CRRT Pressures

Wake Forest Med Center has a note about pressures:

The Prisma measures pressures in several areas. It is very sensitive to changes in access pressures and return pressures. Therefore, if a patient is log rolled and the lines or catheter kink, the machine will stop and give an audible alarm. Most of the time this can be corrected by muting, identifying the problem and restarting the treatment.

This advice applies to every CRRT device (Prismaflex, Edwards, etc.) on the market, not just the Prisma, and presumably every dialysis system as well. Even a shift in position can change the pressure, moving the patient's bed up and down can increase or decrease the pressures. The access pressure alarm is most likely to be caused by patient position (lines or cather kinking, blocked, pinched, etc.), then the return pressure alarm. The effluent and filter pressure alarms are not directly influenced by patient position, but can trigger because of the access or return pressure being too high or low due to patient position.

While I believe change in position leading to pressure or kinking on the line or catheter is the most common cause of pressure alarms, additionally, the filter may be clotting, another line may be inadvertantly clamped (due to bag change or similar), or the access flow rate may be too high. More rarely a line could be leaking or the pressure transducer device or pod is failing or not calibrated correctly.

Depending on the pressure alarm, you may have to relieve the pressure by manually turning a pump backwards, consult the manual before doing so. It is important to note that while a pressure alarm is active, the blood pump is not moving, and clotting may occur in the tubing set or catheter if the problem is not fixed quickly (clotting can happen in as little as 5 minutes). Pressure alarms should be taken seriously and not ignored, every effort should be made to find and correct the problem before restarting the treatment, restarting blind and hoping the problem just goes away could lead to serious problems.

Nurse to Patient Ratio for CRRT

The nurse to patient ratio for a patient on continuous renal replacement therapy (CRRT) should be 1:1, don't let anyone tell you different. This is the ratio that I've seen the most, so hospitals are aware of the high demands CRRT patients and the device itself place on nursing. It is a complicated device and the patients require special attention, everything needs to be constantly monitored and updated. If your hospital's ratio is less than 1:1 then I would really look into it.

A Great ARF Summary Article

From icuroom.net, a great summary article for acute renal failure (ARF): Critical Care Nephrology: Acute Renal Failure in the Intensive Care Unit, Nephrology, Dec 2006. Of interest is this shortened description of CRRT:

CRRT includes a variety of modalities that use ultrafiltration and may use convection, diffusion, or both. Treatment is 24 hours per day with a blood flow of 100-200 ml/min, and a dialysate flow of 17-34 ml/min in the case of diffusive technologies. The advantages of CRRT stem from its continuous nature: both fluid and solutes shift more slowly, allowing for better hemodynamic stability and more precise solute concentrationcontrol. The gradual nature of solute removal in CRRT makes it less likely to cause cerebral edema.19 In addition, CRRT has greater cumulative solute removal than IHD due to the longer treatment time.

(although I've seen other blood and dialysate flow rates commonly used) And the reasons to use CRRT over intermittent hemodialysis (IHD):

Overall, these studies suggest a lack of survival improvement with CRRT versus IHD, with a possibility of improvement with CRRT in the most severely ill ARF patients. While studies have failed to show a survival advantage for any of the modalities, there are specific conditions where a particular RRT method is preferred over another. CRRT is recommended in patients with cerebral edema or liver failure, while IHD is more appropriate in patients with an increased risk of bleeding and life-threatening hyperkalemia.

Although a bit dated, the article is a great resource if you want an overview of ARF treatments, including CRRT.

New CRRT anticoagulation publication

In summary this pilot study shows an improvement in platelet count by using tirofiban (Aggrastat) and unfractionated heparin over just heparin to anti-coagulate CRRT patients.

Tirofiban preserves platelet loss during continuous renal replacement therapy in a randomised prospective open-blinded pilot-study

Andreas Link, Matthias Girndt, Simina Selejan, Ranja Rbah and Michael Bohm

Critical Care 2008, 12:R111

Abstract (provisional)

Introduction

Approximately one third of all patients with cardiogenic shock suffer from acute kidney injury. Percutaneous coronary intervention (PCI), intra-aortic balloon counterpulsation (IABP) and continuous renal replacement therapy (CRRT) require effective antiplatelet therapy and anticoagulation resulting in a high risk for platelet loss and bleeding events. The reversible platelet glycoprotein (GP) IIb/IIIa receptor inhibitor tirofiban was investigated to preserve platelet number and activation in a prospective open-blinded endpoint evaluation study.

Conclusions

This pilot study provides evidence that the use of tirofiban in addition to UFH prevents platelet loss and preserves platelet function in patients with cardiogenic shock and acute kidney injury requiring CRRT. The pathophysiological inhibition of platelet aggregation and platelet-monocyte interaction appears to be causally involved.

Link