Standard Heart Rate Variability Parameters-Their Within-Session Stability, Reliability, and Sample Size Required to Detect the Minimal Clinically Important Effect.

Many intervention studies assume the stability of heart rate variability (HRV) parameters, and their sample sizes are often small, which can significantly affect their conclusions. The aim of this study is to assess the stability and reliability of standard HRV parameters within a single resting session, and to estimate the sample size required to detect the minimal clinically important effect of an intervention. Heart rate was recorded in 50 adult healthy subjects for 50 min in a seated position. Eight standard HRV parameters were calculated from five evenly spaced 5 min intervals. Stability was assessed by comparing the mean values of HRV parameters between the consecutive five test-retest measurements. Absolute reliability was determined by standard error of measurement, and relative reliability by intraclass correlation coefficient. The sample size required to detect a mean difference of ≥30% of between-subject standard deviation was estimated. As expected, almost all HRV parameters had poor absolute reliability but most HRV parameters had substantial to excellent relative reliability. We found statistically significant differences in almost all HRV parameters between the first 20 min and the last 30 min of the session. The estimated sample size ranged from 19 to 300 subjects for the first 20 min and from 36 to 194 subjects for the last 30 min of the session, depending on the selected HRV parameter. We concluded that optimal HRV measurement protocols in a resting seated position should be performed within the first 20 min or between 20 and 50 min after assuming a resting seated position. Future interventional HRV studies should include a sufficient number of subjects and consider the Bonferroni correction according to the number of selected HRV parameters to achieve an appropriate level of study power and precision.

Association between statin use and clinical course, microbiologic characteristics, and long-term outcome of early Lyme borreliosis. A post hoc analysis of prospective clinical trials of adult patients with erythema migrans.

BACKGROUND: Statins were shown to inhibit borrelial growth in vitro and promote clearance of spirochetes in a murine model of Lyme borreliosis (LB). We investigated the impact of statin use in patients with early LB. METHODS: In this post-hoc analysis, the association between statin use and clinical and microbiologic characteristics was investigated in 1520 adult patients with early LB manifesting as erythema migrans (EM), enrolled prospectively in several clinical trials between June 2006 and October 2019 at a single-center university hospital. Patients were assessed at enrollment and followed for 12 months. RESULTS: Statin users were older than patients not using statins, but statin use was not associated with Borrelia seropositivity rate, Borrelia skin culture positivity rate, or disease severity as assessed by erythema size or the presence of LB-associated symptoms. The time to resolution of EM was comparable in both groups. The odds for incomplete recovery decreased with time from enrollment, were higher in women, in patients with multiple EM, and in those reporting LB-associated symptoms at enrollment, but were unaffected by statin use. CONCLUSION: Statin use was not associated with clinical and microbiologic characteristics or long-term outcome in early LB.

Clinical and Radiological Characteristics Associated with Respiratory Failure in Unilateral Lateral Medullary Infarction.

BACKGROUND: The prognosis for unilateral lateral medullary infarction (ULMI) is generally good but may be aggravated by respiratory failure with fatal outcome. Respiratory failure has been reported in patients with severe bulbar dysfunction and large rostral medullary lesions, but its associated factors have not been systematically studied. We aimed to assess clinical and radiological characteristics associated with respiratory failure in patients with pure acute ULMI. MATERIALS AND METHODS: Seventy-one patients (median age 55 years, 59 males) with MRI-confirmed acute pure ULMI were studied retrospectively. Clinical characteristics were assessed and bulbar symptoms were scored using a scale developed for this study. MRI lesions were classified into 4 groups based on their vertical extent (localized/extensive) and the involvement of the open and/or closed medulla. Clinical characteristics, bulbar scores and MRI lesion characteristics were compared between patients with and without respiratory failure. RESULTS: Respiratory failure occurred in 8(11%) patients. All patients with respiratory failure were male (p = 0.336), had extensive lesions involving the open medulla (p = 0.061), progression of bulbar symptoms (p=0.002) and aspiration pneumonia (p < 0.001). Peak bulbar score (OR, 7.9 [95% CI, 2.3-160.0]; p < 0.001) and older age (OR, 1.2 [95%CI, 1.0-1.6]; p=0.006) were independently associated with respiratory failure. CONCLUSIONS: Extensive damage involving the open/rostral medulla, clinically presenting with severe bulbar dysfunction, in conjunction with factors such as aspiration pneumonia and older age appears to be crucial for the development of respiratory failure in pure ULMI. Further prospective studies are needed to identify other potential risk factors, pathophysiology, and effective preventive measures for respiratory failure in these patients.

