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Biomedical subjects

H Sillesen

Publications and source records attributed to H Sillesen.

52 records · Page 3Linked to original sources
PubMed1988

Quantitative Doppler ultrasound evaluation of occlusive arterial disease in the lower limb.

Forty consecutive patients with lower limb arterial disease were evaluated using a multi-gated pulsed Doppler system. Doppler signals were sampled at 4 sites in each limb, and following spectral analysis, the pulse rise time (PRT) was measured. The value obtained at the location giving the longest duration of PRT was used for comparison with ankle/brachial pressure index (A/B index) and angiography. A highly significant correlation was found between PRT and A/B index (r = -0.75, P less than 0.001). Based on receiver operating characteristic curves an overall diagnostic accuracy of 90% in diagnosing a pressure reduction greater than 20% was obtained. The diagnostic accuracy in detecting an angiographic stenosis greater than 50% was almost identical. Based on combined quantitative and qualitative analysis of Doppler signals sampled at the common femoral and popliteal artery, the aorto-iliac segments and the femoro-popliteal segments were evaluated separately. Comparison with arteriography revealed overall accuracies of 96% in the aorto-iliac segments and 87% in the femoro-popliteal segments. It is concluded that simple quantitatively measurable parameters in the Doppler spectrum may accurately predict and localize hemodynamically significant arterial lesions of the lower extremities.

Adult↗
PubMed1988

Haemodynamic evaluation of the cerebral circulation by periorbital Doppler examination and cerebral blood flow (CBF) measurement in carotid artery disease.

To assess the haemodynamic significance of an internal carotid artery (ICA) stenosis, angiography or direct ultrasound examination should be supplemented by indirect physiologic testing of the collateral circulation. Among the tests proposed, we used the periorbital flow direction, assessed by Doppler technique, and cerebral blood flow reactivity to vasodilation, by i.v. xenon-133 technique, in 35 patients before carotid endarterectomy. The results were related to the actual perfusion pressures, measured during surgery in the distal ICA. All 15 patients with normal orthograde periorbital flow had normal cerebral blood flow (CBF) vasoreactivity and no, or only minor, reduction in ICA perfusion pressure. Of the 20 patients with inverted flow, 12 had normal and 8 had abnormal CBF reactivity. These 8 patients proved to have significantly lower cerebral perfusion pressures, as compared with the remaining 12 patients with inverted periorbital flow (p less than 0.001), who in turn had lower perfusion pressures than the 15 patients with orthograde flow (p less than 0.005). Based on these results, we suggest periorbital Doppler examination as a haemodynamic adjunct to direct ICA visualization. A normal orthograde flow will most certainly rule out any severe pressure reduction. By measuring CBF at rest and following vasodilation in cases with inverted flow, most patients with severe reduction in cerebral perfusion pressure may be identified.

Adult↗
PubMed1988

Middle cerebral artery occlusion in presence of low perfusion pressure increases infarct size in rats.

A model was set up in order to evaluate the importance of hemispheric perfusion pressure when the middle cerebral artery (MCA) is occluded in anaesthetized rats. In 6 animals the internal carotid artery (ICA) was occluded prior to ipsilateral MCA occlusion; in 17 animals the MCA only was occluded; 6 animals underwent the same preparation, but the vessels were left unoccluded. Four days after surgery the infarct volume was measured with a computerized image analyser. The infarcted areas were significantly larger in the ICA + MCA occluded group compared with the MCA occluded group (p less than 0.005), which in turn had larger infarcts than the sham-operated animals (p less than 0.001). These results indicate that patients with hypoperfusion, due to severe ICA stenosis and impaired collateral blood supply, are at higher risk of developing major stroke, when embolism into a cerebral artery occurs, as compared to patients with no, or only minor, reduction in hemispheric perfusion pressure.

Animals↗
PubMed1988

Pulsed multigated Doppler ultrasonography in the diagnosis of carotid artery disease.

To evaluate the accuracy of a pulsed multigated Doppler system, 128 carotid arteries were examined. The spectral broadening index was calculated from the power spectrum of a small sample volume located in the center of the stream according to the flow profile and was related to the degree of stenosis as determined by contrast angiography. Even minor wall irregularities seen on the angiogram were classified as disease. The ability of the system to discriminate between normal and diseased vessels reached a sensitivity of 94% and a specificity of 91%. Classification of greater than 50% or less than 50% stenosis could be performed with a sensitivity of 90% and a specificity of 85%. Pulsed multigated Doppler ultrasonography allows identification of even minor degrees of stenosis of the carotid artery and provides an alternative to duplex scanning. Furthermore, the blood flow profile provided by a multigated Doppler system may add valuable information concerning blood flow characteristics not obtainable by single-gated systems.

