Approach to the Acute Kidney Injury Consult

Jehan Bahrainwala MD

Assistant Professor of Medicine

Renal, Electrolyte and Hypertension Division

Outline

• Case 1: Approach to the AKI Consult • History

• Exam

• Data

• Differential Diagnosis

• Case 2: Renal Replacement therapy for AKI• Indications

• Modality review

• Trouble shooting CRRT

Approach to the AKI consult

When the triage fellow gets a page regarding an AKI consult, use the following checklist:

Name/Location

Reason for consult

Urgency of consultEmergent dialysis needs?Emergent electrolyte management?Respiratory status?Glomerulonephritis concerns?

Another renal fellow will call you with additional questions as needed

Case 1: Patient CC

• 66yo Caucasian male PMH of osteoarthritis, BPH, DM II on metformin, hypothyroidism admitted for R TKR on 3/25/19. His Cr was 0.7 mg/dl pre op. Patient is admitted to the orthopedic floor post op. On 3/27/19-his Cr is 3.14 mg/dl. Orthopedic intern calls you for AKI Consult.

• How will you approach this AKI consult?

Case 1: CC- Approach to AKI ConsultHISTORY

What history information will you dig for in EPIC?• Any significant events/history• Nephrotoxic medications: Contrast, Antibiotics, ACEI/ARB/Diuretic, NSAIDS, Non prescription supplements,

Chemotherapy, Illicit drugs

What will you ask the patient?• If the patient cannot talk to you: remember to get collateral from family, check physical chart for OSH records,

check CARE EVERYWHERE for EPIC OSH records• Prior history of CKD? AKI? Dialysis?• Symptoms (thirst, orthostatic, voiding issues, PO intake)?• Uremic symptoms?

What questions do you have for the orthopedic intern?• She tells you that his bladder scan showed 500 ml of urine• She ordered an RP US, results pending• She also adds “oh and yesterday he had this red rash after his second Vancomycin dose”

Case 1: CC -Approach to AKI Consult

EXAM

What will you look for on your exam?• Volume status, rash, cholesterol emboli, asterixis, pericardial rub, mental

status

• POCUS

What exam data should you look for in EPIC?• UOP trends, I/O –negative/positive, Daily weights, Vital signs- hypotension

• Review anesthesia event

ANESTHESIA EVENTReview for post operative consultsUnder Chart Review-> Encounters Anesthesia EventReview: intraoperative hypotension, pressor needs, blood loss, urine output, nephrotoxic medications

Case 1: CC- Approach to AKI Consult

DATAWhat are you going to request at the time of consult?What data will you look for in EPIC?

• Baseline Cr- Medview, Care everywhere, get PCP/OSH records• Onset of AKI-Trend the Cr (can graph it)• BMP +/- Ionized calcium, Phosphate, Magnesium• ABG• Urinalysis with microscopy• UPCR /UACR• FeNA if oliguric• RP US• Bladder scan• GN concerns-Viral serologies, complement, serologies

Approach to the AKI consult-Sediment exam

• When get called about the consult-ask for a urine sample

• Spin urine for AKI consults• Especially when concern for intrinsic disease• Spin as soon as possible

• Prefer tubing to Foley bag

• Dipstick/SSA test

• UA +Sediment exam• Document/Picture in EPIC

• Triage: any emergent biopsy needs?

Case 1: CC- Approach to AKI Consult

DATA

• FLOOR SPECIFIC

• Cardiac floors (HUP-F5,8,10,11; PPMC-Cupp 3S, PAC3) -EKG, recent echo, RHC numbers

• Oncology floors (Rhoads)-TLS labs, SPEP, UPEP, K/L

• Trauma floors (4 PAC at PPMC)-CK

• Transplant floors (S11)-CNI drug levels, transplant US, Urine culture

• Most ICUs-daily CXR for pulmonary edema

EPIC Dot phrase

• AKI Exposures

• Recent contrast exposure: {YES/NO (DEFAULT TO NO):501757}.

• Documented hypotension: {YES/NO (DEFAULT TO NO):501757}.

