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Biomedical subjects

M Kaps

Publications and source records attributed to M Kaps.

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

S-100 protein and neuron-specific enolase concentrations in blood as indicators of infarction volume and prognosis in acute ischemic stroke.

BACKGROUND AND PURPOSE: Better techniques are needed to monitor infarction volume and predict neurological outcome after ischemic brain infarction. We evaluated the usefulness of serial measurements of S-100 protein versus neuron-specific enolase (NSE) in blood samples from patients with acute stroke. METHODS: Using nonisotopic sandwich immunoassays, we measured plasma concentrations of S-100 protein and NSE on admission and on days 3, 4, 7, and 14 after infarction in 44 patients (age range, 22 to 86 years; mean age, 65.1 years; 12 female, 32 male). Infarct volume was measured by volumetric CT on day 4 after ictus, and clinical outcome was assessed at discharge from hospital with the Activities of Daily Living Scale and 6 months after infarction with the Glasgow Outcome Scale. RESULTS: Peak blood levels of S-100 protein were found on day 2.5 +/- 1.3, and peak levels of NSE were found on day 1.9 +/- 0.8 after infarction. Peak plasma levels of S-100 protein correlated well with infarct volume (r = .75, P < .001) and with clinical outcome assessed with the Glasgow Outcome Scale (r = .51, P < .001). Serum levels of NSE correlated with infarct volume (r = .37, P < .05) but not with clinical outcome (r = .18, P > .05). CONCLUSIONS: The results of our study indicate that measuring blood concentrations of S-100 protein periodically in the first 10 days after cerebral infarction helps to predict infarct volume and the long-term neurological outcome more accurately than periodic measurements of blood concentrations of NSE.

Activities of Daily Living↗
PubMed1997

Oxygen inhalation can differentiate gaseous from nongaseous microemboli detected by transcranial Doppler ultrasound.

BACKGROUND AND PURPOSE: Clinically silent circulating microemboli can be detected by transcranial Doppler sonography. The composition of these emboli in different clinical conditions is unclear. METHODS: We performed 1-hour transcranial Doppler sonographic recordings from the middle cerebral or posterior cerebral artery in 20 patients with mechanical prosthetic heart valves, in 78 patients with an arterial embolic source, and in 20 control subjects. During 30 minutes of this recording, the patients inspired room air and 6 L of oxygen per minute via a loosely fitting facial mask; during the remaining 30 minutes, they breathed room air only. RESULTS: There was a significant decline of embolic signals (ES) under oxygen in the patients with mechanical prosthetic cardiac valves (144 ES without oxygen versus 63 ES with oxygen; P = .002) but not in the patients with arterial embolic sources (145 ES without oxygen versus 135 ES with oxygen; P = NS). In the control subjects, no ES were found. CONCLUSIONS: ES in patients with mechanical prosthetic cardiac valves correspond mainly to gas bubbles. Oxygen inhibits the cavitation process of mechanical prosthetic heart valves or speeds up redissolution of gas bubbles generated by cavitation. In contrast, solid microemboli originating from thrombus or atheroma cannot be suppressed by oxygen inhalation. This simple method of oxygen inhalation should help to clarify the composition of microemboli in various clinical and experimental settings.

Administration, Inhalation↗
PubMed1997

Clinically silent microemboli in patients with artificial prosthetic aortic valves are predominantly gaseous and not solid.

BACKGROUND AND PURPOSE: Microembolic signals (MES) are frequently observed by transcranial Doppler ultrasound after prosthetic heart valve implantation. Whether these MES are due to solid or gaseous particles is uncertain. We hypothesized that MES are gaseous and that if they are due to cavitation effects, their occurrence should respond to changes of dissolved oxygen concentration in the blood. METHODS: Transcranial monitoring of MES was performed in five patients with prosthetic aortic valves, who inspired 100% oxygen through a facial mask. In one patient 100% oxygen was administered under hyperbaric (2.5 kPa) conditions in a hyperbaric chamber. RESULTS: Inspiration of 100% oxygen reduced the total number of MES from 96/30 min to 2/30 min. Increasing the concentration of dissolved oxygen in the hyperbaric chamber led to an increase from 0.3 MES per minute (1.0 kPa) to 0.9 MES per minute (2.5 kPa). CONCLUSIONS: The dependence of occurrence of MES in patients with prosthetic cardiac valves on the oxygen partial pressure in blood provides strong evidence that these microemboli are gaseous.

Aged↗
PubMed1997

Bigated transcranial Doppler for the detection of clinically silent circulating emboli in normal persons and patients with prosthetic cardiac valves.