Adult↗
PubMed1987

Doppler examination of the periorbital arteries adds valuable hemodynamic information in carotid artery disease.

The periorbital flow direction and internal carotid artery (ICA) angiogram were compared to the ICA pressure gradient across the stenosis and the distal ICA pressure in 51 patients subjected to carotid endarterectomy. All 17 patients with inverted periorbital flow had stenoses exceeding 50%. The remaining 16 patients with the same degree of stenosis had antegrade flow, which was also observed in all patients with less than 50% stenosis. In 16 of 17 patients with inverted periorbital flow, the mean pressure gradient exceeded 10 mmHg, whereas 33 of 34 patients with antegrade flow had gradients of 12 mmHg or less. For diagnostic purpose, the periorbital Doppler test is inferior to direct Doppler examination or angiography. However, as an adjunct to direct techniques, patients can be classified into 3 groups: Patients with less than 50% stenosis, Patients with 50% stenosis or more and good collaterals and, Patients with 50% stenosis or more and insufficient collaterals.

Arteries↗
PubMed1987

The clinical use of objective quantification of flow disturbance in carotid artery disease: correlation between spectral broadening index and arteriography.

In order to assess the accuracy of objective quantification of carotid flow disturbance, 147 carotid arteries were examined with continuous wave (CW) Doppler technique. The systolic spectral broadening index (SBI), determined as (maximum-mean)/maximum frequency, was calculated from the power spectrum and together with the peak frequency related to the angiographic degree of stenosis. Receiver operating characteristics curves were calculated and the SBI predicted disease with a specificity of 94%. On the other hand, the ability of the SBI to discriminate minor disease was not satisfactory. Both the SBI and the peak frequency were accurate in discriminating between greater or less than 50% stenosis. The study concludes that using CW Doppler the SBI can reliably predict carotid artery stenoses. For exclusion of minor lesions an additional test should be performed, e.g., pulsed Doppler spectral analysis.

Angiography↗
PubMed1987

Carotid endarterectomy in patients with occlusion of the contralateral carotid artery. Perioperative risk and late results.

Recent reports on the outcome of carotid endarterectomy in patients with contralateral occlusion have been conflicting. Therefore, we reviewed 51 cases identified, among 675 consecutive carotid endarterectomies. A perioperative mortality of 2% and a permanent morbidity rate of 16% was observed. Compared with a complication rate of about 5% previously reported from this institution, this clearly indicates contralateral carotid occlusion as a major risk factor in carotid surgery. Though not statistically significant, patients with severely reduced cerebral perfusion pressure (CPP) had suffered more severe strokes when compared to patients with only minor reduction in CPP. In addition, the internal carotid artery blood flow following endarterectomy was significantly higher in the low pressure group (P less than 0.02). No patients were lost during follow-up, for a mean of 34 months. The cumulative five-year survival rate was 74%, not significantly different from the expected survival of an age and sex matched population. During the period of follow-up 16 patients experienced new neurologic symptoms, in six (2 strokes and 4 TIA's) referable to the hemisphere ipsilateral to operation and in 10 (2 strokes and 8 TIA's) referable to the contralateral hemisphere. The five-year stroke rate was 16%. This together with the observed survival rate indicated a better-than-expected course in this group of patients with severe cerebrovascular atherosclerosis.

Carotid Artery Diseases↗
PubMed1987

Intracerebral haemorrhage after carotid endarterectomy.

Among 662 consecutive carotid endarterectomies eight cases of postoperative ipsilateral intracerebral haemorrhage were identified, occurring into brain areas which, preoperatively were without infarction. As blood pressures across the stenosis were routinely measured during surgery, the internal carotid artery (ICA) perfusion pressure could be related to the occurrence of haemorrhage. In addition, cerebral blood flow (CBF) was studied with the intravenous xenon-133 technique in four patients and histopathologic examination of the brain was available in four patients who died subsequent to their haemorrhage. All eight patients had a high grade of ICA stenosis and a marked reduction of ICA perfusion pressure (average of 40%) which was significantly greater than that observed (average of 6%) in the other patients undergoing carotid surgery (P less than 0.0001). Relative hyperperfusion of the ipsilateral hemisphere was seen in the four patients studied postoperatively. In at least two cases the haematoma was preceded by an asymptomatic postoperative ischaemic infarct. Histologic examination did not confirm previous findings of changes resembling those seen in malignant hypertensive encephalopathy. These results substantiate the view, that patients at risk of haemorrhage after endarterectomy are those with a low preoperative cerebral perfusion pressure and postoperative hyperperfusion. Postoperative silent brain infarction is an additional risk factor.

