Nutritional assessment and management in liver transplantation
Patients eligible for solid organ transplantation are functionally end-stage regarding the organ to be transplanted. Being chronic patients, they usually display malnutrition to some extent (1). Weight loss and other malnutrition signs are considered predictive factors for poor prognosis regarding the outcome of surgical patients, including patients undergoing a solid-organ transplant (2,3). The presence of malnutrition is associated with increased morbidity and mortality, and higher healthcare costs (4). Major malnutrition causes in patients with advanced liver disease include inadequate dietary intake -from anorexia, from drugs and therapy-related dietary changes, or from disease complications- and main nutrient-related metabolic changes (5).
Regardless of the underlying disease, a diagnosis of malnutrition is established by a combination of various methods: medical record, anthropometric measurements, biochemical parameters, and body composition. As de Luis et al. suggest in this issue of REED (6), end-stage liver disease itself may greatly modify many of these indices. Ideally, accurate body composition techniques such as K measurement40 or deuterium concentration should be used. Unfortunately, such techniques require complex equipments available only in a few centers.
However, such technical limitations do not justify the omission of nutritional assessments in patients eligible for liver transplantation. Nutritional screening tests are a good tool for the initial assessment of a patient's nutritional status, even when they are not specifically indicated for advanced chronic liver disease (7,8). Anthropometric measurements may also be useful, except when water and salt retention are significant (9). In contrast, plasma concentration measurements regarding some proteins are not so useful in these patients. DXA (dual-energy X-ray absorptiometry) is a method for body composition analysis based on the measurement of a body property, rather than a body component. Many hospitals have this instrument to assess bone mineral density, and it also provides sound information on other body components, including fat mass (10). While some experiences with this method have been reported in patients with cirrhosis (11), its accuracy for patients with water and salt decompensation remains to be definitely established. On the other hand, the accuracy of a bioimpedance analysis depends on the applicability of the regression equation relating current resistance through the body to body composition parameters. This method may scarcely sensitive for the detection of brisk water volume changes, particularly in the abdomen. Despite this, some groups advocate for its usefulness in the assessment of patients with advanced liver disease (12).
De Luis et al. have assessed 31 candidates to liver transplantation using nutritional screening tests, anthropometric and biochemical measures, and bioimpedance analysis. Overall, patients in this small series had an acceptable nutritional status. These findings are in contrast with those by other authors (13,14) who did find a high malnutrition percentage. This difference may be due to a number of factors: various populations and severities, small sample size, and different etiologies for liver disease. Of 31 patients studied by De Luis et al., disease etiology is other than alcohol use in 41.1%, and 35.5% are in Child's A or B stage. The transplantation protocol in their hospital may include preoperative nutritional support with specialized dietary counseling and home enteral nutrition when needed. In fact, energy ingestion is over 25 kcal/kg/day, and protein ingestion exceeds 1 g/kg/day in most cases.
The notion accepted among the various Spanish centers with liver transplantation programs is that malnutrition persists in a relevant percentage of transplant candidates. The incidence of malnutrition varies with the origin of liver disease. Hence, a nutritional status assessment is very useful in all candidates. Those with malnutrition or risk thereof during the waiting period may benefit from specific nutritional treatment. Salt, water or protein restrictions should only be started when needed for complications control. Carbohydrate ingestion before bedtime may be of interest in order to reduce gluconeogenesis. If a dietary analysis shows inadequate energy, protein, zinc, folic acid or fat-soluble vitamin consumption, nutritional supplements to palliate such nutritional deficiencies may be considered. Mixtures containing branching amino acids and carbohydrates would only be indicated for patients developing chronic liver encephalopathy symptoms despite moderate protein intakes. Patients with compensated liver disease may have a positive nitrogen balance with no encephalopathy (15).
]]> Overall, recommendations regarding nutritional supplements among liver transplant candidates are based on expert suggestions rather than prospective, randomized clinical trials. Available results suggest an improvement of nutritional variables, and a trend to decreased mortality; however, samples in these studies are small (16). A preliminary study has shown that liver transplants may be prepared using oral supplements with immunonutrients, which would facilitate nutritional status improvement, and recovery following transplant; they would also reduce post-surgical infection (17). On the other hand, in patients with a transjugular portosystemic shunt enteral nutrition results in greater ammonia levels versus parenteral nutrition, and the parenteral route may have metabolic advantages should some of these patients require artificial nutrition (18).Once the transplant has been completed, nutritional treatment, together with an appropriate immunosuppressing therapy, should contribute to the prevention and treatment of obesity, diabetes, and dyslipemia, as these metabolic disturbances may commonly develop in such patients (5).
M. León Sanz and M. A. Valero Zanuy
Unit of Clinical Nutrition and Dietetics. Hospital 12 de Octubre. Madrid, Spain
References
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