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CARDIOVASCULAR ANESTHESIA

A Comparison of Dexmedetomidine Versus Conventional Therapy for Sedation and Hemodynamic Control During Carotid Endarterectomy Performed Under Regional Anesthesia

Department of Anaesthesia, St Vincent's Hospital Melbourne, Victoria, Australia

Address correspondence and reprint requests to Craig A McCutcheon, MBBS, FANZCA, Department of Anaesthesia, St Vincent's Hospital Melbourne, PO Box 2900, Fitzroy 3065, Victoria, Australia. Address e-mail to craig.mccutcheon{at}svhm.org.au.

	Abstract

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The properties of dexmedetomidine (DEX) that result in titratable sedation and sympathetic modulation suggest that it would be suitable for use during carotid endarterectomy (CEA) performed under regional anesthesia. We performed a randomized, double-blind study in 56 patients having CEA under regional anesthesia and compared hemodynamic control using DEX versus a conventional sedation technique using midazolam and fentanyl standard (STD). Sedation was titrated to a Ramsay Sedation Score of 2–4 in both groups. The primary outcome was the number of pharmacological interventions required to treat deviations of arterial blood pressure and heart rate outside of predetermined limits. We also compared recovery hemodynamic profiles, patient satisfaction, and adverse cardiac and neurological events. There was no difference in the overall rate of hemodynamic interventions (DEX 80% versus STD 79%; P = 1.0). However, the nature of interventions differed in that patients in the DEX group were less likely to require treatment for hypertension and/or tachycardia (DEX 40% versus STD 72%; P = 0.03). The number of interventions per patient for hypertension and/or tachycardia was also lesser in the DEX group (P = 0.02). There were no significant differences in the numbers of patients needing intraoperative treatment for hypotension or bradycardia or in the need for intraarterial shunting. In the postanesthesia care unit, more patients in the DEX group required hemodynamic drug interventions (DEX 11, 44%, versus STD 4, 14%; P = 0.03). These were primarily for hypotension (DEX 7, 28% versus STD 3, 11%; P = 0.16). The number of patients requiring no additional pain relief in the postanesthesia care unit was significantly larger for patients in the DEX group (DEX 18, 72% versus STD 11, 38%; P = 0.027). DEX provides an acceptable alternative, without superiority to standard techniques for sedation during awake CEA.

	Introduction

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The anesthetic management of patients undergoing carotid endarterectomy (CEA) under regional anesthesia requires attention to the goals of optimizing cerebral perfusion, minimizing cardiac and psychological stress, and maintaining sufficient responsiveness to ensure reliable assessment of cerebral function. The pharmacokinetic and pharmacodynamic properties of dexmedetomidine (DEX) suggest that it may be superior to conventional sedatives and analgesics during CEA under regional anesthesia. These properties include easily rousable sedation without respiratory depression, hemodynamic stabilizing effects (less hypertension and tachycardia), a short half-life enabling titration to effect via an IV infusion, rapid recovery avoiding hangover effects, and production of mild analgesia (1). However, hypotension can occur with its use, and concern has been expressed regarding the potential of DEX to increase the need for temporary shunting during CEA (2).

DEX is an -2 adrenoceptor agonist that is 8 times more specific than clonidine (3). It has both sedative and sympatholytic properties without inducing respiratory depression and has been used effectively in the intensive care environment to aid weaning from mechanical ventilation in cardiac surgical patients (4). Alternative sedation techniques using combinations of propofol, benzodiazepines, and opioids are often difficult to titrate and may induce respiratory depression. We therefore decided to investigate, in a prospective double-blind randomized controlled trial, whether DEX could provide effective sedation as well as greater hemodynamic stability than a conventional sedation regimen that comprised a mixture of midazolam and fentanyl.

	Methods

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After institutional ethics committee approval, written informed consent was obtained from patients presenting for CEA under regional anesthesia. Exclusion criteria were baseline heart rate (HR) < 50 bpm, second or third degree heart block, uncontrolled cardiac failure, allergies to study medications or contraindications to regional anesthesia. Patients continued to take their normal antihypertensive medications, including ß-adrenergic blockers, both on the day of surgery and throughout the perioperative period.