• Documented exposure to nephrotoxin: {YES/NO (DEFAULT TO NO):501757} -***

• Significant use of NSAID, herbal medications, illicit drugs and other OTC medications: {YES/NO (DEFAULT TO NO):501757} -***

• AKI Risk Factors

• CKD stage {RENAL CKD STAGE:106672}

• History of DM: {YES/NO (DEFAULT TO NO):501757}- ***

• Family History of ESRD: {YES/NO (DEFAULT TO NO):501757} -***

Case 1: CC -Approach to AKI Consult

66yo Caucasian male PMH of osteoarthritis, BPH, DM II on metformin, hypothyroidism admitted for R TKR on 3/25/19. His Cr was 0.7 mg/dl pre op. Patient is admitted to the orthopedic floor post op. On 3/27/19-his Cr is 3.14 mg/dl. Orthopedic intern calls you for AKI Consult.

• The intern told you about “urinary retention” and “a rash after Vancomycin.”

• You tell the intern to place a foley catheter

Case 1: CC- Approach to AKI Consult

You are consulted POD #2. On further EPIC review and after interviewing the patient you gather the following:

Anesthesia event was unremarkable

POD #0: Pain control with Tylenol, gabapentin, Ropivicaine via pump, standing Celecoxib 200 mg BID

POD #1: had sudden onset of ‘dizziness and rash’, hypotensive to 60s/40s, improved with 2L IVF to 90s/50s.

POD #2: ongoing SBP in the 90s, patient tells you his baseline SBP is 120-130s not on any medications. He has a poor appetite and feels lightheaded. He has had issues with urinary retention in the past needing a catheter. He denies taking any medications except what is prescribed inpatient. His rash has resolved. He feels like his arthritis is flaring up in multiple joints.

He has made 400 ml of urine x 24 hours. RP US: normal kidney size and echotexture, no hydronephrosis. The nurse threw away the urine and you have no sample

You note that his platelets one month ago were 257, today down to 59 K/uL. Hgb 13.6 g/dl pre op, down to 9.2 g/dl.

Case 1: CC- Approach to AKI ConsultWhat is your differential at this point in time?What supports:

Pre Renal injury?

Ischemic Acute tubular necrosis?

poor PO, NSAID use, volume depleted, hypotensive, blood loss

Allergic interstitial nephritis ?

AKI, rash, culprit drug (NSAID)

Obstruction?

unlikely given no hydronephrosis on US, just some brief retention resolved with foley

Anemia, thrombocytopenia, AKI-suggestive of any diagnosis?

TTP, DIC, infection, malignancy, malignant HTN, SLE, scleroderma, APLS, SCT, drugs

HIT-renal atery thrombus?

Case 1: CC- Approach to AKI Consult

What recommendations will you give the intern?

• Make sure the metformin is held

• Your assessment suggests he is quite volume depleted and you ask the intern to give more fluid and keep the foley in for now to track UOP

• POD #3: his Creatinine continues to rise. You also ask the intern to get hematology involved as his platelets continue to drop and hold the heparin

Case 1: CC- Approach to AKI Consult

This is his Cr trend. On POD #5, the team calls you

-does he need a renal biopsy?

-does he need dialysis?

You finally get a urine sample to spin and it shows a mix of granular and muddy brown casts

Case 1: CC- Approach to AKI Consult

Re the Rash: A&I consulted. Per their note “erythematous, mildyraised, not pruritic, medications received seem unlikely to cause drug rash, NSAIDS potentially the only culprit, no other work up recommended”

Re the thrombocytopenia: Hematology consult states “thrombocytopenia most likely consumption and dilution from recent surgery, no schistocytes on smear”

Re his polyarthralgias: Rheumatology consult “strong family hx of RA, current symptoms and exam not c/w with inflammatory arthritis, overall history bit confusing but most likely OA and unrelated to AKI.”

