Browsing by Subject "arterial carbon dioxide tension"

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    The Effect of Hyperventilation on the Increase of Cerebral Blood Flow Velocity Secondary to Deflation of the Tourniquet in Lower Extremity Surgery; [Alt Ekstremite Cerrahisinde Turnike Açilmasina Sekonder Beyin Kan Akim Hizi Artişina Hiperventilasyonun Etkisi]
    (2003) Sakarya M.; Topçu I.; Özkol M.; Yentür A.; Yercan H.; Okçu G.
    We aimed to investigate the effects of hyperventilation on cerebral blood flow (CBF) in order to maintain normocapnia following the deflation of the tourniquet in patients undergoing elective lower extremity operation during intravenous general anesthesia (TIVA). In all cases(n=15), anaesthesia was induced by 2 mg kg-1 propofol, 1 μg kg-1 remifentanyl and 1 mg kg-1 vecuronium, and was maintained with the mixture of 50 % air-O2, 6-8 mg kg-1 dk-1 propofol and 0.5 μg kg-1 dk-1 remifentanyl infusions. Patients were randomized into two groups. Group I (n=7) was ventilated by f=10/min and V T=8 mL kg-1. Patients in group II (n=8) were ventilated similarly as group I until the deflation of tourniquet, and following deflation by increasing respiratory frequency adjusted to maintain end-tidal CO 2 (PETCO2) between 30-35 mmHg. Middle cerebral artery (MCA) flow velocity was measured by transcranial Doppler ultrasonography as mean (m-MCA) and peak (p-MCA) values. Data were recorded 5 minutes before tourniquet deflation (control), and every minute in the first 10 minutes following deflation While there has been no difference for p-MCA, m-MCA and PaCO2 in group II, significant increases (p<0.05) in mean MCA flow velocity were obtained in 2nd, 3rd and 4th minutes in group I. Maximum increase was obtained in 3rd minute and determined as 52±7 cm/sec. The increases of PaCO2 were obtained in 2 to 6 minutes (p<0.05) and maximum level was 41±1 mmHg (25 %±3 %) in 3rd minute. We concluded that, the increase of MCA flow velocity and CBF related to the increase of PaCO2 after deflation of the pneumatic tourniquet may be prevented by maintaining normocapnia provided by increasing minute ventilation.
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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.