Knut Kvernebo

Erythromelalgia: a clinical study of 87 cases

Abstract. Kalgaard OM, Seem E, Kvernebo K (Ullevaal Hospital, Oslo, Norway). Erythromelalgia: a clinical study of 87 cases. J Intern Med 1997; 242: 191–7.

Four years' results of a prospective, randomized clinical trial comparing polytetrafluoroethylene and modified human umbilical vein for below-knee femoropopliteal bypass

Polytetrafluoroethylene (PTFE) (Gore-Tex) and human umbilical vein (Biograft) arterial grafts were compared for below-knee femoropopliteal bypass grafting in a prospective randomized clinical trial. One hundred five patients (105 limbs) entered the trial. Seventy-six percent suffered from rest pain, ulceration, or gangrene. The median postoperative ankle-arm blood pressure index was 0.36. Twenty-three limbs had three patent tibial arteries, 46 limbs had two tibial arteries, 31 limbs had one patent artery, and five limbs had isolated popliteal segments. Thirty-four percent were repeat operations. Fifty-five patients were allocated to receive PTFE grafts and 50 to receive human umbilical vein grafts. The two groups were comparable as to preoperative risk factors and operative and postoperative treatment. During the first 4 years (maximum 1609 days) 40 PTFE grafts and 24 umbilical veins occluded. At 1 year the PTFE patency rate was 53% and at 4 years was 22%. For umbilical vein the corresponding figures were 74% and 42% (p = 0.005, Gehan test). During follow-up the incidence of PTFE failure was on the average 2.1 times higher than that of umbilical vein failure (95% confidence limits 1.2 to 3.4).

Periprosthetic leak and rupture after endovascular repair of abdominal aortic aneurysm : The significance of device design for long-term results

We present a case of abdominal aortic aneurysm treated with an endovascular bifurcated aortic graft in which a periprosthetic leak caused by a tear in the polyester prosthesis appeared between 9 and 12 months after surgery. The tear appeared adjacent to a suture breakage that caused separation of two struts of the nitinol wire framework in the body of the stent graft. The leak was sealed with insertion of a new endovascular tube graft into the body of the bifurcation. Eight months later, the patient had a nonfatal rupture of the abdominal aortic aneurysm because detachment of the second limb from the bifurcation caused a new major periprosthetic leak. According to the manufacturer of this device, suture breakage with separation of metal components is commonly seen, but perforation of the polyester prosthesis caused by movement of the metal stent against the fabric has not been reported. It is likely that this occurred in our patient. Detachment of the second limb from the bifurcated stent, causing a rupture, has been described before. Increasing angulation and tortuosity of the stent graft, as a result of either remodeling of the sac or elongation of the stent, and reduced compliance to angulation after the stent-in-stent procedure might have contributed to the detachment in this case.

Enhanced endothelium-dependent vasodilatation in human skin vasculature induced by physical conditioning

Functional alterations to the endothelial cells of the vascular system may contribute to the improved circulatory performance induced by physical conditioning. We evaluated microvascular reactivity to iontophoretic application of acetylcholine (ACh) and sodium nitroprusside (SNP) through the skin and blood perfusion measurements in the same area using laser Doppler flowmetry. Whereas ACh acts on smooth muscle cells of the vascular system via the production of vasodilator substances from the endothelium, SNP is an endothelium-independent vasodilator acting on vascular smooth muscle cells directly. The study was performed using two groups of subjects with different levels of aerobic endurance, long distance runners competing at national level (n = 9) and controls (n = 9). The subjects were tested for 40 min on a treadmill before and after an exercise test at 80% of their maximal oxygen uptake. During stimulation by ACh cutaneous perfusion increased to a higher level in the athletes than in the controls (overall P < 0.05), whereas an acute period of exercise abolished this difference (overall P > 0.6). There was no significant difference between the athletes and the controls with respect to the SNP-induced increase in cutaneous perfusion either before (P > 0.9) or after (P > 0.9) exercise. The higher cutaneous perfusion responses to stimulation with ACh in the athletes than in the controls may support the hypothesis that regular exercise modifies the responsiveness of the cutaneous endothelium. The difference in ACh-induced perfusion and in unstimulated forearm perfusion between the two groups was present only at rest. This finding indicated that mechanisms were introduced during exercise, which compensated for the lower endothelial sensitivity to stimulation in the controls at rest.

