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Measurement of kidney perfusion in critically ill patients.

Schneider AG, Goodwin MD, Bellomo R - Crit Care (2013)

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Acute kidney injury (AKI) is a major complication of critical illness occurring in 30 to 40% of all critically ill patients and in its severe form requires renal replacement therapy (RRT), in approximately 5% of patients... Since the early description of an "acute uremia syndrome" in crush injury victims during World War II and its association with histopathological findings similar to those found in experimental renal artery ligation, ischemia or some form of alteration in renal blood flow has been thought to play a pivotal role in the pathogenesis of AKI... It delivers slightly lower values as compared with standard inulin clearance but is easier to prepare and more readily available... However, the results generated by the so-called Gates methods have not been shown to be superior to creatinine-based formulas... More importantly, its use in critically ill patients is likely to be very limited even for research purposes... Indeed, PET protocols are long and require extensive mobilization, which, in unstable patients is often labor intensive and can be associated with safety hazards... Newer contrast agents based on ultra-small particles of iron oxide (USPIO) molecules have been presented and seem to be safe and potentially useful for renal blood flow measurement... However, their safety profile is not yet fully established and their clinical role is still to be established, in particular since other MRI techniques, which do not need intravenous contrast agents, are now available... To the best of our knowledge, this study was the first to measure global renal blood flow noninvasively in critically ill patients with sepsis associated AKI... This study provided a clear demonstration that, in septic critically ill patients with AKI, renal blood flow can range from low to supranormal and confirmed what animal studies had long suggested: Septic AKI is not a uniform disease and is not reliably associated with decreased renal blood flow (so-called ischemia)... Ureteric obstruction also significantly affects measurement of RI... The RI alone is, therefore, easily confounding... These agents demonstrate increased stability and have uniform sizes... Microbubbles found in commercial preparations of ultrasound contrast agents (UCA) have very uniform sizes about that of a red blood cell... Assessment of renal blood flow is important but difficult in AKI.

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Example of microcirculatory changes as seen with contrast-enhanced ultrasound images taken during a contrast-enhanced ultrasound study performed on a patient with chronic liver disease and hepatorenal syndrome. The image is centered on the patient's right kidney. Two images are shown: the first (a) was taken just before the intravenous administration of 1 mg of terlipressin and the second (b) 2 hours after. This study demonstrates increased renal perfusion in response to terlipressin administration, as indicated by a brighter signal within the renal cortex on the right image.
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Figure 4: Example of microcirculatory changes as seen with contrast-enhanced ultrasound images taken during a contrast-enhanced ultrasound study performed on a patient with chronic liver disease and hepatorenal syndrome. The image is centered on the patient's right kidney. Two images are shown: the first (a) was taken just before the intravenous administration of 1 mg of terlipressin and the second (b) 2 hours after. This study demonstrates increased renal perfusion in response to terlipressin administration, as indicated by a brighter signal within the renal cortex on the right image.

Mentions: Blood flow quantification using contrast-enhanced ultrasound was first described by Wei et al. [70] in a canine model. The same technique was used by Kishimoto et al. to measure renal blood flow, demonstrating a good correlation with changes in renal blood flow as estimated by PAH clearance [71]. Schwenger [72] and Benozzi [73] et al. demonstrated that contrast-enhanced ultrasound was able to distinguish acute rejection from acute tubular necrosis. Another study, in healthy volunteers demonstrated that contrast-enhanced ultrasound was able to detect a 20% decrease in renal blood flow as induced by an angiotensin II infusion [74]. Above all, contrast-enhanced ultrasound can provide real time visualization of the renal microcirculation. Because it is very well tolerated and can be applied at the bedside, it could in theory be used to determine changes in microcirculation after therapeutic interventions. This would enable us to better understand the intra-renal microcirculatory changes following our common interventions and potentially drive our practice in patients at risk of AKI. As an example, as illustrated in Figure 4, contrast-enhanced ultrasound was able to confirm a strong microcirculatory response to terlipressin in a patient with hepatorenal syndrome.


Measurement of kidney perfusion in critically ill patients.

