S Hansen

University of Glasgow, Glasgow, SCT, United Kingdom

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Publications (41)184.9 Total impact

  • M. Staber, S. Hansen, P O. O. Julu
    European Journal of Anaesthesiology 01/2007; 24. DOI:10.1097/00003643-200706001-00271 · 3.01 Impact Factor
  • S Hansen, M Staber
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    ABSTRACT: We have investigated the accuracy of the Colin tonometry module, a non-invasive alternative to intra-arterial blood pressure (BP) measurement. The claims of previous publications range between good agreement to significant discrepancies between the Colin tonometry and intra-arterial methods. The Colin method relies on calibration of the tonometry module using an oscillometric method. Our aim was to look at the effect of this calibration on the accuracy. Ten conscious patients who already had an indwelling arterial catheter were studied. The Colin monitor was set to perform ten calibration cycles first with the oscillometric cuff on the same arm as the tonometry module and secondly on the opposite arm. Simultaneous recording of BP wave forms from the intra-arterial BP transducer and the Colin monitor allowed comparison of beat-by-beat systolic, diastolic and mean BP. There was considerable inter- and intra-patient variation. In the worst case, the error range was 41 mmHg over ten calibrations. Analysis of variance showed that contra- and ipsilateral calibrations gave a significantly different bias while the multiple calibrations accounted for a significant proportion of the variability in systolic BP error. The Colin Tonometry method is not accurate enough to be used with confidence in clinical practice. The main reason for this is its reliance on an oscillometric method for calibration of the tonometry module. Single BP measurements, using either manual or semiautomatic instruments may vary considerably from the 'true' BP due to short-term perturbations of BP.
    European Journal of Anaesthesiology 10/2006; 23(9):781-7. DOI:10.1017/S0265021506000688 · 3.01 Impact Factor
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    ABSTRACT: In dogs with spontaneous heart disease, an electronically generated measurement of cardiac vagal tone, the cardiac index of parasympathetic activity, was a sensitive, simple and inexpensive measure of the severity of heart failure. Dogs with cardiac disease and an index score less than 3 were at 15.8 (95 per cent confidence interval 2.9 to 87.2) times the risk of dying within a year than those with a score of 3 and over. The measurement of the index provided an objective and reliable beat-by-beat measurement of cardiac vagal tone, which was prognostically useful in dogs with heart disease.
    The Veterinary record 02/2005; 156(4):101-5. DOI:10.1136/vr.156.4.101 · 1.63 Impact Factor
  • M. Staber, S. Hansen
    European Journal of Anaesthesiology 01/2005; 22. DOI:10.1097/00003643-200505001-00077 · 3.01 Impact Factor
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    ABSTRACT: To study cardiovascular control in the period leading to vasovagal syncope we monitored beat-to-beat blood pressure, heart rate (HR) and forearm blood flow in 14 patients with posturally related syncope, from supine through to tilt-induced pre-syncope. Signals of arterial blood pressure (BP) from a Finapres photoplethysmograph and an electrocardiograph (ECG) were fed into a NeuroScope system for continuous analysis. Non-invasive indices of cardiac vagal tone (CVT) and cardiac sensitivity to baroreflex (CSB) were derived on a beat-to-beat basis from these data. Brachial vascular resistance (VR) was assessed intermittently from brachial blood flow velocity (Doppler ultrasound) divided by mean arterial pressure (MAP). Patients underwent a progressive orthostatic stress test, which continued to pre-syncope and consisted of 20 min head-up tilt (HUT) at 60 deg, 10 min combined HUT and lower body suction (LBNP) at -20 mmHg followed by LBNP at -40 mmHg. Pre-syncope was defined as a fall in BP to below 80 mmHg systolic accompanied by symptoms. Baseline supine values were: MAP (means +/- S.E.M.) 84.9 +/- 3.2 mmHg; HR, 63.9 +/- 3.2 beats min-1; CVT, 10.8 +/- 2.6 (arbitrary units) and CSB, 8.2 +/- 1.6 ms mmHg-1. HUT alone provoked pre-syncope in 30 % of the patients whilst the remaining 70 % required LBNP. The cardiovascular responses leading to pre-syncope can be described in four phases. Phase 1, full compensation: where VR increased by 70.9 +/- 0.9 %, MAP was 89.2 +/- 3.8 mmHg and HR was 74.8 +/- 3.2 beats min-1 but CVT decreased to 3.5 +/- 0.5 units and CSB to 2.7 +/- 0.4 ms mmHg-1. Phase 2, tachycardia: a progressive increase in heart rate peaking at 104.2 +/- 5.1 beats min-1. Phase 3, instability: characterised by oscillations in BP and also often in HR; CVT and CSB also decreased to their lowest levels. Phase 4, pre-syncope: characterised by sudden decreases in arterial blood pressure and heart rate associated with intensification of the symptoms of pre-syncope. This study has given a clearer picture of the cardiovascular events leading up to pre-syncope. However, the mechanisms behind what causes a fully compensated system suddenly to become unstable remain unknown.
