Effects of bilateral stellate ganglion block on autonomic cardiovascular regulation

Establishment of stellate ganglion block in mice

BACKGROUND

There have been no reports on the successful implementation of stellate ganglion block (SGB) in mice.

OBJECTIVES

This study aims to investigate a new method for implementing SGB in mice by placing them in a supine position with abducted upper limbs and touching the trachea and sternoclavicular joint with the hand.

METHODS

Fifty BABL/C mice, 8-10 weeks, were selected and randomly divided into four groups: control group (n = 5); SGB-R group (n = 15); SGB-L group (n = 15); and SGB-L + R (group n = 15). SGB was administered with 0.15% ropivacaine solution in a volume of 0.1 mL. The control group received equal volumes of saline. Horner's syndrome, heart rate, and complications such as brachial plexus block, vascular injury, pneumothorax, local anesthetic toxicity, and death were observed.

RESULTS

Horner's syndrome developed in 100% of SGB surviving mice; no difference was seen in the time to onset (100.4 ± 13.4 vs 96.7 ± 12.4, mean ± SD, seconds) and duration (264.1 ± 40.5 vs 296.3 ± 48.0, mean ± SD, min) of Horner's syndrome in the left and right SGB (P > 0.05). Compared with the control group (722 [708-726], median [IQR], bpm), the heart rate was significantly slowed down in the right SGB (475 [451.5-491], median [IQR], bpm) (P < 0.05). While the heart rate was slowed down after performing the left SGB, the difference was not statistically significant (P > 0.05). The overall complication rate was 18.4%, with a brachial plexus block rate of 12.3%, a vascular injury rate of 4.6%, and a mortality rate of 1.5%, as well as no local anesthetic toxicity (includes bilateral implementation of SGB) or pneumothorax manifestations were found.

CONCLUSIONS

This method allows for the successful implementation of SGB in a mouse model.

Cardiovascular dysautonomia in postacute sequelae of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) has led to a worldwide pandemic that continues to transform but will not go away. Cardiovascular dysautonomia in postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection has led to persistent symptoms in a large number of patients. Here, we define the condition and its associated symptoms as well as potential mechanisms responsible. We provide a careful and complete overview of the topic addressing novel studies and a generalized approach to the management of individuals with this complex and potentially debilitating problem. We also discuss future research directions and the important knowledge gaps to be addressed in ongoing and planned studies.

Sympathetic nerve blocks for posttraumatic stress disorder: an evidentiary review for future clinical trials

Posttraumatic stress disorder (PTSD) is a chronic disorder resulting from exposure to traumatic events. In recent years, sympathetic nerve blocks have gained interest as an emerging treatment modality for PTSD. They have been shown to reduce autonomic dysfunction associated with PTSD symptoms, particularly in refractory and treatment-resistant patients. However, there is limited evidence regarding the technique's effectiveness in PTSD patients. Therefore, this scoping review was designed to update and summarize the current literature on this topic to inform the design of future clinical trials and studies. Our review of 22 studies (mostly case reports and series) included 1,293 PTSD patients who received sympathetic nerve blocks, primarily military service members and veterans, with a median age of 42.2 years. 0.5% Ropivacaine was the preferred anesthetic, and the right sided stellate ganglion block was the most commonly used technique. Relapse of symptoms was reported commonly, resulting in additional nerve block sessions. Most reported side effects were mild and transient. Despite the encouraging results, we remain cautious in interpreting the benefit of the technique due to the lack of sufficient standardized clinical trial data, heterogeneity in reported results, and the potential for bias in reporting. Future studies should focus on evaluating and addressing the technique's effectiveness, safety, tolerability, and indications.

