Continous Renal Replacement Theraphy

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Continuous Renal Replacement Therapies are also a type of haemodialysis that were born out of frustration on the part of intensive care medical practitioners due to the restrictions of peritoneal dialysis and the delays to the commencement of IHD. Peritoneal Dialysis has been shown to have restricted clearance of wastes and fluids, the risk of the introduction of infections, limiting respiratory and cardiac function as well as making blood glucose levels difficult to manage

Normal IHD treatment consisted of 4 hours of treatment every second day and due to haemodialysis machines requiring specialised staff, that meant patients would need transporting to a dialysis unit for treatment.

It was clear at this early stage that CRRT might have some important advantages over IHD including the haemodynamic stability, control of circulating volume, nutritional support and the ability to manage it fully within the intensive care unit

Differing modes and treatments of CRRT

With much development and alterations over the years CRRT has become quite versatile in an effort for it to more accurately meet treatment goals in a timely manner. In general CRRT can be defined as an extracorporeal blood purification therapy which is able to treat impaired renal function over extended periods of time with treatment able to run 24 hours a day

CRRT modes have been developed by combining the different principles seen in haemodialysis treatments. Each of the different modes offered by the Aquarius dialysis machine is able to achieve different outcomes through the selective removal of solutes and fluids which will be most beneficial to the patient.

  • SCUF – Slow Continuous Ultra filtration,
  • CVVH – Continuous Veno Venous Haemofiltration,
  • CVVHD – Continuous Veno Venous Haemodialysis,
  • CVVHDF – Continuous Veno Venous Haemodiafiltration,
  • TPE – Therapeutic Plasma Exchange,

Complications of CRRT

  • Patients who undergo Continuous Renal Replacement Therapies are vulnerable to many complications especially when they are critically ill.
  • The first major complication of CRRT is hypotension. Even though CRRT is gentler on a patient’s haemodynamic status, it can cause a drop in blood pressure. This is usually easily compensated for by the patient but in some cases inotropic support may be required to maintain effective mean arterial pressures.
  • The second major complication of CRRT is the risk associated with anticoagulation therapies including bleeding and coagulopathy
  • Another complication of CRRT is the introduction of infection through poor aseptic technique when handling the CRRT circuit, filter and vascath. It can also develop when a vascath has been in the patient for an extended period of time, particularly in a femoral site, as these vascath lines have a shorter life span

CRRT can cause electrolyte and acid-base imbalances if not managed correctly, so nurses must be constantly monitoring the patient for the signs and symptoms and looking at blood results

Indications for CRRT (conditions requiring CRRT)

The predominant indication for CRRT in intensive care is the diagnosis of Acute Renal Failure where the patient is haemodynamically unstable however; CRRT has also proven beneficial in cases of drug toxicity. Proposed criteria for commencing a critically ill patient on CRRT treatments include:

  • Oliguria (200ml in 12 hours)
  • Anuria (less than 50ml in 12 hours)
  • Hyperkalaemia (Potassium >6.5 mmol/L)
  • Severe acidaemia (pH <7.1)
  • Azotaemia (urea >30 mmol/L)
  • Significant organ oedema (lung or heart overload)
  • Uraemic encephalopathy
  • Uraemic pericarditis
  • Uraemic neuropathy/myopathy
  • Severe dysnatraemia (Sodium >160 or <115 mmol/L)
  • Hyperthermia
  • Drug overdose with dialysable toxin