Nephrology and dosing-final

Question 1

What are the excretory fxns of the kidney?

Answer 1

• making urine
• regulating electrolytes
• regulating osmolarity and water balance
• acid-base balance
• metabolite and waste elimination

Question 2

What are the endocrine actions of the kidney?

Answer 2

• Secretion of renin
• Production and secretion of eythropoietin
• Production and metabolism of prostaglandins and kinins

Question 3

What does RAAS do?

Answer 3

• Maintains intraglomerular pressure
• Maintains systemic blood pressure
• Regulates sodium excretion

Question 4

What are the metabolic fxns of the kidney?

Answer 4

• Activation of Vitamin D
• Gluconeogensis
• Metabolism
  * Insulin
  * Steroids
  * Xenobiotics

Question 5

True or false; the kidneys have an effect on blood pressure, RBC production, and bone health?

Answer 5

True

Question 6

What is the best overall index of kidney fxn?

Answer 6

GFR

Question 7

What is GRF?

Answer 7

The volume of plasma filtered across the glomerulus per unit time
Represents sum total filtration rates of all functional nephrons in both kidneys

Question 8

What is normal GFR in an adult?

Answer 8

> 90ml/min

Question 9

What is the criteria for an ideal marker for GFR estimation?

Answer 9

•Stable plasma concentration
•Freely filtered = freely diffuses across the glomerulus and into Bowman’s capsule
•Not reabsorbed, secreted, synthesized, or metabolized by the kidney
Does not alter renal function

Question 10

What is clearance?

Answer 10

volume of plasma “cleared” of a marker per unit time (mL/min)

Question 11

What is the GOLD STANDARD for measuring GFR?

Answer 11

Inulin clearance ….inulin is a substance that is a small, inert polysaccharide molecule that readily passes through the glomeruli into the urine without being reabsorbed by the renal tubules.

Question 12

Why is inulin gold standard?

Answer 12

•Distributed only in extracellular fluid
•Not bound to plasma proteins or tissues
•Easily passes through glomerular pores (freely filtered)
•Not secreted, reabsorbed, or metabolized in renal tubules
•No nonrenal elimination
HIGHLY ACCURATE

Question 13

Why is inulin clearance not used often?

Answer 13

•Procedure highly complicated
Requires continuous IV infusion
Collection of series of blood and urine samples
Need reliable assay to measure inulin in samples
•$$$$
•→ NOT convenient for clinical practice

Question 14

What is an accepted alternative to inulin clearance?

Answer 14

CrCl

Question 15

What is normal CrCL?

Answer 15

100-120 ml/min

Question 16

What is creatinine?

Answer 16

Product of creatine metabolism from muscle and dietary meat intake (endogenous molecule)

Question 17

What is production and release of creatinine related to?

Answer 17

• Production and release related to age, sex, & muscle mass

* Released at relatively constant rate

Question 18

Where is creatinine filtered?

Answer 18

Freely filtered at the glomerulus and not reabsorbed or metabolized by the kidneys

Question 19

What is the relationship of creatning to GFR?

Answer 19

Creatinine concentration increases proportionally to GFR decrease

Question 20

What are some limitations of using SrCr as GFR marker?

Answer 20

• Delayed SCr increase in early renal disease and acute renal failure
• Compounds can interfere with SCr secretion (cimetidine (OTC), trimethoprim)
• Compounds can interfere with SCr plasma assay (cephalosporins
• variability with fluid status, age, gender, muscle mass, and diet

Question 21

What is the Cockcroft gault equation used for?

Answer 21

• Estimate renal function in adults… used to dose adjust drugs
• Uses SCr to estimate CrCl (approximates GFR)
• Accounts for ↑SCr with ↑weight, and ↓SCr with ↑age

Question 22

What is the Cockcroft gault equation?

Answer 22

CrCl = (140-age)ABW / 72xSrCr X 0.85 if female

Question 23

What body weight should be used for obese pts?

Answer 23

Ideal body weight if actual is >30% above ideal

Question 24

What wt should be used in underwt patients?

Answer 24

If actual body wt is

Question 25

What are limitations of 24hr CrCl?

Answer 25

•Inconvenient •↓ accuracy with incorrect sample collection and storage Shorter collection times tend to be less accurate

Question 26

What is the normal range for BUN?

Answer 26

10-20 mg/dl

Question 27

Why is BUN less useful than SCR?

Answer 27

BUN changes independently of GFR

Question 28

What factors affect BUN but NOT renal fxn?

