CRRT Basics

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Caitlyn Stough

The Pre-brief

Continuous Renal Replacement Therapy (CRRT) is a treatment option for patients in need of dialysis or fluid removal. It is typically only utilized in the ICU setting and patients require this particular therapy because of their hemodynamic instability. CRRT is a much slower type of dialysis than regular HD, as it pulls fluid or cleans the blood continuously, 24 hours a day, rather than over a 2-4 hr treatment. Some facilities only use this treatment option in ICU patients with renal failure, even if they are hemodynamically stable. This type of therapy relies on the bedside nurse, who has special training in this technology and the equipment. It requires you to be aware of how the patient responds to the treatment both metabolically and hemodynamically at all times.

Indications

  • Volume Overload
  • Electrolyte Imbalances
    • Hyperkalemia
    • Hyperphosphatemia
    • Hyponatremia
  • Metabolic acidosis
  • Worsening or persistent AKI
  • Pericarditis
  • Drug and toxin removal/encephalopathy
  • Uremia or Azotemia

There are three general types of CRRT

  • Continuous Veno-Venous Hemofiltration (removal of large molecules)
  • Continuous Veno-Venous Hemodialysis (removes fluid via diffusion with dialysate)
  • Continuous Veno-Venous Hemodiafiltration (combo of solute and fluid removal)

 In general, they all achieve a similar outcome, but each treatment option is geared towards a specific treatment. But today we are delving into what I use, CVVHD!

Starting Treatment

So, the nephrologist placed orders for CRRT; what will you need? First things first, access needs to be established. The patient will need a double lumen dialysis catheter.

Fistulas are common for established dialysis patients but cannot be used with CRRT. This is because it is pump-driven and incorporates venovenous extracorporeal circuits. There is a red and a blue line, but it will both be venous and should never be arterial. Once the line is established, it needs to be anticoagulated as soon as it is inserted. The amount of required heparin will be labeled on each port hub. CRRT machine orders will be given by the nephrologist and can be adjusted during the treatment. Patients will either run with a positive, negative, even, or zero fluid balance. Blood flow rate can be adjusted to help prevent clotting, and dialysate rate is usually calculated depending on patient weight and electrolytes. Lab orders and ABGs are followed based on physician preference, patient condition, and/or for any acute change. 

Complications

Clotting is the #1 complication during CRRT, whether it is the circuit clotting or the line itself clotting off. Circuit clotting needs to be closely monitored for and anticipated during the treatment. The bedside nurse should always have saline flushes and heparin (or the anticoagulant ordered) within reach if the machine decides to clot off and stop cycling the blood. If the  machine stops  cycling and appears to be trying to clot, the patient’s blood should be returned and therapy discontinued with the current circuit. Each circuit can hold approximately 150-250 mL blood, which can add up, especially if circuits are replaced 2-3 times a shift.

Other complications the nurse should be aware of and aim to prevent include but are not limited to, infections, bleeding, hypotension, electrolyte imbalances, All of these complications need to be monitored closely and the bedside nurse should utilize the multiple services consulted for the patient for optimal prevention and treatment. Depending on the institution, infectious disease, Heme/Onc and GI/GU may be following the patient as well as Critical Care and Nephrology. 

Clotting Issues

Utilize the OneView graph screen and watch for the pressure trends. The graph should remain almost “flatline” with slight variation. If the chart starts to spike at all, there is some occlusion occurring.

The above pictures depict a machine running within normal limits on the left (green bar at the top), and a clotted machine with high venous pressures on the right (red bar at the top). Depending on the alarm and the numbers, the machine will tell you whether it is a push (blue), pull (red) or something within the circuit or a line is kinked/clamped. If a clot is suspected, there is an option to flush the filter to determine the extent or location of the clot and whether or not the blood can be safely returned to the patient.

The Debrief

  • First things first, always check and verify the machine’s orders, pre-filter (if ordered), and the dialysate bags used for the current therapy. 
  • Check the line and tubing for kinks and clamps, as well as any air or forming clots. 
  • When in doubt of the circuit clotting, rinse back. If the patient is getting more hypotensive or unstable, stop treatment and rinse back. 
  • The arterial (red) line PULLS patient blood, and venous (blue) line PUSHES filtered blood back to the patient. 
  • Never push air back to the patient. 
  • Troubleshoot any red alarms- mute alarm first, information, stop treatment. The information book/“I” in the app bar will walk through the steps or possible interventions needed to get the system back up and running and should always be utilized! 

References

  1. Baldwin I, Fealy N. Clinical nursing for the application of continuous renal replacement therapy in the intensive care unit. Semin Dial. 2009 Mar-Apr;22(2):189-93. DOI: 10.1111/j.1525-139X.2008.00547.x. PMID: 19426427.
  2. Detecting filter clogging / clotting [Video file]. (2020). Retrieved March 21, 2021, from https://www.nxstage.com/hcp/training-resources/detecting-filter-clogging-clotting/

  3. Tandukar, S., & Palevsky, P. M. (2019). Continuous Renal Replacement Therapy: Who, When, Why, and How. Chest155(3), 626–638. https://doi.org/10.1016/j.chest.2018.09.004

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