CKD - Fluid and electrolyte disorders

Question 1

What are the most common electrolyte problems in CKD?

Answer 1

• Hyponatremia
• Hyperkalemia

Question 2

As long as ____, the ECFV expansion will be isotonic and the patient will have a normal plasma sodium concentration

Answer 2

Water intake does not exceed the capacity for renal water clearance

Question 3

Hyponatremia is not commonly seen in CKD patients but, when present, often responds to ____

Answer 3

Water restriction

Question 4

Diuretic use in CKD patients with ECFV expansion

Answer 4

• Thiazide diuretics have limited utility in stages 3–5 CKD, such that administration of loop diuretics, including furosemide, bumetanide, or torsemide, may also be needed
• Resistance to loop diuretics in CKD often mandates use of higher doses than those used in patients with higher GFR
• The combination of loop diuretics with metolazone may be helpful
• Note:*
• Diuretic resistance with intractable edema and hypertension in advanced CKD may serve as an indication to initiate dialysis

Question 5

Depletion of ECFV, whether due to GI losses or overzealous diuretic therapy, can further compromise kidney function through underperfusion, or a “prerenal” state, leading to acute-on-chronic kidney failure. In this setting, what can be done?

Answer 5

Holding or adjusting the diuretic dose or even cautious volume repletion with normal saline may return the ECFV to normal and restore renal function to baseline

Question 6

What are the body’s defense mechanisms againts hyperkalemia even in patients with CKD?

Answer 6

1. Decline in GFR is not necessarily accompanied by a parallel decline in urinary potassium excretion, which is predominantly mediated by aldosterone-dependent secretion in the distal nephron
2. Augmented potassium excretion in the GI tract

Question 7

Triggers of hyperkalemia in CKD patients

Answer 7

• Increased dietary potassium intake
• Hemolysis
• Hemorrhage
• Transfusion of stored red blood cells
• Metabolic acidosis
• Medications
  
  • RAS inhibitors and spironolactone and other potassium-sparing diuretics such as amiloride,
    eplerenone, and triamterene

Question 8

If RAS inhibitors can cause hyperkalemia, should they still be used in CKD patients?

Answer 8

The benefits of the RAS inhibitors in ameliorating the progression of CKD and its complications often favor their cautious and judicious use with very close monitoring of plasma potassium concentration

Question 9

Certain causes of CKD can be associated with earlier and more severe disruption of potassium-secretory mechanisms in the distal nephron, out of proportion to the decline in GFR. These include:

Answer 9

• Conditions associated with hyporeninemic hypoaldosteronism, such as diabetes
• Renal diseases that preferentially affect the distal nephron, such as obstructive uropathy and sickle cell nephropathy

Question 10

Hypokalemia is ____ (common/uncommon) in CKD and usually reflects ____

Answer 10

• Uncommon
• Markedly reduced dietary potassium intake, especially in association with excessive diuretic therapy or concurrent GI losses

Question 11

Management to maintain euvolemia

Answer 11

• Dietary salt restriction; and
• Use of loop diuretics, occasionally in combination with metolazone

Question 12

According to HPIM, what is the indication for water restriction?

Answer 12

Only if there is a problem with hyponatremia

Question 13

Management of hyperkalemia

Answer 13

• Dietary restriction of potassium
• Use of kaliuretic diuretics
• Avoidance of both potassium supplements (including occult sources, such as dietary salt substitutes)
• Dose reduction or avoidance of potassium-retaining medications (especially angiotensin-converting enzyme [ACE] inhibitors or angiotensin receptor blockers [ARBs])
• Use of potassium-binding resins, such as calcium resonium, sodium polystyrene or patiromer