Deciphering Parenteral Nutrition : A Comprehensive Guide to Intravenous Nutrient Administration

1. What is Parenteral Nutrition?

   Parenteral nutrition is a form of medical nutrition therapy involving the administration of essential nutrients directly into the bloodstream, bypassing the digestive system.

   If a person needs supplemental nutrition, a doctor may recommend feeding through tube or oral supplements.⁽¹⁾ If these do not provide adequate nutrition, parenteral nutrition is suggested by the doctor. The nutrition provided through parenteral nutrition includes a combination of carbohydrates, proteins, fats, vitamins, and minerals, tailored to meet the specific nutritional needs of the individual.⁽²⁾

   Parenteral nutrition is crucial in sustaining individuals who cannot consume or absorb nutrients through conventional means, ensuring they receive the necessary components for energy production, tissue repair, and overall health.

2. Importance of Intravenous Administration

   Intravenous administration involves delivering substances directly into the bloodstream and is crucial in various medical contexts due to its rapid and efficient delivery mechanism. Key aspects highlighting the importance of intravenous administration include: 

   • Intravenous administration allows for the rapid onset of action. Medication, fluids, and nutrients introduced directly into the bloodstream can reach the target organs or tissues, providing therapeutic effects.
   • It allows precise control over the dosage of medications or nutrients delivered. It plays an important role in critical medical situations where accurate dosing is crucial for patient safety and treatment efficacy.
   • Quickly administering life-saving medication and fluids ensures a rapid response when time is of the essence.
   • Giving parenteral nutrition allows for the direct delivery of substances without relying on the digestive system.
   • It provides healthcare professionals with the ability to manage patients’ conditions closely and respond rapidly to changing needs.
   • It is often seen in chemotherapy, long-term antibiotic therapy, or sustained fluid support.
   • Parenteral nutrition is more convenient for patients especially if they have difficulty swallowing medications or if frequent dosing is required.
   • Intravenous administration often ensures higher bioavailability of medications compared to other routes.

There are different types of parenteral nutrition, each serving specific needs and conditions. The two main types of parenteral nutrition:⁽³⁾

• Total Parenteral Nutrition (TPN): It is indicated when a patient is unable to meet the nutritional needs through the gastrointestinal tract. It is commonly used in cases of severe malnutrition, gastrointestinal disorders, or when the digestive system needs rest and healing.

It contains carbohydrates, protein, lipids, vitamins, minerals, sodium, potassium, chloride, zinc, copper, and selenium.

TPN is administered through a central venous catheter to ensure proper and safe delivery. Care monitoring of electrolyte levels, blood glucose, and liver function is needed while giving TPN. An individual’s specific nutritional needs are taken into consideration while tailoring the infusion rate and composition of TPN.

• Partial Parenteral Nutrition (PPN): PPN is used when the patient’s nutritional needs can be partially met through the gastrointestinal tract, but oral intake is insufficient. It is suitable for patients with mild malnutrition or those transitioning from TPN to enteral nutrition (oral or tube feeling).

The components of PPN are similar to TPN but are lower in concentrations. It provides a supplemental source of macronutrients and micronutrients.

PPN is administered through a peripheral venous line, making it less invasive than TPN. The administration should be monitored for complications such as phlebitis or infection.

As there is an improvement in the patient’s gastrointestinal function, there is a gradual transition from parenteral to enteral nutrition. This helps in preventing complications associated with prolonged parenteral nutrition. The patient’s ability to tolerate enteral nutrition should be monitored. Adjustments should be made based on oral intake, gastrointestinal function, and nutritional needs.

Patient selection and assessment are critical steps in determining the appropriateness of parenteral nutrition and ensuring its effectiveness and safety.

• Patients who are not able to consume or absorb nutrients through the digestive system due to conditions such as severe malabsorption, gastrointestinal disorders, or surgical interventions are considered for parenteral nutrition.
• Also, individuals with short bowel syndrome, high-output fistulas, or bowel obstructions that limit the absorption of nutrients are considered.
• It can also be considered in instances where the digestive system needs rest and healing and oral or enteral nutrition is not feasible or advisable.

