Chapter 19: Thrombocytopenia

DEFINITION OF THROMBOCYTOPENIA

Platelet counts (PC) less than 150,000/mm³ are defined as thrombocytopenia. Mean PC decrease in all pregnant women, beginning in the first trimester.¹ Gestational thrombocytopenia is a diagnosis of exclusion in a healthy woman with uncomplicated pregnancy. PC may decrease further in a woman with pregnancy-related complications or preexisting thrombocytopenia.

ETIOLOGY OF THROMBOCYTOPENIA

• Gestational thrombocytopenia: affects 7% to 11% of pregnant women.² Usually, it is mild and stable when platelet count is near or above 100,000/mm³.

• Preeclampsia: accounts for 5% to 21% of cases of thrombocytopenia. Platelet function may be impaired. A severe feature of preeclampsia is hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome.

• Acute placental abruption.

• Acute fatty liver of pregnancy.

• Idiopathic thrombocytopenic purpura (ITP).

• Disseminated intravascular coagulation.

• Thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome, due to congenital or acquired ADAMTS13 (A Disintegrin-like Metalloprotease domain with ThromboSpondin type 1 motifs) deficiency.

• Drug-induced thrombocytopenia (e.g., heparin).

IMPACT ON FETUS AND NEONATES

• Gestational thrombocytopenia: poses no risk to the fetus.

• ITP: there is a 10% to 25% risk of fetal thrombocytopenia.

• Preeclampsia: increases risk (2%) of thrombocytopenia in neonates.

THROMBOCYTOPENIA AND SAFETY OF NEURAXIAL ANESTHESIA

A routine PC is not necessary in the healthy parturients before neuraxial procedures.³

However, a lack of high-quality data surrounds the safe placement of a neuraxial catheter in the parturients with thrombocytopenia. The threshold may vary in different providers and different patients and different thrombocytopenic disorders. The first society consensus statement on neuraxial procedures in obstetric patients was published in 2021, providing the best available evidence and clinical decision aid in the setting of thrombocytopenia.⁴

• Neuraxial anesthesia is considered safe when PC is ≥70,000/mm³ in obstetric patients with gestational thrombocytopenia, ITP, and hypertensive disorders of pregnancy, and PC is stable, function is normal, and patient is not taking antiplatelet or anticoagulant drugs.

• Recommend using flexible catheter.

• Recheck PC before removal of an epidural catheter.

• Consider thromboelastography when PC is between 60,000 and 70,000/mm³.

• When PC is trending down, the interval between the time of PC and neuraxial placement should be taken into consideration. Highly recommend an early epidural placement to the patient before PC decreases further.

• Our practice recommendations are listed in Table 19-1.

REFERENCES