Renal Pathophysiology Flashcards
What is azotemia?
The accumulation of nitrogenous waste products due to a
decrease in the kidney’s ability to excrete them.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1309.
How do prerenal, renal, and postrenal azotemia
differ?
Prerenal azotemia typically results from an abrupt decrease in
renal blood flow. Renal azotemia is due to a disorder in the
renal parenchyma from intrinsic disease, ischemia, or
nephrotoxins. Postrenal azotemia occurs as a result of
obstruction of the urinary outflow tract.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 1309.
Is an elevated BUN always indicative of renal
dysfunction?
No. Increased protein intake can elevate the BUN level leading
to an inaccurate diagnosis of renal dysfunction. Other causes
of altered BUN levels include altered intravascular fluid volume
and co-existing diseases.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 335-336.
How does the urine sodium level change with renal
tubular damage?
The urine sodium increases. Urinary sodium > 40 mEq/L is
associated with damage to the renal tubules.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 352.
Which is associated with the highest incidence of
postoperative renal failure in the patient undergoing
abdominal aortic aneurysm repair, infrarenal,
suprarenal, or supraceliac clamping?
Suprarenal clamping has an incidence of postoperative acute
renal failure (8%) and is higher in incidence than supraceliac
and infrarenal clamping. The incidence of acute renal failure
increases substantially (10-30%) in cases involving complicated
aneurysms.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 480.
What form of renal failure is most commonly
associated with the perioperative period?
Prerenal causes of renal failure are related to decreased blood
flow to the kidneys such as blood and volume losses, cardiac
pump failure, renal vascular disease, and clamping and
comprises about 60% of all causes of renal failure. Acute
tubular necrosis from ischemia or toxins such as
aminoglycosides or radiocontrast media is the most common
renal cause of acute renal failure and comprises 30% of all
causes of renal failure. Postrenal causes such as obstructive
nephropathy and ureteral obstruction comprise the remaining
10%.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 643.
Massive proteinuria (exceeding 750 mg/day) would be consistent with extensive damage to what renal structure?
Proteinuria greater than 750 mg/day is always abnormal and
usually indicates severe glomerular damage. It may also be
present when the renal tubules fail to reabsorb the small
amount of protein that gets filtered.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 743.
How does renal tubular damage affect the urine and
plasma osmolality?
A normal urine osmolality (around 1400 mOsm/Kg compared to
the normal plasma osmolality of about 290 mOsm/Kg) indicates
an excellent ability of the tubules to concentrate urine. A
situation wherein the plasma and urine osmolality become fixed
together indicates serious damage to the renal tubules.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 742-743.
What does the presence of nitrites in the urine
indicate?
Nitrites are typically positive if large numbers of bacteria are
present in the urine.
Ferri FF. Ferri’s Best Test. 3rd ed. Philadelphia, PA: Elsevier
Saunders; 2015: 186.
How do patients with renal disease respond to
different intravenous induction agents?
Although the pharmacokinetic profile of barbiturates and
etomidate are largely unchanged in patients with renal failure,
the dose must often be decreased due to an enhanced
sensitivity to the drugs, possibly due to an increase in free
circulating drug related to decreased protein binding. The
pharmacokinetic profile of ketamine and propofol are also
largely unchanged by renal failure. Repeated doses of
ketamine however, can result in accumulation of the drug as
some of its active metabolites depend upon renal excretion.
Additionally, many patients with renal vascular disease may
exhibit hypertension which may be worsened by the
administration of ketamine.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 658.
Is nitrous oxide contraindicated in patients with renal
failure?
Although some clinicians avoid nitrous oxide because they wish
to administer 100% oxygen in the presence of anemia due to
renal failure, this omission appears to only be justified when the
serum hemoglobin is
Is succinylcholine contraindicated in patients with
renal failure? Why or why not?
Succinylcholine can be used safely in patients with renal failure
provided the serum potassium is less than 5 mEq/L. There are
some cases describing decreased pseudocholinesterase levels
in uremic patients after dialysis. However, the risk of prolonged
duration of action appears to be minimal.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 659.
How will the pharmacokinetics of anticholinergics be
affected by the presence of renal failure?
Atropine and glycopyrrolate can be safely used in patients with
renal failure, but because about 50% of the drugs or their
metabolites are excreted in the urine, repeat doses can
potentially accumulate. Scopolamine is not as dependent upon
renal excretion as atropine and glycopyrrolate, but the presence
of azotemia can enhance its central nervous system effects.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 658.
Which two intravenous opioids would be the most
likely to result in prolonged action in patients with
renal failure?
Most of the commonly used opioids are inactivated by the liver
and some or all of the metabolites are excreted in the urine.
With the exception of morphine and meperidine, most do not
result in significant prolongation. The metabolites morphine-6-
glucuronide and normeperidine however, are capable of
exerting clinical effects and may result in respiratory depression
in patients with renal failure.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 658
How are the pharmacokinetic profiles of
benzodiazepines altered by renal failure?
Most benzodiazepines undergo hepatic metabolism and
conjugation and are eliminated by the kidneys. They are highly
protein bound, which can result in increased drug sensitivity due
to hypoalbuminemia. Diazepam may exhibit prolonged action
due to accumulation of active metabolites.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 658.