Clinical manifestations and long-term outcome of early Lyme neuroborreliosis according to the European Federation of Neurological Societies diagnostic criteria (definite versus possible) in central Europe. A retrospective cohort study.

BACKGROUND AND PURPOSE: The characteristics and long-term outcome of Lyme neuroborreliosis (LNB) according to diagnostic certainty (definite vs. possible) are incompletely understood. METHODS: In this retrospective cohort study of adults with definite or possible LNB, clinical and microbiological characteristics and long-term outcome over 12 months were evaluated at a single medical center. Severity of acute disease and long-term outcome were assessed using a composite clinical score encompassing clinical findings and symptoms and by the probability of incomplete recovery. RESULTS: Amongst 311 adult patients enrolled from 2008 to 2017, 139 (44.7%) had definite LNB and 172 (55.3%) had possible LNB. The most frequent LNB manifestation was cranial neuropathy with or without meningitis (53.4%). Patients with definite LNB more often had Bannwarth syndrome (53.2% vs. 18.6%), more severe disease (6 points vs. 4 points), longer pre-treatment duration (median 21 days vs. 13.5 days), higher cerebrospinal fluid pleocytosis (median 139 × 106 /L vs. 11 × 106 /L) and higher rate of Borrelia seropositivity (84.2% vs. 68.6%) than those with possible LNB. Ceftriaxone was prescribed more often than oral doxycycline in definite LNB than in possible LNB (96.4% vs. 65.7%). Unfavorable outcomes decreased during follow-up, being higher in patients with more severe disease at enrollment and in those with possible LNB, but were not associated with antibiotic therapy. CONCLUSIONS: Early LNB, most often presenting as cranial neuropathy, was definitively diagnosed in less than half of cases. A better diagnostic approach is needed to confirm borrelial etiology. Ceftriaxone was not superior to doxycycline in the treatment of early LNB, regardless of diagnostic certainty. In this retrospective cohort study of 311 adults with Lyme neuroborreliosis (LNB), allocated according to diagnostic certainty, early LNB was definitively diagnosed in less than half of cases and the most frequent LNB manifestation was cranial neuropathy with or without meningitis. Patients with definite LNB more often had Bannwarth syndrome, more severe disease, longer pre-treatment duration, higher cerebrospinal fluid pleocytosis and higher rate of Borrelia seropositivity than those with possible LNB. A better diagnostic approach is needed to confirm borrelial etiology. Ceftriaxone was not superior to doxycycline in the treatment of early LNB, regardless of diagnostic certainty.

Prognostic value of CT perfusion and permeability imaging in traumatic brain injury.

BACKGROUND: Currently established prognostic models in traumatic brain injury (TBI) include noncontrast computed tomography (CT) which is insensitive to early perfusion alterations associated with secondary brain injury. Perfusion CT (PCT) on the other hand offers insight into early perfusion abnormalities. We hypothesized that adding CT perfusion and permeability data to the established outcome predictors improves the performance of the prognostic model. METHODS: A prospective cohort study of consecutive 50 adult patients with head injury and Glasgow Coma Scale score of 12 or less was performed at a single Level 1 Trauma Centre. Perfusion CT was added to routine control CT 12 hours to 24 hours after admission. Region of interest analysis was performed in six major vascular territories on perfusion and permeability parametric maps. Glasgow Outcome Scale (GOS) was used 6 months later to categorize patients' functional outcomes to favorable (GOS score > 3) or unfavorable (GOS score ≤ 3). We defined core prognostic model, consisting of age, motor Glasgow Coma Scale score, pupillary reactivity, and CT Rotterdam Score. Next, we added perfusion and permeability data as predictors and compared updated models to the core model using cross-validated areas under the receiver operator curves (cv-AUC). RESULTS: Significant advantage over core model was shown by the model, containing both mean cerebral extravascular-extracellular volume per unit of tissue volume and cerebral blood volume of the least perfused arterial territory in addition to core predictors (cv-AUC, 0.75; 95% confidence interval, 0.51-0.84 vs. 0.6; 95% confidence interval, 0.37-0.74). CONCLUSION: The development of cerebral ischemia and traumatic cerebral edema constitutes the secondary brain injury and represents the target for therapeutic interventions. Our results suggest that adding CT perfusion and permeability data to the established outcome predictors improves the performance of the prognostic model in the setting of moderate and severe TBI. LEVEL OF EVIDENCE: Prognostic study, level III.

