Effect Of Norepinephrine On Cerebral Perfusion In Patients With Septic Shock

Objective: The purpose of this study was to evaluate different doses of Norepinephrine(NE)using bedside ultrasound and Transcranial Doppler Ultrasonography(TCD)on Cardiac Output(CO),blood flow of common carotid artery(CCA)and cerebral perfusion in patients with septic shock.Methods: Patients with septic shock admitted to the Intensive Care Unit(ICU)of the Affiliated Hospital of Yangzhou University from April 2022 to January 2023 were enrolled.After adequate fluid resuscitation,Central Venous Pressure(CVP)≥8mm Hg or urine output ≥30ml/h,according to the Saving Sepsis Campaign Guidelines for the Management of severe Sepsis and Septic Shock,patients with Mean Arterial Pressure(MAP)< 65 mm Hg were given norepinephrine to maintain MAP ≥65mm Hg.According to the dose of norepinephrine,the patients were divided into NE 1 group(0-0.1μg/kg/min),NE 2 group(0.1-0.2μg/kg/min),NE 3 group(0.2-0.3μg/kg/min),NE 4 group(0.3-0.4μg/kg/min),NE 5 group(0.4-0.5μg/kg/min)and NE 6 group(> 0.5μg/kg/min).Cardiac output(CO),Time Average Peak Flow Rate(TAP),cross-sectional area(S)and blood flow(BF)of the common carotid artery were measured by bedside ultrasound.The Perfusion Index(PI)of the Middle Cerebral Artery(MCA)was measured by Transcranial Doppler Ultrasound.Finally,the Cardiac Output(CO),hemodynamic parameters of the common carotid artery(CCA)and Perfusion Index(PI)of the Middle Cerebral Artery(MCA)were compared among the groups to analyze the effects of different doses of norepinephrine on cerebral perfusion.Results: A total of 62 patients were included in the study,including 32 males(52%)and 30 females(48%).A total of 96 data were collected and divided into 6 groups according to the dose,with 16 data in each group.(1)For each group of patients,CO reached the maximum in NE 1 group,and the difference between NE 1 group and other groups was statistically significant(P < 0.05).When the dose of NE was > 0.1μg/kg/min,CO showed a downward trend,and there was no significant difference between group NE 2 and group NE 3(P > 0.05),but there were significant differences between group NE 2 and group NE 3 and other groups(P < 0.05).When the dose of NE was > 0.3μg/kg/min,there was no significant difference among the three groups of NE 4,NE 5 and NE 6(P > 0.05),but there was significant difference between the three groups of NE 4,NE 5 and NE 6(P < 0.05).(2)For CCA blood flow,there was no significant difference between NE 5 group and NE 2 group and NE 3 group,and between NE 2 group and NE 3 group(P > 0.05),but the CCA blood flow in NE 4 group was significantly higher than that in other groups(P < 0.05).The CCA blood flow in NE 1 group was lower than that in NE 4 group,but higher than that in other groups,and the difference was statistically significant(P < 0.05).When the dose of NE was > 0.4μg/kg/min,the CCA blood flow showed a downward trend,and the CCA blood flow in the NE 5 group and NE 6 group decreased sharply,compared with the other groups,the difference was statistically significant(P < 0.05).(3)For the PI value of MCA,there was no significant difference in the PI value of MCA among NE 1 group,NE 2 group,NE 3 group and NE 4 group(P > 0.05),but the PI value of MCA increased when the dose of NE was > 0.4μg/kg/min.There was no significant difference between NE 5 group and NE 6 group(P > 0.05),but there was significant difference between NE 5 group and other groups(P < 0.05).Conclusions:(1)When the dose of norepinephrine was within 0.4μg/kg/min,there was no significant effect on cerebral perfusion;(2)When the dose of norepinephrine in the range of 0.4μg/kg/min,it can reduce cerebral perfusion.