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Injury of the afferent limb of the baroreflex from neck radiation causes radiation-induced afferent baroreflex failure (R-ABF). Identification and management of R-ABF is challenging. We aimed to investigate the pattern of autonomic dysfunction on standardized autonomic testing in patients with probable R-ABF. We retrospectively analyzed all autonomic reflex screens performed at Mayo Clinic in Rochester, MN, between 2000 and 2020 in patients with probable R-ABF. Additional tests reviewed included ambulatory blood pressure monitoring, plasma norepinephrine, and thermoregulatory sweat test. We identified 90 patients with probable R-ABF. Median total composite autonomic severity score (range, 0-10) was 7 (interquartile range, 6-7). Cardiovascular adrenergic impairment was seen in 85 patients (94.4%), increased blood pressure recovery time after Valsalva maneuver in 71 patients (78.9%; median 17.4 seconds), and orthostatic hypotension in 68 patients (75.6%). Cardiovagal impairment was demonstrated by abnormal heart rate responses to deep breathing (79.5%), Valsalva ratio (87.2%), and vagal baroreflex sensitivity (57.9%). Plasma norepinephrine was elevated and rose appropriately upon standing (722-1207 pg/mL). Ambulatory blood pressure monitoring revealed hypertension, postural hypotension, hypertensive surges, tachycardia, and absence of nocturnal dipping. Blood pressure lability correlated with impaired vagal baroreflex function. Postganglionic sympathetic sudomotor function was normal in most cases; the most frequent thermoregulatory sweat test finding was focal neck anhidrosis (78.9%). Standardized autonomic testing in R-ABF demonstrates cardiovascular adrenergic impairment with orthostatic hypotension, blood pressure lability, and elevated plasma norepinephrine. Cardiovagal impairment is common, while sudomotor deficits are limited to direct radiation effects.

Objective: To describe the natural history of afferent baroreflex failure (ABF) based on systematic review of clinical and laboratory data in patients with a diagnosis of ABF at Mayo Clinic Rochester., Methods: We performed a retrospective chart review of all patients who underwent standardized autonomic reflex testing between 2000 and 2020 and had confirmation of the diagnosis of ABF by an autonomic disorders specialist. Patients were identified using a data repository of medical records. Variables included demographic, all-cause mortality, medications, ABF manifestations, comorbidities, and laboratory (autonomic testing, blood pressure monitoring, echocardiogram, brain imaging, plasma catecholamines, serum sodium level, and kidney function tests)., Results: A total of 104 patients with ABF were identified. Head and neck radiation was the most common etiology (86.5%), followed by neck surgery (5.8%) and other causes (7.7%). The most common findings were hypertension (87.5%), fluctuating blood pressure (78.8%), orthostatic hypotension (91.3%), syncope (58.6%), headache (22.1%), and tachycardia (20.2%). Patients commonly received antihypertensives (66.3%), pressor agents (41.3%), or a combination of both (19.2%). The median latency from completion of radiation to ABF was longer compared to the latency in the surgery group ( p < 0.0001). Comorbidities, including complications from neck radiation, were frequently seen and all-cause mortality was 39.4% over a 20-year period., Conclusions: ABF should be suspected in patients with prior head and neck cancer treated by radiation or surgery who present with labile hypertension and orthostatic hypotension. Management may require both antihypertensive and pressor medications. The morbidity and mortality in ABF are high., (© 2021 American Academy of Neurology.)

