Patients with intracranial hemorrhages often develop cerebral edema, which can create unique challenges when providing maintenance hemodialysis. Conall also covering this on RFN a few years back. Hemodialysis can worsen cerebral edema through a rapid decrease in serum osmolarity (urea is rapidly cleared from the blood by the dialyzer but urea transport across brain cell membranes lags behind). As a result, a fairly rapid increase in brain water content develops. Besides worsening cerebral edema, maintenance hemodialysis can also reduce cerebral perfusion if systemic hypotension occurs during dialysis. For these reasons, patients either require continuous renal replacement therapy or modified hemodialysis as outlined below. To reduce the risk of worsening cerebral edema, hemodialysis should be modified to include
- small dialyzers
- slower blood flow rates
- slower dialysate flow rates
- reduced dialysis times
To further reduce changes in osmolarity, one should
- increase the dialysate sodium concentration (consider setting it to 5-10 mEq/L higher than serum sodium).
- Lower the dialysate bicarbonate concentration (consider setting it to 30-32 mEq/L)
- avoiding intracellular acidosis
- subsequent increased intracellular osmolarity
- cell swelling
Other details to reduce overall risk include
- cooling dialysate temperatures to reduce risk of hypotension
- avoiding heparin administration.
As an aside, patients with intracranial hemorrhage are often treated with hypertonic saline. Dialysis patients, in particular, are at risk of developing intravascular volume overload as a result of the large sodium load. This can lead to not only peripheral edema but also pulmonary edema, making ventilation difficult. An alternative to hypertonic saline administration or as an adjunct to reduce the overall sodium load is hyperventilation without humidified air. This will slowly create the desired hypernatremia from free water loss.
Something to consider the next time you see a hemodialysis patient with an intracranial hemorrhage.
Melissa Makar, Nephrology Fellow, Duke