemble the naturally occurring chylomicrons. Using computed tomography (CT) of the rabbit liver as well as vital microscopy and electron microscopy of the rat liver we found that Intraiodol has low efficiency as a liver-specific contrast medium because its particles are predominantly taken up by the hepatocytes and to a less extent by the Kupffer cells, as is Intralipid. The low efficiency of Intraiodol could be fully compensated by an increase in dosage without any significant effect on sinusoidal blood flow. This in turn suggests that the likelihood of release of toxic mediators (and thereby related adverse reactions from activated macrophages) is reduced. We believe that this new way of delivering iodinated lipid particles to the liver represents an important advance in the search for a non-toxic lipid emulsion for CT of the liver.

Effect of intravenously injected iodinated lipid emulsion on the liver. An experimental study correlating computed tomography findings with in vivo microscopy and electron microscopy findings

Iodinated lipid emulsions have been shown to have great potential as site specific contrast media for the liver and spleen. Because of unacceptable adverse reactions none of these emulsions has been adopted for clinical use. In an attempt to find an explanation for these adverse reactions we tested three iodinated lipid emulsions, EOE-13, AG 60.99 and AG 66.18. The following models were used: Computed tomography (CT) of the rabbit liver, in vivo microscopy and electron microscopy of the rat liver. The emulsions contained particles of different sizes and were used in varying doses. We found that the larger the emulsion particles, the more likely they were to be taken up by the Kupffer cells and thereby the higher the opacification of the liver achieved at CT. We also observed changes in the microcirculation of the liver when the emulsions were given in doses required to secure satisfactory opacification of the liver at CT. The main changes were 1) a marked increase in the size of the Kupffer cells, and 2) damage to the sinusoidal endothelium, both contributing to sinusoidal congestion. These changes strongly suggest activation of the macrophages and this in turn probably results in the release of toxic mediators. We suspect that the adverse reactions observed in patients when using iodinated lipid emulsions are due to these toxic mediators.

New developments in lipid emulsions for parenteral nutrition

More than one thousand publications have demonstrated the safety and efficacy of today's lipid emulsions including long chain fatty acids under experimental and clinical conditions. This has resulted in a general acceptance of a dual energy system comprising both carbohydrates and lipids as non-protein calories in total parenteral nutrition. Non-carnitine-dependent fatty acid has been suggested as a superior energy source in clinical situations where carnitine may be in the subnormal range. A medium chain triglyceride (MCT) emulsion would provide an energy source with a more readily oxidizable substrate. The tolerance of MCT is less than that of long chain triglyceride (LCT), whereby only physical mixtures of these emulsions will be used in humans. A structured lipid (SL) is a triglyceride which includes both medium and long chained fatty acids within the same triglyceride. Emulsions including SL have demonstrated a decreased protein energy expenditure and increased serum albumin in burned animal. The SL has also been superior to LCT emulsions in stimulating muscle protein synthesis and maintaining body weight in hepatectomized animals. These positive effects on protein kinetics have been concomitant with a lower RES involvement during septicemia in burned guinea pigs. Emulsions including fatty acids with odd-number carbons give a possibility to provide a fat emulsion which also could contribute positively to the glucose homeostasis. The omega-3 family of fatty acids has demonstrated a potential pharmacologic effect with regard to their ability to decrease blood viscosity and improve survival rate in endotoxin shock in an experimental model. These observations have been ascribed to changes in thromboxin A2 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The metabolic response to glycerol during parenteral nutrition

The use of various nonprotein energy sources in parenteral nutrition regimens has been discussed for many years. Besides glucose, glycerol, xylitol, fructose and sorbitol are currently being used as water-soluble parenteral fuels. Despite the increasing frequency with which these glucose substitutes are being used, little information is available regarding the differences they evoke in host responses. All experimental evidence to date has shown glycerol to be equally effective in sparing body nitrogen as glucose when supplied in hypocaloric amounts. Results from studies in injured animals suggest that exogenously administered glycerol is a more potent inhibitor of fatty acid oxidation than glucose. Although results from human volunteers have been variable, glycerol administration after injury appears to markedly reduce fatty acid oxidation and ketogenesis, as well as increase hepatic glycogen. Glycerol toxicity appears to result only from its excessive administration, or when administered intraperitoneally or subcutaneously. Intravenous administration of hypocaloric quantities of glycerol alone or as a component of total parenteral nutrition is safe and effective.