A laboratory-scale enricher reactor (ER) - permeable reactive biobarrier (PRBB) system was studied to address performance loss of a PRBB due to substrate interactions among a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) in groundwater, when the mixture reappeared after a 10-day absence period. Toluene and BTEX as an inducer in ER were compared to investigate toluene as a potential single inducer in ER. PRBBs without ER augmentation experienced performance losses ranging from 11% to 35% for PRBBs initially inoculated with toluene degraders and 22% to 33% for PRBBs initially inoculated with BTEX degraders. Bacterial communities changed substantially in these PRBBs after the absence period, which could contribute to the performance losses. PRBBs augmented with toluene degraders overcame the inhibition interaction between benzene and toluene, and showed a superior removal performance for toluene degradation suggesting that toluene can be used as a single inducer in an ER., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Glucagon-like peptide-1 (GLP-1), an incretin, which is used to treat diabetes mellitus in humans, inhibited vagal activity and activated nitrergic pathways. In rats, GLP-1 also increased sympathetic activity, heart rate, and blood pressure (BP). However, the effects of GLP-1 on sympathetic activity in humans are unknown. Our aims were to assess the effects of a GLP-1 agonist with or without alpha(2)-adrenergic or -nitrergic blockade on autonomic nervous functions in humans. In this double-blind study, 48 healthy volunteers were randomized to GLP-1-(7-36) amide, the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-l-arginine acetate (l-NMMA), the alpha(2)-adrenergic antagonist yohimbine, or placebo (i.e., saline), alone or in combination. Hemodynamic parameters, plasma catecholamines, and cardiac sympathetic and parasympathetic modulation were measured by spectral analysis of heart rate. Thereafter, the effects of GLP-1-(7-36) amide on muscle sympathetic nerve activity (MSNA) were assessed by microneurography in seven subjects. GLP-1 increased (P = 0.02) MSNA but did not affect cardiac sympathetic or parasympathetic indices, as assessed by spectral analysis. Yohimbine increased plasma catecholamines and the low-frequency (LF) component of heart rate power spectrum, suggesting increased cardiac sympathetic activity. l-NMMA increased the BP and reduced the heart rate but did not affect the balance between sympathetic and parasympathetic activity. GLP-1 increases skeletal muscle sympathetic nerve activity but does not appear to affect cardiac sympathetic or parasympathetic activity in humans.

Background: The baroreflex is responsible for maintaining a stable blood pressure (BP) despite changes in body positions and fails in many autonomic disorders. The baroreflex regulates BP by changing the heart rate (vagal component) and total peripheral resistance (adrenergic component). Baroreflex sensitivity is widely used to quantify the vagal component of the reflex, but the adrenergic component is not quantifiable in the autonomic laboratory., Objectives: To develop and validate an index of adrenergic baroreflex sensitivity., Design: We validated this index with microneurographically recorded muscle sympathetic nerve discharges generated by the Valsalva maneuver and verified it against groups of patients with graded severities of adrenergic failure., Results: Adrenergic baroreflex sensitivity relates BP recovery time to the preceding decrease in BP evoked by the Valsalva maneuver. This index showed a graded and highly significant impairment in 3 groups of patients, (1) those with orthostatic hypotension (n = 26), (2) those with borderline orthostatic hypotension (n = 34), and (3) those with impaired reflex vasoconstriction without orthostatic BP change (n = 24), when compared with an age- and sex-matched control group (n = 29). Adrenergic baroreflex sensitivity better tracked the severity of adrenergic failure than the vagal component of baroreflex sensitivity and provides a much needed index to quantify total peripheral resistance changes in patients with adrenergic failure., Conclusions: The 2 indices of baroreflex sensitivity separately evaluate the vagal and adrenergic components of the baroreflex. Combined, they provide an index of composite or global baroreflex function.

Epidemiological evidence suggests decreased heat tolerance in patients with Type 2 diabetes mellitus (T2DM), but it is not known whether the mechanisms involved in thermoregulatory control of skin blood flow are altered in these patients. We tested the hypothesis that individuals with T2DM have a delayed internal temperature threshold for active cutaneous vasodilation during whole body heating compared with healthy control subjects. We measured skin blood flow using laser-Doppler flowmetry (LDF), internal temperature (T or) via sublingual thermocouple, and mean arterial pressure via Finometer at baseline and during whole body heating in 9 T2DM patients and 10 control subjects of similar age, height, and weight. At one LDF site, sympathetic noradrenergic neurotransmission was blocked by local pretreatment with bretylium tosylate (BT) to isolate the cutaneous active vasodilator system. Whole body heating was conducted using a water-perfused suit. There were no differences in preheating T(or) between groups (P > 0.10). Patients with T2DM exhibited an increased internal temperature threshold for the onset of vasodilation at both untreated and BT-treated sites. At BT-treated sites, T or thresholds were 36.28 +/- 0.07 degrees C in controls and 36.55 +/- 0.05 degrees C in T2DM patients (P < 0.05), indicating delayed onset of active vasodilation in patients. Sensitivity of vasodilation was variable in both groups, with no consistent difference between groups (P > 0.05). We conclude that altered control of active cutaneous vasodilation may contribute to impaired thermoregulation in patients with T2DM.

