1. Presented By
Abeer elnakera
Lecturer of anesthesia
Faculty of Medicine-Zagazig University RC (UK)
2. Objectives
To
• Describe RIFLE classification of AKI
• Identify the risk factors and causes of
AKI after cardiac surgery
• Explain how to
– Predict
– Prevent and
– Manage acute renal injury after
cardiac surgery
RC (UK)
3. Introduction
Acute kidney injury (AKI) following
cardiac surgery with cardiopulmonary
bypass (CPB) is a serious complication
associated with high morbidity, mortality
and resource utilization.
The incidence of cardiac surgery-
associated AKI (CSA-AKI) in Canada
ranged between 5-30%.
RC (UK)
4. Acute Renal Injury and Cardiac Surgery
RIFLE classification defines:
Three grades of increasing severity of acute
kidney injury which are:
Risk (class R).
injury (class I).
failure (class F).
Two outcome classes:
Loss and end-stage kidney disease. RC (UK)
5. Acute Renal Injury and Cardiac Surgery
Risk:
In which there is increased creatinine×1.5 from base
line and there is 25% reduction in GFR and urine
output become<0.5 ml/kg/h over 6 h.
Injury:
In which there is increased creatinine 2 from base
line and there is 50% reduction in GFR and urine
output become<0.5 ml/kg/h over 12 h.
Failure:
In which there is increased creatinine 3 from base
line and there is 75% reduction in GFR and urine
output become <0.3 ml/kg/h over 24h. RC (UK)
6. Acute Renal Injury and Cardiac Surgery
Loss: Persistent acute renal failure
(ARF). Complete loss of kidney function
for> 4 weeks.
ESRD: End stage kidney disease> 3
months.
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7. Acute Renal Injury and Cardiac Surgery
Underlying Causes of Acute Renal Failure
after cardiac surgery:
•Hypoxia, hypotension, hypovolemia
and dehydration.
•The imbalance between pro and anti-
inflammatory cytokines.
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8. Acute Renal Injury and Cardiac Surgery
Pre-operative Risk Factors
Elderly and female patients.
Obesity (BMI>30kg/ m2).
Low left ventricular ejection
fraction, Congestive heart failure
(CHF), presence of extra cardiac
arteriopathy and the need for intra-aortic
balloon pump (IABP)
RC (UK)
9. Acute Renal Injury and Cardiac Surgery
Pre-operative Risk Factors (cont.):
Insulin dependent diabetes mellitus
Pre-operative significant reduction in
creatinine clearance.
Pre-operative medications like ACE
inhibitors which has been associated with
a 28% increase in post-operative AKI in
cardiac surgery patients.
RC (UK)
10. Acute Renal Injury and Cardiac Surgery
Operative Risk Factors:
Non-isolated CABG surgeries and
emergency/salvage operations.
Complex cardiac cases including aortic root
replacement, aortic surgery and simultaneous
CABG with valve replacement carry higher risk of
CRRT than CABG alone.
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11. Acute Renal Injury and Cardiac Surgery
Cardiac Risk Scoring System:
High mean EURO score and Parsonnet
score can predict the need for CRRT
after cardiac surgery.
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12. Acute Renal Injury and Cardiac Surgery
Operative Risk Factors (cont.):
Prolonged CPB time.
The increase in the length of cross-clamp
time >2hrs.
The increased number of red blood cell
units given.
RC (UK)
13. Effect of Cardio-Pulmonary Bypass On Renal Function
CPB is associated with the precipitous
fall in MAP upon commencement of CPB
which causes activation of renin-
aldosterone system and sympatho-
adrenal axis, leading to increased sodium
retention and renal vasoconstriction.
RC (UK)
14. Effect of Cardio-Pulmonary Bypass On Renal Function
Other vasoactive substances released
during CPB include
complement, kallikrein and bradykinin
contribute to generalized inflammatory
response that increases capillary
permeability. RC (UK)
15. Effect of Cardio-Pulmonary Bypass On Renal Function
Hemodilution with CPB:
The incidence of ARI is higher with severe
hemodilution (nHct <21%) and mild
hemodilution (nHct >25%).
Hypothermia during CPB:
All studies suggest that hypothermia is not
detrimental to renal function.
RC (UK)
16. Acute Renal Injury and Cardiac Surgery
Early Post Operative Risk
Factors
Increase Post Prolonged post- Post operative
operative operative pulmonary
extubation time. ventilation. complication.
RC (UK)
17. Prevention of AKI after Cardiac Surgery
A practical approach to Perioperative renal
protection
Preoperative:
1. Optimize volume status, cardiac output and systemic
arterial pressure.
2. Withhold nephrotoxic drugs.
3. Maintain adequate glycaemic control in diabetic patients.
4. Correct metabolic and electrolyte disturbances.
5. Delay surgery until recovery of acute renal dysfunction if
possible.
6. Arrange pre-operative dialysis for dialysis-dependent
patients.
7. Administer isotonic i.v fluids and N-acetylcysteine for
prevention of radiocontrast-induced nephropathy.
RC (UK)
18. Prevention of AKI after Cardiac Surgery
A practical approach to Perioperative renal
protection (cont.)
Intraoperative:
1. Optimize volume status, cardiac output and systemic arterial
pressure.
2. Avoid nephrotoxic drugs.
3. Consider maintaining adequate glycaemic control in all patients.
4. Maintain adequate flow and mean systemic arterial pressure
during CPB.