Answer 28

* Dehydration/hypovolemia (↑) * Hypervolemia (↓) * High protein diet (↑) * Catabolism (↓) * Febrile illness * Steroids * Liver disease (↓) * Decreased cardiac output (↑)

Question 29

What are causes of red-brown urine?

Answer 29

* Hematuria, myoglobinuria, hemoglobinuria * Drugs: nitrofurantoin, metronidazole * Food: beets, rhubarb

Question 30

What are causes of orange urine?

Answer 30

* Drugs: phenazopyridine, rifampin | * Food: Carrots

Question 31

What are causes of blue green urine?

Answer 31

Drugs: methylene blue, propofol, amitriptyline

Question 32

If RBC are found in microscopic UA, what could it indicate?

Answer 32

Glomerular damage, kidney trauma, UTI

Question 33

If WBC are found in microscopic UA, what could it indicate?

Answer 33

* UTI, pyelonephritis | * Acute interstitial nephritis (eosinophiluria)

Question 34

If renal tubular or epithelial cells are found in microscopic UA, what could they indicate?

Answer 34

Tubular damage

Question 35

If squamous cells are found in microscopic UA, what could they indicate?

Answer 35

Lower genital tract | skin contamination

Question 36

If casts are found in microscopic UA, what could they indicate?

Answer 36

•cylindrical bodies composed of proteins and/or cells •Indicates various types renal injury Types: hyaline, RBC, WBC, granular, waxy

Question 37

If crystals are found in microscopic UA, what could they indicate?

Answer 37

* Oxalate, phosphate | * Drugs: indinavir, acyclovir

Question 38

What are some reasons the pH of urine would be >8?

Answer 38

Aged urine, systemic alkalosis, UTI

Question 39

What are some reasons the pH of urine would be

Answer 39

Metabolic acidosis | Large amount of dietary meat intake

Question 40

What does specific gravity measure?

Answer 40

Urine concentrating ability of the kidneys

Question 41

What is protein in the urine?

Answer 41

Marker of kidney damage

Question 42

Why might there be glucose in the kidneys?

Answer 42

Uncontrolled DM

Question 43

What do ketones in the urine indicate?

Answer 43

Diabetic ketoacidosis | Fasting or starvation

Question 44

What are the pharmacokinetic changes in CKD?

Answer 44

Absorption Distribution Metabolism Elimination

Question 45

What are changes in distribution related too?

Answer 45

Protein and tissue binding alterations | Vd changes

Question 46

What is elimination dependent on?

Answer 46

Amount of drug normally excreted unchanged in urine | Degree of renal impairment

Question 47

What drugs have accumulation d/t there renally excreted metabolites? What are there toxic or therapeutic effects?

Answer 47

``` Morphine → morphine-6-glucuronide Prolonged analgesia, sedation, respiratory depression Meperidine → normeperidine Seizures Propoxyphene → norpropoxyphene Cardiotoxicity Sulfadiazine → acetylsulfadiazine Crystaluria, nephrolithiasis ```

Question 48

What is likely to develop in a pt with renal impairment if they receive lorazepam IV?

Answer 48

Propylene glycol toxicity | lactic acidosis, hyperosmolality, hypotension during administration of higher than recommended doses

Question 49

What is Cockcroft-Gault equation used for?

Answer 49

To estimate CrCl

Question 50

When is the MDRD equation used?

Answer 50

To estimate GFR- used to ID and stage chronic kidney dz

Question 51

What are advantages of reducing each dose while maintaining normal dosing intervals?

Answer 51

Provides sustained serum concentrations | Desirable for antibiotics with time dependent bactericidal activity

Question 52

What are disadvantages of reducing each dose while maintaining normal dosing intervals?

Answer 52

Lower peaks Higher troughs May require unusual dosages Associated with a higher risk of toxicities if the dosing interval is inadequate to allow for drug elimination

Question 53

What is an extended interval?

Answer 53

Normal doses are maintained, but the dosing interval is lengthened to allow time for drug elimination before re- dosing.

Question 54

What are advantages to extended interval dosing?

Answer 54

Similar peak and trough concentrations to those achieved in normal renal function Ideal for antibiotics with concentration dependent bactericidal activity Less pharmacy/nursing time

Question 55

What are disadvantages to extended interval dosing?

Answer 55

Interval may be “impractical” (every 90 hours) Associated with a lower risk of toxicities but a higher risk of subtherapeutic drug concentrations, especially toward the end of the dosing interval.

Question 56

What are exceptions to the general hemodialysis dosing rule? Why are they exceptions?

Answer 56

Erythropoetin Darbepoetin These drugs too large to fit through dialyzer