Transonic Is Proud to Introduce:

Our new logo, accompanied by its tagline, the Measure of Better Results, projects the strength, balance and symmetry that conveys the company’s solid foundation on robust technology. It also embodies the company’s renewed sense of purpose, to further advance meaningful measurements for our customers. Empowered by our core values of Innovation, Collaboration, Accountability, Responsiveness and Excellence, our new Transonic brand symbolizes each employee’s commitment to helping our customers achieve the best possible results and/or outcomes. For your measurement needs, discover Transonic, the measure of better results!

A New Quantitative Microvascular Surgical Tool: Direct Volume Flow Measurement

Microvascular surgery involves very small blood vessels, often smaller than 1 mm in diameter. The advent of high resolution microscopes and highly specialized equipment in the early 1960s allowed specialized surgeons to perform, for the first time, successful intricate replantation (or reimplantation) procedures to reattach severed or amputated body parts. During the surgery, blood vessels are reconnected to restore circulation, for without adequate circulation, the replanted tissues die. Another type of microvascular surgery involves the use of tissue free or pedicle flaps for reconstructive procedures. Along with moving tissues, their associated arteries and veins are moved and then connected to local blood vessels to reestablish the tissue’s blood supply.

Transonic’s non-constrictive perivascular flowprobes, employing transit time ultrasound technology, measure volume blood flow directly within these small blood vessels. Transonic’s new line of microvascular flow probes are designed to assist the surgeon’s assessment of blood flow with accurate, quantitative volume flow measurements. Every surgeon is constantly forming a subjective clinical assessment of the quality of his or her work. Microvascular blood flow measurements now offer the surgeon a quantitative tool with which they can objectively assess the quality of the surgery. Unseen blood flow obstructions can be detected intraoperatively and repaired before leaving the operating room. This ability to correct otherwise undetectable flow restrictions provides the surgeon with a unique quantitative opportunity to improve the outcome for their patient.

A study by Selber, et al, from The University of Texas MD Anderson Cancer Center concluded that transit time flow volume “provides novel physiologic flap data and identifies flawed anastomoses…….These data have clinical value in microsurgery and hold the potential to reduce microvascular complications and improve outcomes.”¹

¹Selber, JC, Garvey, PB, Clemens, MW, Chang, EI, Zhang,H, Hanasono, MM. A Prospective Study of Transit Time Flow Volume (TTFV) Measurement for Intraoperative Evaluation and Optimization of Free Flaps.Plastic and Reconstructive Surgery.2012 Oct 16.(Epub ahead of print).

German Case Study Touts Real-time Flow Measurements for Acute Right Ventricular Heart Failure.

A case study from Heart and Vascular Center, Duisburg, Germany and recently published in the Journal for Cardiothoracic Surgery provides powerful testament to the value of Transonic flow measurements in managing acute heart failure and in weaning from ECMO in a left ventricular circulatory support patient.

A 66-year-old female presented with end-stage heart failure due to dilated cardiomyopathy. After four days of milrinone intravenous therapy, the patient was implanted with a HeartAssist 5 (Micromed Cardiovascular Inc. Houston, TX) device which features a custom Transonic ultrasonic flowprobe on the outflow graft to continuously measure real-time pump blood flow (Fig. 1). Edema and severe fluid retention prevented complete closure of the thorax. On days one and two post-op, mean flow measured by the Transonic flowprobe was 4.8 L/min.

On day three post-op, real-time flow began a progressive decline and loss of pulsatility that was associated with an increase of central venous pressure and progressive renal failure. Thermodilution measurements and echocardiography confirmed acute right heart failure. The patient was placed on VA extracorporeal membrane oxygenation (ECMO) on day ten post-op. Real-time flow and pulsatility recovered immediately. ECMO was discontinued on day 14 post-op. On day 17 post-op, the thorax was closed. Further recovery was uneventful.