Breathing patterns in relation to sleep stages in acute unilateral lateral medullary infarction: An exploratory study.

Our aim was to perform an exploratory study of various irregular breathing patterns (IBPs) across different sleep stages in patients with acute unilateral lateral medullary infarction (ULMI) and compare them to apparently healthy individuals. Polysomnography (PSG) was analyzed for IBPs, such as periodic breathing, ataxic breathing and tachypnea. IBPs were found in 52 % of healthy and 90 % of ULMI subjects (p = 0.001) and occurred in long (≥ 10 min) episodes in 8% of healthy and 68 % of ULMI (p < 0.001). In healthy subjects, short (< 10 min) episodes of mild to moderate ataxic breathing were observed in wakefulness and light sleep and short episodes of periodic breathing upon sleep onset. In ULMI, the most common IBPs were ataxic and periodic breathing (80 % of patients), followed by shallow tachypnea (28 %). Ataxic breathing predominated in wakefulness, ataxic or periodic breathing in light sleep, while breathing tended to normalize in deep and REM sleep. Considering the IBPs occurring in the healthy group as physiological, probably pathological breathing patterns (tachypnea, long episodes of moderate/severe ataxic or long episodes of periodic breathing) occurred in 67 % of ULMI patients. Our findings suggest that ULMI might exacerbate physiological sleep-stage-dependent breathing pattern irregularities, such as ataxic and periodic breathing, in terms of intensity and duration or might even induce non-physiological IBP, such as shallow tachypnea with sustained hypoxia.

Systemic immune responses in patients with early localized or early disseminated Borrelia afzelii lyme borreliosis.

INTRODUCTION: The role of host immune responses in the pathogenesis of borrelial dissemination in early Lyme borreliosis (LB) in the form of multiple erythema migrans (MEM) or LB-associated symptoms is incompletely understood. METHODS: In this study, fifteen cytokine or chemokine levels, representative of innate, Th1, and Th17 immune responses, were assessed using a bead-based Luminex multiplex assay in acute sera from 76 adult patients with skin culture-positive Borrelia afzelii solitary erythema migrans (SEM) and 58 patients with MEM at a single-center university hospital. Differences between the groups were tested by modeling each cytokine or chemokine concentration by means of left-censored regression using the classic Tobit model. RESULTS: Mean serum cytokine or chemokine levels were low. When taking into account the proportion of patients with cytokine or chemokine concentrations below the lowest detectable limit, only levels of CXCL10 (p = .03) and CCL19 (p = .02), representatives of the Th1 immune response, differed between patients with SEM and those with MEM; however, the differences did not reach statistical significance when adjusted for multiple comparisons. In addition, we did not find differences in systemic inflammatory responses when comparing patients with and those without LB-associated constitutional symptoms. CONCLUSION: No significant differences in systemic immune responses represented by selected cytokines or chemokines in serum samples of patients with EM infected with B. afzelii suggest that systemic mediators are not pivotal in the pathogenesis of dissemination of early infection in the form of MEM or LB-associated symptoms. Localized immune responses in the skin or other pathogenetic mechanisms may be more important in this regard.

Five-Day vs 10-Day Postexposure Chemoprophylaxis With Oseltamivir to Prevent Hospital Transmission of Influenza: A Noninferiority Randomized Open-Label Study.

