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Cerebral monitoring during cardiopulmonary bypass in children
F H Kern1, R M Schell, W J Greeley
1Department of Anesthesiology, Duke University School of Medicine, Durham, NC 27710.
Insights
Cerebral metabolic monitoring, not blood flow, is key for brain protection during deep hypothermic circulatory arrest (dhCA). Near-infrared technology shows promise for continuous monitoring, aiding strategies to minimize neurologic injury.
Area of Science:
- Neurology
- Cardiovascular Surgery
- Critical Care Medicine
Background:
- Cerebral monitoring during cardiopulmonary bypass (CPB) is evolving, with growing evidence for its clinical utility.
- Traditional temperature monitoring may be insufficient for optimal cerebral protection during deep hypothermic circulatory arrest (dhCA).
Purpose of the Study:
- To evaluate the clinical utility of various cerebral monitoring techniques during CPB and dhCA.
- To highlight the importance of cerebral metabolic monitoring for ensuring brain protection.
Main Methods:
- Review of recent data supporting cerebral monitoring during CPB.
- Discussion of the benefits of cerebral metabolic monitoring versus cerebral blood flow monitoring.
- Evaluation of jugular venous oxygen saturation and near-infrared spectroscopy (NIRS) for cerebral monitoring.
Main Results:
- Cerebral metabolic monitoring provides crucial information for preparing the brain for dhCPB and dhCA.
- Cerebral blood flow monitoring is less beneficial at deep hypothermic temperatures.
- Jugular venous oxygen saturation monitoring complements temperature monitoring for uniform cerebral cooling and metabolic suppression.
- Near-infrared technology shows feasibility and reliability for monitoring cerebral metabolic activity.
Conclusions:
- Cerebral metabolic monitoring is essential for effective brain protection during CPB and dhCA.
- Near-infrared spectroscopy is a promising noninvasive tool for continuous cerebral metabolic monitoring.
- Longer dhCA periods correlate with more severe cerebral metabolic suppression.
- Cerebral protection strategies like intermittent cerebral perfusion warrant further clinical evaluation.
Abstract:
Although cerebral monitoring during CPB remains primarily investigational, recent data support its clinical utility. In particular, it is cerebral metabolic monitoring that provides meaningful information in terms of preparing the brain for dhCPB and dhCA. Cerebral blood flow or cerebral blood flow velocity monitoring is less beneficial due to the presence of luxuriant cerebral blood flow at deep hypothermic temperatures. Conventional temperature monitoring can be improved upon by adding jugular venous oxygen saturation monitoring to satisfy the primary goal of cerebral protection--uniform cerebral cooling and metabolic suppression. Although online measures of cerebral cellular metabolism are not widely available, early experience with near infrared technology suggests that it is a feasible and reliable monitor of cerebral metabolic activity and is likely to represent an important noninvasive continuous monitor in the near future. CMRO2 recovery data have suggested that cerebral metabolic suppression is more severe the longer the period of dhCA. Cerebral protection strategies, such as intermittent cerebral perfusion have demonstrated less metabolic suppression of dhCA in animal models and are currently undergoing clinical evaluation in our institution. Finally, the postoperative period remains a high-risk period for neurologic injury because temperatures are normothermic, cardiac output is reduced, cerebral autoregulation is impaired, and management strategies, such as hyperventilation, are commonly used to increase pulmonary blood flow with little knowledge on its effects on cerebral perfusion.