The purpose of this presentation is to give an outline of nutritional support (NS) in hospitalized surgical patients, planning of optimal and cost-effective NS, analysis of controversial topics, practical clinical guidelines and recent developments. Individual study of detailed literature is encouraged. It is hoped that this paper will kindle the curiosity of the reader. Detailed bibliography is given at the end of this presentation.
BIOCHEMISTRY OF STRESS-INDUCED MALNUTRITION
The key biochemical concept to remember in critical care is that stressed starvation is not the same as simple starvation. In the former, hypermetabolism (increase in resting energy expenditure) and hypercatabolism loss of lean tissue, negative nitrogen balance) occur due to hormonal changes. Counter-regulatory (or “anti-insulin” hormones) such as catecholamines, cortisol and glucagon) are all elevated. While circulating insulin levels are also elevated, there is a relative insulin resistance. Unless an attempt is made to decrease this “auto cannibalism”, loss of protein results in death.
A single and reliable biochemical marker of malnutrition is not available. Three factors for nutritional assessment which have stood the test of time are i) weight loss, ii) plasma proteins (total, albumin, transferrin), and iii) Total lymphocyte count.
The classic method of nutritional assessment deals with:
Anthropometric measurements, including weight, triceps skin fold, and midarm muscle circumference. In clinical practice, only weight loss is useful. A weight loss of 5% over one month or 10% over any period of time should alert the physician that the patient is malnourished.
Among the plasma proteins, albumin is the time-tested marker of malnutrition. Levels of below 3 g/dl signify malnutrition. Exogenous administration of albumin to improve nutritional status is unwarranted. It is expensive and does nothing to alter the nutritional risk. Albumin is merely a marker of malnutrition and artificially elevating a laboratory test result does nothing to alter the risks of malnutrition. Albumin has a half life of 21 days. Transferrin (with a half life of 6-7 days) and pre-albumin with a half life of 2-3 days are better markers of depletion and repletion.
Total lymphocyte count (TLC) is obtained by multiplying the total white blood cell (WBC) count and the percentage of lymphocytes. Levels of < 1500 signify malnutrition. Skin testing for delayed hypersensitivity reactions as an nutritional assessment tool is not recommended.
In surgical patients, a high index of suspicion is needed if malnutrition should be detected first. A fat person is not necessarily fit. A patient with multiple injuries, infection, with actual or potential complications, and with organ system dysfunctions, is suspected already to have biochemical malnutrition and hence nutritional support must be initiated immediately.
INDICATIONS FOR NUTRITIONAL SUPPORT
Prospective, randomized and double-blind studies on the efficacy of NS in malnourished patients with curable or reversible disorders are unethical given the present state of knowledge and experience. The following is a gross simplification. NS is indicated in the following patients:
1. A previously well-nourished patient with actual or expected complications, or with “stress” (eg, infections, polytrauma)
2. A previously well-nourished patient who has not consumed sufficient oral nutrition for 5-7 days prior to admission
3. A patient found to be malnourished on admission
ENTERAL versus PARENTERAL NUTRITIONAL SUPPORT
EN is physiological and is superior to PN in terms of cost, decreased complications, ease of maintenance, efficacy of nutritional repletion, and maintenance of organ function. Providing even “token” EN diminishes gut mucosal atrophy and maintains gut integrity thereby preventing translocation of bacteria and toxins from the gut into the circulation. It is this translocation that
results in the “stress syndrome”. Early EN diminishes the cytokine production a key factor in multiorgan dysfunction.
Peristalsis is not necessary for absorption of nutrients from the ileum. If access into the jejunum is achieved, nutrients can be infused in the absence of bowel sounds, immediately after laparotomy and with so-called “ileus”. The presence of an intestinal anastomosis is not a contraindication for early enteral feeding proximal to the anastomosis, using commercially available preparations. While feeding can be started within 6 hrs after surgery, many physicians wait for 24 – 36 hrs before initiating feeding. This gives an opportunity to take care of fluid and electrolytes problems during the immediate postoperative period.
Nasogastric suction (as in the management of stress-induced gastritis, gastric atony, etc) is not a contraindication for distal feeding into the jejunum. With the tubes now available (polyurethane, 120 cms, with stylet) access into the jejunum can be achieved in most patients.
Guidelines for protein, carbohydrate and fat are the same for EN and TPN. The figures for other components refer to suggested IV requirements.
