Acute Kidney Injury

FY1 Teaching Nov 30th 2011

Dr Jack BondST5 Nephrology

Acute Kidney Injury - Objectives

• To recognise AKI

• To differentiate between pre-renal, renal and post renal causes of AKI

• To recognise and manage hypovolemia

• To manage hyperkalemia and pulmonary odema

• To know indications for emergency dialysis

• How to call a nephrologist without getting shouted at

11/21/2011June 2009

NCEPOD Conclusions - Summary

• There were systematic failings in AKI care

• Failures in: Recognition and management of AKI Recognition and management of complications Referral and support

• Failures in recognition of the acutely ill

AKI Questions

• Please complete the questionnaire

• Anything you want to ask about AKI

• Will answer them anonymously during the lecture

Managing AKI

Is your patient really sick? Get help

Volume assess + fluid challenge

U+Es + blood gas

Urine dip

U/S abdo

Nephrology referral

Definition of AKI

Rise in serum creatinine >50% from baseline

Or

Urine output <0.5ml/kg/hr for 6 hours

Creatinine criteria Urine output criteria

≥ 50-100% rise in Cr

Urine output <0.5 ml/kg/hrfor 6 hours(=240 ml at 80 kg)

SIMPLIFIED RIFLE OR AKIN DEFINITIONUsually based on Creatinine rise Loss and End stage components of RIFLE now dropped

101-200% rise in Cr

Urine output <0.5 ml/kg/hrfor 12 hours(= 480 ml at 80 kg)

>200% rise in Cr

Urine output <0.3 ml/kg/hr for 24 hours or anuria 12 hours

Risk orAKIN 1

Injuryor AKIN 2

Failureor AKIN 3

Highsensitivity

HighspecificityOliguria

Which scenario is AKI? 1. 85 male, D+V, creat 120, usually 80

2. 82 female, D+V, Urea 15.2, Creat 150

3. 60 male, diabetic, creat 250, usual 200

4. 74 male, legionella pneumonia, Na 118, Creat 130, usual creat 70

5. 63 female, diabetic, myocardial infarct, eGFR 25, usual eGFR 35

11/21/2011

Slow rise in Cr untileventually a new steady state is reached

Large acute drop in GFR with oligoanuria

Only a small early rise in Cr: not easy to recognise as AKI

Suspect AKI in a sick patient with a modest rise in their creatinine

GFR falls rapidly to near zero- only shown by oliguria

11/21/2011

Effect of AKI on odds of deathChertow GM et al J Am Soc Nephrol 2005

Rise in serum creat > 50% baseline

• baseline creatinine of 80 mmol/L

• Rises to 120 mmol/L

• Significant kidney injury

• This is the moment to act – it is too late when the creatinine reaches 400

Things that don’t diagnose AKI

• Urea – not specific

• eGFR – used in Chronic Kidney disease

• Electrolytes disturbance – A result of AKI, but not specific

Case

66 year old man is admitted to A+E with breathlessness. He has been unwell for a week, coughing up phlegm and having fevers. His past medical history includes diabetes and hypertension. His medication is metformin, aspirin, ramipril, atenolol and simvastatin.

On examination he is unwell. His obs are BP 85/50, HR 115, Sats 92% on air, RR 25, Temp 38.3. You hear coarse crackles on the right side of his chest. A CXR confirms pneumonia.

His blood results come back which show Na 130, K 4.5, Urea 14.3, Creat 189. The nurse asks you to assess him as he hasn't passed urine since admission.

Case

Outline the management you would undertake in A+E.

What is the likely cause for his renal failure?

What investigations would you order and why?

What risk factors are evident in this man's case that make him more likely to have renal failure?

Managing AKI

Is your patient really sick? Get help

Volume assess + fluid challenge

U+Es + blood gas

Urine dip

U/S abdo

Nephrology referral

AKI risk factors

• Most people have > 1 risk factor

• Age• Drugs (ACEi, diuretics, NSAIDS)• Chronic kidney disease• Hypovolemia/Sepsis• Diabetes

AKI: causes

• Important to attempt to categorise broadly into one of 3 groups

• sepsis/hypovolemia 70%• drug related, acute GN 20%• obstruction 10%

PRE-RENALRENAL

POST-RENAL

Cause of AKI – 3 tests

3 assessments result in a 45% 36 months survival, compared with 15% for 0 assessments

o Fluid/volume assessment PREo Urinalysis RENALo Ultrasound POST

11/21/2011

Question

Which of these is the most useful indicator of hypovolaemia?:1.capillary refill time > 5 seconds2. jugular venous pulse not visible at 30º3.postural pulse rise > 30 bpm4.systolic blood pressure < 95 mm Hg5.systolic BP rise with

