Key points

Introduction

Any medical condition that leads to dysphagia can directly reduce dietary intake and increase nutritional risk. The complex process that allows for the safe passage of masticated food boluses through the pharynx to the esophagus for subsequent digestion and absorption can be disrupted by several physical and neurologic pathologic phenomena. Moreover, a vicious cycle emerges as malnutrition can worsen the dysphagia itself, leading to increased morbidity and mortality.

Adequate nutrition entails the regular intake of calories in the form of carbohydrates, protein, and fats in addition to consumption of certain essential nutrients, such as water, vitamins, minerals, trace elements, certain amino acids, and certain fatty acids. Adequate nutrition is crucial for the maintenance of homeostasis and a healthy physiologic state. In contrast, a state of malnutrition may arise if one or more of these essential dietary components are consumed insufficiently, whether subtle micronutrient insufficiency or overt, severe, and symptomatic protein-calorie malnutrition. Therefore, the comprehensive care of patients with dysphagia must include diligent nutritional assessment and management to optimize clinical outcomes.

Introduction

Any medical condition that leads to dysphagia can directly reduce dietary intake and increase nutritional risk. The complex process that allows for the safe passage of masticated food boluses through the pharynx to the esophagus for subsequent digestion and absorption can be disrupted by several physical and neurologic pathologic phenomena. Moreover, a vicious cycle emerges as malnutrition can worsen the dysphagia itself, leading to increased morbidity and mortality.

Adequate nutrition entails the regular intake of calories in the form of carbohydrates, protein, and fats in addition to consumption of certain essential nutrients, such as water, vitamins, minerals, trace elements, certain amino acids, and certain fatty acids. Adequate nutrition is crucial for the maintenance of homeostasis and a healthy physiologic state. In contrast, a state of malnutrition may arise if one or more of these essential dietary components are consumed insufficiently, whether subtle micronutrient insufficiency or overt, severe, and symptomatic protein-calorie malnutrition. Therefore, the comprehensive care of patients with dysphagia must include diligent nutritional assessment and management to optimize clinical outcomes.

Prevalence of dysphagia

It is estimated that in the United States alone 300,000 to 600,000 people are diagnosed with clinically significant dysphagia annually. Nearly 70% of these patients are greater than 60 years old.

Common causes of dysphagia include neurologic conditions such as stroke, dementia, cerebral palsy, and Parkinson disease, physical obstruction such as cancer of the oropharynx, chemotherapy or radiation treatment, traumatic endotracheal intubation, or rheumatologic disease such as systemic sclerosis. In the case of stroke, 30% to 65% exhibit dysphagia, which is associated with malnutrition and dehydration, leading to worse overall outcome. Pneumonia, the leading cause of mortality following stroke, is associated with dysphagia and aspiration.

For institutionalized dementia patients, the prevalence of dysphagia has been observed to be as high as 45%, again associated with a high risk of pneumonia and aspiration in this population. Most patients with head and neck cancer experience significant dysphagia that leads to malnutrition during the course of the disease. This dysphagia that leads to malnutrition is especially true during or after radiation therapy, chemotherapy, or surgery. Up to 25% of deaths from head and neck cancer may be attributed directly to malnutrition.

Malnutrition: macronutrient deficiencies

The direct effect of dysphagia on oral food intake places these patients at high risk for malnutrition. In one study of adults with dysphagia, high-calorie oral supplements were given to 30% and placement of a feeding tube was required in an additional 12%. In another group of older adults, protein-calorie malnutrition was present in 19% of those with dysphagia compared with 12% of individuals without dysphagia.

Several methods have been used to assess a patient’s nutritional status and classify their degree of malnutrition as mild, moderate, or severe. Of these, the subjective global assessment (SGA) is easily adapted in most clinical practices. The SGA combines the amount of unintentional weight lost with physical signs of malnutrition (eg, lower extremity edema, muscle wasting), an assessment of GI tract function, and overall health and performance of the patient to provide a nutritional status score.

The nutrition risk index (NRI) is also a useful tool that combines weight loss and a measure of serum albumin according to the equation: NRI = 0.417 × (current weight – usual weight)/(usual weight) × 100 + serum albumin (mg/dL) × 15.9. A patient with an NRI of less than 83.5 is considered severely malnourished. If their NRI is between 83.5 and 97.5, they are considered moderately malnourished.

A third nutritional evaluation tool that has been validated in clinical trials is the Nutritional Risk Screen 2002 (NRS2002). This method incorporates information about unintentional weight loss, severity of illness, and age ( Table 1 ) and is especially useful in hospitalized patients.