PROTEINS Maintenance, 1 g/kg/day. Stress, 2 to 2.5 g/kg/day
NONPROTEIN CALORIES Maintenance, 25 kcal/kg/day; upto 40 kcal/kg/day. This is provided as carbohydrate or fat. Upto 60% of caloric intake may be given as fat. The nonprotein calorie to nitrogen ratio is 150:1 in unstressed (ie, simple starvation) and 100:1 in stressed patients.
Guidelines for calories have decreased in recent years. The degree of catabolism that occurs in surgical patients does not depend upon the calories administered. Several complications of nutritional support can be avoided by “hypocaloric feeding”. Thus, nutritional support is started at rates of 20-25 nonprotein calories/kg/day. The emphasis is more on protein administration than calories.
ELECTROLYTES Standard requirements plus replacement of intra- or extracellular losses.
MAJOR MINERALS Ca (10-15 mEq/day), P (10-15 mMol per 1000 carbohydrate calories), Mg (15-20 mEq/day).
MULTIVITAMINS Make sure Vitamin K and Folic acid are included.
TRACE ELEMENTS (IV requirements per day): Zinc 2.5-6.5 mg (100 micromol= 6.5 mg); copper 0.5-1.5 mg (20 micromol=1.3 mg); chromium 10-15 mcg (0.2 micromol=10 mcg), selenium 30-100 mcg (0.4 micromol=32 mcg); manganese 0.15-0.8 mg (5 micromol=0.27 mg). Fe is NOT to be used in the presence of infections due to potentiation of gram negative septicemia. Intravenous trace elements are available now in India.
ACCESS Oral, nasogastric, nasojejunal, gastrostomy or jejunostomy (needle catheter or tube). Large bore nasogastric tubes made of poly vinyl chloride should be discouraged. These tubes cause irritation of the oropharynx and esophagus, can result in sinusitis and erosions, and cause gastro-esophageal reflux resulting in aspiration pneumonitis. They stiffen with body temperature.
The routine use of nasogastric aspiration after laparotomy is no longer recommended and in fact pulmonary complications are increased with its use, mainly due to increased gastroesophageal reflux.
The newer polyurethane tubes are more flexible and trans-pyloric positioning is possible with the use of fluoroscopy or endoscopy, in case spontaneous passage does not occur. It is easy to position such tubes in the duodenum at the time of laparotomy. In all patients who are expected to be on ventilatory support or prolonged nasogastric decompression, the timely positioning of a nasojejunal tube at the time of laparotomy is a life-saving maneuver. This tube can be used for regular fluid and electrolyte administration in addition to medications and EN. The prudent surgeon would position a nasojejunal tube at the time of laparotomy when problems with postoperative feeding are anticipated. In many cases a formal jejunostomy can be avoided. If jejunal access is needed in the postoperative period, or in any other situation, positioning can be achieved easily by fluoroscopy or by endoscopy.
Obtaining enteral access for feeding should be a major concern for the general surgeon. Even if the access is not used in some patients due to early resumption of oral intake, the very presence of the access device allows the surgeon to manage fluid and electrolyte problems, as well as nutritional support.
INFUSATES While kitchen-prepared feedings were traditionally used, these are not ideal for various reasons. Blenderized foods need to be given through large bore feeding tubes, with its attendant complications. Supply of feedings round the clock cannot be assured, there is a high risk of bacterial contamination, and the bioavailability of nutrients makes it difficult to supply “dose-specific” nutritional support. Finally, when the cost of preparation, transport, wastage, personnel time, and management of complications associated with large bore tubes is considered, kitchen prepared diets are not less expensive in the hospital environment. Thus there has been an increase in the availability of commercial enteral preparations, designed for use with small-bore feeding tubes.
These are commonly classified as elemental or non-elemental.The term non-elemental or polymeric means that the substance must be first digested before absorption, like usual oral diet. The term elemental or monomeric means that the diet is “digested” and in the form of basic nutrients (aminoacids, simple sugars, etc). Only semi-elemental diets or partly digested feedings are available in India. The human gut is capable of absorbing complex moieties such as dipeptides just as well.
Commercial preparations are available as liquid or powder. In the latter case, it has to be reconstituted with water. Generally, the feedings provide 1 kcal/cc. The electrolyte content of most commercial feedings is low and needs to be added. Most do not contain fiber.