Percutaneous cervical sympathetic block to treat cerebral vasospasm and delayed cerebral ischemia: a review of the evidence

Delayed cerebral ischemia (DCI) affects 30% of patients following aneurysmal subarachnoid hemorrhage (aSAH) and is a major driver of morbidity, mortality, and intensive care unit length of stay for these patients. DCI is strongly associated with cerebral arterial vasospasm, reduced cerebral blood flow and cerebral infarction. The current standard treatment with intravenous or intra-arterial calcium channel antagonist and balloon angioplasty or stent has limited efficacy. A simple treatment such as a cervical sympathetic block (CSB) may be an effective therapy but is not routinely performed to treat vasospasm/DCI. CSB consists of injecting local anesthetic at the level of the cervical sympathetic trunk, which temporarily blocks the innervation of the cerebral arteries to cause arterial vasodilatation. CSB is a local, minimally invasive, low cost and safe technique that can be performed at the bedside and may offer significant advantages as complementary treatment in combination with more conventional neurointerventional surgery interventions. We reviewed the literature that describes CSB for vasospasm/DCI prevention or treatment in humans after aSAH. The studies outlined in this review show promising results for a CSB as a treatment for vasospasm/DCI. Further research is required to standardize the technique, to explore how to integrate a CSB with conventional neurointerventional surgery treatments of vasospasm and DCI, and to study its long-term effect on neurological outcomes.

Stellate ganglion block catheter for paroxysmal sympathetic hyperactivity: calming the 'neuro-storm'

BACKGROUND

Paroxysmal sympathetic hyperactivity (PSH) is an autonomic disorder affecting patients with severe acquired brain injury characterized by intermittent sympathetic discharges with limited therapeutic options. We hypothesized that the PSH pathophysiology could be interrupted via stellate ganglion blockade (SGB).

CASE PRESENTATION

A patient with PSH after midbrain hemorrhage followed by hydrocephalus obtained near-complete resolution of sympathetic events for 140 days after SGB.

CONCLUSION

SGB is a promising therapy for PSH, overcoming the limitations of systemic medications and may serve to recalibrate aberrant autonomic states.

Cervical Ganglion Sympathectomy to Treat Cerebral Vasospasm in Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) is still a significant cause of death and disability after aneurysmal subarachnoid hemorrhage. Cerebral vasospasm represents one of the most reported mechanisms associated with DCI. The management of DCI-related vasospasm remains a significant challenge for clinicians; induced hypertension, intraarterial vasodilators, and/or intracranial vessel angioplasty-particularly in refractory or recurrent cases-are the most used therapies. Because an essential role in the pathophysiology of cerebral vasospasm has been attributed to the adrenergic sympathetic nerves, a "sympatholytic" intervention, consisting of a temporary interruption of the sympathetic pathways using local anesthetics, has been advocated to minimize the vascular narrowing and reverse the consequences of cerebral vasospasm on tissue perfusion. In this review, we have analyzed the existing literature on the block of the cervical ganglions, particularly the stellate ganglion, in managing refractory cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage. These findings could help clinicians to understand the potential role of such intervention and to develop future interventional trials in this setting.

Safety and utility of ultrasound-guided superior cervical ganglion block for headaches and orofacial pain: a retrospective, single-center study of 10 patients

BACKGROUND

Several new ultrasound-guided superior cervical ganglia blocks (U-SCGBs) have been proposed to overcome the shortcomings of conventional superior cervical ganglia blocks; however, their clinical utility and practicality have not yet been demonstrated. The aim of this study was to evaluate the safety and utility of a new method of U-SCGB.

METHODS

We retrospectively collected data on patients who underwent U-SCGB for the treatment of headaches and orofacial pain at a single center. U-SCGB was performed by injecting 2-3 mL of 1% mepivacaine posterior to the internal carotid artery, just above the bifurcation. The Wilcoxon signed-rank test was used to compare pain scores. Numerical data are expressed as the mean ± standard error.

RESULTS

The total number of U-SCGB procedures was 43. All procedures were accompanied by Horner's sign. The numerical rating scale score for pain (possible scores, 0-10) was reduced predominantly from 7.0 ± 0.7 before treatment to 4.5 ± 0.7 at the follow-up (p = 0.014).