Nutrient requirements in various clinical conditions

We now have a fairly good knowledge of the number of essential nutrients required in man. However, the studies are limited on the exact basic, minimal and optimal requirements of these nutrients in various conditions. Many more investigations are necessary in this field of clinical nutrition. We also need more information on the various biological and clinical parameters to be used in such studies. However, the present recommendations of the nutrient intakes in various clinical situations seem to be sufficient to maintain or obtain a good nutritional status in many clinical conditions and to prevent nutrient deficiency symptoms. Most of these recommendations are generous in relation to the basic requirements. The achievements in this field make us currently able to nourish our patients properly either by well-balanced ordinary hospital food or by tube feeding or parenteral nutrition.

Standards for nutritional adequacy of the diet: European and WHO/FAO viewpoints

The dietary recommendations of FAO/WHO and of the various European nations differ in several ways. There are two types of dietary recommendations or standards. The first is related to the recommended daily intake of nutrient and the second refers to the nutrient content of the diet expressed either as percentage of total energy (energy % or cal %) derived from protein, fat, and carbohydrate or as the amounts of nutrients in relation to units of energy, the so-called nutrient concentration or nutrient density (weight per 1000 kcal, per 1 MJ or per 10 MJ). The numbers of recommended nutrients vary between eight and 28. The recommendations are given for individuals of different age, sex, and physiological status. The highest number of subgrouping is 41 and the lowest 11. The ranges of recommended values are sometimes very wide, but all seem acceptable from the nutritional point of view. There are many good reasons for this situation such as cultural background, food tradition, food production, and availability.

Development of fat emulsions

The studies on the possibility of preparing IV fat emulsions began in the 1920's; since then, a very large number of emulsions with various fats and emulsifiers have been investigated. However, none of the early fat emulsions could be used safely in man. By the trial and error technique, a method was finally found to prepare soybean oil and egg yolk phospholipids to make a fat emulsion that had a low incidence of adverse reactions. A newly devised biological test system based on nutritional concepts was of crucial importance. It meant that any energy supplying nutrient should be tested in animals in relation to the energy requirement of the species used and not identical to the human dose/kg body weight as in the "classical" toxicity and tolerance tests. With the development of well-tolerated IV fat emulsions it has been possible to devise a TPN regimen that is adequate from a nutritional point of view as well as an adequate alternative to the ordinary oral food. This regimen, which can be administered by the peripheral route, means that the original aims for developing IV fat emulsions were finally achieved.

Parenteral nutrition

Parenteral nutrition therapy was born 35 to 40 years ago when the first steps were taken to perform a protein nutrition by the intravenous supply of amino acids in man. Since that time, many efforts have been made to supply adequate amounts of energy intravenously. These efforts have resulted in the two available systems for parenteral nutrition: the lipid-carbohydrate system and the glucose system. The lipid-carbohydrate system, which corresponds to the nutrient content of normal food, may be given either in a peripheral vein or through a central vein catheter. The glucose system is administered through a central venous catheter. Many problems concerning the parenteral nutrition need to be solved and further elucidated. However, our present knowledge and technique in this field are far advanced over earlier methods. Now all patients who cannot take food in adequate amounts orally or enterally may be kept in good nutritional status by parenteral nutrition. In this way it is possible to prevent starvation and its complications in these patients.

[General aspects of intravenous feeding of cancer patients]

In order to obtain or maintain a good nutritional status in cancer patients, it is often necessary to perform intravenous nutrition. In summary, several studies have indicated that intravenous nutrition may be beneficial in association with surgery, radiation, or chemotherapy in patients with cancer. More controlled studies, however, are required. There is no indication at the present time of any adverse effects of this method of treatment in relation to tumor growth. The general nutritional improvement in patients on intravenous nutrition increases the immunocompetence, resistance to radiation and cytostatics as well as the mood and quality of life of the cancer patients. In very broad terms this new intravenous nutrition therapy means that a cancer patient should not be left without specific cancer therapy because of starvation and its serious or even fatal complications.

[General aspects concerning the intravenous feeding of cancer patients]

In order to obtain or maintain a good nutritional status in cancer patients, it is often necessary to perform intravenous nutrition. In summary, several studies have indicated that intravenous nutrition may be beneficial in association with surgery, radiation, or chemotherapy in patients with cancer. More controlled studies, however, are required. There is no indication at the present time of any adverse effects of this method of treatment in relation to tumor growth. The general nutritional improvement in patients on intravenous nutrition increases the immunocompetence, resistance to radiation and cytostatic as well as the mood and quality of life of the cancer patients. In very broad terms this new intravenous nutrition therapy means that a cancer patient should not be left without specific cancer therapy because of starvation and its serious or even fatal complications.

