Energy and protein requirements of general surgical patients requiring intravenous nutrition

Metabolic support challenges with obesity during critical illness

Adiposity-based chronic disease, critical illness, and nutrition therapy increase the risk for overfeeding and worsened nutritional and clinical outcomes. Hypocaloric, high-protein nutrition therapy provides critically ill obese patients the opportunity to achieve net protein anabolism with a reduced risk for overfeeding-related complications. The intent of this review is to discuss the impact of obesity on clinical outcomes, describe the consequences of obesity that increase complications associated with nutrition therapy, provide the framework to develop a hypocaloric, high-protein regimen, review the scientific evidence to support this mode of therapy, and discuss its limitations. Practical suggestions for patient monitoring are also provided.

Protein and Calorie Requirements Associated With the Presence of Obesity

Obesity compounds the metabolic response to critical illness and increases the risk for overfeeding complications due to its comorbidities. Hypocaloric, high-protein nutrition therapy affords the hospitalized patient with obesity the opportunity to achieve net protein anabolism with a reduced risk of overfeeding complications. The intent of this review is to provide the theoretical framework for development of a hypocaloric high-protein regimen, scientific evidence to support this mode of therapy, and unique considerations for its use in specialized subpopulations. Macronutrient goals and practical suggestions for patient monitoring are given.

A comparison of postoperative early enteral nutrition with delayed enteral nutrition in patients with esophageal cancer

We examined esophageal cancer patients who received enteral nutrition (EN) to evaluate the validity of early EN compared to delayed EN, and to determine the appropriate time to start EN. A total of 208 esophagectomy patients who received EN postoperatively were divided into three groups (Group 1, 2 and 3) based on whether they received EN within 48 h, 48 h-72 h or more than 72 h, respectively. The postoperative complications, length of hospital stay (LOH), days for first fecal passage, cost of hospitalization, and the difference in serum albumin values between pre-operation and post-operation were all recorded. The statistical analyses were performed using the t-test, the Mann-Whitney U test and the chi square test. Statistical significance was defined as p < 0.05. Group 1 had the lowest thoracic drainage volume, the earliest first fecal passage, and the lowest LOH and hospitalization expenses of the three groups. The incidence of pneumonia was by far the highest in Group 3 (p = 0.019). Finally, all the postoperative outcomes of nutritional conditions were the worst by a significant margin in Group 3. It is therefore safe and valid to start early enteral nutrition within 48 h for postoperative esophageal cancer patients.

Hypocaloric, high-protein nutrition therapy for critically ill patients with obesity

We published the first article that addressed hypocaloric, high-protein enteral nutrition therapy for critically ill patients with obesity more than 10 years ago. This study demonstrated that it was possible to successfully achieve this mode of therapy with a commercially available high-protein enteral formula and concurrent use of protein supplements. This study was also the first to demonstrate improved clinical outcomes with the use of hypocaloric, high-protein nutrition therapy. The results of this study, its unique findings, and shortcomings are discussed. Subsequent studies have added clarity to the effective use of this therapy, including its use in home parenteral nutrition patients, patients with class III obesity, and older patients with obesity.

Optimal caloric intake for critically ill patients: first, do no harm

Despite considerable efforts to define energy requirements for critically ill patients, no single method has been found to be precise and unbiased for all patients. As a result, clinicians have used various methods that may overestimate energy requirements for some patients. Provision of target caloric intake without regard to the complications of overfeeding, such as hyperglycemia, hypercapnia, or gastric feeding intolerance, could result in overall detrimental clinical outcome. Inadequate nutrition support is also associated with adverse clinical outcomes that necessitate optimization of delivery and tolerance of the nutrition regimen. A pivotal paper by Krishnan and colleagues published in 2003 brought these issues to the forefront of clinical practice. Key papers that support or refute the practice of "permissive underfeeding" are reviewed. Further research is necessary to determine the minimum amount of nutrition required to achieve a therapeutic benefit as well as to ascertain at what amount of additional nutrition intake offers no further improvement in clinical outcome.

Clinical guidelines and nutrition therapy: better understanding and greater application to patient care

The volume of clinical guidelines produced by national and international societies has virtually exploded in the literature over the past decade. The most important aspect of guidelines is transparency, that is, the connection between the recommendation or guideline statement and the underlying supportive studies from the literature should be transparent. Clinical guidelines should help organize the literature, identify key areas of patient management, and provide a framework with which the clinician may operate. The reader of a guideline should embrace controversy, trace back and review the underlying literature, and then determine whether practice should be altered as a result of the guideline recommendations. The purpose of this article is to understand the derivation of clinical guidelines, to learn how to resolve controversy or differences between guidelines and clinical practice, and to learn steps to apply the guidelines to an individual institution or clinical practice.