Adult↗
PubMed1987

Dihydralazine induces marked cerebral vasodilation in man.

Dihydralazine is widely used for acute control of hypertension. In experimental studies it seems to dilate cerebral resistance vessels and increase intracranial pressure. However, the effect on cerebral blood flow (CBF) in man has been little studied. Measurements of CBF were performed with the i.v. xenon-133 technique in seven young, normotensive volunteers before and 15, 60 and 180 min after 6.25 mg i.v. dihydralazine, corresponding approximately to 0.1 mg kg-1 body weight. For comparison the CBF reactivity to inhalation of 5% CO2 in air was investigated. Dihydralazine increased CBF throughout the period of study, in median 16, 27 and 23% at the three periods of measurements, respectively. The arterial blood pressure remained unchanged, whereas heart rate increased significantly. During CO2 inhalation, CBF increased on average 29%. Thus, the cerebral vasodilation exerted by a small i.v. dose of dihydralazine was of the same order of magnitude as the effect of 5% CO2 inhalation. These results in normal subjects should be extrapolated to diseased persons only with extreme caution. Still, the very marked and long lasting vasodilation observed suggests that dihydralazine, from a theoretical point of view, in certain clinical situations may be harmful.

Adult↗
PubMed1987

Cerebral hyperperfusion following carotid endarterectomy.

Serial measurements of cerebral blood flow (CBF) were performed in 56 patients before and one to four times after uncomplicated carotid endarterectomy. The findings were related to the ratio between internal carotid artery (ICA) and common carotid artery (CCA) mean pressures. Within the 1st postoperative day CBF increased by a median of 37% in the ipsilateral and 33% in the contralateral hemisphere. Later recordings showed a gradual return of CBF toward the preoperative level. Sixteen patients with an ICA/CCA pressure ratio below 0.7 showed a significantly more pronounced and longer-lasting flow increase than did 40 patients with a ratio above this level. On Day 1, the median CBF increase in the ipsilateral hemisphere was 61% and 24% in the two groups, respectively (p less than 0.01). A significant improvement in side-to-side asymmetry, resulting from a higher gain in the ipsilateral hemisphere, occurred in the low pressure ratio group, while the hemispheric asymmetry on average was unchanged in the high pressure ratio group. This relative hyperemia was most pronounced 2 to 4 days following reconstruction. The marked hyperemia, absolute as well as relative, in patients with a low ICA/CCA pressure ratio suggests a temporary impairment of autoregulation. Special care should be taken to avoid postoperative hypertension in such patients, who typically have preoperative hypoperfusion, to avoid the occurrence of cerebral edema or hemorrhage.

Adult↗
PubMed1986

Staged bilateral carotid endarterectomy.

In a series of 56 staged bilateral carotid endarterectomies, new neurologic symptoms developed in 5% and 20% following the first and second procedure, respectively. All complications were transient or minor. The incidence of postendarterectomy hypertension was significantly higher following the second procedure, when operations were staged less than 3 weeks apart. A correlation between these hypertensive episodes and the occurrence of new neurologic symptoms could not be shown. However, as this correlation has been proved in several other reports, bilateral carotid endarterectomy is advised to be staged at least 3 weeks apart. In addition, a conservative attitude towards contralateral asymptomatic lesions is proposed.

Adult↗
PubMed1983

Analgesic, respiratory and endocrine responses in normal man to THIP, a GABA-agonist.

In a controlled study, the effects of THIP (a synthetic gamma-aminobutyric-acid-agonist) on respiratory function (ventilatory response to CO2), first detection of stimulation (electrical stimulation of a tooth), pain threshold, magnitude of maximal tolerated pain stimulation, and plasma cortisol, prolactin and glucose were investigated in six normal men. Intramuscular injection of THIP in dosages of both 10 mg and 20 mg increased the magnitude of stimulus before first detection, and the pain threshold as well as the maximal tolerance of pain stimulation. THIP did not lead to changes in respiratory function, or in plasma cortisol, prolactin or glucose, suggesting an analgesic action independent of opiate receptors.

