Allosteric modulation and accelerated resensitization of human P2X(3) receptors by cibacron blue

The activity of ATP as a fast neurotransmitter is mediated by the P2X family of ligand-gated ion channels. P2X receptor subtypes are subject to functional modulation by a diverse set of factors, including pH, divalent cations, and temperature. The human P2X(3) (hP2X(3)) receptor subunit is expressed primarily in sensory ganglia where it exists as either a homomultimeric receptor or, in combination with P2X(2), as a heteromultimeric receptor. This article describes the allosteric modulatory effect of the putative P2X receptor antagonist cibacron blue on the activity of recombinant hP2X(3) receptors. In 1321N1 cells expressing the hP2X(3) receptor, cibacron blue mediated a 3- to 7-fold increase in both the magnitude and the potency of ATP-activated Ca(2+) influx and transmembrane currents. The half-maximal concentration of cibacron blue required to mediate maximal potentiation (EC(50) = 1.4 microM) was independent of the agonist used to activate the hP2X(3) receptor. The nonselective P2 receptor antagonist PPADS (pyridoxal-5-phosphate-6-azophenyl-2',4'-disulfonic acid) caused a rightward shift of the cibacron blue concentration-effect curve, whereas increasing concentrations of cibacron blue attenuated PPADS antagonism. In addition to potentiating the effects of ATP at the hP2X(3) receptor, cibacron blue also produced a 6-fold increase in the rate of hP2X(3) receptor recovery from desensitization (from T(1/2) = 15.9 to 2.6 min), as evidenced by its ability to restore ATP responsiveness to acutely desensitized receptors. Consistent with the properties of other ligand-gated ion channels, these results suggest that hP2X(3) receptor activity can be allosterically modulated by a ligand distinct from the endogenous agonist.

Observations on medical device design, Part II: Good practice

Current guidance on design is inadequate. This second article in a two-part series presents a framework for good design practice that attempts to improve designers' awareness of manufacturing and validation issues. Seven design tactics, derived from observations of current industry practice and design literature, seek to encourage good practice and achieve safer, more profitable devices.

Observations on medical device design, Part I: Current practice

Medical devices must be designed and proven to be fit for the purpose that they were intended. Good design practice ensures this fitness for purpose and is reflected in the commercial success of products. This two-part article focuses on current industry design practice and proposes that there are significant benefits to be obtained by defining good design practice: better products and reduced development costs.

Primary prevention of childhood lead exposure: A randomized trial of dust control

BACKGROUND

Dust control is recommended as one of the primary strategies to prevent or control children's exposure to residential lead hazards, but the effect of dust control on children's blood lead levels is poorly understood.

OBJECTIVE

To determine the effectiveness of dust control in preventing children's exposure to lead, as measured by blood lead levels, during their peak age of susceptibility.

DESIGN

A randomized, controlled trial.

SETTING

Rochester, NY.

PARTICIPANTS

A total of 275 urban children were randomized at 6 months of age, of whom 246 (90%) were available for the 24-month-old follow-up visit.

INTERVENTIONS

Children and their families were randomly assigned to an intervention group (n = 140), which received cleaning equipment and up to eight visits by a dust control advisor, or a control group (n = 135).

OUTCOME MEASURES

Geometric mean blood lead levels and prevalence of elevated blood lead levels (ie, >10 microg/dL, 15 microg/dL, and 20 microg/dL).

RESULTS

At baseline, children's geometric mean blood lead levels were 2.9 microg/dL (95% confidence interval [CI] = 2.7, 3.1); there were no significant differences in characteristics or lead exposure by group assignment, with the exception of water lead levels. For children in the intervention group, the mean number of visits by a dust control advisor during the 18-month study period was 6.2; 51 (36%) had 4 to 7 visits, and 69 (49%) had 8 visits. At 24 months of age, the geometric mean blood lead was 7.3 microg/dL (95% CI = 6.6, 8.2) for the intervention group and 7.8 microg/dL (95% CI = 6.9, 8. 7) for the control group. The percentage of children with a 24-month blood lead >/=10 microg/dL, >/=15 microg/dL, and >/=20 microg/dL was 31% versus 36%, 12% versus 14%, and 5% versus 7% in the intervention and control groups, respectively.

