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Role Of Total Parenteral Nutrition (TPN) In Critically Ill ICU Patient With COVID-19 Infection

Author: Dr. Santosh Sontakke

DNB (Medicine), DNB (Neurology) Consultant Neurologist Ruby Hall Clinic

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COVID-19 pandemic is affecting the whole world with unpredicted challenges and risk to patients as well as healthcare system globally. The disease primarily affects respiratory system posing the threat of spreading over different organs, deteriorating to multi-organ failure and can be fatal. It is a danger to malnourished elderly people, persons with the low immunity, patients with underlying ailments and chronic diseases. Such patients require special attention under continuous observation in intensive care units. The prolonged ICU stay leads to the demanding nutritional need under such conditions, calling for proper treatment with total parenteral nutrition (TPN).


Total Parenteral Nutrition (TPN), also known as intravenous or IV nutrition feeding, is a method of administering nutrition into the body through the veins. It provides nutrients for patients who do not have a functional GI tract, and enteral feeding is not possible. It provides patients with all or most calories and nutrients through solutions that contain a mixture of protein, carbohydrates, glucose, fat vitamins and minerals.

TPN is a standard tool in the armamentarium of the physicians in their quest for delivery of comprehensive health care to patients. It is sterile liquid chemical formula administered into a vein, generally through a PICC (peripherally inserted central catheter) line, but can also be administered through a central line or port-a-cath.

TPN is used when the intestinal tractis obstructed, or when absorption of nutrients is not carried out properly by small intestine, or when gastrointestinal fistula (abnormal connection) is present. It is used when the bowels need to rest and not have any food passing through them.

TPN is used in malnourished individuals to prepare them for major surgery, chemotherapy, or radiation treatment. It is also recommended for critically ill patients such as, with serious bowel issues, severe burns, multiple fractures, and conditions of demanding nutrition requirement, such as COVID-19.

COVID-19 Patients in ICU Hospital Stay

COVID-19 pandemic is affecting the whole world with unpredicted challenges and risk to patients as well as healthcare system globally. The disease primarily affects respiratory system posing the threat of spreading over different organs, deteriorating to multi-organ failure and can be fatal. This calls for the treatment under continuous observation of the patients in intensive care units (ICU). [1]

COVID-19 is affecting the people of all ages, but mainly posing a risk to malnourished elderly people, persons with the low immunity, patients with underlying ailments and chronic diseases. The individual falling under these categories has a worse prognosis and higher mortality rates. Therefore, these groups of people requires special attention and prolonged ICU stay. [2]

The COVID-19 infection itself and the longer duration ICU admission is associated with cause of malnutrition, loss of skeletal muscle mass and altered function which are associated with poor quality of life, disabilities and morbidities even after ICU discharge.[3]

In addition to it, development of sepsis, inflammation and generation of oxidative stress, further contribute to exacerbation of symptoms and deteriorating condition of patients. This necessitates proper nutritional assessment and treatment to effectively decrease the complications and improve clinical results of the condition. Therefore, giving a special attention to the nutritional needs of COVID-19 patients is of prime importance to reduce the overall casualties. [4]

Nutritional Requirement of COVID-19 ICU Patients Achieved by TPN

COVID-19 patient with severe symptoms needs ICU admission and also for intensified conditions by extended stay during hospitalization; consequently, leads to the demand of nutritional therapy based on their state of health. Following recommendation based on international guidelines for COVID-19 treatment must be considered: [3, 5]


As virus primarily attacks lungs; so, COVID-19 patients have higher energy requirement than normal. The recommended requirement is 84-126 kJ/kg/day (1 kcal = 4.184 kJ).  If there is fever; for every 1°C increase in body temperature, the body’s energy consumption increases by 10%. It is critical for COVID-19 patients to maintain the energy balance. However, considering the increased metabolic load with severe infection, moderately low calories can reduce the metabolic load.


Increased inflammation leads to high catabolic events; and to reduce this, it is of top priority to increase the protein supply. The recommended requirement is 1.3 g/kg/day with a high supply of branched chain amino acids upto 50%. This not only prevents muscle loss but also augment the strength of respiratory muscles.


The recommended requirement is 2 g/kg/day and should not exceed 150 g/day. The administration of carbohydrate should be restricted in critically ill COVID-19 patients with respiratory failure. As oxidation of carbohydrates rises from the production of carbon dioxide, it must be avoided in such patients to drop the respiratory quotients.


The recommended lipid requirement of the critically ill patient is 1.5 g/kg/day. Of these the use of medium and long chain fatty acid should be given priority, with a high proportion of ω-3 fatty acids and ω-9 fatty acids. Essential fatty acids play a major role in immune responses by altering the composition of cell membranes and modulating cell signaling. Arachidonic acid, a ω-6 fatty acid, is arguably the most important eicosanoid precursor to prostaglandins and leukotrienes. On the other hand, ω-3 fatty acids dampen inflammatory responses through their effects on eicosanoid production and specific cytokines.