Nutritional and clinicopathological effects of post operative parenteral nutrition following small intestinal resection and anastomosis in the mature horse

REASONS FOR PERFORMING STUDY

There is an absence of data describing the nutritional requirements and nutritional status of horses following surgery for colic; furthermore, the potential effect of parenteral nutrition (PN) on improving nutritional status in such cases is unknown.

HYPOTHESIS

Post operative colic cases suffer from a potentially detrimental negative energy balance and the PN formulation developed in this study would lead to clinicopathologically detectable improvements in the subjects' nutritional status.

METHODS

Several clinicopathological variables, some known to be associated with nutritional status, were compared in 2 groups of horses in the post operative period following colic surgery; Group N (n = 15) were treated with PN and Group C (n = 15) were starved routinely.

RESULTS

Group N had significantly lower serum concentrations of triglycerides, total bilirubin, albumin and urea and significantly higher serum concentrations of glucose and insulin compared with Group C in the post operative period.

CONCLUSIONS

The control group of horses demonstrated significant clinicopathological evidence of starvation and the described PN protocol resulted in a demonstrably improved nutritional status in the treated horses.

POTENTIAL RELEVANCE

Further study is required to investigate clinical benefits and possible harmful side effects of post operative parenteral nutrition before the technique can be advocated for widespread use in practice.

Hypocaloric feeding of obese patients in the intensive care unit

PURPOSE OF REVIEW

Given the increased awareness of the detrimental complications of overfeeding, particularly hyperglycemia, the safety and efficacy of specialized nutritional support for the critically ill obese patient is of major concern. The intent of this review is to provide the scientific foundation, supporting and conflicting literature, for the implementation of hypocaloric, high-protein specialized nutritional support for acutely ill, hospitalized patients with obesity.

RECENT FINDINGS

Similar anabolic equivalencies can be achieved with hypocaloric, high-protein nutritional support compared with a more traditional higher calorie, lower protein regimen. The provision of additional calories worsens hyperglycemia, results in a further accumulation of fat mass, and increases the potential for overfeeding without significant net protein anabolism gain.

SUMMARY

The current literature indicates that hypocaloric, high-protein enteral or parenteral nutrition is promising as the standard of practice for the metabolic support of the critically ill obese patient. The achievement of net protein anabolism and the avoidance of overfeeding complications are the primary goals, with fat weight loss a welcome secondary benefit.

Anabolic and cardiovascular effects of recombinant human growth hormone in surgical patients with sepsis

The clinical and metabolic effects of 7 days of recombinant human growth hormone (rhGH) and total parenteral nutrition (TPN) in surgical patients with sepsis were determined in a randomized controlled trial. In patients with a mean(s.e.m.) pretreatment rate of net protein catabolism (NPC) of 1.5 g per kg per day or less rhGH treatment decreased NPC from 0.93(0.14) to -0.20(0.24) g per kg per day (n = 5; P < 0.0005) and rendered these patients anabolic. TPN alone decreased NPC from 1.12(0.11) to 0.61(0.11) g per kg per day (n = 5; P < 0.001). In patients with an initial NPC of more than 1.5 g per kg per day rhGH treatment decreased NPC from 2.72(0.12) to 1.08(0.24) g per kg per day (n = 5; P < 0.001) while TPN alone decreased it from 2.41(0.32) to 1.28(0.28) g per kg per day (n = 5; P < 0.005). Use of rhGH was not associated with any adverse effects or improvement in clinical course but did decrease the mean systolic and diastolic pressures during the study period. Thus rhGH is a useful anabolic agent and may have a role in the haemodynamic management of the catabolic patient with sepsis.