Background: The clinical characteristics of autoimmune autonomic neuropathy are only partially defined. More than 50% of patients with high levels of ganglionic acetylcholine receptor (AChR) autoantibodies have a combination of sicca complex (marked dry eyes and dry mouth), abnormal pupillary light response, upper gastrointestinal tract symptoms, and neurogenic bladder., Objective: To compare patients with idiopathic autonomic neuropathy who were seropositive (n = 19) and seronegative (n = 87) for ganglionic AChR antibodies., Design: Retrospective review of autonomic programmatic database., Setting: Autonomic Disorders Program Project at Mayo Clinic College of Medicine, Rochester, Minn., Patients: We evaluated a cohort of 87 patients with idiopathic autonomic neuropathy who had undergone full autonomic testing and neurological evaluation and who had a complete panel of paraneoplastic and ganglionic AChR antibodies. We compared patients seropositive (n = 19) and seronegative (n = 87) for ganglionic AChR antibodies., Results: The seropositive group had a significant overrepresentation of abnormal pupillary responses (12/18 [67%] vs 12/87 [14%]; P<.001), sicca complex (9/15 [60%] vs 11/47 [23%]; P =.01), and lower gastrointestinal tract dysautonomia (16/19 [84%] vs 48/85 [56%]; P =.02). A subacute mode of onset was more common in the seropositive group (12/19 [63%] vs 23/84 [27%]; P =.004). Results of quantitative autonomic function tests differed significantly in the 2 groups only in the cardiovagal domain. Because subacute onset was overrepresented in the seropositive group, we analyzed the data separately, controlling for temporal profile (ie, the relationship between antibody status and symptoms while controlling for rate of onset). The relationships between antibody status and clinical profile (eg, presence of sicca complex, pupillary abnormalities, and lower gastrointestinal tract symptoms) generally remained significant regardless of onset rate, indicating that the associations are not due to temporal profile., Conclusions: These observations support the concept that ganglionic AChR antibodies are diagnostically and pathophysiologically important. Patients with orthostatic hypotension and prominent cholinergic dysautonomia are most likely to be seropositive for ganglionic AChR antibody.

We analyzed the clinical characteristics of 18 patients (13 female, 5 male) who had autoimmune autonomic neuropathy (AAN) and ganglionic acetylcholine receptor (AChR) autoantibodies. Mean age was 61.4 years (standard deviation, 12.0 years). Ten patients had subacute symptom onset, six with an antecedent event. Eight patients had chronic AAN, characterized by insidious symptom onset, without antecedent event, and gradual progression. A majority of patients with high antibody values (>1.00 nmol/L) had a combination of sicca complex (marked dry eyes and dry mouth), abnormal pupillary light response, upper gastrointestinal symptoms, and neurogenic bladder. Chronic AAN segregated into two subgroups. One subgroup (N = 4) had low antibody titer (0.09 +/- 0.01 nmol/L) and a paucity of cholinergic symptoms. It was indistinguishable from pure autonomic failure. The other subgroup (N = 4) had high antibody titer (11.6 +/- 2.08 nmol/L), sicca complex, abnormal pupils, and neurogenic bladder; three had severe upper gastrointestinal dysfunction. Higher antibody titers correlated with greater autonomic dysfunction and more frequent cholinergic dysautonomia. These observations expand the clinical spectrum of AAN to include chronic cases, some being indistinguishable from pure autonomic failure, and support the concept that ganglionic AChR antibodies are important diagnostically and pathophysiologically in acquired dysautonomia.