BACKGROUND AND PURPOSE: Detection of clinically silent circulating microemboli by transcranial Doppler sonography is now being widely investigated in the hope of identifying patients at increased risk for stroke. Automatic detection by bigated Doppler, which uses sampling from two different depths in the artery under study and considers the motion of the embolus, may help to define "periods of interest" that can be evaluated off-line. METHODS: In 12 normal volunteers and 10 patients with prosthetic aortic valves, we performed 1-hour recordings from one middle cerebral artery. In the normal subjects, we produced additional artifacts to use them as false-positives. Detection of microemboli was done off-line from digital audiotapes by an experienced blinded investigator (used as the gold standard) and was compared with on-line detection using specially designed software. RESULTS: With the setting used, 91.5% of all recorded artifacts could correctly be identified as such with the software. Embolic signals were detected by the software with a specificity of 59.9% and a sensitivity of 74.3%. CONCLUSIONS: Bigated Doppler adds a new dimension to the definition and detection of microembolic signals. It constitutes an important step forward toward automatic screening of stroke-prone patients. Assessing on-line periods of interest during the recording and going over the recorded data again off-line helps to save time for the discrimination of embolic signals from both the normal Doppler spectrum background and artifacts.

Aged↗
PubMed1997

Characteristics of transcranial Doppler signal enhancement using a phospholipid-containing echocontrast agent.

BACKGROUND AND PURPOSE: Ultrasound attenuation caused by the skull is a major limitation of transcranial Doppler. Echocontrast agents (EAs) may solve this problem. The aim of the present study was to investigate the characteristics of a new echocontrast agent (BY963) containing air bubbles stabilized by phospholipids. METHODS: Nine healthy volunteers received three different doses (2.5, 5.0, and 10 mL) of BY963 at an injection rate of 0.25 mL/s. The Doppler signal amplitude obtained from the middle cerebral artery was recorded with a 2-MHz pulsed-wave Doppler system. After complete decay of the signal enhancement, upward stroking of the veins of the upper arm was performed to evaluate the stability of the EA in the venous system. RESULTS: A dose-dependent increase of at least 30 dB in the Doppler signal amplitude lasted 19 to 47, 35 to 64, and 48 to 126 heart cycles (68% range) after 2.5, 5.0, and 10 mL EA, respectively. In 6 cases, there was a biphasic increase in EA enhancement. Upward stroking of the forearm, in general 12 to 18 minutes after administration, caused a Doppler signal enhancement of at least 30 dB in 6 cases. CONCLUSIONS: Each injection of BY963 caused a diagnostically relevant Doppler signal enhancement. A considerable amount of EA remained stable in the venous system for at least 12 minutes. The biphasic dose-response fits to models of dilution-indicator theory and indicates free recirculation, as well as a nonlinear washout curve.

Adult↗
PubMed1997

Harmonic imaging of the vertebrobasilar system.

BACKGROUND AND PURPOSE: Gas bubbles of ultrasound contrast agents resonate at frequencies used for diagnostic ultrasound and produce harmonics or multiples of the transmitted frequency. Processing of the second harmonic frequency results in a reduction of the signal-to-noise ratio and the signal-to-tissue artifacts. This study is the first to evaluate second harmonic imaging in the cerebral circulation. METHODS: We used a duplex system (HP SONOS 2500) in connection with a 1.8/3.6-MHz (second harmonic) and a 2.5-MHz (conventional) sector transducer. Levovist (6.5 mL; 400 mg/mL) was injected intravenously for second harmonic and conventional color duplex imaging in 13 healthy volunteers (age range, 23 to 34 [median, 29] years). RESULTS: When second harmonic imaging was compared with conventional color duplex imaging, more cerebellar arteries were detected (35 versus 31), the duration of blooming artifact was significantly reduced (7.9 versus 29.9 seconds; P = .03), and the duration of diagnostically useful signal enhancement was increased (248.5 versus 117.4 seconds; P = .0003), but the maximal investigation depth was reduced (8.4 versus 9.3 cm; P = .001). When conventional and second harmonic duplex were compared, there was a significant (P < .04) difference in the systolic blood flow velocity in the vertebral and basilar arteries. CONCLUSIONS: Second harmonic color duplex imaging in the vertebrobasilar system increases the time of diagnostic useful signal enhancement and produces a better spatial resolution compared with conventional color duplex imaging.

Adult↗
PubMed1997

Two-way selection for daily gain and feed conversion in a composite rabbit population.