CONCLUSION

U-SCGB was considered a clinically useful and accurate treatment for headaches and orofacial pain in this study.

A Novel Somatic Treatment for Post-traumatic Stress Disorder: A Case Report of Hydrodissection of the Cervical Plexus Using 5% Dextrose

Despite years of standard treatments, a Marine veteran and former firefighter, disabled due to severe post-traumatic stress disorder (PTSD), worsened over ten weeks while receiving usual care. Bilateral injection of 10 mL of 5% dextrose in water using a 30-gauge needle just under the sternocleidomastoid muscle was performed at weeks 10, 12, 14, 16, and 18. Clinically important improvements were observed by 18 weeks on a 0-10 anxiety rating scale (57%), the PTSD checklist for civilians (41%), EuroQol overall quality of life scale (40%), and the Hospital Anxiety and Depression Scale (28%). Improvements were stable through 22 weeks. He reported symptomatic benefit on anxiety within 20 minutes of injection, suggesting a neurogenic mechanism, potentially related to a therapeutic effect on the nearby sympathetic trunk/superior sympathetic ganglion. Advantages of this procedure over stellate ganglion blockade include its safety (no lidocaine), bilateral treatment option, simplicity, and comfort.

Decrease of blood flow velocity in the middle cerebral artery after stellate ganglion block following aneurysmal subarachnoid hemorrhage: a potential vasospasm treatment?

OBJECTIVE

Cerebral vasospasm (CV) is a delayed, sustained contraction of the cerebral arteries that tends to occur 3-14 days after aneurysmal subarachnoid hemorrhage (aSAH) from a ruptured aneurysm. Vasospasm potentially leads to delayed cerebral ischemia, and despite medical treatment, 1 of 3 patients suffer a persistent neurological deficit. Bedside transcranial Doppler (TCD) ultrasonography is used to indirectly detect CV through recognition of an increase in cerebral blood flow velocity (CBFV). The present study aimed to use TCD ultrasonography to monitor how CBFV changes on both the ipsi- and contralateral sides of the brain in the first 24 hours after patients have received a stellate ganglion block (SGB) to treat CV that persists despite maximum standard therapy.

METHODS

The data were culled from records of patients treated between 2013 and 2017. Patients were included if an SGB was administered following aSAH, whose CBFV was ≥ 120 cm/sec and who had either a focal neurological deficit or reduced consciousness despite having received medical treatment and blood pressure management. The SGB was performed on the side where the highest CBFV had been recorded with 8-10 ml ropivacaine 0.2%. The patient's CBFV was reassessed after 2 and 24 hours.

RESULTS

Thirty-seven patients (male/female ratio 18:19), age 17-70 years (mean age 49.9 ± 11.1), who harbored 13 clipped and 22 coiled aneurysms (1 patient received both a coil and a clip, and 3 patients had 3 untreated aneurysms) had at least one SGB. Patients received up to 4 SGBs, and thus the study comprised a total of 76 SGBs.After the first SGB, CBFV decreased in 80.5% of patients after 2 hours, from a mean of 160.3 ± 28.2 cm/sec to 127.5 ± 34.3 cm/sec (p < 0.001), and it further decreased in 63.4% after 24 hours to 137.2 ± 38.2 cm/sec (p = 0.007). A similar significant effect was found for the subsequent SGB. Adding clonidine showed no significant effect on either the onset or the duration of the SGB. Contralateral middle cerebral artery (MCA) blood flow was not reduced by the SGB.

CONCLUSIONS

To the authors' knowledge, this is the largest study on the effects of administering an SGB to aSAH patients after aneurysm rupture. The data showed a significant reduction in ipsilateral CBFV (MCA 20.5%) after SGB, lasting in about two-thirds of cases for over 24 hours with no major complications resulting from the SGB.