BACKGROUND: The efficacy and optimal duration of postexposure influenza prophylaxis with oseltamivir are undetermined in hospital settings, where immediate separation from index cases is not feasible. METHODS: In an open-label noninferiority randomized clinical trial in a single-center university hospital, the efficacy of 5-day vs 10-day postexposure prophylaxis with oseltamivir was compared in adult patients exposed to influenza who could not be immediately separated from index influenza cases. Influenza incidence was assessed for 10 days after discontinuing prophylaxis. RESULTS: Among 222 exposed patients (median age, 75 years; male 119; median Charlson Comorbidity Index, 5), 110 patients were assigned to 5 days of postexposure prophylaxis with oseltamivir, and 112 patients were assigned to the 10-day group. The median duration of exposure to influenza (interquartile range) was 2 (1-3) days. In the intention-to-treat analysis, the incidence of influenza was 2/110 (1.8%) in the 5-day group and 0/112 (0%) in the 10-day group (difference, 1.8 percentage points; 1-sided 95% CI, -1 to 4.9 percentage points; P = .77). CONCLUSIONS: For patients exposed to influenza in a hospital setting and who were not immediately separated from index cases, postexposure prophylaxis with oseltamivir resulted in low incidence of nosocomial influenza transmission. Five-day postexposure prophylaxis was noninferior to 10-day regimen. CLINICALTRIALSGOV REGISTRATION: NCT03899571.

Prospective study of sleep-disordered breathing in 28 patients with acute unilateral lateral medullary infarction.

OBJECTIVE: Acute unilateral lateral medullary infarction (ULMI) is complicated by respiratory failure in 2-6% of patients. However, studies investigating milder respiratory disorders not leading to overt respiratory failure, i.e., sleep-disordered breathing (SDB) and its outcome, are lacking. The aim of our study was to identify and prospectively follow SDB in acute ULMI. METHODS: We prospectively followed 28 patients with MRI-confirmed acute ULMI. Polysomnography (PSG) was performed 1-3 times in the acute phase (at 1-4, 5-10, and 14-21 days after onset of symptoms) and after 3-6 months. PSG recordings in the acute phase were analyzed and compared to the follow-up. RESULTS: Apnea-hypopnea index (AHI) ≥ 5/h, AHI ≥ 15/h, and AHI ≥ 30/h in the acute phase were observed in 22 (79%), 19 (68%), and 10 (36%) patients, respectively. CSA, OSA, mixed CSA/OSA, or multiple interchanging SDB types were observed in the acute phase in 12 (43%), 2 (7%), 2 (7%), and 6 (21%) patients, respectively. Peak AHI varied in individual patients (median at 7 (3-14) days after onset). At follow-up, AHI and central AHI tended to decrease (p = 0.007, p = 0.003, respectively), obstructive AHI did not change (p = 0.396). Sleep architecture partially improved with significantly higher percentage of N2 and lower percentage of wakefulness after sleep onset (p = 0.007, p = 0.012, respectively). CONCLUSIONS: Our data show that SDB, particularly CSA, is common in the acute phase of ULMI and that the frequency of central events decreases in the subacute phase. Further studies are needed to clarify the clinical significance and possible treatment options of SDB in these patients.

Window of opportunity for surgical decompression in patients with acute traumatic cervical spinal cord injury.

OBJECTIVE: The objective of this prospective study was to determine the optimal timing for surgical decompression (SD) in patients with acute traumatic cervical spinal cord injury (tSCI) within the first 24 hours of injury. METHODS: In successive patients with fracture and/or dislocation of the subaxial cervical spine and American Spinal Injury Association Impairment Scale (AIS) grades A-C, receiver operating characteristic curve analysis was used to determine the optimal timing for SD within the first 24 hours of cervical tSCI to obtain a neurological recovery of at least two AIS grades. Multivariate logistic regression was used to model significant neurological recovery with time to SD, degree of spinal canal compromise (SCC), and severity of injury. RESULTS: In this cohort of 64 patients, the optimal timing for SD to obtain a significant neurological improvement was within 4 hours of injury (95% confidence interval 4-9 hours). Increasing the delay from injury to SD or the degree of SCC significantly reduced the likelihood of significant neurological improvement. Due to the strong correlation with SCC, the severity of injury was a marginally significant predictor of neurological recovery. CONCLUSIONS: These findings indicate that in patients with acute cervical tSCI and AIS grades A-C, the optimal timing for SD is within the first 4-9 hours of injury, depending on the degree of SCC and the severity of injury. Further studies are required to better understand the interrelationships among the timing of SD, injury severity, and degree of SCC in these patients.

