Correlation Of carotid Artery Stump Pressure With 469 Carotid Endarterectomies Performed In Awake Patients

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Keith D. Calligaro, M.D., Kevin Doerr, RVT, Sandy McAffee-Bennett, RVT, Kathy Mueller, RVT, Matthew Dougherty, MD.
Pennsylvania Hospital, Philadelphia, PA, USA.

Purpose: Carotid artery stump pressure (SP) less than 50 mm Hg systolic has been widely accepted as an indication for selective shunting in patients undergoing carotid endarterectomy (CEA) under general anesthesia, although many surgeons currently prefer EEG monitoring. We studied whether this SP threshold correlated with neurologic changes in awake patients undergoing CEA using cervical block anesthesia (CBA) and performed a cost comparison with EEG monitoring.
Patients and Methods: Between July 1, 1995-August 30, 2004, SP was measured during 469 CEAs using CBA with a 19-gauge butterfly needle inserted into the common carotid artery. A saline-filled IV bag in the patient’s contralateral hand was connected to pressure tubing to generate waveforms with hand squeezing that could be visualized on a monitor. Systemic pressure was maintained at approximately 10 mm Hg higher than baseline. Selective shunting was performed only when neurologic changes occurred (aphasia, inability to squeeze the contralateral hand, decreased consciousness).
Results: Shunting was necessary in 6.2% (29/469) of CEAs performed using CBA: 0.3% (1/328) of patients with SP > 50 mm Hg vs. 21% (30/141) with SP < 50 mm Hg. Of note, 0.5% (2/399) of patients with SP > 40 mm Hg required shunting vs. 35% (25/70) with SP < 40 mm Hg. In patients not shunted, the perioperative stroke-death rate was 1.2% (4/327) in patients with SP > 50 mm Hg and 1.0% (4/397) in patients with SP > 40 mm Hg; all events occurred more than 24 hours postoperatively which suggested these were not ischemic events. There was no significant difference in the percentage of patients with SP > 50 mm Hg who underwent CEA using CBA (70%, 328/469) vs. general anesthesia (GA) (68%, 88/130) during this time period. Charges for EEG monitoring including technical fees and interpretation during CEA at our hospital are $3,439 vs. $229 for anesthesia charges and tubing for SP measurements. Use of SP measurements would have resulted in reduced charges of 1.5 million dollars compared to EEG monitoring during CEA in these 469 patients at our hospital.
Conclusion: Stump pressure > 40 mm Hg systolic should replace EEG monitoring as a more reliable and cost-effective method to predict the need for carotid shunting during CEA under GA. These findings need to be considered when cost comparison is made between CEA and carotid artery stenting.