Incorrect instruction in the use of the Valsalva manoeuvre for paroxysmal supra-ventricular tachycardia is common

Objective: Success rates for the Valsalva manoeuvre (VM) in treatment of paroxysmal supraventricular tachycardia (SVT) vary with performance technique. This study aimed to assess whether ED doctors instruct their patients to perform the recommended VM technique (supine position for 15 s). Methods: A multicentre, observational study of 35 ED registrars and 17 emergency physicians. Each doctor was asked to describe how he/she would instruct a patient in SVT to perform the VM. Results: Only five (9.6%) doctors would position their patient correctly and 31 (59.6%) would incorrectly instruct their patient to assume a sitting or semirecumbent position. Only five (9.6%) doctors would give specific instructions to blow for at least 15 s and 34 (65.4%) would instruct their patient to blow ‘as long as you can’. Only four (7.4%) doctors would use a sphygmomanometer to measure intrathoracic pressure during the VM. There were no significant differences (P > 0.05) between the registrar and physician group responses for any study endpoint. Conclusion: Few ED doctors correctly instruct their patients in the VM technique recommended for management of SVT. Hence, maximal vagal tone and SVT conversion rates may not be achieved in many cases. The use of the recommended VM technique is encouraged.     

Human auditory cortical dynamics during perception of long acoustic sequences: phase tracking of carrier frequency by the auditory steady-state response

We recorded human auditory cortical activity during the perception of long, changing acoustic signals and analyzed information provided by dynamic neural population measures over a large range of time intervals (approximately 24 ms-5 s). Participants listened to musical scales that were amplitude modulated at a rate of 41.5 Hz, generating an ongoing, stimulus-related oscillatory brain signal, the auditory steady-state response (aSSR). The aSSR generated energy at the amplitude modulation rate that was recorded using magnetoencephalography. As in previous work, the timing (phase) of this response varied with stimulus carrier frequency over the entire course of minute-long tone sequences ('phase tracking' of carrier frequency). The length of the time interval over which phase was calculated was systematically varied; significant phase tracking was regularly observed at analysis intervals of <50 ms in length. The right auditory cortex exhibited better phase tracking performance than the left at analysis intervals of 24-240 ms, and frequency dependent phase delays were consistently larger than those predicted by cochlear mechanics. Based on these empirical data, a model of the neural populations responsible for phase tracking suggests that it is produced by a subpopulation ( approximately 25%) of the cells generating the aSSR.     

Mechanical consequences of short gastric vessel division at the time of laparoscopic total fundoplication

Laparoscopic Nissen fundoplication is currently the most commonly practiced antireflux operation. Some adverse consequences of the operation remain in the form of mechanical side effects, labeled postfundoplication complaints, of which dysphagia and gas bloat seem to predominate. Measures have been suggested to counteract some of these and one frequently advocated has been division of the short gastric vessels to create a short-floppy wrap. The advantages of this are still debated, particularly in the long-term perspective. The aim of the present study was to evaluate the mechanical consequences of dividing all short gastric vessels at the time of a laparoscopic total fundoplication. Ninety-nine patients with chronic gastroesophageal reflux disease (GERD) were originally allocated on a random basis to have either all short gastric vessels divided or left intact at the time of a laparoscopic total fundoplication. A subsample of these patients, again selected at random, were recruited for a comprehensive manometric investigation 1 year after the operation. In this cohort, 12 patients had all short gastrics divided and in 12 patients, the wrap was done with intact vessels by use of the anterior portion of the fundus. Manometry was carried out by the use of a sleeve sensor to straddle the lower esophageal sphincter (LES), and gastric distension (750 ml air) was used to trigger transient LES relaxations (TLESR). The basal LES tone was similar in the two groups (14.2 ± 2.4 and 18.8 ± 4.3, mean ± SE), respectively. Accordingly, all other relevant manometric variables were equal when the two groups were compared, except for the total number of TLESRs (triggered by gastric distension by air) that were significantly higher (p < 0.02) in patients having their short gastric vessels intact. Consequently, numerically more common cavities were recorded in the latter group. Very similar outcomes in terms of motor function of the LES and esophageal body were observed after a total fundoplication irrespective of whether a complete division of all gastric vessels had been carried out or not. However, after gastric distension with air, more TLESRs were recorded in the latter group suggesting a better maintained ability to vent air from the stomach.     

