Akiko Inoue, DO 2/17/2010 The perioperative risk of stroke for patients undergoing carotid...
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The Influence of Inspired Oxygen Fraction and End-Tidal Carbon Dioxide on Post-Cross- Clamp Cerebral Oxygenation During Carotid Endarterectomy Under General Anesthesia 1 Akiko Inoue, DO 2/17/2010
Akiko Inoue, DO 2/17/2010 The perioperative risk of stroke for patients undergoing carotid endarterectomy (CEA). Literature has not provide consistent
The perioperative risk of stroke for patients undergoing
carotid endarterectomy (CEA). Literature has not provide consistent
measures to reduce this risk. Reversal of neurological deficit due
to cerebral hypoperfusion after carotid artery cross-clamping has
been demonstrated by increasing inspired oxygen fraction (FIO 2 )
Regional oxygenation (rSO 2 ) has been shown to improve by
increasing FIO 2.
Slide 4
In healthy subjects, both middle cerebral flow velocity and rSO
2 increase with increase in PaCO 2. Studies have shown paradoxical
improvements in cerebral blood flow on the ipsilateral side of
cross-clamping with hypocapnia. Hypocapnia restores cerebral
autoregulation during isoflurane anesthesia. Cerebral near-infrared
spectroscopy (NIRS) monitors continuous rSO 2 and estimates balance
between cerebral O 2 supply and demand.
Slide 5
Hypothesis: To determine whether increases in the FIO 2 or
PETCO 2 correlate to a significant change in rSO 2 in patient
undergoing CEA under general anesthesia with and without shunts
during the period of the carotid cross- clamp. Methods:
Prospective, controlled (pilot study, each pt acted as their own
control) study 20 subjects (10 shunting, 10 w/o shunting)
recruited, partial data from 1 subject of unshunted group were
excluded 2/2 hypotension. Exclusion criteria Refused to consent,
respiratory failure, or non-English speaker.
Slide 6
Patients received: premedicated, Midazolam Induced, fentanyl
and propofol Vecuronium or cisatracurium Isoflurane, O 2, N 2 O (2
unshunted and 1 shunted pts) or air, and remifentanil infusion All
patients received phenylephrine to maintain stable arterial
pressure (no higher than 25% of normal). Monitoring: A-line, rSO 2
by INVOS 5100B, optodes, placed by a single researcher
Slide 7
After carotid cross-clamping, FIO 2 and minute ventilation
(constant TV) were adjusted by changing RR to achieve: 1)FIO 2 30%,
PETCO 2 30-35mm Hg 2)FIO 2 100%, PETCO 2 30-35mmHg 3)FIO 2 100%,
PETCO 2 40-45mmHg rSO 2 was measured after at least 5 minutes, once
rSO 2 had stabilized. Data for shunted pts were recorded after
shunts were in situ and open. A paired samples T-test was used to
detect changes in rSO 2, P
