Nutrition In Surgical Patients Notes

Nutrition In Surgical Patients Introduction

• The goal of nutritional support in the surgical patient is to prevent or reverse the catabolic effects of disease or injury and to ensure that their nutritional requirements are met using the most suitable route with minimal complications.
• The ultimate validation for nutritional support should be improvement in clinical outcome and restoration of function.
• Nutrition is an important component of the care of the surgical or critically ill patient. Malnutrition can be fatal. Overnutrition can also be harmful. Provision of services of a physician, dietician, microbiologist and good nursing care are vital to patient recovery.

Read And Learn More: Basic Principles Of Surgery Notes

Causes Of Malnutrition

1. Patient is not able to swallow/eat: Carcinoma oesophagus, carcinoma stomach
2. Anastomotic breakdown: Leak after Whipple’s pancreaticoduodenectomy, after colonic or intestinal resections
3. Enterocutaneous fistula
4. Small gut syndrome
5. Debilitating diseases: Crohn’s disease, intestinal tuberculosis, advanced malignancies

Consequences Of Malnutrition Or Pathophysiology Of Gastrointestinal (Gi) Failure

Autocannibalism:

• When gastrointestinal tract (GIT) fails or during starvation, the existing energy stores are consumed to supply energy. Glycogen stored in the liver undergoes glycogenolysis and gets depleted in 24 to 48 hours. Normal physiological functions of the organs of an average adult at rest [Basal metabolic rate (BMR)/ Resting energy expenditure (REE)] need about 20 kcal/ kg/day.
• Therefore, when GIT fails, the fat in the adipose tissue and protein in the muscles and viscera are mobilized and metabolised to supply and sustain REE. This is called autocannibalism (eating one’s own tissues to survive). It weakens the muscles (e.g. respiratory and cardiac muscles), viscera (liver, kidneys, etc.), and immune system, resulting in increased morbidity and mortality.

Patients receiving intravenous (IV) fluids are semi starving:

• 500 ml of 5% dextrose containing 25 g of dextrose provides about 100 kcal (each gram of carbohydrate provides about 4 kcal), and, therefore, an adult kept nil by mouth (NBM) and receiving 4–5 bottles of 5% dextrose/day gets about 400–500 kcal.
• The balance amount of REE (for a 50 kg individual, REE = 50 × 25 = 1250 kcal; 1250 – 500 = 750 kcal) comes from glycogen for 24 to 48 hours and thereafter from autocannibalism which is detrimental.

Fasting in healthy persons versus fasting in patients:

When healthy persons are fasting, the metabolic rate drops to basal level. Although critically ill patients who are kept nil by mouth (NBM) are also resting, their basal metabolic rate is accelerated (hypermetabolic), and their REE is increased proportionately to the level of stress due to injury or illness.

Patient Evaluation

• Every patient admitted to the hospital must have their nutritional status assessed to determine the severity of nutrient deficiencies or excess and to predict the nutritional requirements.

A thorough history:

• History of unintentional weight loss: Weight loss is an important indicator of nutritional status. A recent history of 20% weight loss indicates mild, 20 to 40% moderate, and more than 40% severe undernutrition. Body mass index (BMI) is another easily calculated indicator.
• Mid-arm circumference and triceps skin fold thickness are anthropometric indices that are useful. Low serum albumin (3–3.5 g%—mild, 2–3 g%— moderate, and <2 g%—severe undernutrition) is not a sensitive indicator because of the long half-life and large pool size.
• Prealbumin, retinol-binding protein, and transferrin have shorter half-lives, smaller pool sizes and are more sensitive indicators.
• History of chronic illness
• Dietary habits and any recent changes
• Medication intake

A complete physical examination:

• Assess loss of muscle and adipose tissues by anthropometric techniques such as skin fold thickness and midarm circumference.
• Skin and hair changes
• Neuromuscular functions
• Any organ dysfunction

Biochemical determinants:

• Albumin and prealbumin levels
• Transferrin levels
• Creatinine excretion
• Total lymphocyte count (assess immunologic function)

Estimating Energy Requirements

Several equations can be used to calculate the energy requirement for a given individual. The most widely accepted equation is the Harris-Benedict equation that estimates the resting energy expenditure (REE) or the basal metabolic rate (BMR).

