The Power of Protein: nPCR as a Measure of Nitrogen Balance in Hemodialysis Patients
Creators: name: Smith, Marion
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2015

description: Chronic kidney disease (CKD) is defined as the slow loss of kidney function over time. The Centers for Disease Control and Prevention estimates that more than 1 in 10 adults, or over 20 million people, in the United States currently have CKD. The disease is categorized into five stages which are ranked by severity, the last of which is called End Stage Renal Disease (ESRD). There is no cure for ESRD, so these patients depend on renal replacement therapy, either in the form of dialysis or a kidney transplant. In 2011 alone, more than 113,000 patients in the U.S. started undergoing maintenance dialysis treatments. Healthy kidneys are responsible for removing waste products and excess water from the blood. When the kidneys become compromised, a patient’s glomerular filtration rate (GFR) will decline. GFR is a commonly used measure of kidney damage, as it estimates how much blood is passing through the kidneys’ glomeruli each minute. In other words, GFR indicates the rate at which the kidneys are able to filter water and waste from the blood. The National Institute of Health diagnoses CKD in patients with a GFR <60 mL/min for 3 or more months. The most common causes of CKD are diabetes and hypertension, although other diseases and conditions can also harm the kidneys. These include, but are not limited to, polycystic kidney disease, kidney stones and infections, and toxic chemicals. The consequences of CKD are many and spread throughout the body. As a result of excess fluid retention, patients with CKD develop high blood pressure, low blood cell count or anemia, and vitamin D deficiency. Bone health is also negatively impacted. Patients with ESRD typically undergo dialysis when they have only 10-15% of kidney function left. Dialysis has four major roles, in which it helps to (1) remove extra salt, water, and waste products from the body, (2) maintain safe levels of minerals and vitamins, (3) control blood pressure, and (4) produce red blood cells. There are two types of dialysis, peritoneal dialysis (PD) and hemodialysis (HD). PD utilizes the peritoneum, or the membrane covering the walls of the abdomen. By inserting a catheter into the abdominal cavity and filling it with a hypertonic solution called dialysate, waste and fluids are drawn out of the blood through the peritoneum and into the solution. The waste solution is then drained from the body and disposed of. This is in contrast to HD, which uses a dialyzer or “artificial kidney.” In this mode of dialysis, patients are attached to a machine that passes their “dirty” blood through a dialyzer and dialysate solution. It then returns the newly filtered blood back to their bodies. Another important aspect of CKD management involves what patients are eating. Depending on the stage of CKD and/or mode of dialysis, the renal diet requires patients to monitor, and oftentimes restrict, their intake of phosphorus, potassium, and sodium. In general, CKD patients on dialysis require more protein and more calories than their non-dialysis counterparts. This is in part due to the fact that 6-12 grams of amino acids, as well as other nutrients, are lost during each dialysis session. In addition, poor appetite and weight loss are common problems for chronic HD patients. The National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative (KDOQI) recommends that maintenance HD patients consume at least 1.2 grams of protein per kilogram of body weight per day (g/kg/d), at least 50% of which should be of high biological value. This guideline was developed in part based on studies showing that a protein intake between 1.0-1.1 g/kg/d is associated with a neutral nitrogen balance. In regards to energy intake, KDOQI recommends that individuals ≤60 years old consume 35 kcal/kg/d, while those >60 years old consume 30-35 kcal/kg/d. Similar to the guidelines concerning protein intake, it is thought that this level of energy intake is adequate in terms of inducing neutral nitrogen balance and maintaining serum albumin levels. Although controversial, hypoalbuminaemia, or low serum albumin, is commonly used to detect malnutrition in individuals undergoing HD.