Intensive Care Nursing/Continuous Renal Replacement Therapy

Indications

Indications for CRRT mirror reasons for a patient needing dialysis in the setting of an acutely ill hemodynamically unstable patient. Reasons may include: electrolyte dysregulation/disruption, imbalance of acid/base of renal origin (metabolic acidosis/metabolic alkalosis), inability for renal-filtration (removal of waste), maintenance of fluid balance, etc. Primarily these indications mirror failure of the various functions of the kidney.

Modes

Some modes CRRT devices are operated in are: Slow Continuous Ultra-Filtration (SCUF), Slow Extended Daily Dialysis (SLEDD) – may also be known as Prolonged Intermittent Renal Replacement Therapy (PIRRT), Continuous Veno-Venous Hemofiltration (CVVH), Continuous Veno-Venous Hemodialysis (CVVHD), Continuous Veno-Venous Hemodiafiltration (CVVHDF).

Practice

Vascular Access

Vascular access is typically obtained with an indwelling catheter as the fistulas/grafts typically utilized in hemodialysis are not able to be utilized for the purpose of 24-hour CRRT. On account of this in conjunction of large volume of blood volume replacement, central venous access is necessary. This can be done with either a dual lumen Central Venous Catheter (CVC) or a tunneled dual lumen CVC. Due to blood volume needed to circulate in a continuous manner, a dual lumen central venous catheter is typically utilized (e.g. femoral, internal jugular, subclavian vein access). These central venous accesses may be present or may be temporarily placed emergently. Some devices have a third lumen on the catheter to allow for additional central venous access as well. On account of the larger volumes of blood flow needed for CRRT to be effective these dual lumen CVCs have larger inner lumens than traditional CVCs utilized for infusions.

Device

Devices may slightly vary but rely on the same basic principles. Typically, there are two different circuits: blood and fluid. The blood circuit begins with an access where blood arrives to the machine, passage through a filter (colloquially known as the “artificial kidney”), and a return side where the cleaned blood returns to the patient’s body. The fluid circuit includes dialysate which passes alongside the filter, and the effluent side after waste material is removed. Alterations in device mode can alter pre/post fluid to dilute blood, and can alter direction of dialysate fluid based on patient needs.

In an effort to keep fluid status measurable in the compromised patient, devices may be volumetric or weight based to accurately measure volume of fluid removed and/or cycled through device.

Troubleshooting

As with all devices, ensure patient safety first. Many alarms noted are due to tubing clamped/occluded or dislodgement/disconnection. So, ensure circuits of blood/fluid have passage without kinks, obstructions, and all connections are intact. Follow manufacturer's recommendations for other troubleshooting tips specific for device.

Anticoagulation

Sometimes due to continued clotting of filter anticoagulation may be ordered. Depending on device, some have the ability to infuse directly at filter. When utilizing systemic anticoagulation and/or filter anticoagulation, the patient should be monitored for signs and symptoms of hemorrhage.

Assessments of the patient receiving CRRT

• Continuously monitor/observe vital signs: specific mention of those involving fluid status like blood pressure, heart rate, cardiac output, etc.
• Fluid Status: via intake and output (typically hourly).
• Mental status: as acid/base imbalance and uremia may cause mental status changes.
• Maintain tubing being free of kinks and occlusions while ensuring connections are maintained.
• Entry site of CVC: monitor position and insertion location for signs and symptoms of infection and to ensure the device has not become dislodged.