Metabolic Complications of Parenteral Nutrition

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

Parenteral nutrition is a method of feeding individuals who not not have a functioning digestive tract. This lesson will provide information about the metabolic complications of parenteral nutrition.

Feeding Directly into the Blood Stream

Kendra is a 43-year-old mother of four who was recently diagnosed with intestinal cancer. In the past few weeks, multiple tumors have formed throughout her small and large intestine that have begun to prevent the flow of food through her GI tract. Due to these tumors, Kendra has not been able to eat anything for a few days.

Since Kendra's digestive tract is not functioning properly, doctors have decided to start total parenteral nutrition (TPN). After a couple days of receiving her nutrients through an IV, Kendra's body started to retain a lot of fluid, breathing becomes difficult, she becomes confused, and her heart beat becomes irregular. Kendra was then put through several tests to see what was causing these new symptoms. After reviewing the test results, a doctor informed Kendra that she was suffering from refeeding syndrome, a complication of her TPN.

TPN is used to deliver nutrients directly into the bloodstream in certain severe conditions that affect the GI tract.

What is Total Parenteral Nutrition?

Normal digestion involves a person eating food, their stomach and intestines digesting the food and then absorbing the nutrients found in the food (carbohydrates, fats, proteins, vitamins, minerals). After the nutrients are absorbed, they enter the bloodstream and are taken throughout the body to be utilized to maintain proper metabolism and health.

However, there are certain conditions that can prevent the stomach and intestines from properly digesting and absorbing food. For example, a person might have several tumors in their intestines that prevent the proper functioning of the GI tract (just like Kendra). Since the intestines cannot properly digest food and absorb nutrients into the bloodstream, these nutrients can be infused directly into the bloodstream through an IV, a procedure called total parenteral nutrition (TPN). It should be noted that TPN is usually a last resort and is only used if absolutely necessary.

Complications of TPN

There are several metabolic complications that can occur because of TPN, which include refeeding syndrome and glucose abnormalities.

Refeeding Syndrome

Refeeding syndrome is a metabolic disorder that can occur when a person eats very little for an extended period of time and is then provided high amounts of nutrients very quickly. For example, Kendra had not eaten much for several days and then was provided TPN which infused large amounts of nutrients directly into her bloodstream.

Refeeding syndrome is characterized by a change in the body's metabolism that results in a decrease in potassium, phosphate, and magnesium in the blood. Low blood levels of these minerals can cause many problems in the body, which include:

  • Low levels of potassium: low blood pressure, irregular heartbeat, fatigue, difficulty breathing, confusion, weakness, edema
  • Low levels of phosphate: congestive heart failure, seizures, anemia, coma
  • Low levels of magnesium: irregular heartbeat, cramps, dizziness, confusion, anemia

Glucose Abnormalities

TPN feedings can also cause complications in the way the body metabolizes glucose, which can result in both hyperglycemia (high blood sugar levels) and hypoglycemia (low blood sugar levels).

Hyperglycemia can occur because the TPN supplies the body with a high amount of carbohydrates (sugar) directly into the bloodstream, and the body's insulin cannot work fast enough to get remove the sugar from the blood. Insulin is a hormone that takes sugar out of the bloodstream and brings the sugar into the various cells of the body, such as muscle cells, to be used as energy. Symptoms of hyperglycemia include headaches, fatigue, blurred vision, and increased risk of infection.

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