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Biomedical subjects

F Vermeulen

Publications and source records attributed to F Vermeulen.

At least 19 recordsLinked to original sources
PubMed2003

[Starting experience with non-invasive ventilation in paediatric intensive care unit].

Non-invasive ventilation in pressure support (NIV) is well described in the adult and child over 5 years. However, its use in children less than 1 year of age remains anecdotal. We report our preliminary experience with the use of NIV in six children aged from 5 days to 10 months. NIV was delivered with a flow generator (VPAP IIST, Resmed Ltd, North Ryde, NSW, Australia) in association with specific tubings and a nasal mask. The use of NIV resulted in a significant decrease of both the respiratory rate (from 53 to 39 breaths per min, p < 0.01) and the PvCO(2) (from 9.33 to 6.28 kPa, p < 0.01). These results show that NIV can be used in children under 1 year of age with improvement of physiological parameters.

Carbon Dioxide↗
PubMed2001

The Hemashield Woven prosthesis in the thoracic aorta: a prospective computer tomography follow-up study.

BACKGROUND: Dacron prostheses in humans have been documented to present long-term fiber alterations, that may account for late graft dilatation. Late dilatation has been documented mainly in knitted prostheses, implanted in the abdominal and thoracic aorta. Dilatation of the collagen-impregnated Hemashield Woven prosthesis has not been studied prospectively in the thoracic aorta. METHODS: Twenty patients were prospectively included. The intraoperative performance of the graft and mid-term clinical behaviour were studied. The graft distensibility was evaluated by postoperative, 1 and 3 yr computed tomographic diameter follow-up. RESULTS: There were no hospital deaths. Two graft-unrelated deaths occurred at 3 yr. The graft performance was excellent or good for most aspects. No significant changes in CT diameter occurred throughout the 3 yr follow-up. CONCLUSION: The collagen-impregnated Hemashield Woven prosthesis is considered safe in replacements of the thoracic aorta. Future evaluation should focus on the very long-term behaviour in young adults.

Adult↗
PubMed1999

Effects of low flow on pulmonary vascular flow-pressure curves and pulmonary vascular impedance.

OBJECTIVE: Flow-pressure curves and vascular impedance are commonly used to investigate pulmonary circulation, but they may be affected at low flow by reflex neurohumoral activation. We therefore investigated the mechanical effects and the reflex effects of decreased flow on pulmonary vascular resistance and impedance. METHODS: In ten anaesthetized dogs, we compared flow-pressure curves generated in less than 10 s to prevent sympathetic activation (fast curves), or generated over 20-30 min to allow neurohumoral equilibration (slow curves), in hyperoxia (inspired oxygen, 40%) and in hypoxia (inspired oxygen, 10%), before and after adrenergic blockade by phentolamine and propranolol. Resistance was assessed from the flow-pressure relationship. Impedance was computed from instantaneous flow and pressure obtained with an ultrasonic flowmeter and a micromanometer-tipped catheter. RESULTS: At baseline, fast flow-pressure curves were steeper and had a lower pressure intercept. Transient low flow did not affect heart rate or pulmonary arterial elastance. Sustained low flow increased heart rate, resistance and elastance, suggesting baroreceptor-induced sympathetic stimulation. After adrenergic blockade, no difference persisted between effects of transient and sustained low flow. In hypoxia, slow and fast flow-pressure curves were similar. Hypoxia increased heart rate and resistance but did not decrease elastance, suggesting chemoreceptor-induced sympathetic stimulation. In hypoxia, differences between transient and sustained low flow were no longer significant, and were completely suppressed by adrenergic blockade. In two additional dogs, epinephrine infusion increased pulmonary vascular resistance and elastance. CONCLUSIONS: We conclude that (1) compared to transient low flow, sustained low flow is associated with increases in distal resistance and proximal elastance due to sympathetic stimulation and (2) these differences between the effects of transient and sustained low flow do not persist in hypoxia, because of an already present chemoreceptor-induced sympathetic stimulation.

