Protocols for High-Risk Pregnancies. Группа авторов

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.

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