Fluid volume:

The recommended requirement for stable patients is 30 mL/kg/day of fluid for adult and 28 mL/kg/day for elderly. It is of utmost importance to maintain neutral fluid balance in critically ill COVID-19 patients with specific consideration to renal and prerenal failure. It is recommended to control the amount of intravenous fluids in elderly patients and for large areas of pulmonary consolidation. If there is fever; for every 1°C increase in body temperature, supplement approx. 4 mL/kg fluid.

Non-protein energy supply ratio:

It is recommended to maintain sugar/lipid approximately upto 50-70/50-30 and non-protein calorie/nitrogen approximately upto (100-150)/11.


The requirement of micronutrients in ICU patients depends on the nutritional therapy used. For routine administration supplements of multivitamins and minerals are considered (as complex of vitamin B, zinc, and selenium). The administration of other micronutrients in doses higher than the recommendations should only be carried out if a specific deficiency is present. High-dose vitamin C (3-5 g/d) is recommended as it is effective for ARDS and significantly reduces mortality rate. Administration of vitamin D is also recommended (100.000 IU to a maximum of 500.000 IU within a week); if the level is <12.5 ng/mL (insufficiency). As it improves the adverse clinical outcomes including higher mortality and infection rates, longer mechanical ventilation and hospital stays.


They influence immune system and improve metabolic and nutritional indices, such as nitrogen balance and serum proteins. There are several types of immunonutrients, such as arginine, nucleotides, glutamine, ω-3 fatty acids, etc. Their functions and mechanisms are different from each other. They can inhibit inflammatory responses and regulate immune function, which helps in promoting patient recovery.

Administration of Nutrition

Proper quality and quantity of nutrition not only provided body with immunity to fight disease but also guarantees faster recovery from disease condition, such as COVID-19. In the critical patient admitted to ICU with respiratory insufficiency, if stay last longer than 48 hours as expected, the medical nutritional therapy must be started with the following priority: [5]

  • Early enteral nutrition (EN) must be started within 48 hours, if no contraindications are present.
  • Total Parenteral nutrition (TPN) must be started within 3 to 7 days and must be considered when all strategies for EN have failed to avoid severe malnutrition. For already malnourished patients, it can be started slowly on day 3 and the infusion rate gradually increased up to the 7th day. For patients at risk of malnutrition, with stable clinical conditions, TPN can be started on day 7, by changing the fluid therapy.
  • Both EN and TPN must be prescribed at increasing speeds to avoid overfeeding, and the target speed must be reached in about 3-4 days.
  • TPN is preferred if the necessary requirements are not met with EN.

Total Parental Nutrition Indicated for Critically Ill ICU Patients

The primary reason for TPN in chronically ill patients where enteral feeding is not possible. TPN is useful to boost inadequate oral intake. The successful administration of TPN requires careful assessment of patient, appropriate medical knowledge & experience of its complications. Below is a list of some more relevant indications of TPN: [6]

  1. Newborns with gastrointestinal anomalies such as tracheoesophageal fistula, massive intestinal atresia, complicated meconium ileus, massive diaphragmatic hernia, gastroschisis, omphalocele or cloacal exostrophy, and neglected pyloric stenosis.
  2. Failure to thrive in infants with short bowel syndrome, malabsorption, inflammatory bowel disease, enzyme deficiencies and chronic idiopathic diarrhea.
  3. Other paediatric indications include necrotizing enterocolitis, intestinal fistulae, severe trauma, burns, postoperative infections and malignancies.
  4. Adults with short bowel syndrome secondary to massive small-bowel resection or internal or external enteric fistulae.
  5. Malnutrition secondary to high intestinal obstruction for example achalasia, oesophageal strictures and neoplasms, pyloric obstruction and gastric neoplasms.
  6. Prolonged ileus due to medical or surgical causes (for example post-operative, following abdominal trauma or polytrauma).
  7. Malabsorption secondary to sprue, enzyme & pancreatic deficiencies, regional enteritis, ulcerative colitis, granulomatous colitis, and tuberculous enteritis.
  8. Functional gastrointestinal disorders like idiopathic diarrhoea, psychogenic vomiting, anorexia nervosa.
  9. Patients with depressed sensorium (for example,  following head injury or intracranial surgery) in whom tube feeding is not possible.
  10. Hypercatabolic states secondary to severe sepsis, extensive full - thickness burns, major fractures, polytrauma, major abdominal operations etc.
  11. Patients with malignancies in whom malnutrition may jeopardize successful delivery of a therapeutic option (surgery, chemo- or radiotherapy).
  12. Paraplegics/quadriplegics with pressure sores in pelvic or perineal regions where fecal soiling is a problem.

