Protocols for High-Risk Pregnancies. Группа авторов
is 0.1 mg/kg, and typical dose for fentanyl is 10 μg/kg. Though these may not be needed, especially in the case of an anterior placenta with easy access to the placental cord insertion site, use of paralytics has been associated with lower rates of procedure‐related fetal loss. You will also need heparinized syringes to draw fetal blood samples for testing. These can be prepared by drawing heparin into 1 cc syringes. Caution is required when using heparinized syringes: you will need to waste the heparin from each syringe immediately prior to drawing a fetal sample. IV tubing for your transfusion circuit, sterile probe and ultrasound covers, and spinal needles should be placed on the procedure table as well.
Once your OR table set‐up is complete, follow sterile technique to prep and drape the maternal abdomen. Most large studies conclude that routine antibiotic prophylaxis is not necessary. Your ultrasound machine should ideally have a clear plastic sterile cover over the control panel, so you can continue to manipulate your image settings even after you are gowned up in sterile fashion. A sterile probe cover is part of the usual prep of equipment as well.
Prior to your initial attempt at sampling of the cord, prime the transfusion circuit. The specifics of a transfusion circuit may vary, but typically consist of simple IV tubing connecting the donor blood unit to the lateral port of a three‐way stopcock, and another piece of simple IV tubing extending from the other lateral port, to connect to the spinal needle that accesses the fetal intravascular space. This fetal side of the circuit remains closed while a 10 or 20 cc syringe attached to the middle port is used to draw blood into it to use as a reservoir. Make sure that you and your assistant are familiar with the on/off twisting of the three‐way stopcock and how it changes direction of flow prior to starting the procedure.
Figure 9.2 A typical OR procedure table set‐up for fetal blood transfusion. Left to right, top: Labeled syringe with fetal dose of fentanyl; labeled syringes with fetal dose of vecuronium; labeled syringes with saline to flush the transfusion circuit as needed; marker; three‐way stopcock with attached 10 or 20 cc syringe in the middle port to serve as blood reservoir, as well as IV tubing, one lateral port leading to the donor blood unit and the other port leading to the fetus; 4 × 4 OR sponges. Left to right, bottom: Syringes with heparin to collect fetal blood samples; 20 or 22 gauge spinal needles of varying length; sterile ultrasound probe cover; sterile ultrasound gel; OR drape.
Accessing the cord is the same as in a diagnostic cordocentesis: using your 22 gauge needle and under continuous ultrasound guidance, you will puncture the fetal umbilical vein and direct the tip of the needle to its lumen. When you think you are in the cord, connect your transfusion circuit to the spinal needle. Maintaining the circuit closed to the donor blood, the middle port of the three‐way stopcock is used to confirm needle placement with a saline flush; you should see turbulent flow within the cord as the fluid is pushed through. Once placement is confirmed, use a heparinized syringe to obtain a fetal blood sample. That initial sample is sent to the OR or STAT lab for processing, and you may start transfusion (at a rate of 3–5 mL/min) while you wait for results.
To transfuse, you will pull blood from the donor unit into the reservoir and then push it towards the fetus from the reservoir, opening and closing the ports of the three‐way stopcock as needed to guide the flow of blood in the right direction. As you transfuse, continue to watch for movement of the blood within the cord, which will appear as echogenic turbulent flow, and keep an eye on the fetal heart rate to make sure the fetus is tolerating the procedure. After you have transfused the necessary blood volume, you will want a closing sample to confirm that you have reached your goal Hct. Once you have removed the needle from the cord, you might observe streaming of blood from the puncture site, which is expected.
Postprocedure care
The patient post fetal transfusion will need fetal monitoring to ascertain a reassuring fetal status, and to evaluate for preterm labor. There are no data to suggest a particular length of monitoring post procedure, but if contractions are noted on tocometry, a 24‐hour observation period on Labor and Delivery would be reasonable. Most centers perform fetal transfusion up to 35 weeks of gestation with delivery anticipated at 37–38 weeks. However, every fetal transfusion carries the risk of a procedure‐related loss, especially in the already compromised fetus, so every decision for repeat transfusion should be individualized.
Once discharged from the hospital, the patient should return for follow‐up sonographic evaluation within a week. Doppler of the fetal middle cerebral artery and other sonographic findings will still guide timing of next procedure.
Future directions
The largest volume of cordocenteses and fetal transfusions is done for the evaluation and treatment of fetuses with suspected anemia, usually due to red cell alloimmunization. Besides fetal transfusion, other interventions have been tested to prevent or decrease the severity of fetal anemia in cases of early and severe maternal red cell alloimmunization. These include treatment with either plasmapheresis or IVIG alone or in combination for an attempt at immunomodulation of the disease. There is currently ongoing research into the development of a human IgG1 monoclonal antibody targeting FcRn, the receptor responsible for mediating transfer of IgG across the placenta into the fetal circulation. If these interventions prove successful, they may delay or perhaps eliminate the need for fetal transfusion in some situations.
Suggested reading
1 Deka D, Dadhwal V, Sharma AK, et al. Perinatal survival and procedure‐related complications after intrauterine transfusion for red cell alloimmunization. Arch Gynecol Obstet 2016; 293(5):967–73.
2 Dodd JM, Windrim RC, van Kamp I. Techniques of intrauterine fetal transfusion for women with red‐cell alloimmunization for improving health outcomes. Cochrane Database Syst Rev 2012;( 9):CD007096.
3 Hellmund A, Geipel A, Berg C, et al. Early intrauterine transfusion in fetuses with severe anemia caused by parvovirus B19 infection. Fetal Diagn Ther 2018; 43(2):129–37.
4 Lindenburg ITM, Smits‐Wintjens VE, van Klink JM, et al. Long‐term neuro‐developmental outcome after intrauterine transfusion for hemolytic disease of the fetus/newborn: the LOTUS study. Am J Obstet Gynecol 2012; 206:141.e1–148.e8.
5 Lindenburg ITM, van Kamp I, Oepkes D. Intrauterine blood transfusion: current indications and associated risks. Fetal Diagn Ther 2014; 36:263–71.
6 Ruma MS, Moise KJ Jr, Kim E, et al. Combined plasmapheresis and intravenous immune globulin for the treatment of severe maternal red cell alloimmunization. Am J Obstet Gynecol 2007; 196;138.e1–138.e6.
7 Wallace AH, Dalziel SR, Cowan BR, et al. Long‐term cardiovascular outcome following fetal anaemia and intrauterine transfusion: a cohort study. Arch Dis Child 2017; 102(1):40–5.
8 Zwiers C, Lindenburg ITM, Klumper FJ, et al. Complications of intrauterine intravascular blood transfusion: lessons learned after 1678 procedures. Ultrasound Obstet Gynecol 2017; 50:180–6.
9 Zwiers C, van der Bom JG, van Kamp I, et al. Postponing Early Intrauterine Transfusion with Intravenous immunoglobulin Treatment: the PETIT study on severe hemolytic disease of the fetus and newborn. Am J Obstet Gynecol 2018; 219:291.e1–9.
10 Zwiers C, van Kamp I, Oepkes D, Lopriore E. Intrauterine transfusion and non‐invasive treatment