    The Journal of Physiology 06/2003; 549(Pt 1):299-311. DOI:10.1113/jphysiol.2002.036715 · 4.54 Impact Factor
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    ABSTRACT: To classify clinical diseases of the subjects with abnormal indices of peripheral neuropathy identified in field studies of sheep farmers and dippers exposed to organophosphate pesticides. To explore what neuropsychological profiles, if any, may be associated with neurophysiological damage in these subjects. A case-control study (79 subjects) nested within the cross sectional study (685 subjects) of sheep farmers from the field study. Three groups with no, possible, and probable or definite neuropathy according to field studies were recruited. Investigations comprised symptoms of neuropathy, neurologial signs, motor and sensory nerve conduction, electromyography, quantitative sensory testing, and neuropsychological tests. The incidence of clinical neuropathy increased from 7% in the no neuropathy group to 52% in the probable or definite neuropathy group based on nerve conduction measurements or presence of neurological signs. Sensory abnormalities were found more often than motor deficits. Small diameter nerve fibres were also affected more than large fibres. The neuropathy is predominantly sensory and is characteristic of distal, chronic neuropathy with no acute features. Small fibre populations are affected more than large fibre populations. Increasing severity of neuropathy was associated with anxiety and depression as measured in the neuropsychological tests.
    Occupational and Environmental Medicine 08/2002; 59(7):434-41. · 3.23 Impact Factor
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    ABSTRACT: To investigate the reproducibility of measured indices of chronic peripheral neuropathy from a field study of sheep dippers when compared with similar measurements carried out in a clinical setting. A stratified random sample of field study subjects was invited to attend a clinic. Neuropathy was measured both in the field and at the clinic with a modified version of a standard symptoms questionnaire and quantitative sensory thresholds for hot, cold, and vibration. These were combined into a classification of the likelihood of neuropathy with a neuropathy scoring system. Indicators of sensory abnormality were based on comparison of sensory thresholds to age dependent reference values derived from an external reference group. Only 51% of subjects were assigned similar classifications in the field and clinic based on the neuropathy scoring system. Of the component indices, grouped symptom scores, with 65% of subjects showing exact agreement, proved to be more reproducible than quantitative sensory test indicators. There were biases in the comparison of field and clinic measurements of hot and vibration sensations, but no evidence of greater variation between individual people in sensory thresholds in the field relative to at the clinic. The neuropathy scoring system proved to be of limited reproducibility, due in a large part to the lack of reproducibility of the indicators of sensory test abnormality caused by inadequate temperature control. However, the symptoms score and measured sensory thresholds could be used separately as indices of neuropathy in exposure-response analyses.
    Occupational and Environmental Medicine 08/2002; 59(7):442-6. · 3.23 Impact Factor
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    ABSTRACT: To investigate the hypothesis that chronic low level exposure to organophosphates (OPs) in sheep dips is related to clinically detectable measures of polyneuropathy. The design was a cross sectional exposure-response study of sheep dippers and other non-exposed groups. The study group consisted of 612 sheep dipping farmers, 53 farmers with no sheep dipping experience, and 107 ceramics workers. Retrospective exposure information was obtained by questionnaire based on stable and easily identifiable features of sheep dipping found during the first phase of the study; in particular, estimates of handling concentrate and splashing with dilute dip. Neurological assessments were based on a standard neuropathy symptoms questionnaire, and thermal and vibration quantitative sensory tests. Adjusted for confounders there was a weak positive association between cumulative exposure to OPs and neurological symptoms, the significance of which was dependent on the inclusion of a few individual workers with extremely high exposure. There was no evidence of an association between cumulative exposure and the thermal or vibration sensory thresholds. However, separating the effects of exposure intensity and duration showed a higher prevalence of symptoms, primarily of a sensory type, among sheep dippers who handled the OP concentrate. There was also evidence that sensory and vibration thresholds were higher among concentrate handlers, the highest exposed group of dippers. The findings showed a strong association between exposure to OP concentrate and neurological symptoms, but a less consistent association with sensory thresholds. There was only weak evidence of a chronic effect of low dose cumulative exposure to OPs. It is suggested that long term health effects may occur in at least some sheep dippers exposed to OPs over a working life, although the mechanisms are unclear.
