2 Acute Kidney Injury, part 2

Question 1

Mainstay for measuring renal function

Answer 1

Creatinine
Elevations of serum creatinine may take 48 hours after onset of decreased renal function.

Also, in patients with no renal function (GFR = 0), serum creatinine level increseases 1 to 3 mg/dL (88-265 umol) a day

Question 2

Remarks on GFRs and creatinine

Answer 2

Patients with lower muscle mass (e.g., older patients and women) have lower actual GFRs for any given creatinine level

Question 3

Stages of CKD

Answer 3

Stage 1: GFR ≥90 mL/min/1.73m2
Stage 2: 60-89
Stage 3: 30-59
Stage 4: 15-29
Stage 5: <15; dialysis or transplant needed

Question 4

Remarks on GFR calculations

Answer 4

All GFR calculations are based on a steady-state creatinine level, severely limiting their applicability in AKI seen in the ED

Question 5

BUN-to-creatinine ratio

Answer 5

If the patient has normal concentrating ability, in the setting of prerenal AKI, the serum ratio of BUN to creatinine is typically >10

Question 6

BUN level is depressed in

Answer 6

patients with malnutrition and hepatic synthetic dysfunction

Question 7

BUN level is increased in the setting of

Answer 7

protein loading, GI hemorrhage, or trauma

Question 8

This suggests myoglobinuria

Answer 8

finding of hemoglobin on urine dipstck analysis with no red cells on microscopy

Question 9

Test of choice for urologic imaging in the setting of AKI

Answer 9

Renal US
Has approx 90% Sn/Sp for detecting hydronephrosis due to mechanical obstruction

Question 10

kidney dimension of ______ suggests CKD

Answer 10

<9 cm

Question 11

Renal parenchyma should be

Answer 11

isoechoic or hypoechoic compared with that of the liver and spleen.
Hyperechogenecity indicates diffuse parenchymal disease

Question 12

Priority in the treatment of AKI

Answer 12

Resuscitation and treatment of the underlying cause

Question 13

a noninvasive measure of volume status and expected fluid responsiveness

Answer 13

inspiratory collapsibility of the intrahepatic segment of the IVC using bedside US

Question 14

Avoid IV contrast studies if possible for patients with GFR ______

Answer 14

<30 mL/min/1.73m2

Question 15

These conditions are examples in which benefits typically outweigh risk for emergency contrast studies

Answer 15

Major trauma
Aortic dissection
STEMI

Question 16

For patients with abnormal kidney function, for whom contrast-enhanced imaging is planned, the ideal rate and volume of fluid administration is not defined. Commonly used volumes are

Answer 16

500 to 1000 mL of cyrstalloid (PLR or pNSS) prior to the procedure;
however significantly dehydrated patients may need additional volume
The administration rate should be determined by the patient’s comorbidities, as well as any additional needs for ugent hydration.

Question 17

Permanent loss of renal function develops over the course of ___________ in the setting of complete renal obstruction

Answer 17

10 to 14 days

Question 18

Mainstay of treatment for fluid overload in patients with normal kidney function

Answer 18

Diuretics
In the absence of fluid overload, diuretics are NOT recommended for patients with AKI, nor have they been shown to prevent AKI.
Diuretics are used in the setting of mild to moderate AKI when fluid overload is present.

Question 19

Remarks on furosemide stress test

Answer 19

1. Furosemide stress test can be used in the setting of mild AKI (AKIN stage ≤2)
2. To determine diuretic responsiveness as well as to predict worsening renal function
3. Administer 1 mg/kg of furosemide in naive patients or 1.5 mg/kg in those with prior exposure
4. A urine output of <200 mL over 2 hours has a Sn 87% and Sp 84% to predict progression to AKIN stage 3 AKI

Question 20

Remarks on mannitol and dopamine

Answer 20

Mannitol has NO role in the treatment of AKI.
Low (“renal)-dose dopamine does NOT improve renal recovery or decrease mortliaty

Question 21

Hypertension in AKI

Answer 21

Fenoldopam and nicardipine are commonly used in this setting of hypertension in AKI.

Question 22

Metabolic acidosis in AKI

Answer 22

1. In cases where the pH >7.1, treat the underlying cause of AKI first
2. If pH ≤7.1, consider treatment
   - dialysis is preferred in the setting of anuria or fluid overload, because safe effective use of sodium bicarbonate requires urine flow and ability to tolerate a fluid load

Question 23

Suspected hyperkalemia should be treated in the setting with ECG findings of

Answer 23

prolongation of PR interval
peaked T waves
widening of the QRS complex

Question 24

Disposition in AKI

Answer 24

1. Patients with mild prerenal AKI (AKIN stage 1) are eligible for treatment in ED observation protocols anticipating reversibility of renal dysfunction before discharge
2. Patients who do not improve or patients with more severe AKI require hospital admission for evaluation and treatment
3. For patients with severe AKI or for patients with uncertain etiology, nephrology should be consulted

Question 25

Indications for emergent dialysis or renal replacement therapy

Answer 25

Uncontrolled hyperkalemia (K >6.5 or rising)
Referactory fluid overload
Uremic perciarditis
Serum Na <115 or >165
Bleeding dyscrasia secondary to uremia
Excessive BUN and craetinine levels (trigger levels are arbitrariy; it is generally advisable to keep BUN level <100 mg/dL, but each patient should be evaluated individually)

Question 26

Life-threatening poisoning of these dialyzable drugs are also indications for emergent dialysis

Answer 26

Salicylates
Lithium
Isopropanol
Methanol
Ethylene glycol

Question 27

CRS type 1

Answer 27

acute deterioration in cardiac function that causes AKI
type 2 is chronic

Question 28

CRS type 3

Answer 28

aka acute renocardiac syndrome
characterized by an AKI that causes acute cardiac injury and/or dysfunction, such as cardiac ischemia, CHF, or arrhythmias
Type 4 is chronic

Question 29

CRS type 5

Answer 29

secondary to a separate systemic condition such as sepsis

Question 30

American College of Radiology recommendations on Metformin

Answer 30

1. For patients with eGFR ≥30 mL/min/1.73, there is no need to discontinue metformin prior to the procedure or following the procedure.
2. For patients with eGFR <30 mL/min/1.73m2, metformin should be withheld at the time of contrast infusion and for 48 hours after the procedure.
   - the renal function should be reassessed at 48 hours to determine the safe administration of subsequent metformin therapy.