Ask the Expert: Nutritional Assessment in Patients With Pulmonary Arterial Hypertension Facing Transplantation

Obesity is epidemic in the United States,12 and a recent analysis of patients enrolled in the Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL) demonstrated significantly more underweight (defined as body mass index [BMI] <18.5) and obese (defined as BMI >30) than age- and sex-matched controls from the National Health and Nutrition Examination Survey (NHANES).3 Specifically, idiopathic PAH (IPAH) and drugs and toxins-associated pulmonary arterial hypertension (PAH) were more likely to be obese, and those individuals with connective tissue disease-associated PAH and congenital heart disease-associated PAH were more likely to be underweight.3 These data suggest that clinicians treating patients with PAH are very likely to encounter patients who are obese or underweight. Historically, lung or heart-lung transplant has been a treatment option facing many of these patients with life-threatening right ventricular (RV) failure. With effective medical therapies for PAH, patients who might have died from RV failure may succumb to comorbidities instead,4 and subgroups of PAH patients with portopulmonary hypertension present a growing population of potential abdominal organ transplant candidates.

The ideal approach to managing patients who are underweight or obese to optimize their candidacy for abdominal organ transplant is far from clear. There is a paucity of data regarding optimal nutritional strategies in patients with PAH; most of the guidance regarding nutritional screening in patients who are potential solid-organ transplant candidates is derived from the general transplant medical literature, which suggests that obesity and underweight affect post-transplant outcomes.5–8

To address the potential nutritional risks, dietitians often set goals that include maintaining the weight and lean muscle mass of patients with adequate nutritional status, promoting weight and muscle gain in underweight patients, and developing strategies for weight loss in obese individuals. The resulting goal-oriented diet and exercise plans are developed with the interdisciplinary care team, which includes dietitians along with active participation of physicians, nursing professionals, physical therapists/exercise physiologists, psychologists, and respiratory therapists. The process emphasizes promoting an overall healthy metabolism, which (for example) includes normalizing blood sugars and managing patients' symptoms.9

While the assessment of patients is individualized, it generally begins with a calculation of BMI, assessment of pattern adiposity for those who are obese, measurement of lean muscle mass (eg, triceps skin fold and mid-arm muscle circumference), a detailed dietary intake, and a comprehensive assessment of laboratory values—emphasizing pre-albumin levels. Attempts to standardize some anthropometric assessments to determine lean muscle mass, such as bio-electrical impedance analysis and dual-energy x-ray absorptiometry (DEXA), have been hampered by the variable fluid status in patients with cirrhosis and renal failure. The importance of an overall clinical assessment of these chronically ill patients is recognized.9

When the initial assessment has been completed and compared with the eligibility criteria of a specific organ transplant program, a plan is often developed focusing on maintenance, repletion, or reduction in weight.9–11 The nutritional plan will likely focus on reaching a specific goal weight, determining the appropriate daily calorie, protein (and fluid) requirements, and thorough dietary counseling, which may include the review of adequate portion sizes, food and beverage choices, meal pattern/consistency, and the importance of staying active. The success of the plan will likely be affected by the patient's severity of illness, commitment to the plan, and the degree of involvement of the interdisciplinary team. As one might expect, a patient's personality and/or changing illness may necessitate changes to the initial nutritional plan, making flexibility and adaptation other key ingredients to success. The safety and efficacy of weight-loss medications, especially in view of the data regarding certain anorexigens and the risk in development of PAH and of weight-loss surgery have yet to be determined. This does not exclude consideration of such approaches in the future as the indications for bariatric surgery in patients with PAH continues to evolve.12

In summary, an increasing number of obese and underweight patients with PAH are likely to require abdominal organ transplant. Optimizing their weight and nutritional status may be required for them to become, or remain, transplant candidates. A set of nutrition evaluation questions are relevant to a majority of these patients (see box), although the points of emphasis and specific BMI or metabolic goals may vary based on the proposed type of organ transplant and individual transplant program criteria. A cooperative and comprehensive interdisciplinary approach with early intervention is an achievable goal and will likely optimize the outcomes for patients with PAH undergoing transplantation.