A 28 year G3P2 carrying twins vertex vertex, presents the day before induction for consultation with anesthesia. She states that she was diagnosed with thrombocytopenia by MFM, and started on 10 mg of prednisone for a platelet count of 71K. She has had two prior deliveries without epidural analgesia. She plans on vaginal delivery this pregnancy without epidural analgesia.
In a recent study published in the NEJM, 2,804 women were followed with twin pregnancy. Those who planned for vaginal birth ended up getting a c-section 44% of the time. This study looked at mortality and morbidity in women and fetuses who had planned c-section v. planned vaginal delivery. There was no difference between groups in terms of outcome. The study did exclude any patients whose twin A was in the breech position, in which case, those patients were delivered by c-section. Another study did show that a major risk factor for unplanned c-section in twin pregnancy is nulliparity and breech twin B.
While twin pregnancy is rare, so also is thrombocytopenia. While up to 12% of obstetric patients may have some degree of thrombocytopenia, only 1% meet the definition of moderate to severe thrombocytopenia (<100,000 x 10^6/L). An anesthesiologist confronting a parturient with thrombocytopenia is most likely to be dealing with one of three main etiologies: 1) gestational thrombocytopenia 2) Immune thrombocytopenia (ITP) or 3) thrombocytopenia associated with hypertensive disorders of pregnancy (i.e. pre eclampsia; hemolysis, elevate liver enzymes, low platelet count [HELLP] syndrome). It is estimated that of parturients who are diagnosed with Thrombocytopenia, 80% of these cases are a result of gestational thrombocytopenia (affects 5-11% of pregnant patients). Some important diagnostic clues include onset in the mid second semester to third semester, mild Thrombocytopenia (not usually less than 75K), no outward symptoms (easy bruising etc), and no prior history of Thrombocytopenia. The diagnosis can only be made by exclusion of other causes. The other main cause of Thrombocytopenia during pregnancy is that related to hypertensive disease of pregnancy. This comprises 8 to 21% of patients with Thrombocytopenia during pregnancy. In these cases platelet function can be impaired in addition to decreased in number. The etiology of Thrombocytopenia in both of these conditions in unknown.
Unfortunately, given the low number of parturients presenting with thrombocytopenia who need neuraxial anesthesia, we do not have good numbers to determine the absolute risk (probability) of any one patient developing an epidural hematoma. It should be noted, that thrombocytopenia refers simply to how many platelets are available, but tells us nothing of platelet function which may be normal, reduced or even increased. Indeed, in pre eclampsia, platelet function is often impaired. However, in general we know that the risk of epidural hematoma with neuraxial anesthesia is about 1:250,000 in all comers. In a meta analysis reviewing 7509 neuraxial procedures, most epidural hematomas occurred in patients with platelet counts < 50,000 x 10^6/L. Of women with platelet counts < 100,000 x 10^6/L there were a total of 33 epidural hematomas, and 5 of these occurred in women with platelet counts between 44,000 and 91,000. However, ALL five of these had other ongoing issues [1 with AVM, 1 was coagulopathic on top of the low platelet count, 2 had HELLP syndrome, and 1 had full blown eclampsia).
In another study, 1524 patients received neuraxial anesthesia with no epidural hematomas noted. The authors, however, estimated the upper limits of the 95% CI for the risk of spinal epidural hematoma stratified by platelet count.
- 70K to 100K ....0.2% risk
- 50K to 69K ....3% risk
- <50K .........11%