MHz Pulsed Doppler Probe Research Articles

Cerebral blood flow velocity and erythrocyte deformability in heavy alcohol drinkers at the acute stage and two weeks after withdrawal

Objective The aim of the study was to measure changes in blood flow velocity ( V mean) and erythrocyte deformability (ED) in heavy alcohol drinkers after withdrawal and the relationship between them. Methods The subjects were 32 heavy alcohol drinkers, mean age 47 years (22 men and 10 women). V mean was determined by a transcranial 2 MHz pulsed Doppler probe. ED was estimated by the method of cation-osmotic haemolysis (COH). The results were compared with those for 20 healthy volunteers. Results The study revealed a significant decrease in V mean and ED after admission. V mean in the left middle cerebral artery (MCA) was 45.1 ± 10.2 cm/s as compared with 59.1 ± 7.5 cm/s in controls; in the right MCA, it was 46.8 ± 11.3 cm/s as compared with 59.0 ± 7.6 cm/s in controls ( p < 0.001 in each case). But while V mean was significantly increased after 14 days withdrawal (54.4 ± 10.4 cm/s in the left MCA, p < 0.001, and 54.3 ± 12.1 cm/s in the right MCA, p < 0.01), ED showed only small change. A significant difference between V mean in men and women was found. Conclusion The changes in V mean after withdrawal are more influenced by plasma composition than by changes in ED.

Blood flow velocity, erythrocyte deformability and hepatic enzymes in heavy alcohol drinkers

Significantly decreased blood flow velocity in cerebral arteries, as well as decreased erythrocyte deformability, was found in heavy alcohol drinkers (Gdovinova 2002). The aim of this study was to determine if there is any correlation between the two. At the same time, the correlation between blood flow velocity and hepatic enzymes was also studied. The study group comprised 30 male patients, who were heavy alcohol drinkers, with a mean age of 46.4 years. Mean flow velocity (Vmean) was determined by a 2 MHz pulsed Doppler probe. Erythrocyte membrane biophysical properties were estimated by cation-osmotic haemolysis (COH). Hepatic enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyltransferase (GMT)] were measured in the Department of Biochemistry. The results were compared with the results from 20 healthy volunteers of the same age. Differences between the two groups were tested by Student’s t-test, and the relationship between blood flow velocity and COH, and of hepatic enzymes was analysed by regressive and correlative analysis. Results showed that Vmean was significantly decreased in heavy alcohol drinkers, in all cerebral arteries (the middle, anterior, and posterior cerebral arteries). No differences were noted between the left and right sides of the arteries tested. COH was similarly significantly decreased in heavy drinkers, in the medium of low (15.4 mmol/l NaCl) and high (123.2 mmol/l NaCl and above) ionic strength. Linear correlation between COH and Vmean was determined by correlative analysis, and a linear relationship was found. All hepatic enzymes (AST, ALT, GMT) were significantly increased in heavy drinkers. The relationship between Vmean and GMT was tested by the regressive analysis, and between these two parameters a linear relationship was found. It was concluded that changes in blood viscosity after the drinking of alcohol disturbs blood velocity and brain perfusion, which can be a major risk factor in strokes.

Do we need more technology to reduce recurrence of bleeding from ulcers?

Do we need more technology to reduce recurrence of bleeding from ulcers?

Continuous measurement of pulmonary blood flow using a retractable pulsed Doppler probe.

The feasibility of measuring pulmonary blood flow (PAQ) continuously using a removable, extraluminal 20 MHz pulsed Doppler probe, which has been used successfully to measure aortic blood flow, was assessed in seven anesthetized mongrel dogs. Simultaneous recordings were made from the Doppler probe (range-gated 5-6 mm from the anterior wall of the main pulmonary artery) and an electromagnetic flow probe (encircling the aorta) over cardiac outputs (CO) ranging from 0.2 to 5.5 L/min. Assuming a flat velocity profile and a fixed cross-sectional area, PAQ was initially calculated as the product of area and mean velocity. Regression analyses (PAQ = a + b X CO) indicated good intraanimal linear correlations in six animals (r greater than or equal to 0.84) and no correlation in one animal (r = 0.003); however, PAQ was consistently higher than CO and interanimal variability was marked, as suggested by large deviations in mean intercept and slope values (a = 1.67 +/- 1.09 L/min and b = 0.70 +/- 0.33). Results improved (r greater than or equal to 0.79 in all animals, a = 0.47 +/- 0.52 L/min, and b = 0.77 +/- 0.21) when the method to estimate PAQ was altered to assume that the starting cross-sectional area was the area that would make baseline PAQ and CO agree, and that the area during each subsequent CO level changed as a function of pulmonary artery pressure and an estimate of pulmonary artery compliance. Results of this study imply that it will be more difficult to use this Doppler probe to monitor CO from the pulmonary artery than it was from the aorta due to the elliptical, more compliant pulmonary vessel walls and the irregular pulmonary artery velocity profile.

Intraoperative assessment of carotid endarterectomy

The use of operative arteriography during carotid endarterectomy facilitates identification and correction of technical errors. Although arteriography is the standard for assessing surgical results, it prolongs the operation and may increase the overall risk. The purpose of this study was to evaluate pulsed Doppler spectral analysis and arteriography as methods of intraoperative assessment. Operative arteriography was performed in 150 consecutive carotid endarterectomies. In 50 of these cases a sterile 20 MHz pulsed Doppler probe and real-time spectrum analyzer were used to evaluate internal carotid velocity patterns before and after endarterectomy. Operative arteriograms were normal in 127 cases, whereas abnormalities were noted in 16 internal and seven external carotid arteries. Thirteen of the arteriographic defects were considered minor and accepted. Major defects requiring immediate repair occurred in eight (5%) internal and two external carotid arteries. In the 50 cases assessed by both techniques, seven internal carotid arteries had mild flow disturbances both before and after endarterectomy, whereas 38 of the remaining 43 arteries showed improvement in spectral characteristics after endarterectomy. In two patients who failed to show improvement on the initial postendarterectomy evaluation, operative arteriography demonstrated residual defects that required immediate repair. No other technical errors were encountered, and there were no perioperative deaths or neurologic complications in the 150 operations. Intraoperative assessment by pulsed Doppler spectral analysis is a safe, rapid, and accurate method for detecting technical errors during carotid endarterectomy. The high sensitivity of this method (no false negative assessments) makes it an ideal screening test to be used for selection of patients for operative arteriography. By indicating when a technical error is most likely, this approach precludes the need for routine operative arteriography.