CARDIOVASCULAR ENGINEERING Journal for Extracorporeal Circulation, Assist Devices,Transplantation and Artificial Organs
	Volume 1, 1996, No 1

Monitoring Cerebral Oxygen Metabolism During Cardiopulmonary Bypass Using Near-Infrared Spectroscopy (NIRS)

E. Schindler, B. Zickmann, G. Hempelmann

Abstract:
Short-term and long-term changes in neuropsychological performance occurring after coronary artery bypass surgery (CABS) have been reported. Although detailed mechanisms of these most serious complications have not yet been completely investigated, both embolism, especially microembolism and cerebral hypoperfusion are involved. Some reports suggest that cerebral ischaemia due to low perfusion pressure during cardiopulmonary bypass (CPB) are responsible. On the other hand cerebral hyperaemia has recently been shown to increase the risk of brain oedema and therefore leads to postoperative neurologic dysfunction. Most cardiopulmonary perfusion is performed at moderate hypothermia and it was suggested that both the introduction and the termination of CPB may result in cerebral oxygen imbalance. For that reason as early as 1965 reports had indicated that monitoring cerebral venous oxygen saturation may be a useful tool to detect phases of cerebral ischaemia in carotid artery surgery. Near-infrared spectroscopy now offers a new possibility to monitor cerebral oxygenation noninvasively in clinical routine. Data obtained by this method suggest that the period of rewarming is the most critical phase during operations with CPB. NIRS monitoring is still a technique that is in evolution. Little or no information on the regional distribution of oxygenation and blood flow can be obtained at this time and spatial resolution is still low. Furthermore, exact quantification of the NIRS spectra will require a more precise knowledge of the optical path lengths in vivo. However, it is possible to monitor cerebral oxygen saturation noninvasively, but we have to find "critical values" below which neurological dysfunction probably occur. NIRS will have to be compared and integrated with information detected by other methods, and studies with a high number of patients have to be performed.

Keywords:
cardiopulmonary bypass, cerebral oxygen metabolism, near-infrared spectroscopy

Address for Correspondence:

[Pabst Science Publishers] [CVE Homepage] [Contents] [Editorials] [Masthead] [Search] [Order]

PABST SCIENCE PUBLISHERS
Lengerich, Berlin, Düsseldorf,
Leipzig, Riga, Scottsdale AZ (USA),
Wien, Zagreb