Comparison of Carotid Blood Flow Measured by Ultrasound and Cardiac Output in Patients Undergoing Cardiac Surgery.

BACKGROUND: In general, cerebral blood flow accounts for 10-15% of cardiac output (CO), of which about 75% is delivered through the carotid arteries. Hence, if carotid blood flow (CBF) is constantly proportional to CO with high reproducibility and reliability, it would be of great value to measure CBF as an alternative to CO. The aim of this study was to investigate the direct correlation between CBF and CO. We hypothesized that measurement of CBF could be a good substitute for CO, even under more extreme hemodynamic conditions, for a wider range of critically ill patients. METHODS: Patients aged 65-80 years, undergoing elective cardiac surgery were included in this study. CBF in different cardiac cycles were measured by ultrasound: systolic carotid blood flow (SCF), diastolic carotid blood flow (DCF), and total (systolic and diastolic) carotid blood flow (TCF). CO simultaneously was measured by transesophageal echocardiography. RESULTS: For all patients, the correlation coefficients between SCF and CO, TCF and CO were 0.45 and 0.30, respectively, which were statistically significant, but not between DCF and CO. There was no significant correlation between either SCF, TCF or DCF and CO, when CO was <3.5 L/min. CONCLUSIONS: Systolic carotid blood flow may be used as a better index to replace CO. However, the method of direct measurement of CO is essential when the patient's heart function is poor.

[Effects of dexmedetomidine on microcirculatory perfusion in rabbits with renal ischemia/reperfusion injury: quantitative evaluation with contrast-enhanced ultrasound].

OBJECTIVE: To investigate the effects of dexmedetomidine on renal microcirculatory perfusion in rabbits with renal ischemia/reperfusion (I/R) injury rabbit by quantitative analysis of contrast-enhanced ultrasound (CEUS). METHODS: Twenty- four New Zealand rabbits were randomly divided into 3 groups (8 in each), including a control group, renal I/R injury group and dexmedetomidine group. In the latter two groups, the right kidney of the rabbits was resected and I/R injury was induced in the left kidney. In dexmedetomidine group, the rabbits received an intraperitoneal dose of 10 µg/kg dexmedetomidine 30 min before renal ischemia, and 24 h after reperfusion, the renal size and renal artery resistance (RI) were measured, and renal cortex perfusion was observed by CEUS. The time-to-peak intensity (TTP), peak signal intensity (PSI), gradient between start frame to peak frame (Grad) and area under the curve (AUC) were quantitatively analyzed using the time-intensity curves. Pathological changes of the kidney were also observed. RESULTS: Compared with the control group, the rabbits in I/R and dexmedetomidine groups showed distinct changes of the renal size with obvious renal pathologies. RI, PPT and AUC all increased, and PSI and Grad decreased significantly in I/R and dexmedetomidine groups (P<0.05). Compared with I/R group, obvious improvement of the renal size and renal pathologies were observed in dexmedetomidine group, which showed significantly decreased RI, PPT and AUC and increased PSI and Grad (P<0.05). CONCLUSION: CEUS combined with the time-intensity curve parameters allows quantitative and dynamic analysis of the protective effects of dexmedetomidine on microcirculatory perfusion in rabbits with renal I/R injury.

A neurosteroid analogue photolabeling reagent labels the colchicine-binding site on tubulin: a mass spectrometric analysis.

Previous studies have shown that the neurosteroid analogue, 6-Azi-pregnanolone (6-AziP), photolabels voltage-dependent anion channels and proteins of approximately 55 kDa in rat brain membranes. The present study used two-dimensional electrophoresis and nanoelectrospray ionization ion-trap mass spectrometry (nano-ESI-MS) to identify the 55 kDa proteins (isoelectric point 4.8) as isoforms of ß-tubulin. This identification was confirmed by immunoblot and immunoprecipitation of photolabeled protein with anti-ß-tubulin antibody and by the demonstration that 6-AziP photolabels purified bovine brain tubulin in a concentration-dependent pattern. To identify the photolabeling sites, purified bovine brain tubulin was photolabeled with 6-AziP, digested with trypsin, and analyzed by matrix-assisted laser desorption/ionization MS (MALDI). A 6-AziP adduct of TAVCDIPPR(m/z = 1287.77), a ß-tubulin specific peptide, was detected by MALDI. High-resolution liquid chromatography-MS/MS analysis identified that 6-AziP was covalently bound to cysteine 354 (Cys-354), previously identified as a colchicine-binding site. 6-AziP photolabeling was inhibited by 2-methoxyestradiol, an endogenous derivative of estradiol thought to bind to the colchicine site. Structural modeling predicted that neurosteroids could dock in this colchicine site at the interface between α- and ß-tubulin with the photolabeling group of 6-AziP positioned proximate to Cys-354.