We conducted a two-way selection experiment in a composite rabbit population to investigate the responses to selection for postweaning ADG and feed conversion (FC). Two generations of crossing, followed by four generations of random pair matings, preceded three generations of selection. Selection was practiced within four lines: high-feed conversion (HFC), low-feed conversion (LFC), high gain (HG), and low gain (LG). Data on 1,446 rabbits from the random mating and selection generations were fitted to an animal model to estimate heritabilities of and the genetic correlation between ADG and FC. The two-trait model included rabbit and common litter random effects and line, generation, and sex fixed effects. Estimates of heritability of ADG and FC were .48 and .29, respectively, and the genetic correlation between them was -.82. Common litter environmental effects accounted for a proportion of .11 and .13 of the phenotypic variation of the two traits, respectively. For ADG (in g/d) the regressions of mean breeding values on generation number during the selection period were 1.23 +/- .12 (P < .01) in the HG line and -.86 +/- .12 (P < .01) in the LG line; the regressions for FC (in g feed/g gain) were -.07 +/- .01 (P < .01) in the HFC line and .03 +/- .01 (P < .05) in the LFC line. Selection for ADG was effective in improving ADG and FC.

Animals↗
PubMed1996

Pharmacokinetic studies of different echo-contrast agents in the cerebral circulation of dogs.

Ultrasound contrast agents (UCAs) are improving the signal-to-noise ratio of the reflected ultrasound so that Doppler frequency spectra can be recorded even under poor sonographic conditions. This is of particular diagnostic value in transcranial Doppler sonography. Depending on specific pharmacologic properties, echo-contrast agents may cause different increase and duration in Doppler signal amplitude. We used a dog model to study the temporal profile of Doppler signal amplitude after application of a phospholipid-containing echo-contrast agent (BY 963). In addition, we compared it with a contrast agent containing albumin (Albunex). Spherosome suspension BY 963 resulted in a dose-dependent increase in the duration of ultrasound amplification (Doppler enhancement of 1 mL, 3 mL and 10 mL of BY 963 per animal: 62.4 +/- 8.4, 72.8 +/- 9.2 and 67.7 +/- 4.2 s, respectively, n = 6). Detection of BY 963 in the extracranial jugular vein demonstrated that the UCA passes through the cerebral microcirculation (cerebral transit time was 2.2 +/- 0.2 s, n = 4). The signal enhancement lasted longer using the spherosome suspension compared with the albumin-containing solution (77.2 +/- 11.6 and 31.1 +/- 3.7 s, respectively, n = 6), and the maximum increase in intensity was more pronounced (27.0 +/- 2.0 and 17.5 +/- 2.2 dB, respectively, n = 6).

Albumins↗
PubMed1996

Transcranial Doppler detection of microemboli in prosthetic heart valve patients: dependency upon valve type.

Transcranial Doppler ultrasound has revealed the existence of cerebrovascular microemboli in asymptomatic patients with prosthetic heart valves. We investigated the relation between the presence and number of emboli signals and valve type. Patients with six types of prosthetic valves (Björk-Shiley monostrut, Medtronic-Hall, Carbomedics, ATS, Carpentier-Edwards standard, Carpentier-Edwards supraannular) were examined using transcranial Doppler ultrasound in two centers. The monitoring time was 30 min over the right middle cerebral artery. All patients were stabilized on warfarin at the time of study. Microemboli signals were identified by their characteristic audiovisual signal and on subsequent spectral analysis, based on accepted criteria. A standard neurologic questionnaire was completed by all patients. The prevalence of microemboli signals varied between 49% (Medtronic Hall) and 97% (Björk-Shiley monostrut), while their number varied between 1 [0-3] (Carpentier-Edwards standard) and 187 [136-240] (Björk-Shiley monostrut) per hour (median and 95% CI). Both parameters were significantly higher in patients with Björk-Shiley monostrut valves compared to the other patient groups. There were no significant differences in the prevalence of neurologic complications among the groups examined (overall 16%), or in emboli numbers between symptomatic and asymptomatic patients. The prevalence and quantity of microemboli signals in patients with prosthetic heart valves, as detected by transcranial Doppler, is dependent upon valve type. The clinical significance of these microemboli signals remains to be further evaluated.

Aged↗
PubMed1996

[Circulating cerebral microembolisms. Detection with transcranial Doppler ultrasound].