CONCLUSIONS

We conclude that dust control, as performed by families and in the absence of lead hazard controls to reduce ongoing contamination from lead-based paint, is not effective in the primary prevention of childhood lead exposure.

Workday communication and ambulatory blood pressure: implications for the reactivity hypothesis

Ambulatory blood pressure monitoring was used to investigate the cardiovascular correlates of naturally occurring interpersonal interactions. Participants were New York City traffic agents, who routinely engage in conflict-prone communication with the public under relatively fixed conditions. Talking with the public, supervisors, or coworkers was associated with levels of systolic and diastolic blood pressure and heart rate that exceeded a resting baseline. Blood pressure was higher when agents were talking to the public than when they were talking to coworkers or engaged in a noncommunicative work task. Systolic blood pressure response during communication was associated with the agent's mood. Blood pressure effects associated with communication appear to persist after the communication has ceased. Implications of these data for the reactivity hypothesis of the pathogenesis of cardiovascular disease are discussed.

Restoring vascular nitric oxide formation by L-arginine improves the symptoms of intermittent claudication in patients with peripheral arterial occlusive disease

BACKGROUND

Administration of L-arginine improves nitric oxide (NO) formation and endothelium-dependent vasodilation in atherosclerotic patients.

OBJECTIVES

We investigated in this double-blind, controlled study whether prolonged intermittent infusion therapy with L-arginine improves the clinical symptoms of patients with intermittent claudication, as compared with the endothelium-independent vasodilator prostaglandin E1, and control patients.

METHODS

Thirty-nine patients with intermittent claudication were randomly assigned to receive 2 x 8 g L-arginine/day, or 2 x 40 microg prostaglandin E1 (PGE1)/day or no hemodynamically active treatment, for 3 weeks. The pain-free and absolute walking distances were assessed on a walking treadmill at 3 km/h, 12% slope, and NO-mediated, flow-induced vasodilation of the femoral artery was assessed by ultrasonography at baseline, at 1, 2 and 3 weeks of therapy and 6 weeks after the end of treatment. Urinary nitrate and cyclic guanosine-3', 5'-monophosphate (GMP) were assessed as indices of endogenous NO production.

RESULTS

L-Arginine improved the pain-free walking distance by 230+/-63% and the absolute walking distance by 155+/-48% (each p < 0.05). Prostaglandin E1 improved both parameters by 209+/-63% and 144+/-28%, respectively (each p < 0.05), whereas control patients experienced no significant change. L-Arginine therapy also improved endothelium-dependent vasodilation in the femoral artery, whereas PGE1 had no such effect. There was a significant linear correlation between the L-arginine/asymmetric dimethylarginine (ADMA) ratio and the pain-free walking distance at baseline (r=0.359, p < 0.03). L-Arginine treatment elevated the plasma L-arginine/ADMA ratio and increased urinary nitrate and cyclic GMP excretion rates, indicating normalized endogenous NO formation. Prostaglandin E1 therapy had no significant effect on any of these parameters. Symptom scores assessed on a visual analog scale increased from 3.51+/-0.18 to 83+/-0.4 (L-arginine) and 7.0+/-0.5 (PGE1; each p < 0.05), but did not significantly change in the control group (4.3+/-0.4).

CONCLUSIONS

Restoring NO formation and endothelium-dependent vasodilation by L-arginine improves the clinical symptoms of intermittent claudication in patients with peripheral arterial occlusive disease.

Intra-arterial and intravenous administration of prostaglandin E1 cause different changes to skin microcirculation in patients with peripheral arterial occlusive disease

BACKGROUND

Disturbed skin microcirculation in patients with peripheral arterial occlusive disease (PAOD) might be affected by prostaglandin E1 (PGE1). The purpose of this study was to investigate local skin perfusion at the forefoot and toe of PAOD patients during different modes of administration of PGE1.

PATIENTS AND METHODS

In 17 patients with severe PAOD local intradermal haemoglobin oxygen saturation (SHB) and dermal vascular reserve capacity, transcutaneous oxygen pressure (tcPO2) and laser Doppler flux (LDF) were determined during intra-arterial (1.5 ng/kg body weight/min) and intravenous (6 ng/kg body weight/min) infusion of PGE1.

