Validation of Transesophageal Echocardiography (TEE) to Measure Renal Resistive Index and to Predict Renal Injury
Status: | Withdrawn |
---|---|
Conditions: | Renal Impairment / Chronic Kidney Disease |
Therapuetic Areas: | Nephrology / Urology |
Healthy: | No |
Age Range: | 18 - 89 |
Updated: | 4/21/2016 |
Start Date: | May 2010 |
End Date: | June 2011 |
Validation of Transesophageal Echocardiography With to Measure Renal Resistive Index and to Predict Acute Kidney Injury
The study doctors are trying to determine if the TEE measurements from your stomach are
helpful in measuring the blood flow to the kidneys.
helpful in measuring the blood flow to the kidneys.
The significant morbidity and mortality associated with acute kidney injury in critical care
patients and after cardiac surgery is well-known. Studies have demonstrated between 1 to 30%
postoperative mortality, and even higher rates of up to 70% when patients develop kidney
failure and require dialysis. Even small increases in creatinine between 0 to 0.5 mg/dl can
result in a greater than two-fold rise in 30-day mortality. Despite efforts to improve
outcome, there has been no proven effective pharmacological interventions to treat acute
kidney failure. Most recommendations are aimed at prevention by identifying high-risk
patients, avoiding nephrotoxic drugs and minimizing intraoperative hypotensive insults.
There are few studies that have assessed renal blood flow using transesophageal
echocardiography (TEE). Yang et al. examined the left renal artery of 60 patients using TEE
during cardiac surgery and evaluated the feasibility of using TEE as a method to measure
renal blood flow intraoperatively. Although they were only able to include 60% of the
subjects due to technical difficulties, they did demonstrate less than 10% variability
between measurements and therefore good reproducibility using TEE.
Renal blood flow may not be the best method to predict sufficient renal perfusion. Renal
autoregulation is not preserved under general anesthesia even with the maintenance of
adequate mean arterial blood pressure and cardiac output. Renal blood flow is further
worsened by hemodilution and hypothermia. In addition, due to its pulsatile nature, the
diameters of the renal arteries vary during the cardiac cycle and are a source of
calculation error when determining renal blood flow as a function of renal blood velocity
and arterial diameter.
Renal resistive index (RI) is a measure of intrarenal hemodynamics that is calculated using
the blood flow velocities of segmental or intrarenal vessels and correlates with renal blood
flow and renovascular resistance. The renal artery is not used because the flow varies and
is inconsistent between systole and diastole. RI becomes elevated in pathological conditions
and is associated with increasing creatinine, renal injury and dysfunction. As blood flow
and creatinine clearance decrease through the renal vasculature, the resistive index
increases. Resistive index may be a better gauge of renal dysfunction rather than renal
blood flow because it is easier to assess and less dependent on obtaining a Doppler beam
view that is oriented perfectly parallel to the blood flow. Because RI is a ratio of the
renal blood flow velocities [RI = (peak systolic velocity - peak end diastolic
velocity)/peak systolic velocity], the margin of error created by non-parallel Doppler beams
cancels out.
Traditionally, resistive index is obtained by transabdominal Doppler ultrasonography (USG)
although there have been transesophageal studies that have used RI as a secondary endpoint
when examining renal blood flow. There is currently no technique that routinely uses TEE to
intraoperatively monitor resistive index as a determination of adequate renal blood
perfusion and an indication of renal compromise.
patients and after cardiac surgery is well-known. Studies have demonstrated between 1 to 30%
postoperative mortality, and even higher rates of up to 70% when patients develop kidney
failure and require dialysis. Even small increases in creatinine between 0 to 0.5 mg/dl can
result in a greater than two-fold rise in 30-day mortality. Despite efforts to improve
outcome, there has been no proven effective pharmacological interventions to treat acute
kidney failure. Most recommendations are aimed at prevention by identifying high-risk
patients, avoiding nephrotoxic drugs and minimizing intraoperative hypotensive insults.
There are few studies that have assessed renal blood flow using transesophageal
echocardiography (TEE). Yang et al. examined the left renal artery of 60 patients using TEE
during cardiac surgery and evaluated the feasibility of using TEE as a method to measure
renal blood flow intraoperatively. Although they were only able to include 60% of the
subjects due to technical difficulties, they did demonstrate less than 10% variability
between measurements and therefore good reproducibility using TEE.
Renal blood flow may not be the best method to predict sufficient renal perfusion. Renal
autoregulation is not preserved under general anesthesia even with the maintenance of
adequate mean arterial blood pressure and cardiac output. Renal blood flow is further
worsened by hemodilution and hypothermia. In addition, due to its pulsatile nature, the
diameters of the renal arteries vary during the cardiac cycle and are a source of
calculation error when determining renal blood flow as a function of renal blood velocity
and arterial diameter.
Renal resistive index (RI) is a measure of intrarenal hemodynamics that is calculated using
the blood flow velocities of segmental or intrarenal vessels and correlates with renal blood
flow and renovascular resistance. The renal artery is not used because the flow varies and
is inconsistent between systole and diastole. RI becomes elevated in pathological conditions
and is associated with increasing creatinine, renal injury and dysfunction. As blood flow
and creatinine clearance decrease through the renal vasculature, the resistive index
increases. Resistive index may be a better gauge of renal dysfunction rather than renal
blood flow because it is easier to assess and less dependent on obtaining a Doppler beam
view that is oriented perfectly parallel to the blood flow. Because RI is a ratio of the
renal blood flow velocities [RI = (peak systolic velocity - peak end diastolic
velocity)/peak systolic velocity], the margin of error created by non-parallel Doppler beams
cancels out.
Traditionally, resistive index is obtained by transabdominal Doppler ultrasonography (USG)
although there have been transesophageal studies that have used RI as a secondary endpoint
when examining renal blood flow. There is currently no technique that routinely uses TEE to
intraoperatively monitor resistive index as a determination of adequate renal blood
perfusion and an indication of renal compromise.
Inclusion Criteria:
- Subjects with use of TEE as part of anesthetic plan as clinically determined by
anesthesiologist
- Subjects with no contraindications to use of TEE or transabdominal doppler
ultrasonography
Exclusion Criteria:
- Patients on hemodialysis/peritoneal dialysis
- Patients with a contraindication to use of TEE i.e.esophageal stricture, esophageal
diverticulum, esophageal/gastric tumor, recent esophageal/gastric surgery or
radiation to the chest
- Patients with a contraindication to use of transabdominal doppler ultrasonography
- Patients who are pregnant
- patients with esophageal varices
- Patient with bleeding disorders
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