In a normal resting physiological state, the BMR for men and women is as follows.

Men:

BMR = 66.5 + (13.75 × weight in kg) + (5.003 × height in cm) – (6.775 × age in years)

Women:

BMR = 655.1 + (9.563 × weight in kg) + (1.850 × height in cm) – (4.676 × age in years)

• Use of simple formulae such as 25–30 kcal/kg/day to provide nutrients is also acceptable. Another method is by using indirect calorimetry and calculation of nitrogen balance.
• As surgical patients undergo physiological stresses, the value thus derived needs to be multiplied by a stress factor to calculate accurate energy requirements.
• For practical purposes, it is easier to remember that the adult REE is 20 kcal/kg/day and it increases to 25, 30, and 40 kcal/kg/day in mild, moderate, and severe stress.

• For example, a 55-year-old man, with a weight of 60 kg and a height of 170 cm, is undergoing major GI surgery, then his basal caloric requirement is 30 × 60 kg = 1800 kcal. A stress factor of 1.2 can be added for elective major surgery, it becomes 2160, or roughly 2200 kcal.
• How much nutrition to be given: Sixty percent of the total calories should come from carbohydrates and 40% from fats. These calories are nonprotein calories.
• Calories obtained from proteins should not be taken into account for calculating energy needs because they are building blocks in tissue repair and are not meant for burning calories.
• The protein requirement of the resting adult is 0.8 g/kg/day, and it increases to 1.1, 1.5, and 2.1 g/kg/day in mild, moderate and severe stress.
• Recommended daily allowances of vitamins, minerals, and trace elements are added to the formulations. The daily intake and output of fluids should also be calculated and balanced.

Perioperative Nutritional Support

• Preoperative assessment of nutritional status must be done in patients undergoing elective surgery and nutritional support provided in those who are not able to take it volitionally. Nutritional support is given to meet energy requirements for essential metabolic processes and tissue repair and to meet substrate requirements for protein synthesis.
• A healthy adult can withstand semistarvation (receiving IV fluids only) for about 4 to 5 days without ill-effects. Beyond this period, they need nutritional support in order to prevent the adverse effects of autocannibalism. Many patients are nutritionally depleted at the time of admission and will need nutritional support much earlier.
• Cells can perform their function only when they get nutrients and oxygen. When the nutrients are metabolised in the cells, the tissues get energy to perform their physiological functions. Gastrointestinal system (GIT) is the source of supply of nutrients (energy) to all the tissues. It has to supply nutrients on a day-today basis because the body has limited expendable reserves (stores). Lack of nutrients results in energy crisis.
• In critical care units, priority is given to treatment of hypoxia, haemorrhage, haemodynamic instability, fluid, electrolyte, acid–base imbalance, and sepsis. These deserve their priority, but hyponutrition and the consequent energy crisis should not be ignored.
• In healthy, non-malnourished patients undergoing elective surgery, the insult to metabolism begins when the patient is kept NPO from midnight in anticipation of surgery. In cases of GI surgeries, this might be followed by a fasting period in the postoperative period, leading to a starvation period of more than 24 hours. This can strain the starvation response and must be prevented for best outcomes.
• Recent enhanced recovery after surgery (ERAS) protocols allow liquid intake up to 2 hours before surgery, encourage carbohydrate loading preoperatively which help in dampening the metabolic insult. In malnourished patients, although a total correction of malnutrition before elective surgery may not be possible, some form of preoperative intervention can be impactful in selected patients.
• A few factors to be considered are the indication for the surgery, whether elective or emergency (should not risk delaying the surgery to optimise the patient nutritionally in case of life-threatening conditions), the patient’s level of malnutrition, likelihood of it responding to preoperative nutrition and the available options for supplementation.