All patients were premedicated with oral temazepam 10 mg 1 h before the procedure. On arrival in the operating suite, 5-lead electrocardiogram (ECG) monitoring was commenced and IV access and radial intraarterial pressure monitoring were established. Arterial blood was sampled for Paco₂ and troponin I levels. All hemodynamic data were continuously acquired using an electronic data acquisition device (Powerlab®; AD Instruments, Castle Hill, NSW, Australia). All patients received oxygen at 6 L/min via facemask.

Patients were allocated to treatment group using computer-generated permuted block randomization by sealed envelopes opened by an independent anesthesiologist once the patient had arrived in the operating room. There were five surgeons who took part in this study. Randomization was stratified to ensure that one particular vascular surgeon who performs the majority of CEA was allocated equal numbers of patients from both groups. He was the responsible surgeon for 34 of the 56 patients recruited. To facilitate blinding, two syringes of "study drug" were prepared for each patient by an anesthesiologist not associated with the study and labeled "Infusion" and "Bolus top-up." One syringe of each pair contained active sedative drug(s); the other contained placebo (saline). Patients in the "Standard Sedation" (STD) group received a 10-mL "Bolus" syringe containing 20 µg/mL fentanyl and 0.5 mg/mL midazolam and a 50 mL "Infusion" syringe containing placebo that was run via infusion through a Graseby 3400 syringe driver (Watford, UK). Patients in the DEX group received a 50 mL "Infusion" syringe containing 4 µg/mL DEX as well as a 10 mL placebo "Bolus" syringe. Sedation was initiated as follows:

Dex Group:

–Initial loading dose of DEX (0.5 µg/kg) over 10 min followed by infusion at 0.2 µg · kg^–1 · h^–1 from the 50-mL "Infusion" syringe.

–2 mL placebo bolus from the 10-mL "Bolus" syringe.

STD group:

–2 mL bolus from the 10 mL "Bolus" syringe (40 µg fentanyl and 1 mg midazolam)

–Initial loading dose plus infusion of placebo from 50 mL "Infusion" syringe at a corresponding rate to the DEX group.

These doses were selected by consensus of the investigators on the basis of previous experience using these drugs for carotid surgery under regional anesthesia.

Level of sedation throughout the procedure was assessed using the Ramsay Sedation Score (RSS) (5) (1 = anxious and agitated, restless; 2 = cooperative, oriented, tranquil; 3 = responsive to verbal commands, drowsy; 4 = "asleep," responsive to light stimulation [loud noise, tapping]; 5 = asleep, slow response to stimulation; 6 = no response to stimulation). The aim was to maintain the patient in the range of 2–4 (i.e., readily rousable at all times). If required, the level of sedation was increased by administering 1 mL from the "Bolus" syringe (STD group: 0.5 mg midazolam plus 20 µg fentanyl) and by increasing the infusion rate from the 50-mL "Infusion" syringe (DEX group: 0.1 µg · kg^–1 · h^–1) to a maximum dose of 0.8 µg · kg^–1 · h^–1. Corresponding volumes of placebo drug were administered from the alternate syringe. The level of sedation could be decreased by reducing the infusion rate by 0.1 µg · kg^–1 · h^–1 increments. Administration of sedative drugs was ceased at the end of the case.

After initiation of sedation, the operative site was anesthetized with deep and superficial cervical plexus blocks using equal volumes of 1.5% lidocaine with adrenaline 1:200,000 and 0.75% ropivacaine. The blocks were performed by, or under the supervision of, 10 anesthesiologists with experience in the performance of cervical plexus blocks (6). The total volume of local anesthetic used was at the discretion of the treating anesthesiologist within the range of 30–40 mL. Adequacy of the cervical plexus blocks was not documented preoperatively; however, additional lidocaine 0.5% administered by the surgeon to treat intraoperative pain was recorded.

The primary outcome variable was the number of pharmacological interventions required to treat deviations of systolic blood pressure (BP) or HR outside predetermined limits. Baseline BP and HR were taken from the patients’ attendance at a preoperative clinic in the weeks preceding surgery. Systolic BP was to be maintained within 30% of baseline as well as within the absolute limits of 100–180 mm Hg. HR was also maintained within 30% of baseline and within the absolute limits of 45–100 bpm. There were no specific additional hemodynamic goals during the time of carotid cross-clamping. Hypotension was treated with a vasopressor (metaraminol or ephedrine) or an IV fluid bolus, bradycardia with a chronotrope (glycopyrrolate or atropine) or ephedrine, hypertension with a ß-adrenergic blocker (atenolol or metoprolol) or an IV infusion of glyceryl trinitrate, and tachycardia with a ß-adrenergic blocker. All of these drugs were administered in doses consistent with clinical practice. The number of interventions and doses of individual drugs were recorded.

