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Biomedical subjects

A Valdivieso

Publications and source records attributed to A Valdivieso.

At least 19 recordsLinked to original sources
PubMed1998

The kidney in chronic liver disease: circulatory abnormalities, renal sodium handling and role of natriuretic peptides.

Patients with chronic liver disease (Läennec's cirrhosis) present sodium chloride retention, leading to fluid accumulation within the extracellular space (edema) and specially in the abdomen (ascites). This article reviews the pathogenesis of the hemodynamic abnormalities observed in these patients, particularly the hypothesis of "primary arterial vasodilation", with an increased nitric oxide production by endothelial cells playing a major role in the pathogenesis of vasodilation. Since excessive renal sodium reabsorption precedes ascites formation, two hypotheses are analyzed with respect to the handling of renal sodium in chronic liver disease: the underfilling and overflow theories. Furthermore, the role of natriuretic peptides is reviewed, the increment in atrial natriuretic peptide observed in well compensated cirrhotic patients being considered as a compensatory response to volume expansion, although with renal resistance to this peptide in early stages of the disease. This review ends with an integrated explanation of the circulatory disturbances, renal sodium retention and renal resistance to atrial natriuretic peptide resulting in the sodium and water abnormalities observed in chronic liver disease.

Animals↗
PubMed1996

Pharmacokinetics and pharmacodynamics of penbutolol in healthy and cancer subjects: role of altered protein binding.

The pharmacokinetic and pharmacodynamic profiles of penbutolol were examined in healthy volunteers and in cancer patients using a pharmacokinetic/pharmacodynamic (pk/pd) model. After receiving a 40 mg single oral dose of penbutolol, the absorption rate constant, apparent volume of distribution and serum clearance of penbutolol were found to be reduced in the cancer group. Changes in the disposition of the conjugate metabolite were also observed in the cancer patients. Penbutolol unbound fraction in serum was statistically decreased (p < 0.005) in the cancer group, according to the increase in the serum levels of alpha 1-acid glycoprotein seen in that group (p < 0.05). The pharmacodynamic effect of penbutolol was measured as the reduction in heart rate (HR); in healthy volunteers, a linear relationship (p < 0.01) between effect and penbutolol serum concentrations (total or unbound) was found. In contrast, in cancer patients, values of HR did not vary statistically in respect to baseline values. These results show that in cancer patients, a change in the pharmacokinetics of penbutolol occurs (associated with changes in drug protein binding), together with an alteration in the pharmacodynamics.

Adult↗
PubMed1996

[Distal renal tubular acidosis and nephrolithiasis in 3 cases of primary Sjögren syndrome].

Tubulo interstitial nephritis, the main manifestation of renal involvement in Sjögren syndrome, may lead to a tubular dysfunction that is usually subclinical. We report three women, aged 32, 35 and 35 years old, with a primary Sjögren syndrome and symptomatic type I or distal tubular acidosis. Two patients had nephrolithiasis and one a nephrocalcinosis. Two had a basal hyperchloremic metabolic acidosis. The ammonium chloride acidification test was abnormal in all, demonstrating a distal tubular defect. None had proximal tubular dysfunction. All had an urinary pH over 6.5 and hypocitraturia and none had hypercalciuria. Renal calculi were composed of calcium oxalate and calcium phosphate in two patients and calcium phosphate and ammonium phosphate in the other. All women had positive antinuclear antibodies with mottled pattern, two had anti Ro antibodies and positive rheumatoid factor and one had hypergammaglobulinemia. None had anti La antibodies, crioglobulinemia or monoclonal proteins.

Acidosis, Renal Tubular↗
PubMed1995

Influence of vitamin C on the absorption and first pass metabolism of propranolol.

