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Biomedical subjects

S C Whitaker

Publications and source records attributed to S C Whitaker.

At least 37 records · Page 2Linked to original sources
PubMed1997

The anatomy of abdominal aortic aneurysms: implications for sizing of endovascular grafts.

OBJECTIVE: To determine the full range of aorto-iliac anatomy of patients with abdominal aortic aneurysms (AAAs) and thence the range of endovascular graft sizes required to deal with the majority of AAAs. DESIGN: Analysis of preoperative spiral CT measurements. MATERIALS: One hundred and sixty-eight patients with AAAs. METHODS: Multiplanar reconstruction measurements were taken of proximal aortic neck diameter and length, lowermost renal artery to the aortic bifurcation distance and length and diameter of common iliac arteries. Based on these measurements a range of graft sizes that would fit the majority of AAAs was determined. RESULTS: Ranges of anatomical variables were as follows: proximal aortic neck diameter 18-30 mm, renal artery to aortic bifurcation distance 93-210 mm, common iliac artery length 13-108 mm, common iliac artery diameter 6-67 mm. Over 750 graft sizes would be required to cover all anatomical combinations using a one-piece aorto-uni-iliac graft. CONCLUSION: A wide variety of aorto-iliac anatomy exists in patients with AAAs. The large number of graft sizes required to deal with the majority of AAAs makes the production of one-piece endovascular grafts commercially impractical. A proposed two-piece modular graft would allow the majority of AAAs to be treated using only 16 graft sizes.

Aged↗
PubMed1997

Influence of abdominal aortic aneurysm size on the feasibility of endovascular repair.

PURPOSE: To assess the effect of abdominal aortic aneurysm (AAA) size on overall aneurysm morphology with special attention to possible relationships among various anatomic variables that determine the feasibility of endovascular repair. METHODS: One hundred sixty-eight patients were assessed with spiral computed tomographic angiography to measure the length and diameter of the AAA, the proximal neck, and the common iliac arteries. Anatomic variables were correlated with aneurysm size using Spearman's rank order correlation coefficients (rS); comparisons among small, intermediate, and large aneurysms were made using the Chi-square test. RESULTS: Correlations between aneurysm size and the anatomic variables above were weak. The strongest association was between aneurysm size and aortic length (rS = 0.41, p < 0.001). Subgroup analysis showed no difference in proximal neck length, neck diameter, or overall suitability for endovascular repair between aneurysms greater or smaller than 5.5-cm diameter. However, significantly more short (< 1.5 cm), wide (> 3 cm), and hence, unsuitable proximal necks were found in patients with aneurysms > 7 cm in diameter (chi 2 = 7.8, p < 0.01). CONCLUSIONS: Shortening and widening of the proximal neck seems to increase with aneurysm size but only after the aneurysm expands beyond 7 cm in diameter. Aneurysms with diameters in the 4.5- to 5.5-cm range are no more suitable for endovascular repair than those between 5.5 and 7 cm. The lack of any significant correlation between anatomic variables emphasizes the need for accurate preoperative assessment of the anatomy of each individual patient before endovascular repair.

Aorta, Abdominal↗
PubMed1997

Results of 100 cases of pulse-spray thrombolysis for acute and subacute leg ischaemia.

BACKGROUND: Pulse-spray thrombolysis is a rapid technique for the treatment of limb ischaemia of recent onset. Early results have been published but the longer term results are not known. METHODS: This study consisted of a series of 100 legs with acute and subacute ischaemia treated using this method with a follow-up interval of up to 3 years. Eighty-three limbs were classified as Fontaine grade III or IV and 42 had a sensory or motor deficit. Sixty-seven limbs were treated with pulse spray alone and 33 had an additional low-dose infusion. In 71 cases an additional catheter-directed intervention was required. RESULTS: Median duration of lysis was 135 (range 35-1540) min and median dose of recombinant tissue plasminogen activator used was 18 (range 4-61) mg. Complete radiological patency was achieved in 79 limbs and the ankle:brachial pressure index improved from a median of 0 (range 0-0.8) to 0.8 (range 0-1.5) (P < 0.0001). At 30 days ten patients had died, eight needed amputation and a further 11 had rethrombosed. Cumulative limb salvage rate at 30 months was 79 per cent (standard error 8) and the estimated cumulative patency rate for successful cases was 72 per cent (standard error 10). The incidence of major bleeding was 7 per cent and of minor bleeding 24 per cent. There were no haemorrhagic strokes but three thrombotic strokes occurred within 30 days of thrombolysis. CONCLUSION: Pulse-spray thrombolysis achieves rapid and safe revascularization of acute and subacute leg ischaemia.

