[Duplex sonography: accuracy, reproducibility and possibilities for error. Checking quantitative flow measurements against an in vitro model]

Aortic Peak Flow Velocity As a Predictor of Fluid Responsiveness in Mechanically Ventilated Children: A Systematic Review and Meta-Analysis

OBJECTIVES

This meta-analysis aimed to determine the accuracy of the respiratory variations in aortic peak flow velocity (delta Vpeak) in predicting fluid responsiveness and the moderators of that accuracy.

DATA SOURCES

We performed searches for studies that used delta Vpeak as a predictor of fluid responsiveness in mechanically ventilated children in PubMed, Embase, Scopus, and CINAHL from inception to June 20, 2022.

STUDY SELECTION AND DATA EXTRACTION

Fifteen studies ( n = 452) were included in this meta-analysis. The diagnostic test data of the included studies were synthesized as pooled sensitivity, specificity, and diagnostic odds ratio (DOR) and the area under the curve (AUC) of the summary receiver operating characteristic of delta Vpeak.

DATA SYNTHESIS

The delta Vpeak cutoff values applied in these studies had a median of 12.3% (interquartile range, 11.50-13.25%). The pooled sensitivity and specificity of delta Vpeak were 0.80 (95% CI, 0.71-0.87) and 0.82 (95% CI, 0.75-0.87), respectively. The DOR of delta Vpeak was 23.41 (95% CI, 11.61-47.20). The AUC of delta Vpeak was 0.87. Subgroup analyses revealed that the accuracy of delta Vpeak was not moderated by ventilator settings, measures of delta Vpeak, gold standard index, the cutoff gold standard value of responders, type and volume of fluid, duration of fluid challenge, use of vasoactive drugs, general anesthesia, and cardiopulmonary bypass.

CONCLUSIONS

By using the cutoff of approximately 12.3%, the delta Vpeak appears to have good accuracy in predicting fluid responsiveness in mechanically ventilated children. The moderators of delta Vpeak predictability are not found.

B-mode and colour Doppler ultrasonography of the milk vein in 29 healthy Swiss braunvieh cows

The morphology and diameter of the milk vein of 29 healthy Swiss braunvieh cows and the velocity of blood flow through it was measured by colour Doppler ultrasonography before and 10 minutes after they had been sedated with 0.03 mg/kg xylazine. The milk vein was situated immediately under the skin. It had a diameter of 0.8 to 1.6 cm and valves were visible in the milk vein of 12 of the cows. The spectral display appeared as a broad band structure with a wave-like course. The Doppler measurement point was 0.4 to 0.8 cm from the body surface. The diameter of the vein and the blood flow velocity did not differ significantly before and after the cows were sedated. The mean (sd) diameter of the milk vein before they were sedated was 1.3 (0.3) cm. The mean maximum blood flow velocity before they were sedated was 45.4 (12.5) cm/second, the mean velocity was 33.5 (9.5) cm/second, and the mean minimum was 25.8 (11.6) cm/second. There were significant correlations between the blood flow velocities before and after the cows were sedated and between individual cow's blood flow velocities, with correlation coefficients ranging from 0.69 to 0.94.

Colour-Doppler sonography of the musculophrenic vein in cows

The goal of the present study was to examine the musculophrenic vein of 29 healthy Swiss Braunvieh cows using colour-Doppler sonography to determine vessel morphology and diameter, and blood flow velocity. The hair over the reticular region was clipped, and the left musculophrenic vein was examined before and 10min after sedation using 0.03mg/kg xylazine. The musculophrenic vein appeared as a vessel with a diameter of 0.5-1.1cm located in the diaphragmatic musculature. The spectral display was a broad band structure with a wave-like shape. The Doppler measurement point was 1.5-2.7cm from the body surface. The diameter of the vein and the blood flow velocity did not differ significantly before and after sedation. Before sedation, the mean diameter (+/-SD) of the musculophrenic vein was 0.7 (0.2) cm, the maximum blood flow velocity 90.2 (38.6) cm/s, the mean blood flow velocity 60.4 (22.3) cm/s and the minimum blood flow velocity 41.4 (24.2) cm/s. There were significant correlations (r=0.45-0.90) between blood flow velocity before and after sedation and between minimum, maximum and mean blood flow velocities.

Vascular responses to 17 beta-oestradiol in postmenopausal women

The vascular responses to 17 beta-oestradiol were examined in 23 postmenopausal women (59 +/- 7 years [mean +/- SD]) using a placebo-controlled double-blind crossover design. All women received 1 mg 17 beta-oestradiol or placebo (P) sublingually on consecutive days in random order. Axial diameters and blood flow rates of the left common femoral arteries were determined before and 60-80 min after application of verum or placebo as well as 10-30 min after 10 mg isosorbide dinitrate (ISDN) with a quantitative duplex ultrasound technique. Oestradiol induced a vasodilation of femoral arteries (+6.4 +/- 4.1% of basal, P < 0.001 vs. basal and P), the vessel diameter was unchanged with placebo (+0.7 +/- 2.1%). The blood flow rate increased significantly after oestradiol application (+30 +/- 28%, P < 0.05 vs. basal and P), but not after placebo (+11 +/- 21%). Mean blood pressure and heart rate remained constant with both drugs. Despite its vasodilatory effect, ISDN significantly reduced the arterial blood flow after pretreatment with oestradiol and placebo, probably through cardiac preload reduction. In conclusion, 17 beta-oestradiol alters the vascular tone of systemic arteries resulting in a vasodilation and increase of blood flow. We suggest that these direct vascular actions may contribute to the preventive properties of oestrogens on cardiovascular diseases in postmenopausal women.

[The value of duplex sonography after orthotopic liver transplantation. Experience with 44 patients]

In a prospective study, 44 patients (11 women, 33 men) who had received orthotopic liver transplants underwent a total of 196 consecutive duplex Doppler ultrasound examinations. The aim of the study was to evaluate the correlation between the pulsatile flow index (PFI) and the damping index (DI) as far as complications as rejection or cholangitis were concerned. The patients were examined five times each on average. The PFI and DI were measured in the hepatic artery, the portal vein and the hepatic veins. The findings were compared with the clinical course (cholangitis, rejection) and the histomorphological diagnosis as determined in biopsy specimens. In biopsy-proven rejection episodes, the sensitivity of the PFI in the hepatic artery was 69.4%, the specificity 72.2%. The sensitivity of the DI in the hepatic vein was 89.4%, the specificity 89.1%. Combining the two, specificity was more than 90%. PFI and DI in the portal vein bore no apparent relation to clinical course or histomorphological diagnosis. We found duplex Doppler ultrasound extremely beneficial in determining the timing and indication for liver biopsy. In addition, this simple examination, which can be performed as often as desired, accurately shows the transplanted liver's response to measures taken to counter rejection.