Continuous renal replacement therapy (CRRT) is used to remove excess fluid from patients who are otherwise unable to hemodynamically tolerate higher removal rates, as in traditional intermittent hemodialysis (IHD). It allows for higher hemodynamic stability by avoiding rapid fluid shifts. It essentially does the work of the kidneys by filtering blood to remove fluid and waste products, such as creatinine. In my unit, we use the NxStage System One with NxView.
The first step is ALWAYS to confirm the medical provider's order to verify CRRT parameters and therapy fluid. In the order, you will find the prescribed blood flow rate (mL/minute), net fluid removal rate (NL) in mL per hour, and treatment (i.e., CVVH, CVVHD, CVVHDF, SCUF). The order looks similar to this:
Hourly Documentation and Calculation of Removal Rates
One of the challenges for nurses is calculating removal rates. Accurate and consistent CRRT charting is very important to avoid unsafe situations and inaccurate fluid removal. Let's break it down.
How to start charting a new CRRT document
Chart the initiation of CRRT at the ACTUAL TIME IT BEGAN. For example, if treatment is initiated at 0930, then you will document the initiation of CRRT as 0930. Note, you will not have the first pressure readings until the top of the next hour. That is, you will not document the following at the initiation of CRRT: Access/Arterial Pressure (AP), Return/Venous Pressure (VP), or Effluent Pressure (EP). You WILL, however, document the (A) Total Intake (mL) and (B) Total output (mL) using the past hour's I/O's (i.e., 0801-0900 in this example). Of course, you must first "infusion verify all" in the I/O tab of Flowsheets and update any other patient intake and output to obtain accurate totals. The total is found in the hourly table view of the Intake/Output tab. Documentation will look like this:
In this example, the patient had a total of 100 mL of intake and no output for the previous hour. The first value for (C) Prescribed Fluid Removal Rate (mL/hr) is a chosen volume that is within the NL range taken from the provider's order. It is the volume the nurse determines can be safely removed from the patient given their hemodynamic status. This step requires nursing judgment. It is generally good practice to start with a low volume and reassess your patient's hemodynamic status before increasing.
The Calculated Fluid Removal Rate (mL/hr) is obtained by the following equation: A-B+C. In this case, 100-0+50=150. The Actual Programmed Removal Rate (mL/hr) is the rate the nurse actually sets the CRRT machine to remove in one hour's time. In this example, the calculated rate is 150 mL/hr and the nurse sets the actual programmed removal rate to 150 mL/hr. This rate is adjusted on the machine in the yellow window (see image above).
What's next?
At the top of the next hour, which is 1000 in our example, the nurse documents the first AP, VP, and EP values listed on the treatment screen of the CRRT machine. Let's say the pressure values are -115, 179, and 159 respectively. Meanwhile, the Fluid Removed (mL) or ultrafiltration (UF) volume is 140 mL, which is the total fluid the CRRT machine was actually able to remove. Then, the documentation will look like this:
How do we calculate the prescribed fluid removal rate?
Since the calculated fluid removal rate was 150 mL for the first hour and the UF was 140 mL, there was a total of 10 mL not removed (150-140= 10 mL). We calculate the prescribed fluid removal rate by adding the volume not removed from the previous hour to the chosen NF loss volume for the next hour. Let's say the nurse uses nursing judgment to conclude that the patient is hemodynamically stable and able to tolerate a higher removal rate. Given that the NF loss in the provider's order above is 0-150 mL/hr, the nurse decides to remove 75 mL this next hour. So, the prescribed fluid removal rate is the 10 mL plus 75 mL. This gives us a prescribed fluid removal rate of 85 mL/hr.
How do we get the calculated fluid removal rate? Let's say that the I/Os for the 0901-1000 hour was again one-hundred for intake and zero for output because our patient is receiving continuous IV fluids, is NPO, and not urinating. When entering 100 for intake (A), 0 for output (B), and 85 for prescribed fluid removal rate (C), Epic calculates the fluid removal rate using equation A-B+C. In this case, the calculated fluid removal rate is 100-0+85=185 mL/hr. The nurse then programs the actual removal rate on the machine to 185 mL/hr for the next hour.
References:
NxStage: https://www.nxstage.com/hcp/products/the-nxstage-system-one-s-with-nxview/