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PubMed2003

Neurovascular dissociation with paradoxical forearm vasodilation during systemic tyramine administration.

BACKGROUND: Despite the widespread use of tyramine as a pharmacological tool to assess the effects of norepinephrine release from sympathetic nerve terminals, its vascular effects are not adequately characterized. In particular, previous results indicate that intravenous tyramine produces little if any systemic vasoconstriction, suggesting that tyramine does not cause significant norepinephrine release from sympathetic nerves innervating peripheral vascular beds. To test this hypothesis, we determined the effects of intravenous tyramine on local forearm norepinephrine spillover and vascular resistance. METHODS AND RESULTS: Seven healthy subjects were studied with systemic and local forearm norepinephrine spillover and forearm blood flow at baseline, during systemic tyramine infusion, and after sympathetic stimulation induced by the cold pressor test. Tyramine infusion caused a significant increase in systemic and forearm norepinephrine spillover. The amount of norepinephrine released into the forearm by tyramine was similar to that caused by cold pressor stimulation, 0.15+/-0.05 versus 0.18+/-0.05 ng x dL(-1) x min(-1). As expected, forearm vascular resistance increased during the cold pressor test, but tyramine produced forearm vasodilation (4.5+/-1 versus -5+/-1 mm Hg x dL(-1) x min(-1), P<0.03) despite the increase in local norepinephrine spillover. In 6 additional subjects, plasma dopamine increased significantly during tyramine administration, from 11+/-3 to 662+/-105 pg/mL. CONCLUSIONS: Thus, systemic tyramine infusion evokes a significant increase in peripheral norepinephrine spillover, and this, paradoxically, is associated with local vasodilatation rather than vasoconstriction.

Adult↗
PubMed2000

Sympathetic denervation of the upper limb improves forearm exercise performance and skeletal muscle bioenergetics.

BACKGROUND: Sympathetic activation may limit exercise performance by restraining muscle blood flow or by negatively affecting skeletal muscle metabolic behavior. To test this hypothesis, we studied the effect of thoracoscopic sympathetic trunkotomy (TST) on forearm exercise duration, blood flow, and muscle bioenergetics in 13 patients with idiopathic palmar hyperhidrosis. METHODS AND RESULTS: Heart rate and beat-by-beat mean arterial pressure were recorded at rest and during right and left rhythmic handgrip before and 4 to 7 weeks after right TST. Forearm blood flow was measured bilaterally at rest and on the right during exercise. Right forearm muscle phosphocreatine content and intracellular pH were assessed by (31)phosphorus magnetic resonance spectroscopy. After right TST, exercise duration increased from 8.9+/-1.4 to 13.4+/-1.8 minutes (P<0.0001) with the right forearm and from 5.7+/-0.4 to 7.6+/-0.9 minutes (P<0.05) with the left (P<0.05 for the interaction between treatment and side). Right forearm blood flow at rest was 66% higher (P<0.01) after right TST, but this difference decreased as the exercise progressed. After right TST, a significant reduction occurred in muscle acidification and phosphocreatine depletion during ipsilateral forearm exercise. This was associated with a significantly reduced mean arterial pressure response to right handgrip, whereas the pressor response to left handgrip did not change. CONCLUSIONS: Sympathetic denervation of the upper limb significantly improves forearm skeletal muscle bioenergetics and exercise performance in patients with idiopathic palmar hyperhidrosis.

Adult↗
PubMed1995

Abnormal forearm vascular responses during dynamic leg exercise in patients with vasovagal syncope.