Case 1: CC- Case of severe Ischemic ATN

Outline

• Case 1: Approach to the AKI Consult • History

• Exam

• Data

• Differential Diagnosis

• Case 2: Renal Replacement therapy for AKI• Indications

• Modality review

• Trouble shooting CRRT

Case 2: Patient GD 45 yo AA male h/o HTN s/p multiple GSW to abdomen and RLE rushed to OR for ex-lap; s/p 8U PRBC, 5U platelet, 3U FFP. Post operatively transferred to the Trauma ICU. He had significant bleeding into his RLE. His abdomen was left open. Surgery plans to go to the OR tomorrow to wash out his RLE and hopes for potential abdomen closure in 2-3 days.

Exam: on Neo @ 100, Levophed @ 10 with MAP 55. Intubated on FiO2 70%. 1+ pitting edema. Abdomen open. Between his drips and medications, he is getting around 150-200 ml per hour. He is currently 4.5L positive.

Data:• BMP Na 135 K 5.9 Cl 105 CO2 19 BUN 64 Cr 3.2 ; CBC Hgb 9 Plt 202 WBC 13• CK 120024503600• pH 7.3 pCo2 42 paO2 87 98%• CXR with pulmonary edema

Case 2: Patient GD

It is 10PM. The surgical intern calls you because the UOP in the OR was 150 ml x 6 hours. He has been in the ICU x 2 hours with zero UOP.

What is going through your mind at 10 PM when you hear about this case?• Muscle injury + massive transfusion K and Phos trends?

• Any ureter/renal injury from the multiple GSW?

• Need for RRT support intra operatively tomorrow?

• High obligate input with high FiO2 and pulmonary edema with oliguria-can he tolerate any more volume?

• Do I need to start removing volume now?

• Open abdomen-will they be able to close in a few days?

Case 2: Patient GD

It is 10PM. The surgical intern calls you because the UOP in the OR was 150 ml x 6 hours. He has been in the ICU x 2 hours with zero UOP.

“He has Oliguric AKI. I need your help.

His pressure is low, I was thinking about giving 2L of LR…..

He has no EKG changes, so I ordered Kayexalate for the potassium..”

What will you tell surgical intern right now before you have seen the patient?

• No more fluid!! No kayexalate!!

Case 2: Patient GD

Does this patient need RRT?

You discuss the case with your attending and decide to initiate RRT in the setting of

1. Hyperkalemia

2. Volume overload

3. Hypoxia

Do not forget to get consent!

Tolwani, A. (2012). Continuous renal-replacement therapy for acute kidney injury. New England Journal of Medicine, 367(26), 2505-2514.

Case 2: Patient GD -Access for RRT

What access will you ask the team for?

• Non tunneled initially

• Preferred Catheter location:

• RIJ preferred, mobilize patient

• Consider femoral BMI < 24, do not need to mobilize early, emergent line/no US available

• LIJ and subclavian risk of central venous stenosis

• What is likelihood of needing permanent access?

Case 2: Patient GD -Modality

Marshall, M. R., & Golper, T. A. (2011, March). Low‐efficiency acute renal replacement therapy: role in acute kidney injury. In Seminars in dialysis (Vol. 24, No. 2, pp. 142-148). Blackwell Publishing Ltd.

SCUF iUF

CAPD

CCPD

What modality will you choose and why?

Indications for CRRT

• ICU setting (Room/RN/Machine availability)

• Hemodynamically unstable patient• Slower rate of fluid removal (4L in 4 hours of iHD=~1L/hour, 4L in 24 hours of

CRRT= ~166ml/hr)• Avoid UF rate > Plasma refill time• Avoiding hypotension essential to aid renal recovery• Improved fluid status

• Risk of cerebral edema• Slower rates of urea clearance decrease water shifts and cell edema• Preserve cerebral perfusion pressure• Neuro ICU patients, Fulminant Liver failure

Cerdá, Jorge, and Claudio Ronco. "The clinical application of CRRT—current status: modalities of continuous renal replacement therapy: technical and clinical considerations." Seminars in dialysis. Vol. 22. No. 2. Blackwell Publishing Ltd, 2009.

