Case Discussion for Glom India on “Darkening of Blood during Hemodialysis” by Dr. Jay Shah

Mr C, 55/Male who is K/c/o DM-CKD on maintenance hemodialysis thrice a week through left brachiocephalic arteriovenous fistula since last 6 months came to our dialysis unit for a holiday hemodialysis. Our HD technician noticed the darkening of blood colour after a few minutes of hemodialysis session commencement.

As per my experience, there can be four major reasons for darkening of blood, listed as below:

1. Dialysis through venous catheter

Blood from venous catheter is usually darker compared to arteriovenous access because of less oxygenation of blood in venous access in comparison to arteriovenous access. It is a common cause of the darkening of blood in hemodialysis while using venous catheters.

2. Clotting in the circuit

Circuit clot is a vital but preventable cause of darkening of blood. Whenever clotting in circuit is suspected, one should visualize the circuit by rinsing the system with saline while temporarily occluding the blood inlet. Other signs of circuit clot include black streaks in the dialyzer, foaming with subsequent clot formation in drip chambers and venous trap, rapid filling of transducer monitors with blood, “Teetering” (blood in the post dialyser venous line segment that is unable to continue into the venous chamber but falls back into the line segment), presence of clots at the inflow dialyser header. Arterial and venous pressure may also change as a result of clotting in the circuit.

3. Hemolysis due to various causes

Acute hemolysis during hemodialysis, although rare but potentially life threatening, can be caused by water contamination, faulty dialysis techniques, chemi­cals, drugs, toxins, or patient-related factors. The diagnosis of acute hemolysis is evident when grossly translu­cent hemolysed blood is observed in the tubing. The most common presenting symptoms are non-specific and may include nausea, vomiting, and abdominal pain. Other symptoms may be shortness of breath, chest pain, back pain and headaches. If hemolysis is suspected during HD, the patient’s blood in the extracorporeal dialysis circuit should not be reinfused.

4. Access recirculation

Hemodialysis access recirculation occurs when dialysed blood returning through the venous needle re-enters the extracorporeal circuit through the arterial needle, rather than returning to the systemic circulation. Access recirculation occurs because of low access flow which may be due to venous stenosis, intra-access stenosis, or arterial inflow stenosis.  High rate of recirculation leads to the dialysed blood coming back to the circuit instead of going back to the body from where fresh blood should enter the circuit. This will make the blood thicker and darker because of removal of water and lack of proper oxygenation of same blood. At times, very high ultrafiltration rate also makes blood slightly darker and thicker in appearance.

Over here, with this particular case, I was able to determine that the reason for blood darkening was Access circulation (#4). Below are certain observations and inputs of mine for the same:

Methods of measuring recirculation:

Methods of measuring recirculation include non-urea-based indicator dilutional methods and urea-based methods. The preferred methods are non-urea-based dilutional methods, however it requires special equipment. Common non-urea-based methods include ultrasound velocity dilution, thermal dilution, optical dilution, conductivity dilution, and potassium dilution. A recirculation value above 5 to 10 percent detected by a non-urea-based method should prompt fistulography.

If a urea-based method is used, the two-needle stopped- or slowed-flow recirculation approach should be used rather than the more traditional three-needle approach. This is consistent with the KDOQI recommendations. Recirculation that is >10 percent by a urea-based method should prompt fistulography.

Protocol for performing the low blood flow technique to measure access recirculation:

Turn off ultrafiltration approximately 30 minutes after the initiation of hemodialysis, obtain arterial and venous line samples, reduce access blood flow to 50 mL/min & obtain the blood sample from the arterial blood line after sufficient time has passed to clear 150 percent of the volume between the arterial needle and the sampling point, but no later than 30 seconds after the reduction of access flow to 50 mL/min.

With our patient, we were conducting dialysis with arteriovenous fistula. There were no signs of clotting in the extracorporeal circuit. Clinical scenario did not fit with hemolysis and other dialysis patients during the same shift were asymptomatic. So, in view of possible access recirculation, trial of change of the position of venous needle to the other site was given. The change in the colour of blood did not appear after changing the venous needle site. Patient had significant outflow stenosis in the fistula. Patient had other signs of severe outflow stenosis like noncollapsibility of fistula on elevating the arm, prolonged bleeding after needle removal, almost absent thrill. Fistulogram with this patient was not possible due to logistic reasons.

Article Courtesy – Dr. Jay Shah.

About him:

Dr Jay H Shah has done DM Nephrology from Institute of Kidney Diseases and Research Center-Dr H L Trivedi Institute of Transplantation Sciences (IKDRC-ITS), Ahmedabad and MD Medicine from Maulana Azad Medical College, Delhi. He is currently working as a Consultant Nephrologist and Transplant Physician at Shalby hospitals, Ahmedabad. He is having active interest in hemodialysis, acute kidney injury and glomerulonephritis.