Study of hypocaloric peripheral parenteral nutrition in postoperative patients (Europan project)

The objective of this study is to ascertain whether or not the supply of a low-calorie amino acids (AA) parenteral solution is useful in postoperative patients, by assessing a series of parameters that indicate nutritional status. 75 postoperative patients who met at least 2 of the 3 criteria: 1) albumin less than 3 g/dl; 2)prealbumin less than 21 mg/dl; 3) body weight less than 95% of ideal weight, were studied. Patients were divided into 4 groups: control group, 15 patients receiving conventional infusion therapy; group I, 20 patients receiving glucose + AA; group II, 20 patients receiving glycerol + AA; and group III, 20 patients receiving sorbitol-xylitol + AA. The most significant findings were a prompt recovery of short half-life proteins (prealbumin and retinol binding protein), a less negative nitrogen balance, a greater decrease in urinary 3-methylhistidine and a marked increase in most AAs when hypocaloric peripheral parenteral nutrition (HPPN) was used. As regards complications, suture dehiscence occurred in a greater percentage of control patients than in the active therapy groups (13.3% versus 5%) and, in contrast, a greater number of cases of infusion phlebitis was observed in the HPPN groups. Clinical data were not statistically significant. We conclude that HPPN is a valid means for providing nutritional support but, at present, there are few randomized, controlled studies that show that its use is clearly beneficial.

Predictors of total parenteral nutrition-induced lipogenesis

OBJECTIVE

To evaluate the incidence and cause of parenteral nutrition-induced lipogenesis.

DESIGN

Retrospective patient review.

SETTING

A 40-bed predominantly surgical ICU.

PATIENTS

One hundred forty patients receiving central venous nutrition and mechanical ventilatory support.

INTERVENTIONS

Indirect calorimetry was used to determine patient's measured energy expenditure (MEE) and respiratory quotient (RQ). Additionally total caloric intake (TCAL), glucose infusion rate, basal energy expenditure (BEE), estimated stress factor, and calculated energy expenditure (CEE) were assessed in each patient.

MEASUREMENTS AND MAIN RESULTS

Net fat synthesis was found as RQs exceeded 1 in 47 percent of patients. Statistically significant differences in oxygen consumption, CO2 production, measured energy expenditure, total and carbohydrate caloric intake, and glucose infusion rate were found between groups of patients with an RQ < or = or > 1. Seventy-three percent of patients with glucose infusion rates > 4 mg/kg-min had RQs > 1.

CONCLUSIONS

Net fat synthesis was found in a surprisingly large number of critically ill patients receiving central venous nutrition. Many of these patients received carbohydrate calories in excess of their measured energy expenditure, even though it appeared that they needed this level of caloric intake by clinical assessment. The high carbohydrate total parenteral nutrition (TPN) solutions with lipids provided only for prevention of essential fatty acid depletion resulted in an unacceptably high incidence of fat synthesis. The results suggest that caloric intake may be optimized in critically ill patients using indirect calorimetry. When calorimetry is not available, a total caloric intake of up to 140 percent of the BEE with glucose infusion rates not exceeding 4 mg/kg-min and fats providing 40 to 60 percent of calories will meet the energy requirements of most critically ill patients without forcing the RQ > 1.

Metabolic basis for management of the septic surgical patient

The physiologic events accompanying postoperative septic complications in surgical patients represent a coordinated response to bacterial invasion, which is aimed at maintaining the function of key organ systems. When sepsis is prolonged or overwhelming, physiologic dysfunction and multiorgan failure develop. This review outlines the pathophysiologic response to sepsis and correlates it with recent therapeutic advances in the metabolic management of the postoperative septic patient.

Total energy expenditure in patients with Crohn's disease: measurement by the combined body scan technique

A combined body scan technique for measuring total energy expenditure (TEE) from energy intake and changes in energy stores is presented. The TEE of 13 patients with Crohn's disease who required nutrition support over a 14-day period was measured. They had a mean TEE of 33 kcal/kg per day. The components of the TEE in these 13 patients were also measured. Seventy percent of the TEE was made up by resting metabolic expenditure, 10% by diet-induced thermogenesis, and the remaining 20% by activity energy expenditure. These patients had a mean activity energy expenditure of 369 kcal/day. The diet-induced thermogenesis was a mean 12.6% increase on the resting metabolic expenditure. Each percent increase was caused by a mean of 210 kcal of energy in either the intravenous nutrition or the enteral nutrition. There was no difference in diet-induced thermogenesis between those having enteral nutrition and those receiving intravenous nutrition. Decreased activity was significantly correlated with increased activity of the disease (r = .7, p < .01). This confirms the belief that patients with Crohn's disease require no more energy (ie, 33 kcal/kg per day) than other patients. If the resting metabolic expenditure is increased through illness, then the activity energy expenditure decreases. The combined in vivo neutron activation-dual energy x-ray absorptiometry technique has allowed for the first time measurements in ward patients with Crohn's disease. The measurements confirm that TEE is not raised and that 30 to 35 kcal/kg per day is sufficient to achieve energy balance in such patients.

