Lecture 6- renal function and lipids

serum creatinine

• waste product of creatine and phosphocreatine metabolism (occurs in muscle tissue)

• proportional to muscle mass and excreted daily by kidneys

BUN

• blood urea nitrogen

• product of digestion ad protein metabolism, which takes place in liver; excreted by kidneys

• impacted by protein intake, hydration, and liver function

eGFR

• estimated glomerular filtration rate

• estimate of kidney filtration capacity

• inversely proportional to creatinine

SCr and BUN

• filtration markers eliminated primarily b ykidenys

• inverse relation to eGFR

eGFR

• overall index of kidney function

serum creatinine

• eGFR is calculated using serum creatinine

• inverse to eGFR (increase creatinine usually means decrease eGFR)

BUN relationship

• BUN rises when kidney function decreases

• eGFR is NOT directly calculated from BUN, but BUN often changes in parallel with creatinine

importance?

does adjustments

BUN:Cr in AKI- pre-renal

decreased blood flow to kidneys

• CHF

• chock

• dehydration

• vomiting, diarrhea with dehydration

• HIGH BUN:Cr >20:1

• LOW urine Na+, <20mmol/L

• fluid status

BUN:Cr in AKI- renal

intrinsic kidney damage

• glomerulonephritis

• lyelonephritis

• interstitial nephritis

• rhabdomyolysis

• DM

• nephrotoxic drugs

• malnutrition

• acute tubular necrosis

• normal or low BUN:Cr 10:1

• HIGH urine Na+, >40mmol/L

BUN:Cr in AKI- post-renal

obstruction preventing mictrurition

• prostate

• nephrolithiasis

• bladder outlet obstruction

• neurogenic bladder

• tumor

• variable BUN:Cr

acute kidney injury (AKI)

abrupt decrease in renal function

• retention of urea

• dysregulation of extracellular volume and electrolytes

• multiple etiologies can cause

• increase in SCr by >0.3mg/dL within 48 hrs or >50% in 7days

• decrease in urine output <0.5mL/kg/hr for >6hrs

effect of serum Cr with increased muscle mass

• increase

• more Cr produced from muscle metabolism

effect of serum Cr with intense exercise

• increased (transient)

• muscle breakdown temporarily raises Cr

effect of serum Cr with high protein or cooked meat intake

• increase (slightly and only short period of time)

• creatinine like substances absorbed from diet

effect of serum Cr with dehydration

• increase

• volume depletion

effect of serum Cr pregnancy

• decrease

• increased GFR due to increase volume (more blood filtered) clears more rapidly

effect of serum Cr with liver disease

• decrease

• liver makes Cr→ if impaired, Cr prod may drop

effect of serum Cr with low muscle mass (elderly. malnutririon)

• decrease

• less Cr production

disease processes that increase SCr

• AKI: sudden drop in GFR (dehydration, obstruction, rhabdo)

• CKD: long term decline in GFR and filtration

• urinary tract obstruction: back pressure reduces filtration (enlarged prostate, kidney stines)

• diabetic nephropathy: reduced blood flow to kidneys impairs function

• nephrotoxic drugs (NSAIDs, aminoglycosides): direct kidney damage lower filtration

• glomerulonephritis: inflammation of glomeruli reduces filtration capacity

conditions causing false increased SCr (no GFR change)

• medications: inhibit tubular secretion

• diuresis: hemoconcentration

indications to measure SCr- chronic

• CKD

• DM

• HTN

• CVD assessment

• any autoimmune disease that affects kidneys (lupus, sarcoidosis)

• pre-op

• ANY chronic cond that requires use of chronic medication

indications to measure SCr- acute

general:

• diagnosis of AKI

• monitor critically ill pt

• before and after neo=phrotoxic medications

• pre/post contrast admin

• drug dosing adjustments

urinary sx:

• increase or decrease frequency of micturition, urgencym octuria, incontinence

• weak stream, staining to void

• flank pain with gross hematuria

• microscopic hematuria and/or proteinuria

use of lipid profile

determine risk of ASCVD (athlersclerotic cardiovascular disease)

components of lipid panel

• total cholesterol

• triglycerides - fat molecules in blood

• HDL cholesterol- good cholesterol. protective

• VLDL

• LDL cholesterol- bad. primary atherogenic lipoprotein

low density lipoprotein (LDL)

• carries cholesterol FROM lover to cells that need it (“Let’s go party in tissues”)

• can accumulat ein arterial walls

• determines coronary heart disease (CHD) risk

• high triglycerides→ inaccurate LDL calculation

high density lipoprotein (HDL)

• carries excess cholesterol to the LIVER (“lets go Home)

• more protective and reduces CHD risk at higher levels

• >60 is negative risk factor for CHD

• <40 is positive risk factor for CHD

  • smoking and etoh decrease HDLs

total cholesterol

HDL + LDL + 20% triglycerides

triglycerides

• critical value: >400mg/dL

• levels >500 increase risk of pancreatitis

• high TG can mask LDL levels

• transported mostly by VLDLs

• storage source of energy

• fatty meal ingestion, high starch consumption, etoh, and pregnancy→ can elevate TG levels

  • have pts FAST for mot accurate results

non-HDL

• all atherogenic lipoproteins (LDL, VLDL…)

• total cholesterol - HDL= non-HDL

• better predictor than LDL alone for ASCVD

• useful with elevated TG

increased risk ASCVD

• increased LDL (primary target)

• increased non-HDL (secondary target)

• increased TG

• increased lipoprotein

protective (decrease risk) ASCVD

• increased HDL

tx goals- ASCVD

• lower atherogenic lipoproteins

• LDL remains primary target