Adrenergic alpha-Antagonists↗
PubMed1999

Gelseal versus Gelweave dacron prosthetic grafts in the descending thoracic aorta: a two-year computed tomography scan follow-up study.

BACKGROUND: In the abdominal aorta, the use of knitted rather than woven dacron prostheses has shown an early and slow late dilation. The dilation of woven versus knitted dacron prostheses in the thoracic aortic position has not yet been investigated. METHOD: From 1992, 25 patients entered a prospective study: 13 Gelweave and 12 Gelseal prostheses (diameter 18-26 mm) were implanted in the descending thoracic aorta. Computed tomography (CT) scans without contrast-enhancement were performed 2 weeks, and 1 and 2 years postoperatively. The full length of the grafts was scanned and the diameter was measured in mm measured at a level outside the areas of intercostal artery reimplantation. Patient determinants analysed were age, hypertension and implantation diameter of the grafts. The Gelseal group had a mean age of 63.7 years and seven were males. The Gelweave group had a mean age of 67.8 years and seven were males. RESULTS: the mean implantation diameters were 19.6 +/- 1.7 mm and 22.0 +/- 2.7 mm (P = 0.02) for the Gelseal and Gelweave grafts, respectively. On the CT-scans at 2 weeks postoperatively, the diameter had increased by 18.8 +/- 4.8% (P = 0.0001) in the Gelseal and by 5.7 +/- 6.4% (P = 0.007) in the Gelweave grafts. This difference in diameter at 2 weeks between the two prostheses was significant (P < 0.0000 1). At 1 year the diameter had increased by 28.4 +/- 5.2% (P = 0.0001) and by 8.4 +/- 4.6% (P = 0.0003) for the Gelseal and Gelweave grafts, respectively, compared with the implantation diameter. The increase in diameter between the postoperative values at 2 weeks and those at 1 year was statistically significant in the Gelseal grafts (P = 0.0002) but not in the Gelweave grafts (P = 0.56). At 2 years an increase in diameter by 31.4 +/- 5.2% (P = 0.0001) and by 7.4 +/- 7.1% (P = 0.014) for the knitted and woven prosthetic grafts, respectively, was noted compared with the initial implantation diameter. The increase in diameter between the CT measurements at 2 weeks and those at 2 years was statistically significant in the Gelseal group (P = 0.001) but not in the Gelweave group (P = 0.86). The difference in this late increase in diameter between the two implanted grafts was also significant (P < 0.005). Age, hypertension and initial diameter did not appear to be significant determinants. CONCLUSION: In contrast to the Gelseal prosthesis in the descending aorta, the Gelweave prosthesis does not show any late dilation.

Adult↗
PubMed1999

Polyunsaturated fatty acids inhibit Mg2+ -ATPase in basolateral membranes from rat enterocytes.

It is known that certain polyunsaturated fatty acids of the n-6 family, for example linoleic and arachidonic acids, can activate both Na+, K+-ATPase and Ca2+-ATPase. These enzymes drive active absorption processes in the duodenal enterocyte. This study presents data which show a 30-50% inhibition of Mg2+-ATPase activity in enterocyte basolateral membrane preparations by linoleic and gamma-linolenic acids (also a member of the n-6 family.) Mg2+-ATPase activity has several possible roles in the enterocyte: involvement in Mg2+ and Ca2+ absorption (as part of Ca2+-ATPase and also myosin I activity) as well as control of phospholipid distribution in the membrane by a class of Mg2+-ATPases called 'flippases'. The action of linoleic and gamma-linolenic acids on basolateral membrane Mg2+-ATPase may thus modulate several cellular transport processes.

Animals↗
PubMed1998

Pulmonary vascular resistance in dogs and minipigs--effects of hypoxia and inhaled nitric oxide.

