Classic Flow and Pressure Monitoring Techniques in Conscious Rats Applied in Development of PKPD Model of Interrelationship between Mean Arterial Blood Pressure, Cardiac Output and Total Peripheral Resistance
2.5PSS Flowprobes are ideal for rat ascending aorta application.
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Physiologists at Leiden's Academic Centre for Drug Research in collaboration with Novartis Institutes for BioMedical Research, Novartis Pharmaceuticals Corporation, US have developed a mechanism-based pharmacokinetic-pharmacodynamic (PKPD) model in rats that could be used to characterize the effects of cardiovascular drugs with different mechanisms of action (MoA) on the interrelationship between blood pressure (BP), cardiac output (CO) and total peripheral resistance (TPR).
The cardiovascular effects of six drugs with diverse MoA were characterized in spontaneously hypertensive rats by chronically instrumenting the rats with Transonic ascending aorta flowprobes and femoral arterial catheters/transmitters (DSI) for continuous monitoring of MAP, heart rate, stroke volume, CO and TPR. Data were analyzed in conjunction with independent information on the time course of drug concentration using a mechanism-based PKPD modelling approach.
By simultaneous analysis of the effects of six drugs, the dynamics of the interrelationship between BP, CO and TPR were quantified. The researchers were able to distinguish system-specific parameters from drug-specific parameters. Therefore, their drug-independent model could be further used to quantify and predict the cardiovascular effects of other drugs. They expect that ultimately, their model could be used to obtain preclinical data to predict the effects of a particular drug on BP in humans.
Snelder N et al, “PKPD modelling of the interrelationship between mean arterial BP, cardiac output and total peripheral resistance in conscious rats,” Br J Pharmacol. 2013, Aug;169(7):1510-24.
“Analysis of the Spatial Sensitivity of Conductance/Admittance Catheter Ventricular Volume Estimation” captured front page coverage in the August 2013 issue of IEEE Transaction on Biomedical Engineering. A cover graphic compared the sensitivities of Admittance and Conductance Catheter Technologies.
The University of Texas research team of ER Larson, MD Feldman, JW Valvano, and JA Pearce conducted advanced finite element modeling and analysis to assess the sensitivity of each method in determining the conductance of blood (Gb) and the technology’s ability to separate out the conductance of muscle (Gm), also known as parallel conductance. The sensitivity with which a measurement modality can determined Gb and Gm directly impacts the accuracy of the subsequent ventricular volume calculations.The models show that the Admittance method correctly removes parallel conductance from muscle, and results in a more uniform sensitivity distribution in the LV blood pool. In contrast, the hypertonic saline method, which is used with Conductance Catheters, overestimates parallel conductance in each model.
Transonic® Introduces Its “Above and Beyond” Optima Flowmeter
Single–channel (HT353) Optima Flowmeter and dual channel (HT363) Optima Flowmeter as part of the AureFlo® system.
The best just got better! Transonic’s versatile, new-generation Optima Flowmeter goes above and beyond earlier HT300-Series Surgical Flowmeter models. Single and dual-channel models can be used as stand-alone Flowmeters or be incorporated into the AureFlo® system. Improved Optima electronics make processing of results quicker. Accuracy is unsurpassed. The Optima’s higher acoustic frequency range makes even smaller Flowprobes (down to 0.7 mm) compatible.
The Optima Flowmeter works with the largest variety of Flowprobe styles available, including the new Confidence Flowprobe® for highly accurate measurement on turbulent vessels, the OptiMax® banding Flowprobe, and small Microvascular Flowprobes. Application to vessels is easier and faster. Enhanced waveform quality results in highly accurate data. Excellent customer support complements the Optima’s release.
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CiDA Features Vascular Access Procedures Guided by
Transonic® Flow Measurements
COnfidence Flowprobes® consist of a Flowprobe shell and a single-use soft, flexible Ultrafit liner. The form-fitting Ultrafit Liner slips into the transducer shell to encircle the vessel and keep the vessel in place and protect it during a flow measurement.
Real-time vascular access surgical procedures were highlighted at the CiDA (Controversies in Dialysis Access) 10th Annual Meeting last month. Dr. John Ross and his surgical team demonstrated live cases via satellite feed from his new Regional Medical Center in Orangeburg, SC to the San Francisco convention hall’s big screens.
Dr. Ross narrated the cases as they were performed in the various surgical suites. In the first case, real-time HVT100 measurement was shown associated with a HeRO graft which was referred for low flow. The HVT100’s intra-access flow measured 1400 mL/min which lead to a clinical decision not to intervene. In others, Dr. Ross showed the flow measurement on the HVT100 meter, also in a HeRO graft in a patient with arm swelling and apparent central venous stenosis. Flow measurement in the inflow and outflow segments of the HeRO graft revealed consistent flow of 1700 ml/min. Again, the clinical decision was not to intervene in the graft, but further investigate the cause of the arm swelling.
In another case, Dr. Jose Zamora from San Diego demonstrated wrapping a fistula with an Artegraft, a bovine artery graft, as a COnfidence Flowprobe® proximal to the access measured flow continuously. This was the first time the COnfidence Flowprobe® was used on a high flow fistula with turbulent flow. In spite of the turbulence, the novel 4-crystal Probe produced consistent and accurate measurements.
MILLER Banding Procedure Video Premiered at CiDA
MILLER Banding is a simple and effective minimally invasive technique for treating steal syndrome and reducing flow in high-flow fistulas using the HVT100 Endovascular Flowmeter. A video of the step-by-step MILLER banding procedure in which an angioplasty balloon is used as a sizing dowel for banding and intra-graft flow measurements with the HVT100 document precise flow reduction was premiered in the Transonic exhibit at CiDA.
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Columbia University Transplant Video Demonstrates Value of Intraoperative Flow Measurements during Live Donor Liver (A2ALL) Transplant Case
High stakes orthotopic liver transplantation demands both expert surgical skills and sophisticated tools to inform during the operation. Intraoperative flow measurement is such a tool. It provides invaluable information because both the portal vein and the smaller hepatic artery must deliver blood to the transplanted liver in order for the organ to survive. The usual visual clues from a transplanted allograft can be misleading since an obviously perfused transplanted liver does not reveal whether both the hepatic artery and portal vein are actually perfusing the liver or if the flow from each is adequate. Measuring intraoperative blood flows following the respective anastomoses of these two vessels inform and assure the surgeon that each is delivering blood to the transplanted liver. This is of particular importance in the portal vein which is prone to kinking.
The video, filmed and edited at Columbia Presbyterian Hospital in NYC, includes an introduction by Dr. Jean Edmond, Chief of Transplantation and Co-chair of the A2ALL study, a review of the necessary flow measurement equipment, demonstration of the proper flow measurement technique, and an example procedure documenting flow results for the patient’s record.
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