A few criteria that can be used to initiate preoperative nutrition are:

• BMI <18 kg/m2
• Unintentional weight loss of more than 10% of body weight in 6 months.
• Serum albumin <3 g/dl
• If patient is expected to be unable to meet caloric requirements for more than 7 days perioperatively.
• Catabolic diseases

Role Of Immunonutrition

• Patients undergoing elective surgery benefit from preoperative initiation of immunonutrition as injury induced by surgery leads to significant suppression of immune function.
• It must be initiated 5–7 days preoperatively for optimum benefit. Patients who may benefit include severely malnourished patients undergoing major oncologic GI surgery, head and neck surgery, patients with severe trauma or burns.
• Studies have shown that their administration is associated with reduced rates of infection and other complications and shorter lengths of hospital stay. The nutrients that have been proven to cause improvement in immune functions include:
• Arginine: Supports T lymphocytes; provides substrate for generation of nitric oxide
• Glutamine
• Omega-3 polyunsaturated fatty acids: Promotes synthesis of favourable prostaglandins; decreases production of inflammatory cytokines, etc.

Route Of Administration Of Nutrition

Enteral Nutrition

It is paradoxical that sick patients who need to eat more to meet the increased metabolic demands are often unable to eat. They have anorexia, nausea, vomiting, and altered sensorium. Oral feeding is impossible in patients with faciomaxillary injuries or those on ventilators. In many of them, the intestines are functioning. Enteral route is best for providing nutrition. Hence the dictum, “When the gut is working, use it”.

1. Enteral access: Following are the routes to introduce nutrients into the GIT:

• Nasogastric feeding: When the stomach emptying is normal and swallowing is impossible or contraindicated, nasogastric feeding (Ryle’s tube) provides nutrition.
• Nasojejunal feeding (Fig. 11.4): In gastric stasis, feeding can be given through a nasojejunal (NJ) feeding tube introduced either blindly, under radiologic or endoscopic guidance to place its tip in the jejunum (postpyloric).
• Feeding gastrostomy: By open method or by percutaneous endoscopic gastrostomy (PEG) when RT or NJ tube insertion is impossible.
• Percutaneous endoscopic gastrostomy (PEG): With the help of an endoscope, a gastrostomy tube is placed in a retrograde manner and brought out through a skin incision. It is technically very easy and can be done under local anesthesia. It has replaced feeding gastrostomies (open method). It is popular nowadays. Complications include colonic perforation, sepsis, bleeding, wound infection, etc.
• Feeding jejunostomy: After major/complex operative procedures on the esophagus, stomach, and pancreas, a feeding jejunostomy is frequently established.

2. What to feed: A number of preparations are commercially available but most cost-effective ones are the blenderised kitchen feeds. Enteral feeds are hyperosmolar and provide 1.2 to 2.0 kcal/ml.

•  Polymeric feeds: These are commonly prepared in the kitchen. Liquid and powder preparations are commercially produced. These contain polysaccharides, polypeptides, and oils. Soups of dal, vegetables, and chicken are examples of polymeric feeds.
• Elemental feeds: These are predigested in vitro and contain oligosaccharides, oligopeptides, and medium and long-chain triglycerides (MCT and LCT). They are useful in patients with irritable bowel disease and short bowel.
• Modular feeds: Contain monosaccharides, amino acids, and fatty acids.
• Disease-specific feeds: The composition of the feeds needs to be altered in certain disease states. Renal failure—low protein, low/no electrolytes; hepatic failure—more branched-chain amino acids (BCAA) and less aromatic amino acids; respiratory failure— more fats (55% cal) and less carbohydrates.

3. How to feed: The feeds can be gravitated, injected with a syringe, or pumped into the tubes either continuously or intermittently. Start with 50 ml every 2 hours on the first day and if tolerated, increase gradually to 200 ml every 2 hours until the target is reached.

Advantages of enteral nutrition:

1. The integrity of gut mucosa depends on provision of nutrients into the gut lumen. If the fasting period exceeds more than a few hours, the gut mucosal cells start disintegrating and the villi get destroyed. This may permit the intestinal bacteria to enter the circulation leading to sepsis. Translocation of bacteria from the intestines into circulation has been identified as the ‘motor of multiorgan failure’.
2. Use of natural route of nutrition requires less nursing supervision.
3. Infection rate is lower with enteral nutrition.
4. Greater insulin response is seen with enteral nutrition.
5. There is a lower tendency to retain salt and water.
6. Enteral nutrition is cheaper.

