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Nocturnal differences in subcutaneous tissue glucose between forearm and abdominal sites during continuous glucose monitoring in normal subjects.

OBJECTIVE: A number of short-term studies using the continuous glucose monitoring system (CGMS) indicate that improved metabolic control can be observed in patients with type 1 diabetes when CGMS is applied in clinical practice. Data have also accumulated to suggest that spot measurements of glucose performed four times a day would not detect as much as 70% of all hypoglycaemic episodes registered by CGMS. When more frequent reference values were obtained however it was inferred that nighttime hypoglycaemia reported by CGMS may be spurious. As most assessments with CGMS have been utilizing abdominal subcutaneous tissue, we were interested to evaluate whether differences between blood glucose and sensor readings obtained from different sites exist. RESEARCH DESIGN AND METHODS: Two viscometric affinity glucose sensors, applicable to subcutaneous tissue of both forearm and abdomen, were inserted subcutaneously in 12 non-diabetic subjects. Sensors generated glucose data at 3 min intervals and venous blood glucose was determined in duplicates by HemoCue at 15-90 min intervals for 24 hours. Each subject consumed three carbohydrate-rich meals, performed an exercise test, and was observed during nocturnal bed-rest at the research center. RESULTS: The initial decrease of blood glucose during exercise was not fully detected by the sensors. Otherwise, no significant differences between sensor values and blood glucose were observed during day-time. During nocturnal bed-rest abdominal sensor values came approximately 20% lower than blood glucose (P<0.001) and forearm sensor readings. CONCLUSION: It is concluded that a difference between glucose values obtained from abdominal and forearm subcutaneous fat can be observed during nocturnal bed-rest in non-diabetics.

Abdomen↗

[Stability of the forearm after resection of the distal ulna and proximal radius in rheumatoid arthritis: report of 11 cases].

Combined resection of radial head and distal ulna could jeopardize the stability and kinematics of the forearm bones. The goals of this retrospective study was to investigate these data after resection of distal ulna and proximal radius in rheumatoid arthritis. Between 1990 and 1998, eleven patients had these bone resections combined with implantation of elbow prostheses (eight Kudo and three GSB III). Wrist surgery consisted in five wrist arthrodeses combined with Darrach procedure, four Sauvé-Kapandji procedures and two isolated Darrach procedures. Mean age at surgery was 58 years and the average follow-up was 40 months. We assessed at follow-up: 1) wrist and elbow pain according to Gschwend; 2) stability of the forearm bones (cubitus valgus angle, impingement of the proximal radial stump with humerus, giving away accident of the ulnar distal stump); 3) wrist and elbow mobility. At follow-up six patients had no pain at the elbow and five had slight occasional pain. At the wrist, five patients had no pain and six slight occasional pain. Elbow motion was increased (from mean 83 degrees [50 degrees-100 degrees] to mean 110 degrees [85 degrees-135 degrees]) excepted in supination which slightly decreased (from mean 3 degrees [40 degrees-90 degrees] to mean 75 degrees [85 degrees-90 degrees]). Mean wrist mobility was impaired because of the five combined radiocarpal arthrodeses. If these five wrist arthrodeses were excluded, the mean ranges of motion were: 10 degrees in flexion, 16 degrees in extension, 2 degrees in radial deviation, 14 degrees in ulnar deviation. At follow-up, no patient had giving away accident of the ulnar distal stump nor impingement between radial stump and humerus in full flexion. Average cubitus valgus was 10 degrees. This study pointed out the predominant effect of the interosseous membrane in stability of the forearm bones.

Adult↗

Severe atherosclerosis of the radial artery in a free radial forearm flap precluding its use.

The free radial forearm flap is the most frequently used free flap for head and neck reconstructions. Survival of free flaps is dependent on adequate blood supply. A 69-year old woman was scheduled for excision of a T3N0M0 oropharyngeal carcinoma, neck dissections and reconstruction with a free vascularized radial forearm flap. During the operation it appeared that the entire radial artery was almost completely obstructed by atherosclerotic plaques precluding microvascular anastomosis. Despite systemic risk factors certain artery types are more prone to develop clinically manifest atherosclerosis. There are no reports on the pathology of the radial artery in free flap reconstructions. In head and neck cancer patients severe atherosclerosis of the radial artery is very rare, but if present makes free radial forearm flap reconstruction impossible. Therefore, in patients with risk factors for peripheral vascular disease screening for radial artery stenosis should be considered.

