Clamping ischemia, threshold ischemia and delayed insertion of the shunt during carotid endarterectomy with patch

Shunt insertion during carotid endarterectomy (CEA) is mandatory to avoid neurological damage due to clamping ischemia; however shunt insertion before plaque removal has many inconveniences (atheroembolism, intimal dissection, difficulty of endarterectomy). The aim of this study is to verify whether and how long shunt insertion may be safely delayed to permit plaque removal and ensure cerebral perfusion during the further time consuming manoeuvres of CEA (peeling, patch angioplasty).

From July 1990 to February 1996 383 patients underwent 411 CEAs under general anesthesia with EEG continuous monitoring and PTFE patch angioplasty. A Pruitt-Inahara shunt was routinely inserted only after atherosclerotic plaque removal. In 316 CEAs (76.9%) without EEG signs of cerebral ischemia (Group A) the mean clamping time was 10 min +/-4.8 (range 2-37 min). In 95 CEAs (23.1%) with EEG signs of cerebral ischemia (Group B) it was 7.3 min +/-3.5 (range 3-20 min). All patients had normal EEG signals after delayed shunt insertion and reperfusion (mean 21 min, range 5-45 min).

In the short term results (within 30 days) there was a relevant neurological complication rate of 0.96% (2 major stroke and 2 lethal stroke); at awakening we observed 5 RINDs (1.21% of total) 1 in a patient of Group A (0.31%) and the other 4 in patients of Group B (4.21%).

These data confirm the rationale of a delayed insertion of the shunt: actually the cerebral parenchyma may tolerate under general anesthesia a sufferance due to carotid clamping, EEG detectable, without neurological deficits for at least 7.3 min. This time is sufficient to perform the most difficult steps of CEA (plaque removal, distal intima checking) allowing shunt insertion in a clean operatory field, without inconveniences. Finally the shunt allows complementary time consuming steps, as patch angioplasty, with improvement of both short- and long-term results.