The effect of ascorbic acid on the availability of propranolol has been examined. After oral administration of propranolol 80 mg with or without ascorbic acid pretreatment (2 g), the plasma concentrations and urinary excretion of propranolol and its metabolites, 4-hydroxy-propranolol and propranolol-conjugated, were determined by HPLC. Compared to controls, vitamin C decreased the maximum concentration of propranolol from 463 to 334 nmol.l-1, and the area under the propranolol concentration-time curve (from 0 to 24 hours) from 3.13 to 1.96 mumol.l-1.h. The time to reach maximum propranolol concentration was increased from 1.9 to 2.7. The total amount of drug recovered in urine has also significantly diminished (from 12.6 to 4.29 mg). No change in elimination rate was observed, indicating that ascorbic acid had affected both the absorption process and the first pass metabolism. The heart-rate decreased less when propranolol was administered with ascorbic acid in comparison to control subjects, although this interaction has little biological importance.

Administration, Oral↗
PubMed1995

Is it worth using mechanical sutures in gastric surgery?

The use of stapler devices in gastrointestinal surgery has to be justified by the results. Since the cost of staplers is very high, their use should be followed by some advantage in the operating time, the morbidity or mortality rate or the postoperative stay. We have found a slight shortening in the operating time, but only statistically significant for Billroth I, and in the postoperative stay only for oesophagojejunostomies mechanically performed. We have not found any advantage with the other techniques and in the other parameters. Consequently, the use of staplers in gastric surgery should be carefully assessed by the surgeon for each patient in particular, and only used in those cases where a real benefit will be presumed.

Adult↗
PubMed1993

Propranolol absorption in peptic ulcer disease.

This study was designed to determine whether gastroduodenal ulcer influences propranolol absorption. Eleven patients with peptic ulcer disease and eight healthy subjects received 80 mg of propranolol orally. Serum propranolol levels were measured with high-performance liquid chromatography. Ulcer patients showed a significant decrease in mean peak concentration of propranolol (90 +/- 12 ng/ml versus 151 +/- 23 ng/ml) (p < 0.025), in the absorption constant (1.43 +/- 0.21 h-1 versus 0.96 +/- 0.12 h-1) (p < 0.05), and in the area under concentration-time curve (802 +/- 129 ng/ml.h versus 492 +/- 73 ng/ml.h) (p < 0.05). No significant difference was seen in drug effect on the heart at 90 min. We conclude that propranolol is absorbed more slowly in ulcer patients than in healthy subjects, but this delay has no clinical effect after a single dose.

Adult↗
PubMed1993

Renal vascular and excretory resistance to atrial natriuretic peptide in pre-cirrhotic, bile-duct ligated rats.

Renal response to atrial natriuretic peptide in chronic cholestasis was studied in anaesthetized rats and in their isolated perfused kidneys. Cholestasis was induced by bile duct section after ligature, while controls were sham operated. Three weeks after surgery, cholestatic rats showed moderate arterial hypotension, elevated diuresis and no differences in urinary sodium, glomerular filtration rate (GFR) and fractional sodium excretion (FENa), when compared to controls. Isolated kidneys of cholestatic rats had equal basal diuresis and less natriuresis than the controls. Cholestatic rats presented blunted natriuretic and diuretic responses to iv injections of atrial natriuretic peptide (ANP 0.5 microgram), associated with reduced increments in GFR and FENa, when compared with controls. Similarly, the diuretic-natriuretic response of isolated kidneys to ANP (3.5 x 10(-9) M) was greatly attenuated in this group. ANP did not increase perfusion pressure in cholestatic rats, as it did in controls. These results indicate that animals with chronic cholestasis present refractoriness to ANP, which might be mediated by a direct impairment at the renal vascular and tubular sites for ANP action.

Analysis of Variance↗
PubMed1992

Renal function and cardiopulmonary bypass: effect of perfusion pressure.

