Perioperative Care—Renal Failure
Concept
Multiple causes, but can be broken down into prerenal, intrarenal, and postrenal causes. Certain information on H+P and your diagnostic tests will help you here.
Prerenal
Hypovolemic shock Hemorrhagic shock Septic shock
Third space losses (burns, pancreatitis, long operation, cirrhosis)
Vascular (emboli, renal artery occlusion) Abdominal compartment syndrome Pump failure
Intrarenal
ATN—from ischemia—secondary to inadequate perfu- sion (from prerenal cause above)
Acute interstitial nephritis—secondary to medication
Postrenal
Urethral obstruction (catheter/prostate)
Bilateral ureteral obstruction (intra-op injury, retroperi- toneal fibrosis)
Always want to convert oliguric renal failure into non- oliguric. Most often cause will be hypovolemia in surgical patients.
Way Question May be Asked?
“You are called to see a patient 6 h s/p AAA repair whose urine output has been 15 cc the past 3 h. What do you want to do?”
Question may be after any operation or in the management of any patient for example, s/p multiple trauma, burns, APR.
How to Answer?
History
I/Os
Intra-op fluids
Clamp time on AAA (supra or infrarenal) History of renal disease
Nephrotoxic meds Diuretic use
Recent transfusions (hemolysis with precipitation in renal tubules)
Trauma with major muscle injury (myoglobinuria)
Physical Exam
Vital signs (shock?) Skin (turgor?) Mucous membranes Chest (CHF?)
Abdomen (distended bladder?)
Check Foley (is one in place? has it been flushed?) Bladder pressures (compartment syndrome)
Diagnostic Tests
Complete labs BUN/Cr ratio
U/A (protein with glomerular disease, eosinophils with interstitial nephritis)
Urinary electrolytes (urinary Na < 20 suggests prerenal etiology)
U/S to evaluate kidneys Obstruction
Confirm two kidneys
CVP or SGC to determine volume status +/− IVP to evaluate kidney function
Confirm no postrenal obstruction
(careful—die load—use non-nephrotoxic contrast agents)
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+/− Renal Scan—MAG3 scan, useful to assess kidney perfusion
Surgical Treatment
(1) Low threshold for CVP, txfr to ICU, SGC
(2) D/C any nephrotoxic drugs and supplemental K+ (3) Go through your DDx for renal failure
(4) Fluid resuscitation and monitor hourly UO (5) +/− Dopamine at renal doses
(6) Lasix to convert to non-oliguric renal failure (7) +/− Mannitol
(8) Monitor electrolytes closely (9) Consider dialysis
Common Curveballs
Indications for dialysis
Asked to describe how to measure bladder pressures?
Their significance?
Asked how to treat abdominal compartment syndrome Patient will be unresponsive to all resuscitative meas-
ures
Patient will have myoglobinuria and asked your man- agement (alkalinize urine)
Patient will have transfusion reaction and development renal failure and you’ll be asked how to manage Patient will have only one kidney
Patient won’t respond to fluid boluses
Patient will be elderly with brittle heart/prone to CHF/low EF
Won’t be able to place foley catheter Patient will have hematuria
Strikeouts
Not breaking DDx down into prerenal, intrarenal, and postrenal causes
Not placing at least CVP after two fluid boluses with- out a response
Not being aggressive with resuscitation of patient Not identifying abdominal compartment syndrome Performing angiogram acutely
Performing renal biopsy acutely
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