BACKGROUND: We have reported previously that in some patients with normal hearts who present with exercise syncope, abnormal forearm vasodilation is seen during leg exercise and tilt table tests are positive. This suggests that exercise syncope may be a variant of vasovagal syncope. In this study we tested the hypothesis that there is loss of the normal forearm vasoconstrictor response during dynamic leg exercise in an unselected population of patients with classic vasovagal syncope. METHODS AND RESULTS: We evaluated forearm vascular responses during maximal semierect cycle exercise in 28 consecutive patients with vasovagal syncope and compared them with 30 age-matched control subjects. We also evaluated blood pressure responses during erect treadmill exercise (Bruce protocol). While forearm vascular resistance at rest was similar in the patients with vasovagal syncope and the control group, forearm vascular resistance was markedly lower in the patients than in control subjects at peak exercise (85 +/- 54 versus 149 +/- 94 units, P = .002). Forearm vascular resistance fell by 3 +/- 48% during exercise in patients versus an increase of 135 +/- 103% in control subjects (P < .0001). Systolic blood pressure during erect exercise was lower in patients versus control subjects (155 +/- 32 versus 188 +/- 17 mm Hg, P < .0001). Six of the vasovagal patients complained of exercise syncope or presyncope on specific inquiry, and 4 of these 6 exhibited exercise hypotension during erect treadmill exercise testing. CONCLUSIONS: Patients with vasovagal syncope exhibit a failure of the normal vasoconstrictor response in the forearm during dynamic leg exercise. Exercise syncope and presyncope are not uncommon in unselected patients with classic vasovagal syncope, as is exercise hypotension.

Adult↗
PubMed1991

Attenuated forearm vasodilator response to atrial natriuretic factor in the elderly.

The vasodilator potency of human atrial natriuretic factor-(99-126) was investigated in the forearm vascular bed of 10 young and 10 elderly normotensive volunteers with venous occlusion strain gauge plethysmography. Atrial natriuretic factor was infused at six increasing dose steps into the brachial artery from 0.001 up to 0.3 microgram/min/100 ml of forearm volume. This induced a mean +/- SEM increase in blood flow from 1.4 +/- 0.2 up to 6.0 +/- 1.0 ml/min/100 ml in the young and from 1.4 +/- 0.2 up to 3.9 +/- 0.6 ml/min/100 ml in the elderly. The dose-response curves of forearm blood flow and of forearm vascular resistance after increasing infusion rates of atrial natriuretic factor were shifted to the right in the elderly when compared with the young subjects. The mean percent decrease in forearm vascular resistance, induced by atrial natriuretic factor, during this dose-response curve averaged -31 +/- 3% in the elderly versus -56 +/- 3% in the young subjects (p = 0.0002). The calculated forearm spillover of the second messenger of atrial natriuretic factor, cyclic guanosine monophosphate, significantly increased from baseline values of 1.2 +/- 1.1 and 0.7 +/- 0.5 pmol/min/100 ml in young and elderly subjects, respectively, up to 23.2 +/- 5.0 and 30.5 +/- 7.0 pmol/min/100 ml during the highest dose of atrial natriuretic factor (both p less than 0.01 versus baseline). There were no significant differences in the increments of the forearm spillover of this second messenger between both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Effects of L-arginine on forearm vessels and responses to acetylcholine.

This study was designed to investigate the effects of L-arginine (the substrate of endothelium-derived nitric oxide) in human forearm vessels. We examined whether intra-arterial infusion of L-arginine dilated forearm vessels and augmented vasodilatory responses to acetylcholine in young, healthy humans. The left brachial artery was cannulated for drug infusions and direct measurement of arterial pressure. Forearm blood flow was measured by a strain gauge plethysmograph. Intra-arterial infusions of L-arginine at 10, 20, 40, and 60 mg/min increased forearm blood flow from 4.7 +/- 0.6 to 4.9 +/- 0.5, 5.7 +/- 0.5, 7.2 +/- 0.8, and 8.2 +/- 0.9 ml.min-1.100 ml-1, respectively (n = 8, p less than 0.01), whereas D-arginine at the same doses did not alter forearm blood flow (n = 7). Intra-arterial infusions of acetylcholine (n = 7) (4, 8, 16, and 24 micrograms/min) and sodium nitroprusside (n = 5) (0.2, 0.4, 0.8, and 1.2 micrograms/min) increased forearm blood flow dose dependently (p less than 0.01 for both). Arterial pressure was not altered with infusions of these drugs. Responses to acetylcholine were augmented with simultaneous intra-arterial infusion of L-arginine at 10 mg/ml (p less than 0.01) but not with D-arginine. Responses to sodium nitroprusside were not altered by L-arginine. These results in human forearm resistance vessels support the notion that vasodilation induced by acetylcholine is a result of the conversion from L-arginine to endothelium-derived nitric oxide.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Forearm blood flow reserve and cardiac and renal indexes of pressure load in normotensive and hypertensive individuals.