The effect of sedation on ventilation was assessed by comparing Paco₂ recorded before commencement of sedation to the level recorded 45 min after the performance of the cervical plexus blocks.

During the procedure the RSS and the patient's verbal pain scores (VPS) (0 = no pain to 10 = worst pain) were recorded every 30 min and at the time of carotid artery cross-clamping. Shunting was indicated when there was a clear decline in neurological performance, as assessed by grip strength in the contralateral hand and by the patient's ability to maintain verbal communication during the period of carotid clamping. Cross-clamp time, surgical blood loss, and intraoperative complications were also documented. At the completion of surgery the surgeon who was blinded as to treatment group was asked to rate the quality of operative conditions on a verbal scale from 0 to 10 (0 = poor to 10 = excellent). Electroencephalogram and stump pressures were not recorded.

On the completion of surgery, patients were transferred to the postanesthesia care unit (PACU), where nursing staff recorded hemodynamic variables and Spo₂ every 10 min and RSS every 30 min until discharged to the ward. Requirements for hemodynamic, analgesic, and antiemetic medications were documented. Although there were no study stipulations on the administration of these drugs, the PACU staff members were blinded as to treatment group and used routine indications. The time taken to reach readiness for discharge to the ward according to the standard PACU requirements (hemodynamically stable, adequate analgesia, RSS 4 or less) was recorded.

The following day, using a questionnaire, patients assessed their overall level of satisfaction, recall of perioperative events, and whether they would have the same anesthetic technique were they to require the procedure again in the future. They were also assessed for cardiac events by clinical history, 12-lead ECG, and troponin I levels at 24 h. Neurological events (transient ischemic attack, cerebrovascular accident) or diagnosis of myocardial infarction (made by surgical unit) were recorded up to hospital discharge.

Intraoperative and PACU data were recorded by blinded operating room nurses not associated with the study, and the postoperative questionnaire and postoperative clinical assessments were made by the first two authors of the study who were blinded as to treatment group allocation.

Data were compared using Student's t-test for continuous variables and ² or Fishers’ exact test for categorical data. Ranked categorical data were analyzed using the Mann-Whitney U-test. A P value of <0.05 was considered statistically significant. The primary outcome of the study was the number of pharmacological treatments required to treat changes of HR or BP outside of predetermined limits. Based on previous studies of CEA performed within our institution, (6,7) a sample size of 56 patients would be required to show a two-thirds reduction in the number of hemodynamic interventions with power of 0.8 and = 0.05. Statview Software (Version 4.0; Abacus Concepts, CA) was used to perform the analyses.

	Results

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In the 13-mo period from March 2003, 74 patients presented to our institution for CEA. Eighteen patients were not recruited for logistical reasons, predominantly that one of the major investigators was not available to coordinate enrollment in the study. Of the 56 patients who were enrolled in the study, 54 were included in the analysis, with 25 in the DEX group and 29 in the STD group. There were two withdrawals after randomization, both from the DEX group: One patient's surgery was cancelled because of severe preoperative hypertension (preoperative systolic BP was 210 mm Hg, increasing to 240 mm Hg after commencement of the initial dose); the other patient was cancelled after the forearm into which the DEX was being infused became cold and pale with concern from the surgeon that the patient's hand might become ischemic, although distal pulses were present and the hand appeared normal. Both of these patients had uneventful procedures on a subsequent occasion. Demographic and preoperative data are shown in Table 1 and the intraoperative data in Table 2. There were no differences between groups with regard to demographics or intraoperative measures of blood loss, volume of supplemental lidocaine, or the surgeon's rating of operating conditions.

The overall number of patients requiring hemodynamic interventions was similar between groups, with 80% of DEX patients and 79% of STD patients requiring at least one intervention. There were however, differences in the nature of interventions required (Table 3). Significantly fewer patients required intervention for hypertension and/or tachycardia in the DEX group than the STD group (DEX 40% versus STD 72%, P = 0.03). The number of interventions required per patient for these conditions was also smaller in the DEX group (Fig. 1a; P = 0.02). Although fewer patients in the DEX group required treatment for hypertension per se, this difference was not significant (P = 0.06).