Aged↗

The effects of partial chronic denervation on forearm metabolism.

Effects of chronic denervation upon in vivo forearm metabolism were studied in six patients and six controls. The diagnosis was amyotrophic lateral sclerosis in four patients, the neuronal form of Charcot-Marie Tooth disease in one patient, and an unclassified chronic disease of the lower motor neurons in one patient. In all cases the forearm muscles showed clinical weakness and electrical evidence of denervation, while muscle biopsy from a proximal muscle of the upper limb showed typical denervation atrophy. At rest there was increased oxygen utilization and lactate output as well as a tendency for increased uptake of glucose and long chain fatty acids from arterial blood per 100 ml of forearm tissue. During exercise the abnormally high lactate output increased further. An increased arterial lactate concentration was present during rest and exercise. Oxidation of fatty acids was not impaired. It is suggested that these abnormalities are consistent with an augmented utilization of blood borne fuels at rest by denervated muscles. A concurrent regional ischemia of muscles during rest and exercise, possibly due to defective autoregulation of skeletal muscle blood flow, may explain the abnormally high lactate generation.

Adult↗

Tribological testing of skin products: gender, age, and ethnicity on the volar forearm.

BACKGROUND/PURPOSE: Few studies have focused on the simultaneous measurement of the friction and electrical properties of skin. This work investigates the feasibility of using these measurements to differentiate between the effects of chemicals commonly applied to the skin. In addition, this study also compares the condition of the skin and its response to application of chemicals across gender, ethnicity, and age at the volar forearm. METHOD: Friction and electrical tests were performed on 59 healthy volunteers with the UMT Series Micro-Tribometer (UMT). A 13-mm-diameter copper cylindrical friction/electrical probe was pressed onto the skin with a weight of 20 g and moved across the skin at a constant velocity of 0.4 mm/s. Each volunteer served as his or her own control. The friction and electrical impedance measurements were performed for polyvinylidene chloride occlusion and for the application of glycerin and petrolatum. RESULTS: No differences were found across age, gender, or ethnicity at the volar forearm. Polyvinylidene chloride (PVDC) occlusion showed a small increase in the friction and a small decrease in the electrical impedance; petrolatum increased the friction by a greater amount but its effect on the impedance was comparable to PVDC occlusion; glycerin increased the friction by an amount comparable to petrolatum, but it decreased the impedance to a much greater degree than petrolatum or the PVDC occlusion. An amplitude/mean measurement of the friction curves of glycerin and petrolatum showed that glycerin has a significantly higher amplitude/mean than petrolatum. CONCLUSION: The properties of the volar forearm appear to be independent of age, gender, and ethnicity. Also, the simultaneous measurement of friction and electrical impedance was useful in differentiating between compounds administered to the skin.

Adolescent↗

Forearm and finger hemodynamics, blood pressure control, and lipid changes in patients with diabetic hypertension treated with atenolol and prazosin.

Hypertension and diabetes mellitus frequently coexist and are independent risk factors for reduced peripheral perfusion. Antihypertensive medications that reduce blood pressure and improve peripheral perfusion would have advantages in diabetic patients with hypertension. In a randomized, two-placebo period, single-blind, two-way crossover study, we determined finger and forearm blood flow, lipid levels, and blood pressure control in 19 diabetic patients with hypertension, with each atenolol or prazosin and placebo period of 4 weeks' duration. Both drugs reduced blood pressure (sitting: 157/95 to 142/84 mm Hg, atenolol; 155/95 to 138/82 mm Hg, prazosin; standing: 154/94 to 144/84 mm Hg, atenolol; 154/94 to 133/81 mm Hg, prazosin). Lipid levels did not change except that low-density lipoprotein levels fell from 148 to 127 mg/dl with prazosin. Atenolol did not change forearm or finger blood flow or vascular resistance. Prazosin increased blood flow and reduced vascular resistance in both finger and forearm. In conclusion, prazosin has a potentially more appropriate hemodynamic profile than has atenolol in diabetic patients with hypertension.

