Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Randomized Controlled Trial Clinical Trial
The influence of arterial oxygenation on cerebral venous oxygen saturation during hyperventilation.
Cerebral venous oxygen desaturation may occur when hyperventilation is employed during neurosurgical procedures. In this study, we examined the effect of arterial hyperoxia (PaO2 > 200 mmHg) on jugular bulb venous oxygen tension (PjvO2), saturation (SjvO2) and content (CjvO2) in 12 patients undergoing anaesthesia for neurosurgical procedures. Under stable anaesthetic conditions, the inspired oxygen fraction (FIO2) was varied to give four different levels of arterial oxygen tension (PaO2 100-200, 201-300, 301-400, and > 400 mmHg), at two levels of controlled hyperventilation (PaCO2(25) and 30 mmHg). ⋯ From these lines we calculated the PjvO2, SjvO2 and CjvO2 at PaO2 of 100, 250 and 400 mmHg, at each level of PaCO2 for each patient. At PaCO2 of 25 mmHg, hyperoxaemia increased PjvO2 (from 27.6 +/- 1.1 mmHg at PaO2 of 100 mmHg to 30.6 +/- 1.4 and 33.6 +/- 1.8 mmHg at PaO2 of 250 and 400 mmHg respectively) and SjvO2 (from 54 +/- 3% at PaO2 of 100 mmHg to 60 +/- 3 and 65 +/- 3% at PaO2 of 250 and 400 mmHg respectively, P < 0.05). Hyperoxaemia had a similar effect on SjvO2 and PjvO2 at a PaCO2 of 30 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)
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This prospective study was completed to determine the influence of epidural anaesthesia on the fetoplacental circulation of normal subjects. Thirty-seven normal pregnant patients at term, undergoing elective Caesarean section, had Doppler measurements of the fetal umbilical artery blood flow velocity before and after epidural anaesthesia using lidocaine 2% without epinephrine. There were no differences in systolic/diastolic, resistance or pulsality indices following epidural anaesthesia. These results suggest that this technique has no adverse effect on fetoplacental circulation in normal non-labouring subjects.