View larger version (21K): [in this window] [in a new window]   Figure 1. a. Number of hemodynamic interventions per patient for hypertension and/or tachycardia. DEX = dexmedetomidine group; STD = standard group; P = 0.02. b. Number of hemodynamic interventions per patient for hypotension and/or bradycardia. P = 0.27.

There were no significant differences in the numbers of patients needing treatment interventions for hypotension or bradycardia (Table 3) or in the number of interventions required per patient (Fig. 1b).

Sedation was effectively titrated to the target RSS range of 2–4 in both groups, with 98% of all recorded RSS being within this range. The DEX group had a larger proportion of RSS = 4 (DEX 20.7% versus STD 8.0%; P = 0.03) whereas the STD group tended to have a larger proportion of RSS = 2 (DEX 65.3% versus STD 84.7%; P = 0.1).

There was no statistically significant difference between groups with regards to the effect of sedation on Paco₂; the increase of Paco₂ at 45 min was 2.2 ± 0.7 mm Hg (DEX) and 3.5 ± 0.9 mm Hg (STD), respectively (mean ± se; P = 0.26).

VPS were not significantly different between groups (P = 0.86). Overall, VPS were 4 or less on 79% of occasions.

In the PACU, patients in the DEX group had significantly lower systolic BP (P = 0.02) than the STD group for the first 5 of the 10-min assessments, and slower HR (P = 0.01) for 7 of the first 8 assessments (Figure 2). More patients in the DEX group required hemodynamic drug interventions in the PACU (DEX 11, 44% versus STD 4, 14%; P = 0.03). These were primarily for hypotension (DEX 7, 28% versus STD 3, 11%; P = 0.16), and all responded to ephedrine.

View larger version (25K): [in this window] [in a new window]   Figure 2. a. Postoperative systolic blood pressure. b. Postoperative heart rate. BP = systolic blood pressure; PACU = postanesthesia care unit; DEX = dexmedetomidine group; STD = standard group; *P < 0.05.

Analgesic requirements were increased in PACU for patients in the STD group (morphine: DEX 3, 12% versus STD 12, 43%; P = 0.016). The number of patients requiring no additional pain relief in PACU was significantly larger in the DEX group. (DEX 18, 72% versus STD 11, 38%; P = 0.027). There was a trend toward reduced requirements for antiemetic medications in the DEX group; however, this was not statistically significant (DEX 0, 0% versus STD 4, 14%; P = 0.11). The time between admission to PACU and readiness for discharge was similar in both groups. (DEX 97.3 ± 7.7 min, STD 102.9 ± 9.6 min; P = 0.66).

The postoperative questionnaire revealed no statistically significant differences between groups. Overall patient satisfaction was high; the number of patients reporting being satisfied or very satisfied was DEX 20 (80%) versus STD 28 (97%) (P = 0.08), with one patient in the STD group being very dissatisfied and 5 patients in the DEX group being either dissatisfied or neither satisfied nor dissatisfied. There was no difference between groups in terms of the proportion of patients who reported feeling some discomfort during the procedure (DEX 18, 72% versus STD 16, 55%; P = 0.39) or in those who tended to prefer an awake procedure were they to require a repeat operation (DEX 20, 80% versus STD 26, 90%; P = 0.24).

The postoperative assessment for cardiac events up to 24 h showed that the majority of patients tolerated the procedure without incident. Only one patient (STD group) described a period of chest pain and shortness of breath during this time. These symptoms were consistent with the patient's normal pattern of angina and were promptly relieved with his normal antianginal medication. Three patients had increases in their 24-h troponin I levels. Two of these patients (STD 1, DEX 1) had small asymptomatic increases (troponin I 0.2 and 0.4 mmol/L; normal value <0.16 mmol/L). They were reviewed by members of the cardiology unit but required no specific alteration to management. The third patient with an increase of serum troponin I (STD group – level 9.2 mmol/L) had known triple coronary vessel disease and was scheduled for coronary artery bypass surgery after correction of his tight carotid stenosis. During the CEA he became tachycardic and developed pulmonary edema requiring conversion to general anesthesia with tracheal intubation and inotropic support. On completion of the CEA he underwent immediate cardiac surgery and was managed postoperatively in the intensive care unit (ICU). This patient was excluded from the PACU data analysis, the intraoperative data and late postoperative follow-up was retained. He was the only patient in the study to develop postoperative ECG changes. He was discharged well 1 wk later. There were no additional late neurological or cardiac complications identified before discharge.