Modular changes in EN (ie, specific addition of protein, fat or carbohydrate as needed to standard commercially available formulas) are required for optimal NS.
Formulas enriched with glutamine (to preserve gut integrity), fiber (to improve tolerance and to stimulate gut mucosa by virtue of degradation to short chain fatty acids) and omega-3 fatty acids plus RNA (to stimulate immunity) are commercially available. Their superiority in all cases of nutritional repletion has not been convincingly proven but the complication (especially infections complications) rate is lower with these immune-enhancing regimens.
i) Aspiration pneumonitis This major complication can be diminished by elevating the head end of the bed by 30 degrees during feeding and for 30 minutes thereafter. The gastric residue is checked every 4 hours before feeding and feeding should be held if the volume of aspirate is over 150 cc. Small bore feeding tubes must be used even if intragastric feeding is contemplated. However, checking for gastric residuals becomes difficult. Transpyloric feeding (especially intra-jejunal) is the best way to avoid this complication. In intubated patients, aspiration is a “silent” killer. Addition of coloring matter to the feeding, and checking the endotracheal aspirate for glucose will assist us in detecting aspiration. Prokinetic agents can also be used.
ii) Diarrhoea A rectal examination is first done to make sure that we are not dealing with “spurious” diarrhea due to fecal impaction where the stool proximal to the obstruction liquefies and is extruded thru the anus. The commonest cause of diarrhea is medications. Most medications in elixir form have sorbitol added to it and this results in a high osmolality which causes diarrhea. The second cause is bacterial contamination of feeds. The “hang time” must therefore be kept at less than 6 hours. Other causes include indiscriminate use of antibiotics. Management of diarrhea is multifaceted. Lactose containing feeds must first be avoided. Smaller quantities of feeding or lesser infusion rates are used. Finally, fiber is a useful treatment for diarrhea (in addition to its well known effect on constipation). The fiber gets converted to short chain fatty acids in the colon which are a source of nutrition for colonocytes.
iii) Constipation This occurs because to too little free water in the enteral feeds and not adding fiber.
iv) Electrolyte Abnormalities Most commercial preparations have less electrolytes. The physician must make sure that the electrolyte (Na, K) requirements are met.
ACCESS Peripheral IV catheters must also be inserted under aseptic conditions and kept in place for not more than 72 hrs. Solutions of osmolality not exceeding 900 milliOsm can be used (approximately a D10% and aminoacid 5% solution). Central venous cannulation and care should follow established protocols. The catheters must be inserted under sterile conditions (mask, gown). The IV tubing must be changed every day while the dressing and extension tubing (between the central venous catheter and IV set) must be changed every 48 hours. Several types of central venous catheters are available. The use of peripherally inserted central catheters (PICC) is especially useful where the catheter is inserted into the antecubital vein and threaded into a central vein.
INFUSATES Several aminoacid solutions with varying concentrations, with or without added electrolytes and major minerals, are available. Solutions available in India include 3%, 5%, 8.5%, and 10%. The physician must make sure of the electrolyte content of these solutions. Absence of Mg and P is especially easy to miss. Dextrose solutions vary in concentration from 10% to 50%. However, it is usually available only in smaller aliquots and not 500 cc bottles which is the volume needed in PN. Fat emulsions are available as 10% or 20% solutions, 100 cc, 250 cc, and 500 cc. Addition of vitamins and multiple trace elements is crucial. When these components of TPN are given by separate infusions, the risk of catheter sepsis is more. However when total nutrient admixtures (described below) are not available, it is better to provide TPN in this manner rather than not provide nutrients at all.
The convenience and safety of 3-in-1 admixtures (also called total nutrient admixture) have made this the correct way to administer PN. The amino acids and dextrose solutions are provided in a large 1 or 2 L bag but separated by a valve or occlusion of two walls of the bag. When this barrier is broken, the minoacid and dextrose are mixed together. Fat can also be added and so can electrolytes, multivitamins and trace elements. Thus, all components of TPN are mixed in one high-volume bag and provided to the patient, avoiding the need for multiple bottles, and multiple rate monitoring. The catheter sepsis rate is far less as there is less handling. Several companies market solutions of various volumes and concentrations.
