Potassium DistributionTotal body potassium in a healthy adult is approximately 50 meqlkg body weight or about 3500 meq for a 70-kg man (1, 2). Most of this is located within cells (Figure 1), primarily muscle, at a concentration of about 150 meq/L. Only 2% of total body potassium is located in the extracellular fl uid, normally at concentrations of 3.5 -5.0 meq/L. The maintenance of this high intracellular to extracellular K concentration depends upon the Na-K ATPase pump (3, 4) as well as other fac tors, including H+ balance, plasma tonicity, and plasma insulin, epinephrine, and aldosterone concentrations (5). The large difference in potassium concentration across the cell mem brane is critical for normal cell fu nction since it is the primary determinant of the resting membrane potential. Small changes in the intracellular/ex tracellular K ratio can severely disturb neuromuscular fu nction, particu larly of the heart. A gain (or loss) fr om the extracellular space of an amount of potassium equal to only I % of the total body K content (35 meq) can cause a 50% increase (or decrease) in plasma K concentration. Such a change would have pronounced effects on neuromuscular func ti on. Like wise, redistribution of a similar amount of potassium fr om the intracellular to extracellular (or vice versa) fluid compartmen t without net gain or loss of K fr om the body, would similarly affect neuromuscular excitability. Thus, it is important that both the total amount of potassium within the body and the distribution of potassium between intracellular and extracellu lar fl uid compartments be closely regulated.In healthy man, potassium enters only via the gastrointestinal tract. Approximately 100 meq of K is ingested per day and essentially all of this is absorbed fr om the stomach and upper gastrointestinal tract. Approxi-521 0066-4219/8 2/040 1-0521 $02.00 Annu. Rev. Med. 1982.33:521-554. Downloaded from www.annualreviews.org Access provided by Haifa University on 01/05/15. For personal use only.Quick links to online content Further ANNUAL REVIEWS

T hese guidelines are designed to help physicians and patients in the evaluation process that leads to renal transplantation. They cover issues pertinent to the assessment of potential adult or pediatric recipients of kidneys from either living or cadaveric donors. Although they are designed to be comprehensive, they cannot cover every possible contingency. Each transplant candidate Is different and faces a unique constellation of clinical and psychosocial challenges resuiting from end-stage renal disease (ESRD). Therefore, it is not possible to strictly define an evaluation process that can adequately meet the needs of each individual patient. On the other hand, the large amount of often conflicting information and issues pertaining to the evaluation of transplant candidates makes guidelines particularly helpful. It is in that spirit that these guidelines were developed. It Is intended that they aid In the evaluation of potential transplant recipients, that they not be too rigidly enforced, and that their limitations be clearly recognized by all potential users. The guidelines were developed by the Patient Care and Education Committee of the American Society of Transplant Physicians pursuant to a mandate of the Society's Board of Directors. Work initially began in August 1993, and was completed in December 1994. The areas covered were arbitrarily divided into several sections. Each member of the committee who wished to participate was assigned to be a primary reviewer for one section and a secondary reviewer for another. An initial version of the guidelines was prepared by combining the sections wrItten by the primary and secondary reviewers. We relied on literature located using MEDLINE and bibliographies in pertinent publicatlons, as well as our personal experiences and the opinions of colleagues. Several draft versions of the guidelines were circulated among all committee members, and each version