Refeeding syndrome

Patients that are severely malnourished for prolonged periods undergo a physiologic compensation that includes catabolism of lean body mass and reduced energy expenditure. These patients are generally deficient in multiple micronutrients and electrolytes, and they are at risk for the development of refeeding syndrome. If adequate nutrition is rapidly reintroduced, cellular metabolic pathways are activated and consume the available micronutrients while driving potassium, magnesium, and phosphorus electrolytes into cells, leading to a rapid decline in circulating levels. Severe hypokalemia or hypomagnesemia may cause cardiac arrhythmias, while hypophosphatemia may lead to muscle weakness and respiratory failure.

Many patients, including those that are only mildly malnourished, may experience a decline in serum phosphorus levels after the introduction of nutritional support; however, this condition of refeeding hypophosphatemia is mild in comparison to the rapid decline in serum phosphorus in severely malnourished individuals. Consequently, refeeding syndrome is potentially fatal. To prevent this condition, nutrition is slowly reintroduced to severely malnourished patients. Current guidelines recommend starting at a daily calorie intake of 10 kcal/kg and advancing over a 4- to 7-day period to the goal calorie intake. Adequate supplementation with thiamine, potassium, magnesium, and phosphorus is recommended.

Macronutrient target intake

An appropriate amount of calories and protein must be consumed to meet daily requirements and expenditures ( Table 2 ). There are several methods that have been developed to estimate a patient’s protein and calorie requirements that are in clinical use. Care should be taken to avoid overfeeding as this may lead to hyperglycemia, hepatosteatosis, accumulation of adipose tissue, and worsened obesity.

A simple and generally accurate estimation of daily calorie requirements is weight-based and is approximated as 25 to 35 kcal/kg, depending on nutritional risk, objectives, and body composition. This estimate generally provides enough energy for metabolic processes to maintain homeostasis with a low rate of overfeeding.

In obese individuals, an adjusted body weight (ABW) is substituted for actual weight, and 25 to 35 kcal/kg of ABW is used to estimate calorie needs. This adjustment is predicated on the increased lean weight that attends increased adiposity and safe, permissive underfeeding to promote lipolysis without excessive restriction in protein based on a corrective factor ( cf ). ABW may be calculated by the following equation: ABW = Ideal weight + ([current weight – ideal weight] × cf ), where published values of cf range from 0.25 to 0.5. In common practice, a conservative value for cf is 0.25.

Because there are no protein stores, patients require dietary protein every day. In general, daily protein intake should be approximately 1 g/kg/d in the nonstressed state, with increased amounts to 1.2 to 1.5 g/kg/d in the stressed state. One exception is for patients with renal insufficiency, who require 0.8 to 1 g/kg of protein daily, and for renal failure patients on dialysis that require 1.5 to 2 g/kg to make up for protein loss in dialysis. Obese stressed patients that are permissively underfed should be given close to 1.5 g/kg of protein to optimize nitrogen balance, nearly always necessitating the use of protein supplements.

Malnutrition: micronutrient deficiency

Patients with dysphagia that reduce their overall dietary intake or selectively choose foods that are easier to swallow are at risk of micronutrient deficiencies. Commonly observed deficiencies include iron, folate, cobalamin (B12), and vitamin D. Other micronutrients, such as thiamin (B1) and zinc, may also be deficient, especially in severely malnourished patients. Even with nutritional support, micronutrient deficiencies may develop that contribute to a decline in the overall health of the patient. Trace metal deficiencies, including iron, zinc, copper, and manganese, have been reported in patients with long-term use of enteral tube feeds.

Empiric supplementation with multivitamins and vitamin D can help to reduce this risk. Periodic testing for serum levels of iron, folate, B12, and vitamin D at 4- to 6-month intervals can ensure adequate micronutrient intake over the course of the disease.

In some individuals, micronutrient deficiencies may contribute to the dysphagia itself. A case of dysphagia that was associated with severe B12 deficiency and resolved with the administration of B12 has been reported. This same phenomenon of reversible dysphagia has also been noted in severe B1 deficiency. Adequate supplementation and empiric treatment of these micronutrients can reduce these effects.

Dehydration

Water is an essential component of the diet that is necessary to replace fecal, urinary, and other insensible fluid losses. Daily water requirements are approximately 30 to 40 mL/kg, depending on age, body composition, and energy expenditure. Some of this is ingested as water contained within foods, which generally provide 15% to 25% of the daily requirements of water, while most is consumed separately as a liquid.