Hypertension prophylaxis with omega-3 fatty acids in heart transplant recipients.

OBJECTIVES This study sought to determine whether omega-3 fatty acids act as hypertension prophylaxis in heart transplant recipients and have an impact on vascular reactivity. BACKGROUND Cyclosporine-induced hypertension is probably related to endothelial dysfunction. Suggested vasodilatory mechanisms of omega-3 fatty acids may therefore be particularly beneficial in heart transplant recipients. METHODS Heart transplant recipients were randomized to receive either 4 g of omega-3 fatty acids (treatment group, n = 14) daily or corn oil (placebo group, n = 14) from the fourth postoperative day. Twenty-four hour blood pressure monitoring was performed at day 12 and 1,2,3 and 6 months postoperatively. Microvascular endothelium-dependent vasodilation, evaluated by skin laser Doppler perfusion measurements of postocclusive reactive hyperemia, was determined preoperatively and at the end of the study. RESULTS With comparable characteristics at the time of randomization, blood levels of cyclosporine did not at any point differ between the groups. After 6 months, systolic blood pressure decreased 2 +/- 4 mm Hg (mean +/- SEM) in the treatment group and increased 17 +/- 4 mm Hg in the placebo group (p < 0.01), whereas diastolic blood pressure increased 10 +/- 3 and 21 +/- 2 mm Hg (p < 0.01), respectively. The decrease in systolic blood pressure was inversely proportional to increases in concentrations of serum eicosapentaenoic and docosahexaenoic acid (p = 0.01). After 6 months, five patients in the treatment group and nine in the placebo group needed additional antihypertensive treatment. Although the endothelial-dependent phase of the reactive hyperemic response remained unchanged in the treatment group, it decreased significantly in the placebo group. CONCLUSIONS Postoperative daily administration of 4 g of omega-3 fatty acids in heart transplant recipients is effective as hypertension prophylaxis, depending on increases in serum eicosapentaenoic and docosahexaenoic acids. Preservation of microvascular endothelial function, demonstrated by a more pronounced response to forearm skin ischemia in the treatment group, may contribute to the hypotensive role of omega-3 fatty acids.

Multiple Emboli and Filter Function: An in Vitro Comparison of Three Vena Cava Filters!

PURPOSE To establish the influence of number of emboli on the trapping ability of vena cava filters in vitro. MATERIALS AND METHODS Three filters, the titanium Greenfield, Vena Tech-LGM, and Günther Tulip retrievable, were studied with use of 20- or 26-mm-diameter tubes to simulate the inferior vena cava. In the first protocol, five small (4 x 20-mm) or medium (6 x 10-mm) emboli were delivered in sequence, and the fate of each was recorded. In the second protocol, medium or large (6 x 30-mm) clots were sequentially introduced until filter occlusion occurred or 50 clots had been delivered. RESULTS For the first protocol, 82% of first small clots and 60% of second clots were trapped in 20-mm tubes (P = .001) and 63% and 45%, respectively, were trapped in 26-mm tubes (P - .02). With medium clots, the proportion trapped also dropped significantly with ascending clot rank. In the second protocol the proportion of clots captured was invariably higher for the first 10 clots (P < .001 for all combinations of covariables). CONCLUSION Filter function deteriorates with number of emboli delivered, irrespective of embolus size and simulated vein caliber.

Assessment of human muscle blood perfusion with single-fiber laser Doppler flowmetry

Laser Doppler flowmetry (LDF) is a technique for continuous monitoring of microvascular perfusion. Commercially available flowmeters in general are equipped with probes constructed for performing measurements on superficial tissue surfaces, but small (phi = 0.45 mm) metallic needle probes for in-tissue measurements are also available. In this study a flexible single-fiber LDF probe with a total diameter of 0.5 mm has been inserted into human tibial muscle and used for assessment of local muscle blood flow. Local muscle perfusion shows a considerable spatial variation. If the probe position is not changed between consecutive measurements, reproducible curve parameters are obtained. Vasomotion was not observed in any measurement. The hyperemic blood flow response was recorded after tourniquet deflation. Time to reach peak magnitude as well as duration of the hyperemic blood flow response was increased significantly (P less than 0.01) with prolonged occlusion time. The response was found in both skin and muscle blood flow recordings. Increasing occlusion time from 3 to 5 min did not significantly enhance the results. Comparison of skin and muscle responses with respect to time to reach peak magnitude showed a significant difference (P less than 0.02) for the 1-min occlusion. A significant increase (P less than 0.01 and 0.05 for muscle and skin, respectively) in peak flux was seen in muscle and skin when tourniquet occlusion was increased from 1 to 3 min. Further increases in occlusion time did not produce significant increases in peak flux. The technique is easy to use, and may be of value in studies of disturbances of perfusion in muscle and possibly in parenchymatous organs (transplantation surgery) and central nervous system circulation.