The pig has been reported to present with a stronger hypoxic pulmonary vasoconstriction than many other species, including the dog, but it is not known whether this is associated with a different longitudinal partitioning of pulmonary vascular resistance (PVR). We investigated the relationships between cardiac output (Q) and mean pulmonary artery pressure (Ppa) minus occluded Ppa (Ppao), and effective pulmonary capillary pressure (Pc') minus Ppao, in seven minipigs and in seven dogs in hyperoxia (FI(O2) 0.4) and hypoxia (FI(O2) 0.1), first without, then with the inhalation of 80 ppm nitric oxide (NO) to inhibit any reversible component of PVR. Pc' was estimated from the Ppa decay curve following pulmonary artery balloon occlusion. In hyperoxia, minipigs compared to dogs had (Ppa - Ppao)/Q and (Pc' - Ppao)/Q plots shifted to higher pressures. Hypoxia at each level of Q increased Ppa - Ppao in minipigs more than in dogs, and Pc' - Ppao in minipigs only. Inhaled NO reversed hypoxia-induced changes in (Ppa - Ppao)/(Q and (Pc' - Ppao)/Q plots. We conclude that the minipig, compared to the dog, presents with higher PVR and reactivity including vessels downstream to the site of Pc' as determined by the arterial occlusion technique.

Administration, Inhalation↗
PubMed1998

Predictors of hospital mortality in type A aortic dissections: a retrospective analysis of 148 consecutive surgical patients.

Reports in the literature frequently concern miscellaneous types of dissections. This makes correct interpretation of data difficult. In order to assess the determinants of hospital mortality, the results of 148 consecutive patients over a 23-year period, all operated on for a type A dissection, were reviewed. Mean(s.d.) age was 56(13.1) years, 64% were male. An acute dissection (surgery within 14 days after onset of symptoms) was performed in 139 patients. Stigmata of the Marfan syndrome were present in 6.1% (n = 9). Peripheral vascular ischaemic complications were observed in 27.7%. Nowadays, diagnosis is primarily confirmed using transoesophageal echocardiography (75 correct diagnoses among 76 performed). Operation consisted of repair or replacement of the ascending aorta. Resuspension of the aortic valve was performed in 74 patients, and arch replacement in 25. In 74 patients, distal repair was done under deep hypothermic circulatory arrest. Hospital mortality rate was 23.6% (35 patients), though mortality rate calculated over the period 1990-1993 was 17.4% (P = n.s.). Univariate analysis revealed the following variables to be statistically significant predictors of hospital mortality (P < 0.05): preoperative ischaemic complications, preoperative resuscitation, haemopericardium, postoperative neurological complications, rethoracotomy, renal insufficiency and intestinal ischaemia. Multivariate stepwise logistic regression indicated preoperative resuscitation, postoperative haemodialysis and postoperative neurological complications as the only independent predictors of hospital death. Dissections arising from a primary intimal tear in the descending aorta had a more favourable outcome (P = 0.06, odds ratio 0.1). Although hospital mortality has declined over the past few years, no decline was seen in operative mortality since gelatine-resourcine-formol (GRF) glue is used as a routine. Transoesophageal echocardiography is the first choice in confirming diagnosis. Early operation is advocated, with careful haemostasis, before the development of cardiac tamponade or end-organ ischaemia, as the cornerstone of a successful treatment of a type A dissection. Reduction of neurological complications will further improve the results.

Aortic Dissection↗
PubMed1998

[The focus in neonatology].

During the last years, neonatology has greatly improved. In the last decade, mortality and morbidity have decreased: mortality from respiratory failure of prematurity has decreased from 22% to 12%, mortality of the very low birthweight infants under 1000 g fell from 56% to 35% and mortalities related to asphyxia have diminished from 21% to 12% and to malformations from 33% to 28%. Prematurity is now the first cause of neonatal mortality. During this period, the number of babies under 1000 g has increased 4-fold and the number of multiple births increased more than 2-fold from 3% to 7% of the live births of our hospital. Attitudes towards the premature infant have changed, especially towards the extremely small (called the micropremies). The number of disabled children has increased in parallel with the better survival of the very immature newborns who till recently were not resuscitated.