Vestibular evoked myogenic potentials in acute low-tone sensorineural hearing loss

OBJECTIVE/HYPOTHESIS: It was the authors' premise that the vestibular evoked myogenic potential (VEMP) test may be used to differentiate acute low-tone hearing loss (ALHL) from Meniere's disease with low-tone HL. STUDY DESIGN: Prospective study. METHODS: From January 2000 to December 2002, consecutive 12 patients with ALHL and another 12 patients with definite Meniere's disease with low-tone HL were enrolled in this study. All patients underwent audiometry and VEMP test, before and after treatment with isosorbide for 3 consecutive months. RESULTS: Before treatment, 12 patients with ALHL revealed normal VEMPs (11, 92%) and augmented VEMPs (1). After treatment, 11 (92%) patients had resolved to normal hearing within 3 days. One year later, two (17%) patients progressed to Meniere's disease. In comparison with Meniere's disease, 6 (50%) of 12 patients showed normal VEMPs before treatment, and 7 (58%) patients had their hearing improved 3 months after treatment. Comparison of VEMP responses or hearing outcome between both groups exhibited significant differences. CONCLUSION: Most patients with ALHL reveal normal VEMPs throughout the episode, indicating that the saccule is spared. In contrast, 50% of Meniere's disease patients with low-tone HL demonstrate abnormal VEMPs, showing a significant difference. Therefore, the VEMP test can be used to differentiate ALHL from Meniere's disease with low-tone HL.     

Discordant mental and physical efforts in an autistic patient

We investigated whether there was mental effort in response to verbal commands in a 16-year old girl with autism, a high degree of non-compliance with commands and symptoms of autonomic dysfunction by monitoring the brainstem autonomic tone during an attempt to perform isometric exercise. An index of cardiac vagal tone (CVT), cardiac sensitivity to baroreflex (CSB), heart rate (HR) and mean arterial blood pressure (MAP) were measured simultaneously. Physical non-compliance with our commands meant there was no force applied by the patient during the attempted exercise, but CVT and CSB were both reduced and sustained at very low levels throughout the attempt, while MAP and HR were increased concurrently to higher levels in the same period. This vagal withdrawal to allow concurrent increases in HR and MAP is an arousal response appropriate for isometric exercise, which is a sign of a positive mental effort to comply with our commands. These results demonstrate discordant mental and physical efforts in our patient. In this particular case, the physical inabilities in some instances could have been mislabelled as mental non-compliance due to autism. It would be worthwhile to investigate the prevalence of discordant mental and physical efforts in autism.     

AT1 antagonism by eprosartan lowers heart rate variability and baroreflex gain

INTRODUCTION: Blockade of the renin-angiotensin system (RAS) by ACE inhibitors has been demonstrated to reduce total mortality in cardiovascular diseases. This advantage was attributed in part to changes of autonomic cardiovascular control, exemplified by an increase of heart rate variability (HRV) and baroreflex gain (BRG). We sought to assess the effects of the angiotensin type 1 (AT1) receptor blocker eprosartan on HRV and BRG. MATERIALS AND METHODS: In a double-blind randomized cross-over design 25 young males took eprosartan (600 mg/day) and placebo each for a period of 7 days with a wash-out period of at least 4 weeks in between. At the end of the intake phases simultaneous recordings of arterial blood pressure (AP; Finapres) and electrocardiogram (ECG) were taken. Power spectra of HRV and arterial blood pressure variability (APV) were calculated by fast Fourier transform (FFT) and served to calculate BRG. Ang-II levels were measured by radioimmunoassay. RESULTS: Eprosartan tended to lower mean AP, it slightly increased heart rate (HR) (p<0.05), and markedly increased circulating Ang-II levels (p<0.01). Eprosartan diminished the total power of HRV (p<0.05) and the BRG (p<0.01). The low/high frequency (LF/HF) ratio of HRV and the APV were not altered. CONCLUSIONS: AT1 antagonism by eprosartan lowers heart rate variability and baroreflex gain. We speculate that these findings are due to the marked increase in circulating angiotensin II (Ang II). Further studies are needed to clarify whether angiotensin type 1 (AT1) blockers with potential actions inside the blood-brain barrier (BBB) may have different effects on HRV and BRG.     

Topical phenylephrine increases anal canal resting pressure in patients with faecal incontinence

INTRODUCTION: The internal anal sphincter receives a stimulatory alpha(1) adrenergic innervation. Use of an adrenergic agonist may therefore have a role in treating patients with faecal incontinence. METHODS: Ten patients (seven females, median age 66 years) with passive faecal incontinence related to weak internal anal sphincter were studied. All patients had intact anal sphincters as assessed by endoanal ultrasound. Phenylephrine gel was applied in a double blind manner in concentrations of 0%, 10%, 20%, 30%, and 40% (Slaco Pharma (UK) Ltd, Watford, UK) on separate days. Maximum resting anal pressure (MRP), anodermal blood flow, blood pressure, and pulse rate were measured before, and one and two hours after application. RESULTS: All concentrations of phenylephrine gel increased median MRP (43, 48, 54, 65, and 70 cm H(2)O, for placebo, 10% (p=0.122), 20% (p=0.170), 30% (p=0.002), and 40% (p=0.004), respectively at one hour; comparisons with placebo). This was sustained at two hours. There was a clear dose-response relationship at one hour. Higher concentrations raised median MRP to within the normal range (> 60 cm H(2)O). At two hours, all concentrations greater than 20% increased the pressure to a similar degree, suggesting that the exact concentration may be important for the initial effect but given a certain threshold is less important after a period of time. Toxicity was rare. Two patients experienced transient perianal burning which settled within a few minutes. There was no significant effect on anodermal blood flow, blood pressure, or pulse rate. CONCLUSION: This study has demonstrated the feasibility of using topical phenylephrine to raise resting anal tone in patients with faecal incontinence. Randomised controlled trials are required to assess the efficacy of this agent.     

