Hemodynamic stability is paramount during, and after carotid endarterectomy (CEA). Maintenance of cerebral perfusion pressure is required before, and during cross-clamping of the internal carotid artery (ICA) to prevent ischemia. After declamping, arterial hypertension must be avoided to prevent cerebral hyperperfusion syndrome (CHS), a rare, but serious complication after cerebral revascularisation procedures. CHS is associated with increased arterial blood pressure and characterised by headaches, neurological deficits, and seizures not caused by cerebral ischemia.
Recently, our group has demonstrated the significant propofol-sparing effect of the centrally acting alpha agonist dexmedetomidine during CEA. We also found significantly decreased requirements for the vasopressor norepinephrine, which may be well explained by the propofol sparing effect of dexmedetomidine in addition to its peripheral alpha-agonistic action (5).
Dexmedetomidine is known to exert a biphasic effect on arterial blood pressure (ABP); at higher concentrations, or when administered as an intravenous bolus, dexmedetomidine increases vascular resistance via peripheral alpha-adren-ergic receptors. After prolonged administration, and at lower concentrations, its central sympatholytic effects prevail (6-8), which may predispose dexmedetomidine as a well-suited adjunct to general anaesthesia for CEA. Recently, low-dose dexmedetomidine has been found to prevent CHS after stenting of the ICA (9).
In addition to its favorable hemodynamic profile, other beneficial effects of dexmedetomidine for CEA have been reported. Frequently, patients undergoing CEA have suffered recent stroke, which itself represents a high risk of delirium (POD) (10). In 700 elderly patients undergoing non-cardiac interventions8, low-dose dexmedetomidine was found to reduce the incidence of delirium from 23% to 9%. Moreover, there is growing evidence for neuroprotective effects of dexmedetomidine in the context of ischemia and reperfusion5,6 Proposed mechanisms include modulation of neuroinflammation, apoptosis, oxidative stress, and synaptic plasticity via the α2-adrenergic receptor (11).
Our previous study was designed to measure the effects of dexmedetomidine on intraoperative requirements of propofol. While the decreased requirements for norepinephrine were clinically significant, it was not defined as primary outcome measure. Also, most of the parameters have been collected only during the immediate perioperative period. The only assessment on postoperative day 1 was CAM-ICU for delirium.
The main purpose of the present follow-up study is to measure the effects of dexmedetomidine on systemic haemodynamics during, and after CEA, with a particular focus on 1) maintenance of cerebral perfusion pressure before and during cross-clamping of the ICA and 2) maintenance of an upper limit of systolic arterial blood pressure for prevention of CHS.
To evaluate the haemodynamic stability during and after CEA with co-administration of dexmedetomidine compared to a standard therapy.