Acute hemodynamics of cardiac sympathetic denervation

INTRODUCTION

We aimed to study the immediate hemodynamic effects of thoracoscopic bilateral cardiac sympathetic denervation (CSD) for recurrent ventricular tachycardia (VT) or VT storm.

METHOD

We studied a group of 18 adults who underwent bilateral thoracoscopic CSD; the blood pressure (BP) and Heart Rate (HR) were continuously monitored during the surgery and up to 6 h post-operatively.

RESULTS

Immediately on removal of the sympathetic ganglia, the patients had a drop in both the systolic (110 mm Hg to 95.8 mm Hg, p < 0.001) and diastolic BP (69.4 mm Hg to65 mm Hg, p = 0.007) along with a drop in the HR (81.6 bpm to 61.2 bpm, p < 0.001).At 6 h after CSD, the systolic and diastolic BP did not recover significantly, while there was recovery in HR (61.2 bpm to 66 bpm, p = 0.02). There was no significant difference between those with and without left ventricular (LV) systolic dysfunction.

CONCLUSION

The acute hemodynamic changes during the perioperative period of CSD are significant but not serious. Awareness of this is useful for peri-operative management.

Bilateral superior cervical ganglionectomy attenuates the progression of β-aminopropionitrile-induced aortic dissection in rats

AIMS

Aortic dissection (AD) represents one of the most common aortic emergencies with high incidence of morbidity and mortality. Clinical studies have shown that the increased excitability of the sympathetic nerve may be associated with the formation of AD. In this study, we examined the effects of bilateral superior cervical sympathectomy (SCGx) on the progression of β-aminopropionitrile (BAPN)-induced AD in rats.

MAIN METHODS

Sprague-Dawley rats were randomly divided into three groups, including BAPN, BAPN+SCGx and control groups. For terminal measurements, the mean arterial pressure (MAP) and heart rate (HR) were monitored and the basal sympathetic nerve activity (SNA) was assessed through recording the variation in arterial pressure in response to hexamethonium application. Pathological changes in the aortic wall were observed by histological staining. Matrix metalloproteinase-2 (MMP-2) and MMP-9 concentrations within the aortic wall were analyzed by western blot.

KEY FINDINGS

The results show that BAPN administration could elevate SNA and cause the formation of AD in rats with a high incidence (67.7%), while SCGx treatment inhibited the elevation of SNA and significantly reduced the incidence (20%). SCGx may suppress the formation of BAPN-induced AD via restraining the rise of HR and reducing the MMP-9 concentration in aortic wall.

SIGNIFICANCE

These results indicate that surgical techniques such as sympathetic nerve block may be a potentially useful therapy for the prevention of AD.

Effects of Linearly Polarized Near-Infrared Irradiation Near the Stellate Ganglion Region on Pain and Heart Rate Variability in Patients with Neuropathic Pain

Background

Neuropathic pain associated with sympathetic overactivity can be effectively relieved by light irradiating the region near stellate ganglion (SGI), applied as an alternative to a conventional sympathetic blockade. The clinical effect of SGI on heart rate variability (HRV) and its association with pain outcomes require investigation.

Objective

This study attempted to identify the effects of SGI on pain outcomes and HRV indices and to determine the association between pain and HRV outcomes.

Design

A prospective double-blind, randomized study.

Setting

An outpatient pain medicine clinic.

Subjects and Methods

A total of 44 patients were enrolled and randomized into the experimental group ( n = 22) and control group ( n = 22). The experimental group received 12 sessions (twice weekly) of standard SGI, whereas the control group received the same protocol with sham irradiation. Pain and HRV were measured before and after each irradiation session. All outcome measures used in the first- and second-half treatment courses were analyzed.

Results

Pain and HRV outcome measures of the experimental group significantly improved after SGI when compared with the control group in both courses. Considering time and frequency domains, the changes in HRV in the second-half treatment course exceeded those in the first-half treatment course. Pain was significantly associated with postirradiated HRV indices ( P < 0.001).

