By Peter Laird, MD
As a physician, one of the most interesting aspects of watching the nightly news is to hear of some "new" research paper telling us of a "new and novel" finding that is worthy of mention on a news cast. Many times I get a feeling of Deja Vu about the alleged "new" report because it is an issue that I had learned in my training many years before. If this had only happened once or twice, I might have an eerie feeling about such a report, but instead it appears to be a pattern of modern medical research to simply spin its wheels on rehashed subjects. NephrOnline has one such report that caught my attention today: Lowering sodium intake might be the best way to manage hypertensioin in dialysis patients:
The investigators found that dry-weight can be assessed inexpensively through relative plasma volume monitoring (which uses photo-optical technology to assess changes in volume of a patient’s blood) and body impedance analysis (which determines lean body mass). They also discovered that restricting salt intake can help control blood pressure and make it easier for patients to get down to a proper dry-weight.
While in medical school, I learned of the relationship between sodium intake and volume expansion of the intravascular space. Throughout my career, in hundreds of patients, I used this information in critically ill patients in the ICU to support inadequate blood pressures with the proper saline solution. I understand the role sodium plays in hypertension, particularly the effect of high sodium on the blood pressure of dialyzors with decreased or no urine output. I understand sodium's role because it has been understood for a long time. Dr. Belding Scribner saw blood pressure control as a primary marker of adequate dialysis and as a result Scribner for decades educated and chided his patients to limit sodium as the key to successfully using dialysis. There is no doubt that confirmatory studies are important and should be done, but it is even more important to accept the original studies in hand, such as the experience in Tassin which has been preaching this very issue since the 1970's with dozens of published reports on the subject.
In the meantime, I eagerly await many unanswered questions about dialysis that I ponder every day that I hook up to my portable NxStage machine. Here is a partial list of my own questions that I look forward to seeing in a new and novel study one day:
- What is the optimal frequency, duration and intensity of dialysis?
- What is the optimal water soluble vitamin replacement dosage?
- What is the cause of sudden cardiac death in dialysis patients?
- What is the cause of myocardial ischemia during hemodialysis sessions?
- What is the optimal hemoglobin level?
- What is the optimal renal diet?
I am sure that there are dozens of questions that researchers would likewise wish to be answered that could be easily added to my short list. However, noting the correlation between salt intake and hypertension is not on my short or long list since that has long since been answered to my satisfaction years ago.
When, my fellow medical colleagues, will the true issues of dialysis ever be addressed? I have now been on hemodialysis for nearly four years and the same questions that I wondered about every time the needle enters my arm I still wonder about. Is it time for more deja vu, or is it instead time to wake up and answer the difficult questions we have had for nearly fifty years?