Adult↗

Forearm arterial distensibility in patients with hypertension: comparative effects of long-term ACE inhibition and beta-blocking.

Fifty patients with mild or moderate hypertension were assessed for the influence on peripheral hemodynamics of 10 months of treatment with lisinopril (25 patients) or metoprolol (25 patients). Two-dimensional Doppler flowmetry was used for the evaluation. Responding patients (blood pressure < 150/90 mm Hg) were monitored for another 4 weeks after treatment withdrawal to determine whether changes in forearm hemodynamics, if any, persisted. Twenty-two patients from either group (88%) were considered to be responders. Systolic and diastolic blood pressure in patients receiving lisinopril dropped by 6% and 15%, respectively (p < 0.001), in those receiving metoprolol the decrease was 5.9% and 14%, respectively (p < 0.001). Forearm hemodynamics was not significantly different before treatment and improved in patients receiving lisinopril, with increased compliance (p < 0.001) and lower vascular resistance (p < 0.001). No significant changes were observed with metoprolol. After withdrawal, blood pressure returned to baseline values in both groups. However, improvement in forearm hemodynamics persisted in the lisinopril group. Hemodynamics changes were statistically different on lisinopril versus metoprolol both after treatment and after withdrawal. Lisinopril, but not metoprolol, seems capable to induce regression of functional and/or structural changes of large arteries in patients with hypertension.

Adult↗

Systemic ETA receptor antagonism with BQ-123 blocks ET-1 induced forearm vasoconstriction and decreases peripheral vascular resistance in healthy men.

1. The effect on systemic haemodynamics of BQ-123, a selective endothelin A (ETA) receptor antagonist, was investigated in healthy men by giving, on separate occasions, ascending intravenous doses of 100, 300, 1000 and 3000 nmol min(-1) BQ-123, each for 15 min, in a randomized, placebo-controlled, double-blind study. The response of forearm blood flow to brachial artery infusion of endothelin-1 (ET-1; 5 pmol min(-1) for 90 min) was also studied using bilateral forearm plethysmography, after systemic pre-treatment, on separate occasions, with one of two doses of BQ-123 (300 and 1000 nmol min(-1) for 15 min) or placebo. 2. Systemic BQ-123 dose-dependently decreased systemic vascular resistance (P<0.01 for all doses vs placebo) and mean arterial pressure (P<0.05 for 300 nmol min(-1) and P<0.01 for 1000 and 3000 nmol min(-1)) during the 60 min following infusion. There were concurrent increases in heart rate and cardiac index. BQ-123, when infused systemically for 15 min, appeared to reach a maximum effect at 1000 nmol min(-1). 3. Intra-brachial ET-1 infusion, after pre-treatment with placebo, caused a slow onset progressive forearm vasoconstriction without systemic effects. This vasoconstriction was attenuated by pre-treatment with BQ-123 at 300 nmol min(-1) and abolished by BQ-123 at 1000 nmol min(-1) (P<0.01 vs placebo). 4. These effects occurred at concentrations of BQ-123 in the plasma (510+/-64 nmol l(-1)) that were ETA receptor selective, and were not accompanied by an increase in plasma ET-1 that would have indicated ETB receptor blockade. 5. We conclude that ETA-mediated vascular tone contributes to the maintenance of basal systemic vascular resistance and blood pressure in healthy men.

Adolescent↗

Vascular effects of anandamide and N-acylvanillylamines in the human forearm and skin microcirculation.