Adult↗
PubMed1983

Pharmacokinetics of the gamma-aminobutyric acid agonist THIP (Gaboxadol) following intramuscular administration to man, with observations in dog.

The pharmacokinetics of the gamma-aminobutyric acid (GABA) agonist, THIP (Gaboxadol) has been studied following intramuscular administration of 10 or 20 mg THIP-monohydrate to six healthy human volunteers. Additional experiments with special reference to the possible occurrence of non-linear kinetics and to estimation of the efficiency of absorption were carried out in three beagle dogs. As estimated from the dogs, absorption of THIP from the site of injection was efficient (F = 0.94 +/- 0.16, mean +/- S.D., in 8 experiments). The time course of the THIP serum concentration was in all experiments adequately described by an open 1-compartment linear model. In most individual experiments a near maximum concentration was present at 15 or 10 min. after the administration to man and dog, respectively. In some subjects and dogs an uncertain relation was found between dose and the time integral of the THIP serum concentration, but the mode of variation did not suggest deviations from first-order kinetics at high doses or concentrations. The rate constant of elimination was estimated to 0.50 +/- 0.13 hr-1 and 0.52 +/- 0.13 hr-1 following injection of a 10 or 20 mg dose, respectively, to man (mean +/- S.D., n = 6), and similar values were obtained from the dogs.

Absorption↗
PubMedDate not supplied

Echo-lucency of computerized ultrasound images of carotid atherosclerotic plaques are associated with increased levels of triglyceride-rich lipoproteins as well as increased plaque lipid content.

BACKGROUND: Echo-lucency of carotid atherosclerotic plaques on computerized ultrasound B-mode images has been associated with a high incidence of brain infarcts as evaluated on CT scans. We tested the hypotheses that triglyceride-rich lipoproteins in the fasting and postprandial state predict carotid plaque echo-lucency and that echo-lucency predicts a high plaque lipid content. METHODS AND RESULTS: The study included 137 patients with neurological symptoms and > or = 50% stenosis of the relevant carotid artery. High-resolution B-mode ultrasound images of carotid plaques were computer processed to yield a measure of echogenicity (gray-scale level). Lipoproteins were measured before and hourly for 4 hours after a standardized fatty meal. A subgroup of 58 patients underwent endarterectomy. On linear regression analysis, echo-lucency (low gray-scale level) was associated with elevated levels of fasting and postprandial plasma triglycerides (P=.0002 and P=.002), IDL cholesterol (P=.0009 and P=.006), and VLDL/chylomicron remnant cholesterol (P=.0003 and P=.0004) and triglycerides (P=.0003 and P=.003), the area under the plasma triglyceride curve 0 to 4 hours after a fatty meal (P=.001), and body mass index (P=.0001). On ANCOVA, body mass index, fasting IDL cholesterol, and fasting plasma triglycerides were independent predictors of echo-lucency. Echo-lucency was associated with increased relative plaque lipid content (P=.02). CONCLUSIONS: Increased plasma levels of triglyceride-rich lipoproteins predict echo-lucency of carotid plaques, which is associated with increased plaque lipid content. Because echo-lucency has been associated with a high incidence of brain infarcts on CT scans, triglyceride-rich lipoproteins may predict a plaque type particularly vulnerable to rupture.

Arteriosclerosis↗
PubMedDate not supplied

Hemodynamic effect of carotid endarterectomy.

Cerebral blood flow was measured by the intravenous xenon-133 technique at rest and during cerebral vasodilation with acetazolamide in 32 patients before and after uncomplicated carotid endarterectomy. The results were compared with the internal carotid artery perfusion pressure measured during surgery. A significant improvement in side-to-side cerebral blood flow asymmetry occurred in 6 patients studied at baseline and in 11 patients during provoked cerebral vasodilation. These patients all belonged to a group of 14 patients who, in addition to a severe stenosis of the internal carotid artery, presented a reduction in cerebral perfusion pressure of at least 20%. No improvements occurred in 18 patients with no or only minor reduction in perfusion pressure, irrespective of the degree of stenosis. These findings indicate an improved perfusion reserve following carotid endarterectomy in most patients with marked reduction in perfusion pressure, whereas only some of these patients will experience an improvement in baseline cerebral blood flow.

Acetazolamide↗