Hyperphosphatemia in Stage 5 CKD

Consequences And

Management

Bone and Mineral Metabolism in CKD ↓ Renal Function

Phosphate Retention ↓ 1,25 D Production

↑ PTH ↓ Ca+ Decreased VDR expression

Altered Parathyroid Gland Function ➙ Hyperplasia ➙ SHPT

CONSEQUENCES Renal Osteodystrophy Fractures Calcification CV Disease

MORBIDITY & MORTALITY

↑ PO4

Hyperphosphatemia

What are the different sources of vitamin D?

Precursor or pro-hormones found in: Skin - 7 dehydrocholesterol D3 Diet

- Animal Source: Cholecalciferol=D3 - Plant Source: Ergocalciferol = D2

Metabolic Pathways of Vitamin D 2 and D 3

7-dehydrocholesterol

Cholecalciferol (D3)

25-hydroxycholecalciferol

1,25-dihydroxyergocalciferol 1,25-dihydroxycholecalciferol

Dietary Sources

Liver

Kidney

(25-hydroxylase)

(1 -hydroxylase)

1,25(OH)2D2 1,25(OH)2D3

Ergosterol

Ergocalciferol (D2)

25-hydroxyergocalciferol

UV Light

What are the normal levels of vitamin D? How are they affected?

Average production of active vitamin D hormone by healthy kidneys = 1-2 mg/day

Average serum level of active vitamin D hormone = 20 -70 pg/ml (pg=1 trillionth of a gram)

Seasonal and developmental variation in serum levels

Age Lifestyle Geographical location

seasonal Race Culture

Severe Vitamin D Deficiency

Vitamin D Status1

1. National Kidney Foundation (NKF). K/DOQI clinical practice guidelines for bone metabolism and disease in chronic kidney disease. Am J Kidney Dis. 2003;42(4 Suppl 3):S1-S201.

5-15 ng/mL

30 ng/mL

Note: A patient’s vitamin D status is typically assessed by measuring serum 25(OH)D1

25(OH)D Insufficiency and Deficiency

X

Osteoclast

Ca2+

Bone

Blood Ca2+ (& PO4)

Kidney

Ca2+

PO4

D hormone

Parathyroid Gland

Intestine

1 -hydroxylase

1,25(OH)2D 25(OH)D

1 -hydroxylase

1,25(OH)2D 25(OH)D

Normal

CKD Decreasing Renal Mass

Elevated phosphorus and uremia suppress the activity of 1 -hydroxylase in the kidney

↑FGF 23

Vitamin D Deficiency in CKD

Balance between Protein Synthesis and Catabolism

A shift in balance between protein synthesis and breakdown toward catabolism can cause an increase in serum phosphorus1:

Infection Trauma Starvation

1NKF. K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in CKD.Am J Kidney Dis. 2003; 42(suppl 3)

Hidden Sources of Phosphorus

173 mg/12 oz

53 mg/12 oz

53-140 mg/12 oz 134 mg/12 oz 93 mg/12 oz

49 mg/12 oz

37 mg/12 oz

115 mg (from mix)

98-150 mg/biscuit

89 mg/10 inch Flour tortilla

66 mg/12 oz with lemon or raspberry

http://www.supereggplant.com/archives/biscuits.JPG

PhosLo GENERIC NAME(S): CALCIUM ACETATE

Renvela Sevelamer carbonate

Serum Calcium

Serum Calcium

Bound To Protein

40%

Complexed10%

Free (Ionized)50%

Friedman PA, Tenenhouse HS. Renal Handling of Calcium and Phosphorus. Disorders of Bone and Mineral Metabolism. Lippincott Williams and Wilkins. Philadelphia, PA, 2nd Edition, 2002

Corrected Calcium Serum Calcium should be “corrected” or “adjusted” in the presence of hypoalbuminemia A formula often used for correcting/adjusting calcium is: a) 4.0 minus patient’s serum albumin = X b) X times 0.8 = Y c) Patient’s serum calcium plus Y = corrected serum

calcium

National Kidney Foundation. K/DOQI clinical practice guidelines for bone metabolism and disease in chronic kidney disease. Am J

Kidney Dis 2003; 42 Suppl 3: 80.

Positive calcium balance may not be reflected in serum calcium

Homeostatic control works to maintain normal serum calcium

KT/V AND BUN

• KT/V tells us whether a patient is receiving adequate dialysis.

• Normal is 1.2 or greater.

• BUN (blood urea nitrogen) 60-80 is normal in dialysis patients. We seldom look at this because the kt/v is what is important..

• Patients rarely receive too much protein

Be in the Cool Crowd: Meet your Goals!

Your Lab Goals: Albumin: 3.5 or higher Hemoglobin: 10-12 Calcium: 8.4-10.2 Phosphorus: 3.0-5.5 PTH 150-600 Potassium: 3.5-5.5 Kt/V: 1.2 or higher Weight Gain Between Treatments: 3 kg or less Copyright DaVita, Inc. 2011