In response to hypertension, arterioles remodel their structure, the heart develops myocardial hypertrophy, and the kidney reduces creatinine clearance and increases albuminuria. To better understand the interrelations among the target organs involved in hypertension, we evaluated minimal forearm vascular resistances--a hemodynamic index of arteriolar structure derived from mean blood pressure and maximal postischemic forearm blood flow--the echocardiographic indexes of cardiac structure, and urinary albumin excretion and creatinine clearance in 29 male mild to moderate non-macroalbuminuric essential hypertensive patients on no drugs and 11 age- and sex-matched normotensive control subjects. Minimal forearm resistances were elevated in hypertensive patients and correlated with left ventricular mass, wall thickness, and mean arterial pressure. Patients with abnormal minimal forearm resistances (2 SD above normal) were characterized by higher pressure, greater wall thickness, lower creatinine clearance, and higher albumin excretion, suggesting that maximal forearm flow capacity does relate to the hemodynamic load exerted on both the kidney and heart. However, the correlation with cardiac structure and mean arterial pressure explained only part of the variability of minimal forearm resistances. Furthermore, no correlation among these parameters was found when hypertensive patients were evaluated separately from normotensive subjects, possibly because of heterogeneous factors active on arteriolar structure and unrelated to the pressor load. Overall, the data suggest that the development of abnormal minimal forearm resistances in the course of the hypertensive process is related to the pressor load, but its details need further understanding.

Adult↗
PubMed1995

Insulin and forearm vasodilation in hypertension-prone men.

Insulin-stimulated peripheral glucose uptake and insulin-mediated forearm vasodilation were investigated in 38 normotensive men with a family history of hypertension (relatives) compared with 27 age- and body mass index-matched normotensive men with no family history of hypertension (control subjects). The euglycemic hyperinsulinemic clamp technique was used to measure peripheral glucose uptake (insulin sensitivity index) and the metabolic clearance rate of insulin. Intra-arterial blood pressure and forearm blood flow were determined simultaneously, and forearm vascular resistance was calculated. The insulin sensitivity index was lower in relatives than in control subjects. The metabolic clearance rate of insulin was reduced and did not correlate to glucose disposal in the relatives as opposed to the control subjects. Forearm blood flow increased and forearm vascular resistance decreased to a similar extent in the two groups during the clamp. The vasodilator response was positively correlated to glucose disposal only in the relatives. In conclusion, impaired insulin-stimulated peripheral glucose uptake in normotensive sons from hypertensive families was accompanied by retained insulin-mediated forearm vasodilation. Thus, skeletal muscle blood flow supply does not seem to be the major determinant for glucose disposal. On the other hand, the positive correlation between glucose disposal and decrease in forearm vascular resistance in the relatives suggests that insulin-mediated vasodilation may be a limiting factor for peripheral glucose uptake in insulin-resistant individuals.

Disease Susceptibility↗
PubMed1987

Demonstration of neuronal and extraneuronal uptake of circulating norepinephrine in the forearm.

