Nephrology Flashcards
____ is the most important aspect of kidney function with respect to adjustment of drug dosing, and it cannot be measured easily by direct measures.
GFR
Factors that affect creatinine
- Age 2. Body Mass 3. Sex 4. Diet high in protein, 5. Drugs affecting Creatinine secretion (i.e. cimetidine, trimethoprim, probenecid)
Cockcroft-Gault Equation
140-age(years) X IBW (kg)/ (72 X Scr (mg/dl)) X 0.85 for females
IBW Equation
Male: 50 Kg + 2.3 * (inches over 5 ft)
Female 45 + 2.3 (inches over 5 ft)
MDRD Facts
- Usually the basis for the eGFR seen in patient charts, 2. does not use a weight/based on BSA 3. underestimates eGFR for heavy people, overestimates for underweight people
CKD- EPI Formula
CKD Epidemiology Collaboration formula, this equation is more precise than the MDRD equation.
Jeliffe Equation
Use when height and weight in adults are unavailable
Salazar-Corcoran
Equation for obese individuals
Schwartz Equation
For use in children.
Stages of Kidney Disease based on GFR
Stage 1: Kidney damage with normal GFR >90 ml/imin
Stage 2: Kidney damage with mild reduction in GFR 60-89 ml/min
Stage 3: Moderate Dec in GFR, 30-59 ml/min
Stage 4: Severe Dec in GFR, 15-29 ml/min
Stage 5: Kidney Failure, < 15 ml/min or on dialysis
____ is the cause of 50% of CKD cases in the US
Diabetes
30-300 mg of creatinine per gram in urine
microalbuminuria
> 300 mg of creatinine per gram in the urine
macroalbuminuria
Macroalbuminuira Treatment for Normotensive Patient
Treat with an ACE-I or ARB
What is the most important reason to avoid use of an ACE-I in a patient with CKD and HTN?
Bilateral Renal Artery Stenosis (obviously angioedema with previous treatment as well)
_____ is the cause for CKD in 25-30% of patients.
HTN
HTN treatment in CKD without albuminuria, preferred treatment?
No preferred agent.
Which stages of CKD is it appropriate to use thiazides? Loops? Potassium-Sparing?
Thiazide: Stages 1-3
Loops: any, often used in stages 4-5
Potassium Sparing: Use caution in stages 4 & 5, especially if on ARB/ACE-I
Preferred Beta-blocker in Renal Dz
Metoprolol (reason is some b-blockers like atenolol have an extended half-life in renal dz.
Signs and Symptoms of Uremia
Nausea/Vomitting, Anorexia, taste changes, constipation, Dry skin, itching, Altered mental status (encephalopathy)
Nutritional Considerations for Patients with CKD (not on dialysis)
- Protein Restriction (often limited to 0.4- 0.8 g/kg/day however this can leaded to malnourishment once patient gets to dialysis.
- Sodium Restriction (no more than 3 g/day)
- Potassium Restriction to 2-4 g/day
- Phosphorus Restriction beginning at CKD stage 3, less than 800mg/dl.
Additional Nutritional Considerations for Patients with CKD on dialysis
- Magnesium
- Aluminum (both from antacids)
- Fluid
Goals of Anemia Management in CKD on ESA
Hemoglobin should not exceed 10 g/dl, dose should be decreased or interrupted if Hgb exceeds 11 g/dl.
Starting Dose for Epoetin Alfa
50-150 units/kg 3 times per week, w/o dialysis can typically be given 1 x per week at higher dose.
Starting Dose for Darbepoetin
0.45 mcg/kg, can be given as infrequently as every 4 weeks. In HD every 1-2 weeks.
Monitoring Parameters for ESA Use
- Monitor Hbg every 2 weeks until stable, then monthly
- Dose increases should not be made more often than once monthly and usually not in increments greater than 25%.
- Dose decreases should be made anytime Hgb rise exceeds 1 g/dl in any 2 week period or above desired value.
4.
Iron Therapy Targets
Ferritin: 200-500 ng/ml Transferrin saturation (TSAT) > 20%
(oral therapy is appropriate for stages 3 or 4), but patients undergoing HD must receive parenteral iron.
Hyperphosphatemia and Hypocalcemia occur in CKD because….
Due to the kidney’s inability to activate vitamin D, which reduces the amount of calcium that is absorbed from the gut as well as circulating calcium. Reduces phosphorus elimination
Low free calcium concentrations in CKD…lead to…
increased levels of PTH, which leads to bone demineralization.
