Blood flow determinations by venous occlusion plethysmography applying the strain-gauge technique are frequently used. A problem with the strain-gauge technique is that the relationship between venous volume and transmural pressure is not linear and, furthermore, changes with the sympathetic tone. The present study tests the hypothesis that these factors lead to a redistribution of venous blood, which may impair the accuracy of the technique. The relative volume expansion rates of four leg segments were studied with the leg in different positions and at disparate temperatures, thereby inducing varying venous pressures and sympathetic tone ( n =6). With elevated leg and relaxed veins (at 50 °C), the distal thigh showed a relatively low expansion rate (25.8±4.5 ml·min -1 ·l -1 ), whereas values in the calf segments were higher (34.5–39.0 ml·min -1 ·l -1 ). With lower initial transmural pressure, calf segments can increase their volume much more during occlusion compared with the distal thigh. In a higher transmural pressure region (lowered leg), the difference in compliance between limb segments is less. In this case, compliance and volume expansion rate was higher in the distal thigh (14.2, 13.5 and 22.2 ml·min -1 ·l -1 at 10, 20 and 50 °C respectively) than in the calf segments (for the distal calf: 6.4, 7.7 and 16.2 ml·min -1 ·l -1 respectively). There was a significant interaction ( P <0.001) between temperature and leg position, indicating a higher degree of sympathetic vasoactivity in the calf. It is concluded that blood flow determination by strain-gauge plethysmography is less accurate, due to a potential redistribution of the venous blood. Therefore possible influences of variations in sympathetic tone and venous pressure must be considered even in intra-individual comparisons, especially in interventional studies.

The human forearm model is used extensively in physiological, pharmacological and clinical investigations. Effects of arm dominance or arterial cannulation on forearm flow measurements have never been tested formally. In the present study we tested the hypotheses that left or right arm dominance or cannulation of the brachial artery do not affect forearm haemodynamic responses to physiological or pharmacological stimuli. Results obtained in 16 volunteers showed that forearm blood flow responses to physiological stimuli are comparable before and after intra-arterial cannulation in either the dominant or the non-dominant forearm. Cannulation of a forearm brachial artery has a small effect on baseline blood flow. Responses to intra-arterially infused noradrenaline (norepinephrine) were not influenced by left or right arm dominance. Intravenous infusion of noradrenaline in eight subjects resulted in small responses in forearm blood flow that were slightly asymmetrical. During the intravenous infusion of noradrenaline, forearm blood flow or the forearm blood flow ratio did not reflect the marked increase in FVR that occurred. These results support our hypotheses (a) that either arm can be used as the control or intervention arm, and (b) that intra-arterial cannulation does not affect the results of intra-arterial infusion studies.

1. The purpose of the study was to evaluate the degree of thrombus regression, development of valvular insufficiency, impaired calf muscle pump function and clinical symptoms after a period of acute deep venous thrombosis. 2. Seventy patients with acute deep venous thrombosis, diagnosed by duplex scanning or venography, received treatment with heparin and oral coumarin derivatives according to a standard protocol. All patients wore graduated compression stockings during the whole study period. Duplex scanning was performed at diagnosis and 1 and 3 months later to measure thrombus mass and reflux. The supine venous pump function test was used to assess calf muscle pump function. 3. Three months follow-up was completed in 60 patients. In total 218 (28%) out of 780 vein segments were initially thrombosed and 134 (17%) could not be traced. A statistically significant reduction of thrombus mass was recorded throughout the study period. Total resolution of thrombosis in all vein segments occurred in 25% of the patients within 1 month and in 40% in 3 months. There was no difference in regression between the various proximal vein segments. Distal segments showed more regression than proximal segments. Reflux occurred in 27% of the initially thrombosed veins and in 15% of the patent veins. Patients who showed total resolution after 1 month had a significantly higher calf muscle pump function than patients without total resolution (70% pf vs 61% pf , P < 0.05). Patients with reflux in two or more segments had a significantly lower calf muscle pump function than patients with reflux in less than two segments (58% pf vs 69% pf , P < 0.05). 4. Using duplex scanning and the supine venous pump function test 3 months after an acute deep venous thrombosis, overall haemodynamic abnormalities and local site of valve incompetence could readily be identified. Patients with haemodynamic abnormalities might be at risk to develop the post-thrombotic syndrome. There was no difference in thrombus regression between the various proximal vein segments. Reflux was significantly more often seen in initially thrombosed veins. Thirty-five percent of the patients developed an abnormal calf muscle pump function after 3 months. Patients with early resolution of thrombus had a higher calf muscle pump function after 3 months.