Disturbances in peripheral norepinephrine release or removal by neuronal and extraneuronal uptake may have pathogenetic significance in cardiovascular disease states. We investigated the mechanisms of removal of norepinephrine in the forearm of healthy subjects under basal conditions, using measurements of arterial and venous plasma norepinephrine concentrations, blood pressure, heart rate, and forearm blood flow. The specific inhibitor of neuronal uptake, desipramine, was infused intra-arterially into the brachial artery of five subjects. Net norepinephrine overflow from the forearm increased markedly, revealing considerable local release of norepinephrine. Six other subjects received four intra-arterial infusions of norepinephrine, 1.18 pmol/kg/min, with various doses of desipramine and the extraneuronal uptake-inhibiting drug hydrocortisone. The forearm extraction rate for circulating norepinephrine decreased with increasing doses of desipramine (from 69.4 +/- 3.0 [SEM] to 35.3 +/- 8.4%; p less than 0.001). Increasing doses of hydrocortisone during continued inhibition of neuronal uptake resulted in decreased forearm extraction of norepinephrine (from 63.3 +/- 4.9 to 40.6 +/- 4.4%; p less than 0.01). In six other subjects who received the highest dose of hydrocortisone without concomitant inhibition of neuronal uptake, forearm extraction of norepinephrine decreased from 57.1 +/- 4.9 to 51.5 +/- 4.7% (p less than 0.05). These results suggest that neuronal uptake contributes markedly to the removal of circulating and endogenously released norepinephrine in the forearm. For circulating norepinephrine, a corticosteroid-sensitive mechanism of extraneuronal uptake was also demonstrated. These results indicate that neuronal and extraneuronal uptake can be estimated separately in this vascular bed. Similar organ-specific studies in patients may reveal disturbances in mechanisms of norepinephrine removal.

Adult↗
PubMed1991

Evidence for functional alpha 2-adrenoceptors on vascular sympathetic nerve endings in the human forearm.

The role of alpha 2-adrenoceptors on vascular sympathetic nerve endings in modulating release of the sympathetic neurotransmitter norepinephrine (NE) in humans was examined by measuring the regional rate of appearance of NE in forearm venous plasma (forearm NE spillover [FSO]) in 32 healthy volunteers during intra-arterial infusion of drugs acting at adrenoceptors or directly on vascular smooth muscle. Simultaneous intra-arterial infusions of tracer amounts of [3H]NE were used to calculate the extraction rate of NE in the forearm. Methoxamine or propranolol with epinephrine (PRO + EPI) was used to stimulate alpha-adrenoceptors, yohimbine was used to inhibit alpha-adrenoceptors, and sodium nitroprusside (NIP) was used to produce increases in forearm blood flow directly. Sympathetic efferent activity was manipulated by systemic intravenous infusions of NIP or trimethaphan. Yohimbine and NIP increased and PRO + EPI and methoxamine decreased NE FSO, without effects on systemic blood pressure, heart rate, or arterial levels of catechols. Changes in FSO were flow dependent; therefore, the slope of the relation between the changes in FSO and forearm blood flow was used to evaluate the effects of each drug on regional sympathoneural activity. During administration of yohimbine, the mean slope of the relation between the change in estimated FSO and the change in forearm blood flow was about four times that of the mean slope during administration of NIP (F = 6.35, p less than 0.05). The slopes of the relations between changes in FSO and forearm blood flow were unaffected by systemic trimethaphan or NIP infusion, indicating that the activity of alpha 2-adrenoceptors was not altered during inhibition or reflexive stimulation of sympathetic outflow. The results suggest that alpha 2-adrenoceptors modulate release of NE from vascular sympathetic nerve endings in humans and that the function of these receptors is unchanged during acute changes in junctional NE concentrations.

Adult↗
PubMed1981

Leucine meal increases glutamine and total nitrogen release from forearm muscle.

