Carotid artery blood flow and middle cerebral artery blood flow velocity during physical exercise.

Factors controlling cerebral blood flow (CBF) during exercise are complex and incompletely known. Different techniques have shown partly contradictory results of changes in regional and global cerebral perfusion during dynamic exercise in healthy subjects. To elucidate the global CBF response to supine stepwise increasing physical exercise, we measured blood flow in the left common carotid artery (QCCA) and the left internal carotid artery (QICA) simultaneously with the blood flow velocity in the ipsilateral middle cerebral artery (VMCA) using duplex ultrasonography and transcranial Doppler ultrasonography. During moderate exercise intensity (60-67% of maximal capacity), the VMCA increased 14% (P < 0.001), the QICA 17% (P < 0.01), and the QCCA 33% (P < 0.001) compared with baseline values. High physical exercise intensity (80-90% of maximal capacity) tended to reduce VMCA and QICA compared with moderate exercise, in contrast to a continued increase in QCCA. The results indicate an increased global CBF during exercise. This increase was reduced during hard exercise due to a decrease of the arterial PCO2 secondary to hyperventilation.

The effect of erythropoietin treatment on arteriovenous haemodialysis fistula/graft: a prospective study with colour flow Doppler ultrasonography.

To determine the effect of erythropoietin (EPO) on patency the haemodynamics and morphology in haemodialysis fistula/graft were prospectively assessed using ultrasonographic two-dimensional imaging and colour flow Doppler together with pulsed Doppler, prior to and during partial correction of anaemia with EPO. Nineteen radiocephalic fistula and 11 loop grafts in 30 patients on routine maintenance haemodialysis were investigated prior to EPO treatment. A significant stenosis defined as a localised 100% increase in flow velocity was found in the arterial inflow in seven (23%) patients, in the loop graft in seven (64% of loop grafts) patients, and in the venous segments in 23 (77%) patients. Fourteen patients were rescanned after more than 200 days of EPO therapy. There was a significant increase in haemoglobin (84 +/- 14 g/l to 104 +/- 18 g/l) and haematocrit (24 +/- 4 to 31 +/- 5%) during this time. One arterial, four loop grafts and two venous stenoses appeared or increased in severity, and one venous return flow segment had occluded. Blood flow according to ultrasonography was unchanged. Of the 16 patients lost to follow-up, three underwent surgical intervention (clinical failure rate 0.20 access/year). EPO therapy may contribute to minor changes in access haemodynamics but does not seem to be detrimental to patency.

The "ad hoc" estimation of outflow does not predict patency of infrainguinal reconstructions.

OBJECTIVES: This prospective study was performed to evaluate the clinical implication of the adhoc estimation (also called SVS score) of outflow on patency of infrainguinal in situ femoropopliteal or -distal bypasses. METHODS: The bypasses were followed with Duplex scanning at 1, 3, 6, and 12 months after surgery. Fifty-three bypasses were recruited for the study, 20 of which were performed in 17 diabetics. In 47% the adhoc scoring was < or = 4.5 and in 53% it was between 5 and 10 (1 corresponds to an excellent outflow and 10 to a blind segment). RESULTS: Within the first 30 days eight occlusions occurred, all of which were surgically corrected. The adhoc score for these bypasses was 4.2 vs. 4.9 (NS) for those who did not occlude. During follow-up, revisions were performed in 21 cases (40%) with 30 interventions. At the end of 1 year, 68% of the bypasses were patent (80% among diabetics and 64% among non-diabetics, NS). Patency at 1 year was not influenced by the adhoc classification. CONCLUSION: The estimation of outflow from angiography seems to be of no value in predicting graft patency in infrainguinal grafting.