Aspects of Cardiothoracic Anaesthesia
The use of near infrared spectroscopy (NIRS) in combined vascular and cardiac surgery: 029
Introduction: NIRS has recently been described as a non-invasive means of brain function monitoring . The ability to measure changes in brain regional oxygen saturation (rSO2) and express them within short time intervals (30 seconds) makes it a useful trend monitor especially where an interruption of flow in the carotid artery is anticipated .
Method: Between November 2000 and November 2003 we used NIRS (INVOS 4100, SOMANETICS) in 58 consecutive patients who underwent combined elective surgery (carotid thromboendoarterectomy - TEAC - and open heart surgery). All the TEACs were performed under general anaesthesia by the vascular surgery team before the beginning of the open heart procedure. 45 patients had an aorto-coronary bypass graft (ACBPG), 36 with cardiopulmonary bypass and 9 off-pump procedures. Of the remaining patients, 5 were operated on for valvular disease and 8 for complex procedures (ACBPG with valvular or left ventricular aneurysmectomy). We considered as a cut-off point for cerebral ischaemia a reduction > of 15% in rSO2 from the baseline value in the first 5 minutes after carotid cross-clamping (CC). An intravascular shunt was placed in patients in whom the cut-off point was reached and in 5 high risk patients electively (bilateral symptomatic disease).
Results: We divided the patients in two groups according to the placement of a shunt: group A (with shunt) and group B (without shunt). Group A comprised 29 patients (50%), of whom 24 (41.3%) were positive for ischaemia and 5 (8.7%) who had an elective shunt. Group B comprised 29 patients (50%) negative for ischaemia, without shunt. None of the patients from group B had complications whereas 3 patients from group A (shunt) had a major neurologic outcome (stroke) in the dependent side. A CT scan and angiography described the nature of the lesion as most probably embolic. Specificity for this cut-off was 61%.
Discussion: INVOS is a useful non-invasive method of brain haemodynamic monitoring in combined surgery (TEAC + heart surgery). In our patients we were able to restrict to less than half, the indication for an intravascular shunt (a method not free from risk, especially embolic) with a favourable neurologic outcome.
1 Samra SK, Dy EA, et al. Evaluation of a cerebral oximeter as a monitor of cerebral ischemia during carotid endarterectomy. Anaesthesiology
© 2004 European Society of Anaesthesiology
2 Youngberg JA, Gold MD. Carotid Artery Surgery: Perioperative anesthetic considerations. In: Kaplan JA ed. Vascular Anesthesia.
New York: Churchill Livingstone, 1991; pp. 333-361.