To assess the consequences of elevated branched chain amino acid levels on alanine, glutamine, and ammonia metabolism in muscle, L-leucine meals (14.7 g) were consumed by six normal postabsorptive individuals. Bilateral forearm studies were performed, and the dominant arm was subjected to 15 min of light exercise, using a calibrated dynamometer, beginning 45 min after the ingestion of the meal. Large uptakes of leucine were seen across both forearm muscle beds within 30 min of the meal. After exercise, blood flow in the dominant arm increased from 3.1 +/- 0.4 to 5.2 +/- 0.9 ml/100 ml forearm per minute (mean +/- SEM, P less than 0.005). Glutamine flux out of the dominant forearm increased threefold after the ingestion of the leucine meal and increased eightfold over base line after exercise. Less marked changes (significant only at 90 min) in the nonexercised, nondominant arm were also seen. Alanine flux out of the dominant forearm muscle bed increased modestly at 75 and 90 min. No significant change in ammonia flux across either forearm muscle bed was noted. Unexpectedly, large and significant net nitrogen loss from both forearm muscle beds was documented. Thus, following the ingestion of a leucine meal and light exercise, the primary means by which excess nitrogen is routed out of muscle is via glutamine formation and release with alanine and ammonia pathways playing relatively minor roles. More importantly, the ingestion of significant amounts of leucine by normal subjects, presumably in optimal nitrogen balance, results in a net loss of nitrogen from muscle.

Adult↗
PubMed2003

Deterioration of muscle function after 21-day forearm immobilization.

PURPOSE: Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function. METHODS: Six healthy males (age: 21.5 +/- 1.4, mean +/- SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization. RESULTS: After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST. CONCLUSION: In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.

Adult↗
PubMed1992

Measurement of forearm bone mineral density in normal women by dual-energy X-ray absorptiometry.

We report the results of forearm measurements, without the use of a water bath, using dual-energy X-ray absorptiometry (DEXA) in 100 normal women aged 29-69 years (average age, 52 years). Studies were performed using the Hologic QDR-1000, with bone mineral density (BMD) measured at three sites in the non-dominant forearm: ultradistal, distal one-third and a region between these two. The precision of the technique was 0.74%, 0.55% and 0.58%, respectively. The normal range for forearm BMD and variation with age was established. BMD was also measured in the lumbar spine (L1-L4) and femoral neck. Linear regression analysis gave a range of correlation coefficients between forearm and axial sites of r = 0.49-0.67. Standard errors of the estimate (SEE) in predicting axial from peripheral measurements gave average values from the three forearm sites of 0.085 g/cm2 for the femoral neck and 0.118 g/cm2 for the spine. Forearm measurements using DEXA can now be reliably performed in air. DEXA produces a high-resolution image, is fast and simple to perform, and enables both cortical and trabecular sites to be examined in one measurement. Forearm and axial measurements can be performed using the same equipment, where centres possess a suitable DEXA system.

Absorptiometry, Photon↗
PubMed1995

Effects of intra-arterial infusion of insulin on forearm vasoreactivity in hypertensive humans.

We previously demonstrated that intra-arterial infusion of insulin attenuates vasoreactivity to phenylephrine and angiotensin II in the forearm of normotensive humans, which suggests that the pressor effects of insulin via sympathetic activation may be offset in peripheral arteries. In the present study, we investigated the effects of insulin on vasoreactivity in hypertensive humans. Seven male patients with essential hypertension (age, 26 +/- 2 yr; blood pressure, 159 +/- 4/103 +/- 4 mmHg; mean +/- SEM) were studied. We measured forearm blood flow by a strain gauge plethysmograph while infusing phenylephrine (1, 4, 12 nmol/min) and angiotensin II (5, 10, 20 pmol/min) locally into the brachial artery before and during simultaneous intra-arterial infusion of human insulin (0.15 mU/kg/min). Forearm vascular resistance was calculated from directly measured arterial pressure and forearm blood flow. Intra-arterial infusion of insulin raised the local plasma insulin level without changing the blood glucose level, basal forearm blood flow, or forearm vascular resistance. Phenylephrine and angiotensin II increased forearm vascular resistance dose-dependently before and during insulin infusion. In contrast to the previous results in normotensive subjects, locally infused insulin did not attenuate vasoconstrictive responses to phenylephrine and angiotensin II in patients with essential hypertension. These results suggest that the balance between the pressor and depressor effects of insulin might be altered in favor of a pressor effect in patients with hypertension.