Dysphagia patients are at high risk for dehydration, which represents a common cause of morbidity and rehospitalization in this group. The actual prevalence of dehydration is difficult to quantify because there is no agreement for the standard clinical definition. Some authors argue that an elevated blood urea nitrogen to creatinine ratio (>15) is sufficient for the diagnosis of dehydration, while a more traditional approach involves a complete assessment of electrolytes for hypernatremia, hyponatremia, and renal function, urine studies for highly concentrated urine, and physical examination findings, such as poor skin turgor and dry mucous membranes.

Patients with dysphagia should be evaluated frequently for signs of dehydration, and if present, further evaluation of other nutritional deficiencies may be warranted.

Dietary modification

Components of the diet may be adjusted or modified to facilitate the swallowing process. In general, solid foods are softened and liquids are thickened. Although clinical evidence for this practice is limited, its widespread use is largely based on experience and anecdotal evidence. In one study comparing use of dietary liquids of varying thickness in dysphagia patients, no difference in rates of pneumonia were observed among the different study groups. Some authors speculate that the decreased palatability of these thickened foods and other dietary modifications may contribute to diminished intake and may worsen nutritional status. In one study, the intake of dietary liquids is reduced when thickening agents, such as honey, are added, increasing the risk of dehydration in these patients.

Nutritional supplements

Oral supplements in the form of high-calorie, protein, and micronutrient-containing beverages or puddings are available. These products may be added for regular consumption to the diet of dysphagia patients to augment their nutritional intake.

In patients with head and neck cancer, the addition of oral dietary supplements can reduce weight loss and improve tolerability of radiation therapy and surgery. In patients with dementia, oral supplements reduced cognitive decline and weight loss. The inclusion of oral supplements alongside food during mealtime or with snacks increases their consumption and overall caloric intake.

Dysphagia patients treated with oral supplements that continue to lose weight or that show signs of dehydration or other nutritional deficiencies should be assessed for more aggressive nutritional support.

Nutritional support: enteral feeding

The enteral feeding route is generally preferred for nutrition support. The use of enteral nutrition (EN) in patients with dysphagia can significantly improve nutritional status. A review of feeding practices following stroke that included 33 randomized controlled trials demonstrates the use of enteral feeding through either nasogastric (NG) tube or percutaneous endoscopically inserted gastrostomy (PEG) tube led to increased protein and calorie intake. Although there were no demonstrable differences in mortality, or in functional dependence following stroke, a reduction in decubitus ulcers was noted. Patients with PEG tube feeding also had lower incidence of gastrointestinal (GI) bleeding, higher amount of food delivery, and higher serum albumin levels compared with patients fed with NG tubes.

Patients with long-term and progressive neurologic disorders may also be considered for PEG tube insertion and provision of enteral tube feeds. In advanced neurologic disease, patients are unable to meet daily caloric requirements because of dysphagia coupled with diminished appetite due to effects of the underlying disorders on the appetite centers of the hypothalamus and elsewhere in the central nervous system.

The practice of providing EN to patients with advanced dementia is controversial and is currently not recommended. The use of EN has been advocated in Parkinson disease patients with dysphagia; however, these patients may require higher calorie intake because of a higher resting energy expenditure associated with muscle rigidity or dyskinesias.

Patients with head and neck cancer are at significant risk of dysphagia because of the erosive direct effects of the cancer and the indirect effects of the treatment (surgical, external radiation, and/or and chemotherapy). The prophylactic insertion of a PEG feeding tube before treatment in head and neck cancer remains controversial. In some uncontrolled studies, early PEG tube insertion has been associated with lower than expected weight loss in this population. Two small randomized trials that compare the use prophylactic PEG tube insertion versus no insertion in patients with head and neck cancer have been published. Results of these small trials demonstrate improved quality of life at 6 months of follow-up and slightly lower rates of malnutrition at 6 months and 1 year of follow-up, suggesting the prophylactic management of nutrition may be beneficial in these patients.

The use of NG tubes for enteral feeding has also been advocated in patients with head and neck cancer. The cost of NG tube insertion is approximately 10-fold less than that of PEG tube insertion ; however, because patients tend to require several months of tube feed administration, NG tubes need to be replaced every 14 to 20 days to avoid epithelial erosion.

To date, only one small randomized controlled trial (n = 33) has been published comparing PEG versus NG tube feeding in patients with head and neck cancer. In this study, the group of patients in the PEG tube group lost only 1.25 kg at 6 weeks of follow-up, compared with a loss of 3 kg in the NG tube group. By 6 months, no differences were noted.

Current guidelines recommend that patients with head and neck cancer be given EN, especially during radiation treatment. The decision for mode of delivery, either NG or PEG tube, should be made on an individual basis. If a prolonged duration of EN administration is expected, then PEG placement is reasonable.