HDCN Article Review/Hyperlink

Fishbane S, Natke E, Maesaka JK

Role of volume overload in dialysis-refractory hypertension

Am J Kidney Dis (Aug) 28:257-261 1996

The role of volume overload in the hypertension of dialysis patients is controversial. We know that blood pressure in 50 % of dialysis patients either stays the same or increases during dialysis. Because there is sympathetic overactivity in dialysis patients, perhaps in many ESRD patients fluid is not involved in the genesis of hypertension. There are data on both sides. For example, at ASN 1995, Katzarski et al demonstrated a large rebound in the blood volume after short (3 hour) dialysis. Also, Bergstrom's group previously had shown that in patients being dialyzed using the Tassin regimen (6-8 hour dialysis sessions) IVC diameter was lower 24 hours after dialysis as opposed to IVC diameter in patients undergoing "short" treatments. The Tassin patients have good survivals, good blood pressure control, and low requirement for antihypertensive medications.

In a contrarian view, also at the 1995 ASN, Luik and colleagues found that blood pressure only increased in 3/10 patients who were deliberately volume loaded by altering dry weight. Using the CRIT- LINE monitor, Steuer et al presented data at the 1996 ASAIO meeting suggesting that increased fluid removal from patients who were apparently volume overloaded based on intradialytic hematocrit measurements did not lower the blood pressure.

In the present paper, Fishbane et al used predialysis plasma ANP levels as a marker for volume overload. Levels were compared in 12 normotensive HD patients, 12 hypertensive patients whose BP normalized with fluid removal, and 9 patients with dialysis refractory hypertension. Patients with "cardiac disease", which I understand as meaning primarily CHF, were excluded.

Plasma ANF levels in normotensive HD patients averaged about 240 pg/ml and did not change with HD. In the dialysis sensitive hypertensives, plasma ANF was much higher, about 800 pg/ml, but decreased to a mean of 160 pg/ml by the end of dialysis. Surprisingly, in the dialysis resistant group, plasma ANF was quite high, mean 1730 pg/ml, and remained at 1940 pg/ml postdialysis, despite removal of an average of 3.1 L of ultrafiltrate. Six of the 9 volume resistant hypertensives were subjected to extensive UF. In 3 of these 6, dry weight was successfuly reduced by about 2.7 kg and BP became volume responsive. Plasma ANF levels in these "responders" now decreased with dialysis, from about 1100 pg/ml predialysis to 250 postdialysis. In the other 3 patients, attempted reductions in dry weight were accompanied by severe cramps or intradialytic hypotension.

Comment: This is a landmark study in that it casts doubt on the idea that volume resistant hypertension in ESRD patients really exists. It may be that the combination of the relatively high sodium and chloride dialysate used today associated with short treatments, maintains many patients in a covert overhydrated state. It would be fascinating to see if apparently volume resistant hypertensives had a "flat line" hematocrit profile during dialysis, and if reduction of dry weight based on intradialytic hematocrit monitoring would improve their plasma ANF levels. Plasma ANF might conceivably become a useful clinical tool to assess fluid overload in ESRD patients. Much further work needs to be done in this very important area. (John T. Daugirdas, M.D., University of Illinois at Chicago)