Biomedical subjects

M Andreucci

Publications and source records attributed to M Andreucci.

21 records · Page 2Linked to original sources

PubMed1996

Some sodium, potassium and water changes in the elderly and their treatment.

Creatinine clearance decreases with age by 1 ml/min/year after 40 years of age, although serum creatinine remains constant because of reduction of muscle mass. Reduction of water intake may occur in the elderly because of a reduced sensation of thirst; this is associated with a tendency to lose water with urine. The capacity to respond to sodium load is impaired in aged kidneys, thereby leading to ECV expansion and hypertension. But there is also, in the elderly, a reduced capacity for retaining sodium (FENa is higher than in young subjects), making old subjects sensitive to salt depletion and ECV contraction. Hypernatraemia (Nas > 150 mmol/l) is not infrequent in the elderly (1%) and is usually due to water deficiency (old subjects should be forced to drink), and rarely to iatrogenic excess of sodium. It is the abrupt occurrence of severe hypernatraemia that causes neurological symptoms due to dehydration and brain shrinking, which may lead to cerebral haemorrhage and death. Hyponatraemia (Nas < 130 mmol/l) is frequent among the elderly (7-11%) and is mainly due to water overload, which is usually iatrogenic. Hypovolaemic hyponatraemia occurs when salt depletion causes ECV contraction > 10%, and is due to water retention in an attempt to normalize ECV. Hypervolaemic hyponatraemia is due to ADH hypersecretion because of a decrease in 'effective' circulating blood volume. 'Pseudohyponatraemia' may occur because of hyperlipidaemia or hyperproteinaemia. It is the abrupt occurrence of severe hyponatraemia that causes neurological symptoms (water intoxication), secondary to the oedomatous swelling of the brain within the skull. While rapidly occurring hyponatraemia may be lethal, slowly occurring hyponatraemia is usually asymptomatic. Rapid correction of hyponatraemia may cause cerebral dehydration and 'osmotic demyelination syndrome' ('central pontine myelinosis'). Decrease (e.g. by diuretics) or increase (e.g. by ACE-inhibitors, non-steroidal anti-inflammatory drugs, beta-blockers) or serum potassium may occur in the elderly. Diuretics should be used with caution in elderly subjects to avoid salt depletion, hypotension and renal function impairment.

Aging↗

PubMedDate not supplied

Diuretics in renal failure.

Fluid retention following reduction in the glomerular filtration rate causes extracellular fluid volume expansion that reduces tubular reabsorption by residual nephrons, thereby maintaining the external sodium balance. The price paid for this is salt-dependent hypertension. Thus, loop diuretics are the best treatment for uremic hypertension. Diuretics are also used in chronic renal failure to treat edema due to nephrotic syndrome and congestive heart failure (CHF). In nephrotics, edema is often refractory to diuretics because of low plasma protein, depletion of the intravascular compartment, decrease in the protein-bound fraction of the diuretic in peritubular blood, and increase in tubular fluid. Thus, higher doses are needed. In uremics with CHF the efficacy of diuretics may be hampered because of the reduced renal blood flow. The association of dopamine (1-1.5 microg/kg body weight/min) may overcome this resistance; improvement in cardiac function by dialysis ultrafiltration may also help. Diuretic resistance is sometimes observed; it may be overcome by the following procedures: in CHF by the use of digitalis and/or angiotensin-converting enzyme inhibitors; by substitution of an ineffective loop diuretic for another one; by using larger doses of diuretic; by intravenous infusion rather than bolus therapy, and by a combination of diuretics acting in different segments of the tubule: loop diuretic+thiazide+amiloride. Intravenous infusion of 20% albumin has also been suggested.

Chronic Disease↗

PubMedDate not supplied

Early impairment of renal hemodynamic reserve in patients with asymptomatic heart failure is restored by angiotensin II antagonism.

BACKGROUND: The early/asymptomatic stages of heart failure (HF) are characterized by sodium retention secondary to derangement of sodium reabsorption at the proximal nephron level. Because this phenomenon is reversed by ACE inhibition, abnormalities of renal sodium handling may depend on intrarenal changes of angiotensin II (AII)/nitric oxide (NO) levels. Renal hemodynamic reserve (ie, the glomerular vasodilatory response to amino acid infusion) has been proposed as a reliable test to assess in vivo AII/NO balance. METHODS AND RESULTS: In this study, the effects of 6 weeks of treatment with 5 mg/d of enalapril or with 50 mg/d of losartan on systemic hemodynamics and renal function were assessed, at baseline and after amino acid infusion (AA), in patients with mild HF (NYHA class I) and in healthy volunteers. Untreated HF patients showed a basal renal function comparable to that of healthy subjects. After AA, glomerular filtration rate and renal plasma flow significantly increased in healthy subjects (+29.0% and +30.4%, respectively), whereas no vasodilatory response was observed in HF. Although they did not affect basal renal hemodynamics, both enalapril and losartan restored a normal response to AA in HF patients. Blood pressure and heart rate were comparable in HF subjects and healthy subjects at baseline and were not modified by either treatment. Left ventricular ejection fraction was depressed in HF but did not change after either drug. Urinary excretions of cGMP and nitrate (indexes of NO activity in the kidney), comparable in healthy subjects and in HF patients, were unchanged by either enalapril or losartan and did not correlate with renal reserve. CONCLUSIONS: (1) Renal functional reserve is absent in patients with early/asymptomatic HF and normal renal function and (2) both enalapril and losartan restore a normal vasodilatory response to AA in these patients without affecting basal systemic and renal hemodynamics. These data suggest a major role of AII in the development of early abnormalities in patients with HF.

Adult↗