Browsing by Subject "Middle Cerebral Artery"

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    Effect of Propofol and Clonidine on Cerebral Blood Flow Velocity and Carbon Dioxide Reactivity in the Middle Cerebral Artery
    (2004) Mirzai H.; Tekin I.; Tarhan S.; Ok G.; Goktan C.
    This study was designed to evaluate the effects of propofol alone and propofol-clonidine combination on human middle cerebral artery blood flow velocity (Vmca) and cerebrovascular carbon dioxide (CO2) response by using transcranial Doppler ultrasonography. Mean Vmca in response to changes in arterial partial pressure of CO2 (PaCO2) was determined under the following conditions: awake (group 1), propofol anesthesia (group 2), and combined propofol-clonidine anesthesia (group 3). Normocapnic, hypercapnic, and hypocapnic values of heart rate, mean arterial pressure, partial end-tidal CO2 pressure, PaCO2, and Vmca were obtained. The mean Vmca in groups 2 and 3 was significantly lower than that in group 1 at each level of PaCO2. The calculated Vmca at each level of PaCO 2 was not different between groups 2 and 3. There was a correlation between PaCO2 and Vmca in all groups, but in the anesthetized groups the effect of PaCO2 on Vmca was attenuated. The present data demonstrated that clonidine-propofol does not change CO2 reactivity compared with propofol alone, but both anesthetics attenuate cerebral blood flow compared with awake controls.
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    Assessment of fetal cerebral arterial and venous blood flow before and after vaginal delivery or Cesarean section
    (2004) Baytur Y.B.; Tarhan S.; Uyar Y.; Ozcakir H.T.; Lacin S.; Coban B.; Inceboz U.; Caglar H.
    Objectives: To compare perinatal intracranial arterial and venous blood velocity changes between healthy term neonates delivered vaginally or by Cesarean section and to correlate these changes with cord blood gases and pH values at birth. Methods: The study involved 43 healthy term neonates who were delivered vaginally (n = 20) or by Cesarean section (n = 23). All fetuses/neonates were examined by Doppler ultrasound to obtain middle cerebral artery (MCA) and cerebral transverse sinus (Tsin) Doppler waveforms on three occasions (before delivery, and 1 h and 24 h after birth). Pulsatility index (PI) and peak systolic velocity (PSV) for MCA and Tsin were measured and compared between neonates who were delivered vaginally or by Cesarean section. Umbilical cord blood samples were analyzed for umbilical artery and vein pH, pO2 and pCO2 and values were correlated with MCA and Tsin Doppler indices. Results: MCA-PI increased and MCA-PSV decreased at 1 h after birth, and Doppler measurements returned to predelivery values at 24 h after birth. Tsin Doppler measurements remained unchanged at 1 h and 24 h when compared to predelivery values in both the Cesarean and vaginal delivery groups. There was a negative correlation between Tsin-PI before birth and umbilical venous pH. There was a positive correlation between Tsin-PSV at 1 h after birth and umbilical vein pCO2. Conclusions: Cerebral arterial blood velocity decreases immediately after birth and increases within 24 h probably as part of neonatal adaptation. Cerebral venous blood velocity remains constant during the perinatal period and is likely to be regulated in a different and more complex manner than that of arterial blood velocity. Mode of delivery does not affect cerebral blood velocity. Copyright © 2004 ISUOG.