Does access to a portable ophthalmoscope improve skill acquisition in direct ophthalmoscopy? A method comparison study in undergraduate medical education.

BACKGROUND: Direct ophthalmoscopy (DO) is an essential skill for medical graduates but there are multiple barriers to learning this. Medical students and junior doctors typically lack confidence in DO. Most students do not own an ophthalmoscope and learn via ward devices that vary in design and usability. The Arclight ophthalmoscope (AO) is an easy to use, low-cost and portable device that could help address device access. This study aimed to assess the impact of personal ownership of an AO on DO skill acquisition and competency amongst medical students in the clinical environment. METHODS: Method comparison study with 42 medical students randomised to either traditional device ophthalmoscope (TDO) control or AO intervention group during an 18-week medical placement. Three objective assessments of DO competency were performed at the beginning and end of the placement: vertical cup to disc ratio (VCDR) measurement, fundus photo multiple-choice questions (F-MCQ) and model slide examination (MSE). DO examinations performed during the placement were recorded via an electronic logbook. RESULTS: Students in both groups recorded a median number of six examinations each during an eighteen-week placement. There was no statistically significant difference between the groups in any of the objective assessment measures (VCDR p = 0.561, MCQ p = 0.872, Model p = 0.772). Both groups demonstrated a minor improvement in VCDR measurement but a negative performance change in F-MCQ and MSE assessments. CONCLUSIONS: Students do not practice ophthalmoscopy often, even with constant access to their own portable device. The lack of significant difference between the groups suggests that device access alone is not the major factor affecting frequency of DO performance and consequent skill acquisition. Improving student engagement with ophthalmoscopy will require a more wide-ranging approach.

Effect of superficial venous surgery on venous function in chronic venous insufficiency.

Patients with chronic venous insufficiency often have combined superficial and deep venous incompetence. The aims of this study were to determine the effects of superficial venous surgery (SVS) on deep venous haemodynamics and on ambulatory venous pressure (AVP) and to determine if the AVP tourniquet test can predict the effect of SVS. Of 119 legs, 42 legs (32 subjects) with chronic venous insufficiency, healed ulceration, or active ulceration and with combined superficial and deep incompetence underwent preoperative duplex imaging and AVP measurement followed by appropriate SVS. Four months later, all underwent postoperative duplex imaging and AVP measurement. The pressure relief index (PRI) was calculated from the AVP measurement as an overall assessment of venous function. Seventeen of 119 (14%) showed no tourniquet improvement in PRI and were therefore excluded from SVS. Of those suitable for SVS, median (range) age was 56 (32-78) years. Twenty-two limbs underwent long saphenous surgery, four limbs short saphenous surgery, and 16 limbs both, based on duplex findings. Segmental deep incompetence resolved in 11/21 (52%) limbs after surgery compared to 6/21 (29%) with multisegment incompetence. Median (range) PRI improved from 319 (4-1,600) preoperatively to 1,300 (360-2,670) postoperatively (p < 0.001, Wilcoxon). PRI with thigh tourniquet correlated with postoperative PRI (r = +0.828, p = 0.01, Spearman), as did calf tourniquet (r = +0.996, p = 0.004) and both tourniquets (r = 0.535, p = 0.046). The majority of patients with combined superficial and deep incompetence can be selected for SVS on the basis of AVP measurement with tourniquets. SVS can improve segmental deep incompetence and PRI in those properly selected.

Early carotid surgery in acute stroke: a multicentre randomised pilot study.

BACKGROUND: Standard practice has been to delay carotid endarterectomy (CEA) for 2 months following acute stroke to avoid a perceived risk of cerebral haemorrhage. We investigated whether early CEA reduces early recurrent stroke and improves outcome in partial anterior circulation infarction (PACI). METHODS: Patients with PACI and a Barthel score of >18 before stroke underwent carotid duplex and CT imaging within 7 days of stroke. Forty consenting patients fit for surgery with greater than 70% ipsilateral carotid stenosis were randomised, 19 to 'early' (within 24 h) and 21 to 'delayed' surgery (at 8 weeks). Modified Rankin and Barthel scores were recorded at 1 week, 2 months, 6 and 12 months. RESULTS: Rankin scores improved more rapidly following 'early' surgery to a score of 1 (0-4) at 2 and 6 months compared with 2.5 and 2 (1-4), respectively, for delayed surgery (p < 0.05). Barthel scores were also significantly improved following 'early' CEA at 7 days but both groups reached a median score of 20 by 2 months. Four 'delayed' and 3 'early' patients suffered extension or recurrence of neurological deficits with 1 death in each group. CONCLUSIONS: Early CEA within 7 days of ischaemic stroke improved functional outcome with earlier hospital discharge. A large multicentre study is needed to exclude the possibility that 'early' CEA increases the risk of cerebral haemorrhage or death.

The contribution of the external carotid artery to cerebral perfusion in carotid disease.

