About 13-36% of TTP-HUS in women is associated with pregnancy. Pregnancy may be a risk factor for developing TTP-HUS because of hypercoagulability, loss of integral endothelial cell membrane proteins, decreased fibrinolytic activity and ADAMTS13 activity. Among all patients with pregnancy associated TTP-HUS , 8% occurs in the 1st trimester, 16% in the 2nd trimester and 77% in the 3rd trimester or post-partum.
There are a number of factors to think about in the management of pregnant dialysis patients:
1. Duration and frequency of dialysis: Pregnant patient usually start on daily dialysis with a predialysis BUN goal of <50mg/dl. It has been shown that patients on nocturnal hemodialysis with an average of 48hours/week have better outcomes than women who dialyzed 20 to 26 hours/week.
2. Anemia: Pregnant women usually require higher doses of erythropoietin and iron, with goal of Hg>10g/dl, and transferrin saturation>30%. These targets are based more on patients in the general dialysis population and are not evidence based. Pregnant women are usually anemic although their red cell mass increases.
3. Hypophosphatemia: Our daily phosphorous ingestion is 800 to 1600mg. 2.5g to 3.0g phosphorous is removed during a regular 4 hour dialysis treatment. Phosphorous levels will decrease in patients who receive intensive hemodialysis. Hypophosphatemia can cause tissue hypoxia and intracellular depletion of adenosine triphosphate with impairment of glucose metabolism. In a pregnant patient, our goal is to keep the phosphorous level >3mg/dl with either po repletion or supplemental phosphorous in the dialysate .
4. Calcium: 25 to 30 g of calcium is required for fetal skeletal growth. This demand requires transfer of 140mg/kg/day calcium across the placenta. To prevent osteopenia, it is recommended that an additional 1500mg of calcium be ingested daily during pregnancy.
Our patient was started on 6 times/week hemodialysis for 4 hours each session. Her phosphorous level was 2-2.5mg/dl after 1 week on hemodialysis. With aggressive oral repletion and a regular diet, her phosphorous level was maintained at 3mg/dl upon discharge.
Posted by Jie Cui