Nutritional Demands and Enteral Formulas for Adult Surgical Patients

Introduction:

Early oral feeding is the best mode of nutrition for surgical patients. Lack of nutritional therapy poses the risk of underfeeding in the postoperative course after major surgery resulting in malnutrition. The principle behind nutritional therapy is to shield both nutritional elements and the enhanced recovery after surgery (ERAS) concept by focusing on the special nutritional needs of patients undergoing major surgery to prevent complications and enhance a high recovery rate.

1. The integration of nutrition therapy for the overall management of the patient.

2. Preoperative fasting.

3. Early oral feeding after surgery.

4. Initiating nutritional therapy immediately. If a nutritional risk becomes evident, then it is essential to keep metabolic control, like

1. Blood glucose level.

2. Reduction of factors that aggravate stress-related catabolism or disturb gastrointestinal function.

3. Early mobilization stimulates protein synthesis and muscle function.

What Is the Need for Metabolic and Nutritional Care?

The metabolic strategy reduces perioperative stress and improves outcomes. Thus, prehabilitation may contribute to decreased postoperative complication rates and shortened hospital length of stay (LOS) in patients undergoing major surgery. Still, the fact is that nutritional therapy comprises all active elements and protein and carbohydrates required by the body that has undergone a stress-induced procedure or major surgery. An inadequate nutritional supply will reduce muscle mass (sarcopenia). Thus, malnutrition is associated with bad outcomes, and major surgical stress and trauma will induce catabolism. The extent of catabolism is linked to the magnitude of surgical stress and the outcome.

Is Preoperative Fasting Necessary?

Patients undergoing surgery, where the surgeon guides them for having no specific risk of aspiration, can drink clear fluids until two hours before anesthesia, and solids can be allowed until six hours before anesthesia. Patients at special risk undergoing emergency surgery and those with known delayed gastric emptying or gastroesophageal reflux having a great incidence of aspiration, regurgitation, or associated morbidity or mortality are exempted.

Can We Use Preoperative Metabolic Preparation Using Carbohydrates in Diabetic Patients?

For perioperative discomfort, including anxiety or low blood glucose level, it is required to provide oral preoperative carbohydrates instead of overnight fasting or the night before and two hours before surgery should be administered. Thus evaluation of preoperative carbohydrates or blood glucose levels in patients undergoing major surgery is essential.

Preoperative intake of a carbohydrate drink with 800 ml the night before and 400 ml before surgery does not increase the risk of aspiration, or it is better to switch to fruit-based lemonade as a safe alternative with no difference in gastric emptying time. Thus oral carbohydrates have been documented to improve postoperative outcomes and control blood sugar levels.

How to Fulfill the Nutritional Demand of the Surgery Patient Who Cannot Receive from an Oral Route?

Enteral nutrition (EN) provides essential macro and micronutrients to patients unable to maintain adequate oral intake to satisfy their nutritional needs. EN is typically needed for neurological conditions impairing swallowing, such as stroke and Parkinson's disease, or in case of inability to swallow due to mechanical ventilation and altered mental status. Many commercial EN formulas are available from standard formulations, disease-specific, peptide-based, and blenderized formulas. Enteral nutrition (EN) is crucial for individuals who cannot maintain sufficient nutritious input orally.

EN is used instead of parenteral nutrition (PN), which is associated with an increased incidence of adverse effects such as increased blood sugar level, electrolyte abnormalities, and infection rates, as well as complications such as PN-associated liver and metabolic bone disease. On the other hand, EN is more physiological and helps sustain gut integrity, supporting immune function and protecting against gut atrophy.

What Are the Indications for Enteral Approach?

A variety of physiological or medical reasons may cause inadequate intake.

• Dysphagia.

• Parkinson's disease.

• Conditions such as head and neck cancers.

• Enormously altered mental status due to dementia.

• Mechanical ventilation.

• Hepatic or metabolic encephalopathy.

• Short bowel syndrome (SBS).

• Gastroparesis, and chronic intestinal pseudo-obstruction.

• Age above 70 years.

• Supine position (head of bed not elevated).

• Impaired gastric motility.

What Are the Sites of the Enteral Approach?

Enteral nutrition is required to maintain adequate nutritional status if the patient cannot achieve the nutrition through the oral route. But, if the patient does not tolerate (EN) enteral nutrition, switch to the parenteral route. EN feeding sites are either gastric or post-pyloric. The post-pyloric sites are duodenal or jejunal (behind the ligament of Treitz). The definitive site for feeding relies on several aspects, including the desired EN modality, risk for aspiration, and specific medical conditions. For example, jejunal feedings may be chosen in patients with severe acute pancreatitis to bypass stimulating the pancreas and gallbladder. Based on the enteral approach, the feeding site has specific types of feeding tubes like gastric and post-pyloric. Based on the duration of feeding, it is categorized as short-term and long-term.

What Are the Enteral Formulations?

Enteral formulas differ in caloric content from 1.0 to 2.0 kcal/mL. Formulas are composed of different sources like:

• Carbohydrates: Provides 30 % to 60 % energy carbohydrates with standard or polymeric formulas obtained from sucrose, fructose, solids, or sugar.

• Protein: Formulas deliver 10 % to 25 % energy from protein sources, including milk, whey, casein, caseinates, or soy.

• Fat: Provides 10 % to 45 % energy from fat sources, including canola oil, soy lecithin, safflower oil corn oil.

Based on the formulations:

• Semi-Elemental Formula: Partly hydrolyzed and used for dysfunction in individuals' GI (gastrointestinal) tract.

• Elemental Formula: Fully hydrolyzed and used only for people unable to tolerate semi-elemental formulas.

• Disease-Specific Enteral Formula: Special formulas are known for medical conditions including diabetes, chronic obstructive pulmonary disease (COPD), wound healing, chronic kidney disease, liver failure, and compromised immune system. These products have variable macronutrient and micronutrient ranges established on specific disease states (like high protein for wound healing).

Conclusion:

Metabolism is the principle cycle of the body, which requires essential nutrients to carry out the physiological process and synthesis of the body's building blocks and provide energy. Thus, in major surgery, the body becomes stressed; however, the stress-induced body is more prone to release catabolic hormones and chemical mediators. Thus glycolysis (breakdown of the protein glucose to maintain the energy supply to the vital organ) requires more nutrients to maintain the physiological balance.