Confirmation of the physiological principles of the sequential laser technique for twin–twin transfusion syndrome: A Sequential Trial subanalysis

Abstract Introduction Twin–twin transfusion syndrome (TTTS) is a complication of monochorionic diamniotic twin pregnancies. It is commonly treated with laser surgery to separate the placental circulations. Perioperative changes in the fetal middle cerebral artery peak systolic velocity (MCA PSV) may characterize the intraoperative blood shifts that occur between the twins during surgery. This study compared changes in the donor MCA PSV for the “selective” versus the “sequential” laser surgery techniques. Methods This is a post hoc analysis of the Sequential Trial, a randomized controlled trial that compared the two laser techniques. The distinguishing characteristic of the sequential technique is that arteriovenous anastomoses are ablated in an order that should allow for an intraoperative blood transfer from the hypervolemic recipient to the hypovolemic donor. We compared the difference (Delta) in donor MCA PSV multiples of the median (MoM) (24‐h postoperative minus preoperative value) by surgical technique. Because anemia is associated with a higher MCA PSV, a negative Delta is consistent with a drop in the MCA PSV and a gain in blood volume. Results Of the 642 patients, 606 (94%) had data available for analysis; 30 (4%) of the donors died within 24 h of surgery, and 6 were missing data and excluded from the analysis. The mean Delta MCA PSV MoM for the donor twin was −0.053 ( p < 0.0001) for the sequential and 0.001 ( p > 0.999) for the selective techniques ( p = 0.003 for comparison of techniques). Based on the presence versus absence of donor critical abnormal Doppler (CAD) parameters and arterioarterial anastomoses (AA), four risk categories for donor survival were described in the Sequential Trial. Mean Deltas for the sequential versus selective procedures in these four categories were as follows: Category 1, no CAD no AA −0.021 versus 0.000, p = 0.162; Category 2, CAD no AA −0.199 versus −0.034, p < 0.001; Category 3, no CAD with AA −0.049 versus 0.121, p = 0.010; and Category 4, CAD with AA 0.073 versus −0.040, p = 0.239. Linear regression for Delta yielded a coefficient for the sequential versus selective techniques of −0.053 (0.024 SE), p = 0.027. Conclusions Patients receiving the sequential technique had a greater drop in the mean donor MCA PSV MoM, suggesting that the sequential technique facilitated an intraoperative net blood transfusion to the donor. This benefit was apparent in Categories 2 and 3.