RESULTS

SHB significantly increased at both locations during intravenous PGE1; intra-arterial administration significantly increased SHB in the skin of the forefoot only. Reserve capacity increased during intravenous administration and was markedly reduced during intra-arterial infusion. No significant changes were found regarding tcPO2 and LDF.

CONCLUSIONS

These data suggest different therapeutic mechanisms for intra-arterial and intravenous administered of PGE1.

Prostaglandin E1 in peripheral vascular disease: a PET study of muscular blood flow

BACKGROUND

Increase of blood flow in the ischaemic leg is believed to represent the main action of prostaglandin E1 (PGE1) in the therapy of peripheral vascular disease (PVD). There is no reliable data in man concerning the amount of increase in muscular blood flow (MBF) of the calf, and the difference between intra-arterial and intravenous application.

PATIENTS AND METHODS

We conducted a positron emission tomography (PET) study of MBF with 15O-water as flow tracer. Fifteen patients with PVD and three healthy volunteers were given 5 micrograms PGE1 intra-arterially over 50 min; PET scans were taken at 0, 25 and 50 min. Additionally, eight of the patients were investigated during an intravenous infusion of 40 micrograms PGE1 over 120 min; PET scans were taken at 0, 30, 60 and 120 min.

RESULTS

Increase of muscular blood flow by intra-arterial PGE1 averaged 80%. A steal phenomenon was not observed. The amount of flow enhancement depended on whether or not the femoral artery was patent. During intravenous PGE1, muscular blood flow remained unchanged.

CONCLUSIONS

In man, the pharmacodynamic profile of intra-arterial PGE1 differs clearly from intravenous PGE1. The flow-enhancing property is lost during metabolization in the lung. Since no difference exists between the therapeutic efficacy of intraarterial and intravenous PGE1, the impact on muscular blood flow is not as important as suggested previously.

Aerobic exercise for a patient with chronic multisystem impairments

Many patients with long-term disabilities have inactive lifestyles that put them at risk for chronic diseases and secondary disabilities. The purpose of this case report is to illustrate the process of aerobic exercise prescription for a patient with chronic multisystem impairments. The patient was a 43-year-old man who incurred a traumatic brain injury and multiple fractures in a motorcycle accident 15 years previously. He subsequently developed heterotopic ossification around the right hip. In addition, the patient had a history of smoking. We chose a "nontraditional" mode of exercise for the patient that we believed would be safe and effective and would accommodate his neurologic and orthopedic impairments. The mode of exercise used was an apparatus in which the upper and lower extremities alternately flexed and extended in a nonreciprocal fashion. The patient attended 12 exercise sessions over a 1-month period, during which he demonstrated acute and chronic physiological responses appropriate for the exercise stimulus.

Sailing without radar: an excursion in resource allocation

This paper deals with the knowledge base employed in resource allocation. It deliberately distinguishes between 'thick-textured' and 'thin-textured' knowledge. A thick-textured view of change in the health sector accounts for the history, civic goods and variety of human needs and passions which rationalist economics defines out as a thin-textured matter of individual choices in a free market. The narrative material begins with a discussion of health service policy-making in South Australia and elsewhere in the 1980s and 1990s, then proceeds to a discussion of priority-setting literature, which we regard as thin-textured. We offer two accounts of approaches to setting priorities in health care which we think have overcome some of the deficiencies of the thin-textured approach.

Dose-related effect of intravenous L-arginine on muscular blood flow of the calf in patients with peripheral vascular disease: a H215O positron emission tomography study

