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Biomedical subjects

I M Williams

Publications and source records attributed to I M Williams.

At least 19 recordsLinked to original sources
PubMed1996

Neutrophil activation in jugular venous blood during carotid endarterectomy.

OBJECTIVES: Neutrophils may play an important role in cerebral ischaemia. We investigated whether neutrophil activation can be detected in cerebral venous blood during the mild cerebral hypoxia and reperfusion that occurs during carotid cross clamping and declamping for endarterectomy. DESIGN, SETTING AND MATERIALS: The ipsilateral jugular bulb was cannulated at operation in 16 patients undergoing carotid endarterectomy. Blood was taken immediately prior to and 30 seconds following internal carotid cross clamping; then immediately prior to, 30 s and 2 m following declamping. Blood was also taken from a peripheral vein in the foot. Intracerebral oxygen saturation (CsO2) was measured continuously by near infrared cerebral spectroscopy. Neutrophil activation was measured by flow cytometric detection of fluorescence to hydrogen peroxide in unstimulated cells and phorbol myristate acetate stimulated cells, and expressed as mean fluorescent intensity (MFI). OUTCOME MEASURES: Neutrophil activation and cerebral oxygenation. MAIN RESULTS: CsO2 fell from 68% (95% Confidence interval 64%-72%) to 63% (59%-68%) following carotid cross clamping (p < 0.05, repeated measures analysis of variance). This recovered slightly during the cross clamp period to 64% but only returned to preclamp levels following declamping (p > 0.05). Neutrophil hydrogen peroxide generation by stimulated neutrophils rose significantly from 0.79 mean fluorescent intensity (0.53-1.19) to 1.46 (0.98-2.20) but no there was no further rise following cross clamp release. There was no significant neutrophil activation in the peripheral samples. CONCLUSIONS: These results indicate that even mild cerebral hypoxia is associated with priming of neutrophils in cerebral venous blood.

Aged↗
PubMed1996

Recent developments in cerebral monitoring--near-infrared light spectroscopy. An overview.

A recent development has been the resurgence of interest in the concept of near-infrared light spectroscopy as a method of monitoring cerebral perfusion. Although this technique has been in use for 40 years, the principle has been primarily employed in peripheral pulse oximetry. Infrared light of wavelengths 600-1300 nanometres (nm) penetrate human tissue to a depth of several centimetres. Within the human brain this light is attenuated by the chromophores oxyhaemoglobin, deoxyhaemoglobin and also oxidised cytochrome a3. Positioning a near-infrared light source and a photodetector in a side by side configuration detects light attenuated and reflected in a parabolic path through the scalp, skull and brain tissue.

Brain↗
PubMed1996

The senior SHO rotation in Wales--a basis for BST training.

Between 1969-1992 there was a successful surgical registrar rotation in South Wales (1). This was a three-year rotation comprising two years general surgery, six months trauma and orthopaedics and six months surgical specialty. The rotation was aimed at those doctors who had completed senior house officer (SHO) posts in accident and emergency, 6-12 months general surgery and had already obtained the primary FRCS. However, with the recent recommendations of the Calman Report concerning general surgical training (2) changes to this rotation have become necessary, namely to reduce the number of surgical registrars in order to achieve a balance in numbers entering higher surgical training and to shorten the period of training to seven years with two years Basic Surgical Training (BST) and five years Higher Surgical Training (HST). A modified rotation was therefore designed and implemented in South Wales since July 1992. The previous registrar rotation was shortened to two years instead of three ensuring the pre-requirements for entry into HST and eligibility to sit the second part FRCS. The aim of this study was to assess whether the new senior SHO/BST rotation in South Wales is providing adequate training for our surgical trainees to enter into HST. We present our data as a potential basis for setting up a formal BST rotation.

Attitude of Health Personnel↗
PubMed1996

Prevalence of abdominal aortic aneurysm in a hypertensive population.

Two studies were undertaken to estimate the prevalence of abdominal aortic aneurysm in a hypertensive population. The initial study screened hypertensive people from three local general practices. In this study 918 patients underwent ultrasound scanning of the abdominal aorta (498 men and 420 women). A total of 24 abdominal aortic aneurysms were identified; 20 in men (4%) and four in women (0.9%). Of these, 11 were > 4 cm in transverse diameter. Following this study, only hypertensive men over the age of 60 years and women over the age of 65 years were screened from a total of 29 general practices. Regular scanning sessions were held at each practice and 1328 patients attended (744 men and 584 women). A total of 43 abdominal aortic aneurysms were detected; 39 in men (5.2%) and four in women (0.7%). Hypertensive men are at increased risk of developing abdominal aortic aneurysms and should be offered an initial ultrasound scan at 60 years of age. Female hypertensives yield a much lower detection rate and screening hypertensive females would probably be an inappropriate use of available resources.

Age Distribution↗
PubMed1995

Effects of stimulus velocity and acceleration on smooth pursuit in motor neuron disease.

