Multi-modality neurophysiologic monitoring for cardiac surgery

A high percentage of patients who undergo cardiac surgery experience persistent cognitive decline. The costs to insurers from brain injury associated with cardiac surgery is enormous. Furthermore, the same processes that injure the brain also appear to cause dysfunction of other vital organs. Therefore, there are great clinical and economic incentives to improve brain protection during cardiac surgery. This article discusses the methods of monitoring neurophysiologic function during heart surgery, including electroencephalography (EEG), near-infrared spectroscopy (NIRS), transcranial doppler (TCD) ultrasound, and cerebral oximetry, and analyzes the effectiveness of multi-modality neuromonitoring.

Neurophysiologic studies have implicated hypoperfusion and dysoxygenation as major causative factors for brain injury during cardiac surgery. Since these functional disturbances are often detectable and correctable, there is a new impetus to examine the role of neurophysiologic monitoring in brain protection. We have used a retrospective, single-surgeon case-control study to examine the influence on outcome following myocardial revascularization of multi-modality neuromonitoring, with modalities that include 4-channel EEG, bilateral cerebral oximetry, and single channel TCD.

The majority of noteworthy functional disturbances detected by neuromonitoring can be corrected by simple adjustments in perfusion, oxygenation, or anesthetic administration. In more recalcitrant cases, pharmacological neuroprotection has proven effective. In addition to the substantial reductions in length of hospital stay, costs, and neurologic complications, the results of neuromonitoring suggest a possible benefit to other vital organ systems. Future studies of neuromonitoring efficacy should not overlook these important accessory benefits.

This study provides the clearest evidence to date that multi-modality neuromonitoring for cardiac surgery is safe, clinically beneficial, and cost-effective. Although neuromonitoring involves negligible risk and modest costs, it's benefits for patient outcome and cost control are substantial.