pET -A Simpler Approach for Determining Prescriptions. 187. TABLE 1 Adequacy of dialysis. TABLE u Clinical criteria of dialysis adequacy. 1. Prescription.
Zbylut J. Twardowski
PET - A Simpler Approach for Determining Prescriptions for Adequate. Dialysis Therapy
Fast Pet test is a modified version of original PEl. Only
.one dialysate sample for glucose and creatinine is taken from the total drained dialysate and a blood sample at the end of the test exchange. It can be used both for diagnostic and prognostic purposes. The Pet and clearance measurements are complementary studies which can guide in dialysis prescription.
Keywords Adequacy of dialysis, peritoneal equilibration test, clearance, fast PET
CLINICAL RESULTS (LONGEVITY, WELLNESS)
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From the Division of Nephrology, Department of Medicine, University of Missouri, Hany S. Truman Veterans Administration Hospital, Dalton Research 41 Center, Columbia, Missouri.
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AMOUNT OF DIALYSIS (ARBITRARY UNITS) -
Optimal dialysis The relationship between the amount of dialysis and clinical results is presented in Figure 1. According to this theoretical approach optimal dialysis is defined as the amount of dialysis yielding clinical results which cannot be further improved. The results would be measured by comparison of longevity, morbidity, and general wellness in dialysis patients to those in general population. By the amount of dialysis I accept not only the dose of dialysis (average weekly clearance/standard body surface area, or weekly KTN, or volume of peritoneal dialysis solution per week), but also weekly distribution of dialysis sessions (continuous, infrequent intermittent, daily, nightly, or twice daily). Such an evaluation has not been performed yet. There are three possible outcomes of such a study (if it is ever
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1 Clinical results in relation to amount of dialysis.
done): I) constant increase in dialysis would give consistently better results but at some point tiie improvement would be so small that the benefits would not be easily discernible; 2) best maximum would be an amount of dialysis beyond which further increases In amount of dialysis would not result in further improvement; and 3) overdialysis would occur when increasing dialysis beyond a given point cause clinical deterioration. Do we provide optimal dialysis? There is no answer to this question but it is verj likely that we are far from optimal dialysis. Adequacy of dialysis Because we are forced to keep the cost and time of dialysis within reasonable limits we do not even attempt to provide optimal dialysis, we only try to provide merely adequate dialysis. According to Webster' optimal' means most desirable or satisfactory, 'adequate' means sufficient for a specific requirement, barely sufficient or satisfactory. But
pET-A Simpler Approach for Determining Prescriptions TABLE 1
Adequacy of dialysis
1. Prescription • Fulfills criteria
2. Criteria ./ A priori:
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• Acceptable clinical and laboratory condition A posteriori: • Satisfactory morbidity, longevity, and wellness
187 TABLE
Positive
Absence of
./ 'Feels weU, looks good' ./ Well controlled blood pressure ./ Stable lean body mass
-Anorexia - Astheny - Dysgeusia -Emesis -Insomnia -Nausea
TABLE
what does adequate dialysis mean, how much dialysis is 'barely sufficient or satisfactory'? The term is frequently used in two ways (Table 1): 1) A dialysis prescription fulfilling certain criteria, and 2) The condition of a patient achieved with a particular prescription. This outcome constitutes a criterion of dialysis adequacy. During the early years of chronic hemodialysis, a definition of adequate dialysis was based on clinical grounds, particularly on the absence of symptoms and signs of uremia (1). In the early 1970s the definitions were based on a mixture of clinical symptoms and laboratory data (2,3). These definitions used a priori criteria of adequacy and were supposed to predict long term results of dialysis. The National Institutes of Health (NIH) sponsored National Cooperative Dialysis Study (NCDS) used the overall morbidity and mortality as decisive objective criteria for the relative values of different dialysis prescriptions (4). This approach used an a posteriori (from the actual results) criterion of dialysis adequacy. It was found that more dialysis decreased morbidity but no attempt was made to establish the optimal prescription.
Adequate peritoneal dialysis The adequacy of peritoneal dialysis prescriptions has never been tested in well controlled prospective studies. The adequacy of peritoneal dialysis is judged mainly by a priori clinical and laboratory criteria (Tables nand lll). The adequately dialyzed patient 'feels well and looks good', maintains hematocrit above 25% (without anabolic steroids or erythropoietin), has stable or increasing nerve conduction velocity (if not diabetic), and exhibits well controlled blood pressure. Manifestations of inadequate dialysis are usually subtle and often develop insidiously. Most commonly, inadequate dialysis results in such symptoms as insomnia, and
u Clinical criteria of dialysis adequacy
m Laboratory criteria of dialysis adequacy
1. Normal electrolytes 2. Serum creatinine:
