Biomedical subjects

R D Monk

Publications and source records attributed to R D Monk.

5 recordsLinked to original sources

PubMed2006

Tacrolimus-associated hypomagnesemia in renal transplant recipients.

BACKGROUND: Since hypomagnesemia occurs frequently in tacrolimus treated patients, we studied the correlation between renal magnesium wasting and tacrolimus blood levels in renal transplant patients. METHODS: Serum magnesium, fractional excretion of magnesium (FEMg), and 24-hour urinary excretion of magnesium were measured in 41 transplant patients and 10 healthy volunteers for correlation with tacrolimus level. RESULTS: Of tacrolimus-treated patients, 43% displayed hypomagnesemia. FEMg (7.42+/-3.59% versus 1.88+/-0.43%) and 24-hour urinary excretion (112.36+/-51.43 mg/dL versus 6.7+/-2.79 mg/dL) were significantly higher among tacrolimus-treated patients than controls. Magnesium replacement did not influence FEMg or 24-hour urinary magnesium excretion. Tacrolimus level was the best predictor of 24-hour urinary magnesium excretion and FEMg. Serum magnesium levels correlated inversely with tacrolimus concentrations and creatinine clearance. CONCLUSION: Hypomagnesemia in renal transplant recipients results from renal magnesium wasting. Tacrolimus levels and renal function impact on the excess renal magnesium excretion. Studies of longer duration are warranted to assess the long-term effects of this early posttransplant hypomagnesemia.

Adult↗

PubMed1998

Electrolyte quintet: Calcium.

Abnormalities in serum calcium concentration may have profound effects on neurological, gastrointestinal, and renal function. Maintenance of the normal serum calcium is a result of tightly regulated ion transport by the kidney, intestinal tract, and bone, mediated by calcaemic hormones especially parathyroid hormone and 1,25-dihydroxyvitamin D3. Abnormalities in calcium transport that result in uncompensated influx into, or efflux from, the extracellular fluid, will result in hypercalcaemia or hypocalcaemia, respectively. When possible the biologically important ionised calcium concentration should be measured. A variety of common disorders are responsible for abnormalities in the serum calcium. Treatment of both hypercalcaemia and hypocalcaemia is dependent on the underlying disorder, the magnitude of the deviation of the serum calcium, and the severity of symptoms. Fortunately, in the case of hypercalcaemia, there is a broad selection of effective medications, especially the bisphosphonates. Treatment of hypocalcaemia relies on the provision of calcium and often vitamin D. In this article we review the mechanisms responsible for abnormalities in calcium homoeostasis, the differential diagnosis of hypercalcaemia and hypocalcaemia, and appropriate therapy.

Calcium↗

PubMed1997

Renal sonography: can it be used more selectively in the setting of an elevated serum creatinine level?

The objectives of our study were to (1) assess the outcomes resulting from the use of sonography in patients referred to our institution's ultrasound laboratory for an elevated serum creatinine level and (2) determine relevant clinical parameters in these patients to better triage them for sonography. We retrospectively identified and determined outcomes of 60 patients (20 women, 40 men; mean age, 61 years; range, 33 to 100 years) referred for sonographic evaluation because of an increased serum creatinine level (> or = 1.3 mg/dL). Ultrasound findings (hydronephrosis, renal size, and echogenicity) were correlated with clinical outcomes. Twenty-one patients (35%) had hydronephrosis, with 14 of these patients confirmed to be obstructed and five not obstructed. Two were indeterminate for obstruction. Eight of 14 obstructed patients were successfully treated. All obstructed patients had a suggestive history for obstruction with at least one of the following: pelvic mass (n = 9), stone disease (n = 4), or flank pain (n = 1). Only 2 of 44 patients, who were not obstructed, had any of these parameters (statistically significant difference, P < 0.0001). Thirty of the patients, who were not obstructed, had more likely alternative causes for renal failure, with sonography having no effect on patient management. Renal size and echogenicity had little effect on patient management. Sonography was efficacious in guiding management in patients with a suggestive history for obstruction (eg, pelvic mass, stone disease, or flank pain) but not in most patients who had no suggestive history and other more likely causes for renal failure.

Adult↗

PubMed1996

Clinical approach to adults.

Acute episodes of renal colic are associated with severe pain and often necessitate invasive procedures and costly absences from work. A medical approach to evaluate all patients with kidney stones is generally recommended to detect underlying systemic disorders associated with nephrolithiasis and prevent further stone formation. patients with a single stone require a limited evaluation, whereas those with metabolically active stones, stones not composed of calcium oxalate, all children, and patients in demographic groups not commonly associated with nephrolithiasis should undergo a more extensive workup. The major classes of stones formed are calcium oxalate, calcium phosphate, uric acid, struvite, and cystine. This article focuses on etiologic factors that predispose to nephrolithiasis in general, as well as to specific stone types. A thorough review of the evaluation and therapy required for all stones is presented.

Adult↗

PubMed1994

Hormonal regulation of Na(+)-Ca2+ exchange in osteoblast-like cells.

We proposed a role for Na-Ca exchange in hormonally mediated bone resorption and recently characterized Na-dependent Ca transport in an osteoblast-like rat osteosarcoma cell line (UMR-106). To test whether calcemic agents alter Na(+)-Ca2+ exchange in osteoblasts, UMR cells were treated acutely or cultured in the absence or presence of calcemic agent for 24 h. Cells were then loaded with the Ca-sensitive dye fura-2 in the presence of 140 mM NaCl, no Ca, and the absence or presence of 0.3 mM ouabain. Cells were resuspended at 22 degrees C, and the fluorescence ratio at excitation wavelength of 340 and 380 nm was measured. An outward Na gradient was generated by removing extracellular Na and maintaining isotonicity with choline chloride. Na(+)-Ca2+ exchange was demonstrated by enhanced Ca uptake in ouabain-treated (Na-loaded) cells after the addition of 1.5 mM Ca. Acute addition of 10(-7) M PTH or 10(-6) M PGE2 had no effect on Na-dependent Ca uptake. However, 24 h treatment of cells with PTH, PGE2, or 1,25(OH)2D3 caused a dose-dependent inhibition of Na(+)-Ca2+ exchange. Using the Na-sensitive dye, SBFI, we also demonstrated that the effect was bidirectional; PTH inhibited Ca-dependent Na uptake comparably to its inhibition of Na-dependent Ca uptake. The effects of the calcemic agents were mimicked by 24 h treatment of the cells with 1 microM forskolin or 2 microM PMA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