• Laboratory parameters such as protein status, assessment of anemia and overall blood health, metabolic complications, and liver function tests are assessed.
• Weight, height, body mass, skinfold thickness, and ability of individuals to perform daily activities are assessed. The presence of conditions such as diabetes or renal impairment is evaluated.
• Collaboration is made with a multidisciplinary team including dieticians, physicians, pharmacists, and nurses to comprehensively assess and address the patient’s nutritional needs.

• Special attention is given to age-specific nutritional requirements and potential complications.
• Intensive care unit patients may have unique nutritional needs and challenges. A regular reassessment is crucial.
• To adjust the regimen of parenteral nutrition, regular reassessment of nutritional status is needed.
• As the gastrointestinal function improves, there should be a gradual transition to enteral nutrition.
• Discussion should be done with the patients and their families regarding the goals of care, potential benefits, and risks of parenteral nutrition.

The formulation and compounding of parenteral nutrition involves a careful preparation of intravenous solution containing essential nutrients to meet the specific nutritional needs of individual patients. 

• It may contain macronutrients including carbohydrates, protein, and lipids, and micronutrients including vitamins, minerals, trace elements, and electrolytes. Adjustments are made in osmolarity and tonicity to ensure the solution is safe for administration.
• Formulations are tailored according to individual requirements and health conditions.
• The compatibility of all the components is ensured. Strict sterile compounding procedures are maintained to prevent microbial contamination.
• Compounding is carried out by trained pharmacists and pharmacy technicians.

Parenteral nutrition is considered less ideal than enteral because of the complications involved. The common complications include: 

• Infection is the primary concern. Bacteria from the IV catheter can infect the bloodstream. As the infection spreads throughout the body, it can lead to sepsis, a life-threatening condition.
• Blood may clot at the site where the catheter meets the veins.
• Gastrointestinal atrophy can begin occurring after about two weeks.
• Glucose imbalances are common and can be treated with insulin and dextrose adjustments.
• There can be transient liver reactions to the nutritional formula. It can be managed by adjusting the formula.
• Parenteral nutrition-associated liver disease is a complication that can occur due to long-term parenteral nutrition. It affects 50% of patients after 5-7 years.⁽⁴⁾
• Gallbladder problems can result due to the lack of stimulation from the digestive system, causing bile to accumulate without being released normally into the small intestine.
• There can be bone demineralization in people who receive long-term parenteral nutrition. This may be due to vitamin and mineral deficiencies.

Other possible complications may include: 

• Injury during catheter insertion
• Reaction to lipid emulsions in the formula
• Fluid overload
• Hunger pangs

After successfully being weaned off parenteral nutrition, the healthcare team continues to monitor the weight and nutrition levels of the patient for a while to make sure oral nutrition and hydration are sufficient.

Someone with liver complications during parenteral nutrition may have higher enzyme levels persisting for years.⁽⁵⁾

In conclusion, parenteral nutrition plays a vital role in providing essential nutrients to individuals who are unable to meet their nutritional needs through oral and enteral routes.

Total parenteral nutrition and partial parenteral nutrition are two main types that are tailored to specific clinical scenarios.

Patient selection and assessment are crucial steps and involve a comprehensive evaluation of the individual’s medical history, nutritional status, and specific needs. This helps in ensuring that parenteral nutrition is appropriately prescribed for those genuinely requiring it.

The formulation of parenteral nutrition is highly individualized with careful consideration given to the patient’s age, weight, medical condition, and specific nutritional requirements. The compounding process is carried out in hospital pharmacies following stringent aseptic techniques and quality control measures to prevent contamination and ensure the stability and compatibility of the solution.

The patient is closely monitored during the administration of parenteral nutrition and adjustments are made if essential. There are a few risks associated which should be taken care of.

While discussing parenteral nutrition with a doctor, a person should consider asking the type that would suit the best according to the health and lifestyle needs, different methods, and ways to limit complications.