Monitoring: Equipment and Computers
Goal of Study: Near infrared spectroscopy (NIRS) monitoring was used to guide anaesthetic management in patients undergoing carotid endarterectomy (CEA).
Methods: After board approval and patient informed consent 17 consecutive patients aged 50-80 yrs underwent CEA under general anaesthesia. Changes in ipsilateral and contralateral regional O2 saturation (rSO2) were monitored by NIRS. Heart rate, pulse oximetry (SpO2) and direct arterial blood pressure were continuously monitored and recorded in one minute intervals. Changes in rSO2 were recorded in absolute percent change. The relative changes of rSO2 from baseline were calculated (absolute change in rSO2/baseline rSO2). The anaesthetic management included head positioning, mean arterial pressure (MAP), FiO2, PaCO2 and anaesthetic depth adjustment. The patients were evaluated neurologically and Ramsey and Sedation Agitation Scale (SAS) values were taken before induction and 15 min after emergence.
Results: Baseline rSO2 values varied significantly among patients (47-80%). In 2/17 (12%) patients the relative rSO2 change due to head malpositioning was 0-35% (0-20% in absolute values) and immediate repositioning was made. After emergence there was no neurological deficit and they had SAS score 3-4 and Ramsey score 2-3. In 5/17 (29.5%) cases the relative rSO2 change was 10-17% (5-14% absolute value) which was corrected when the MAP was adjusted to 130-150 mmHg. After emergence there was no neurological deficit and they had SAS score 3-4 and Ramsey score 2-3. In 4/17 (23.5%) patients the relative rSO2 change was 5-23% (5-12% in absolute values) due to PaCO2 values (28-38 mmHg) which was adjusted to PaCO2 40-50 mmHg where the rSO2 was normal. After emergence there was no neurological deficit and they had SAS score 3-4 and Ramsey score 2-3. In 1/17 (6%) patient relative rSO2 increase was noticed up to 15% (0-12% in absolute values) after CEA. After emergence the patient had no neurological deficit with SAS score 6 and Ramsey score 1. In 1/17 (6%) patient the relative rSO2 decrease was 10-25% (5-12% in absolute values). After emergence the patient had no deficit with SAS score 2 and Ramsey score 5.
Conclusion: NIRS may prove a useful non-invasive diagnostic tool in early detecting intraoperative cerebral ischemia and guide to anaesthetic interventions.