CRRT: What You Need to Know for Patient Care

Continuous renal replacement therapy (CRRT) is a lifesaving procedure that requires a high level of skill, well established procedures and a multidisciplinary approach for safe execution. Here are 6 things you need to know if you provide care to patients receiving CRRT.

What is CRRT?

CRRT is a continuous form of dialysis indicated for patients with acute kidney injury. Intermittent hemodialysis and CRRT both work by removing a portion of patients’ blood from the body, running it across semipermeable filters to remove toxins (like urea) and returning it to the patient.

Both procedures use a dialysate fluid which runs in the opposite direction to blood flow. This creates a diffusion gradient across the semipermeable filters allowing extraction of toxins into the dialysate fluid which is collected as waste.

Dialysate fluid mimics the natural composition of plasma. It contains purified water, electrolytes and dextrose.

When is CRRT Preferred?

The blood flow rate in intermittent dialysis is as high as 300-500ml/min. CRRT flow rates are 150-250ml/min.

The lower flow rate results in softer fluctuations in blood pressure.

CCRT is also the preferred form on dialysis when a patient is fluid overloaded particularly with cerebral edema where rapid correction of systemic volume will worsen outcomes.

Because CRRT is running 24/7 it means that all other aspects of your patient’s care will be affected. Ideally, there will be stringent policies and procedures established for the use of CRRT at your facility but quite honestly that is not always the case.

Where’s what you need to know to advocate for safe patient care. Let’s start with medications and CRRT.

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CRRT: Medication Dosing & Administration

Be sure that all your medications have been reviewed by pharmacy for accurate dosing in patients receiving CRRT.

Even with all these considerations dosing is not a one and done deal. It has to be reevaluated as the patient’s clinical condition improves or worsens.

Antibiotics require significant consideration of the organism being targeted and the sensitivity of the organism to the drug. Both overdosing and under-dosing are potential risks with CRRT.

Sedatives, analgesics, vasopressors and anticonvulsants will all be affected by the use of CRRT. In some cases, you will note higher doses than usual and in some cases a dose reduction will be required.

In short, run all medication changes by your pharmacist.

CRRT: Associated Risks to Monitor

There are significant risks associated with CRRT. You need to know what to look out for while providing patient care.

1.Clotting

Clotted filters and tubing are the number one reason for interruptions in CRRT. The most common cause being inadequate anticoagulation.

The coagulation cascade will be activated any time blood contacts foreign objects including the tubing and filters of the dialysis machine. Therefore, an anticoagulant either heparin or calcium citrate must be used during this process.

Here’s what you do:

Monitor for visible clot formation, which is most common during initiation of CRRT at the point of venous access, in the tubing and at the filter.

2. Bleeding

Anytime anticoagulation is used there is an increased risk of bleeding. For CRRT either heparin or calcium citrate will be used as anticoagulant. While heparin does have a higher risk of bleed relative to calcium citrate, using citrate has its own risk like hypocalcemia and electrolyte disturbances that can be significant in a patient who is already critically ill.

There are also patient specific risk factors like thrombocytopenia that increases the risk of bleed.

Here’s what you do:

Monitor lab values like hemoglobin, hematocrit, platelets, apTT for heparin and any visible signs of bleeding.

3. Temperature

Hypothermia can occur in up to 50% of patients receiving CRRT.

Body temperature is strictly regulated at around 98.6 F. During CRRT, blood is being removed from the body, ran through a machine at room temperature and returned to the body, all of which drops the temperature of blood.

In a patient who is already very sick hypothermia can have significant medical impact. It increases oxygen requirements, causes arrythmias, ischemia, clotting dysfunction and much more.

Here’s what you do:

Most protocols recommend hourly checks of temperature and continuous monitoring if temperature drops below normal. There are blood warming devices that can be used with CRRT machines. These will warm up the patient’s blood before it is returned to the body.

External warming with blankets, warming blankets, heating pads can also be used to raise the core temperature.

4. Electrolytes

All forms of dialysis are associated with electrolyte disturbances.

The kidneys play a central role in maintaining electrolyte balance. The use of dialysate fluid that mimics the physiological concentrations of electrolytes attempts to compensate for this function. However, dialysate fluid is not dynamic in response to physiological changes.

This places the patient at risk for both supra and sub physiological levels of electrolytes with consequences ranging from cardiac and muscle dysfunction, cerebral edema and neurological dysfunction.

The selection of dialysate fluid plays a major role in minimizing the occurrence of electrolyte disturbances. This is one of the complexities that requires a highly trained team to prescribe optimal fluids on a patient specific basis. It requires correlation between the formulation of the dialysate, the patient’s baseline electrolyte status and choice of anticoagulant.

What you should do:

All CRRT patients should have their electrolytes monitored at least every 12hrs. This includes sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonates.

5. Blood Pressure

The major advantage of CRRT is the hemodynamic stability offered by the slow rate of filtration. However, hypotension is still a very real concern. This should be continually monitored in the critical care setting where CRRT will be performed.

I hope this provides you with a solid foundation to advocate for yourself and your patients receiving CRRT. While we all cannot be experts in CRRT as a requirement for patient care, knowing what questions to ask and what to monitor as the bedside provider of care can save lives.

The National Kidney Foundation offers a deep dive into the complexities of CRRT.

The information on this website is intended to be used solely for educational and informational purposes. While the content may be about specific medical and health care issues, it is not a substitute for or replacement of personalized medical advice and is not intended to be used as the sole basis for making individualized medical or health-related decisions.