Three patients (DEX 1, STD 2) became unconscious within 2 min of carotid cross-clamping and required shunt insertion to restore ipsilateral cerebral blood flow.

One patient (DEX group) required reoperation for neck swelling as a result of bleeding from the operative site. One patient (DEX group) developed a self-limiting period of second degree heart block in the recovery room that was associated with bradycardia (35 bpm) and some cerebral dysfunction (agitation), both of which responded to treatment with ephedrine and glycopyrrolate.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
This study shows that DEX, used as an infusion during CEA performed under regional anesthesia, is associated with less intraoperative and postoperative hypertension and tachycardia while maintaining similar degrees of sedation when compared with a conventional sedative technique. Both techniques provided satisfactory levels of sedation. Postoperatively, episodes of hypotension and bradycardia were more common in the first postoperative hour in the DEX-treated patients.

We were unable to detect a significant difference in the overall rate of hemodynamic interventions when comparing DEX to midazolam/fentanyl; however differences in the indications for these interventions were significant. In particular, patients in the DEX group were less likely to require treatment for hypertension and/or tachycardia (DEX 40%, STD 72%; P = 0.03), an effect that persisted for up to 70 minutes into the postoperative recovery period. This presumably reflects the action of DEX on central -2 adrenoceptors resulting in a reduction of sympathetic tone and lower catecholamine levels (3,8).

Others have reported similar depressant hemodynamic effects as in our study (8,9). There was a tendency for more patients in the DEX group to require treatment for hypotension both intraoperatively (DEX 14 patients, STD 12 patients) and postoperatively (DEX 7 patients, STD 3 patients); however, these results were not statistically significant. Despite DEX patients experiencing more perioperative hypotension and bradycardia and STD patients more hypertension and tachycardia, the infrequent rate of ischemic cardiac events overall (4 patients, 2 with small troponin increases only) does not make it possible to draw any conclusions regarding an effect of treatment group on cardiac morbidity.

Overall, patients were sedated to the target level for more than 98% of all recordings. This contrasts with the results of Bekker et al. (8), in which only 3 of 62 patients undergoing CEA under regional anesthesia were sedated to the appropriate level at each of their measurement points, although the authors concluded that DEX was superior to their control group. The reason for this large discrepancy may relate to the systems used for assessment of sedation and the level of sedation deemed desirable. Bekker et al. (8) used the Observer's Assessment of Alertness-Sedation and targeted a level of 4 (lethargic response to name, mild slowing of speech), whereas we used the RSS with a broader range of sedation as being acceptable (RSS 2–4). We chose to use the RSS because this scoring system was used in several published articles concerning DEX (4,10–12) and seemed particularly appropriate for CEA. Furthermore, this range of acceptable sedation scores considers the distinctive character of sedation with DEX, in which patients in the unstimulated state appear asleep with their eyes closed but can be reliably roused with a clear sensorium using verbal stimulation (RSS = 4) (1). Although we detected no differences in the overall rate of acceptable sedation between study groups, patients receiving DEX had a larger proportion of RSS = 4.

In the study of Bekker et al. (8) the finding of a frequent requirement for carotid artery shunting during surgery in DEX-sedated patients (19% versus 6%) raised concerns, with conjecture that an effect of DEX in reducing cerebral blood flow may have influenced this outcome (2). Importantly, however, the actual number of patients needing shunts in Bekker et al.'s study (8) was small, and the difference was not statistically significant. In our study, only 3 patients required shunting (1, 4% DEX and 2, 8% STD), which was in response to a clear change in conscious state after clamping. A study of at least 240 patients would be required to confirm the effect reported by Bekker et al. if the incidence of shunting remains the same; indeed our baseline rate was similar. Based on clinical end-points, we therefore cannot support the conclusion that DEX adversely affects cerebral perfusion in these patients.

There were no differences between groups in terms of intraoperative VPS, possibly reflecting the appropriate titration of the two sedation regimes used. Postoperatively, however, the analgesic effects of DEX resulted in a significantly smaller need for supplemental analgesics in the PACU compared with STD, despite the fact that fentanyl was included in the standard mixture. This presumably reflects a persisting action of DEX on spinal cord -2 adrenoceptors (4,13). Also, pain experienced by the patients in the DEX group was more likely to be controlled using "simple" analgesics (acetaminophen, codeine, tramadol) than was pain in the STD group patients, who had larger requirements for parenteral morphine. We did not specifically assess the ward requirements for analgesia, however satisfaction scores assessed on postoperative day 1 did not reveal any significant difference between the groups.

