Robert Spaziani

Vagal dysfunction in irritable bowel syndrome assessed by rectal distension and baroreceptor sensitivity

Abstract  Autonomic nervous system dysfunction has been implicated in the pathophysiology of irritable bowel syndrome (IBS). This study characterized the autonomic response to rectal distension in IBS using baroreceptor sensitivity (BRS), a measure of autonomic function. Rectal bag pressure, discomfort, pain, ECG, blood pressure and BRS were continuously measured before, during and after rectal distension in 98 healthy volunteers (34 ± 12 years old, 52 females) and 39 IBS patients (39 ± 11 years old, 35 females). In comparison with the healthy volunteers, IBS patients experienced significantly more discomfort (69 ± 2.2% vs 56 ± 3.6%; P < 0.05), but not pain (9 ± 1.4% vs 6 ± 2.4%; ns) with rectal distension despite similar distension pressures (51 ± 1.4 vs 54 ± 2.4 mmHg; ns) and volumes (394 ± 10.9 vs 398 ± 21.5 mL; ns). With rectal distension, heart rate increased in both healthy volunteers (66 ± 1 to 71 ± 1 bpm; P < 0.05) and IBS patients (66 ± 2 to 74 ± 3 bpm; P < 0.05). Systolic blood pressure also increased in both healthy volunteers (121 ± 2 to 143 ± 2 mmHg; P < 0.05) and patients (126 ± 3 to 153 ± 4 mmHg (P < 0.05) as did diastolic blood pressure, 66 ± 2 to 80 ± 2 mmHg (P < 0.05), compared with 68 ± 3 to 84 ± 3 mmHg (P < 0.05) in IBS patients. The systolic blood pressure increase observed in IBS patients was greater than that seen in healthy volunteers and remained elevated in the post distension period (139 ± 3 mmHg vs 129 ± 2 mmHg; P < 0.05). IBS patients had lower BRS (7.85 ± 0.4 ms mmHg−1) compared with healthy volunteers (9.4 ± 0.3; P < 0.05) at rest and throughout rectal distension. Greater systolic blood pressure response to rectal distension and associated diminished BRS suggests a compromise of the autonomic nervous system in IBS patients.

Heightened central affective response to visceral sensations of pain and discomfort in IBS

Background  Typically, conventional functional imaging methods involve repeated exposures to sensory stimulation. In rectal distension (RD) studies that involve multiple distensions, however, it is difficult to disambiguate the central response to RD from pathological alterations in peripheral neural responses associated with relaxation and accommodation of the rectum.

The effect of sham feeding on neurocardiac regulation in healthy human volunteers

BACKGROUND Distension and electrical stimuli in the esophagus alter heart rate variability (HRV) consistent with activation of vagal afferent and efferent pathways. Sham feeding stimulates gastric acid secretion by means of vagal efferent pathways. It is not known, however, whether activation of vagal efferent pathways is organ- or stimulus-specific. OBJECTIVE To test the hypothesis that sham feeding increases the high frequency (HF) component of HRV, indicating increased neurocardiac vagal activity in association with the known, vagally mediated, increase in gastric acid secretion. METHODS Continuous electrocardiography recordings were obtained in 12 healthy, semirecumbent subjects during consecutive 45 min baseline, 20 min sham feeding (standard hamburger meal) and 45 min recovery periods. The R-R intervals and beat-to-beat heart rate signal were determined from digitized electrocardiography recordings; power spectra were computed from the heart rate signal to determine sympathetic (low frequency [LF]) and vagal (HF) components of HRV. RESULTS Heart rate increased during sham feeding (median 70.8 beats/min, 95% CI 66.0 to 77.6; P<0.001), compared with baseline (63.6, 95% CI 60.8 to 70.0) and returned to baseline levels within 45 min. Sham feeding increased the LF to HF area ratio (median: 1.55, 95% C.I 1.28 to 1.77; P<0.021, compared with baseline (1.29, 95% CI 1.05 to 1.46); this increase in LF to HF area ratio was associated with a decrease in the HF component of HRV. CONCLUSIONS Sham feeding produces a reversible increase in heart rate that is attributable to a decrease in neurocardiac parasympathetic activity despite its known ability to increase vagally mediated gastric acid secretion. These findings suggest that concurrent changes in cardiac and gastric function are modulated independently by vagal efferent fibres and that vagally mediated changes in organ function are stimulus- and organ-specific.