1. Endothelium-derived nitric oxide (NO) contributes to the regulation of vascular tone and blood pressure. Infusion of L-arginine produces systemic vasodilatation via stimulation of endogenous NO formation. Vasodilatation is accompanied by an increase in peripheral arterial blood flow. However, it is not known whether capillary nutritive blood flow increases as well. The time course and dose-response pattern of this effect remain to be elucidated. 2. Two groups of ten patients with peripheral vascular disease (PVD) received an intravenous infusion of 8 g or 30 g of L-arginine over a period of 40 min. Blood pressure and heart rate were monitored non-invasively. Muscular blood flow (MBF) of the calf was determined at 0, 20, 40, 60, 80 min by positron emission tomography with H215O as flow tracer. Plasma L-arginine and cyclic GMP (cGMP) levels were determined at the same time points. 3. L-arginine induced a dose-related decrease in blood pressure during the infusion period. MBF and plasma cGMP levels during and after the infusion of 8 g of L-arginine did not change significantly. In the patients receiving 30 g of L-arginine, MBF was enhanced significantly from 1.56 +/- 0.14 to 2.09 +/- 0.21 ml min-1 100 ml-1 at 40 min and 2.23 +/- 0.15 ml min-1 100 ml-1 after 80 min (+43.0%). The increase in MBF was paralleled by an increase in plasma cGMP from 4789.8 +/- 392.2 nmol/l at baseline to 9223.2 +/- 1233.6 nmol/l at 40 min. 4. We conclude that intravenous L-arginine enhances nutritive capillary MBF in patients with PVD via the NO-cGMP pathway in a dose-related manner. This effect might be therapeutically beneficial in patients with PVD.

Vital capillary microscopy of skin areas at the forefoot of diabetic patients using intraarterial injection of Na-fluorescein

A modified technique of vital capillary microscopy with intraarterial application of Na-fluorescein has been introduced in the study of nutritional skin microcirculation to assess skin microcirculation of different diabetic patients, comprising one group without neurocutaneous complications (group 2; n = 9), one suffering only from neuropathy (group 3; n = 9) and one with trophic skin lesions in the contralateral foot (group 4; n = 8), all without macroangiopathy, compared to healthy controls (group 1; n = 9). Femoroarterial injection of small boli (10 mg) of Na-fluorescein allowed repeated investigation of the dye appearance times (AT) and capillary-filling times of forefoot skin capillaries within small periods of time before, during and after reactive hyperemia. At rest, AT was significantly shorter in patients of group 4 (16.8 +/- 4.4 s; p < 0.05) compared with groups 1-3 (34.3 +/- 12.8; 31.7 +/- 11.7 and 35.9 +/- 15.3 s). Fifteen seconds after the end of arterial occlusion, dye propagation to the skin was markedly accelerated in groups 1-3 (19.8 +/- 14.0; 14.4 +/- 7.6 and 18.7 +/- 10.6 s, respectively; p < 0.001), but prolonged in group 4 (18.4 +/- 7.4 s). After 10 min, the values at rest were reestablished. No differences between the four groups were found concerning capillary density and morphology. It is concluded that the development of skin lesions in diabetic patients without significant macroangiopathy may be favored by hyperperfusion and impaired vasoregulation. Intraarterial dye injection presents a valuable tool to assess dynamic alterations of the microcirculation at the level of skin capillaries.

Ten strategies for creating successful managed care relationships

Among the many customers providers serve are managed care organizations. The strategic relationships providers develop with these payers greatly influence the long-term success of both organizations. Providers can implement 10 strategies to improve their managed care relationships: focusing on contracting with selected managed care organizations, fostering positive relationships, coordinating contract participation, establishing communication links, educating providers about managed care, providing high-quality customer service; understanding operating costs, demonstrating value, maintaining flexibility, and pursuing alternative competitive relationships with caution. At the same time, managed care organizations can implement the same strategies to develop win/win relationships with providers.

Biochemical evidence for impaired nitric oxide synthesis in patients with peripheral arterial occlusive disease

BACKGROUND

We studied urinary nitrate and cGMP excretion rates, indices of systemic NO formation, and plasma concentrations of L-arginine and the endogenous NO synthase inhibitor asymmetrical dimethylarginine (ADMA) and its inactive stereoisomer, symmetrical dimethylarginine, in 77 patients with peripheral arterial occlusive disease (PAOD) in Fontaine stages IIb through IV and in 47 young and 37 elderly healthy control subjects.