The endocannabinoid anandamide is an emerging potential signalling molecule in the cardiovascular system. Anandamide causes vasodilatation, bradycardia and hypotension in animals and has been implicated in the pathophysiology of endotoxic, haemorrhagic and cardiogenic shock, but its vascular effects have not been studied in man. Human forearm blood flow and skin microcirculatory flow were recorded using venous occlusion plethysmography and laser-Doppler perfusion imaging (LDPI), respectively. Each test drug was infused into the brachial artery or applied topically on the skin followed by a standardized pin-prick to disrupt the epidermal barrier. Anandamide failed to affect forearm blood flow when administered intra-arterially at infusion rates of 0.3-300 nmol min(-1). The highest infusion rate led to an anandamide concentration of approximately 1 microM in venous blood as measured by mass spectrometry. Dermal application of anandamide significantly increased skin microcirculatory flow and coapplication of the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine inhibited this effect. The TRPV1 agonists capsaicin, olvanil and arvanil all induced concentration-dependent increases in skin blood flow and burning pain when administered dermally. Coapplication of capsazepine inhibited blood flow and pain responses to all three TRPV1 agonists. This study shows that locally applied anandamide is a vasodilator in the human skin microcirculation. The results are consistent with this lipid being an activator of TRPV1 on primary sensory nerves, but do not support a role for anandamide as a circulating vasoactive hormone in the human forearm vascular bed.

Adult↗

Similarity of cutaneous reactive hyperemia in the forearm of women with and without hyperinsulinemia.

OBJECTIVE: The present study was undertaken to assess in pre- and postmenopausal women whether obesity influences cutaneous reactive hyperemia in the forearm. DESIGN: Cross-sectional study. SUBJECTS AND METHODS: Eight lean premenopausal (age 24.6+/-3.5 y, BMI=21.9+/-1.5 kg/m(2), mean+/-1 s.d.), eight obese premenopausal (age 27.8+/-5.1 y, BMI=35.3+/-5.8 kg/m(2)), eight lean postmenopausal (age 56.1+/-8.3 y, BMI=20.2+/-2.2 kg/m(2)) and eight obese postmenopausal women (age 57.4+/-6.1 y, BMI=32.8+/-3 kg/m(2)) were included. Plasma glucose, insulin and lipid profile were determined in fasting state, and a glucose tolerance test was performed. The skin blood flow response to transient occlusion of the forearm circulation (reactive hyperemia, RH) was measured using a laser-Doppler imaging system. RESULTS: Obese women had hyperinsulinemia, suggesting that they were insulin-resistant. The magnitude of the RH was similar in postmenopausal compared to premenopausal women. Obesity did not influence this microvascular response. CONCLUSION: Obesity, which is known to be associated with impaired endothelial-dependent vasodilation in the skeletal musculature, has no effect on the RH of the forearm skin microcirculation.

Adult↗

Cold-induced elevation of forearm vascular resistance is inversely related to birth weight.

Fetal growth retardation has been linked to elevated blood pressure in adult life. This association between birth weight and blood pressure is present in childhood and is amplified with age. However, the mechanisms that underlie this association are largely unknown. We examined the relationship between birth weight and forearm vascular resistance and forearm blood flow in children aged 9-12.7 years. A total of 58 children were randomly selected from a cohort of 1610 born at the University Hospital of the West Indies in Jamaica where adequate antenatal and delivery records were available. Blood pressure, heart rate and forearm blood flow (by venous occlusion plethysmography) were measured at rest and after cold pressor and mental arithmetic tests. There was a significant inverse correlation between birth weight and the change in the vascular resistance for the cold pressor test (r=-0.47; P<0.001) and the mental arithmetic stress test (r=-0.26; P=0.05). The log ratio of vascular resistance under stress to resting decreased by 0.289 units per kg of birth weight (95% CI: 0.145-0.434; P=0.0002). Lower birth weight is associated with increased vascular responsiveness. Increased vascular resistance might be one mechanism linking fetal growth to subsequent elevated blood pressure.

Birth Weight↗

Effect of a surgically created side-to-side arteriovenous fistula on heat elimination from the human hand and forearm: evidence for a critical role of venous resistance in determining fistular flow.