Complications of enteral nutrition: Nausea, vomiting, abdominal distension, and diarrhoea are common. However, intractable diarrhea should be investigated for Clostridium difficile infection. Electrolyte imbalance, hyperosmolar coma, refeeding syndrome, and aspiration are other problems. Mechanical complications include tube clogging, displacement, leak, and erosion.

Parenteral Nutrition

• When enteral nutrition is not possible for more than a few days, parenteral nutrition (PN) may need to be considered. When all nutrition is done by the parenteral route, it is termed total parenteral nutrition. Partial parenteral nutrition may be given to supplement inadequate enteral nutrition.
• Parenteral nutrition (PN) to GI failure is like dialysis to renal failure and ventilator support to respiratory failure. When enteral feeding is not possible, parenteral nutrition should be given. Prolonged ileus, intestinal obstruction, malabsorption, short gut, inflammatory bowel disease, high output intestinal fistulae are some common indications for PN.

PN formulations are marketed as:

1. Dextrose + amino acid solutions (2 in 1 solution)
2. Dextrose + amino acid solution + lipid emulsion (3 in 1 solution)
   • Lipid emulsions are available in 100 to 250 ml bags or glass bottles and contain the essential fatty acids that are milky in appearance.
   • Insulin is commonly added to PN solutions. Heparin is occasionally added.
   • Vitamins may be added to the solutions. Electrolyte requirements must be calculated separately on a daily basis.

Electrolyte Requirements

The daily requirements of various electrolytes are given below.

• Vitamins are given separately. One ampule of watersoluble vitamins must be infused daily, over a period of time exceeding 30 minutes to avoid urinary loss. Folic acid, vitamins B₁₂, K, A, and D need to be given once a week. Trace elements are given weekly to patients on long-term PN.
• The choice of volume and composition of TPN solution must be based on the patient’s metabolic requirement, clinical status, and laboratory parameters.
• TPN orders should be reviewed each day, so that changes in electrolytes or acid–base balance can be addressed appropriately without wasting costly TPN solutions.

Routes of Administration

1. Peripheral vein: Solutions with less than 800 mOsm/L may be administered through a peripheral vein. This is suitable for short-term PN.
2. Central vein: Either internal jugular or subclavian vein is cannulated. PN solutions with higher osmolality must be given through a central vein.
3. Peripherally inserted central vein catheter: This also may be used for short-term purposes.
4. Subcutaneously implanted central vein catheter: Ports are especially suitable for long-term, domestic, or ambulatory PN.

The central venous access should be dedicated to PN and should not be used for administration of drugs or other fluids. This line should be handled with strict asepsis to prevent bacterial growth.

Methods of Administration

• The solutions can be gravitated but the rate of infusion is better controlled if given through pumps. Smaller volumes are given initially and is gradually increased to reach the target volume/day.
• Absolute aseptic precautions are observed while handling the catheters and the PN formulations, since central vein catheter infection is a dangerous complication. Central vein catheter should be used exclusively for administering PN solutions and should not be used for any other purpose.

Monitoring During PN

Aim:

1. To identify excess or deficiency of individual nutrients.
2. To identify complications.

Daily: Blood sugar, serum electrolytes, blood urea, and serum creatinine.

Biweekly: Liver function tests, coagulation profile, complete haemogram.

Merits of PN: Assured delivery of nutrients, accurate and rapid correction of fluid, electrolyte, and acid–base imbalances but it is complicated and expensive.

Complications of PN

1. Technical complications: Injury to subclavian/ carotid artery, brachial plexus, haemo- or pneumothorax.
2. Catheter-related: Central line sepsis is the most dangerous, at times, life-threatening and yet, preventable complication and its incidence is a measure of patient safety. It may not be possible to control sepsis with antibiotics alone without removing the central catheter. Thrombosis and catheter clogging are other problems.
3. Gut mucosal atrophy: Patients on total parenteral nutrition develop atrophy of the intestinal mucosa which loses its barrier function and becomes permeable to bacteria. The consequent bacterial translocation leads to sepsis and multiorgan dysfunction syndrome (MODS). This is not seen in patients on partial PN supplemented with EN.
4. Cholestasis: Some patients on long-term TPN develop cholestasis, jaundice, and gallstones which resolve on starting oral/EN.
5. Fluid, electrolyte, and acid–base imbalances are common.