Edema and Heart Failure

Question 1

what is primary edema? what is secondary edema?

Answer 1

primary edema (also called overfill, overflow or nephritic) has to do with renal failure - usually acute glomerulonephritis
secondary edema is when the EABV is not properly reflecting the ECF due to a "Starling" block somewhere in the subcompartments

Question 2

what causes secondary edema?

Answer 2

all of the salt/water conservation mechanisms (catecholamines, RAA, ADH, sympathetic stimulation) are turned on, but the body is retaining large amounts of fluid

Question 3

name some conditions that cause secondary edema

Answer 3

CHF, burns, cirrhosis

Question 4

what natural condition might cause a slack circulation?

Answer 4

pregnancy

Question 5

where is the Starling block in burns?

Answer 5

between ECF and blood volumes (ECF traps fluid in tissue, vesicles and bullae)

Question 6

where is the Starling block in CHF?

Answer 6

in between blood volume and arterial volume; when the LV can’t put out enough blood into the arteries, it gets trapped in the venous return

Question 7

where is the Starling block in liver failure?

Answer 7

in between arterial volume and EABV; this is brought on by AV fistulas (shunts) in the microcirculation that return blood to the venous side, by portal hypertension that causes the release of NO into the endothelium of the vasculature causing dilation

Question 8

how do diuretics (esp. thiazides and loop) bring about hypokalemia?

Answer 8

they increase Na delivery to the distal nephron (CT) where increased Na uptake fuels increased K secretion

Question 9

what causes diuretics to induce metabolic alkalosis?

Answer 9

again, increased Na delivery to the distal nephron (CT) causes electronegativity in the CT, which brings about proton secretion from alpha intercalated cells; K secretion also helps the process as there are H/K ATP-ases in the CT

at the same time, the diuretics cause increased proximal reabsorption secondary to ECF contraction, which increases reabsorption of bicarb.

Question 10

what causes hyponatremia in CHF?

Answer 10

increased water retention, due to decreased delivery of solute into the distal tubule, which mean less free water formation; and all that water is reabsorbed in the CT anyways

these effects are secondary to the high levels of circulating RAA/ADH/sympathetic/catecholamines

thirst also contributes (due to high ADH/AII)