Schneider AG, Goodwin MD, Bellomo R - Crit Care (2013)

Example of microcirculatory changes as seen with contrast-enhanced ultrasound images taken during a contrast-enhanced ultrasound study performed on a patient with chronic liver disease and hepatorenal syndrome. The image is centered on the patient's right kidney. Two images are shown: the first (a) was taken just before the intravenous administration of 1 mg of terlipressin and the second (b) 2 hours after. This study demonstrates increased renal perfusion in response to terlipressin administration, as indicated by a brighter signal within the renal cortex on the right image.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672528&req=5

Figure 4: Example of microcirculatory changes as seen with contrast-enhanced ultrasound images taken during a contrast-enhanced ultrasound study performed on a patient with chronic liver disease and hepatorenal syndrome. The image is centered on the patient's right kidney. Two images are shown: the first (a) was taken just before the intravenous administration of 1 mg of terlipressin and the second (b) 2 hours after. This study demonstrates increased renal perfusion in response to terlipressin administration, as indicated by a brighter signal within the renal cortex on the right image.
Mentions: Blood flow quantification using contrast-enhanced ultrasound was first described by Wei et al. [70] in a canine model. The same technique was used by Kishimoto et al. to measure renal blood flow, demonstrating a good correlation with changes in renal blood flow as estimated by PAH clearance [71]. Schwenger [72] and Benozzi [73] et al. demonstrated that contrast-enhanced ultrasound was able to distinguish acute rejection from acute tubular necrosis. Another study, in healthy volunteers demonstrated that contrast-enhanced ultrasound was able to detect a 20% decrease in renal blood flow as induced by an angiotensin II infusion [74]. Above all, contrast-enhanced ultrasound can provide real time visualization of the renal microcirculation. Because it is very well tolerated and can be applied at the bedside, it could in theory be used to determine changes in microcirculation after therapeutic interventions. This would enable us to better understand the intra-renal microcirculatory changes following our common interventions and potentially drive our practice in patients at risk of AKI. As an example, as illustrated in Figure 4, contrast-enhanced ultrasound was able to confirm a strong microcirculatory response to terlipressin in a patient with hepatorenal syndrome.

View Article: PubMed Central - HTML - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Acute kidney injury (AKI) is a major complication of critical illness occurring in 30 to 40% of all critically ill patients and in its severe form requires renal replacement therapy (RRT), in approximately 5% of patients... Since the early description of an "acute uremia syndrome" in crush injury victims during World War II and its association with histopathological findings similar to those found in experimental renal artery ligation, ischemia or some form of alteration in renal blood flow has been thought to play a pivotal role in the pathogenesis of AKI... It delivers slightly lower values as compared with standard inulin clearance but is easier to prepare and more readily available... However, the results generated by the so-called Gates methods have not been shown to be superior to creatinine-based formulas... More importantly, its use in critically ill patients is likely to be very limited even for research purposes... Indeed, PET protocols are long and require extensive mobilization, which, in unstable patients is often labor intensive and can be associated with safety hazards... Newer contrast agents based on ultra-small particles of iron oxide (USPIO) molecules have been presented and seem to be safe and potentially useful for renal blood flow measurement... However, their safety profile is not yet fully established and their clinical role is still to be established, in particular since other MRI techniques, which do not need intravenous contrast agents, are now available... To the best of our knowledge, this study was the first to measure global renal blood flow noninvasively in critically ill patients with sepsis associated AKI... This study provided a clear demonstration that, in septic critically ill patients with AKI, renal blood flow can range from low to supranormal and confirmed what animal studies had long suggested: Septic AKI is not a uniform disease and is not reliably associated with decreased renal blood flow (so-called ischemia)... Ureteric obstruction also significantly affects measurement of RI... The RI alone is, therefore, easily confounding... These agents demonstrate increased stability and have uniform sizes... Microbubbles found in commercial preparations of ultrasound contrast agents (UCA) have very uniform sizes about that of a red blood cell... Assessment of renal blood flow is important but difficult in AKI.

Show MeSH
Related in: MedlinePlus