1Clinical Perfusionist, Department of Cardio-Thoracic and Vascular Surgery, All India Institute of Medical Sciences (AIIMS), Ansari Nagar, New Delhi
2Assistant Professor, Department of Cardio-Thoracic and Vascular Surgery, All India Institute of Medical Sciences (AIIMS), Ansari Nagar, New Delhi
3Professor, Department of Cardio-Thoracic and Vascular Surgery, All India Institute of Medical Sciences (AIIMS), Ansari Nagar, New Delhi
4Professor, Department of Cardio-Thoracic and Vascular Anaesthesia, All India Institute of Medical Sciences (AIIMS), Ansari Nagar, New Delhi
*Corresponding Author: Sandeep Kumar, Clinical Perfusionist
Online published on 23 December, 2015.
Bispecteral Index and Near infrared Spectroscopy monitoring are standard monitoring regimen in anesthesia practice as well as in cardiac surgery. Both are important neuromonitoring modalities during cardiopulmonary bypass (CPB) due to high incidence of adverse neurologic outcome in post-operative period.
This observational and prospective study was designed to monitor the changes in Bi Specteral Index (BiS) and Near Infrared Spectroscopy (NIRS) at different steps of CPB in 40 patients undergoing Coronary artery bypass grafting (CABG).
40 patients of either sex in the range of age 30 to 70 years undergoing CABG with the use of CPB were studied. In all 40 patients both BiS and NIRS (right and left) electrodes were applied and values were studied at different steps of CPB.
In this study BiS showed increased value at initiation of bypass because ofanaesthetic drug dilution and a lower BiS value was observed at stable hypothermic state (32°C) because of decreased metabolic activity of neuronal cells. As increased value of BiS at stable normothermic state (35°C) and at aortic cannula removal indicated increased metabolic activity and chances of awareness.
The NIRS right and left electrode values decreased from baseline values on initiation of bypass because of loss of pulsatile perfusion and haemodilution. Increased NIRS values were seen in stable hypothermic state (32°C) because of less oxygen uptake by the brain tissue. NIRS returned to its baseline values when physiologic circulation was resumed at the end of bypass.
From our study we conclude that low BiS values can indicate poor perfusion only but it takes some time as compared to NIRS values where sometimes low values of NIRS are related to hypocarbia (due to cerebral vasoconstriction), hypoperfusion, low Hb and Hematocrit values. NIRS can also detect cannula malposition and carotid stenosis if one of either two electrodes shows a low value, while a high value of one of the two electrodes can be because of a large old cerebral infarct. From this study it is recommended to use both BiS and NIRS monitor as neuromonitoring modalities to enhance patient safety and favorable outcome.
cardiopulmonary bypass, neurologic monitoring during CPB, BiS monitor, NIRS monitor
