NRSG 326 Week 2 - AKI

Functions of the kidney

Excretion of wastes, reabsorption or secretion of minerals and electrolytes, acid-base balance, hormone secretion

What 3 hormones do the kidneys play a role in secreting and what do they do?

Erythropoietin (regulate RBC production), renin (regulate BP), calcitriol (active form of vitamin D converted in kidneys)

Syndrome

A cluster or grouping of s/s that present themselves in a specific way

Not a disease, is a manifestation that something else is going on

Kidney Disease Improving Global Outcomes (KDIGO) definition of AKI

Increase in serum creatinine of > 26.52 micromols in 48h, increase in serum creatinine of > 1.5x baseline within 7 days, urine volume < 0.5 mL/kg/h for 6 hours

Azotemia

Accumulation of nitrogen waste products (BUN and creatinine) in blood

3 cardinal signs of kidney damage

Increased creatinine, decreased eGFR/GFR and decreased urine output

Risk factors for AKI

ETOH use, dehydration, trauma, infection, diabetes, cardiovascular disease, liver disease, obesity, genetics, age, socioeconomic status, racial discrimination

Normal urine output

0.5 mL/kg/hr

What is the most common manifestation of AKI?

Oliguria

Blood urea nitrogen (BUN)

Produced by digestion of ammonia in liver (ammonia comes from proteins)

Removed by kidneys, primarily by glomerular filtration and proximal tubular secretion

Indicator but not a direct measure of renal function

Creatinine

Breakdown product of creatinine phosphate from muscle and protein metabolism

Released at constant rate by body

Removed from blood by kidneys via glomerular filtration and proximal tubular secretion

Indicator, but not a direct measure of renal function

What can increase creatinine

Rhabdomyolysis, high protein diet, high intensity exercises

What can decrease creatinine

Poor nutritional status, pregnancy

Glomerular filtration rate (GFR)

Provides info on how well kidneys are working and can be used to estimate function

Can be directly measured by the clearance of exogenous filtration markers

Expensive + time consuming test!

Estimated GFR (eGFR)

Best estimate of pt's GFR

Not an actual GFR test

Uses creatinine as filtration marker

Takes creatinine, sex, age and sometimes race into a formula to calculate GFR

3 types of renal failure

Prerenal, intrarenal, post renal

Prerenal kidney failure

D/t factors external to kidneys resulting in decreased perfusion to the kidneys, which decreases GFR

Can be caused by decreased cardiac output, hypovolemia, sepsis, vasoactive medications and HF

Intrarenal kidney failure

D/t direct damage to renal tissue from ischemia, nephrotoxins, hemolyzed RBCs, myoglobin, lupus and acute glomerulonephritis

Most common intrarenal failure is acute tubular necrosis (ATN)

Postrenal kidney failure

D/t mechanical obstruction of urinary outflow

Can be due to BPH, prostate cancer, kidney stones (caliculi), trauma, tumors etc

Urine diagnostics in prerenal

Increased osmolality, decreased urine sodium, no protein present, no blood present, and no urine sediment present

Urine diagnostics in intrarenal

Decreased urine osmolality, increased urine sodium, protein is present, microscopic amounts of blood present, brown/muddy casts

Urine diagnostics in postrenal

Normal osmolality (can increase), normal urine sodium (can increase), protein not present, may have gross hematuria depending on cause, sediment possible if blood in urine

Common causes of acute tubular necrosis (ATN)

Ischemia, nephrotoxin accumulation, sepsis

Markers of initiation phase of ATN

Increased creatinine and BUN

Markers of maintenance phase of ATN

Increased creatinine and BUN, decreased eGFR and

Fluid overload, metabolic acidosis, increased electrolytes, neurochanges

Markers of recovery phase

Increasing eGFR, decreased BUN and creatinine

1-5L of UO per day

Can lead to hypovolemia, hypotension, hyponatremia, hypokalemia and dehydration

Tx of hyperkalemia

Calcium gluconate, insulin and glucose concurrently, kayexalate, calcium (cardioprotectic), salbutamol (inhaled beta agonists) hemodialysis

Short term monitoring for AKI

Renal profile (eGFR, Cr, BUN), electrolytes, CBC

Long term monitoring for AKI

Renal profile (eGFR, Cr, BUN) x 4 weeks

Types of dialysis

Hemodialysis, peritoneal dialysis, continuous renal replacement therapy (CRRT)

Indications for dialysis in AKI

Volume overload, hyperkalemia, acidosis, symptomatic uremia (pericarditis, encephalopathy, bleeding dyscrasias, NV, pruritus), uremia (BUN > 38 mmol/L), dialyzable intoxications/poisioning (ex: ASA, lithium, ethylene glycol)

Risks for survivors of AKI

Increased risk of death, rehospitalization, CKD and CVD

What kind of kidney injury would a 55 y/o with a GI bleed have?

Prerenal

What kind of kidney injury would a 25 y/o with an ASA OD have?

Intrarenal

What kind of kidney injury would a 40 y/o with prostate cancer have?

Postrenal

What kind of kidney injury would an 82 y/o with flu-like symptoms have?

Prerenal

What kind of kidney injury would a 30 y/o with renal colic have?

Postrenal

What kind of kidney injury would a 25 y/o who ODed on fentanyl and now has rhabdomyolysis have?

Intrea

What kind of kidney injury would a 55 y/o who is post-op CABG have?

Prerenal

What kind of kidney injury would a 60 y/o with a cervical mass have?

Post renal

Urine specific gravity

Weight of solute in solution

Normal is 1.005 to 1.030

Urine osmolality

# of dissolved particles per unit of water in the urine

Oliguria urine output

> 400 mL/24h

Anuria urine output

> 50 mL/ 24h

S/S of hyperkalemia

Muscle weakness

Urine (oliguria, anuria)

Respiratory distress

Decreased cardiac contractility

EKG changes

Reflexes (hyperreflexia, areflexia)

EKG of hypokalemia

Depressed ST, diphasic T wave, prominent U wave

EKG of hyperkalemia

Peaked T wave, widened PR interval, widened QRS complex, loss of P wave, sinusoidal wave