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399: Hemodynamic changes in the middle cerebral artery of fetuses undergoing laser surgery for twin-twin transfusion syndrome: evidence of cerebral autoregulation?

      Objective

      We hypothesized that laser surgery for twin-twin transfusion syndrome (TTTS) would result in fetal hemodynamic alterations, manifested by changes in cerebral vessel resistance with autoregulation of blood flow. The study objective was to compare the middle cerebral artery (MCA) pulsatility index (PI) and mean velocity (mean V) before and after laser surgery for TTTS.

      Study Design

      A prospective observational study of TTTS patients was conducted. MCA Doppler examination was attempted within one day before and after laser surgery for TTTS. Patients were excluded from analysis if MCA Doppler measurements were unavailable (n=41) or if gestational age (GA) was less than 18 weeks (n=13). The pre- and postoperative mean (S.D.) of the MCA PI and mean V z-scores of the recipient and donor fetuses were calculated and compared. Demographic and outcome data were analyzed in relation to the MCA PI and mean V. Data were analyzed using paired t-tests and multivariable linear regression models.

      Results

      Of 157 patients, 103 met study criteria. The MCA PI z-scores of the recipients increased from −1.29 (1.20) preoperatively to 0.14 (1.52) postoperatively (p<0.0001), while the donors' decreased from −0.31 (1.67) to −0.67 (1.29), p=0.07. MCA mean V z-scores did not change following surgery in donors and recipients. Some significant associations were identified between changes in the MCA PI and mean V and Quintero stage, GA at surgery, numbers of vessels lasered, donor growth restriction, and outcomes (GA of delivery, survival).

      Conclusion

      Post laser surgery for TTTS, the recipient's MCA PI increased toward normal values, and MCA PI values in the donor tended to decrease slightly or stabilize. There was no significant change in the MCA mean V. These findings may provide supportive evidence for autoregulatory capacity in the cerebral vessels of the mid-trimester fetus.