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E Wahlberg

Publications and source records attributed to E Wahlberg.

36 records · Page 2Linked to original sources
PubMed1997

Gene therapy and vascular disease: potential applications in vascular surgery.

Advances in molecular biology have generated methods that are used to enhance diagnosis and treatment of a variety of human diseases. More recently modification of gene expression in cells by gene transfer has been introduced as a new therapeutic modality. The targeting of vascular cells with this method is appealing not only for anatomical reasons, but also because endovascular techniques provide access to the vasculature and makes site-specific delivery possible. Over the past few years, gene transfer has been widely used to explore the pathophysiology of vascular diseases in experimental models and available data suggests that this method may eventually become a therapeutic alternative for vascular disorders such as restenosis, graft failure, and critical ischaemia. In the following we discuss the methodology of gene transfer, its tentative use in vascular diseases related to vascular surgery, and the problems associated with this new technology.

Animals↗
PubMed1996

Postocclusive reactive hyperemia estimating peripheral vascular resistance: a noninvasive method to predict outcome of infrainguinal vascular reconstructions?

OBJECTIVE: The peripheral vascular resistance is an important factor determining the outcome of infrainguinal revascularizations. When measured intraoperatively, it correlates to graft patency, but to select patients to surgery a preoperative, preferably noninvasive, method is necessary. The aim of the present study is to test if parameters recorded during postocclusive reactive hyperemia can be used for that purpose. EXPERIMENTAL DESIGN: This prospective study compares patients with occluded grafts within 30 days postoperatively to patients with patent grafts. SETTING: University Hospital. PATIENTS: Thirty patients with critical ischemia scheduled for infrainguinal bypass surgery. MEASURES: Correlations between intraoperatively measured peripheral resistance and preoperatively recorded parameters of postocclusive reactive hyperemia. The ability of the values to predict outcome. RESULTS: Peripheral resistance correlated significantly to two parameters during postocclusive reactive hyperemia recorded after thigh occlusion, flux reappearance time (r=0.47, p=0.01) and time to peak flux (r=0.41, p=0.03). Intraoperative peripheral resistance predicted graft occlusion at 30 days with a 90% accuracy, while parameters obtained during reactive hyperemia, only tended to predict adverse outcome. CONCLUSIONS: Several parameters during reactive hyperemia show weak correlation to intraoperatively measured peripheral resistance, but none was able to accurately predict graft failure. Further studies are needed to evaluate its capability for patient selection.

Aged↗
PubMed1995

Changes in postocclusive reactive hyperaemic values as measured with laser Doppler fluxmetry after infrainguinal arterial reconstructions.

OBJECTIVES: The aim of the present study was to evaluate microcirculartory changes of the postocclusive reactive hyperaemia test measured with Laser Doppler fluxmetry to detect results of arterial reconstructions. DESIGN: Prospective open study. SETTING: Vascular laboratory of a University Hospital. MATERIAL: Sixty patients with peripheral arterial occlusive disease who underwent infrainguinal reconstruction were examined the day before and 1-2 days after surgery. CHIEF OUTCOME MEASURES: The values were obtained during postocclusive reactive hyperaemia induced by release of a 3 min arterial occlusion with a cuff at ankle level with the laser Doppler probe placed dorsally on the first toe. The alterations after surgery in these hyperaemia parameters were compared to changes in ankle/brachial index and clinical improvement at 30 days postoperatively. MAIN RESULTS: Patients improved by surgery according to ankle/brachial index had significantly reduced time to peak (p < 0.001) and significantly increased resting flux value (p < 0.05) and peak flux value (p < 0.05). There was a significant correlation between the change after surgery in time to peak flux and increment of ankle/brachial index (r = 0.63, p < 0.001). CONCLUSIONS: Changes in reactive hyperaemia values as measured with laser Doppler fluxmetry, especially the time to peak flux, seem to detect circulatory changes caused by arterial reconstructions.

Aged↗
PubMed1995

PAS-Port: a new implantable vascular access device for arm placement: experiences from the first two years.