METHODS AND RESULTS

Urinary nitrate excretion was 182.0+/-11.4 micromol/mmol creatinine and cGMP excretion was 186.2+/-13.0 nmol/mmol creatinine in young healthy control subjects. In elderly control subjects, both excretion rates were slightly lower (nitrate, 156.0+/-7.8 micromol/mmol creatinine; cGMP, 150.0+/-8.3 nmol/mmol creatinine; P=NS). In PAOD patients, there was a significant, progressive reduction of urinary nitrate (IIb, 138.4+/-11.9; III, 128.6+/-11.3; and IV, 91.9+/-8.0 micromol/mmol creatinine; P<.05) and cGMP (IIb, 139.9+/-25.2; III, 115.6+/-13.1; and IV, 76.9+/-7.9 nmol/mmol creatinine; P<.05) excretion rates related to the Fontaine stage of PAOD. These changes were independent of changes in renal excretory function. Plasma L-arginine concentrations were not significantly different between the groups, but ADMA concentrations were elevated in PAOD patients (young control subjects, 1.25+/-0.11; elderly control subjects, 1.01+/-0.05 micromol/L; IIb, 2.62+/-0.24; III, 3.06+/-0.48; and IV, 3.49+/-0.26 micromol/L; P<.05 for PAOD versus control subjects). There was a significant linear correlation between urinary nitrate and cGMP excretion rates and a significant negative linear correlation between plasma ADMA concentrations and urinary nitrate excretion.

CONCLUSIONS

In PAOD patients, there is a progressive reduction in urinary nitrate and cGMP excretion rates, which may be caused in part by accumulation of ADMA, an endogenous inhibitor of NO synthase.

Treatment of primary Raynaud's syndrome with traditional Chinese acupuncture

OBJECTIVE

Evaluation of the effects of a standardized acupuncture treatment in primary Raynaud's syndrome.

DESIGN

A controlled randomized prospective study.

SETTING

A winter period of 23 weeks, angiological clinic of Hannover Medical School.

SUBJECTS

Thirty-three patients with primary Raynaud's syndrome (16 control, 17 treatment).

INTERVENTIONS

The patients of the treatment group were given seven acupuncture treatments during the weeks 10 and 11 of the observation period.

MAIN OUTCOME MEASURES

All patients kept a diary throughout the entire observation period noting daily frequency, duration and severity of their vasospastic attacks. A local cooling test combined with nailfold capillaroscopy was performed for all patients at baseline (week 1) and in weeks 12 and 23, recording flowstop reactions of the nailfold capillaries.

RESULTS

The treated patients showed a significant decrease in the frequency of attacks from 1.4 day-1 to 0.6 day-1, P < 0.01 (control 1.6 to 1.2, P = 0.08). The overall reduction of attacks was 63% (control 27%, P = 0.03). The mean duration of the capillary flowstop reaction decreased from 71 to 24 s (week 1 vs. week 12, P = 0.001) and 38 s (week 1 vs. week 23, P = 0.02) respectively. In the control group the changes were not significant.

CONCLUSIONS

These findings suggest that traditional Chinese acupuncture is a reasonable alternative in treating patients with primary Raynaud's syndrome.

Oxygen-15-water PET assessment of muscular blood flow in peripheral vascular disease

To assess quantitatively regional nutritive muscular blood flow in patients with peripheral vascular disease (PVD), we evaluated the utility of PET with 15O-water.

METHODS

Eight healthy volunteers and 16 patients with angiographically proven PVD were studied. Regional blood flow of the calf was measured with 15O-water PET during rest, after intra-arterial infusion of prostaglandin E1 and during ergometry. The studies were quantified using a one tissue compartment model.

RESULTS

Normalized mean tracer uptake from 15-60 sec correlated closely (r = 0.98) with absolute blood flow. Scan times longer than 90 sec were required to determine blood flow reliably. The flow values were overestimated by 2% if arterial blood volume was neglected or if the input function delay was corrected globally for parametric imaging. Mean blood flow of calf muscles at rest did not differ significantly between patients (0.017 +/- 0.006 ml/min/ml) and control subjects (0.018 +/- 0.010 ml/min/ml). In PVD patients, blood flow increased by 100% after intra-arterial infusion of PGE1 in the respective leg. In the control subjects, average flow increased by a factor of six during exercise. The increase was more pronounced in the extensor muscles (0.182 +/- 0.031 ml/min/ml) than in flexor muscles (0.121 +/- 0.045 ml/min/ml). Due to the specific type of ergometry, superficial flexors exhibited higher flow values than the profound ones.

CONCLUSION

PET with 15O-water enables reliable determination of regional nutritive skeletal muscle blood flow for research and clinical applications in patients with PVD.