Blood Glucose↗
PubMed2006

Effect of wrist and forearm training on linear bat-end, center of percussion, and hand velocities and on time to ball contact of high school baseball players.

This study examined the effects of 12 weeks of wrist and forearm training on linear bat-end velocity (BV), center of percussion velocity (CV), hand velocity (HV), and time to ball contact of high school baseball players. Forty-three baseball players were randomly assigned by a stratified sampling technique to 1 of 2 training groups. Group 1 (n = 23) and group 2 (n = 20) performed the same full-body resistance exercises while training 3 days a week for 12 weeks according to a stepwise periodized model. Group 2 also performed wrist and forearm exercises 3 days a week for 12 weeks. Wrist and forearm strength were measured pre- and posttraining. Linear BV, CV, HV, and time to ball contact were recorded pre- and posttraining by a motion-capture system. A 3 repetition maximum (RM) parallel squat and bench press were measured at baseline and after 4, 8, and 12 weeks of training. Both groups showed statistically significant increases (p < or = 0.01) in linear BV, CV, and HV (m.s(-1) +/- SD) after 12 weeks of training; however, there were no differences between the 2 groups. Both groups statistically increased wrist and forearm strength (p < or = 0.05). Group 2 had statistically greater increases (p < or = 0.05) in 10 of 12 wrist and forearm strength measures than did group 1. Both groups made statistically significant increases in predicted 1RM parallel squat and bench press after 4, 8, and 12 weeks of training; however, there were no differences between groups. These data indicate that a 12-week stepwise periodized training program can significantly increase wrist and forearm strength, linear BV, CV, and HV among high school baseball players. However, increased wrist and forearm strength did not contribute to further increases in linear BV, CV, or HV.

Adolescent↗
PubMed1997

An analysis of the effects of nitroglycerin on forearm circumference, with simultaneous recordings of arterial and venous diameters and blood pressure.

The aim of this study is to define the effect of sublingually administered nitroglycerin (NTG) on the diameters of the forearm arteries and veins as well as to define the relationship between these vascular changes and the forearm circumference in healthy volunteers. For this purpose, we employed a noninvasive method permitting the simultaneous quantitative recording of vascular diameters, forearm circumference and blood pressure using a miniature load cell, linear differential transformers and mercury-in-rubber strain gauge. Sublingually administered NTG (0.3 mg) increased the radial arterial diameter and the forearm circumference, whereas the cephalic vein capacitance was decreased; consequently, the cephalic vein acts to moderate the increase in forearm circumference. The results clearly indicate that nitroglycerin dilates forearm arteries but not forearm veins in the normal state.

Adult↗
PubMed1998

Radioulnar load-sharing in the forearm. A study in cadavera.

Custom-designed miniature load-cells were inserted into the distal end of the ulna and the proximal end of the radius in ten fresh-frozen forearms from cadavera. The forces transmitted through the bones at these sites were measured under 134 newtons of constant axial load that was applied through the metacarpals as the forearm was rotated from 60 degrees of supination to 60 degrees of pronation. The simultaneous measurements of these forces allowed the calculation of radioulnar load-sharing at the wrist and the elbow as well as the calculation of the amount of force that was transferred from the radius to the ulna through the interosseous membrane. With the elbow in valgus alignment (that is, with contact between the radial head and the capitellum), the main pathway for load transmission through the forearm was direct axial loading of the radius; measurements from both load-cells were unaffected by the angle of elbow flexion. When the forearm was in neutral rotation, the mean force in the distal end of the ulna averaged 2.8 per cent of the load applied to the wrist and the mean force in the proximal end of the ulna averaged 11.8 per cent; this indicated that only a small amount of tension developed in the interosseous membrane. With the elbow in varus alignment (that is, with no contact between the radial head and the capitellum), load was transmitted through the forearm by a transfer of force from the radius to the ulna through the interosseous membrane. When the forearm was in neutral rotation, the force in the distal end of the ulna averaged 7.0 per cent of the load applied to the wrist and the force in the proximal end of the ulna averaged 93.0 per cent; the force through the interosseous membrane decreased with supination of the forearm. Testing with the elbow in valgus alignment and shortening of the distal end of the radius in two-millimeter increments produced corresponding increases in force in the distal end of the ulna and decreases in force in the radial head. The forces through the interosseous membrane remained low after each amount of radial shortening.