    Occupational and Environmental Medicine 12/2001; 58(11):702-10. · 3.23 Impact Factor
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    ABSTRACT: To investigate breathing rhythm and brain stem autonomic control in patients with Rett disorder. Two university teaching hospitals in the United Kingdom and the Rett Centre, Sweden. 56 female patients with Rett disorder, aged 2-35 years; 11 controls aged 5-28 years. One hour recordings of breathing movement, blood pressure, ECG R-R interval, heart rate, transcutaneous blood gases, cardiac vagal tone, and cardiac sensitivity to baroreflex measured on-line with synchronous EEG and video. Breathing rhythms were analysed in 47 cases. Respiratory rhythm was normal during sleep and abnormal in the waking state. Forced and apneustic breathing were prominent among 5-10 year olds, and Valsalva breathing in the over 18 year olds, who were also most likely to breathe normally. Inadequate breathing peaked among 10-18 year olds. Inadequate and exaggerated breathing was associated with vacant spells. Resting cardiac vagal tone and cardiac sensitivity to baroreflex were reduced. Labile respiratory rhythms and poor integrative inhibition in Rett disorder suggest brain immaturity. Linking this to an early monoaminergic defect suggests possible targets for the MECP2 gene in clinical intervention. Exaggerated and inadequate autonomic responses may contribute to sudden death.
    Archives of Disease in Childhood 08/2001; 85(1):29-37. DOI:10.1136/adc.85.1.29 · 2.91 Impact Factor
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    ABSTRACT: We report a patient with sympathetically maintained pain following a mild limb injury. Only emotional sudomotor failure was found in the painful limb. Thermoregulatory vasomotor function was intact. However, the patient had other target-specific sympathetic lesions, including thermoregulatory vasomotor failure in a different limb, not associated with pain. We hypothesize that the sympathetic failure preceded the symptoms and that the mild injury may have provoked collateral sprouting of emotional sudomotor fibres, coupling them with somatic sensory fibres to cause continuous pain.
    European Journal of Neurology 06/2000; 7(3):351-4. DOI:10.1046/j.1468-1331.2000.00069.x · 3.85 Impact Factor
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    ABSTRACT: Rapid changes in heart rate are caused by changes in parasympathetic tone. The NeuroScope is an electronic device designed to offer an objective real-time measure of instantaneous cardiac vagal tone by phase demodulation of a high-resolution time domain of R-R wave intervals. Data are displayed against an arbitrary but linear scale, the cardiac index of parasympathetic activity (CIPA). To validate this method, 10 conscious healthy dogs were each given six incremental doses of atropine (0.01 mg/kg) to a total dose of 0.06 mg/kg or equal volumes of saline. A dose-response curve was constructed. At the maximum dose of atropine, CIPA values fell to 1. 3 +/- 0.7% (SD) of baseline, whereas R-R intervals fell to 51.5 +/- 11.5% of baseline, and standard deviation of the R-R wave interval fell to 10.6 +/- 6.5% of baseline. These findings show that the NeuroScope can provide a specific real-time index of cardiac vagal tone in dogs without need for recourse to atropine.
    The American journal of physiology 03/1999; 276(2 Pt 2):H758-65. · 3.28 Impact Factor
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    ABSTRACT: We report a symptomatic failure of the baroreceptor blood pressure (BP) buffering mechanism in a woman with familial aniridia. Her baseline BP oscillated at 0.1 Hz, the frequency of Mayer waves, with increased amplitude on standing without orthostatic hypotension. Although sudomotor function was normal, cutaneous thermoregulatory function and BP response to Valsalva's maneuver were abnormal. The defective BP buffer mechanism suggests Mayer waves could be a sympathetic mediated cardiovascular resonance. Baroreceptor cardioinhibition was intact. We presume that the lesion is in the rostral aspect of the dorsal medulla oblongata.
