CRRT- Continuous Renal Replacement Therapy

Continuous Renal Replacement Therapy

People often confuse kidney failure with acute kidney injury. Acute Kidney Injury(AKI) refers to a kidney failure that occurs within a very short period, usually one or two days.

Acute Kidney Injury is more serious than kidney failure but there’s a silver lining here. Depending on the cause of acute kidney injury, it can heal by CRRT.

How do you know if your kidneys are not working properly?

Decreased urine output is the main vital sign that you should look for if you suspect kidney disease. However, the following can be additional signs of kidney disease.

  • Constant fatigue
  • Trouble in concentrating
  • Insomnia
  • Dry and Itchy skin
  • Blood in the urine
  • Puffiness around eyes
  • Foamy urine

How is acute kidney failure different from chronic kidney disease?

In the case of chronic disease, kidney failure occurs over some time whereas, in the case of acute kidney failure, it is sudden damage. The damage can take place in a day or even a few hours.

The other name for Acute kidney injury is ‘acute renal failure.’ AKI builds up the waste products in the blood and creates a fluid imbalance in the body.

Whom does acute kidney injury affect and how CRRT can help?

There are no standard criteria for judging whom AKI will affect. However, it is seen that the people who already are in ICU are prone to it. People who are already on ECMO can experience AKI and need immediate CRRT.

While ECMO is also used to purify the blood outside the body and push it in the body, there is a little difference between the two procedures.

ECMO adds oxygen and other minerals to blood and pushes it inside the body. It helps the heart and lungs to relax.

Whereas, CRRT also purifies blood outside the body but it removes toxins and filters unwanted things from the blood and repumps the filtered blood into the body. It relaxes the kidney.

Apart from that, the people who are vulnerable to AKI include:

  • People who are in ICU
  • People with existing kidney diseases
  • People aged 65 or more (the elders)
  • People who suffer from chronic diseases
  • People with high Blood pressure

People who already have existing health conditions or are in ICU are already sick. They are more prone to AKI. In the case of AKI, it is better if they are provided CRRT treatment rather than simple dialysis.

Dialysis can be done two or three days a week for three to four hours but it is a speedy process and puts an extra load on the heart. This can in turn damage other organs of the body.

CRRT can be quite useful in cases where the patient’s body is incapable of bearing the load of dialysis.

How is acute kidney injury diagnosed?

CRRT can be applied to a patient in the case of AKI. But often the question is how AKI is diagnosed? AKI in medical terms is defined as,

  • Serum creatinine > 0.3mg/dL or more within 48 hours or
  • Considerable increase in Serum creatinine that is more than 1.5 times baseline or more within a week or
  • Urine output < 0.5 ml/Kg/hr for 6 hours

What causes acute kidney injury?

The whole process of doing CRRT depends on the cause of AKI. Acute damage to the kidney can happen due to

  • Inadequate blood flow to the kidneys
  • The existing problem with the kidney
  • Blockages in ureters. The job of Ureters is to carry urine from the kidneys to the bladder.
  • Blood pressure and diabetes

f the underlying cause for the damage is known and analysed then it is easy to judge whether a patient can be kept on dialysis or needs CRRT.

CRRT can help the kidneys to recover depending on the damage done to them.

What is CRRT, and how does it help?

Patients with AKI need blood purification therapy which is gentle on their bodies. CRRT helps in the purification of blood gently, without being harsh on the other body organs.

CRRT removes fluid and uremic toxins from the blood and then returns them to the body. Unlike dialysis that needs just three to four hours, CRRT is to be done over 24 hours and is a slow process.


The CRRT machine is complex to operate. There are six medical products required to perform CRRT on a patient:

Blood Purification Machine: This is the machine that pumps the blood. It controls the blood flow in the machine and into the body after being purified.

Dialysate: It is a type of fluid that helps to remove toxins from the filter.

Replacement fluid: It is a kind of sterile fluid that helps to flush toxins. It also helps in replacing the electrolytes and other necessary things lost during the filtration process.

Filter: It is used to remove fluid and uremic toxins from the blood that is inputted in the CRRT machine.

Anticoagulation method: There is a huge possibility of blood clotting inside the machine and therefore anticoagulation helps in a smooth blood flow.

Blood warmer: It maintains the temperature of blood during the purification process.

What are the difficulties in doing CRRT in COVID patients?

COVID patients face the problem of clotting of blood while doing CRRT. COVID patients develop cytokine storms and their immune system reacts adversely. It is seen that the immune system produces infection-fighting substances which in turn result in blood clotting inside the machine.

What are the signs the kidneys are recovering?

As said earlier, the first sign of kidney recovery is the smooth flow of urine. Creatinine is not a proper parameter to measure the functioning of the kidney, because through the CRRT machine the body is already getting filtered blood so creatinine is going to get reduced anyways.

So the true test of whether the kidneys have repaired themselves is the passing of urine in the right quantities. It does not matter whether the patient is taking fluids externally because intravenous fluids are injected into the body.

Unless the tubules in the kidney are repaired, they do not allow the smooth flow of the urine. Through the CRRT machine, kidneys get a chance to repair the tubules.

How long do patients stay on continuous dialysis/CRRT machines?

CRRT machines can be used till the time the kidneys begin to function normally or the body can bear the normal dialysis procedure.

How to keep your kidneys healthy?

  • Always stay hydrated. Don’t drink when you are thirsty, drink intermittently.
  • Don’t intake too many medicines without consulting a doctor.
  • Keep your blood pressure and diabetes in control

Where can we obtain treatment through CRRT?

CRRT treatment requires specialized and skilled staff to operate. Due to the huge capital cost involved, very few hospitals can afford the CRRT machine.

Expertise and cost are the two most critical factors when you want to find a hospital offering CRRT treatment.

At Janvi Multispeciality hospital, we have expert doctors and expert staff to take care of patients who are on CRRT machines.

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