While there are theoretical reasons to provide branched-chain amino acid-enriched infusates to stressed patients, the cost- effectiveness of its routine use has not been demonstrated.
i) Catheter malfunction due to occlusion, breakage.and sepsis,
ii) Catheter sepsis. If no other source of fever can be identified, it is better to take the catheter out.
ii) electrolyte and mineral deficiency,
iii) glucose intolerance. Make sure the TPN is started slowly and then advanced once blood glucose levels are controlled. Insulin can be added to the TPN. Usually, we check the glucose levels every 6 hrs and give subcutaneous regular insulin as needed. Half the amount of insulin given is added to the next day’s TPN solution. Remember too that hypoglycemia is lethal.
Warning: DO NOT OVERFEED! Hypophosphatemia and hypokalemia can occur with lethal results during the “refeeding syndrome”. This occurs when a chronically malnourished person is suddenly given too much nutrition. this is best avoided by starting slowly (both in terms of volume and caloric density) and then gradually increasing by 20% each day.
MONITORING OF NS
Determining the adequacy or otherwise of nutritional support is difficult as we do not have one single parameter. Clinical improvement is the best parameter. Additionally, the following guidelines can be used.
a) Nutritional monitoring : Weight gain, serum total protein and albumin levels, nitrogen balance, total lymphocyte count
b) Fluid status monitoring : A negative balance during repletion is common due to mobilization of intracellular water. In EN,the amount of free water in infusions is only 75 to 85 % of the total volume.
c) Biochemical monitoring:
i) Acid base and electrolyte status,
ii) Glucose levels,
iii) Renal functions (BUN, creatinine),
iv) Liver functions (blirubin, enzymes)
v) Major mineral status – (Ca, P, Mg), and vi) Serum triglycerides.
d) Hematalogic monitoring: Complete blood count, coagulation functions (prothrombin time).
e) Functional monitoring : Sensorium, improvement in ventilatory muscle function.
MODE OF INFUSION Cyclic vs continuous
Continuous feeding is unphysiological as glucose stimulates release of insulin which in turn decreases lipid mobilization. In cyclic feeding, either the infusion is interrupted for 4-6 hours each day, or a glucose-free solution with decreased amounts of intracellular ions (K, Mg, P) is infused. Better nutritional repletion and a decrease in liver-enzyme elevation occurs.However, managing fluid balance and glucohomeostasis in an ICU patient is difficult with cyclic feeding.
RENAL FAILURE The requirement for protein and energy, especially if the patient is being dialysed, is actually increased! The use of essential aminoacids alone is controversial. Monitor K,bicarbonate, Mg, P and Ca levels.Avoid 1,25-dihydroxycholecazlciferol. Add vitamin B6. Avoid
chromium, decrease selenium.
HEPATIC FAILURE Branched-chain aminoacid enriched infusates result in more rapid recovery from encephalopathy and better nitrogen retention. Cost is a consideration. Intravenous fat is safe as lipoprotein lipase needed for its metabolism is present in capillary endothelium and not in human hepatocytes. Avoid Mn and Cu. Monitor coagulation profile and use vitamin K liberally.
PULMONARY FAILURE Use lipid-based EN or TPN systems to decrease Respiratory Quotient and CO2 production. If too many calories are given, the excess glucose is converted to fat’ this reaction produces a lot of CO2. Thus more fat allows us to give less glucose and avoid this problem. Hypophosphatenmia is a common cause of failed weaning.
DIABETES MELLITUS Add insulin to TPN routinely, at doses of daily insulin dosage x 1.5 x % of patient’s caloric requirements being infused.
ETHICS Philosophies about NS in seriously ill patients should be discussed with the patient’s family especially in terminally ill patients. Prolonging useful life is different from delaying death.
TEAM APPROACH For optimal, safe, and cost-effective TPN and EN, a well-trained team is necessary. The team consists of a well trained dietician, a nurse and a physician with an interest in nutrition. The physician may belong to any specialty. All institutions with tertiary care facilities must have an organized nutrition support team to watch over all patients on EN or PN and to assess all admissions for malnutrition. However knowledgeable and skilful a surgeon may be, without a trained dietician, mortality and morbidity can be expected to be high. A general surgeon practicing without the help of a trained dietician is akin to a cardiovascular surgeon doing procedures without a perfusionist.