250 ml saline bolus > 20 mm

Volume assessment - key

MEWS score Cap refillBP, HR, Postural BPJVPAuscultate lungsPeripheral odemaUrine output

Volume assessmentYou are the FY1 covering orthopedics. You have been asked to see 74 female post #NOF as she has low urine outputPMH - diabetes, hypertension

Creat 150, baseline 100, urine output 20mls in last hourCRT 2 secs, BP 110/50, HR 98, JVP ??, chest couple of creps, no edema

Is patient fluid depleted, euvolemic or overloaded?

How much fluid would you prescribe?

Volume management

Most patients are hypovolemic (70%)

If not grossly overloaded – fluid challenge - 500ml + recheck

“Normal” BP for 75 year old – 150/70 - a post op BP of 110 is relatively

hypotensive

Volume assessment

Furosemide in ARF – meta-analysis- Ho et al 2006, BMJ

Does not improve mortality

Does not reduce need for dialysis

Urinalysis

- this points towards intrinsic renal disease Ie glomerulonephritis

- blood and proteinuria on dipstick = nephrology referral

AKI investigations

u/s urinary tract

- suspect obstruction in men with prostatic symptoms

- palpable mass

- intra-abdominal malignancy compress ureters with no bladder palpable females

- where cause not obvious

Managing AKI

Is your patient really sick? Get help

Volume assess + fluid challenge

U+Es + blood gas

Urine dip

U/S abdo

Nephrology referral

AKI QUESTION TIME

Hyperkalaemia - True/False

1. Calcium gluconate acts by reducing the serum potassium T/F2. Insulin/dextrose infusion requires 30mins to shift potassium into cells T/F3. Insulin/dextrose infusion effects last for 24 hours T/F4. Salbutamol nebulisers have the same effect as insulin/dextrose infusion T/F5. IV sodium bicarbonate can reduce potassium T/F6. to treat hyperkalemia you would prescribe 50 units of actrapid in 50ml 50% dextrose T/F7. 10ml of 10% Calcium gluconate is the correct prescription for the treatment of hyperkalemia T/F 8. Calcium resonium acts within minutes to reduce serum K T/F

Hyperkalemia

K+ >6.5

- 1st – repeat measure on VBG/ABG (takes 5 mins)

- if true – ECG - if life threatening changes

o Calcium gluconate 10ml 10% stat (through big vein – tissue burns)

- thereafter 10 units actrapid in 50mls 50% glucose over 30 mins.

Hyperkalemia

Insulin/dextrose – lasts 4 hours only

- in meantime correct cause of high K - Repeat ABG at 4 hours to see if better

If K+ still high – DIALYSIS MAY BE INDICATED

Hyperkalemia

Salbutamol nebs (10-15mg) have same action as insulin/dextrose and may be an option - caution in cardiac disease

IV sodium bicarbonate 1.26% - useful in dehydrated patient who is

ACIDOTIC - discuss with senior, but consider if HCO3 <18

and needs ongoing fluid replacement - worsens pulmonary oedema ++

Hyperkalemia

Key is to recheck after treatment

Correct underlying cause

Consider dialysis

Pulmonary oedema in AKI

ABCDE approachOxygenGTN infusionDiamorphineConsider large dose furosemide 250mg IVCPAPITU/ventilationCorrect cause of renal failure (days)

Dialysis indications

• Consider haemodialysis/haemofiltration if:

• Resistant hyperkalaemia >6.0• Fluid overload and no urine output• Persistent acidosis pH<7.2

• Call for senior support in all cases• Nephrology referral for dialysis patients

admitted under any other specialty

When to call nephrology

Any known dialysis patient admittedAny known renal transplant patient admitted

Any case of AKI where cause not clearWorsening AKIEmergency dialysis indicationsSuspect glomerulonephritis

What info to have when calling nephrologist

Your (boss') reason for referral The history and background in your head – dont read the notes to me – check with patient if not clear historyThe notes by the phoneThe obs chart by the phone (MEWS, Urine output)A urine dipstick resultYour assessment of the patients fluid statusAn up to date venous blood gas (that day)

Managing AKI

Is your patient really sick? Get help

Volume assess + fluid challenge

U+Es + blood gas

Urine dip

U/S abdo

Nephrology referral

AKI: Summary

• Small changes in creatinine can have grave clinical consequences

• ABCDE assessment and careful management of fluid status is mainstay of treatment

• Get help early