Conclusions

Twelve sessions of SGI exerted time-dependent positive effects on pain and sympathovagal imbalance. HRV outcomes, including time and frequency domains, were an independent indicator of the clinical efficiency of SGI for treating pain in patients with neuropathic pain.

Transition from Deep Regional Blocks toward Deep Nerve Hydrodissection in the Upper Body and Torso: Method Description and Results from a Retrospective Chart Review of the Analgesic Effect of 5% Dextrose Water as the Primary Hydrodissection Injectate to Enhance Safety

Deep nerve hydrodissection uses fluid injection under pressure to purposely separate nerves from areas of suspected fascial compression, which are increasingly viewed as potential perpetuating factors in recalcitrant neuropathic pain/complex regional pain. The usage of 5% dextrose water (D5W) as a primary injectate for hydrodissection, with or without low dose anesthetic, could limit anesthetic-related toxicity. An analgesic effect of 5% dextrose water (D5W) upon perineural injection in patients with chronic neuropathic pain has recently been described. Here we describe ultrasound-guided methods for hydrodissection of deep nerve structures in the upper torso, including the stellate ganglion, brachial plexus, cervical nerve roots, and paravertebral spaces. We retrospectively reviewed the outcomes of 100 hydrodissection treatments in 26 consecutive cases with a neuropathic pain duration of 16 ± 12.2 months and the mean Numeric Pain Rating Scale (NPRS) 0-10 pain level of 8.3 ± 1.3. The mean percentage of analgesia during each treatment session involving D5W injection without anesthetic was 88.1%  ±  9.8%. The pretreatment Numeric Pain Rating Scale score of 8.3 ± 1.3 improved to 1.9 ± 0.9 at 2 months after the last treatment. Patients received 3.8 ± 2.6 treatments over 9.7 ± 7.8 months from the first treatment to the 2-month posttreatment follow-up. Pain improvement exceeded 50% in all cases and 75% in half. Our results confirm the analgesic effect of D5W injection and suggest that hydrodissection using D5W provides cumulative pain reduction.

Effects on hemodynamic variables and echocardiographic parameters after a stellate ganglion block in 15 healthy volunteers

BACKGROUND

The sympathetic nervous system has an important role in generating pain. Various pathomechanisms are involved that respond well to the application of local anesthetics (LA), for example to the stellate ganglion block (SGB).

OBJECTIVES

We wanted to know more about the effects of SGB on cardiovascular parameters.

METHODS

We included 15 healthy volunteers; another 15 healthy volunteers as a control group (sham injection of LA). In order to produce a more precise SGB, we employed only a small volume of LA (3mL), a LA with a lower permeability (procaine 1%), and a modified injection technique. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and echocardiographic parameters were recorded before and after SGB. We also investigated whether there are side differences (left and right SBG).

RESULTS

At baseline all parameters were within the normal range. After performing right and left SGB DBP significantly increased (on the right side from 68.73±8.61 to 73.53±11.10, p=0.015; on the left side from 70.66±13.01 to 77.93±10.40, p=0.003). In the control group no increase in DBP was observed. No side-specific differences were found, except a significant reduction in the maximum velocity of myocardial contraction during the systole with left-sided SGB.

CONCLUSIONS

Even with our methods we could not prevent the simultaneous occurrence of a partial parasympatholytic effect. For this reason, the SGB has only minor hemodynamic effects, which is desirable as it enhances the safety of the SGB.

Model of human cardiovascular system with a loop of autonomic regulation of the mean arterial pressure

A model of human cardiovascular system is proposed which describes the main heart rhythm, the regulation of heart function and blood vessels by the autonomic nervous system, baroreflex, and the formation of arterial blood pressure. The model takes into account the impact of respiration on these processes. It is shown that taking into account nonlinearity and introducing the autonomous loop of mean arterial blood pressure in the form of self-oscillating time-delay system allow to obtain the model signals whose statistical and spectral characteristics are qualitatively and quantitatively similar to those for experimental signals. The proposed model demonstrates the phenomenon of synchronization of mean arterial pressure regulatory system by the signal of respiration with the basic period close to 10 seconds, which is observed in the physiological experiments.