Novel Direct Anticoagulants and Atherosclerosis.

Coagulation factors can affect cellular processes that include inflammatory signaling by acting on endothelial protease activated receptors, vascular smooth muscle and inflammatory cells beyond the coagulation cascade. This is important in the pathogenesis of atherosclerosis. Accordingly, experimental data points to beneficial effects of coagulation protease inhibitors on the attenuation of atherosclerosis progression in animal models. However, available clinical data do not support the use of anticoagulants as an add-on treatment of atherosclerosis. New clinical studies are needed with a better selection of patients to clarify the role of novel direct anticoagulants in the management of atherosclerosis.

Doxycycline-induced photosensitivity in patients treated for erythema migrans.

BACKGROUND: Doxycycline is one of the recommended antibiotics for treating erythema migrans (EM). Since EM predominantly occurs during summer, the potential of doxycycline to induce photosensitivity is of concern. In studies on the efficacy of doxycycline for treating relatively small numbers of patients with EM, the reported frequency of photosensitivity has varied from none to 15%. The aim of this study was to elucidate the frequency and clinical symptoms of doxycycline-induced photosensitivity in a large cohort of patients with EM treated in a single medical centre. METHODS: Prospectively collected data on adverse events were analysed in adult patients with EM treated with doxycycline 100 mg twice daily for 10-15 days. RESULTS: Photosensitivity reactions ranging from itching and burning sensations to transient mild erythema of sun-exposed skin were documented in 16/858 (1.9, 95% CI 1.1-3.0%) patients and appeared from June to October with highest frequency in July. These adverse events were more frequent in patients treated for 14 or 15 days (16/750 [2.1%]; 95% CI 1.2-3.4%) than in those treated for 10 days (0/108 [0%]; 95% CI 0.0-3.4%); however, the difference was not significant (P = 0.24). Women were more often affected than men (13/475 [2.7%], 95% CI 1.5-4.6% versus 3/383 [0.8%], 95% CI 0.2-2.3%; P = 0.04). Of the 16 patients who developed photosensitivity, 13 did not adhere to the recommendation to avoid sun exposure. None of the patients had any long-term sequelae of photosensitivity. CONCLUSIONS: Photosensitivity reactions in adult patients with EM treated with doxycycline 100 mg twice daily for 10-15 days occurred rarely, were not severe, and had no long-term sequelae. TRIAL REGISTRATION: Registered at http://clinicaltrials.gov , Identifiers NCT00910715, May 28th 2009, NCT01163994, July 13th 2010 and NCT03584919, June 19th 2018 retrospectively registered.

Neurological Recovery after Traumatic Cervical Spinal Cord Injury Is Superior if Surgical Decompression and Instrumented Fusion Are Performed within 8 Hours versus 8 to 24 Hours after Injury: A Single Center Experience.

A prospective study was performed to evaluate the impact of surgical decompression (SD) and instrumented fusion within 8 h versus 8-24 h after injury on neurological recovery after cervical traumatic spinal cord injury (tSCI) in patients operated on in the UMC Ljubljana, Slovenia. Only patients with the American Spinal Injury Association (ASIA) Impairment Scale (AIS) grades of A through C and with MRI-confirmed spinal cord compression were enrolled. The primary outcome was the change in AIS grade at the 6-month follow-up. Of the 48 enrolled patients, 22 patients who underwent surgery within 8 h (group 8 h) and 20 patients who underwent surgery between 8 and 24 h (Group 8-24 h) after injury concluded the study. At admission, there was no statistically significant difference in AIS grade between the study groups. At the 6-month follow-up, an improvement of at least two AIS grades was found in 45.5% of patients in group 8 h and in 10% of patients in group 8-24 h (p=0.017). The median improvement in the ASIA motor score was 38.5 (10.0-61.0) motor points in group 8 h and 15.0 (8.8-34.0) motor points in group 8-24 h (p=0.0468). In a multivariate analysis, adjusted for the preoperative AIS grade and the degree of spinal canal compromise, the odds of an at least two-grade AIS improvement were at least 106% higher for patients in group 8 h than for patients in group 8-24 h (odds ratio=11.08, p=0.004). No statistically significant difference was found in the rate of perioperative complications, pneumonia, and the number of ventilator-dependent days or the mortality between the groups. Our results suggest that the patients with tSCI who undergo SD within 8 h after injury have superior neurological outcomes than patients who undergo SD 8-24 h after injury, without any increase in the rate of adverse effects.

