Saturday, January 31, 2009

Treatment Options for Intradialytic Hypotension

Intradialytic hypotension is a relatively common complication in dialysis patients. Here are some of the common therapeutic options to deal with this:

1. Increase the dry weight: one cause for intradialytic hypotension is simply over-ultrafiltration--if a patient is gaining weight but has his dry weight kept constant, this will result in hypotension.

2. Sodium modeling: during the dialysis procedure, solute is removed from the vascular compartment, leading to decreased plasma omolarity relative to the intracellular compartment. This leads to fluid movement into the intracellular compartment in order to maintain osmotic equilibrium, thereby causing a decrease in the systemic blood pressure. The fall in osmolarity is further enhanced by the use of a low sodium (typically 130) dialysate solution. In order to prevent hypotension, the technique of sodium modeling (starting with a higher dialysate sodium and then progressively decreasing the value) may be employed such that much of the ultrafiltration occurs prior to the osmolarity falling to its nadir.

3. Lowering dialysate temperature: decreasing the dialysate temperature from 37 C to 36 C (or even 35C) induces some degree of vasoconstriction which raises BP.

4. Sequential ultrafiltration: this refers to the practice of performing ultrafiltration initially, followed by dialysis.

5. Use of midodrine: this is an alpha-1-agonist which acts as a vasoconstricter. Many dialysis patients take it prophylactically, either before or during dialysis, to prevent intradialytic hypotension.

6. Use of albumin: may be useful in patients who are albumin deficient, though this controversial (and expensive).

7. Use of the "crit-line" monitor: some dialysis machines come equipped with a built-in, real-time "hematocrit monitor" that determines the rate of fluid removal--a rapid decline in the "crit-line" may be an early sign of volume depletion, and one can back-off on the level of ultrafiltration when this is seen, hopefully prior to the onset of actual hypotension.

8. Holding blood pressure medications until after dialysis: some dialysis patients who are sensitive to fluid shifts but still are hypertensive on non-dialysis days should hold their BP meds until after dialysis has finished.

3 comments:

Zach said...

Any thoughts on using mannitol?

nathanhellman said...

Actually our dialysis unit at Mass General Hospital still uses mannitol regularly--but for the purpose of avoiding dialysis disequilibrium syndrome for those patients initiating dialysis. I think this puts us in the minority of dialysis units that still does this however.

Zach said...

Our center uses mannitol as a means to treat intradialytic hypotension up to the last hour of treatment.