PURPOSE: In the presence of carotid occlusion, the external carotid artery (ECA) becomes an important source of cerebral blood flow, especially if the circle of Willis is incomplete. The contribution of the ECA to hemispheric blood flow in patients with severe ipsilateral carotid stenosis has never been previously investigated. METHODS: One hundred eight patients were monitored during sequential cross-clamping of the external (ECA) and then ipsilateral internal carotid artery (ICA) during carotid endarterectomy using transcranial Doppler sonography (TCD) (Neuroguard CDS, Los Angeles, Calif), to measure middle cerebral artery blood flow velocity, and near-infrared spectroscopy, to measure regional cerebral oxygen saturation (CsO(2)) (Invos 3100A; Somanetics, Troy, Mich). RESULTS: On the ipsilateral ECA cross-clamp, the median fall in CsO(2) was 3% (interquartile range, 1%-4%; P <.0001). On addition of the ICA cross-clamp there was a further fall of 3% and a total fall of 6% (3%-9%; P <.0001). The median percentage fall in middle cerebral artery blood flow velocity on ECA clamping was 12% (4%-24%; P <.0001); on ICA clamping it was 48% (25%-74%; P <.0001). Falls in TCD on ECA clamping were greater with increasing severity of ipsilateral ICA stenosis. The correlation between CsO(2) and TCD on external clamping, although less strong than that on internal clamping, was statistically significant r = 0.32; P =.01; Spearman rank correlation). CONCLUSIONS: The falls in TCD and CsO(2) were of a similar order of magnitude and must therefore reflect a fall in cerebral perfusion. The ipsilateral ECA contributes significantly to intracranial blood flow and oxygen saturation in severe carotid stenosis.

Relationship between endothelial cell markers and arterial stenosis in peripheral and carotid artery disease.

Damage to the endothelium is an important component of atherosclerosis and can be quantified by measuring plasma markers, such as von Willebrand factor, thrombomodulin, intercellular adhesion molecule-1, and E-selectin. We hypothesized that increased levels of these markers would be related to objectively defined disease severity among patients with peripheral atherosclerosis or carotid atherosclerosis. To test this, we measured the markers by using ELISA in the plasma of 45 patients with intermittent claudication alone and in 53 patients presenting with transient ischemic attack. Disease severity in the former was by ankle-brachial pressure index and in the latter by ultrasound defined % stenosis. Any symptomatic dual disease or history or present coronary atherosclerosis warranted exclusion. Data were correlated according to Spearman's method. The only significant correlation was between von Willebrand factor and ankle-brachial pressure index (r = -0.39, p = 0.008). Our data suggest that von Willebrand factor is the most sensitive marker of peripheral atherosclerosis and that none of the plasma markers seems to be a useful marker of the degree of carotid artery stenosis.

Should heparin be reversed after carotid endarterectomy? A randomised prospective trial.

OBJECTIVE: To investigate whether heparin reversal after carotid endarterectomy reduces the incidence of haemorrhagic complications. DESIGN: A randomised prospective trial. METHODS: Sixty-four patients randomised to reversal of heparin or no reversal, of whom 31 received protamine titrated to the residual circulating heparin at closure of arteriotomy. Measurements included serial activated clotting times (ACTs), wound drainage, neck swelling using duplex Doppler imaging to measure the depth from skin to carotid bifurcation, and the recording of all complications. RESULTS: Wound drainage volumes were significantly reduced by protamine reversal (68.5 ml compared to 35 ml, p < 0.001), but neck swelling was not (72 mm compared to 70 mm, p = 0.77). Two patients who were not reversed developed neck haematomas requiring evacuation. More importantly, two patients receiving protamine, thrombosed the operated internal carotid artery (ICA) postoperatively and died despite urgent thrombectomy. A further patient who was not randomised in this study but who received protamine also developed ICA thrombosis within the same 3 month period. CONCLUSIONS: Reversing heparin with protamine reduces postoperative wound drainage after carotid surgery but may predispose to ICA thrombosis and stroke. This is in keeping with a previous retrospective study published during our trial.

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.

Facilitation of peripheral intravenous access: an evaluation of two methods to augment venous filling.

STUDY OBJECTIVE: To evaluate two methods of augmenting venous filling as potential aids to i.v. cannulation. DESIGN: Comparative study of cross-sectional areas of preselected antecubital fossa veins. SETTING: Vascular laboratory of a British university teaching hospital. PARTICIPANTS: Thirty healthy, normotensive, adult volunteers. INTERVENTIONS: Vessel cross-sectional areas measured noninvasively using a color flow duplex ultrasound scanner. Measurements were taken at rest, after application of a venous tourniquet, with tourniquet and Esmarch bandage, and with tourniquet and Rhys-Davies exsanguinator. RESULTS: Mean (+/- SD) cross-sectional area at rest was 0.18 +/- 0.094 cm2 and after tourniquet was 0.28 +/- 0.14 cm2. Application of an Esmarch bandage produced an increase to 0.33 +/- 0.14 cm2, and Rhys-Davies exsanguinator produced an increase to 0.32 +/- 0.15 cm2 (P < .0001 for all comparisons except Rhys-Davies exsanguinator versus Esmarch bandage). CONCLUSION: Application of either the Esmarch bandage or the Rhys-Davies exsanguinator caused significant filling of antecubital fossa veins in excess of that produced by a venous tourniquet alone in normovolemic, normotensive volunteers.

Cerebral hypoxia detected by near infrared spectroscopy.

Near infrared spectroscopy is a relatively new technique for monitoring intracerebral oxygen saturation. Using the technique, three episodes of cerebral hypoxia were detected during elective carotid endarterectomy which were not reliably recorded by more standard monitoring of cerebral perfusion. In one case, cerebral hypoxia was related to slippage of the tracheal tube into the right main bronchus and in the other two to episodes of hypotension. Near infrared spectroscopy is a reliable indicator of peripheral cortical perfusion and provides continuous and noninvasive monitoring of intracerebral oxygen saturation.

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.

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.