Contraindications of Total Parental Nutrition

Treating a patient with TPN when it is not indicated is not only frustrating for the doctor as well as the patient, but is also an unnecessary drain on scarce resources. Definite contraindications to TPN include the following:

  1. Where gastrointestinal feeding is possible. Almost always, this is the best route to provide nutrition to the patient. [7]
  2. Patients with good nutritional status in whom only short term TPN support is anticipated.
  3. Irreversibly decerebrate patients.
  4. Lack of specific therapeutic goal: TPN should NOT be used to prolong life if death is inevitable. [8]
  5. Severe cardiovascular instability or metabolic derangements. These should be corrected before attempting intravenous hyper-alimentation.
  6. Infants with less than 8 cm of small bowel as it has been, conclusively proved that they cannot adapt to enteral feeding despite prolonged periods of TPN.

Monitoring of Artificial Feeding and TPN

When an oral diet does not fulfill the energy goal, oral nutritional supplements should be considered first and then EN medication. If there are limitations on the enteral path, it may be recommended to prescribe peripheral PN for the population that does not meet the target energy protein through oral or enteral feeding. Regular monitoring is essential to detect and minimize complications and determine response to nutritional support.

Patients receiving TPN should have their nutritional requirements reviewed regularly, taking into account clinical condition, treatments (e.g. dialysis), drug therapy, nutritional status, response to TPN and supporting laboratory data.

Clinical assessment of the patient can reveal ascites, oedema, impaired wound healing or loss of muscle mass that may not be evident from monitoring weight and biochemical indices see the table below: [9]

When an oral diet does not fulfill the energy goal, oral nutritional supplements should be considered first and then EN medication. If there are limitations on the enteral path, it may be recommended to prescribe peripheral PN for the population that does not meet the target energy protein through oral or enteral feeding.

During the initial step of re-nutrition, most problems can be avoided by close monitoring and sufficient intakes. Infusion rate, body temperature, cardiac and respiratory function, urinary volume, twice daily weight and digestive production must be constantly tracked.

Complication of Total Parental Nutrition

Complications can be classified in four groups: central venous catheter (CVC) associated PN solution stability and drug reactions, metabolic or nutritional and other organ systems.

CVC related complications include infection, occlusion, central venous thrombosis, pulmonary embolism and accidental removal or damage. Metabolic or nutritional complications include deficiency or excess of individual PN components including electrolytes, minerals, glucose, essential fatty acids, vitamins, trace elements and the presence of contaminants.

Infection is one of the commonest complications of CVC’s and is potentially fatal. The occlusion of the CVC that occur inside the CVC. Lumen (blood, substance or PN precipitate) in the vein (a clot or a fibrin sheath) external to the CVC due to the tip

Resting against the surface of the vein or due to external compression Clavicle, for example, or patient positioning.

The target of hormonal and metabolic changes in starvation facilitate survival by reducing basal metabolism price, protein conservation and organ prolongation act, given the preferential skeletal catabolism muscular tissue and depletion of visceral cell mass. PN-related metabolic bone disease (MBD) with decreased bone mineral density ( BMD), osteoporosis, pain and fractures has been identified in adults with long-term parenteral nutrition.

Careful monitoring of hepatic function during PN is highly important in order to mitigate or correct factors responsible for liver disease.


  1. Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020; 395:497-500
  2. Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet 2020 Mar 11. [Epub ahead of print]
  3. Singer P, Blaser AR, Berger MM, Alhazzani W, Calder PC, Casaer MP, et al. ESPEN guideline on clinical nutrition in the intensive care unit. ClinNutr 2019; 38:48-79
  4. Gomes F, Schuetz P, Bounoure L, Austin P, Ballesteros-Pomar M, Cederholm T, et al. ESPEN guideline on nutritional support for polymorbid internal medicine patients. ClinNutr 2018; 37:336-53
  5. Kaiying Y, Hanping S. Interpretation of expert recommendations on medical nutrition therapy for patients with new Coronavirus pneumonia. Nat Med J China 2020; 100: 724-728
  6. Smith LC. Mullen JL. Nutritional assessment and indications for nutritional support. SurgClin North Am 1991; 71:449-58
  7. Heymsfield SB. Bethel RA, et al, Enteral hyperaIimentation: an alternative to central venous hyper› alimentation. Ann Intern Med 1979; 90:63-7
  8. Klein S, Simes I, Blackburn GL. Total parenteral nutrition and cancer clinical trials. Cancer 1986; 58:1378-86