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Biomedical subjects

V P van der Hulst

Publications and source records attributed to V P van der Hulst.

9 recordsLinked to original sources
PubMed2001

[Endovascular treatment of 2 patients with an aneurysm of the descending thoracic aorta].

Two men, aged 71 and 70, who had previously experienced an abdominal aneurysm were found to have thoracic aortal aneurysms of respectively 8 cm and 7.5 cm in length. For the first patient an endovascular operation was carried out due to a high operative risk: with the help of a radiograph, four endoprostheses were inserted into the thoracic descending aorta via the femoral artery, after which the aorta diameter became more normal. A month later, the patient died from persistent renal failure, which had developed as a result of the previously ruptured abdominal aneurysm. In the second patient with an aneurysm of the proximal descending aorta, a left decompensation arose following aortal clamping during open surgical repair. Ten weeks later an endoprosthesis was inserted via the femoral artery. A year later the aortal diameter had decreased to 6.5 cm; the patient functioned well. The insertion of an endoprosthesis in the thoracic aorta is a minimally invasive procedure in which the patient experiences little perioperative inconvenience.

Aged↗
PubMed1997

Hemodynamic significance of renal artery stenosis: digital subtraction angiography versus systolically gated three-dimensional phase-contrast MR angiography.

PURPOSE: To compare digital subtraction angiography with three-dimensional phase-contrast magnetic resonance (MR) angiography in detection of significant renal artery stenosis. MATERIALS AND METHODS: Sixteen patients underwent digital subtraction angiography and systolically gated three-dimensional phase-contrast MR angiography within 1 week. Scoring of stenosis on MR angiograms was based on presence and length of a flow void and quality of flow signal intensity in the distal part of the artery. Intraarterial pressure measurement was the reference standard for hemodynamically significant renal artery stenosis. RESULTS: MR angiography depicted two of five patent accessory arteries. Comparison of digital subtraction angiography and MR angiography with intraarterial pressure measurements was possible in 25 main renal arteries. In 13 arteries, a pressure gradient of more than 15 mm Hg was found. Digital subtraction angiography depicted 10 of these stenoses (sensitivity, 77%; specificity, 92%). A flow void was present at MR angiography in eight stenoses (sensitivity, 62%; specificity, 83%). In 12 of the stenosed vessels, distal flow signal intensity was impaired at MR angiography (sensitivity, 92%; specificity, 75%). There was no difference between the two modalities (P > .05) in grading hemodynamic significance of renal artery stenosis. CONCLUSION: Systolically gated MR angiography and digital subtraction angiography are equally effective in depicting hemodynamically significant stenoses in the main renal arteries. MR angiography, however, is not adequate in depiction of accessory renal arteries.

Adult↗
PubMed1996

Renal artery stenosis: endovascular flow wire study for validation of Doppler US.

PURPOSE: To compare the accuracy of proximal and peripheral Doppler parameters for detection of renal artery stenosis (RAS). MATERIALS AND METHODS: The authors obtained absolute velocities and peripheral Doppler waveforms in 16 stenotic and 14 normal renal arteries by using a 0.45-mm endovascular flow wire. Hemodynamically significant stenosis was established by measuring transstenotic invasive pressure gradients, with a 10 mm Hg or greater pressure drop indicating RAS. Accuracy of the Doppler parameters and of digital subtraction angiographic (DSA) results were compared by using receiver operating characteristic analysis. RESULTS: Measurements of absolute velocities at the site of the stenosis (maximal peak systolic velocity [PSVmax], PSV ratio, renal artery-to-aortic PVS ratio) showed high accuracy for diagnosis of RAS similar to that of DSA (areas under the ROC curve were 0.96, 0.97, 0.93, respectively). The distal intrarenal Doppler indexes (notably loss of early systolic peak, acceleration, acceleration time, pulsatility index, and resistive index) did not show statistically significant correlation with RAS. CONCLUSION: Doppler measurements in the main renal artery correlate well with RAS. The intrarenal Doppler spectrum, however, has no diagnostic value. The authors conclude that duplex Doppler US is not a suitable screening test for RAS.

Angiography, Digital Subtraction↗
PubMed1992

Pressure and X-ray recording of reflux into the thoracic stomach.

Anastomotic leakage, pulmonary aspiration and reflux-esophagitis might be induced or aggravated by the increased duodenogastric reflux observed in the thoracic stomach. In this study, the effect of respiration on the reflux-promoting pressure gradient in the intrathoracally located stomach was assessed. In nine patients pressure recording was done in the duodenum and the abdominal and thoracic part of the stomach. Intrapleural pressure was determined by recording mouth pressure during inspiratory occlusion. In addition, the course of injected contrast was examined fluoroscopically. The mean end-expiratory pressure gradient in the thoracic part of the stomach was 0.8 cm H2O, increasing up to 6.0 cm H2O and 21.3 cm H2O during normal and forced inspiration, respectively. Fluoroscopic examination showed reflux of contrast that coincided with the downward movement of the diaphragm. From this study, we conclude that reflux into the thoracic stomach is promoted by intraluminal pressure fluctuations induced by voluntary breathing. Performing a pyloroplasty or -myotomy after intrathoracic esophagogastrostomy destroys the integrity of the pyloric sphincter as a barrier to reflux, thus promoting duodenogastric reflux.

