Post on 25-Jan-2021
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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