Energy balance in elderly patients after surgery for a femoral neck fracture

To study energy and protein balances in elderly patients after surgery, spontaneous energy and protein intake and resting energy expenditure (REE) were measured in 20 elderly female patients with a femoral neck fracture (mean age 81 +/- 4, SD, range 74-87 years; weight 53 +/- 8, range 42-68 kg) during a 5-6 day period following surgery. REE, measured over 20-40 min by indirect calorimetry using a ventilated canopy, averaged 0.98 +/- 0.15 kcal/min on day 3 and decreased to 0.93 +/- 0.15 kcal/min on day 8-9 postsurgery (p less than 0.02). REE was positively correlated with body weight (r = 0.69, p less than 0.005). Mean REE extrapolated to 24 hr (24-REE) was 1283 +/- 194 kcal/day. Mean daily food energy intake measured over the 5-day follow-up period was 1097 +/- 333 kcal/day and was positively correlated with 24-REE (r = 0.50, p less than 0.05). Daily energy balance was -235 +/- 351 kcal/day on day 3 (p less than 0.01 vs zero) and -13 +/- 392 kcal/day on day 8-9 postsurgery (NS vs zero) with a mean over the study period of -185 +/- 289 kcal/day (p less than 0.01 vs zero). When an extra 100 kcal/day was allowed for the energy cost of physical activity, mean daily energy balance over the 5-day study period was calculated to be -285 +/- 289 kcal/day (p less than 0.01 vs zero). Measurements of total 24-hr urinary nitrogen (N) excretion were obtained in a subgroup of 14 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of nutritional recovery after total gastrectomy

Malnutrition is reported to be an inevitable consequence of total gastrectomy, although there are few data to support this contention. Six patients of median age 63 years underwent total gastrectomy for malignancy. At follow-up (median 45 months, range 25-60 months) each patient was clinically tumour-free and underwent dietary assessment, faecal fat and nitrogen measurement and routine haematological testing. Protein and fat stores, measured by neutron activation analysis and the tritiated water dilution technique, were compared with the same measurements made before operation and with predicted values. Mean (s.d.) dietary intake (2224(381) kcal day-1 and 81(15)g protein day-1) met the patients' estimated requirements. Mean(s.d.) serum albumin and faecal nitrogen values were normal but there was notable steatorrhoea (21(17) g day-1). Body composition measurements revealed profound deficiencies of body-weight (P less than 0.02), protein (P less than 0.01) and fat (P less than 0.02) before operation which were not corrected by an apparently curative total gastrectomy (P less than 0.05), although further deterioration was prevented.

What rate of infusion of intravenous nutrition solution is required to stimulate uptake of amino acids by peripheral tissues in depleted patients?

We examined the effect of varying the quantities (0, 0.1, 0.2, 0.3, and 0.4 gN.kg-1.[day]-1) of nitrogen input on N balance, 3-methylhistidine (3MH) excretion, plasma amino acid concentration and the net flux of amino acids across the leg in depleted patients requiring parenteral nutrition. The calorie-to-nitrogen ratio was 140 to 1 (kcal:1 gN) and consequently the patients received varying amounts of calories (8, 14, 28, 42, and 56 kcal.kg-1.[day]-10. There was negative nitrogen balance and net loss of amino acids from the limb during fasting. An infusion of 0.2 gN.kg-1.[day]-1 of IVN reversed the net catabolic process and resulted in equilibrium of peripheral total amino acid flux and of tyrosine flux without a decrease in 3MH excretion. Net uptake of total amino acids and tyrosine in peripheral tissues was achieved with 0.4 gN.kg-1.[day]-1 and 56 kcal.kg-1.[day]-1. This was associated with a fivefold increase in 3MH excretion (p less than 0.01), indicating that net anabolism occurred with increased protein turnover. Fifty per cent of the amino acids taken up by peripheral tissues during infusions of 0.4 gN.kg-1.[day]-1 was due to the uptake of glutamate (Glu) and 20% was due to the uptake of branched chain amino acids (BCAA). Plasma Glu concentration, [Glu], did not increase with increasing IVN infusion, but BCAA concentrations did. Although the mean plasma [Glu] did not change with IVN infusion, there was an independent effect of plasma [Glu] (p less than 0.0001) and of N input (p less than 0.0001) on Glu flux, indicating that even at high infusion rates the maximal capacity of peripheral tissues to take up Glu had not been reached.