5. Limit the duration of CPB.
6. Avoid excessive haemodilution.
7. Avoid red cell transfusion.
8. Consider extra-corporeal leucodepletion.
9. Consider haemofiltration during CPB.
10. Consider off-pump coronary artery bypass surgery.
RC (UK)
19. Prevention of AKI after Cardiac Surgery
A practical approach to Perioperative renal
protection (cont.)
Post-operative:
1. Avoid nephrotoxic drugs.
2. Maintain adequate glycaemic control in all patients.
3. Promptly treat acute cardiac dysfunction.
4. Control haemorrhage.
5. Manage sepsis aggressively.
6. Recognize and treat rhabdomyolysis.
7. Recognize and treat intra-abdominal hypertension.
8. Provide appropriate organ support for multiple organ
dysfunction syndrome.
9. Institute renal replacement therapy for RIFLE grade F
acute renal dysfunction.
RC (UK)
20. Prediction of AKI after cardiac
surgery
• Progression is reversible when early
appropriate interventions implemented
diagnostic biomarkers early
AKI detection.
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21. Diagnosis of AKI after Cardiac Surgery
Characteristics of an Ideal Biomarker:
Should be non invasive (blood or urine
sample), easily measured, inexpensive
and produce rapid results.
Highly specific.
Highly sensitive.
RC (UK)
22. Diagnosis of AKI after Cardiac Surgery
Some of the Biomarkers Used for
Diagnosis of AKI:
•Interleukin-18
•Neutrophil-Gelatinase-Associated
Lipocalin (NGAL)
•Kidney Injury Molecule-1 (KIM-1)
•Tubular Enzymes
•Cystatin C
RC (UK)
23. Treatment of AKI
Indications for RRT:
The usual renal indication for RRT:
Fluid overload unresponsive to diuretic treatment.
Hyperkalaemia (>6.5 mmol/L or rapidly rising
level).
Azotaemia (urea>36 mmol/L).
Sever acidaemia (PH<7.1).
Oliguria (urine output<200ml in 12 hours) or
anuria (urine output<50ml in 12 hours).
Uraemia complication like bleeding, pericarditis or
encephalopathy.
RC (UK)
24. Treatment of AKI
Indications for RRT (cont.):
Non renal indication for RRT:
Removal of endogenous toxins as in severe lactic acidosis.
Patients requiring a large amount of fluid, parenteral nutrient
or blood product but at risk of developing pulmonary oedema
or acute respiratory distress syndrome (ARDS).
Heart failure.
Hyperthermia or hypothermia (core temperature>39.5c
or<30c).
Severe dysnatraemia (Na>160mmol/L or<115mmol/L).
Sepsis and other inflammatory syndromes as ARDS to remove
the inflammatory mediators by hemofiltration.
RC (UK)
25. Treatment of AKI
Continuous renal replacement therapy
(CRRT) is often the preferred choice over
intermittent renal replacement therapy
(IRRT) and peritoneal dialysis in the ICU.
RC (UK)
30. The pathogenesis of kidney injury during CPB is
complex and involves hemodynamic and
inflammatory mechanisms
Intravascular volume expansion, maintenance of
renal blood flow and renal perfusion pressure,
avoidance of nephrotoxic agents, strict glycemic
control and appropriate CPB management are
highly efficient measures for renal protection
Early prediction and establishment of CRRT are
beneficial
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31. Early prediction
Usage of the off-pump technique when
possible.
Perioperative renoprotective measures
Early establishment of CRRT when indicated
RC (UK)
There is no evidence that pharmacological interventions are effective in protecting renal function during surgery.
There is no evidence that pharmacological interventions are effective in protecting renal function during surgery.
There is no evidence that pharmacological interventions are effective in protecting renal function during surgery.
Several Studies show that AKI progression is reversible by appropriate interventions implemented in the early stages of the disease. This finding has prompted interest in identifying diagnostic biomarkers for early AKI detection.
Interleukin-18:Urine IL-18 increased at 4-6 h after CPB, peaked at over 25 fold at 12 h, and remained markedly elevated up to 48 h after CPB. NeutrophilGelatinase-Associated Lipocalin:The urinary NGAL at 2 h after cardiopulmonary bypass was a powerful independent predictor of AKI.Kidney Injury Molecule-1 (KIM-1):An advantage of KIM-1 over NGAL is that it appears to be more specific to ischemic or nephrotoxic kidney injury and is not significantly affected by chronic kidney disease or urinary tract infections.Tubular Enzymes:Measurement of tubular enzymuria is inexpensive and easy to measure.Cystatin C:Serum cystatin C increased by more than 50% at 0.6 days earlier than the increase in serum creatinine, but it’s not highly specific for renal injury.
It offers high volume ultrafiltration using replacement fluid
CVVHDs are new modifications of continuous replacement therapy, most useful in patients who are haemodynamically compromised. They offer a smooth way of instituting dialysis treatment where conventional dialysis is difficult to perform
This mode is used where large amounts of fluid are removed and replaced per hour, as a means of ‘cleaning’ the plasma, for example to remove inflammatory cytokines
CAVHD was developed to augment the solute clearances obtainable with continuous arteriovenoushaemofiltration (CAVH). Although CAVH provides excellent volume control, solute clearances are frequently insufficient to provide satisfactory control of azotemia, particularly in hypercatabolic patients.