The postoperative questionnaire revealed a trend towards patients in the DEX group reporting recall of intraoperative discomfort and less frequently requesting an awake technique for a repeat procedure. Although there may be a number of reasons for this trend, the lack of amnesic effects with small concentrations of DEX (14) may enable patients to better remember any discomfort associated with surgery despite similar levels of sedation to the STD group, in whom the midazolam may have blunted recall of intraoperative events. Venn (4) reported that a number of patients receiving DEX for ICU sedation found the experience particularly stressful despite their apparent comfort and ease of management by ICU staff. The ideal sedation technique for CEA under regional anesthesia, therefore, may combine the amnesic properties of small doses of a benzodiazepine together with DEX's beneficial properties.

There are potential side effects associated with the use of DEX, as evidenced by the patients who were withdrawn from the study. DEX may cause a transient increase in BP with initial administration, an effect related to the drug's action on peripheral receptors. In the patient who developed the pale forearm, we are uncertain as to the exact cause of this reaction. The fact that this reaction occurred in the arm into which the DEX was being infused, was temporally related to the commencement of the initial loading dose, and resolved without specific treatment after cessation of the drug's administration raises concern that this reaction was related to DEX. We postulate that retrograde flow of DEX through the superficial venous system of the forearm resulted in transient venoconstriction and resulting pallor but no discomfort to the patient. Nonetheless, despite confirmation that the infusion was not intraarterial it was decided that the response was sufficiently unusual to warrant withdrawal from the investigation at this point before surgery commencing.

Based purely on the number of hemodynamic interventions, it is difficult to justify the 17-fold cost differential between the 2 drug regimes at our institution (DEX 200 µg/mL ampoule = $48 AUD, fentanyl 200 µg, and midazolam 5 mg = $2.73AUD). However, this increased cost must be weighed against the lesser requirements for analgesics (and possibly antiemetics) in the PACU.

There were a number of limitations related to this study. Variability of the success of the cervical plexus blocks may have influenced the amount of discomfort experienced, and subsequently the hemodynamic profiles exhibited by the patients. However, intraoperator and interoperator variability was likely to be similar because of the experience of the anesthesiologists performing the blocks (6). Another reason for variations in the level of patient comfort is the surgical complexity of the operative carotid lesion. Because patients with high carotid lesions present a greater technical challenge to the surgeon, these patients tend to experience more discomfort, which is associated with the placement of surgical retractors high in the neck outside the territory anesthetized with the cervical plexus blocks. We did not specifically assess these surgical details.

HR of 100 bpm is possibly too rapid for vascular surgical patients with a frequent incidence of concomitant heart disease. However for most patients in this study, the upper limit of acceptable HR was 30% above their baseline BP (average baseline HR was 69 bpm), with the absolute value of 100 bpm to cover patients with more rapid resting HR in whom a 30% increase would have exceeded this limit. It is possible that a lower limit for acceptable HR would have increased the observed differences between these groups with regards to the number if interventions for tachycardia considering the sympatholytic profile of DEX.

Our study was not adequately powered to detect differences between groups in the incidence of cardiac or neurological events. Although a study of several hundred patients would be required to show a difference with regard to these uncommon events, we felt it was important to document that patients sedated using this novel technique did not have an overtly frequent incidence of such complications.

As an outcome variable, the number of hemodynamic interventions may be considered to lack clinical relevance, especially considering we were unable to demonstrate an overall difference between groups. However, our study has shown that there is a difference in the nature of hemodynamic interventions required, highlighting the sympatholytic profile of DEX in this patient population.

In conclusion, we found that DEX, when used for sedation during CEA under regional anesthesia, provided reliable and titratable sedation. It produced mild analgesic effects that decreased analgesic requirements postoperatively and had a hemodynamic profile characterized by moderate reductions of HR and BP that persisted into the postoperative period. These characteristics are desirable in patients undergoing CEA who have more frequent coronary artery disease and are at greater risk for perioperative myocardial ischemia than the general population. However the potential for hypotension and bradycardia when using DEX in these patients highlights the need for vigilant hemodynamic monitoring throughout the perioperative period.

	Footnotes

 
Supported, in part, by a research grant from the Australian Society of Anaesthetists.

Accepted for publication October 25, 2005.

	References

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