Sinusoidal smooth pursuit eye movements were evaluated in 11 normals, five moderately and four severely affected motor neuron disease (MND) patients, using two target amplitudes and a range of frequencies. This enabled us to examine separately the effects of peak target velocity and acceleration on pursuit gain. Moderately affected patients showed an acceleration, but not a velocity saturation; severely impaired patients' performance declined with increased velocity. Smooth pursuit eye movements are thus impaired in MND, but the nature of this pursuit deficit is complex and changes with the progression of the disease.

Aged↗
PubMed1995

The influence of contralateral carotid stenosis and occlusion on cerebral oxygen saturation during carotid artery surgery.

OBJECTIVES: To study the effect of contralateral carotid stenosis on oxygen saturation (CsO2) of both cerebral hemispheres monitored by reflective near-infrared spectroscopy (NIRS) during carotid surgery. METHODS: NIRS was compared to ipsilateral transcranial Doppler ultrasonography (TCD) of the middle cerebral artery and jugular bulb venous oxygen saturation (JvSO2) in 54 patients undergoing carotid endarterectomy. RESULTS: Median operated side and contralateral CsO2 were 68(54-88)% and 69(55-85)% before carotid clamping falling to 63(44-80)% and 69(55-84)% respectively on clamping the carotid (p < 0.0001 and p = NS). JvSO2 fell from 78(38-98)% to 72(30-97)% on carotid clamping with a percentage fall in peak TCD of -28(0 to -100)% (p < 0.0001). Patients with a contralateral carotid artery occlusion experienced falls in ipsi and contralateral CsO2 of -8(-4 to -10)% and -3(2 to -7)% compared to -4(0 to -14)% and 0(-5 to 4)% in those with a lesser stenosis (p < 0.05). On declamping, median ipsilateral and contralateral CsO2 rose from 65(46-82)% and 67(52-87)% to 68(53-84)% respectively (p < 0.0001 and p = NS). JvSO2 increased from 75(33-95)% to 79(42-95)% (p < 0.0001) with an increase in median peak TCD of 35(-34 to 506)%. CONCLUSIONS: The greatest changes in CsO2 occurred in the operated side cerebral hemispheres in those with a contralateral carotid artery occlusion. However, a contralateral carotid artery occlusion does not reliably predict the need for a shunt and cerebral monitoring remains essential; although is only required on the operated side.

Brain↗
PubMed1994

Cerebral oxygen saturation, transcranial Doppler ultrasonography and stump pressure in carotid surgery.

Transcranial Doppler ultrasonography (TCD) of the middle cerebral artery (MCA), light-reflective cerebral oximetry and measurement of internal carotid artery stump pressure were compared as methods of monitoring cerebral perfusion during carotid surgery in 33 patients. Median cerebral oxygen saturation was 70 (range 62-85) per cent and TCD-measured mean blood velocity 42 (range 19-91) cm/s before carotid cross-clamping, falling to 68 (53-83) per cent and 16 (0-50) cm/s respectively on application of the clamps (P < 0.001). Stump pressure correlated closely with MCA blood velocity 30 s after the start of cross-clamping (rs = 0.58, P < 0.001), but not with cerebral oxygen saturation. A fall of 5 per cent or more in cerebral oxygen saturation following cross-clamp application was predicted by a decrease in mean MCA blood velocity of at least 60 per cent. Changes in cerebral oxygen saturation correlated significantly with systolic blood pressure throughout the perioperative period (rs = 0.41, P < 0.001). Significant falls in cerebral oxygenation were not predicted by low stump pressure but were associated with large reductions in the mean MCA blood velocity measured by TCD.

Blood Flow Velocity↗
PubMed1994

Light-reflective cerebral oximetry and jugular bulb venous oxygen saturation during carotid endarterectomy.

A novel instrument using reflected near-infra-red light spectroscopy to measure cerebral oxygen saturation non-invasively was evaluated during carotid endarterectomy; cerebral perfusion was compared with jugular bulb venous oxygen saturation and transcranial Doppler ultrasonographic measurements. Initially, oximetry sensors with light source-detector separation distances of 10 and 27 mm were positioned over the frontal area, while a cannula positioned in the jugular bulb permitted sampling for jugular bulb venous oxygen saturation. To increase cerebral oxygen saturation sensitivity, modified sensors with light source-detector separation distances of 30 and 40 mm were relocated over the middle cerebral artery territory. The changes in cerebral and jugular bulb venous oxygen saturation, and in peak blood flow velocity before and 30 s after carotid clamping and declamping were recorded. The modified cerebral perfusion system achieved improved correlations between cerebral and jugular bulb venous oxygen saturation changes during carotid clamping and declamping (r = 0.92, P < 0.001). The correlation between change in cerebral oxygen saturation and the percentage change in peak flow velocity on both cross-clamping and declamping was equally strong (r = 0.90, P < 0.001). Near-infra-red cerebral spectroscopy reliably detects changes in cerebral oxygen saturation during carotid endarterectomy and may have wide applications in monitoring brain perfusion during neurosurgery and cardiopulmonary bypass surgery, and in closed head injury.

Blood Flow Velocity↗