Study of Renal Resistive Index to Assess Postoperative Development of Acute Kidney Injury in Patients Undergoing Off Pump CABG.

Aim:

TO STUDY PREDICTIVE VALUEOF RENAL RESISTIVE INDEX FOR DEVELOPMENT OF  POSTOPERATIVE ACUTE KIDNEY INJURY IN PATIENTS UNDERGOING OFF PUMP CABG

 Objectives:

Primary objective :

a)    To document the change in RRI following coronary  anastomosis in off pump CABG

b)   To determine predict value of RRI for development ofpostoperative AKI

Secondary objective

1.    To document the change in RRI and CVP followingcoronary  anastomosis in off pump CABGand   determine their combined value topredict development of postoperative AKI

2.    To correlate the changes in RRI during position of theheart for circumflex (lateral) and PDA (inferior) anastomosis in off pump CABGwith changes cardiac output, cardiac index, mean arterial pressure and CVP

 StudyMethodology :

TEEprobe is routinely inserted after induction of anaesthesia .  We  usethe TEE probe to scan the kidney and measure the renal resistive index in theleft kidney.

The TEE probe is advancedapproximately 30 cm from the upper incisor teeth, and a standard midesophageal4-chamber view is obtained. Starting from the 4-chamber view, the probe isadvanced a further 8 to 10 cm to lead it through the short abdominal part ofthe oesophagus eventually into the stomach and anteflexed to obtain amidpapillary transgastric short-axis (TG SAX) view.

STEP 1:  TG SAX view is obtained . •

STEP 2: The probe   is rotated 90 to 270 degrees toward the LEFTuntil the SAX view of the   descendingaorta is imaged. The aorta lies  anterior to the oval hypoechogenic vertebral body

STEP 3: The probe is advanced 4–6 cm followingthe aorta to the origin of the left renal artery Colour flow doppler isused  to image the blood flow in leftrenal vessels.

STEP 4 : Pulse wave doppler is used to measurethe RRI as follows :

   Useof ionotropes , fluids or vasodilators to maintain haemodynamic stability ismanaged by the concerned anaesthesiologists. After steadying of hemodynamicchanges due to positioning and stabilization of the heart with octopus foranastomosis of obtuse marginal (OM) and posterior descending artery (PDA), changein the left kidney RRI are noted. Final left RRI is  recorded after protamine reversal of heparin.

Systemichemodynamic changes are manifested in both the kidneys .As left kidney is easyto scan we measure only left RRI.

TEE guided Left Renal Resistive Index (RRI) will be  measured as follows

a.    Baseline T0:measured after induction and steady state haemodynamics for 5 mins

b.    During anastomosisof OM -T1

c.    During anastomosisof PDA-T2

d.    After reversal ofheparin with protamine .-T3

AKIwill be  diagnosed using criteria proposed by AcuteKidney Injury Network (AKIN) as  an abrupt (within 48 h)absolute increase in the serum creatinine concentration of ≥0.3 mg/dL frombaseline, a percentage increase in serum creatinine of ≥50%, or oliguria ofless than 0.5 mL/kg/hr for more than 6 h14 AKI will be  defined using the AKIN criteria by comparingthe highest serum creatinine within 48 h after surgery with preoperative serumcreatinine

 Recovery from AKI will bedefined as a 50 percent decrease in serum creatine or return of serum creatineto its baseline value.

 .

Patients who meet theAKIN criteria for AKI are classified as “AKIâ€, whereas those who do not are  classified as “no AKIâ€.

For analysis study population will be groupedas follows

1.     NoAKI

2.     TransientAKI:

TransientAKI will be defined as recovery from AKI within 3 days after surgery.Persistent AKI : will be defined as persistent elevation of serum creatine   after 3 days.

 IntraoperativeParameters recorded will be

1.    Left RRI

2.    Cardiac output andcardiac index as measured by flowtrac

3.    Mean arterialpressure (MAP)

4.    CVP

Post operativeparameters recorded will be

Sr creatineand   Urine out put :for 3 days if no AKI; or till 5 days if AKI develops.

 Statistical analysis

Results will be expressedas median with range,  number withproportion (%), percentage with standard deviation as appropriate.Pearson’s  test will be used to study thecorrelations. A receiver-operating characteristic curve (ROC) will be generatedfor RRI in each AKI group to test the significance of RRI as a diagnostic tool.