Non-invasive determination of dermal hemoglobin oxygenation and concentration in patients with peripheral arterial occlusive disease

BACKGROUND

Oxygen saturation (SHB) and concentration (CHB) of dermal hemoglobin are important parameters for the supply of the skin. They may be non-invasively assessed by means of reflection photometry as hemoglobin is predominantly contributing to the skin reflection spectrum.

METHODS AND RESULTS

Dermal reflection spectra from the middle of the forefoot and from the tip of the toe of 20 healthy subjects and 61 patients suffering from peripheral arterial occlusive disease (PAOD) were recorded and compared to transcutaneous oxygen pressure (tcPO2). SHB, and tcPO2 were significantly higher in controls: compared to patients (ankle pressure (AP) > 50 mmHg) SHB in the skin of the forefoot was 63.8 vs. 54.5% (p < 0.05), CHB was 0.89 vs. 0.62 aU (p < 0.01). In the great toe SHB was 92.9 vs. 59.9% (p < 0.001), CHB was 2.21 vs. 0.92 aU (p < 0.001). Heating the skin of the forefoot to 44 degrees C yields local dermal vascular reserve capacity: SHB and CHB increased in all healthy subjects (96.4%; 1.44 aU, respectively). SHB decreased at the forefoot in 14 and at the toe in 18 of 21 patients with AP < 50 mmHg. At the toe decrease was found in 50 of 61 patients (sensitivity 82%, specificity 100%).

CONCLUSIONS

Local vascular reserve capacity of dermal perfusion is reduced in patients with PAOD, depending on AP. It should be determined preferably in patients with severe PAOD.

Hypothenar hammer syndrome successfully managed with intravenous prostaglandin E1 and heparin and with correction of the thrombogenic risk profile. A case report

A fifty-one-year-old man presented with a history, symptoms, and clinical findings typical of a hypothenar hammer syndrome in his dominant hand. A thrombotic obstruction in the distal section of the ulnar artery with multiple downstream occlusions of proper digital arteries were documented angiographically. Coexistence of additional cardiovascular risk factors (smoking-induced polycythemia, obesity, hypercholesterolemia, and hypertension) was identified. Conservative management with intravenous heparin and prostaglandin E1 together with measures directed at controlling the additional risk factors (repeated venesection, immediate smoking cessation, and low-lipid diet) resulted in a striking clinical and angiographic improvement of the digital perfusion, without resort to interventional measures or thrombolysis.

A new method for the assessment of tissue hemoglobin oxygenation in patients with chronic venous insufficiency

Venous incompetence often leads to ulceration of the skin of the lower limb due to a disturbance of skin microcirculation. We investigated 10 healthy subjects and 18 patients with chronic venous insufficiency by means of a fast scanning reflection photometer and determined noninvasively the hemoglobin oxygen saturation (S(HB)) and the relative concentration of hemoglobin (C(HB)) in the skin of the forefoot and at the calf, 10 cm proximal of the inner malleolus during positional changes. In supine position no significant differences were found. During sitting and standing S(HB) dropped and was significantly lower in patients at both locations (calf, standing, patients 22.2 +/- 10.6% vs controls 48.2 +/- 13.5%, P < 0.001). C(HB) increased in patients during standing from 0.71 to 2.13 +/- 0.33 aU (in controls from 0.69 to 1.49 +/- 0.28 aU, P < 0.001). Activation of the muscle pump decreased C(HB) and increased S(HB) in patients and in controls. After the movements were stopped, S(HB) decreased again and fell to the initial low values eight times faster in patients (7.4 +/- 5.3 vs 57.5 +/- 19.6 sec, P < 0.001). C(HB) increased four times faster in patients (7.2 +/- 6.1 vs 29.9 +/- 13.6 sec). In sitting and standing positions hemoglobin oxygenation in the skin of the lower limb was markedly reduced in patients, but normal perfusion conditions were restored in supine position, indicating reversibility of the changes. Reflection oxymetry seems a valuable tool for the assessment of chronic venous insufficiency. The substantially reduced oxygenation of dermal hemoglobin in standing patients may contribute to the development of venous ulcers.