    Neurology 01/1998; 49(6):1705-8. DOI:10.1212/WNL.49.6.1705 · 8.30 Impact Factor
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    Archives of Disease in Childhood 12/1997; 77(5):464-5. · 2.91 Impact Factor
  • Archives of Disease in Childhood 11/1997; 77(5):463-463. DOI:10.1136/adc.77.5.463c · 2.91 Impact Factor
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    ABSTRACT: Autonomic activity and respiration were studied in Rett syndrome (RS) and age matched controls. Breathing movements were monitored using a pletysmograph around the chest. Sympathetic activity was monitored by measuring blood pressure (BP) using the Finapres. Cardiac parasympathetic activity was monitored by measuring the cardiac response to baroreflex using the NeuroScope which outputs measure of cardiac vagal tone (CVT) in units of a linear vagal scale (LVS). Resting CVT (means +/- SEM) was 10.5 +/- 0.9 units in the LVS and BP was 94.6 +/- 6.4 mmHg in controls. The BP was 78 +/- 4.33 mmHg and CVT was 3.6 +/- 0.7 units in the LVS in girls with RS, 65% lower than in their age matched controls (p < 0.001), but equal to previously reported level in neonates. Each girl with RS had at least 6 types of breathing dysrhythmias, a sign of instability of the respiratory oscillator. The sympathetic system controlled the HR and BP smoothly during breath holding in control girls, but there were oscillations and rebounds in RS. The HR and BP were under parasympathetic influence during hyperventilation in normal girls but not in RS. The CVT was invariably withdrawn at the height of sympathetic activity during both hyperventilation and breath holding in RS, leading to sympathovagal imbalance with the risk of cardiac arrhythmias and possibly sudden death. Neonatal level of CVT, poor autonomic integration and multiple breathing dysrhythmias shows medullary immaturity in RS. It is the first demonstration of immaturity of the brain which could be used for screening in early childhood and potentially useful for diagnosis and management of RS.
    European Child & Adolescent Psychiatry 01/1997; 6 Suppl 1:47-54. · 3.55 Impact Factor
  • The Veterinary record 12/1996; 139(21):527-8. · 1.63 Impact Factor
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    ABSTRACT: In a pilot study, 14 Gulf War veterans were randomly selected from a large list of those with unexplained illness, to compare the functional integrity of the peripheral and central nervous system with a group of 13 healthy civilian control subjects using predetermined outcome measures. The controls were matched closely for age, sex, handedness, and physical activity. Outcome measures included scoring of symptoms and clinical neurological signs, quantitative sensory testing of heat, cold and vibration sensibilities, motor and sensory nerve conduction studies on upper and lower limbs, needle EMG of distal and proximal muscles and multimodality evoked potential (visual, brainstem, and somatosensory) studies. Three measurements, all related to peripheral nerve function (cold threshold (P = 0.0002), sural nerve latency (P = 0.034), and median nerve sensory action potential (P = 0.030) were abnormal in the veterans compared with the controls. There may be a dysfunction in the veterans but more studies are required to investigate the findings further and to characterise the dysfunction if confirmed.
    Journal of Neurology Neurosurgery & Psychiatry 05/1996; 60(4):449-51. DOI:10.1136/jnnp.60.4.449 · 5.58 Impact Factor
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    Journal of Neurology Neurosurgery & Psychiatry 03/1991; 54(2):187-8. DOI:10.1136/jnnp.54.2.187-a · 5.58 Impact Factor
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    ABSTRACT: In six healthy subjects cortical potentials were evoked by rapidly changing heating or cooling stimuli to the hand. Recordings were made from the contralateral scalp area overlying the sensori-motor cortex, referred to a frontal reference. The potential averaged from 25 stimuli comprised a large positive wave with a mean amplitude of 9.2, SD 1.1 microV for heat and 8.8 SD 1.2 micro V for cold stimulation. The heat evoked potentials had longer peak latencies (range: 280-350 ms) than those elicited by cold stimuli (range: 178-200 ms). A lower amplitude positive wave of a longer latency was also recorded to both modes of stimulation over the corresponding ipsilateral cortex. Cortical thermal evoked potentials were absent in two patients, one with severe selective small fibre neuropathy and the other with syringomyelia, both of whom had high thermal thresholds demonstrated by the technique of Jamal et al. Cerebral potentials evoked by thermal stimuli may represent an alternative approach to the investigation of the central projections of the human small fibre system with both clinical and research potential.
    Journal of Neurology Neurosurgery & Psychiatry 02/1989; 52(1):99-105. DOI:10.1136/jnnp.52.1.99 · 5.58 Impact Factor
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    ABSTRACT: Routine clinical electrophysiological techniques assess function in the large diameter, motor and sensory nerve fibres, but not in the smaller diameter fibres subserving pain, thermal sensation and autonomic function. The instrument we describe measures thermal sensation thresholds to both cooling and warming thus providing an index of function in the small diameter thinly myelinated A delta fibres and unmyelinated C fibers respectively. A commercial version, the Thermal Threshold Tester (TRIPLET) provides a portable instrument for routine clinical use. It has a particularly important role in the sequential and quantitative monitoring of small nerve fibre function as for example in diabetic neuropathy. It can also be applied to the study of small nerve fibre function in persons exposed to potentially neurotoxic substances either as medication or in industry.
    Biosensors 01/1987; 3(6):391-401. DOI:10.1016/0265-928X(87)80020-2