Vaptans and hyponatremia in critical patients

Hyponatremia is the most frequent fluid and electrolyte disorder in hospitalized patients (20%), particularly in ICU, associated with an increase in morbility and mortality. While hypovolaemic hyponatremia needs to be corrected with the replacement of the lost extracellular fluid by isotonic saline, euvolaemic (SIADH) and hypervolaemic hyponatremia (oedematous states like decompensated heart failure, liver cirrhosis, i.e.) are treated by restriction of fluid intake, loop diuretics and hypertonic saline. A novel approach consists in use of vaptans, non-peptide arginine vasopressin (AVP) receptor antagonists. Vaptans cause “aquaresis”, which results in the correction of plasma osmolality and serum sodium levels, without activation of the renin-angiotensin-aldosterone system or changes in blood pressure and renal function. In this paper we critically reviewed the results of the available randomized controlled critical trials, discussing the effectiveness and safety of vaptans in treating hypervolaemic and euvolaemic hyponatremia in critical patients

Dopamine use in intensive care: are we ready to turn it down?

Dopamine is still frequently used as a first line vasopressor agent in hypotensive patients, when physicians are afraid of noradrenaline and believe that dopamine, with its β and α, inotrope and vasopressor effects, may be helpful. Evidence exists that it does not offer protection from renal failure, even if at low doses (0, 3-5 mcg/Kg/min) it may exert its effects on D1 and D2 receptors resulting in natriuresis and renal vasodilation, augmentation in renal blood flow, and diuresis. The effects of dopamine on gastrointestinal system and splanchnic perfusion in critical care patients are even more controversial, since they seem to be at least partially dependent on the initial fractional splanchnic blood flow. Dopamine may exert deleterious effects on respiratory function, by impairing the ventilatory drive response to hypoxemia and hypercapnia and reducing arterial oxygen saturation through a regional ventilation/perfusion mismatching. Dopamine seems to affect the cellular mediated mechanism of the immune function directly by its action on receptors located on immune system cells and indirectly altering the hormonal response regulating immune response. In this paper, the use of low dose dopamine is discussed in the intensive care perspective