Time-frequency analysis of heart rate variability signals in patients with autonomic dysfunction

An imbalance in the autonomic nervous system has been suspected in patients with coronary artery disease during episodes of silent ischemia. Frequency analysis of the beat-to-beat heart rate variability (HRV) signals reveals a signature of autonomic regulation of the heart. We performed time-frequency analysis of HRV records containing silent ischemic episodes. In 14 out of 17 (82%) HRV data sets there was a loss of power during such intervals, as determined by S-T segment changes. Our studies suggest that if the frequency content of the signal is well preserved, there is less likelihood of ischemic events of any appreciable duration.

A Backward Glance, the Forward Gaze: Evaluation in Problem-Based Courses

That evaluation drives learning is an oft-repeated mantra, though what the purpose of that learning is or what it ought to be is debated. Problem-based learning (PBL) is often touted as providing an opportunity for students to learn more actively, foster self-directed learning and enable a platform for students from which they could launch useful, successful careers. Sixteen years ago, we contrasted the views of students and faculty on specific assessment tools used in an undergraduate science programme which had a significant PBL component (Rawnsley, Spaziani, & Rangachari, Probe 2:9–14, 1994). We now revisit our views about such procedures and see whether any of those that had been developed on largely academic grounds had a measurable impact on our professional lives. The report uses our individual cases to explore the ramifications of the notion of consequential validity.

Optimal electrical stimulation modality for cortical esophageal evoked potentials: transmural or intraesophageal?

Esophageal electrical stimulation using short and a relatively small number of (200 /spl mu/s, 0.2 Hz, n=25) electrical pulses generates a characteristic and well defined cortical evoked potential response (EP). There are two methods of stimulation: either through intraesophageal electrodes or with transmural electrodes. The objective of this paper is to compare EP response, sensations and heart rate variability power spectra elicited by both stimulation modalities in healthy volunteers. Our results suggest that transmural stimulation is more accurately perceived and at lower intensities, produces more reproducible peaks of higher amplitude than during intraesophageal stimulation. During either mode of esophageal stimulation, power within the high-frequency component of the heart rate variability power spectrum is enhanced.

The Benefit of Fentanyl in Effective Sedation and Quality of Upper Endoscopy: A Double-Blinded Randomized Trial of Fentanyl Added to Midazolam Versus Midazolam Alone for Sedation

Abstract Aims Our goals were to compare the effect of adding fentanyl to midazolam in a double-blinded, randomized, placebo-controlled trial and determine if fentanyl enhances sedation, increases adverse events or effects time of the procedure or discharge. Methods Patients 18 to 65 years scheduled for outpatient upper endoscopy were eligible for the study. Patients were randomized to receive either 100 mcg/2 mL of Fentanyl or 2 mL of placebo IV with a double-blinded protocol. All patients received 2 mg of intravenous midazolam initially. Additional midazolam could be given to achieve adequate sedation. Results There were 68 patients randomized to the Fentanyl group and 69 patients to the placebo group. The mean dose of midazolam was 4.0 mg for the Fentanyl group and 5.2 mg for placebo group (P=0.003). Both endoscopist and nurse independently rated sedation to be better in the fentanyl group (P=0001). The patient did not perceive any difference in sedation (P=0.4). Procedure time was significantly shorter in the Fentanyl group (8.5 versus 11.1 minutes, P=0.001), with no difference in the discharge time. There was significantly less retching observed in patients in the fentanyl group (P<0.001). There were no major complications. Conclusions Endoscopists and nurses found adding fentanyl significantly improved sedation, led to a shorter procedure time, and allowed for less midazolam to be used per case. It did not affect the patient experience of sedation and was safe. Fentanyl use for routine outpatient upper endoscopy should be considered as a safe option to improve procedural sedation. NCT:01514695 (www.clinicaltrials.gov) Accepted as an abstract for the Canadian Digestive Diseases Week meeting in February 2014.