Dependent oedema and attenuation of postural vasoconstriction associated with nifedipine therapy for hypertension in diabetic patients

A Review of Microvascular Measurements in Wound Healing

The microcirculatory evaluation in patients affected by arteriopathic or venous ulcers is usually carried out using laser Doppler flowmetry, transcutaneous oxygen (transcutaneous pressure of oxygen, TcPO2), and carbon dioxide (transcutaneous pressure of carbon dioxide, TcPCO2) measurements and capillaroscopy. These techniques provide significant pathophysiologic and prognostic information. TcPO2 and TcPCO2 diagnose and classify the extent of arterial disease in the leg ulcers caused by arterial disease; the prognostic value is recognized, though doubts about its prognostic potential exist in the case of leg ulcer. Laser Doppler flowmetry is able to identify the first functional impairment in the early stages of the arterial disease and in the complicated venous insufficiency. Capillaroscopy gives us morphological and quantitative parameters of the capillary bed that is damaged in arteriopathic and venous ulcers; nevertheless, it does not provide us with definite prognostic indexes. Combining the 3 methods may contribute to yield objective measures in the clinical management of lower extremity ulcers.

Pramipexole-related chronic lower limb oedema in a patient with Parkinson's disease

Pramipexole is a non-ergot dopamine agonist that is used frequently as a single therapy or in combination for the management of Parkinson's disease. Common side effects are daytime drowsiness, hypotension, hallucinations and compulsive behaviour. We describe a patient who developed severe chronic and extensive lymphoedema after pramipexole was introduced and that resolved after its cessation.

Role of combination therapy in the treatment of hypertension: focus on valsartan plus amlodipine

Hypertension control is rare in clinical practice, particularly in high-risk patients. A large factor is therapeutic inertia deriving from poorly prescribed lifestyle changes, excess monotherapy use, and scarce on-treatment modifications. The use of drug combinations significantly improves blood pressure (BP) control; in particular, fixed combinations improve therapy without increasing daily pill intake, thereby favouring patient compliance and therapy continuation. The most widely used fixed combination is based on thiazide diuretics added to either angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs). Several large-scale clinical trials have been conducted showing that these combinations are effective in lowering BP. However, thiazide diuretics can reduce the metabolic benefits derived from renin-angiotensin-aldosterone system (RAAS) inhibitors in high metabolic risk patients. In contrast, ACE inhibitors or ARBs combined with dihydropyridine calcium channel antagonists (DHPCAs) exert a marked antihypertensive effect without decreasing metabolic protection by RAAS blockade. In the recent JIKEI heart study, approximately 60% of patients affected by hypertension, heart failure, coronary heart disease or their combination in the valsartan arm were simultaneously treated with DHPCAs. Of note, a 39% reduction in the primary endpoint of combined morbidity and mortality was reported in the valsartan compared with the non-valsartan arm. Furthermore, in a recent multinational study, 83% of 3161 hypertensive patients treated with valsartan and the DHCPA amlodipine reported a concontrolled BP after 8 weeks of treatment. As expected, amlodipine did not negatively influence the metabolic profile of patients, thereby supporting the role of ARB+DHPCA combinations as effective and promising tools in hypertension treatment. In summary, the combination of ARBs with DHPCAs is an effective strategy in hypertension treatment through synergy between their antihypertensive and vascular protective actions, persistent metabolic benefits deriving from RAAS inhibition, and reduced incidence of side effects.

Long-term effects of endovascular angioplasty on orthostatic vasocutaneous autoregulation in patients with peripheral atherosclerosis

OBJECTIVE

To test the hypothesis that endovascular revascularization of femoropopliteal lesions improves the impaired venoarteriolar response (VAR) in patients with atherosclerosis.

METHODS

We prospectively compared VARs in 15 healthy controls (18 legs) and 14 patients (17 legs) with mild to moderate peripheral arterial disease before and after successful peripheral endovascular angioplasty of femoropopliteal lesions. In all subjects, foot skin blood flow was assessed by laser Doppler flowmetry in the horizontal (HBF) and sitting (SBF) positions. VAR was calculated as (HBF - SBF)/HBF x 100.