Asphyxia Neonatorum↗
PubMed1998

Influence of the use of a bypass on the results of thoracoabdominal aortic aneurysm surgery.

OBJECTIVES: To evaluate the influence of the use of a bypass on the results of thoracoabdominal aortic aneurysm surgery. METHODS: The results of the repair of 224 thoracoabdominal aortic aneurysms operated upon between 1981 and the end of 1996 were evaluated retrospectively. In 122 cases we used simple cross-clamping (clamp and sew technique) and in 102 cases a left heart bypass (atrio-femoral or aorto-femoral) was the preferred method. Except for the use of cerebrospinal fluid drainage over the last years, the methods of spinal protection were the same in both groups. Renal protection was also identical in both groups. All aneurysms were repaired using the inlay technique. RESULTS: Hospital mortality was 11.2%: 14.7% in cross-clamp group versus 6.8% in the bypass group (p = 0.04). Postoperative dialysis was necessary in 9.8%: 12.7% in the cross-clamp group versus 6.8% in the bypass group (p = 0.108). Paraplegia occurred in 8.4%: 7.4% in the cross-clamp group versus 9.8% in the bypass group (p = 0.517). Using the highly predictive model of Acher, there would have been 33% spinal cord lesions in the bypass group. CONCLUSIONS: Hospital mortality, postoperative dialysis and postoperative spinal cord problems are lowered by the use of a bypass during the repair of thoracoabdominal aortic aneurysms. These results evidence that the use of a bypass is indicated in this complex operation.

Aged↗
PubMed1997

Reoperative aortic root surgery late after use of histo-acryl.

Cardiovascular reoperations after the use of histo-acryl are extremely rare. A patient is described, who underwent an aortic root replacement according to Bentall's technique, for a postdissectional aneurysm. At that time, to achieve hemostasis, histo-acryl adhesive was applied and a Cabrol's fistula was created. Fourteen years later, a recurrent 'false', aneurysm had developed and the fistula had a hemodynamically significant left-right shunt. At reoperation, the composite graft was replaced by a cryopreserved aortic root allograft with long coronary arteries. To our knowledge, this is the first report of a cardiovascular reoperation after previous use of histo-acryl. This patient also merits attention as to the fact that it illustrates a failure of a modified Cabrol's procedure.

Adult↗
PubMed1997

Site of pulmonary vasodilation by inhaled nitric oxide in microembolic lung injury.

We investigated the site of pulmonary vasodilation and associated effects on gas exchange in response to inhaled NO in acute microembolic lung injury. Pulmonary arterial (Ppa) and effective capillary (Pc') pressures versus cardiac output (Q) plots were generated in anesthetized dogs before and after, successively, (1) embolization with 100 microns glass beads, (2) administration of either a placebo (n = 5) or 80 ppm inhaled NO followed by cyclooxygenase inhibition by aspirin 1 g given intravenously and again 80 ppm inhaled NO (n = 8). Pc' was estimated from the pressure decay curve after pulmonary artery balloon occlusion. Embolism increased pulmonary vascular resistance, with a slight decrease in its precapillary component, from 77 to 66%. NO decreased Ppa at the highest levels of Q, and aspirin increased Ppa at all levels of Q. Neither NO nor aspirin affected Pc'/Q plots or pulmonary shunt. We conclude that pulmonary vascular resistance in microembolic lung injury increases at the periphery of the pulmonary arterial tree, with partial reversibility by inhaled NO and by endogenous products of the cyclooxygenase pathway upstream from the site of effective capillary resistance. Reduced pulmonary vascular tone does not improve gas exchange in this model of acute lung injury.

Animals↗
PubMed1996

'In vivo' size of knitted Dacron prostheses (Gelseal) used in the thoracic aorta: a computed tomography study.