Indications for iHD

• Hemodynamically stable patients • Can tolerate higher UF rate

• No concerns about cerebral edema

• Therapeutic priority is mobilization and rehabilitation

INTERMITTENT RRT CONTINUOUS RRT

PROS• Lower cost• Flexible timing• Less anticoagulation needs• Faster correction of metabolic

derangements• Faster UF• Faster clearance of toxic drugs

PROS• Stable and predictable clearance of

solute and water• Stable ICP• Less hypotension

CONS• Hypotension-hinders risk of AKI

recovery, ischemia• Limited duration of therapy• Cerebral edema

CONS• Continuous-limits mobility• Higher cost• Need for ICU• Anticoagulation-bleeding risks

Modality of RRT

TRUE OF FALSE:

1. iHD offers an overall survival benefit when compared with CRRT

2. Based on current data, modalities should be considered equivalent and cannot make recommendation regarding use of CVVHD, CVVH or CVVHDF

3. Dialysis depends on convection whereas filtration depends on diffusion

4. Filtration is more effective than diffusion at removing middle molecules

5. Protein bound drugs are easily removed by CRRT/IHD

Principles of RRT

• Removal of unwanted solutes and water through a semi permeable membrane

• Fluid removal• Ultrafiltration

• In hemodialysis: generation of transmembrane pressure > plasma oncotic pressure

• Some small molecule clearance

Deepa, C., and K. Muralidhar. "Renal replacement therapy in ICU." Journal of anaesthesiology, clinical pharmacology 28.3 (2012): 386.

Principles of RRT

Solute removal• Influenced by: Membrane surface area, pore size, thickness of

membrane

• Diffusion

• electrochemical gradient created across a membrane using a dialysate solution

• Convection

• transmembrane pressure-driven ‘solvent drag’ is created where solute moves together with the solvent across a porous membrane

Deepa, C., and K. Muralidhar. "Renal replacement therapy in ICU." Journal of anaesthesiology, clinical pharmacology 28.3 (2012): 386.

Case 2 Patient GD: Orders, Dosing, ClearanceWhat parameters do you have to order in your order set?

Blood Flow QB 200-400 ml/minHigher clotting at lower Qb

Dialysate Flow/Replacement Fluid Rate QD “X” L/hour

24 hour I/O goal Even/ negative “X” Liter in 24 hour

Protocol driven lab frequency Every 8 hours

Potassium Bath 0K/ 2K/ 4K depending on serum K

What determines drug dosing and clearance?

Clearance = QD (Qd 1L/hr = 17 ml/min)

Dosing: Deliver an effluent volume of 20-25ml/kg/hr

(For ex: 2L/hr in a 70 kg man = 28 ml/kg/hr)

Case 2: Patient GD

The team places a RIJ NTDC. You recommend CVVHD at a Qb of 300 ml/min, Qd 3L/hr, no UF and no heparin. The circuit goes up at 1AM.

6AM Pre rounds: You notice high access pressures and the nurse has the Qb at 200 ml/min instead of 300 ml/min per your order. The blood work is stable, you do not make any changes.

3PM: The nurse reports the circuit clotted and is down. You tell her to start a new circuit.

11PM: The nurse calls your colleague to report the circuit has clotted again. The K is 5.2 mmol/L. What will you do next?

Case 2: Patient GD – Troubleshooting CRRT

• What are potential etiologies for the problem?

• What do you tell the nurse to do?• Do not restart, re assess in the AM, trend labs

• Restart circuit in same modality

• Change modality

• Change the line

• Start Coumadin

• Instill TPA in the line

• Start post filter heparin

• Start pre filter heparin

Case 2: Patient GD – Troubleshooting CRRT

• Tried TPA at the port. Helped overnight. The following afternoon, recurrent issues of clot removal at the port and clot in the filter.

What do you think is going on?