KDOQI Therapy Goals for Calcium (mg/dl)
Stage 3 & 4: Normal
Stage 5: 8.4-9.5 mg/dl
KDOQI Therapy Goals for Phosphorus (mg/dl)
Stage 3 & 4: 2.7-4.6
Stage 5: 3.5-5.5
KDOQI Therapy Goals Calcium X Phosphate product
Always want < 55
KDOQI Therapy Goals for iPTH (pg/ml)
Stage 3: 35-70
Stage 4: 70-110
Stage 5: 150-300
Corrected Calcium Formula
serum calcium + 0.8 X (4- serum albumin)
Phosphate Biner Therapy- Calcium Products
- Must take with meals!
- Calcium Containing Agents:
Calcium Carbonate is inexpensive, chewable, OTC
Calcium acetate (PHOSLO) is more potent
Hypercalcemia can limit use of calcium-based products. Also recent data suggestions vascular calcification and extra-skeletal calcification concerns. Total dose of Calcium should not exceed 2000 mg/dl. (elemental 1500mg/dl)
Sevelamer
Brand Name: Renagel
Nonabsorbable dietary resin that binds phosphorus
Good option for hypercalcemic patients.
Some drug interactions:cyclosporin, mycophenolate, FQ’s, Thyroid Meds.
Lanthanum Carbonate
Brand Name: FosRenol
Also non absorbable dietary resin that binds phosphorus, Tasteless, chewable wafer, contraindicated in children.
Active Vitamin D Analogs- Calcitriol
Use to reduce PTH, orally and parenterally, oral agent appears to increase GI absorption more causing hypercalcemia/hyperpohsphatemia.
Active Vitamin D Analogs- Paricalcitol
use to reduce PTH
Oral & Parenteral
Lower incidence of hypercalcemia/hyperphosphatemia than with calcitriol
IV at the end of HD = 100% adherence
Active Vitamin D Analogs- Doxercalciferol
Reduces PTH, oral/parenteral/requires hepatic activation, lower incidence of hypercalcemia than with calcitriol
Active Vitamin D Analogs-Cinacalcet HCL
Brand Name: Sensipar
Lowers PTH
MOA: Calcimimetic agents that binds to the calcium receptor on the PT gland. increases calcium receptor sensitivity which reduces PTH secretion.
Only Oral
Expensive (reserved for patients with hypercalciema/ not responding to phosphate binders)
Caution seizure disorders
Must monitor Serum Ca and PO4 within 1 week of therapy, and after dose titration. PTH should be measured within 1-4 weeks of therapy.
Use in conjunction with vitamin D and phosphate binders, not mono therapy
Initial Dose: 30 mg/day with dose adjustment every 1-2 weeks.
Take with food or shortly after a meal.
Avoid in patients with serum calcium less than 8.4mg/dl.
Changes in Drug Absorption that can occur in CKD
- lower drug absorption due to drug interactions (antacids/iron with FQ)
- Lower secondary to uremia gastritis, uremia neuropathy, diabetic gastropathy
- Lower secondary to change in gastric ph (more alkaline)
- Lower secondary to decreased first pass metabolism by the liver.
Changes in Protein Binding in CKD/Drug Interactions
Decrease protein = decreased binding sites for chloramphenicol, pheyntoin, warfarin, diazepam, furosemide, valproic acid, pentobarbital, salicylate.
Drugs and Hormones that are partially metabolized by the Kidneys
Lower metabolism can occur in CKD.
Acetaminophen, calcitonin, cephalothin, growth hormone, imipenem, insulin, isoproterenol, meperidine, morphine, salicylate, sulindac.
Accumulation of Metabolites in CKD
Morphine, propoxyphene, procainamide, meperidine
Indications for Renal Replacement Therapy (A-E-I-O-U)
A- Acide base E- Electrolyte disorders I- Intoxications O- Fluid Overload U- Uremia (general rule if BUN >100 or Scr >10)
Drug Removal by Dialysis
- small molecular weight
- low protein binding
- small volume of distribution (found solely in the blood)
- Hydrophillic
The Most important characteristic of HD for drug removal is….
whether the hemodialyzer is a low or high flux dialyzer
Is there a difference in outcomes in HD vs. PD?
No patient outcomes are similar. However PD is not as efficient at removing drugs or solutes as HD per unit of time. PD typically is a dextrose solution, DM patients will need more insulin. There is a newer agent Icodextrin on the market that may be an answer.
Peritonitis Clinical Presentation & Treatment
Clinical Presentation: Cloudy dialysate, abdominal pain, abdominal tenderness, fever, nausea, elevated WBC
Treatment: Intraperitoneal antibiotics: catheter removal for selected organisms
First and third gen cephalosporins together (example cefazolin and ceftazidime)
Vancomycin and gent can be used less desirable.
Patients with residual renal function or automated PD will need higher antibiotic doses.
