Parenteral nutrition, also known as total TPN or TPN, is a method of feeding patients intravenously, providing nutrients such as glucose, proteins, minerals, and vitamins. It bypasses the usual process of eating and digestion and puts nutrients directly into the bloodstream.
Reasons to Use
Parenteral nutrition is typically used for patients who are unable to receive nutrition through their gastrointestinal tract due to dysfunction, damage, surgery, or illness. Some common reasons TPN is used include:
- Gastrointestinal Diseases: Conditions like Crohn's disease, ulcerative colitis, short bowel syndrome where parts of the small intestine are removed make it difficult for the body to absorb enough nutrients through oral intake. TPN provides an alternative method to meet the nutrition needs of the patient.
- Post-Surgery Recovery: Patients undergoing major gastrointestinal surgeries like bowel resection often need TPN during recovery to allow the gastrointestinal tract time to heal without digestion duties. This prevents malnutrition during convalescence.
- Chronic Pancreatitis: Inflammation and damage to the pancreas may impair its ability to produce digestive enzymes that break down food for absorption. TPN provides sustenance until the pancreas heals sufficiently or in severe long-term cases.
- Severe Malnutrition: For patients too malnourished from conditions like cancer, AIDS or poverty, putting calories and Parenteral Nutrition straight into the blood may be life-saving until oral intake is feasible again.
- Neurological Issues: Disorders affecting swallowing ability or consciousness levels can make eating unsafe and lead to undernutrition without parenteral alternatives.
Administration Process
Parenteral nutrition is delivered via a central venous catheter or PICC (peripherally inserted central catheter) line placed in a large vein, usually in the arm or chest. Different types of central venous access devices are surgically implanted based on planned duration of TPN:
- Peripherally Inserted Central Catheters (PICC): Flexible tubes inserted into arm veins for 4-6 weeks of parenteral feeding.
- Tunneled Central Catheters: Longer tubes surgically placed under the skin and exiting the chest for 2-12 months of use.
- Implanted Venous Access Ports: Ports placed completely under the skin and accessed periodically for long-term parenteral needs.
Nutrients are mixed as a compounded sterile solution and infused through the catheter over 8-24 hours, usually using an ambulatory infusion pump. Electrolytes, minerals, vitamins and other additives are adjusted according to the patient's individual medical condition and labwork.
Monitoring with Parenteral Nutrition
Proper monitoring is essential with TPN to monitor for any reactions or complications and ensure therapy is meeting nutrition goals. Patients receiving TPN require:
- Frequent Bloodwork: To monitor electrolytes, liver and kidney function, infection markers and adjust nutrient levels appropriately.
- Fluid Balance Tracking: Daily weight, intake and output must be measured to maintain optimal hydration and avoid fluid overload or dehydration.
- Infusion Site Checks: The catheter exit site and surrounding skin are examined daily for signs of infection like redness or tenderness.
- Nutrition Assessment: Periodic review of calories, protein intake and other labs to ensure patient is gaining or maintaining adequate weight and nutritional status on the parenteral regimen.
Complications of Parenteral Nutrition
While lifesaving for many, TPN also carries risks if not managed carefully. Some potential complications that may require intervention include:
- Catheter-Related Bloodstream Infections: Bacteria can enter through the catheter and cause sepsis if proper sterile technique is not followed for access and care. Antibiotics are usually needed.
- Liver Problems: Excess glucose can cause fatty liver infiltrations called steatosis, and prolonged use increases risk of gallstones or cholestasis requiring intervention or even transplant.
- Metabolic Derangements: Fluid, electrolyte and mineral imbalances can occur from too rapid or prolonged infusion or inadequate monitoring leading to issues like refeeding syndrome.
- Vein Damage: Long-term central access can lead to thrombosis, stenosis or extravasation requiring catheter replacement or open/endovascular vein repair.
- Pulmonary Embolism: Blood clots forming on catheter tips have potential to dislodge and lodge in pulmonary circulation, sometimes fatally.
So while TPN prevents or treats malnutrition, close vigilance and protocol adherence are necessary to minimize risks and allow safe, effective use as a life-extending medical therapy. With proper patient selection and multidisciplinary oversight, it provides critical care not otherwise possible.
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