Pain in primary erythromelalgia--a neuropathic component?

&NA; Erythromelalgia is a condition characterized by attacks of red, hot, painful extremities with relief of symptoms by cooling and aggravation by warmth. Although the main emphasis has been on pathophysiological mechanisms related to circulatory changes, recent reports have focused on an involvement of efferent small nerve fibers indicating a neuropathic component. Since the symptoms resemble those described in neuropathic pain, we wanted to investigate the possible affection of afferent nerve fibers. Twenty‐five patients with primary erythromelalgia were examined by neurological testing, neurography and quantitative sensory testing. Thresholds for heat, cold, heat‐pain and cold‐pain detection were compared with those of a group of 29 healthy controls. The patients had significantly higher median heat (39.5 (36.1–40.8) and cold (29.3 (27.1–30.8)‐detection thresholds at the dorsal aspects of their feet compared to the controls (37.0 (35.4–37.7) and 31.2 (30.3–31.5) respectively). These findings show an impaired small fiber function inside or close to the symptomatic area in this group of erythromelalgia patients. Seven patients had brush‐evoked allodynia and fourteen had punctate hyperalgesia inside or close to the symptomatic areas in their feet. When comparing the individual results, there is a tendency to clustering of patients in two separate groups; reduced small fiber input/no hyperalgesia and normal thermal thresholds/hyperalgesia. Our results showing an affection of afferent small nerve fibers together with the nature of the symptoms, suggest that the pain experienced by erythromelalgia patients could have a neuropathic component.

Laser Doppler flux reappearance time (FRT) in patients with lower limb atherosclerosis and healthy controls.

Laser doppler flowmetry was used to examine the skin circulation in the lower limb during postischaemic reactive hyperaemia. Flux reappearance time (FRT), the time from tourniquet deflation to the start of the hyperaemic response, was determined from the recorded curves, and the aim of the study was to investigate whether FRT is dependent on total limb vascular resistance or to the resistance in a segment of the limb. FRT was first compared with the clinical situation of the examined subjects, and with the resting ankle blood pressure index (API). Controls had an immediate hyperaemic response (FRT less than or equal to 3 s), while patients with critical ischaemia had prolonged FRT (greater than 48 s). Among the claudicators there was no significant correlation between API or ankle blood pressure and FRT. When FRT was compared with angiography, all claudicators who only had significant atherosclerosis proximal to the tourniquet, had FRT values within the control range. Patients who only had distal atherosclerosis had prolonged values (greater than 15 s), indicating that FRT is independent of proximal atherosclerosis and reflects the vascular resistance in the arteries in the segment between the tourniquet and the measuring probe. This interpretation was supported by the reduction of pathologically prolonged FRT when the distance between the tourniquet and the measuring site was reduced. We conclude that FRT as measured by this technique seems to reflect the vascular resistance in the run off arteries distal to the tourniquet.

Human microvascular imaging: a review of skin and tongue videomicroscopy techniques and analysing variables

Imaging techniques are increasingly important in clinical diagnostic work. Microcirculation is essential for function and survival of all tissues, but imaging techniques for microvascular monitoring of patients have only been used to a limited extent in clinical practice. The microcirculation is complex with its static and dynamic feature, and only skin and oral mucosa are readily accessible for microscopic examination. In addition, there is a no general agreement on which microvascular parameters and analysing techniques that could be useful. The aim of this article is to give an overview of techniques for human intra‐vital microscopy and to describe software and variables used to analyse pictures and film sequences of human microcirculation. We also present clinical examples where microvascular examinations have been shown to be of diagnostic value. Improved techniques for assessing microvascular morphology and physiology will probably become important tools in clinical work in many disciplines in the near future.