1. In eight patients with a unilateral fistula between the radial artery and a nearby superficial vein, heat elimination from both hand and forearm, as measured by calorimetry, was always substantially greater on the side of the fistula (a mean excess from hand-plus-forearm 889 J/min). 2. Fistular blood flow measured by hand-plus-forearm plethysmography in these patients averaged 431ml/min. Correlation between fistular blood flow and heat elimination was poor (r = 0.70, P less than 0.06), probably because heat elimination due to the fistula takes place mainly from veins, whose pattern varies from patient to patient. 3. Approximately half of the total increased heat elimination due to the fistula is from the hand. Occlusion of the circulation to the hand caused fistular flow rate to be reduced by about half. This suggests that the main resistance to fistular is venous, proximal veins offering a similar resistance to distal veins. 4. The obligatory heat loss due to fistula is unlikely to embarrass temperature regulation, except in severe cold stress.

Adult↗

Forearm glucose uptake in cirrhosis and its relationship to glucose tolerance.

1. Oral glucose-tolerance tests (100 g) were carried out in six patients with stable well-compensated cryptogenic cirrhosis and in 12 control subjects. 2. In confirmation of previous studies, patients with cirrhosis had high post-glucose serum insulin levels and were glucose intolerant (mean incremental glucose area 954 +/- 186 compared with 482 +/- 35 mmol 3 h-1 l-1 in controls; P < 0.05). 3. Forearm arteriovenous differences of glucose and forearm blood flow were measured to estimate the proportion of the glucose load metabolized in peripheral tissues. Values in cirrhotic patients and control subjects (5614 +/- 1630 compared with 5344 +/- 672 mumol of glucose min-1 l-1 of forearm in 3 h) were similar despite higher glucose levels and sustained high insulin levels in the cirrhotic patients. 4. Peak lactate concentrations after glucose were of similar magnitude in the two groups (0.66 +/- 0.12 compared with 0.62 +/- 0.75 mmol/l) but in the patients with cirrhosis the peak occurred later and was more sustained. 5. The glucose intolerance of cirrhosis is primarily due to impaired hepatic retention of the glucose load. Insulin resistance in peripheral tissues may also be important since the higher insulin concentrations found in cirrhotic patients failed to enhance peripheral glucose uptake.

Adult↗

The effects of posture on abnormalities of forearm venous tone in women with pregnancy-induced hypertension.

1. Forearm venous tone was measured in the left lateral supine position and in response to passive leg elevation in a group of women with pregnancy-induced hypertension and compared with a group of normotensive pregnant women and a group of non-pregnant women. 2. The women with pregnancy-induced hypertension were venoconstricted in the supine position compared with the normal pregnant women (P less than 0.002). There was no difference in forearm venous tone between the women with pregnancy-induced hypertension and the non-pregnant women. 3. In response to passive leg elevation the women with pregnancy-induced hypertension venodilated (P less than 0.002) whereas there was no change in forearm venous tone in the normotensive pregnant women and the non-pregnant women. There was no change in blood pressure in any of the women after 35 min of leg elevation. 4. These results demonstrate that the abnormal venous vasoconstriction that occurs in women with pregnancy-induced hypertension in the supine position is corrected by passive leg elevation, a manoeuvre which leads to an increase in central blood volume.

Blood Pressure↗

Effects of nitroglycerin on forearm haemodynamics in patients with cirrhosis.

1. Basal forearm haemodynamics were studied by venous occlusion plethysmography in three groups of subjects: group I, healthy controls, group II, patients with cirrhosis age- and sex-matched with group I, and group III, an older group of patients with cirrhosis. Subsequently, responses to sublingual nitroglycerin were measured in group I and II subjects. 2. Controls responded to nitroglycerin with an increase in venous distensibility; group II patients had higher initial venous distensibility but did not respond to nitroglycerin. No other variables in either group were affected by nitroglycerin. 3. Group II and III patients differed in forearm blood flow and vascular resistance and venous distensibility. A significant inverse correlation was found between age and forearm blood flow (r = 0.57, P less than 0.001) in all patients with cirrhosis. 4. We conclude that (a) venous tone is reduced in cirrhosis, possibly as a result of chronic venodilatation; (b) this venodilatation impedes further dilatory response to a small dose of nitroglycerin; (c) cirrhosis is also associated with age-related decreases in peripheral haemodynamics.