RESULTS

In patients with peripheral arterial disease, mean HBF (in arbitrary units [AU]; mean +/- SD) was similar before (25.6 +/- 15.3 AU) and after (27.0 +/- 16.4 AU) angioplasty (P = .67), whereas SBF was significantly lower after than before the endovascular procedure (11.6 +/- 7.7 AU to 18.4 +/- 14.1 AU; P < .05). Intragroup differences between SBF and HBF were significant before and after angioplasty (P < .001). VAR was higher after angioplasty (55.1% +/- 21.2%) compared with VAR before intervention (33.4% +/- 20.2%; P = .015). Although VAR increased after the intervention, VAR was still lower than in healthy controls (68.4% +/- 20.5%; P = .025). During the 6 months of follow-up, the ankle-brachial index and VAR remained unchanged (P > .05).

CONCLUSIONS

Patients with mild to moderate peripheral arterial disease have an impaired orthostatic autoregulation that improves after successful endovascular revascularization of femoropopliteal obstructive lesions. The effect on VAR is sustained in the absence of restenosis.

The insulin sensitiser pioglitazone does not influence skin microcirculatory function in patients with type 2 diabetes treated with insulin

AIMS/HYPOTHESIS

Insulin resistance is associated with abnormal microvascular function. Treatment with insulin sensitisers may provoke oedema, suggesting microvascular effects. The mechanisms underlying the peripheral oedema observed during glucose-lowering treatment with thiazolidinediones are unclear. Therefore we examined the effect of pioglitazone on microvascular variables involved in oedema formation.

METHODS

Subjects (40-80 years) with type 2 diabetes and on insulin were randomised to 9 weeks of pioglitazone therapy (30 mg/day; n=14) or placebo (n=15). The following assessments were performed at baseline and 9 weeks: microvascular filtration capacity; isovolumetric venous pressure; capillary pressure; capillary recruitment following venous or arterial occlusion; postural vasoconstriction; and maximum blood flow. A number of haematological variables were also measured including vascular endothelium growth factor (VEGF), IL-6 and C-reactive protein (CRP).

RESULTS

Pioglitazone did not significantly influence any microcirculatory variable as compared with placebo (analysis of covariance [ANCOVA] for microvascular filtration capacity for the two groups, p=0.26). Mean VEGF increased with pioglitazone (61.1 pg/ml), but not significantly more than placebo (9.76 pg/ml, p=0.94). HbA(1c) levels and the inflammatory markers IL-6 and CRP decreased with pioglitazone compared with placebo (ANCOVA: p=0.009, p=0.001 and p=0.004, respectively).

CONCLUSIONS/INTERPRETATION

Pioglitazone improved glycaemic control and inflammatory markers over 9 weeks but had no effect on microcirculatory variables associated with oedema or insulin resistance in type 2 diabetic patients treated with insulin.

Peripheral sympathetic autoregulation in arterial calf inflow enhancement with intermittent pneumatic compression

BACKGROUND

Peroperative mortality, graft failure and balloon angioplasty limitations mitigate against active intervention for claudication. With the exception of exercise programmes, conservative treatments yield limited results. Intermittent pneumatic compression of the foot (IPC(foot)) used daily for over 3 months enhances significantly the walking ability and pressure indices of stable claudicants; this is attributable to the significant calf inflow enhancement with IPC(foot); however, the physiologic mechanisms involved are only partially understood. Aims by comparing the effects of IPC(foot)and postural alteration on calf inflow haemodynamics, this study examines the role of peripheral sympathetic autoregulation, which controls homeostasis in lower limb vessels when posture changes, in the enhancement of calf inflow with IPC(foot)in healthy subjects and claudicants.

MATERIAL AND METHODS

forty-one limbs of healthy subjects (n =34; Group I) and 48 limbs of stable claudicants (Fontaine II) (n =42; Group II) were studied. The volume flow (Q), pulsatility index (PI), mean (mV), peak systolic (PSV) and end diastolic (EDV) velocities were measured in the popliteal artery using duplex ultrasound in: the horizontal position, and on sitting with or without IPC(foot).

RESULTS

in Group II: median Q, mV, PSV and EDV increased by 61%, 53%, 29% and 51% respectively, and PI decreased by 20% as posture changed from sitting to horizontal; with IPC(foot)median Q, mV, PSV and EDV increased by 70%, 58%, 22% and 75% respectively, and PI decreased by 26% (all p < 0.001). In Group I: median Q, mV, PSV and EDV increased by 125%, 115%, 51% and 38% respectively and PI decreased by 30% as posture changed from sitting to horizontal; with IPC(foot)median Q, mV, PSV and EDV increased by 119%, 153%, 23% and 46%, respectively, and PI decreased by 50% (all p < 0.001). The effects of IPC(foot)and postural alteration (from sitting to horizontal) did not differ haemodynamically (p > 0.1) in both groups. Q on lying was similar in Groups I and II. On sitting Q was higher in Group II [p =0.027 (95% CI 1.7, 27 ml/min)].