When replacing the thoracic aorta, gelatin-sealed triaxial knitted Dacron prostheses are used as they have zero porosity and are easy to handle. It is known that knitted prostheses (not triaxially constructed), when implanted in the abdominal aorta or in the peripheral vessels, show a dilatation of 10-20%. The initial in vivo expansion of this prosthesis in the thoracic aorta was assessed using computed tomography scanning in 18 patients. The graft sizes used were 18mm (n = 4). 20mm (n = 5). 22mm (n = 4), 26mm (n = 1), 28mm (n = 2) and 30mm (n = 2). All patients were kept normotensive postoperatively. Computed tomography scan measurement was performed within 4 weeks of operation. using standard computed tomography equipment and no contrast. Two radiologists checked and agreed upon the slice levels and measurements compared with the manufacturer's stated size referring to internal diameter of the crimped prosthesis. The mean(s.d.) 'in vivo' size was 16.2(6)% larger. This 'true size' should be taken as the reference measurement when considering further dilatation over the period of follow-up.

Adult↗
PubMed1996

Hypoxic pulmonary vasoconstriction and gas exchange in acute canine pulmonary embolism.

Hypoxic pulmonary vasoconstriction (HPV) is inhibited in several models of acute lung injury. Whether HPV is preserved in pulmonary embolism is unknown. We investigated the effects of a reduction in the fraction of inspired O2 (FIO2) on pulmonary hemodynamics and gas exchange in anesthetized dogs before and after autologous blood clot pulmonary embolism. In a first group of 14 dogs, stimulus-response curves for HPV were constructed as pulmonary arterial pressure (Ppa) vs. FIO2 varied between 1.0 and 0.06 at a cardiac output (Q) kept constant at 3.5 l.min-1.m-2. Gas exchange was evaluated by using the multiple inert-gas elimination technique at FIO2 of 1.0, 0.4, and 0.1. Embolism decreased the relative magnitude of HPV, expressed as the gradient between Ppa and pulmonary arterial occluded pressure in hypoxia divided by (Ppa-pulmonary arterial occluded pressure) at FIO2 of 1.0, from 1.8 to 1.2 (P < 0.05). Retention minus excretion gradients for sulfur hexafluoride and ethane were increased by decreased FIO2 (P < 0.005 and P < 0.05, respectively) before but not after embolism. Hypoxia-induced deterioration in gas exchange before embolism was related to the amount of baseline very low ventilation-perfusion (VA/Q) ratios. Similar results were obtained in a second group of seven dogs with Q decreased to maintain Ppa at the same average value as before embolism. However, gas exchange was not affected by inspiratory hypoxia before as well as after embolism in this group, which presented with a lesser amount of baseline very low VA/Q. In both groups of dogs, increase in the FIO2 from 0.4 to 1.0 did not affect gas exchange. We conclude that 1) pulmonary embolism is associated with a partial inhibition of HPV, 2) HPV does not contribute to preserve gas exchange in pulmonary embolism, and 3) a strong HPV may deteriorate gas exchange in severe hypoxia in the presence of minor very low VA/Q inequality.

Animals↗
PubMed1992

The Intact porcine bioprosthesis: early world-wide clinical experience and analysis of a single institution's experience.

The Intact porcine bioprosthesis is a new-generation valve fixed under stress-free conditions and subjected to a mineralization-inhibiting treatment. The valve is undergoing multi-centre prospective clinical evaluation sponsored by Medtronic, Inc., with 19 centres participating world wide. Since April 1986, 1465 valves have been implanted in the aortic position (AVR, n = 965), mitral position (MVR, n = 438), or both (n = 62), and followed up to 5 years. The data recorded at our participating centre, with 115 valves implanted (AVR n = 93, MVR n = 22) closely match the overall event and death rates in the prospective study. Early mortality in the overall study is 5.6% in AVR and 6.6% in MVR; 3-year actuarial survival rates are 88.5% in AVR and 85.6% in MVR; structural valve-failure-free rates at 3 years are 99.8% in AVR and 98.5% in MVR; 3-year freedom from valve-related reoperation is 97.3% in AVR and 95.8% in MVR. The preferential use of bioprosthetic valves in patients aged 70 years and older with no other indication for anticoagulant treatment entails the not infrequent occurrence of patient/prosthesis mismatch in AVR. Hence, when implanting bioprostheses in old patients, the acceptance of some mismatch has to be weighed against the freedom from anticoagulation treatment and the expected long-term freedom from structural valve failure. Further long-term follow-up will be required to demonstrate the greater durability expected from the stress-free fixation and the anti-mineralization treatment.

