Obesity Case 4

A 54 year-old woman is scheduled for surgical neck exploration and laryngectomy for the recurrence of a laryngeal squamous cell carcinoma. She was initially treated with external beam radiation to the neck 3 years prior when she was first diagnosed. Over the past 6 months, she has lost 35 lbs, which was attributed to increased dysphagia and reduced appetite during this time. Despite strong support of family members and friends and a large supply of oral nutritional supplements at home, the patient is unable to meet her nutritional needs with oral intake. Her current weight is 93 lbs (42 kg), and her height is 65 inches (165 cm), giving her a body mass index (BMI) of 15 kg/m2 (normal, 18.5 to 24.9 kg/m2).

Her other medical history includes hypothyroidism that developed 6 months after radiation therapy and hypertension. She previously smoked one pack of cigarettes daily for 25 years, but quit 10 years prior. She has mild emphysema and only rarely requires rescue inhalers for symptoms of wheezing.

Her oral medications include levothyroxine, amlodipine, as well as opiate medications for pain. Two weeks prior to her scheduled surgery, the patient is admitted for nutritional optimization and a gastric feeding tube is placed.

Question 1

Which tube feeding regimen should be administered to this patient?

A. Standard tube feed formula (1 kcal/mL)
B. A specialized pulmonary feeding formula fortified with lipids to alter the respiratory quotient (R) and reduce CO2 production.
C. A concentrated formula (1.8 kcal/mL)
D. A semi-elemental formula
E. An immune-modulating tube feed formula, fortified with ω-3 fatty acids, arginine, glutamine, and ribonucleic acids.
Correct Answer
An immune-modulating tube feed formula, fortified with ω-3 fatty acids, arginine, glutamine, and ribonucleic acids.

The choice of tube feed formula can be daunting: a wide array of tube feed formulas are available for clinical use. In most cases, standard tube feeds are equally efficacious to specialty feed formulas, and standard feeds are the most cost effective. The use of specialized feeds is only clinically beneficial in a few specific instances. Some examples of these include the use of low carbohydrate feeds for patients with diabetes or the use of concentrated feeds with low potassium and low phosphorus for patients with renal insufficiency. Formulas with partially hydrolyzed proteins (semi-elemental) or formulas with amino acids and dipeptides as a protein source are more easily absorbed and can be used in patients with reduced intestinal absorptive area or intestinal ischemia and in pediatric populations.

For many other clinical scenarios, evidence for specialized tube feeds is lacking, or in some cases, no specific benefit has been demonstrated. For example, tube feed formulas directed for use in hepatic encephalopathy show no difference in mental status or cognition in clinical trials. In patients with pulmonary disease, use of a specialized pulmonary feeding formula that is fortified with lipids to alter the respiratory quotient (R) does not impact pulmonary function. While less CO2 is produced in the metabolism of formulas with a low R quotient, a higher amount of O2 is consumed. No differences in mortality, quality of life, or other clinically meaningful outcomes have been demonstrated with the use of specialized pulmonary formulas.Over the past few decades, dietary compounds that affect immune system function have been identified in animal studies and in human trials with purported health benefits. These include substances such as ?-3 fatty acids, glutamine, arginine, ribonucleic acids, and other antioxidant compounds.

For many clinical scenarios, however, the use of immune-modulating tube feed formulas remains a subject of controversy. In cases of acute critical illness, septic shock, or acute respiratory distress syndrome, initial clinical trials demonstrate benefit with specific immune-modulating formulas, while subsequent studies show no effect. In contrast, six separate, recently published trials investigating the use of arginine-fortified tube feeds among subjects with head and neck squamous cell cancer consistently demonstrate improved outcomes including reduced surgical complications, reduced fistula formation, and reduced length of hospitalization. Based on these findings, administration of tube feeds enriched with arginine is most appropriate in the patient presented here.

Question 2

In the same patient, tube feeds are started. After 36 hours, the patient develops mild lower extremity edema, and bloodwork demonstrates an electrolyte abnormality. Refeeding syndrome is suspected. 

Which of the following serum electrolyte abnormalities is most often seen in refeeding sydrome?

A. Hyperkalemia
B. Hypophosphatemia
C. Hypocalcemia
D. Hypermagnesemia
Correct Answer
B. Hypophosphatemia

Refeeding syndrome is marked by electrolyte abnormalities that occur in severely malnourished patients as nutrition support is re-introduced. In some cases, edema, diarrhea, tachycardia, and weakness can develop. Any form of nutrition including oral diet, tube feeds, or parenteral nutrition can lead to refeeding syndrome.

During times of fasting or scarce nutritional intake, circulating insulin levels are low and glucagon levels are elevated. Intracellular potassium, magnesium, and phosphate stores are continually utilized, becoming depleted. As intake of food suddenly increases, insulin levels rise significantly. Potassium, magnesium, and phosphate shift into the intracellular space, leading to low serum levels of these electrolytes.Hypophosphatemia is the most commonly described electrolyte abnormality, with a reported prevalence of 96% in a review of 27 refeeding syndrome cases. This results from a sudden increase in phosphate utilization, e.g., the intracellular phosphorylation of newly ingested glucose to glucose-6-phosphate, and through an abrupt increase in synthesis of adenosine triphosphate (ATP).

When severe, the hypophosphatemia in refeeding syndrome can lead to muscle weakness, paralysis, and even death from diaphragmatic weakness and subsequent respiratory failure. Hypokalemia and hypomagnesemia are also commonly observed in approximately half of individuals with refeeding syndrome, stimulated by intracellular shifts of these electrolytes as nutrients are given and insulin levels rise. Serum calcium levels, when corrected for low circulating levels of albumin, are usually not affected.

To avoid refeeding syndrome, nutrients should be introduced slowly, depending on the severity of malnutrition. Electrolyte disturbances can be anticipated: phosphate, potassium, and magnesium supplementation may be given along with the initial nutrition support to avoid refeeding syndrome. Thiamine, which functions as a cofactor in glucose metabolism, should also be empirically administered to address potential thiamine deficiency that can be exacerbated as dietary carbohydrate intake suddenly rises. Careful monitoring of serum electrolyte levels should guide the adjustment of electrolyte supplementation over the initial days of nutrition support in cases of severe malnutrition.