Abstract: Background：Premature infants are prone to hemodynamically significant patent ductus arteriosus (hsPDA), which can lead to changes in cerebral blood flow parameters. However, there is limited research on the recovery of cerebral blood flow after ductus arteriosus ligation. Objective：To analyze the impact of hsPDA on cerebral blood flow in premature infants and the recovery of cerebral blood flow after ductus arteriosus ligation using bedside transcranial Doppler ultrasound measurements. Design：Case series report. Methods：Cases who were diagnosed with hsPDA, born at a gestational age of less than 37 weeks, and admitted to the NICU of Zhejiang University School of Medicine Children's Hospital from July 2022 to January 2023, were selected from the HIS system as the case group. The control group consisted of infants with gestational age<37 weeks at the same period in NICU who were confirmed to have no PDA by echocardiography after 72 hours of birth. Cases with concurrent cyanotic or complex congenital heart diseases, severe intracranial hemorrhage or hydrocephalus, and cases undergoing surgical treatment for intestinal infection, necrosis, and perforation were excluded from both groups. Cerebral blood flow parameters of the middle cerebral artery (MCA) and basilar artery (BA) were measured using echocardiography. Main outcome measures：Blood flow parameters of MCA and BA after ductus arteriosus ligation. Results：There were twenty-eight cases in the case group. Arterial duct closure was achieved through medical treatment in 7 cases and surgical intervention in 21 cases. Fourteen cases （50%）were male, and the internal diameter of the PDA was measured to be 2.77±0.53 mm. The control group consisted of 30 cases, and 14 cases (46.7%) were male. No statistically significant differences were found in gender, birth weight, and age between the two groups. The gestational age at birth in the case group was lower than that in the control group, and this difference was statistically significant. For the MCA and BA, the preoperative systolic peak flow velocity (Vs) between the case group and control group had no statistically significant differences; the enddiastolic velocity (Vd) in the case group were lower compared to that in the control group; the preoperative resistance index (RI) and the ratio of Vs to Vs (S/D) were both higher in the case group than that in the control group. These differences were statistically significant. The cerebral blood flow parameters (Vs, Vd, RI and S/D) of MCA and BA in case group after surgery (within 72 hours after PDA ligation surgery in 21 cases) have no statistically significant differences compared to that in the control group. Conclusion：hsPDA causes the abnormities of blood flow parameters in the anterior and posterior circulation of cerebral artery in premature infants. After ductus arteriosus ligation, cerebral blood flow can rapidly recover.

Key words: Patent ductus arteriosus, Transcranial Doppler ultrasound, Premature infant, Cerebral blood flow