1. In contrast to the extensive documentation on diagnosis and treatment of deep venous thrombosis (DVT), information about long-term complications, clike the post-thrombotic syndrome (PTS), is scarce. Most studies report on clinical examination only, whereas adequate haemodynamic investigation is lacking. Therefore 81 patients with venographically confirmed lower extremity DVT were clinically and haemodynamically reexamined 7–13 years after DVT (mean 10 years) to assess PTS. Interest was focused on the relation between clinical and haemodynamic PTS and the relation between location of the initial DVT and incidence of PTS. 2. Clinical signs and symptoms of PTS were classified according to the latest consensus of the international consensus committee on chronic venous disease. Non-invasive venous vascular laboratory tests were performed to assess the venous outflow resistance and calf muscle pump function (CMP). CMP was determined by the supine venous pump function test (SVPT). 3. Clinically only 20 of 81 patients (25%) were asymptomatic, 34 (42%) had mild PTS (class 1–3), 25 (31%) moderate PTS (class 4) and 2 (2%) severe PTS (class 5–6); 57% had an abnormal CMP. Both the severity of clinical symptoms and the haemodynamic abnormalities were related to the location of the initial thrombus. Of the patients with distal DVT 11% developed moderate clinical PTS and 39% developed an abnormal CMP. CMP and difference in CMP between post-thrombotic and non-thrombotic leg were significantly related to the different classes of PTS. 4. This study indicates that 7–13 years after DVT 31% of the patients had moderate and 2% had severe clinical PTS, while 57% of the patients had abnormal haemodynamic findings (both related to the initial site of the thrombosis). Secondly, it reveals that the risk of PTS after distal DVT is not negligible, which causes concern about not diagnosing and treating patients with distal DVT. Thirdly, we have demonstrated that a functional test, such as the SVPT, is a sensitive test to assess post-thrombotic damage. Therefore its use as a screening tool after a period of DVT should be investigated to select patients at risk of PTS.

1. The aim of this study was to examine whether arginine vasopressin modulates the vasoconstricting action of phenylephrine in human forearms. 2. In seven healthy subjects, we determined the percentage increases in forearm vascular resistance evoked by intra-arterial infusion of phenylephrine at graded doses during simultaneous intra-arterial infusion of saline or arginine vasopressin at two doses. Similarly, in another seven subjects, we examined the effects of intra-arterial infusions of saline or angiotensin II on the vasoconstricting action of intra-arterial phenylephrine. 3. Arginine vasopressin and angiotensin II caused small, but insignificant, increases in baseline forearm vascular resistance. Arginine vasopressin at the two doses significantly attenuated the percentage increases in forearm vascular resistance evoked with phenylephrine at graded doses. Angiotensin II did not alter the forearm vascular responses to phenylephrine. 4. Intra-arterial infusion of arginine vasopressin at doses of 0.6 and 1.8 ng/min raised the plasma arginine vasopressin concentration in the venous effluents from 1.6 ± 0.3 (control) to 4.0 ± 0.9 and to 16.4 ± 6.9 pg/ml, respectively. 5. These results suggest that arginine vasopressin at physiological concentrations with a minimal direct effect on resistance arteries attenuates the vasoconstricting action of phenylephrine in human forearms.

1. In eight healthy volunteers we compared leg blood flow, as determined in a calf segment by strain-gauge plethysmography, with the flow measured by a constant-rate infusion of Indocyanine Green dye into the femoral artery. The representativeness of the calf segment was evaluated by complementary measurements with additional strain gauges attached around the proximal and distal crural and the distal thigh segments ( n = 6). Furthermore, we investigated the influence of the catheterization procedure and a simulated vascular puncture, as well as repeated venous occlusions, on blood flow and on arterial and femoral venous substrate concentrations and blood gases ( n = 8). 2. The leg blood flow measured by dye dilution was 0.31 ± 0.03 litre/min (mean ± sem). The blood flow in the calf segments was 14.8 ± 1.6 ml min −1 litre −1 and no difference between the legs was observed. Extended to the whole leg the plethysmographic blood flow was 0.17 ± 0.01 litre/min and thus lower (43 ± 7%, P < 0.001) than the flow determined by the indicator-dilution method. Blood flow in the legs was not influenced by catheterization or sham punctures of the vessels or by repeated venous occlusions. 3. The concentrations of glucose, lactate and glycerol, as well as blood gas variables, in arterial and femoral venous blood did not change during the study or decreased so slightly (pH and lactate) that the arteriovenous difference was not influenced. 4. We conclude that the blood flow of the total leg cannot be satisfactorily estimated from strain-gauge plethysmography of a single calf segment. Strain-gauge plethysmography can therefore not be recommended for quantitative studies of substrate turnover in the leg tissues applying the Fick principle. Catheterization of the femoral vessels, or manipulations close to them with a thin cannula or repeated venous occlusions, has no significant effect on leg blood flow and substrate exchange.