CONCLUSIONS

the striking similarity in the haemodynamic effects of IPC(foot)and postural alteration in the popliteal artery strongly suggests that the leg inflow enhancement with IPC(foot)is mediated by a transient suspension of peripheral sympathetic autoregulation. In addition to their role as clinical markers of PVD severity, the autoregulatory reflexes of peripheral circulation appear to have functions with significant clinical implications in the management of patients with leg inflow impairment.

Calcium channel blockers, postural vasoconstriction and dependent oedema in essential hypertension

Treatment with calcium channel blocker (CCB)s, dihydropyridines and others, is frequently complicated by dependent oedema in the absence of sodium retention or cardiac failure, a bothersome side effect of unclear aetiology. The present paper reviews our own and other work dealing with the antagonism exerted by such drugs on postural vasoconstriction, a mechanism triggered by limb venous congestion during orthostasis and controlled through a local sympathetic axo-axonic reflex and increased myogenic tone in response to changes in transmural pressure. By stabilising capillary pressure, postural vasoconstriction counteracts fluid hyperfiltration consequent to gravitational stimuli, and consistent evidence shows attenuation of this response by L-type calcium channel blockers. Interference with the postural reflex control of skin blood flow may therefore contribute to dependent oedema, although cannot entirely explain its development. Attenuation of postural vasoconstriction may amplify the fluid hyperfiltration induced by CCBs through other mechanisms, such as imbalanced intracapillary pressure or enhanced vascular permeability, which are the main factors determining net fluid filtration into the interstitial compartment.

Sympathetic autoregulation in peripheral vascular disease

BACKGROUND

Lower limb venous pressure increases on dependency, stimulating a local sympathetic axon reflex which triggers precapillary and arteriolar vasoconstriction. The resulting decrease in arterial calf inflow, known as the venoarteriolar response (VAR), is impaired in critical leg ischaemia. The aim of the study was to evaluate the VAR in symptomatic non-critical leg ischaemia and after restoration of leg perfusion following successful revascularization.

METHODS

The study included 30 normal subjects, 30 patients with stable intermittent claudication and 30 patients with severe ischaemia who had undergone successful infrainguinal revascularization. In all patients the foot skin blood flow (flux) in the horizontal (HBF) and sitting (SBF) positions was measured using laser Doppler fluxmetry. The VAR was calculated as (HBF - SBF)/HBF x 100 per cent. The pressure that elicited the reflex (pVAR) was evaluated in the horizontal position.

RESULTS

The median VAR was significantly lower in patients with stable claudication than in normal subjects or patients following successful revascularization (29.1 versus 59.5 and 63.9 per cent respectively; P < 0.0001). Similar results were obtained for the pVAR (22 versus 45 and 40 mmHg respectively; P < 0.001). There was no difference, however, in either the VAR or pVAR between normal individuals and patients following a successful bypass.

CONCLUSION

Patients with claudication had a significant impairment of orthostatic sympathetic autoregulation. After successful revascularization, and in spite of the extensive disease in the receiving circulation, this autoregulation returned to normal. Presented previously to the Vascular Surgical Society in London, November 1997 and published in abstract form as Br J Surg 1998; 85: 557

Amlodipine, enalapril, and dependent leg edema in essential hypertension

Calcium channel blockers (CCBs) blunt postural skin vasoconstriction, an autoregulatory mechanism that minimizes gravitational increases in capillary pressure and avoids fluid extravasation when standing. To evaluate the dose-response relation between this pharmacological interference and dependent edema, a frequent side effect of CCBs during antihypertensive treatment, skin blood flow (laser Doppler flowmetry) at the dorsum of the foot, both supine and with the limb passively placed 50 cm below the heart level, and leg weight (Archimedes principle) were measured at baseline, during increasing doses of the dihydropyridine amlodipine (5 and 10 mg UID each for 2 weeks), and after drug withdrawal in 10 hypertensive men. Because angiotensin-converting enzyme inhibitors may attenuate ankle swelling by CCBs, those parameters were evaluated according to a similar design during amlodipine (10 mg UID) and enalapril (20 mg UID) combined (n=10). As a control, the effect of enalapril monotherapy (10 and 20 mg UID for 2 weeks each) was evaluated in a third series of patients (n=8). Amlodipine (5 mg UID) increased leg weight without modifying postural vasoconstriction (the percent skin blood flow decrease from horizontal to dependent position), which indicates that extravascular fluid shift was independent of postural skin vasoconstriction. At 10 mg UID, however, amlodipine blunted postural vasoconstriction and increased leg weight further, which suggests that skin blood flow autoregulation limited additional fluid transfer. Both parameters normalized after drug withdrawal. Enalapril per se did not affect cutaneous vasomotion or leg weight but reduced the amount of dependent fluid extravasation by the CCB despite a persistent antagonism for postural vasoconstrictor responses.

