Etiology:
Increased total body Na+
Primary d/o
Decreased effective circulating volume:
CHF
Cirrhosis
Profound hypoalbuminemia
Dx:
Expansion of interstitial compartment = edema, effusions
Expansion of intravascular compartment = lung crackles, JVD, HJR, S3 gallop, elevated BP.
Overt si of hypervolemia may not manifest until 2 - 4 L of fluid retention.
Gradual rise in wt. is the earliest indication of Na+ retention.
Sx: dyspnea, orthopnea, abdominal distension, swelling of extremities.
Labs: Hypervolemia is a clinical diagnosis
Urine Na <15 mEq/L with decreased effective circulating volume, reflecting renal Na+ retention.
Imaging: CXR may show pulmonary edema or pleural effusions, but clear lung fluids do not exclude volume overload.
Tx:
Tx underlying causes.
Correct ECF volume excess
diuretics enhance renal excretion of Na+ by blocking the various sites of Na+ reabsorption along the nephron.
THZ block NaCl transporters in the DCT.
Impair urine dilution capacity and often stimulate a responsive increase in the proximal tubule reabsorption.
Loop diuretics block Na-K-2Cl cotransporter in the ascending loop of Henle.
Brisk and immediate diuresis in acute vol overload.
Also enhance Ca++, and Mg++ excretion.
Impair urinary concentration, by increasing renal free water excretion.
K+ sparing diuretics act by decreasing Na reabsorption in the collecting duct.
Aldosterone antagonist do not require tubular secretion, and useful in low renal perfusion or impaired tubular function.
Limit Na+ intake.
Water restriction
if (Urine Na + Urine K)/Sr. Na, <0.5, restrict to 1 L/day
if (Urine Na + Urine K)/Sr. Na is 0.5 - 1, restrict to 500 mL/day
if (Urine Na + Urine K)/Sr. Na is >1, the Pt has negative renal free water clearance and is actively reabsorbing water.