Ischaemic stroke is predominantly caused by cerebral emboli which may originate from cardiac sources or atherosclerotic lesions of the cerebral arteries. The diagnosis is primarily based on clinical symptoms and may be confirmed by typical patterns in cranial computed tomography. Echocardiography, ultrasonography of the supraaortic vessels, and angiography are additional diagnostic tools and helpful in clarifying the pathogenesis. Circulating cerebral emboli can be detected using transcranial Doppler sonography (TCD). Emboli are characterised by short-term, high-intensity ultrasonic signals with characteristic audible "chirps". Because of their acoustic impedance, gaseous emboli reflect the ultrasonic beam with a higher intensity than do formed particles. The differentiation between true embolic signals and artifacts (probe dislocation, electrocautery) requires an experienced observer. With recent developments in automatic detection systems, monitoring will become more feasible for clinical applications. During cardiovascular surgery, TCD signals implying cerebral emboli have been registered in various studies. The incidence of embolic signals during cardiopulmonary bypass varies with stage (before, after aortic declamping) and type of surgery (coronary, valve replacement) and the perfusion regime (bubble, membrane oxygenator). For carotid surgery, embolic signals are most likely to occur with carotid clamping, during shunt insertion, and after declamping. There are some studies suggesting a relation between intraoperative embolic signal count and post-operative neurologic state, but the prognostic significance of these signals is still under debate. Strictly controlled prospective studies including a large number of patients have to be conducted to answer the question whether embolic signal count indicates an increased stroke risk. The high number of patients after valve replacement showing up to 30 embolic signals per minute without suffering from neurologic symptoms raises the question whether continuous, predominantly gaseous microembolisation may cause cumulative brain damage. At present, the nature of emboli (gaseous vs. solid) cannot be easily identified by TCD in clinical settings. Future technical improvement of ultrasonic devices may solve this problem, since detection of solid rather than gaseous emboli seems more likely to be clinically relevant.

Animals↗
PubMed1996

[The aortic arch as an embolism source for cerebral infarcts].

Atherosclerotic plaques in the aortic arch are a potential source of cerebral emboli in patients with cryptogenic stroke (Amarenco et al., 1994). We report on seven patients with cerebral infarction, who had atherosclerotic plaques in the aortic arch, diagnosed by transesophageal echocardiography (TEE). Cardiovascular risk factors as hypertension, diabetes, hypercholesterolemia or cigarette smoking were found in all cases. Carotid disease was present in four patients, one patient had atrial fibrillation with left atrial spontaneous echo contrast, which might have been an additional potential embolic source. Intraluminal protrusion of the plaques ranged from five to twenty-four millimeters. In conclusion, even in patients with carotid or heart disease, the aortic arch may be an important source of cerebral emboli. In cases with mobile and pedunculated protruding atheromas anticoagulation should be considered.

Aged↗
PubMed1996

Variability in occurrence of embolic signals in long term transcranial Doppler recordings.

Albeit still unproven, it is supposed that the presence and number of asymptomatic circulating cerebral microemboli detected by transcranial Doppler ultrasound (TCD) may be an indicator of stroke risk. Little research has been done to assess the reproducibility of these data and the required time for recording. We examined one middle cerebral artery in 7 subjects with carotid, aortic or cardiac embolic source for 24 h by TCD. Analysis for embolic signals was done off line completely blinded to the diagnosis and the time of the day during the recording. Embolic signals were found in all 7 subjects varying from 0 per h to 13 per h. Embolic signals occurred throughout the day with a nonsignificant tendency towards higher values in the early morning hours. Half an hour recording would not have been suitable to rule out or to confirm the presence of embolic signals as there were too many gaps between embolic signals of more than 1/2 h. One hour is the required minimum. Concerning the number of embolic signals, even a recording of four hours yielded variabilities of 0.25 and 8 embolic signals per hour in the same person. We recommend to perform follow-up studies the same time of the day. In patients with a low number of embolic signals longer recordings or a lower detection threshold with a higher number of detected embolic signals are necessary to compare frequencies of embolic signals.

Aged↗
PubMed1996

Asymptomatic circulating cerebral emboli and cerebral blood flow velocity under aspirin and ticlopidine in patients with cerebrovascular disease.

Aspirin and ticlopidine are two commonly used drugs in the prevention of cerebral embolic ischemic events. No direct comparisons in a cross-over design of the effects of ticlopidine and aspirin on asymptomatic circulating cerebral microemboli are available. We investigated 53 patients with cerebrovascular disease. Twenty-six patients were dosed for 2 weeks, 300 mg aspirin once daily and then for 2 weeks, 250 mg ticlopidine twice daily. In 27 other patients the scheme was reversed. Transcranial Doppler monitoring (both middle cerebral arteries simultaneously for 1 h were performed at the end of the two weeks. The signal was recorded on digitalised audio tapes and analyzed blinded off-line. The number of embolic signals per hour and vessel was 15.7 under aspirin and 11.7 under ticlopidine (difference not significant). The correlation between the number of emboli under the two medications was high. The highest number of embolic signals was found in high grade carotid stenosis. In patients with a low number of embolic signals, reproducibility was low. A minimum of 7 embolic signals in one treatment group is required for further therapeutic drug trials to allow reasonable comparisons. This study may help to plan further therapeutic trials using emboli detection.