Study of neurovascular coupling during cold pressor test in patients with migraine.

BACKGROUND: Altered neurovascular coupling in migraineurs could be a consequence of impaired function of modulatory brainstem nuclei. The cold pressor test (CPT) should activate brainstem structures. We measured visually evoked cerebral blood flow velocity response (VEFR) to CPT in migraine. METHODS: Twenty-three healthy volunteers and 29 migraineurs participated in the study. We measured arterial blood pressure, end-tidal CO2, heart rate and cerebral blood flow velocity in posterior and middle cerebral artery using transcranial Doppler. VEFR was calculated as cerebrovascular reactivity to photic stimulation before, during and after CPT. RESULTS: In healthy individuals, there was a significant decrease in peak systolic VEFR from CPT phase to recovery phase (p < 0.05). There was an increase in mean VEFR from basal to CPT phase and a decrease from CPT to recovery phase, both significant (p < 0.05). End-diastolic VEFR increased from basal to CPT phase and decreased in recovery phase below the basal phase values, all changes significant (p < 0.05). In migraine, no statistically significant changes in peak systolic, mean or end-diastolic VEFRs were observed between phases (p > 0.05). The differences in phases in mean and end-diastolic VEFRs between the basal phase and the CPT phase and between the CPT phase and the recovery phase were significantly higher in healthy individuals (p < 0.05). CONCLUSIONS: The absence of the effect of CPT on VEFR in migraine is likely to be a consequence of impaired subcortical modulation of neurovascular coupling.

Tick borne encephalitis without cerebrospinal fluid pleocytosis.

BACKGROUND: Tick borne encephalitis is the most frequent vector-transmitted infectious disease of the central nervous system in Europe and Asia. The disease caused by European subtype of tick borne encephalitis virus has typically a biphasic clinical course with the second phase presenting as meningitis, meningoencephalitis, or meningoencephalomyelitis. Cerebrospinal fluid pleocytosis is considered a condition sine qua non for the diagnosis of neurologic involvement in tick borne encephalitis, which in routine clinical practice is confirmed by demonstration of serum IgM and IgG antibodies to tick borne encephalitis virus. CASE PRESENTATION: Here we present a patient from Slovenia, an area highly endemic for tick borne encephalitis, with encephalitis but without cerebrospinal fluid pleocytosis in whom tick borne encephalitis virus infection of the central nervous system was demonstrated. CONCLUSION: Cerebrospinal fluid pleocytosis is not mandatory in encephalitis caused by tick borne encephalitis virus. In daily clinical practice, in patients with neurologic symptoms/signs compatible with tick borne encephalitis and the risk of exposure to ticks in a tick borne encephalitis endemic region, the search for central nervous system infection with tick borne encephalitis virus is warranted despite the lack of cerebrospinal fluid pleocytosis.

Resting heart rate variability and heart rate recovery after submaximal exercise.

PURPOSE: Aerobic training accelerates Heart Rate Recovery after exercise in healthy subjects and in patients with coronary disease. As shown by pharmacological autonomic blockade, HRR early after exercise is dependent primarily on parasympathetic reactivation. Thus, accelerated HRR early after exercise in endurance-trained athletes may be attributed to augmented parasympathetic reactivation. In the present study, we tested the hypothesis that the HRR early after submaximal exercise is related to the pre-exercise parasympathetic modulation. METHODS: Thirty endurance-trained athletes (20 males, 50 ± 7 years) and thirty control subjects (20 males, 52 ± 6 years) performed a submaximal exercise on a cyclo-ergometer. Pre-exercise resting short-term heart rate variability (HRV) parameters in time and frequency-domains were correlated with HRR during the first 30 s, 1 and 2 min after cessation of exercise. RESULTS: We found that HRR was statistically significantly faster in athletes than in controls at all examination time points (p < 0.05). HF, SDNN and RMSSD were statistically significantly higher in athletes than in controls (p < 0.05), but other resting HRV parameters were not statistically different between groups. After 30 s, 1 and 2 min of recovery, HRR correlation with total power, HF, HFnu and RMSSD was positive, while the correlation with LF/HF was negative for small and positive for larger values. The opposite was true for SDNN. CONCLUSIONS: These findings support the hypothesis that HRR early after submaximal exercise is related to resting parasympathetic modulation in the middle-aged subjects. In addition, they suggested an optimal range of HRV for maximal HRR after exercise.