Adult↗
PubMed1997

Anatomical suitability of abdominal aortic aneurysms for endovascular repair.

BACKGROUND: Aortic aneurysm anatomy is crucial when considering patients for endovascular repair. The aim of this study was to determine the proportion of patients with aortic aneurysm suitable for endovascular repair with three different graft-stent systems. METHODS: Spiral computed tomographic angiography was used to assess the anatomy of 154 abdominal aortic aneurysms. Measurements were made of aneurysm neck length and diameter, renal artery to aortic bifurcation length, common iliac artery diameter and length, and external iliac artery diameter. Aneurysms were assessed for anatomical suitability for currently available aortoaortic, aortobi-iliac and aortouni-iliac devices. RESULTS: Six patients (4 per cent) had a distal aortic neck suitable for implantation of a straight aortic graft. Fifteen patients (10 per cent) had arterial anatomy suitable for implantation of a bifurcated graft and 85 (55 per cent) patients were suitable for endovascular repair with an aortouni-iliac graft. The primary reasons for unsuitability were: proximal neck length less than 1.5 cm (44 patients), proximal neck diameter greater than 3.0 cm (12), and angulation of the proximal neck (three). A further ten patients were considered unsuitable for an aortouni-iliac graft because of bilateral common iliac artery aneurysms (four), tortuous iliac arteries (four) and narrow external iliac arteries (two). CONCLUSION: The aortouni-iliac device has the widest applicability of the currently available endovascular systems but open repair remains the only option for a large proportion of patients.

Aged↗
PubMed1996

Lymphoscintigraphy and colour Doppler sonography in the assessment of leg oedema of unknown cause.

Oedema of the lower limbs may be associated with a number of factors, most commonly a lymphatic or venous abnormality. Generally effective treatment options are only available with venous disorders. The aim of this study is to show that a combination of duplex Doppler sonography and lymphoscintigraphy in patients with limb oedema will help to determine the aetiology and thus identify patients for whom treatment is appropriate. 32 patients presenting with unexplained oedema involving the lower limb have been studied. Each patient underwent Doppler sonography followed by lymphoscintigraphy. In 16 patients the lymphoscintigraphy was abnormal, showing absent or poorly visualized lymphatics. The Doppler study was abnormal in 17 patients, nine of whom went on to receive definitive surgical treatment. In five patients both studies were abnormal and there were six cases where both investigations were normal. It is concluded that in the great majority of referrals (82%), the combination of lymphoscintigraphy and Doppler ultrasound is a satisfactory means of assessment of patients with unexplained limb oedema.

Adolescent↗
PubMed1995

Immediate and early follow-up results of purse spray thrombolysis in patients with peripheral ischaemia.

Pulse spray thrombolysis is a technique of accelerated peripheral thrombolysis which has been evaluated in 38 patients, 29 with threatened limb viability and nine with a viable but critically ischaemic limb. The median length of occlusion was 26.5 (range 3-65) cm. The lytic agent used was recombinant tissue plasminogen activator (rtPA), injected manually via a pulse spray catheter at a concentration of 0.33 mg/ml and a bolus size of 0.2 ml. The median total dose of rtPA was 18 (range 5-35)mg. Patency and flow were completely restored in 34 of 38 patients and clinical success at 30 days was maintained in 27 of 38. The median lysis time was 120 (range 35-1125) min, compared with a median duration of 1545 (range 42-5760) min in 120 consecutive patients previously treated with conventional low-dose infusion thrombolysis using rtPA. This represents a 12-fold reduction in lysis time (P < 0.001). The overall estimated cumulative limb salvage rate for the 38 patients who entered the study was 84 per cent and the cumulative patency rate for the 34 patients in whom patency was restored was 74 per cent at 18 months follow-up. Pulse spray thrombolysis rapidly restores patency with good limb salvage at 30 days; the benefit is sustained even in patients with limbs at immediate risk of irreversible ischaemic injury who are not considered suitable for conventional thrombolysis.