COST ISSUES Cost is often quoted as a reason for sub-optimal nutritional support. However, on careful analysis, one sees that patients are often unnecessarily kept in the hospital (both pre- and post operative), undergo unwarranted investigations which do not alter the management plan and receive non-indicated medications. Examples include multiple does of antibiotics for prophylaxis when only one dose may be sufficient; or an IV route of administration when the oral route will suffice. Additionally, PN is used when EN is possible. When these factors are considered, one will realize that it is not the cost factor but the lack of sensitivity on the part of the physician that results in neglect nutritional support.
Providing nutritional support (NS) to all critically ill surgical patients is important as hemodynamic, respiratory and pharmacologic support. Delay in initiating and maintaining effective NS is lethal. No patient is “too sick” to receive NS!
SELECTED READINGS IN NUTRITIONAL SUPPORT
The reader is advised to visit the website of Indian Society for Parenteral and Enteral Nutrition at http://www.ispen.org for links to various other sites and educational material. Membership to ISPEN is encouraged.
ASPEN (American Society for Parenteral and Enteral Nutrition) Board of Directors. Guidelines for the use of parenteral and enteral nutrition in adult and pediatric patients. JPEN 1993; 17(4) (Supplement), 1SA-52SA. (Available from ASPEN’s web site at www.nutritioncare.org and go to Standards.
ASPEN: Nutrition Support Practice Manual, 1998.
Matarese LE, Gottschlich MM (Editors), Contemporary Nutrition Support Practice : A clinical guide. WB Saunders Co, 1998.
Rombeau JL, Rolandelli RH (editors ). 1. Clinical Nutrition, Enteral and Tube feeding (3rd edition), 1997 AND 2. Parenteral Nutrition (new edition expected). WB Saunders Co.
See below for addresses and how to get.
Jeejeebhoy, KN. Nutritional assessment. In Gastroenterology Clinics of North America: Clinical Nutrition, (Ed. Fleming, CR), June 1998; 347-369.
Clinical Nutritional in Practice: Consequences of malnutrition, fasting, stress and disease. Koretz RL. Intravenous albumin and nutrition support: Going for the quick fix. JPEN 1995; 19(2):166-171.
**Medical and Sugical nutritional assessment guidelines from University of Pennsylvania. (Available on Internet, Arbor Nutrition guide>Clinical>Nutritional assessment>Write up guidelines)
**American Gastroenterological Association Technical review on tube feeding for enteral nutrition. Gastroenterology 1995; 103(4):3-21. (Available on the Internet. Go to Arbor Nutrition Guide, Clinical>Surgical nutritional support>Guidelines for the use of enteral nutrition)
Bengmark S. Progress in perioperative enteral tube feeding. Clinical Nutrition 1998; 17:145-152.
Andris DA, Krzywda. Central venous access: Clinical practice issues. In The Nursing Clinics of North America, Clinical Nutrition (Evans-Stoner N, Lysen LK, editors). December 1997, pages 719-740.
Wolfram G. The use of lipid infusions in postoperative nutrition (Editorial comment). Nurition 1998; 14(4): 407-408.
National Advisory Group on Standards and Practice Guidelines for parenteral nutrition. (Approved by ASPEN Board of Directors). JPEN 1998; 22(2):49-66. (Expected to be available on the Internet shortly)
Meadows N. Monitoring and complications of parenteral nutrition. Nutrition 1998; 14(10): 807-808.
DISEASE SPECIFIC NUTRITION
Summary: Mexican consensus on the integral management of digestive tract fistulas, Mexico. 1997. Nutrition 1999; 15(3):235-238.
Mizock B. Nutrition support in hepatic encephalopathy. Nutrition 1999; 15(3):220-228.
Buchman AL. The clinical management of short bowel syndrome: Steps to avoid parenteral nutrition. Nutrition 1997; 13(10):907-913.
**ACCP Consensus Statement: Applied nutrition in ICU patients. Chest 1997; 111:769-778. (Available on the Internet, go to Educational Links of ISPEN’s home page)
For ASPEN publications: Visit ASPEN website
WB Saunders Co is represented in India by:
Harcourt Publishers Ltd, 27 M Block Market, Greater Kailash, New Delhi 110048.
Phone: (011) 646 4550. FAX: (011) 647 5065
Email: [email protected]
ISPEN’s home page: www.ispen.org
** Available Internet
Krishnan Sriram MBBS, FACS, FRCS(C)
Hony Prof of Surgery and Surgical Critical Care
E mail: [email protected]