Orthostatic vasoconstrictor response in patients with occlusive arterial disease assessed by laser Doppler flux and transcutaneous oximetry

Posturally induced microvascular constriction normally causes a decrease of transcutaneous oxygen pressure (tcPO2) and laser Doppler flux (LDF) measured on the forefoot at 37 degrees C. The authors used both methods to assess the vasoconstrictor response (VCR) in 31 patients with various degrees of peripheral arterial occlusive disease (PAOD) and analyzed factors that could have influenced the response. Disturbed VCR was indicated by a signal increase following leg dependency, which occurred significantly more often in tcPO2 than in LDF measurements (69% vs 32%, P < 0.001). Correspondingly the median sitting/supine ratio was 2.4 for tcPO2 and 0.7 for LDF (P < 0.0001). Age and clinical stage had no influence on the VCR. With ankle artery pressures below 50 mmHg an increase of LDF was more probable. TcPO2 predominantly increased with ankle artery pressure up to 100 mmHg, though the sitting/supine ratio of tcPO2 was correlated with ankle artery pressure. In nondiabetics the response of tcPO2 but not of LDF was influenced by the values at rest. Differences between the two methods may be explained in part by their different sample volumes. The authors assume that tcPO2 is predominantly monitoring a local myogenic response while LDF is reflecting venoarteriolar response.

L-arginine induces nitric oxide-dependent vasodilation in patients with critical limb ischemia. A randomized, controlled study

BACKGROUND

L-Arginine is the precursor of endogenous nitric oxide (NO), which is a potent vasodilator acting via the intracellular second-messenger cGMP. In healthy humans, L-arginine induces peripheral vasodilation and inhibits platelet aggregation due to an increased NO production. Prostaglandin E1 (PGE1) induces peripheral vasodilation via stimulating prostacyclin receptors.

METHODS AND RESULTS

We investigated the effects of one intravenous infusion of L-arginine (30 g, 60 minutes) or PGE1 (40 microgram, 60 minutes) versus those of placebo (150 mL 0.9% saline, 60 minutes) on blood pressure, peripheral hemodynamics, and urinary NO3- and cGMP excretion rates in patients with critical limb ischemia (peripheral arterial occlusive disease stages Fontaine III or IV). Blood flow in the femoral artery was significantly increased by L-arginine (+42.3 +/- 7.9%, P<.05) and by PGE1 (+31.0 +/- 10.2%, P<.05) but not by placebo (+4.3 +/- 13.0%, P=NS). Urinary NO3- excretion increased by 131.8 +/- 39.5% after L-arginine (P<.05) but only by 32.3 +/- 17.2% after PGE1 (P=NS). Urinary cGMP excretion increased by 198.7 +/- 84.9% after L-arginine (P<.05) and by 94.2 +/- 58.8% after PGE1 (P=NS). Both urinary index metabolites were unchanged by placebo.

CONCLUSIONS

We conclude that intravenous L-arginine induces NO-dependent peripheral vasodilation in patients with critical limb ischemia. These effects are paralleled by increased urinary NO3- and cGMP excretion, indicating an enhanced systemic NO production. Increased urinary NO3- excretion may be a sum effect of NO synthase substrate provision (L-arginine) and increased shear stress (PGE1 and L-arginine).

[How often is thrombolytic therapy of deep pelvic-leg venous thrombosis indicated?]

BACKGROUND

For patients with deep vein thrombosis new thrombolytic regimes are being proposed and demand evaluation in controlled studies. We tested prospectively, how many patients in internal medicine are candidates for thrombolysis.

PATIENTS AND METHODS

All available patients with the diagnosis of deep vein thrombosis (DVT) in lower extremities who were admitted to the service of internal medicine in a medium-sized hospital during one year were prospectively evaluated for the indication of fibrinolysis therapy according to the established criteria.

RESULTS

A total of 62 patients were enrolled. Fibrinolysis was not proposed in 25 patients aged over 70 years nor in another 9 patients in whom the thrombosis was restricted to calf veins. Nine additional cases had a recurrence of DVT (n = 4) or a history of more than 14 days. Among the remaining 19 patients, fibrinolysis was not performed in 11 because of advanced malignomas (n =4) or other diseases (n = 3) with limited life expectance, enhanced probability of haemorrhage (n = 3) and obvious non-compliance (n = 1). Eight patients were offered thrombolytic therapy, but 5 of them denied consent after being comprehensively informed.

CONCLUSION

Obviously by far most of patients admitted to internal medicine for DVT are candidates for standard heparin therapy only.