Aged↗
PubMed2002

Utility of ultrasonographic venous assessment prior to forearm arteriovenous fistula creation.

AIM: The purpose of this study was to evaluate the clinical utility of Doppler ultrasound (US) prior to native forearm arteriovenous fistula (AVF) creation. MATERIALS AND METHODS: US mapping was carried out pre-operatively to evaluate the major veins and arteries in the appropriate arm. One hundred and 6 patients were identified retrospectively over 2 years with complete clinical and US data. A failed fistula was defined as an inability to provide blood flow to meet adequacy targets by 6 months (urea reduction ratio > or = 65%). RESULTS: Twenty-nine patients (27.4%) had successful forearm AVFs. The mean minimum forearm cephalic vein diameter (CVD) was 2.51 +/- 0.14 and 2.23 +/- 0.06 mm in successful and failed fistulae, respectively (p = 0.04). This result was primarily due to differences observed in women. A receiver operator curve analysis showed that a cutpoint of 2.6 mm for minimum forearm CVD had the greatest predictive value with a likelihood ratio of 3.94 (95% CI: 1.97 - 7.84) for fistula failure. Multivariate logistic regression analysis determined that male gender and minimum forearm CVD were the only significant predictors for fistula success with odds ratios of 3.90 (95% CI: 1.30 - 11.68) and 2.31 (95% CI: 1.00 - 5.43), respectively. The study is limited by the possibility that US results in patients may have lead to an alternative type of access being attempted. CONCLUSIONS: US mapping prior to forearm AVF creation is of modest benefit. Only male gender and minimum forearm CVD were predictive of AVF success.

Adult↗
PubMed2006

Cephalic vein measurement before forearm fistula creation: does use of a tourniquet to meet the venous diameter threshold increase the number of usable fistulas?

OBJECTIVE: To optimize forearm radiocephalic fistula success, many programs recommend a minimal cephalic vein diameter of 0.25 cm or greater on preoperative sonographic mapping. It is not established, however, whether a vein diameter before or after application of a tourniquet should be used in determining suitability for creation of a forearm fistula. METHODS: Before forearm radiocephalic fistula placement, preoperative sonographic mapping measured the cephalic vein diameter before and after application of a tourniquet. The patients fell into 2 groups: those with a pretourniquet vein diameter of 0.25 cm or greater (group 1) and those with a pretourniquet vein diameter of less than 0.25 cm that increased to 0.25 cm or greater after application of the tourniquet (group 2). The adequacy of each fistula for dialysis was determined clinically. RESULTS: Among 73 radiocephalic fistulas with known clinical outcomes, 28 were in group 1, and 45 were in group 2, on the basis of sonography. Fistula success rates were similar in group 1 patients (11 [39%] of 28) and group 2 patients (15 [33%] of 45) (P=.624, Fisher exact test). Inclusion of group 2 patients increased the number of patients recommended for placement of forearm fistulas and increased the total number of usable forearm fistulas from 11 to 26. The overall success rate of forearm fistulas was lower in women (19% versus 50%; P=.015, Fisher exact test). CONCLUSIONS: The use of a venous tourniquet increases the number of patients eligible for forearm fistulas without decreasing the adequacy rate of these fistulas. Therefore, a tourniquet should routinely be used in patients with small cephalic veins on pretourniquet evaluation.

Arteriovenous Shunt, Surgical↗