Actuarial Analysis↗
PubMed1991

Measured attenuation correction using the Maximum Likelihood algorithm.

Quantitative determination of local radioactivity concentration in positron emission tomography (PET) requires a good attenuation correction procedure to reconstruct the emission image. Using a similar Maximum Likelihood (ML) algorithm as for the reconstruction of the emission image, a method is proposed to reconstruct a transmission image, i.e. a map of absorption coefficients. This reconstructed transmission image is then used to calculate the attenuation correction factors needed for the ML reconstruction of the emission image. This approach takes automatically into account the convolution step in the acquisition process (caused by various smoothing factors, e.g. the detector width). This results in appreciable noise suppression without loss of resolution due to filtering, thus making the reconstructed images easier to interpret. A comparison is made with other estimates for the measured attenuation correction using phantom studies.

Algorithms↗
PubMed1990

Intraoperative transesophageal color-coded Doppler echocardiography for evaluation of residual regurgitation after mitral valve repair.

Because mitral valve competence after mitral valve reconstruction is awkward to assess during this procedure, we evaluated in this respect transesophageal color-coded Doppler echocardiography in 23 patients undergoing mitral valve reconstruction for severe mitral regurgitation. Transesophageal echocardiographic examinations were performed after induction of anesthesia but before sternotomy (baseline), after mitral valve repair before decannulation, and at sternal closure, all at similar mean aortic pressure and echocardiographic instrument settings. The degree of mitral regurgitation by transesophageal color Doppler flow mapping was visually quantified on a 5-point scale (0 to 4), pending the left atrial extent of the regurgitant jet. This was compared with the degree of mitral regurgitation by left ventricular cineangiography performed within several weeks after operation and also visually quantified on a 5-point scale (0 to 4), with use of the right anterior oblique projection. There was good correlation between the two methods (r = 0.83; p less than 0.001). We conclude that residual mitral regurgitation, as assessed by transesophageal color flow mapping in the operating room, highly correlates with the ultimate mitral regurgitation by cineangiography. Therefore transesophageal echocardiography can be helpful for evaluation of mitral valve competence during mitral valve reconstruction, and hence, in case of repair failure, allow valve replacement in the same surgical session, thus avoiding reoperation.

Adolescent↗
PubMed1989

Surgical correction of descending thoracic aortic aneurysms with shunt or bypass techniques versus simple aortic cross-clamping.

Between June, 1972, and January, 1986, 57 patients underwent resection of a descending thoracic aortic aneurysm using a shunt or bypass for distal aortic perfusion (group I, n = 29) or simple aortic cross-clamping, routinely used since mid-1983 (group II, n = 28). There was a statistically significant difference in the mean age of the patients: in group II it was 14 years higher than in group I (group I: 52.8 years, group II: 66.5 years). Of these 57 patients, 8 died in hospital (group I: 6 patients, group II: 2 patients). Hospital mortality was strongly related to preoperative rupture and the incidence of intraoperative complications. Postoperative paraplegia occurred in 3 patients, all in group I, and could be related to ligation of four or more intercostal arteries between T8 and T12. Postoperative renal failure, necessitating dialysis in 5 patients, was strongly related to intraoperative hypotension, and also to emergency procedures and pre-existing renal dysfunction. Intraoperative haemorrhage occurred more often using shunting or bypass techniques. Mortality, paraplegia and renal failure showed a decreasing trend after abandoning the use of adjunctive perfusion.

Acute Kidney Injury↗