Controversy continues as to whether hypotension during cardiopulmonary bypass (CPB) impairs intraoperative and postoperative renal function. Therefore, 21 patients with normal renal function (plasma creatinine less than 1.2 mg/dL, creatinine clearance greater than 70 mL/min), aged 50 to 70 years, without associated pathology, scheduled for elective coronary surgery were studied prospectively. Patients were randomized into two groups: group 1 included 14 patients whose arterial blood pressure during CPB was left untreated, and group 2 consisted of 7 patients who received phenylephrine to maintain their arterial pressure above 70 mmHg. Plasma and urine creatinine, sodium, potassium, and osmolality were measured preoperatively, intraoperatively and postoperatively. Creatinine, osmolal and free water clearances, and excreted sodium fraction were calculated. Plasma creatinine remained normal throughout the study in all patients. Creatinine clearances were similar preoperatively (101.9 +/- 36.7 in group 1 and 120.6 +/- 50.7 mL/min in group 2). In group 1, creatinine clearance decreased during CPB to 88.7 +/- 39.7 mL/min, whereas in group 2 it increased to 157.6 +/- 79.5 mL/min; the difference between groups was significant. Early postoperatively, there was no difference: 136.2 +/- 86.6 mL/min in group 1 and 100 +/- 21.4 mL/min in group 2. One week postoperatively, values were 100.5 +/- 37.9 and 101.9 +/- 18.4, respectively. There was a significant correlation between the creatinine clearance and perfusion pressure intraoperatively, but not postoperatively. Osmolal clearance also correlated with perfusion pressure intraoperatively, but it was significantly lower in the phenylephrine group postoperatively. Postoperative renal function was normal in all patients; no deleterious effect of a low arterial pressure during bypass could be identified.

Aged↗
PubMed1992

[Hypomagnesemia associated with hypokalemia, hyponatremia and metabolic alkalosis. Possible complication of gentamycin therapy].

Hypomagnesemia is a serious abnormality with different causes and usually associated to other disorders of electrolyte metabolism. We report a female patient developing hypomagnesemia after administration of gentamycin. This was associated to severe hypokalemia, hyponatremia and metabolic alkalosis. Possible pathogenetic mechanisms and therapeutic measures are discussed.

Aged↗
PubMed1992

[Effect of octopamine on arterial pressure and renal function in the normal rat].

Octopamine is a beta hydroxylated phenylethanolamine which accumulates in patients with chronic liver damage. A pathogenic role of octopamine in hemodynamic and systemic alterations of advanced liver failure was investigated in normal awake rats. An infusion of octopamine (220 ug/kg/min) was associated with an increase in mean arterial pressure, urinary volume, urinary Na and K output and their filtration fractions. Glomerular filtration rate and renal plasma flow were not affected. A sudden and marked decrease in mean blood pressure and diuresis was observed after stopping octopamine infusion. Findings during the infusion differ from those observed in the hepatorenal syndrome, although the post infusion period was characterized by hypotension and oliguria. Octopamine behaves as a vasoconstrictor and may interfere with the action of physiologic neurotransmitters.

Animals↗
PubMed1990

[Osteomalacia and renal tubular acidosis associated with analgesic abuse. A clinical case].

Osteomalacia is a multifactorial bone disorder. Main causes are vitamin D deficiency and phosphorus depletion. Among patients with renal insufficiency the incidence of osteomalacia is variable and probable related to impairment of the synthesis of 1,25 dihydroxy-vitamin D3 (calcitriol). We report a patients with severe osteomalacia, hyperkalemic tubular acidosis, low serum calcitriol levels and insufficiency associated to a prolonged overuse of analgesic drugs. Differential diagnosis and pathophysiology are discussed.

Acidosis, Renal Tubular↗
PubMed1989

[Hepatorenal syndrome].

The clinical and laboratory features of this syndrome are reviewed, with special emphasis upon different mechanisms that may be involved in its pathogenesis.

Hepatorenal Syndrome↗
PubMed1989

[Pseudohyponatremia and anion gap changes in multiple myeloma].

Pseudo-hyponatremia is a rare condition characterized by a decrease in plasma sodium concentration associated with a normal or increased effective plasma osmolarity. We present the case of a 62 year old woman with multiple myeloma (IgG) who had a plasma sodium of 84.5 mEq/l (as measured with flame photometry) and an anion gap of -8.8 mEq/l. However, when determined with an ion-selective electrode, plasma sodium was 135 mEq/l. The patient was treated with chemotherapy and did not receive sodium. One week later, plasma sodium--again measured by flame photometry--was 134 mEq/l and the anion gap 4.0 mEq/l. The pathophysiological and clinical aspects of pseudo-hyponatremia and the anion gap are discussed.

Acid-Base Equilibrium↗