Adult↗
PubMed1996

Hemostaseologic and hematologic parameters with aspirin and ticlopidine treatment in patients with cerebrovascular disease: a cross-over study.

No direct comparisons of the effects of ticlopidine and aspirin on platelet aggregability, clotting parameters, and blood count are available in a cross-over study design in humans. We investigated 45 patients with cerebrovascular disease. Twenty-one patients received 300 mg aspirin once daily for 2 weeks and then for 2 more weeks received 250 mg ticlopidine twice daily. In 24 other patients, the scheme was reversed. ADP-induced aggregability was lower during ticlopidine treatment; epinephrine- and collagen-induced aggregabilities were lower with aspirin treatment. Platelet counts were higher during ticlopidine than during aspirin treatment (199.6/ nl with aspirin, 213.0/nl with ticlop dine, p = 0.008), probably reflecting less platelet activation and degradation and a longer platelet survival time induced by ticlopidine treatment.

Adenosine Diphosphate↗
PubMed1996

Transcranial duplex monitoring discloses hemorrhagic complication following rt-PA thrombolysis.

INTRODUCTION: Transcranial color-coded sonography (TCCS) allows imaging of basal cerebral arteries as well as brain parenchyma. It may therefore serve to monitor thrombolysis in acute stroke. CASE DESCRIPTION: rt-PA thrombolysis was performed in a patient, suffering from paradoxical embolism causing MCA occlusion. Hemorrhage immediately after completion of rt-PA infusion as well as delayed MCA recanalization could be monitored by TCCS. CONCLUSION: TCCS is useful to improve monitoring and safety of systemic thrombolytic treatment.

Adult↗
PubMed1996

Periodic leg movements are part of the B-wave rhythm and the cyclic alternating pattern.

Periodic leg movements (PLM) in sleep are supposed to constitute a frequent cause of insomnia. There is some controversy whether PLM are the cause of insomnia by provoking microarousals or whether they are simply and epiphenomenon not casually related to the insomnia. We examined four patients with PLM by overnight polysomnography and concomitant transcranial Doppler sonography (TCD) monitoring, 13 patients with suspected normal pressure hydrocephalus by concomitant overnight polysomnography and intracranial pressure recording, and 10 healthy volunteers by concomitant overnight polysomnography and TCD monitoring. EEG arousals occurred more frequently before than after the PLM. PLM were associated with increase in heart rate, breathing amplitude, and cerebral blood flow velocity assessed by TCD. PLM occurred with a mean wavelength of 40.5 s. This mean wavelength corresponded to similar values calculated for intracranial pressure B-waves (43.3 s) in 13 patients with suspected normal-pressure hydrocephalus, TCD B-wave equivalents (42.2 s) in 10 healthy young adults and the frequency of the cyclic alternating pattern in EEg recordings (40 s). Our date suggest that these cyclic variations with a wavelength of about 40 s are part of a common endogenous rhythm. PLM seem to be an epiphenomenon of this rhythm and not the cause of insomnia.

Adult↗
PubMed1996

Dislocation of the third ventricle due to space-occupying stroke evaluated by transcranial duplex sonography.

Transcranial color-coded duplex sonography is a recently introduced method for visualizing (1) the blood flow velocity of the basal cerebral arteries and (2) the brain parenchyma as an acoustic impedance image. Dislocation of the third ventricle due to space-occupying stroke is an important clinical marker. This study evaluated the dislocation of the third ventricle from the brain midline by transcranial duplex sonography in 10 healthy volunteers. The mean dislocation was 0.2 +/- 0.3 mm. Eighteen stroke patients were investigated within 12 hours by both duplex sonography and computed tomography (CT) and the dislocation of the third ventricle was measured. Correlation between the two methods was high (r = 0.87, N = 27). Twelve stroke patients divided into three subgroups according to the extent of the space-occupying effects of the lesion were followed for 3 weeks. The increase and decrease of the dislocation of the third ventricle over the time were monitored. In conclusion, transcranial duplex sonography is a reliable tool to monitor dislocation of the third ventricle due to space-occupying stroke.

Adult↗