Renal Support in the Critically Ill

The second Renal Support in the Critically Ill Conference, hosted by The Alfred ICU, took place last week.

Here are the top 10 ‘take home messages’ from the conference:


1. Biomarkers
Biomarkers of structural kidney injury, such as Neutrophil gelatinase-associated lipocalin (NGAL), are becoming more widely available. Early measurement of these biomarkers predicts development of acute kidney injury (AKI) and associated adverse outcomes.


2. Renal recovery
Renal recovery from AKI is influenced by a number of factors; severity, duration, CKD status, and patient age and comorbidity. Data suggest that initial application of continuous renal replacement therapy (CRRT) – as compared to intermittent RRT (IRRT) – may improve the likelihood of complete recovery (e.g. free from chronic dialysis).

3. Fluids and renal perfusion pressure
IV fluids do not lead to a sustained increase in renal blood flow (RBF) and do not increase renal perfusion pressure in large animal models of sepsis. Their use in response to oliguria may lead to a positive fluid balance, which has been associated with adverse outcomes in the critically ill. Use of vasopressors to improve perfusion pressure (in reference to the patient’s baseline blood pressure) may prove a more optimal approach.

4. Drug pharmacokinetics
Drug pharmacokinetics are significantly altered in critically ill patients, in part due to alterations in renal clearance associated with AKI. Application of CRRT further complicates this process, such that therapeutic drug monitoring offers the best method of optimizing drug exposure.

5. Citrate anticoagulation for RRT
Citrate offers an attractive alternative to heparin for circuit anticoagulation, and appears to prolong filter lifespan. Caution remains when applying this therapy in patients with hepatic failure.

6. Loop diuretics
Data on loop diuretic therapy in patients with AKI remains conflicted. These agents remain a consideration in the management of fluid overload, and the lack of an adequate diuresis in response to loop diuretics, may serve as a useful trigger to commence RRT.

7. Septic AKI
Animal data suggests there is neither a significant deterioration in RBF, nor any significant structural abnormality in models of septic AKI. The noteworthy disparity between functional and structural characteristics in this setting suggests an otherwise unknown mechanism.

8. Synthetic colloids and Saline
Hydroxyethyl starch (HES) is clearly associated with AKI, while there is very little data on the safety of other synthetic colloids in the critically ill. Chloride rich solutions (0.9% saline) cause a reduction in RBF in animal models, and renal cortical perfusion in healthy volunteers. Decreasing chloride administration may decrease renal dysfunction.

9. Initiation of RRT
Initiation of RRT in ICU is a complex process, such that there is a poor understanding of the standard of care delivered across centers. Earlier initiation of RRT may have clinical benefits, although the quality of existing data is poor.

10. ECMO and renal failure
Extracorporeal membrane oxygenation (ECMO) initiated after renal failure is associated with reduced survival. RRT can be safely provided in such patients by accessing the ECMO circuit.

 

4 comments to “Renal Support in the Critically Ill”
  1. Does the Alfred routinely use citrate for circuit AC?

    There’s definitely institutional (and departmental!) variation in practice, but I think we’ve pretty much stopped using any anticoagulation for our CRRT pumps.

    The problem with citrate is that I’m pretty sure with as much CRRT as we do at the STC we depleted the entire Eastern US’ supply of calcium gluconate after 6 months, put it on a national shortage…

  2. Alfred have Gambro PrismaFlex machines, which can run citrate with the filtrate replacement fluid. The Calcium algorithm is tied to this, and rather automated. We haven’t had any trouble with shortages of Calcium.

    Citrate is used only about 15-20% of the time, but it’s use is increasing annually.
    Our filter life is well tracked electronically, and certainly when we use “no anticoagulation” our filter life is shorter, but sometimes that is what we must do.
    Heparin is still commonly used, although our CRRT algorithm is different to our full anticoagulation protocol- somewhat lower APTTs are used for example.

    Watch this space, it looks as Citrate becomes safer and easier it is being used more and more. As we have found, the ease of use and familiarity is very important in getting acceptance in practice. We have just published our own RCT on Citrate against Heparin:

    Brain MJ, Roodenburg OS, Adams N, McCracken P, Hockings L, Musgrave S, Butt W, Scheinkestel C. Randomised trial of software algorithm driven regional citrate anticoagulation versus heparin in continuous renal replacement therapy: the Filter Life in Renal Replacement Therapy pilot trial. Crit Care Resusc. 2014 Jun;16(2):131-7. PubMed PMID: 24888284 (journal article link)

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