Idiopathic edema

Idiopathic edema is a syndrome of real or perceived excessive weight gain. This article reviews what is known about the possible causes, evaluation, and treatment. Although the cause is unknown but often thought to be due to secondary hyperaldosteronism, primary abnormalities of the hypothalamus, thyroid, dopaminergic release or renal dopaminergic metabolism, vascular basement membrane, or capillary sphincter control could perhaps contribute in some patients. The diagnosis requires careful attention to possible abnormalities of the liver, heart, kidneys, gastrointestinal tract, thyroid, and pancreas. The history must include an evaluation for risks of bulimia and purging; diuretic and laxative screening should be performed. Specific records of daily weights, urinary outputs, and menstral cycle dates are useful. Treatment may include dietary counseling to provide weight control and a constant carbohydrate intake, treatments for depression, compression stockings, spironolactone, amiloride, angiotensin II inhibitors, or sympathomimetic agents, depending on the severity and timing of the patient's symptoms. Unfortunately, idiopathic edema may be a multifactorial disorder that has not been completely delineated. Further research into possible causative mechanisms is required before a more useful algorithm for evaluation and treatment is available.

Nifedipine increases microvascular permeability via a direct local effect on postcapillary venules

Calcium-channel antagonist drugs are prescribed widely for angina and hypertension. A limiting side effect is edema, which can make heart failure worse. We show that nifedipine, a dihydropyridine-type calcium-channel antagonist, can increase vascular permeability in rat skeletal muscle and skin when injected locally. In nifedipine-injected cremaster muscle, the copper content, used to quantify Monastral blue dye accumulation, was 15.0 +/- 2.4 microgram/g compared with 5.3 +/- 0.7 microgram/g in control preparations (P < 0. 05). The injection of nifedipine in rat skin in vivo increased local plasma leakage in injected sites from 5.5 +/- 1.1 microliter in control sites to 9.9 +/- 2.5, 17.0 +/- 2.4, 24.3 +/- 5.9, and 23.3 +/- 5.4 microliter in sites injected with 10(-10), 10(-9), 10(-8), or 10(-7.2) mol/site, respectively (P < 0.05 in each case compared with control). Vascular labeling techniques using light microscopy, electron microscopy, and microanalysis show that the microvascular site of leakage is not from capillaries but from postcapillary venules of 12-36 micrometer in diameter, the same site that controls the edema response in inflammation. Nifedipine can act within the microcirculation to increase the permeability of the postcapillary venule.

Cardiac inotropes inhibit the oedema caused by nifedipine in rabbit skin

1. We have shown previously that exposing the rat or rabbit microcirculation to nifedipine increases the permeability of the post-capillary venule, the segment of microcirculation that is known to control inflammatory oedema. 2. In the present study modulation by the inotropes isoprenaline, dopexamine and dobutamine of nifedipine-induced oedema was examined in the rabbit skin microcirculation by measuring the localised leakage of 125I-radiolabelled albumin after the i.d. injection of agents. 3. Coinjection of isoprenaline (10(-11) moles per site), dopexamine (10(-10) moles per site) or dobutamine (10(-10) moles per site) suppressed significantly (P < 0.05) the oedema response to nifedipine (10(-7.2) moles per site) in the rabbit dorsal skin microcirculation. 4. To confirm the oedema suppresser effect of the inotropes, dopexamine or dobutamine were also coinjected with histamine 10(-8) + PGE2 10(-10) moles per site, or bradykinin 10(-10) + PGE2 10(-10) moles per site. Both inotropes at 10(-10) moles per site reduced significantly (P < 0.05) the leakage of albumin caused by bradykinin + PGE2 and histamine + PGE2. 5. When measured by laser Doppler, basal local skin blood flow increased at 30 min by 57 +/- 14% with nifedipine 10(-7.2) moles per site and 15 +/- 11% with isoprenaline 10(-11) moles per site. Isoprenaline did not suppress the blood flow response to nifedipine, the response to coinjection being 68 +/- 11%. 6. Oedema caused by nifedipine can be suppressed by low concentrations of beta-adrenergic agonists that do not suppress the blood flow response to nifedipine. This suggests that cardiac inotropes can influence non-inflammatory changes in microvascular permeability.