[Postoperative energy requirements following large abdominal surgery interventions: comparison of measuring by indirect calorimetry with estimated values]

Energy requirement after major abdominal operations, as calculated according to the formula for basic energy expenditure by Harris-Benedict, was increased by 30% in the early and by 50% in the late postoperative period. Correlation of these calculated values to measurements by indirect calorimetry was good. Even more simply a good estimation of caloric requirements can be obtained by multiplication of the body weight with a factor 30. The development of septic complications does not increase considerably postoperative energy expenditure, however, the correlation between measured and estimated values becomes poor. As supposed from isotope studies measuring gas exchange for indirect calorimetry for one hour provides sufficiently stable results.

Metabolic response to sepsis and trauma

This review examines current knowledge regarding the metabolic responses to trauma and sepsis. The factors which may mediate the responses are discussed and the potential value of pharmacological or nutritional manipulation is reviewed.

The metabolic and nutritional effects of injury and sepsis

The existence of a co-ordinated response to stress of a variety of causes has clearly been established. Basically, this consists of an elevation in energy expenditure and an increased breakdown of skeletal muscle protein. In addition, glucose level in the plasma increases as a result of increased synthesis and decreased uptake of glucose into cells. Release of fatty acid into the plasma is also increased, and an elevation in the proportion of energy derived from oxidation of fatty acids is observed. This response is qualitatively very different from that seen in simple starvation, where a progressive reduction in energy expenditure and a reduction in the synthesis of glucose allows fat to become the major energy-producing substrate and also allows sparing of body protein stores. The mechanisms responsible for this altered pattern of metabolism are probably primarily hormonal in nature, with adrenaline, cortisol and glucagon being the major catabolic stimulants. Some evidence exists, however, for alteration in intracellular pathway metabolism. Within the past decade a new class of mediators of the stress response, the cytokines, has been recognized. These substances are protein products of circulating monocytes and the way in which they integrate into the control of the stress response has not been completely elucidated. At present there is evidence that they can stimulate production of catabolic hormones, and also they may well have direct effects in enhancing protein catabolism in muscle. At present the main method for modification of the stress response remains the provision of energy and amino acid, either intravenously or enterally. In the present state of our knowledge, 30-40 kcal kg-1 day-1 would appear to be adequate for most patients, with half provided as fat. Amino acids 3 g kg-1 day-1 will provide adequate nitrogen. It must be said, however, that the most effective method of modifying the stress response is removal of the source of stress by surgery, antibiotics or other primary therapy.

Identification and assessment of the malnourished patient

The assessment of protein-energy malnutrition has become important for identifying patients whose nutritional status increases their risk of an adverse outcome during hospitalization. Anthropometric, biochemical and immunological measurements, used either alone or in combination are not sensitive or specific enough for monitoring short-term nutritional changes, although some of these variables are associated with an increased incidence of postoperative complications after surgical procedures. The sensitivity of clinical assessment is dependent on the training of the clinician and the outcome variable being sought. For most clinicians, objective measurements are needed to raise their awareness to potential nutritional problems. The relationship of nutritional status to clinical events, particularly stress events during hospitalization, is critical to the interpretation of nutritional measurements and relating them to outcome variables. A classification based on the concepts of nutritional depletion and stress is presented. The prevalence of PEM has been shown to be between 20 and 30% in western hospitals, depending on the population studied and the criteria used to define PEM. In studies which have claimed an association between nutritional status and outcome, the contribution of nutritional variables to the development of postoperative complications has been overestimated and the relevance of technical factors underestimated.

Impaired glucose metabolism in surgical patients improved by intravenous nutrition: assessment by the euglycemic-hyperinsulinemic clamp

