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Cerebral blood flow autoregulation is preserved during cardiopulmonary bypass in isoflurane-anesthetized patients
L J Aladj1, N Croughwell, L R Smith
1Heart Center, Duke University Hospital, Durham, North Carolina.
Insights
Isoflurane anesthesia during cardiopulmonary bypass preserves cerebral blood flow (CBF) autoregulation. This study found that mean arterial pressure changes did not affect CBF in patients receiving isoflurane, indicating preserved pressure-flow relationships.
Area of Science:
- Anesthesiology
- Neurosurgery
- Cardiovascular Surgery
Background:
- Coronary artery bypass surgery often involves cardiopulmonary bypass, which can affect cerebral blood flow (CBF).
- Maintaining adequate CBF and its autoregulation is crucial during surgery to prevent neurological complications.
Purpose of the Study:
- To investigate whether isoflurane anesthesia abolishes the relationship between mean arterial pressure and CBF (pressure-flow autoregulation) during hypothermic nonpulsatile cardiopulmonary bypass.
- To assess the impact of different isoflurane concentrations on cerebral blood flow autoregulation.
Main Methods:
- 21 patients undergoing elective coronary artery bypass surgery were studied.
- Cerebral blood flow (CBF) was measured using 133Xe clearance during cardiopulmonary bypass.
- Patients were divided into three anesthesia groups: midazolam/fentanyl, midazolam/fentanyl/0.6% isoflurane, and midazolam/fentanyl/1.2% isoflurane.
- Mean arterial pressure was increased by phenylephrine to assess pressure-flow autoregulation.
Main Results:
- Isoflurane significantly decreased mean arterial pressure and was associated with lower CBF.
- Increasing mean arterial pressure by 25-34% had no effect on CBF in any group.
- Pressure-flow autoregulation of CBF was preserved across all groups studied.
Conclusions:
- Isoflurane anesthesia, within the studied concentrations, does not abolish pressure-flow autoregulation of cerebral blood flow during cardiopulmonary bypass.
- Cerebral blood flow autoregulation remains intact during isoflurane administration for cardiac surgery, ensuring stable brain perfusion.
Abstract:
In 21 patients undergoing elective coronary artery bypass surgery, cerebral blood flow (CBF) was measured during hypothermic nonpulsatile cardiopulmonary bypass to test the hypothesis that isoflurane abolished the mean arterial pressure-CBF relation (pressure-flow autoregulation). Cerebral blood flow was determined by 133Xe clearance. The patients were randomly divided into three groups according to anesthesia during cardiopulmonary bypass: group 1 received midazolam and fentanyl; group 2 received, in addition to midazolam and fentanyl, 0.6% isoflurane; and group 3 received, in addition to midazolam and fentanyl, 1.2% isoflurane. The groups were maintained at a constant temperature, PaO2, PaCO2, and pump flow during CBF measurements. Mean arterial pressure was increased by phenylephrine greater than or equal to 25% after the first CBF determination. Isoflurane decreased mean arterial pressure significantly (P less than 0.05) and was associated with lower CBF. Increasing the mean arterial pressure 29% in group 1, 25% in group 2, and 34% in group 3 had no effect on CBF. We conclude that, within the range studied, pressure-flow CBF autoregulation is preserved during isoflurane anesthesia administered for cardiopulmonary bypass.