Quantification of renal haemodynamics with radionuclides.
ABSTRACT Non-invasive quantification of renal function with radionuclides is an important role of nuclear medicine. With modern commercial preparations of technetium-99m diethylene triamine penta-acetic acid (DTPA), glomerular filtration rate (GFR) can be measured accurately either from the rate of disappearance of the tracer from plasma or from its rate of uptake into the kidneys. Determination of the latter with the gamma camera allows measurement of individual kidney GFR. Renal blood flow (RBF) can be measured from plasma clearance of hippurate or from first-pass kinetics of intravenously injected tracer using the gamma camera. The filtration fraction can be obtained from separate measurement of GFR and RBF, either globally from plasma clearance studies or of each kidney from gamma camera studies. Because they are central to the understanding of plasma clearance studies, the effective distribution volumes of the various tracers used for renal function studies are also discussed in detail.
- European journal of nuclear medicine and molecular imaging 01/1995; 22(6):587-588. · 5.11 Impact Factor
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ABSTRACT: Hospital acquired renal dysfunction, most commonly caused by renal hypoperfusion, dramatically increases mortality in intensive care patients. Glomerular filtration rate (GFR) is rapidly altered during renal hypoperfusion, and a more rapid means of GFR measurement may prompt institution of renal-specific therapy. We hypothesized that a transcutaneous renal function monitor can rapidly and accurately assess acute changes in GFR within a time frame much shorter than the 2-4 hours currently available. The study design was a prospective determination of the capability to measure GFR transcutaneously. In three different studies, concurrent transcutaneous measurement of GFR, using the rate of disappearance of 99mTc-diethylenetriaminepentaacetic acid (DTPA), was compared by correlation and standard deviation (SD) to reference standards of DTPA plasma clearance, serum inulin clearance, or serum creatinine. Continuous transcutaneous clearance (TC) measurement correlated with standard DTPA plasma clearance techniques (r = 0.93). Acute pharmacologically induced changes in GFR are detectable by TC measurement within 12-20 min, a time interval significantly affected by the data acquisition interval. Excess patient movement in the ICU patients created clearance artifacts in 50% of clearance traces. Retrospective analysis of ICU patient data reveal TC measurements are 93% specific and 92% sensitive for serum creatinine levels in critically ill patients. TC monitoring provides prompt indication of directional changes in GFR and may provide the clinician warning of inadequate resuscitation. Prospective analysis of the specificity, sensitivity, and TC guided renal-specific resuscitation is needed.Journal of Clinical Monitoring and Computing 06/1998; 14(4):275-82. · 0.71 Impact Factor
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ABSTRACT: This study investigated whether the acute natriuretic effect of nitrendipine is related to its initial renal hemodynamic effects. We investigated 16 patients (10 men and 6 women, mean age 52 +/- 2 years) with essential hypertension, whose treatment, if any, was stopped 3 weeks before the study. They were admitted to a metabolic ward for 9 days and kept on a constant sodium diet of 55 mmol/day. During two 24-hour experiments, subjects randomly received a single oral dose of placebo/nitrendipine 10 mg (group 1, n = 8) or placebo/nitrendipine 20 mg (group 2, n = 8), according to a double-blind crossover study design. Patients fasted during the experiments, but their sodium intake was ensured by a constant intravenous saline infusion of 2.3 mmol/hr. Mean arterial pressure (MAP) and heart rate were determined for 5 hours following the administration of nitrendipine or placebo. Effective renal plasma flow (ERPF), glomerular filtration rate, active plasma renin concentration, angiotensin II, aldosterone, atrial natriuretic peptide, and catecholamines were determined every hour for 5 hours. Hourly urine collections were used to assess sodium, potassium, and creatinine excretions. Relative to placebo, only in group 2 (nitrendipine 20 mg) was a fall in MAP and a rise in ERPF observed 2 hours after the start of the experiment. The effects, however, lasted only for 1 hour. No such changes were seen in group 1. In neither group did nitrendipine affect hormonal concentrations. Sodium excretion was enhanced after the 20-mg dose of nitrendipine only (p < 0.05). Nitrendipine 20 mg induced a significant increase in sodium excretion, which may be dissociated from its acute hemodynamic effects.Cardiovascular Drugs and Therapy 03/1997; 11(1):33-8. · 2.67 Impact Factor