Sympathetic activity-associated periodic repolarization dynamics predict mortality following myocardial infarction

BACKGROUND

Enhanced sympathetic activity at the ventricular myocardium can destabilize repolarization, increasing the risk of death. Sympathetic activity is known to cluster in low-frequency bursts; therefore, we hypothesized that sympathetic activity induces periodic low-frequency changes of repolarization. We developed a technique to assess the sympathetic effect on repolarization and identified periodic components in the low-frequency spectral range (≤0.1 Hz), which we termed periodic repolarization dynamics (PRD).

METHODS

We investigated the physiological properties of PRD in multiple experimental studies, including a swine model of steady-state ventilation (n=7) and human studies involving fixed atrial pacing (n=10), passive head-up tilt testing (n=11), low-intensity exercise testing (n=11), and beta blockade (n=10). We tested the prognostic power of PRD in 908 survivors of acute myocardial infarction (MI). Finally, we tested the predictive values of PRD and T-wave alternans (TWA) in 2,965 patients undergoing clinically indicated exercise testing.

RESULTS

PRD was not related to underlying respiratory activity (P<0.001) or heart-rate variability (P=0.002). Furthermore, PRD was enhanced by activation of the sympathetic nervous system, and pharmacological blockade of sympathetic nervous system activity suppressed PRD (P≤0.005 for both). Increased PRD was the strongest single risk predictor of 5-year total mortality (hazard ratio 4.75, 95% CI 2.94-7.66; P<0.001) after acute MI. In patients undergoing exercise testing, the predictive value of PRD was strong and complementary to that of TWA.

CONCLUSION

We have described and identified low-frequency rhythmic modulations of repolarization that are associated with sympathetic activity. Increased PRD can be used as a predictor of mortality in survivors of acute MI and patients undergoing exercise testing.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00196274.

FUNDING

This study was funded by Angewandte Klinische Forschung, University of Tübingen (252-1-0).

The effect of celiac plexus block on heart rate variability

BACKGROUND

Celiac plexus block (CPB) can be used for treating intra-abdominal visceral pain syndromes. The celiac plexus is the largest plexus of the sympathetic nervous system. Several nerve blocks have a marked effect on autonomic nervous activity. Furthermore, stellate ganglion block changes cardiac autonomic nervous activity. Thus, CPB could influence the sympathetic activity of the cardiac plexus. The aim of the present study was to see whether CPB modulated heart rate variability (HRV) in patients with pancreatic cancer.

METHODS

Twelve patients received neurolytic CPB using 14 ml absolute alcohol. Data recorded in a palm-sized electrocardiographic unit were analyzed for HRV.

RESULTS

CPB using a neurolytic solution did not induce any significant changes in the low-frequency (LF)/high-frequency (HF) ratio of HRV (LF/HF, P = 0.4642). Furthermore, the procedure did not induce any significant changes in blood pressure (systolic, P = 0.5051; diastolic, P = 0.5180).

CONCLUSION

CPB did not induce any significant changes in HRV or hemodynamics.

Pilot evaluation of a stellate ganglion block for the treatment of hot flashes

PURPOSE

Hot flashes are a significant problem in breast cancer patients, especially because the most effective therapy, estrogen, is often contraindicated. Based on recent pilot data from a single group supporting the use of a stellate ganglion block for the treatment of hot flashes, the present pilot trial was done to further evaluate the hypothesis that a stellate ganglion block may be a safe and effective therapy for hot flashes.

METHODS

In women with breast cancer who had hot flashes, a stellate ganglion block was performed after 1 week of baseline hot flash data collection. The main efficacy measures were the changes from baseline in hot flash frequency and hot flash score during the 6th week.