Mapping responses to frequency sweeps and tones in the inferior colliculus of house mice

In auditory maps of the primary auditory cortex, neural response properties are arranged in a systematic way over the cortical surface. As in the visual system, such maps may play a critical role in the representation of sounds for perception and cognition. By recording from single neurons in the central nucleus of the inferior colliculus (ICC) of the mouse, we present the first evidence for spatial organizations of parameters of frequency sweeps (sweep speed, upward/downward sweep direction) and of whole-field tone response patterns together with a map of frequency tuning curve shape. The maps of sweep speed, tone response patterns and tuning curve shape are concentrically arranged on frequency band laminae of the ICC with the representation of slow speeds, build up response types and sharp tuning mainly in the centre of a lamina, and all (including high) speeds, phasic response types and broad tuning mainly in the periphery. Representation of sweep direction shows preferences for upward sweeps medially and laterally and downward sweeps mainly centrally in the ICC (either striped or concentric map). These maps are compatible with the idea of a gradient of decreasing inhibition from the centre to the periphery of the ICC and by gradients of intrinsic neuronal properties (onset or sustained responding). The maps in the inferior colliculus compare favourably with corresponding maps in the primary auditory cortex, and we show how the maps of sweep speed and direction selectivity of the primary auditory cortex could be derived from the here-found maps of the inferior colliculus.     

Vasomotor effects of L- and D-arginine in stenotic atheromatous coronary plaque

OBJECTIVE—To examine the effects of exogenous L- and D-arginine on coronary stenosis vasomotion in relation to stenosis morphology.
DESIGN—Intracoronary infusions of normal saline, L- and D-arginine (50 and 150 µmol/min), and glyceryl trinitrate (250 µg bolus) were given in 24 patients with coronary artery disease and stable angina. Coronary stenoses were classified as smooth or complex (irregular borders). The diameter of the coronary stenoses and their adjacent reference segments was measured by computed quantitative angiography.
RESULTS—During L-arginine infusion a larger proportion of complex stenoses than smooth stenoses dilated by ⩾ 10% (p < 0.01), and the magnitude of dilatation was greater at the site of complex stenoses (p < 0.05). Irrespective of the type of morphology there was a positive correlation (p < 0.01) between the severity of stenoses and the magnitude of vasodilatation to L-arginine. The response to glyceryl trinitrate was similar in the two groups. No significant change was found in either group in response to D-arginine.
CONCLUSIONS—In patients with coronary artery disease, coronary stenoses—particularly those of complex morphology—dilate in response to the administration of L-arginine but not D-arginine. This finding is consistent with partial deficiency of the substrate for nitric oxide synthesis, L-arginine, at the site of complex stenoses.


     

A Novel Formulation of VIP in Sterically Stabilized Micelles Amplifies Vasodilation In Vivo

Purpose. To determine whether human vasoactive intestinal peptide (VlP)-poly(ethylene glycol) (PEG)-grafted distearoyl-phosphatidyleth-anolamine (DSPE) micelles elicit potent and stable vasodilation in vivo. Methods. PEG-DSPE micelles were prepared by co-precipitation. VIP was loaded into micelles by incubation at room temperature. Vasoactivity of VIP in SSM was determined by monitoring changes in diameter of resistance arterioles in the in situ hamster cheek pouch using intravital microscopy. Results. VIP easily undergoes self-assembly into small PEG-DSPE micelles (mean [±SEM] size, 18 ± 1 nm) in a time-dependent fashion. This generates a potent vasoactive matrix at nanomole concentrations of VIP as manifested by ~3-fold potentiation and prolongation of vasodilation relative to that evoked by aqueous VIP alone (p < 0.05). This response is specific and mediated by the L-arginine/nitric oxide (NO) biosynthetic pathway. Micellar VIP dispersion remains vasoactive for at least 14 days after preparation and storage at 4°C. Conclusions. A novel, self-associated, small and stable PEG-DSPE micellar formulation of VIP amplifies vasodilation in the in situ peripheral microcirculation in a specific fashion by elaborating NO. An optimized formulation could be considered for certain cardiovascular disorders associated with L-arginine/NO biosynthetic pathway dysfunction.