Adult↗
PubMed1995

Prospective randomised comparative study of pulse spray and conventional local thrombolysis.

OBJECTIVES: To compare the time required to achieve lysis with the pulse spray technique and the conventional slow continuous infusion technique. DESIGN: Prospective randomised open Study. METHODS: Eighteen patients suitable for intra-arterial thrombolytic therapy with conventional and pulse spray technique were randomised 1:1 to receive either pulse spray thrombolysis with 0.33 mg/ml rt-PA injected as a bolus of 0.2 ml or conventional thrombolysis with 0.05 mg/ml rt-PA infused at a rate of 10 ml/h. RESULTS: The age, duration of symptoms, length of occlusion and prethrombolysis ankle brachial pressure index were comparable in the two groups. The median duration of thrombolytic therapy in the pulse spray group was 195 min (range 90-1260) compared to 1390 min (range 300-2400) in the Conventional group. The difference between the two groups was significant, p < 0.002 (Mann-Whitney test). CONCLUSIONS: Significantly shorter time is required to achieve local thrombolysis with pulse spray compared to the conventional infusion method.

Aged↗
PubMed1995

Carbon dioxide: an alternative to iodinated contrast media.

OBJECTIVES: To study the use of carbon dioxide as a contrast medium for arteriography. METHODS: Carbon dioxide was used as a contrast medium for intra-arterial digital subtraction lower limb angiography in 12 examinations on 11 patients. RESULTS: No complication was encountered and no significant changes occurred in the arterial pH, PaCO2 and PaO2. The quality of images as assessed by an independent observer was adequate for the majority of the vessels (77%). CONCLUSIONS: Carbon dioxide is a safe alternative in patients at an increased risk of adverse reaction to iodinated ionic or non-ionic contrast medium and is very cheap.

Aged↗
PubMed1995

Eye splashes during invasive vascular procedures.

In recent years there has been an increased awareness among health care workers regarding possible risk of nosocomial transmission of blood borne pathogens. The aim of this study is to document the risk of contamination of radiologists' eyes during invasive vascular procedures. Radiologists performing these examinations were asked to wear glasses throughout. After each examination the glasses were inspected for droplets. 150 procedures were performed on 123 patients (M = 80, F = 43). 10 procedures (6.7%) resulted in splashes to glasses. In four of these cases the radiologist was not aware of the "eye splash" nor was there a spray event to account for it. Radiologists were aware of 13 spray events (8.7% of all procedures). There was a significantly increased risk of spray events and eye splashes during thrombolysis (chi 2 = 14.93, p < 0.001) and of spray events during angioplasty when compared with perfemoral arteriography (chi 2 = 8.816, p < 0.01). Procedures lasting longer than 30 min were associated with a significantly increased risk of spray events (chi 2 = 5.63, p < 0.02). Significantly more eye splashes were associated with more than two catheter changes (chi 2 = 8.912, p < 0.01). It is suggested that protective eye wear should be used routinely during invasive vascular procedures.

Angiography↗
PubMed1994

Transfemoral endoluminal repair of abdominal aortic aneurysm with bifurcated graft.

Traditional open repair of abdominal aortic aneurysm has disadvantages. We present our experience of transfemoral endoluminal repair with a bifurcated graft system. 29 patients with aortic aneurysm over 5.5 cm in diameter and 1 with a 3.2 cm aneurysm and bilateral iliac stenosis were assessed; 5 were suitable for the procedure. The operation was successful in all the patients, without haemodynamic compromise or major complications. This technique has the potential to reduce morbidity and mortality from abdominal aortic aneurysm. Further modifications are required to make it applicable to most aneurysms.

Aged↗
PubMed1994

Experience with pulse-spray technique in peripheral thrombolysis.