Malnutrition is associated with glucose intolerance. This could be related to decreased pancreatic insulin secretion and/or peripheral insulin resistance. We have used the euglycemic-hyperinsulinemic clamp and continuous indirect calorimetry to assess the disposal of an intravenous glucose load in 13 malnourished patients with benign disease (median age, 55 years; mean weight loss 21 kg +/- 8 SD). Seven normally nourished controls were also studied (median age, 62 years) and eight patients were restudied after 14 days on continuous glucose-based intravenous nutrition (IVN). With hyperinsulinemia of 90 microU/mL, malnourished patients disposed of 6.1 mg glucose/kg fat-free body (FFB).min +/- 1.7 SD and oxidized 1.9 mg/kg FFB.min +/- 1.4 SD. Controls disposed of a similar amount of glucose (6.6 mg/kg FFB.min +/- 3.5 SD) but oxidized significantly more (3.0 mg/kg FFB.min +/- 2.3 SD). After two weeks of glucose-based IVN, both glucose disposal rate (9.5 mg/kg FFB.min + 2.3 SD) and oxidation rate (3.9 mg/kg FFB min +/- 1.0 SD) increased significantly. Respiratory quotient was low in malnourished patients (.88 +/- .12), but above 1.0 in controls (1.07 +/- 0.18) and patients after IVN (1.10 +/- 0.11), showing net lipogenesis in these groups. Malnourished patients can metabolize normal amounts of glucose under conditions of hyperinsulinemia and, although carbohydrate oxidation rate is initially impaired, it becomes normal after 2 weeks of IVN.

Body composition research at the University of Auckland--some implications for modern surgical practice

The fundamental changes in body composition which accompany surgical illness are loss of body protein, gain in extracellular water, and erosion of body fat stores. The rate at which each of these processes occurs and the balance between them determine the clinical picture observed and an understanding of them opens the door to intelligent management of many complex disorders. Recent advances in technology have lent impetus to body composition research and a number of new findings have major implications for clinical practice. In this review, some of the work from the body composition laboratories in the University Department of Surgery at Auckland Hospital will be described with special emphasis on that which is directly relevant to the practising surgeon.

The immediate and long-term effects of postoperative total parenteral nutrition on body composition

The short and long-term effects of postoperative total parenteral nutrition (TPN) on body composition were studied in a randomised series of patients undergoing major colorectal surgery. Ninety-two patients (colorectal cancer: 50, ulcerative colitis or Crohn's disease: 42) were grouped according to diagnosis and clinical inflammatory activity. TPN was given for 9.7 +/- 1.1 days. The complication rate was not changed by the TPN. Nitrogen balance was studied during the first week. Body weight, total body potassium, triceps skinfold, serum albumin and body water were measured before and at intervals up to 24 weeks after the operation. Cumulative nitrogen balance in control patients at 7 days after surgery was -47.3 g. Patients given TPN balanced nitrogen intake and output (cancer patients and patients with quiescent inflammatory bowel disease, IBD) or were in positive balance (patients with active IBD). Weight loss at 1 week after surgery was less in TPN patients compared to controls and this difference remained statistically significant up to 6 months after termination of the nutritional treatment. A similar, although not statistically significant, difference was noted in total body potassium and triceps skinfold. Patients with active IBD regained pre-operative body composition earlier than cancer patients and patients with quiescent IBD. It is concluded that TPN after major colorectal surgery reduces postoperative weight loss and that this effect lasts after termination of the nutritional treatment. In the absence of increased body potassium and increased body water, we conclude that the long-term effect of TPN on body weight is most likely due to preservation of fat.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of a lipid containing medium chain triglycerides in patients receiving TPN: a randomized prospective trial

Lipid emulsions which contain long chain triglycerides (LCTs) provide a valuable energy source for patients requiring total parenteral nutrition (TPN). We have investigated the use of a new lipid emulsion containing both long and medium chain triglycerides (MCTs) in a randomized prospective trial. Sixty patients received TPN including 500 ml of either 20 per cent Lipofundin S (LCT) or Lipofundin 10 per cent MCT/10 per cent LCT for at least 6 days. Patients with renal or hepatic impairment, or major trauma, were excluded from the study. The MCT/LCT emulsion was found to be as safe and as effective a source of calories as LCT but the differences in metabolic parameters did not differ significantly between the two groups of patients. A lipid emulsion containing MCTs may have important advantages for seriously ill patients, but appears to have no obvious advantages for the majority of patients receiving TPN who are not severely stressed.

A key to the literature of total parenteral nutrition: update 1987

This comprehensive bibliography is intended to enhance the education of the practitioner, student, and academician in the area of parenteral nutrition. This bibliography is not all-inclusive but serves as an update from the original published in 1983. Of particular note in this work is the addition of topics that reflect a growing interest in medical specialties with regard to patient nutritional status and support.