Adolescent↗

Hysteresis of the venous pressure-volume relationship in the forearm of borderline hypertensive subjects.

1. The forearm venous pressure-volume relationship was studied in 14 young men with borderline hypertension and in 16 control subjects of the same age and sex. Strain-gauge plethysmography was used to evaluate volume changes after slow increases and decreases in distention, in order to estimate the amplitude of the hysteresis curve. 2. Compared with normotensive control subjects, subjects with borderline hypertension had significantly higher values of blood pressure, heart rate and forearm blood flow. 3. Baseline forearm venous tone was slightly, but not significantly, increased in borderline hypertensive subjects (21.35 +/- 6.53 versus 18.75 +/- 5.95 mmHg ml-1 100 ml-1) and was significantly enhanced after a cold pressor test. The increase was no higher in the borderline hypertensive subjects than in the normotensive control subjects. 4. The area of the hysteresis curve was significantly decreased (7.58 +/- 3.58 versus 10.34 +/- 5.67 arbitrary units; P = 0.0092) as was the extent of isotonic relaxation (creep) (0.28 +/- 0.11 versus 0.39 +/- 0.22 ml/100 ml; P = 0.0098) in borderline hypertensive subjects compared with control subjects. Both parameters were unaffected by the cold pressor test. 5. The study suggests that the viscous component of the venous wall is altered in young patients with borderline hypertension, indicating intrinsic changes in vascular segments which are not exposed to increased intraluminal pressure.

Adult↗

Glycerol exchange across the human forearm assessed by a combination of tracer and arteriovenous exchange techniques.

1. Whole-body kinetics and regional exchange of glycerol across forearm muscle were assessed in eight lean subjects by a combination of a tracer method (infusion of [2H5]glycerol) and arteriovenous catheterization. 2. During an apparent steady state, the enrichment of glycerol in deep venous blood from the muscle bed of the forearm was about half (4.40 +/- 1.72 atom per cent excess) that observed in arterialized blood (8.41 +/- 4.30 atom per cent excess). Under the same conditions, the circulating concentrations of glycerol in arterialized (91 +/- 24 mumol/l) and venous (87 +/- 32 mumol/l) blood were similar. 3. In a further group of 37 subjects it was found that about half had a positive arteriovenous concentration difference and the other had half a negative arteriovenous concentration difference (mean -1.6 +/- 11.9 mumol/l; range -25 to +22 mumol/l). 4. These results suggest: (a) that human muscle does not always release glycerol and may take it up; (b) that there is substantial isotopic exchange of glycerol across forearm muscle tissue, which is not reflected by the net exchange of glycerol; this could be due to slow equilibrium of enriched glycerol from the circulation, with unenriched free glycerol in the muscle pool, or due to the simultaneous metabolic utilization of enriched glycerol and metabolic production of unenriched glycerol; (c) that the estimation of glycerol flux rates is strongly dependent on whether the blood is arterialized or deep venous.

Adult↗

Carbohydrate metabolism in insulin resistance: glucose uptake and lactate production by adipose and forearm tissues in vivo before and after a mixed meal.

1. To examine whether insulin resistance in vivo is manifest equally in both muscle and adipose tissues, we measured arteriovenous glucose and lactate fluxes across forearm (muscle) and abdominal subcutaneous (adipose) tissue in nine obese, glucose-intolerant subjects and 13 non-obese subjects of similar age and sex. 2. Compared with non-obese subjects, the forearm of the obese subjects was resistant to insulin stimulation of glucose uptake after a mixed meal. In contrast, adipose tissue showed little evidence of insulin stimulation of glucose uptake, and adipose tissue in subjects in both normal and obese groups behaved very similarly (assessed per 100 g of tissue). 3. For lactate flux, adipose tissue behaved very similarly (per 100 g of tissue) in obese and non-obese subjects, and was a consistent lactate exporter. 4. We conclude that insulin resistance of glucose uptake observed in the forearm of obese subjects is not evident in adipose tissue. Adipose tissue glucose uptake in obese, insulin-resistant subjects is similar to that in lean control subjects, although it occurs at elevated circulating insulin and glucose concentrations.

Adipose Tissue↗