OBJECTIVE: To evaluate the performance of a new subcutaneous infusion port for placement in the arm. DESIGN: Retrospective study. SETTING: Karolinska Hospital, Stockholm, Sweden. SUBJECTS: 85 of 90 consecutive patients referred for implantation of a subcutaneous infusion port. Five records were missing. Implantation was successful in 81 cases (95%). INTERVENTIONS: Implantation of a PAS-Port (Kabi Pharmacia Deltec) subcutaneously on the forearm. Vascular access was obtained by cut-down. MAIN OUTCOME MEASURES: Success rate, complications and reliability in routine use. RESULTS: After a follow-up time of 1-24 months (median 5), 42 ports were still in use, 21 patients had died with functioning ports, two ports had been removed at the end of treatment, 11 had been removed because of complications and because they malfunctioned; and 3 patients were lost to follow-up. The overall infection rate was 0.08/100 catheter days. CONCLUSIONS: PAS-Port is a safe alternative to chest-placed port systems where there is a need for long term vascular access in adult patients.

Adolescent↗
PubMed1994

Infusion methods for determination of peripheral resistance: influence of infused medium and back pressure.

It has been suggested that peripheral vascular resistance (PR), measured intraoperatively, can predict the outcome of infrainguinal reconstructions. There is, however, a great deal of variability in design and predictive value with this method, and it is prone to technical difficulties and possible errors. The present study evaluated the influence of the choice of infusion medium and the back pressure on PR as measured by the infusion technique. In a porcine model of experimentally induced stenosis, standard PR (calculated by the pressure difference across the stenosis and the Doppler volume flow) was compared with PR based on infusions of blood or saline solution. With blood as the infusion medium there was a significant correlation between the PR and the standard values (r = 0.795, p = 0.0005), whereas there was no correlation when saline solution was infused (r = 0.067, p = 0.345). Subtracting the back pressure resulted in a slight improvement in the correlations between standard PR and PR measured after infusion of blood but not saline solution. In summary, blood should be used as an infusion medium in methods of PR determination, but the influence of back pressure remains uncertain.

Animals↗
PubMed1994

Correlation between peripheral vascular resistance and time to peak flow during reactive hyperaemia.

Earlier studies have proposed that the time to reach peak hyperaemic flux recorded with laser Doppler (tp) is a simple and accurate method of evaluating ischaemic limbs and possibly a method of estimating the peripheral vascular resistance (PR). The aim of this study was to investigate the relationship between the tp and changes in limb vascular resistance caused by arterial stenosis. Forty postocclusive hyperaemia tests with arterial stenoses of different pressure gradients were performed in four pigs. A laser Doppler fluxmeter was used to record postocclusive hyperaemia in the skin of one hind limb. A specially designed tourniquet was used for the arterial occlusion. Proximal and distal to the occlusion level a snare was used to form different grades of stenosis. The PR (mmHg.ml-1.min-1) was either estimated by infusion of a known blood volume into the tested limb over a given time period with simultaneous measurement of pressure or calculated on the basis of measurements of limb blood flow and blood pressure gradients. The tp was closely related to total limb vascular resistance assessed by the blood infusion method (r = 0.83, p < 0.0003) and to the resistance calculated from volume blood flow and intraarterial pressures (r = 0.86, p < 0.0001). This study suggests that the tp accurately reflects limb vascular resistance in an experimental model. Thus tp may be used as a quantitative indicator of overall blood flow impairment, and should be evaluated in patients with lower-limb atherosclerosis.

Animals↗
PubMed1994

Limb loss in association with vascular surgery--a five-year series of major lower-limb amputation.