Duodenogastric Reflux↗
PubMed1991

Three-dimensional pressure profilometry of the anal sphincter.

Single channel manometry is of limited value in determining the cause of sphincter dysfunction. This is due mainly to the recording variability caused by radial pressure asymmetry. Multi-channel manometry does not have this disadvantage, but is complicated and difficult to interpret. We report on computerized eight-channel manometry which permits three-dimensional reconstruction of the sphincter. Fifteen subjects were measured. At rest, lower pressures were recorded in the left, left-dorsal, and dorsal directions. Sphincter length was shortest in the right direction and ventral directions. The graphic reconstruction showed marked indentations in the right- and right anterior direction, and one indentation on the opposite side. At maximal squeeze the graphic reconstruction showed the same indentations, but they were more pronounced. In conclusion, computerized eight-channel manometry proved to be an efficient technique which could be routinely applicable. The graphic reconstruction provides insight into radial and axial pressure asymmetry.

Adolescent↗
PubMed1990

The lower esophageal sphincter shown by a computerized representation.

The clinical application of manometry of the lower esophageal sphincter (LES) remains controversial. This is because of the large variability in recorded lower esophageal sphincter pressure (LESP). In this paper a computerized method providing a three-dimensional image of the LES is described. In 12 healthy subjects end-expiratory rapid pull-through LESP recordings were performed for 1 h, using a perfused 8-channel probe. A cylindric model of the sphincter was calculated by means of a graphics program. The graphic representation of the LES demonstrated a circular pressure zone that was affected by the gastric migrating motility complex. This pressure zone was located proximal to a persistent indentation in the posterior and right posterolateral direction. Three-dimensional visualization of the LES provides additional information that cannot be obtained by the usually used techniques of analysis of sphincter manometry.

Adolescent↗
PubMedDate not supplied

Long-term extracorporeal blood bypass in dogs at low flows without systemic heparinization. Heparin-coated versus uncoated circuits.

A blind, randomized study of the effects of a heparin-coated bypass circuit on thromboembolus formation and hematologic and hemostatic parameters was carried out on 12 dogs. The dogs were anesthetized and bypassed for 24 hours using a centrifugal pump circuit with a mean flow of 475 ml/minute. Six of the dogs were bypassed with a heparin coated circuit and six with an uncoated circuit. No systemic heparin was administered to any of the dogs at any time during the procedure. Both the coated and uncoated circuits remained patent at low flows. Thrombus formation, however, primarily around the pump axis, was observed in both groups. Four of the dogs (two from either group) had no evidence of lung emboli. The remaining eight dogs all showed pulmonary emboli. Thromboemboli did not lead to clinical complications or hemodynamic disturbances. Hematologic and hemostatic parameters showed a reduction in hemoglobin, erythrocytes, thrombocytes, leukocytes, and antithrombin III, which was most pronounced in the uncoated group. This study showed that a low flow bypass circuit remains patent for 24 hours whether or not the circuit is coated with heparin. Although the heparin coating limits the reduction in antithrombin III and blood elements, it does not eliminate the risk of thromboembolus formation.

Animals↗
PubMedDate not supplied

Veno-venous bypass without systemic heparinization using a centrifugal pump: a blind comparison of a heparin bonded circuit versus a non heparin bonded circuit.

Veno-venous bypass without the use of systemic heparinization has recently become of increasing interest for application during liver transplantation and surgery on the large abdominal veins. However, possible adverse effects on blood components as demonstrated by means of hematologic and hemostatic parameters or on the occurrence of thromboembolic complications are until now not excluded. No consensus has been reached as to the efficacy of heparin coated circuits in those procedures. In the present study veno-venous bypass was performed for four hours in ten dogs using heparin coated and non coated circuits without further heparinization in a randomized blind fashion. No changes or significant intergroup differences were noted in the hematological and coagulation parameters. Macroscopic evaluation of the circuits revealed small strands of fibrin on all connector rims and clots in the center part of the pump head and at the cannula tips. The lungs showed two small emboli in large size pulmonary arteries and also two minor emboli in small size arteries. In four animals the emboli were equally divided between the two groups. As expected regarding the size of the clots no influences could be seen on hemodynamic or respiratory parameters. With Scanning Electronic Microscopy a monolayer of activated thrombocytes was observed on the surface of the bypass circuits in the coated as well as in the uncoated group. This study suggests that a veno-venous bypass without systemic heparinization is possible without serious damage to blood cellular elements or impressive activation of the coagulation system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