Comparison of diltiazem and verapamil on rat microvascular permeability

Calcium channel antagonists are among the most widely prescribed cardiovascular drugs. Their benefit is limited by the side effect of edema, the microvascular mechanism of which is not known. We compared the local effect on edema formation in rat skin and skeletal muscle of two calcium channel antagonists, diltiazem and verapamil, and determined if the edema effect correlated with changes in microvascular flow. An increase in microvascular flow can potentiate edema formation by increasing microvascular hydrostatic pressure and the proportion of the bed that is perfused. Diltiazem, but not verapamil or control, injected s.c. in scrotal skin caused plasma albumin leakage visualized as local bluing of tissue in rats that had been pretreated with Evans blue dye systemically. Topographic studies using Monastral blue dye showed that in the underlying cremaster muscle, diltiazem increased leakage of dye particles not from capillaries but from postcapillary venules. The postcapillary venule is associated with inflammatory edema, suggesting a direct effect of diltiazem on endothelial permeability. The local injection of diltiazem also increased significantly (P < 0.05) plasma leakage quantified as the local accumulation of systemically injected 125I-radiolabeled albumin, from 14.5 +/- 2.0 and 6.9 +/- 1.0 microliters in control sites to 30.0 +/- 7.3 and 18.0 +/- 2.5 microliters in dorsal skin and abdominal rat skin, respectively. In contrast, verapamil at similar doses did not increase plasma albumin leakage significantly. At the doses that caused local skin edema, diltiazem had less effect on microvascular skin blood flow, measured by a laser Doppler flow probe, (12.6 +/- 5.3% at 15 min and 2.8 +/- 8.4% change at 30 min) than verapamil (39.0 +/- 7.3% at 15 min 30.0 +/- 6.7% change at 30 min, P < 0.01). The microvascular effects of these two calcium channel antagonists differ in that diltiazem had a significant effect on microvascular permeability whereas verapamil had a significant effect on microvascular blood flow.

Effect of calcium channel blockade on skin blood flow in diabetic hypertension: a comparison of isradipine and atenolol

In previous studies, using laser Doppler techniques, the authors have demonstrated a duration-dependent reduction in skin blood flow reserve at sites of nutritive (NUTR) perfusion that occurs in diabetes and correlates with the presence of diabetic retinopathy and proteinuria. They speculated that it might be possible to reverse this decrease in blood flow by using agents with peripheral vasodilating properties. They chose the calcium channel blocking agent isradipine as a prototype. As a contrast agent, they chose atenolol, which has an equivalent antihypertensive effect but minimal peripheral vasodilating properties. They studied 24 diabetic hypertensive patients in a randomized, two-way crossover design. They assigned patients randomly to one or the other active drug and titrated to a maximum tolerated maintenance dose. Skin blood flow was measured at the end of the titration and maintenance phases. Patients then entered a four-week washout period, followed by crossover to the alternative drug, and measurements were repeated. At baseline, the twenty-four-hour mean ambulatory systolic blood pressure was 150 +/- 2 mm Hg with a twenty-four-hour mean diastolic blood pressure of 93 +/- 1 mm Hg. Thermally stimulated skin blood flow reserve was about 50% lower in these patients as compared with an age-, sex-, and weight-matched group of 28 nondiabetic, nonhypertensive patients. There was no difference in skin blood flow between the two groups at basal skin temperature or at a controlled temperature of 35 degrees C. Both atenolol and isradipine successfully lowered blood pressure in the study patients. There was a slightly greater decrease in systolic blood pressure with isradipine and a greater decrease in heart rate with atenolol. Neither isradipine nor atenolol treatment affected skin blood flow values at the maximal 44 degrees C temperature. However, at basal skin temperature and at 35 degrees C, isradipine-treated patients had substantial increases in skin blood flow at NUTR sites. For example, skin blood flow at the knee at 35 degrees C with isradipine treatment was 3.1 +/- 0.4 mL/min/100 g compared with 1.1 +/- 0.2 with atenolol, 1.3 +/- 0.1 with placebo, and 0.9 +/- 0.1 for the nondiabetic controls (all P < 0.01). The authors found a twofold to threefold increase in basal skin blood flow at NUTR sites with isradipine treatment. This degree of increase is substantially greater than that previously demonstrated by their group using pentoxifylline. Locally reduced skin blood flow is a factor in promoting skin breakdown and delayed healing. Further study is needed to explore the possibility that isradipine treatment may enhance healing of diabetic skin ulcers.