[Complete parenteral nutrition of amino acids, glucose, vitamins and minerals with inclusion of fats]

The objective of complete intravenous nutrition is to supply by the intravenous route all the nutrients normally obtained in the oral diet and the same relative proportions as absorbed from an oral diet. Some suggested allowances to meet these nutritional requirements in patients with different clinical conditions are made. There appears to be little overall difference in the clinical effectiveness of an intravenous regime in which all the non-protein energy is provided by glucose and one in which both glucose and lipid are used. However, the use of a system of complete intravenous nutrition, which by definition must contain lipid, does have specific practical advantages which make it the system of choice in certain circumstances.

A perfluorochemical oxygen carrier (fluosol-43) in a synthetic medium used for perfusion of isolated rat liver

An emulsion of perfluorotributylamine (Fluosol-43) was used as substitute for the gas-carrying function of erythrocytes in a synthetic medium for perfusion of isolated rat liver. The efficiency and effect of this synthetic gas-carrier were evaluated from measurements of the concentrations of rat albumin, the unsaturated vitamin B12-binding capacity of small-molecular-size vitamin B12-binding proteins (UBBC of SBP), urea nitrogen, glucose, sodium, potassium, alanine amino transferase (ALAT) in the medium, and the incorporation of 14C-lysine into the circulating proteins. Secretion of bile, portal pressure, PO2, PCO2 and pH in the affluent and the effluent mediums were also measured. The results demonstrate that the oxygen-carrying capacity of the medium and the metabolic functions of the liver were higher, and the liver damage less, when the medium included Fluosol-43 than without it. The albumin synthesis and the secretion of bile were as high as has been reported for perfusions with erythrocytes. This indicates that the oxygen carried by the Fluosol-43 was utilised by the liver, and that the metabolic functions were not adversely affected during 4 h of perfusion by the medium containing Fluosol-43.

Studies on isolated rat liver perfused by perfluoro-compound emulsion

Isolated rat livers were perfused for 6 hours by different types of cell-free synthetic media. Some of the media included perfluoro-compounds as an oxygen carrier. The value of the perfusion medium as blood substitute was judged on the basis of observations and measurements of a number of parameters. These were: secretion of bile, fluid pressure in the portal vein, the level of GPT (ALAT) transaminase, urea nitrogen, and glucose in the perfusate. The rate of albumin synthesis and the rate of 14-C-lysine incorporated into circulating proteins were also measured. It was found that perfusion of the isolated rat liver with the TC-199 Difco medium containing the perfluoro-compound FC-80 emulsion maintained the liver in a good condition demonstrated, among other things, by the synthesis of albumin and other proteins. The liver could be kept in a good functional condition during 6 hours perfusion with this cell-free medium. With all the other types of perfusate tested the liver did not synthesize proteins. The isolated rat liver seems to be both convenient and advantageous for testing the perfusion media with respect to their capacity to maintain important metabolic functions.

Vollständige parenterale Ernährung

Ausgedehnte experimentelle und klinische Untersuchungen haben ergeben, dass man eine vollständige intravenöse Ernährung mit Hilfe von Aminosäuregemischen, Glukose oder Fruktose, Fett-emulsionen, Elektrolyten und Vitaminen durchführen kann. Mit dieser Alternative zur oralen Nahrungsaufnahme ist es möglich, bei Patienten, bei denen eine orale Nahrungszufuhr unmöglich oder nicht angezeigt ist, einen guten Ernährungszustand zu erreichen und das Wachstum bei Kindern über längere Zeit zu gewährleisten. Durch die parenterale Ernährung ist es bei Kleinkindern und Säug-lingen einerseits möglich, postoperative Körpereiweiss- und Ge-wichtsverluste zu verhindern und andererseits die Neubildung von Körpereiweiss anzuregen und das Wachstum zu fördern. Manche Fragen, die mit der parenteralen Ernährung in Zusammen-hang stehen, müssen im Laufe ihrer weiteren Anwendung noch be-antwortet werden, wie z. B. Fragen der optimalen und maximalen Fettzufuhr, der optimalen Zusammensetzung von Aminosäuregemischen und des Energie-Nährstoffbedarfes. Unser heutiges Wissen über eine vollständige parenterale Ernährung ist jedoch so weit-reichend, um eine Mangelernährung, wie sie als Begleitsymptom bei den verschiedensten inneren und chirurgischen Erkrankungen auf-zutreten pflegt, ausschalten zu können.