Possible role of juxtaglomerular apparatus in low cardiac output syndrome and multiple organ failure: modulation by high sodium load.
Sympathetic overdrive in acute low cardiac output syndrome, diverts blood from cutaneous and visceral circulation centripetally. Microcirculation in general, and renal circulation in particular, deteriorates during these circulatory adjustments leading to multi-organ failure (MOF). Decreased afferent glomerular arteriolar blood flow, increased renal sympathetic nerve discharge and a resultant decreased sodium chloride delivery around macula densa stimulates the Juxta-glomerular apparatus (JGA) and triggers renin-angiotensin-aldosterone mechanism. This, along with increased ADH production results in a state of vasoconstriction, increased after-load, and continued fluid retention, further compromising the visceral microcirculation. Initially the fluid retention under the effect of aldosterone and ADH is iso-osmotic, but later under inappropriate ADH action more water than salt is retained, as evidenced by the presence of hyponatraemia and 'water-logging' in the endstage of this condition.The author hypothesizes that: although physiological, the persistent stimulation of the JGA during the low cardiac output state plays an important role in perpetuating a negative cardiovascular vicious cycle and further aggravating it into MOF. Furthermore, by infusing hypertonic saline and hence increasing the sodium chloride delivery to the distal tubules and the macula densa, the JGA could be inhibited. This strategy should work like angiotensin-converting-enzyme-inhibitor drugs in chronic cardiac failure, except by acting at the root cause and inhibiting Renin production at its source. It should further help by stimulating atrial natriuretic peptide secretion.
Mazhar
R
R
Cardiothoracic Surgery, Hamad Hospital, Doha, State of Qatar. rashmazhar@hotmail.com
D002303:Cardiac Output, Low / Q000503:physiopathology*; D006801:Humans; D007606:Juxtaglomerular Apparatus / Q000503:physiopathology*; D009102:Multiple Organ Failure / Q000503:physiopathology*; D012964:Sodium / Q000008:administration & dosage*
D012964:Sodium