OBJECTIVE: To evaluate the type, timing and number of vascular reconstructions that preceded amputation; to compare the characteristics of amputees who had had reconstructions with those of amputees who had not, and to compare the results of amputation. DESIGN: Retrospective study of case notes. SETTING: University hospital, Sweden. SUBJECTS: All 219 patients who underwent amputation between 1987 and 1992. MAIN OUTCOME MEASURES: Incidence of amputations; presenting features, and type and results of vascular reconstructions. RESULTS: The number of amputations decreased after 1988, and that of vascular reconstructions increased. 56 of the 99 who had amputations after reconstruction (57%) had had their last procedure within a month. This group had had a mean of three operations, had worse run-off as assessed by angiography, and 2 of them (5%) had amputations after failed suprainguinal reconstruction for claudication alone. 68 of the total (31%) had amputations without first being assessed by a vascular surgeon. 52 (24%) required reamputation. CONCLUSION: Better objective methods are needed for the assessment of patients before primary as well as secondary vascular reconstructions. All patients should be seen by a vascular surgeon before amputation is recommended.

Adult↗
PubMed1993

Level of arterial obstruction in patients with peripheral arterial occlusive disease (PAOD) determined by laser Doppler fluxmetry.

AIM: To evaluate the laser Doppler fluxmeter as a non-invasive screening method to determine the level of peripheral arterial occlusive disease (PAOD) in the lower limb. DESIGN: Open study of the veno-arterial reflex (VAR) during a shift in body position using a laser Doppler fluxmeter at five probe positions distal to the knee, compared with the occlusion level determined by arteriography and segmental plethysmography. MATERIALS: 50 legs comprising 10 normal controls, 20 legs with suprainguinal obstructions (10 claudication and 10 critical ischaemia) and 20 legs with infrainguinal obstructions (10 claudication and 10 critical ischaemia). RESULTS: Controls had normal VAR (mean flux reductions of 38% during dependency) at all probe positions. Legs with infrainguinal disease had normal reflexes proximally but significantly disturbed reflexes distally, whereas suprainguinal disease showed alterations at all sites. Claudicants had diminished flux reduction (mean 12%) whilst those with critical ischaemia increased the flux (mean 32%). CONCLUSION: This simple, non-invasive technique may be of use in determining the level of obstruction in PAOD.

Aged↗
PubMed1992

Effects of local hyperemia and edema on the biological zero in laser Doppler fluxmetry (LD).

The method of laser Doppler (LD) fluxmetry records the flux of moving blood cells and particles in a small tissue volume. However, also during complete arterial occlusion a flux-independent signal can be recorded, which is sometimes significantly different from the electrical zero of the instrument. This part of the signal has been called the biological zero (BZ), and can sometimes represent up to 80% of the total LD signal. In the present study, we investigated the influence of induced hyperemia produced by methylnicotinate and histamine respectively, both vasodilators but only histamine giving edema. Eleven legs of nine healthy subjects were studied. Test sites on the dorsal skin of the foot were prepared with a) histamine (10 mg/ml), b) methylnicotinate (0.1 mol/l) and c) saline. The substances were administered onto the skin with a lancet as the prick test procedure. The basal LD was measured before, and the BZ during an arterial occlusion obtained with a cuff at the ankle. Histamine induced a wheal and edema in all subjects, while methylnicotinate only caused erythema. Basal LD was significantly (p less than 0.01) increased by both substances compared to saline. The BZ was significantly higher (p less than 0.01) with histamine than with both saline and methylnicotinate. The results show that BZ is increased by vasodilation, and still more so by edema formation. It is concluded that the BZ value must always be recorded and taken into consideration when LD blood cell flux is measured in the skin.

Adult↗
PubMed1990

The influence of reactive hyperemia and leg dependency on skin microcirculation in patients with peripheral arterial occlusive disease (PAOD), with and without diabetes.