Improved wound healing response in surgical patients receiving intravenous nutrition

The wound healing response was assessed in 90 surgical patients by measuring the accumulation of hydroxypyroline that occurred over a 7 day period, in fine tubes of thin walled GORE-TEX placed in the subcutaneous layers of the arm. In 47 patients presenting for intravenous nutrition, the wound healing response was less (0.34 +/- 0.23 microgram hydroxyproline/cm of tubing) than that of 36 normally nourished patients (0.49 +/- 0.30 microgram/cm; P less than 0.01). However, it was higher when measured after intravenous feeding had commenced (0.88 +/- 0.62 microgram/cm; P less than 0.005). In 29 patients two sequential studies of wound healing were conducted over a 14-day period of intravenous nutrition. The mean accumulation of hydroxyproline during the first week of intravenous nutrition was 0.36 +/- 0.24 microgram/cm and this was increased significantly over the second week of feeding to 0.78 +/- 0.67 microgram/cm; P less than 0.005. The wound healing response that occurred in wounds made after a period of pre-operative nutrition was better than that which occurred when only postoperative nutrition had been given (P less than 0.02). These results show that the wound healing response in surgical patients requiring intravenous nutrition is improved by this treatment. This improvement is seen after only one week of therapy and before there is an obvious change in nutritional status. It also appears that the improved wound healing response is more marked when intravenous nutrition is given before, rather than after the surgical procedure.

Assessing the efficacy of intravenous nutrition in general surgical patients: dynamic nutritional assessment with plasma proteins

We have compared the direction of changes in four plasma transport proteins measured weekly with the direction of nitrogen balance in general surgical patients receiving intravenous nutrition (IVN). Fifty four patients had IVN for 2 weeks, and 15 had IVN for 3 or 4 weeks. Change in plasma prealbumin followed the direction of nitrogen balance in both weeks of IVN in 39 of 54 of the former group, whereas none of the other plasma proteins achieved 50% accuracy. A weekly rise in plasma prealbumin had a sensitivity of 88%, specificity of 70%, positive predictive value of 93%, and negative predictive value of 56% in detecting positive nitrogen balance. Results in the patients who received 3 or 4 weeks of IVN showed an improvement in negative predictive value to 79%. None of the other plasma proteins performed as well. Twelve patients suffered a major complication of their disease or died, following their course of IVN. Nitrogen balance was the best prognostic indicator of these patients, whereas a fall in prealbumin was the best of the plasma proteins, with a sensitivity of 67%, specificity of 79%, positive predictive value of 40%, and negative predictive value of 92% in determining the incidence of complications. Prealbumin was the most suitable plasma protein for use as a dynamic index of nutritional progress in the type of patient seen in this study.

Whole body protein kinetics in severely septic patients. The response to glucose infusion and total parenteral nutrition

Rates of whole body protein synthesis and catabolism in normal volunteers and in a group of severely septic patients were isotopically determined. In addition, the effect in the patients of either glucose infusion or total parenteral nutrition (TPN) on protein dynamics was assessed. The basal rate of net protein catabolism (NPC) was significantly higher in the septic patients than in the volunteers (p less than 0.05). The values obtained in the volunteers and patients were 1.44 +/- 0.18 and 2.20 +/- 0.10 g/kg/day, respectively. This increase in NPC was primarily due to a major increase in whole body catabolism that was partially counteracted by a modest increase in protein synthesis. When the patients were infused with glucose (4 mg/kg/min), NPC decreased significantly (p less than 0.001) to 1.96 +/- 0.08 g/kg/day, and during TPN the value was significantly lower again (p less than 0.04) (0.63 +/- 0.28 g/kg/day). In each instance the conservation of host tissue was due to an increase in protein synthesis: the accelerated rate of whole body protein catabolism continued irrespective of the nutritional status. The following conclusions were reached from these data: severely ill septic patients have an accelerated rate of NPC compared with normal volunteers, and this is primarily due to a large increase in whole body protein catabolism; TPN is an effective means of conserving host tissue in severely septic patients via the promotion of whole body protein synthesis; despite the beneficial effect of TPN in these patients, whole body protein catabolism continues unabated, and as a result, protein losses still occur at approximately one fourth the rate seen in the absence of TPN; and there is no obvious advantage in terms of protein-sparing when protein is provided in amounts exceeding 1.5 g/kg/day.