Pulse-spray thrombolysis (PST) is a new technique of accelerated peripheral arterial thrombolysis. This technique has been evaluated on 24 patients with limb ischaemia. Severe acute limb-threatening ischaemia with sensory and motor deficit was present in 11/24 (45.8%) patients. The median dose of recombinant tissue plasminogen activator (rt-PA) used was 18 mg (10-35 mg) injected in a concentration of 0.33 mg/ml and bolus size of 0.2 ml. The median length of occlusions treated was 23 cm (range 4-55 cm). Complete initial lysis was achieved in 23/24 (95.8%) and limb salvage at 30 days was achieved in 18/24 (75%) of the cases. The overall 30-days mortality was 4/24 (16.6%) and 2/4 (50%) in those who required surgical intervention. The median duration of thrombolytic treatment was 137.5 minutes (range 35-1125 minutes) which is an 11-fold and significant reduction (p < 0.001, Mann-Whitney) in lysis time compared with the results of conventional low dose infusion of rt-PA at a rate of 0.5 mg/h in 120 consecutive patients in our unit. PST rapidly restores vascular patency and may become the treatment of choice for acute limb ischaemia including those at immediate risk of irreversible ischaemic injury which would not be considered suitable for conventional thrombolysis.

Adult↗
PubMed1993

Peripheral arterial thrombolysis: intermediate-term results.

To determine the intermediate-term results of intra-arterial thrombolysis, 127 consecutive patients receiving 129 courses of treatment were reviewed at a median follow-up of 3 years. At initial review, 30 days after treatment, thrombolysis was successful in 63 cases (49 per cent). Of these patients, 16 were lost to follow-up: 15 died without further vascular symptoms and one moved from the area. Some 35 patients were alive and asymptomatic, of whom 33 had either angiographic or clinical evidence of continued arterial patency. Symptomatic reocclusion occurred in 12 cases; a further two patients remained asymptomatic and reocclusion was detected at follow-up. Two of the 12 symptomatic patients required amputation. Estimated patency rates were 80 per cent at 1 year, 72 per cent at 2 years and 70 per cent at 3 years. The intermediate-term results in the 66 cases in which lysis was unsuccessful were worse, only 16 patients (24 per cent) surviving to follow-up with the treated limb intact. It is concluded that, if thrombolysis is successful at 30 days, the intermediate-term results are good.

Adult↗
PubMed1993

The role of angiography in the investigation of acute or chronic gastrointestinal haemorrhage.

We have reviewed the clinical details and radiology of all patients with non-variceal gastrointestinal haemorrhage referred for angiography during an 8 year period. Forty-six patients with a history of overt bleeding had 49 technically satisfactory angiograms of which 29 were true positives but 16 were false negatives (sensitivity 64%, accuracy 63%). The accuracy of angiography in this group was much higher (92%) in those patients referred within 24 h of admission. Nine patients who had a history of iron-deficiency anaemia due to sub-acute blood loss had 9 angiograms. Five studies in this group were correct (two true negatives and three true positives) but there were four false positive studies. Angiography is an effective means of diagnosis in patients with acute gastrointestinal haemorrhage who have a negative endoscopy but best results will only be achieved when the study is performed with minimal delay following negative endoscopy. Angiography should also be considered in patients with continuing subacute blood loss when other investigations are negative.

Acute Disease↗
PubMed1993

The value of scintigraphic studies in the assessment of patients with acute or chronic gastrointestinal haemorrhage.

The scintigrams of 76 patients with gastrointestinal bleeding referred over an 8 year period have been reviewed together with their subsequent clinical course. Twenty-five patients had either 99Tcm-sulphur colloid or 99Tcm-labelled red cell scintigraphy to localize a source of active bleeding. Fourteen patients had 99Tcm-sulphur colloid scintigraphy, of which seven were false negatives, two were false positives and two were true positives. Eleven patients had 12 99Tcm-labelled red cell scintigrams, of which three were false negatives, one was a false positive and four were true positives. Fifty patients had 99Tcm-pertechnetate scintigraphy to look for ectopic gastric mucosa in Meckel's diverticula. There were 43 true negatives, two false negatives, two true positives and three false positives in this group. Our results emphasize the need for caution in interpreting nuclear medicine studies in patients with blood loss from the gastrointestinal tract.

Acute Disease↗