Renal Resuscitation using Renal Interlobar Artery Doppler (RIAD)

Shocked patient…. check! Adequate volume resuscitation…. check!  Vasopressors.… check! Mean arterial pressure (MAP) > 65 mmHg….. check!  Adequate urine output…. Wait, why isn’t my patient making urine?

As we begin to understand more about shock, hemodynamics, and the importance of perfusion over the usual macrocirculatory goals (MAP > 65), finding ways to assess regional blood flow is critical.  A recent study examined the effect of fluid administration on renal perfusion using renal interlobar artery Doppler (RIAD) to assess the interlobar resistive index (RI).  See how to perform a RIAD here.

They also recorded the fluid challenge’s effect on the traditional hemodynamic measurements of MAP and pulse pressure (PP) then observed the patient’s urine output (as a clinical marker of perfusion).  The authors reported 3 key findings:
 

1. In the hemodynamically impaired patient, a fluid challenge results in reduced intrarenal vasoconstriction (a reduction in the RI).
2. In the hemodynamically impaired patient, changes in RI are more effective than changes in MAP or PP in predicting an increase in urine output after a fluid challenge.
3. Using RI to guide fluid therapy may be limited by small changes and technical limitations.

 

Bottom Line: The use of ultrasound to determine intrarenal hemodynamics is an interesting strategy to guide renal resuscitation in the shocked patient.  There is mixed data on the use of RIAD, however this study could explain the findings of SEPSISPAM and also addresses the growing concern that traditional hemodynamic goals may be inadequate resuscitation targets.

 

References

1. Moussa MD, Scolletta S, Fagnoul D, et al. Effects of fluid administration on renal perfusion in critically ill patients. Crit Care. 2015;19(1):250.
2. Asfar P, Meziani F, Hamel JF, et al. High versus low blood-pressure target in patients with septic shock. N Engl J Med. 2014;370(17):1583-93.

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