Hyperalimentation of jaundiced patients on percutaneous transhepatic biliary drainage

Although percutaneous transhepatic biliary drainage (PTBD) restores hepatic and renal function in patients with obstructive jaundice, it is not certain whether it reduces the rate of complications and death after biliopancreatic surgery. We studied the possibility that the operative risks of jaundiced patients are related to malnutrition and the usefulness of hyperalimentation with PTBD to reduce the incidence of complications. Sixty-four patients with obstructive jaundice and serum bilirubin greater than 200 mumol/l were randomized into two treatment groups (n = 32) with PTBD or PTBD + hyperalimentation. Four patients were withdrawn from the latter group, two for metastatic cancer and two for complications of PTBD. Before starting hyperalimentation, the incidence of malnutrition was assessed by biochemical, immunological and anthropometric tests: malnutrition was found in 70 per cent of the patients. All the patients had good recovery of hepatic function but patients treated with PTBD alone still had high mortality (12.5 per cent) and morbidity (46.8 per cent) after biliopancreatic surgery. When hyperalimentation was provided to patients on PTBD for a period of 20 days before the operation, the incidence of complications fell to 17.8 per cent and mortality to 3.5 per cent. These results suggest that the combined use of PTBD and hyperalimentation, improving both hepatic function tests and the nutritional status of jaundiced patients, can reduce the rate of complications after biliary and pancreatic surgery.

Supplement feeds and nitrogen and calorie balance following femoral neck fracture

A 10 day study of nitrogen and calorie balance has been undertaken in 61 women patients aged 65-96 years (mean age 81 years) with femoral neck fractures. All underwent fracture surgery with an inhalation anaesthetic lasting from 45 min to 2 h. Intake of ward food varied widely but was always low with a mean of 127 mg N kg-1 and 17 kcal kg-1 daily. Daily nitrogen production was 85-250 mg N kg-1 (mean 158 mg N kg-1) and calorie expenditure was 17-48 kcal kg-1 (mean 32 kcal kg-1). These were greatest in trochanteric fracture patients. Of the 61 patients, 90 per cent were in negative nitrogen balance with a mean 8 day deficit of 411 mg N kg-1 and all in negative calorie balance, mean 141 kcal kg-1. The deficits were greatest in trochanteric fracture patients. Sip feeding with supplementary enriched drinks raised protein and calorie intake substantially. Both nitrogen and calorie balance were significantly improved, but large calorie deficits remained; intolerance of the supplements proved to be a handicap in correcting the deficits in many patients.

Total parenteral nutrition in acute illness

Successful total parenteral nutrition in acute illness requires an appreciation of the pathophysiology of the illness and an understanding of the nutritional state of the patient, as well as a knowledge of the principles of total parenteral nutrition. Management of the acutely ill patient's general condition is essential prior to the introduction of nutritional support. A basic regimen which includes administration of 1-2g/kg/day of protein, and 8,400 kJ (2,000 kcal)/day of energy, part glucose and part lipid, together with all minerals, vitamins and zinc, in an appropriate amount of water, should be provided. Modifications to this regimen may be indicated to accommodate cardiac, respiratory, liver or renal failure. The questions of the optimum mix of carbohydrate and lipid, the ideal amount of protein and the correct mix of amino acids for a particular period in an individual patient's illness, are still debated. The fact that recent research supports many of the postulates of the Scandinavian pioneers of total parenteral nutrition suggests we may be returning to a correct approach.

Pocket computers: a new aid to nutritional support

A program has been written to run on a pocket computer (Sharp PC-1500) that can be used at the bedside to predict the nutritional requirements of patients with a wide range of clinical conditions. The predictions of the program showed good correlation with measured values for energy and nitrogen requirements. The program was used, with good results, in the management of over 100 patients needing nutritional support. The calculation of nutritional requirements for each patient individually facilitates more appropriate treatment and may also produce financial savings when compared with administration of a standard feeding regimen to all patients.

Carnitine as a possible adjunct in parenteral feeding

Carnitine is necessary for the transport of fatty acids across the inner mitochondrial membrane, and depletion in response to Intralipid infusion has previously been demonstrated. This study investigates whether orally administered L-carnitine increases tolerance to a lipid load given intravenously. Eight patients with active inflammatory bowel disease, being treated with intravenous prednisolone, were studied. Intralipid was infused on two occasions. Triglycerides and ketone bodies rose in a reproducible manner. Carnitine did not influence these changes. Carnitine excretion rose after an oral dose indicating that carnitine was absorbed, but carnitine excretion was increased in the steroid-treated individuals and rose after oral prednisolone in two healthy subjects. It is concluded that under the conditions of this study oral carnitine is without demonstrable effect on the handling of an intravenous lipid load.