Is Hemodialysis Dangerous?

By Peter Laird, MD

Since returning from the ADC and I have engaged in extensive literature searches on the issue of myocardial stunning and its associated causes and complications, a related issue is myocardial ischemia (inadequate blood flow to the heart) in dialysis patients with no known coronary artery disease, CHF or LVH.  Silent ischemia is present in a much larger percentage of patients undergoing dialysis than what would intuitively be evident. In a small but well conducted study on myocardial blood flow, researchers were surprised to find that all subjects tested had profound reductions in myocardial blood flow (MBF). Haemodialysis is associated with a pronounced fall in myocardial perfusion:

This study demonstrates that the HD procedure is associated with a significant fall in myocardial perfusion. This was observed in ‘relatively healthy’ dialysis patients that were selected for having a low cardiovascular risk, e.g. non-diabetic patients with stable HD sessions and uneventful cardiac histories. Two of the seven patients who were studied developed regional LV dysfunction in regions with the greatest fall in MBF. Notably, these cardiac derangements were clinically silent.

The most surprising aspect of this study is that the reduction in myocardial blood flow was not related to hypovolemia.  The onset of reduced myocardial blood flow occurred in the first thirty minutes of dialysis in all of the subjects tested despite the fact that they had less than 100 ml of ultrafiltration at that point:

Contrary to our expectations, we observed a significant reduction in MBF already shortly after the start of HD. At this time hypovolaemia was not prominent since only 100 ml of fluid had been filtered during the first 30 min of HD although filling of the extracorporal circuit led to some additional blood loss from the circulation. Notably, at 30 min of HD the diastolic (the main determinant of coronary blood flow) and systolic blood pressure as well as the cardiac output were identical in comparison with baseline. All in all, hypovolaemia seems an unlikely explanation for the decrease in MBF this early during HD.

The implications of this study is that there may be an intrinsic myocardial defect in hemodialysis patients despite no evidence of structural damage or coronary artery occlusions which some researchers have postulated, or on the other hand, there may be an extrinsic or dialysis related effect separate from ultrafiltration that is the cause. Most likely, it is a combination of both intrinsic CKD host factors coupled together with extrinsic dialysis factors.

To date, the issue is not settled other than to note that there is a pronounced reduction in myocardial blood flow at the onset of hemodialysis as well as several studies showing a high incidence of silent myocardial ischemia proceeding to myocardial stunning which is a known precursor of arrhythmias and sudden cardiac death.

Is hemodialysis dangerous?  From the perspective of myocardial blood flow, the answer is possibly yes especially in those patients with known coronary artery disease or other cardiovascular disability which is likewise already a well known caution in these patients from a clinical perspective.  In my opinion, intradialytic hypotension should be diligently avoided in all dialysis patients especially in those patients with known cardiac disease.

Understanding that silent myocardial ischemia is present in the majority of well compensated dialysis patients makes avoidance of any further hemodynamic insult mandatory in all patients, not just those with known cardiovascular disease.  Ultrafiltration rates above 10-12ml/hr/kg add a devastating insult to an already compromised myocardial burden of ischemia.  No matter what the cause is of the original myocardial ischemia in dialysis patients, avoiding intradialytic hypotension from short, violent dialysis sessions should no longer be any part of conventional dialysis care.

Choosing peritoneal dialysis may be the most prudent approach for some patients who are not candidates for renal transplant and have underlying cardiovascular disease.  I believe that informed consent of renal replacement options should include these issues before a patient makes his personal choice. Despite the fact that myocardial ischemia had already been documented in dialysis patients prior to my starting date, I am only now becoming aware of this important issue by my own research after first hearing of the issue of dialysis related myocardial stunning at the ADC. In the end analysis, none of our renal replacement choices are risk free.  Nevertheless, patients have a right to understand what is the true risk, benefit and alternative to each modality. 

From the perspective of renal replacement therapy, the outcomes in high dose optimal dialysis settings with mortality rates that rival cadaveric transplant, the answer to whether hemodialysis is dangerous is no. The results of nocturnal dialysis compared to cadaveric transplant are essentially the same over a 14 year period of time. Understanding that the majority of dialysis patients have a continuum of reduced myocardial blood flow leading to silent ischemia and myocardial stunning should be the most important dialysis issue on the forefront of research in my opinion. 

Look for future posts exploring this important dialysis complication; it is my hope that it will receive the due attention it deserves. Our lives are dependent perhaps more than anything else on this single complication of dialysis.  Sudden cardiac death is the most frequent dialysis death and it may be directly attributable to underlying episodes of myocardial ischemia now documented in the majority of dialysis patients.

Comments

[M3Riddler]

This is a catch 22 in some instances. Some people have already exhausted their choice of Peritoneal Dialysis and this is no longer an option. Then your options are Transplantation or Hemo dialysis in one of its forms, or no dialysis....Even then Transplantation is not always an option either....

[Zach]

Another good reason for all folks on dialysis to set up an exercise program.

Just celebrated my 28th year on in-center hemodialysis. :)
No transplant ... yet.

[Peter Laird, MD]

Dear M3Riddler,

Obviously patients with CKD-5 must choose a renal replacement option or suffer the consequences of their disease, yet the purpose of my post is not to reduce options, but instead to encourage further research into this issue which I believe can be resolved in a positive fashion. The greatest advances in treating myocardial infarction was the understanding of plaque rupture behind the majority of heart attacks. A further advance came later when we understood the role of platelets in this process as well. The result of the basic understanding was to devise treatment options in accord with the underlying pathophysiology. I believe that this will happen with dialysis related myocardial ischemia as well.

[Peter Laird, MD]

Zach, you are absolutely correct about exercise in dialysis patients. I have missed my usual walk the last two days and I feel it this morning. Exercise gives an immediate survival advantage of 10-15% in several studies right from the get go. The role that the patient plays in his own dialysis health care is substantial. Diet, exercise, avoidance of smoking, etc may have a greater predictive value than many other dialysis related factors.

[Sidharth Sethi]

Hi Bill
what happened to CKD Blog reports? I kinda miss them!

[Preeti]

Hello there,

I required a second opinion for somebody I know.A 71 year old male Diabetic(well controlled),CKD -II not yet on maintenance dialysis;was recently diagnosed with CAD Ac MI inf wall ,underwent PTCA stent to LCX, Urea :58mg/dl;serum creatinine then was 1.7mg/dl,BP 100/70mmHg.Does this patient require prophylactic HD?
thanks.

[Peter Laird, MD]

Dear Preeti, DSEN is not a consulting renal nephrologist so as much as we would like to be able to help with such a question, DSEN does not have the credentials to answer this issue for you in a consultant manner. We are instead a dialysis advocacy website dedicated to furthering the known benefits of optimal dialysis for all patients. You may wish to consider having the patient in question consult with a nephrologist who are the only physicians licensed to prescribe dialysis.