RESULTS

Ten patients were enrolled between 4/23/2009 and 7/10/2009; eight patients were evaluable. After the stellate ganglion block, the mean hot flash frequency and score decreased from baseline values by over 60% during some of the post-treatment weeks. The mean hot flash frequency and score at week 6 decreased from baseline values by 44% and 45%, respectively. There were no significant adverse events clearly attributed to the stellate ganglion blocks.

CONCLUSIONS

The results of this pilot trial support that stellate ganglion blocks may be a helpful therapy for hot flashes. A prospective placebo-controlled clinical trial should be done to more definitively determine this contention.

Link between heart rate and blood pressure Mayer wave during general anesthesia

OBJECTIVE

Mayer wave (~10 s) blood pressure (BP) oscillations may represent rhythmic vasomotor activity. However, it remains unclear if volatile anesthetics disturb the coherence between heart rate (HR) and BP rhythms in this region, which may result in improperly affecting BP-HR modulation by the baroreflex, especially when sympathetic stimulation is evoked during general anesthesia using sevoflurane-nitrous oxide (Sev-N2O).

METHODS

Twenty-seven patients were anesthetized with Sev-N2O, followed by surgical incision which induces Mayer wave augmentation. Baseline status before surgical incision was compared with that of 19 awake volunteers, and with status after surgical incision. Baroreflex function was assessed by gain and coherence by transfer function analysis, and the baroreflex effectiveness index (BEI). BP Mayer waves were measured by BP variability at a low frequency (LF) of ~0.1 Hz, and spontaneous baroreflex sensitivity (BRS) was obtained by assessing transfer function gain at LF (BRSLF), and the sequence technique (BRSSEQ).

RESULTS

Sev-N2O anesthesia markedly reduced Mayer waves by 93%, BRSLF by 42%, BRSSEQ by 81%, BEI by 37%, coherence by 42%, and the number of coherent segments by 73%, compared with awake controls. During sympathetic stimulation by surgical incision, however, augmentation of Mayer waves (-1.57±0.72 vs. -0.60±1.00, ln mmHg2 P<0.001) did not improve depressed coherence above 0.5 (0.37±0.09 vs. 0.43±0.11) or BEI (0.17±0.13 vs. 0.13±0.05).

CONCLUSIONS

Sev-N2O anesthesia alters the link between HR and BP Mayer wave oscillation even during sympathetic stimulation, indicating weak spontaneous baroreceptor-HR modulation during general anesthesia.

Autonomic function and cerebral autoregulation in patients undergoing carotid endarterectomy

BACKGROUND

Carotid endarterectomy (CEA) is the first-line treatment in severe carotid stenosis to prevent stroke. Because of methodological limitations, the acute impact of CEA on baroreflex function and cerebral autoregulation is not well defined and was therefore investigated by applying a novel algorithm.

METHODS AND RESULTS

Systemic arterial blood pressure, ECG and respiration during metronomic breathing and Valsalva maneuver were continuously recorded in 18 patients with carotid stenosis before and after CEA, and in 10 healthy controls. Baroreflex sensitivity, frequency spectra of RR intervals and indices for cerebral autoregulation were evaluated by trigonometric regressive spectral analysis. Compared with the controls, patients had impaired baroreflex sensitivity. Baroreflex sensitivity and frequency spectra were not changed by CEA. Cerebral autoregulation of patients with carotid stenosis as calculated by phase shift was reduced compared with controls but it improved significantly after CEA. Improvement of cerebral autoregulation was independent of changes in cerebral blood flow velocity.

CONCLUSIONS

Baroreflex sensitivity and cerebral autoregulation are impaired in patients with carotid stenosis, conferring a high stroke risk. CEA improves cerebral autoregulation, but does not affect baroreflex sensitivity. For further risk reduction, interventional approaches targeting baroreflex function need to be considered.