Comparison of active standing test, head-up tilt test and 24-h ambulatory heart rate and blood pressure monitoring in diagnosing postural tachycardia.

Protocols for the assessment of postural tachycardia differ in both type of orthostatic challenge and test duration. We therefore compared heart rate (HR) and blood pressure responses during an active standing test (AST) and a head-up tilt test (HUT) in 34 patients with orthostatic intolerance and 31 asymptomatic subjects. A subset also performed 24-h ambulatory blood pressure monitoring (ABPM). HR responses were similar between AST and HUT both in asymptomatic and in orthostatic intolerant subjects. Specificity of HR increase ≥30 bpm for orthostatic intolerance was high (above 0.85) with both AST and HUT and was similar at 3 minutes and at 9 minutes. HR changes recorded during self-performed AST (in the context of 24-h ABPM) and circadian HR difference corresponded well to changes recorded during AST in the autonomic laboratory. We conclude that AST and HUT are comparable methods for the assessment of postural tachycardia, that 3-min and 9-min tests are appropriate, and that ABPM is a useful ancillary test in the assessment of orthostatic responses.

Influence of breaching the connective sheaths of the donor nerve on its myelinated sensory axons and on their sprouting into the end-to-side coapted nerve in the rat.

The influence of breaching the connective sheaths of the donor sural nerve on axonal sprouting into the end-to-side coapted peroneal nerve was examined in the rat. In parallel, the effect of these procedures on the donor nerve was assessed. The sheaths of the donor nerve at the coaptation site were either left completely intact (group A) or they were breached by epineurial sutures (group B), an epineurial window (group C), or a perineurial window (group D). In group A, the compound action potential (CAP) of sensory axons was detected in ~10% and 40% of the recipient nerves at 4 and 8 weeks, respectively, which was significantly less frequently than in group D at both recovery periods. In addition, the number of myelinated axons in the recipient nerve was significantly larger in group D than in other groups at 4 weeks. At 8 weeks, the number of axons in group A was only ~15% of the axon numbers in other groups (p<0.05). Focal subepineurial degenerative changes in the donor nerves were only seen after 4 weeks, but not later. The average CAP area and the total number of myelinated axons in the donor nerves were not different among the experimental groups. In conclusion, myelinated sensory axons are able to penetrate the epiperineurium of donor nerves after end-to-side nerve coaption; however, their ingrowth into recipient nerves is significantly enhanced by breaching the epiperineurial sheets at the coaptation site. Breaching does not cause permanent injury to the donor nerve.

The effect of the cold pressor test on a visually evoked cerebral blood flow velocity response.

We investigated the hypothesis that during tonic pain stimulus, neurovascular coupling (NVC) decreases, measuring visually evoked cerebral blood flow velocity response (VEFR) during cold pressor test (CPT) in healthy human subjects as a test. VEFR was calculated as a relative increase in blood flow velocity in the posterior cerebral artery from average values during the last 5 s of the stimulus-OFF period to average values during the last 10 s of the stimulus-ON period. Three consecutive experimental phases were compared: basal, CPT and recovery. During CPT, end-diastolic and mean VEFR increased from 20.2 to 23.6% (p < 0.05) and from 17.5 to 20.0% (p < 0.05), respectively. In recovery phase, end-diastolic and mean VEFR decreased to 17.7% and 15.5%, respectively. Both values were statistically significantly different from CPT phase (p < 0.05). Compared with the basal phase, only end-diastolic VEFR was statistically significantly different in the recovery phase (p < 0.05). Our results are consistent with the assumption that there is a change in the activity of NVC during CPT because of the modulatory influence of subcortical structures activated during tonic pain. Contrary to our expectations, the combined effect of such influences increases rather than decreases NVC.