Complications of RRT: Catheter Malfunction• Early dysfunction: Malposition

• Kinking• Short catheter

• Late dysfunction: Thrombosis• At the catheter tip• Within the catheter lumen• Around the catheter (fibrin sheath)• Entire vein (mural thrombus)• In the right atrium

• Infection

Complications of RRT: Catheter Malfunction

• What occurs clinically?• High access pressures, machine alarming, resistance to blood return, unable

to withdraw blood, low blood flow rates

• How can you troubleshoot?• Consider CXR to confirm position• Patient repositioning • Flushing the line with saline• Reversing the lumens• Instillation of TPA 2mg/ml, dwell time varies

• Low threshold to change catheter or consider fibrin sheath stripping with IR

Complications of RRT: Clotting

Clotting of machine• Common

• Interrupted treatment inadequate dialysis, higher cost, unnecessary blood loss, strain on nursing

• Trouble shooting:• Need for anticoagulation (discussion with primary team re

bleeding risk and safety of pre-filter heparin)• CVVH with pre filter Replacement fluid• Increase blood flow

Complications of RRT: Other

• Bleeding

• Air Emboli

• Platelet consumption

• Catheter related blood stream infections• Duration of catheter

• How often catheter is accessed

Case 2: Patient GD – Troubleshooting CRRT

• The team places a new line

• You switch his modality to CVVH with pre filter replacement fluid

• You avoid heparin given his ongoing surgeries

Tolwani, A. (2012). Continuous renal-replacement therapy for acute kidney injury. New England Journal of Medicine, 367(26), 2505-2514.

Continuous RRT Circuit

Case 2: Patient GD

45 yo AAM, GSW victim. He has been on CRRT for 3 weeks. He is s/p multiple surgeries, doing well, wounds are healing, he was extubated 2 days ago. His pressors were discontinued 36 hours ago. His SBP is in the 130s. He put out 200cc of urine in the last 24 hours. His machine expired 2 hours ago. The RN calls you-should I restart the machine?

• What do you want to do?

• Do not restart CRRT, pull the catheter

• Restart CRRT

• iHD session today

• iHD session tomorrow

• He made 200 cc, he never needs RRT again

• Do not restart CRRT, reassess tomorrow

Discontinuation of RRT

• Scarce data on optimal timing to stop RRT

• Monitor for recovery:• Urine output• Creatinine trends

• Trial of diuretic for fluid management if MAP stable

Transitioning from CRRT to iHD

• No signs of renal recovery

• Needs to be hemodynamically stable

• Needs low obligate input in 24 hours

• Remember to adjust drug dosing

Case 2: Patient GD

He was successfully transitioned to iHD given ongoing oliguria and obligate input of 2L per day.

No signs of recovery yet.

Drug dosing in CRRT

• Drug clearance complex and variable• Drug factors: bioavailability, protein binding, lipid solubility, drug metabolism

• RRT factors: molecular weight of drug, mode of RRT, flow rates, membrane pore size, pre vs post filter RF, age of filter

• Increased drug clearance• Drugs with low protein binding

• Drugs that are not lipid soluble (lower Vd)

Drug dosing in CRRT

• Use your pharmacists

• Check drug levels

• Adjust dosing: when circuit goes down or change in dialysate flow

• Avoid UNDERDOSING

Lewis, Susan J., and Bruce A. Mueller. "Antibiotic dosing in critically ill patients receiving CRRT: underdosing is overprevalent." Seminars in dialysis. Vol. 27. No. 5. 2014.

Trotman, Robin L., et al. "Antibiotic dosing in critically ill adult patients receiving continuous renal replacement therapy." Clinical infectious diseases 41.8 (2005): 1159-1166.

Take home points• When approaching AKI, use a systematic approach of history/exam/data

collection from both the bedside and the EMR

• Sediment exam in a timely fashion can be very valuable to diagnosis/management

• Common indications for RRT for AKI include volume overload, hypoxia, electrolyte abnormalities, intoxications, acidemia

• CRRT is preferred in patients that are hemodynamically unstable and at risk for cerebral edema

• Catheter dysfunction and clotting are frequent complications of CRRT and need to be addressed in a timely fashion to avoid inadequate dialytic therapy

• Transition to iHD when patients are stable hemodynamically, have low obligate input and need to be mobilized

• Drug dosing should be adjusted for any change in prescription or modality

• Avoid hypotension and continue to monitor UOP, Cr trends to assess for AKI recovery to discontinue RRT

Questions?

Thank you

jehan.Bahrainwala@uphs.upenn.edu