The increase in venous pressure during leg dependency causes a vasoconstriction of the distal vascular bed in healthy subjects, which is due to the so-called veno-arteriolar reflex. The aim of the present study was to investigate if this reflex is disturbed in patients with severe peripheral arterial occlusive disease (PAOD), with and without diabetes. The total skin microcirculation during rest and postocclusive reactive hyperemia (PRH) after a three minute arterial occlusion at the ankle was studied by laser Doppler (LD) fluxmetry. The LD probe was attached to the dorsal region of the foot in 10 legs of healthy control subjects, patients with PAOD, and patients with PAOD and diabetes respectively. No vasoconstriction was seen in the PAOD group when the leg was moved from the supine to the dependent position. The PRH response was also significantly (p less than 0.05-0.01) impaired compared to the controls in both positions. The diabetic PAOD patients had an almost normal reactivity in spite of an equally reduced arterial circulation as the non-diabetic patients. The results show that patients with PAOD have a significantly disturbed reactivity of the skin microcirculation in the ischemic foot, while the reactivity in diabetic PAOD patients is almost normal.

Aged↗
PubMedDate not supplied

A rat model for severe limb ischemia at rest.

We sought an animal model able to discriminate metabolic and angiogenic processes in limb ischemia. For that we modified and evaluated a rat model of severe unilateral limb ischemia at rest. A two-stage surgical procedure entailing left femoral artery ligation preceded by interruption of collateral vessels originating from the infra-renal aorta and left iliac arteries was performed in Sprague-Dawley rats. The model was evaluated for up to 8 weeks with a transit-time flow meter, a laser Doppler perfusion imager, microspheres, arteriography and histology. It was found to be well tolerated with low mortality and perfusion in the foot skin was reduced up to 8 weeks, while collaterals were visible after 2 weeks. Histologic signs of ischemia were seen for up to 4 weeks. This rat model of severe limb ischemia at rest lasts up to 8 weeks and seems well suited for longitudinal studies of the pathophysiology of limb ischemia and healing mechanisms like angio- and arteriogenesis.

Angiography↗
PubMedDate not supplied

Spatial and temporal variation in laser Doppler flux values in healthy lower limbs: comparison between the standard and the multiprobe.

Skin flow recordings with a laser Doppler instrument have not proven useful for evaluation of patients with peripheral arterial occlusive disease. The introduction of a probe using seven fibers suggested a reduction in spatial variation, but few studies using this multiprobe have been published. The present study was designed to compare the multiprobe to the standard probe placed between the knee and the first toe, chosen to fit a future study for amputation levels. The aim was to evaluate the multiprobe for that purpose. A laser Doppler fluxmeter with a standard and a multiprobe was used. Measurements were made in five probe sites in lower limbs of healthy volunteers. Each subject was studied by 30-second recordings during 60 min with both probes. Statistically (p < 0.001) lower flux values were obtained with the multiprobe than with the standard probe. The flux variation between the five probe sites was significantly (p < 0.01) higher with the standard probe than with the multiprobe, but the temporal variation was similar with both probes. The results suggest that the spatial variation in widely separated probe sites is reduced with the multiprobe. The temporal variation was not found to be reduced.

Adult↗
PubMedDate not supplied

Reference sample microsphere method to measure blood flow effects on small intestinal perfusion in the rat.

To evaluate whether the microsphere method, including the necessary surgical procedures, for blood flow determination creates hemodynamic stress and a secondary reduction in small intestinal perfusion, we monitored the small intestinal perfusion with laser Doppler (LD) fluxmetry in 3 groups of Sprague-Dawley rats. Group I was studied during two microsphere injections without manipulation, group II was subjected to mesenterial-root occlusion during the second injection, and for group III, vasodilatation with papaverine preceded the second injection. While cardiac output and kidney blood flow were constant at the two microsphere injections, mean blood pressure (p < 0.05) and hematocrit (p < 0.01) significantly decreased in all 3 groups. Blood glucose increased significantly (p < 0.01). LD values also declined significantly (p < 0.05) between the start and end of experiments. In group I, the initial values of 9.5 perfusion units (PU) (5-23) decreased to 6.5 PU (3-12), in group II, 10.5 PU (5-24) decreased to 7.0 PU (4-15) and in group III, 9.0 PU (5-13) decreased to 5.5 PU (4-12). In conclusion, these findings suggest that the microsphere technique with two injections of spheres and reference sample withdrawals may affect the perfusion of the small intestine in the Sprague-Dawley rat.

Animals↗