The authors report that, by enabling the monitoring of the left ventricular preload and contractility throughout the post-operative period, Transonic real-time flow measurement proved to be a useful tool both for the diagnosis and the management of right heart failure, including weaning from ECMO. It was a reliable alternative to conventional techniques for the measurement of cardiac output in the clinical setting. Transonic measurements were validated by thermodilution measurements. Moreover, the loss of pulsatility in the flow curve foreshadowed insufficient LV preload, which allowed earlier intervention.

Spiliopoulos S, Guersoy D, Koerfer R, Tenderich G, “Beneficial aspects of real time flow measurements for the management of acute right ventricular heart failure following continuous flow ventricular assist device implantation,” J Cardiothorac Surg. 2012;7:119. (Transonic Reference # 9760AH)

Ultrasound Dilution Technology Used to Verify Dual-lumen Cannula Positioning During VV-ELS

A 2012 case report from the University of Maastricht, The Netherlands, published in Intensive Care Medicine, presented three illustrative cases where ultrasound dilution technique was used to verify optimal positioning of a dual-lumen catheter during VV-ELS. In all three patients, transthoracic echocardiography images were first taken to show positioning of the cannula. To verify optimal positioning, recirculation was measured by ultrasound dilution technique with the percentage recirculation displayed on an ELSA Monitor screen.

In the first two cases, ultrasound dilution recirculation measurements corroborated the cannula positioning displayed by the transthoracic image: the first confirmed optimal placement with only 2% recirculation; the second confirmed improper placement with 45% recirculation.

However, in the third patient, ultrasound dilution registered a 38% recirculation, even though the transthoracic echocardiography images showed good positioning of the cannula. This ultrasound dilution recirculation measurement prompted repositioning of the cannula that led to a decrease in mechanical ventilation and increased arterial saturation.

In light of this false positive by transthoracic echocardiography, the clinicians suggested that recirculation be measured in VV-ECMO patients to augment image guidance and confirm optimization of dual-lument extracorporeal life support.

Körver EP, Ganushchak YM, Simons AP, Donker DW, Maessen JG, Weerwind PW. Quantification of recirculation as an adjuvant to transthoracic echocardiography for optimization of dual-lumen extracorporeal life support.î Intensive Care Med. 2012; 38(5): 906-9. (Transonic Reference # ELS9679AH)

Blood Flow Research Using Rodent Models

Until the late 1980’s, much of physiological research and pharmaceutical study used large animal models such as dogs and primate to study human disease. In response to pressure from ethical activist groups, scientists began seeking other animal models that did not evoke the high emotional response as these species do. Rats and rodents were such an alternative, but there were obvious hurdles to making this switch. A spontaneously hypertensive rat (SHR) and others were developed for hypertension and diabetes studies. Other models could be scaled down, but on a very practical level, scientists also needed new tools that could permit study in small animals. Scientists could use standard medical devices for large species, and often did. However, these devices didn’t have the resolution nor the precision to work in these small animals. Consider the catheter size required to measure pressure in a 300 gram rat vs. a 20 kilo dog; or the precision required to measure flow in a rat renal artery that is <1 mm diameter vs. 3 – 4 mm. The new rodent models introduced huge challenges to biomedical instrumentation engineers like Transonic Systems’ team.

First 1 mm Flowprobes for the Rodent Model

Through collaboration with pioneering researchers such as Brian Murray, SUNY Buffalo, and Tom Smith, Bowman Gray School of Medicine (now Wake Forest Univ. Health Science), Transonic worked to miniaturize a small 1 mm flowprobe that could be used to measure renal blood flow in a rat. The smallest probe to date had been the 2R-series with a 2.5 x 3 mm lumen – impossibly big for a 1 mm rat renal artery. Size was not the only challenge. The flowmeter electronics would require an overhaul to operate at a much higher frequency to detect the ultrasonic phase shifts to measure blood flows of 2 – 4 ml/min with a probe of such small dimensions. A team of engineers accomplished just that in 1990 and the T106 and T206 Small Animal Flowmeters were introduced to the research community.

With the success of the new flowmeter fostering growth in the field of biomedical instrumentation and enabling hundreds of studies, Transonic established itself as a leader in the field. Throughout the past two decades, physiological research first in rats and now in transgenic mice has exploded with new models for hypertension, diabetes, stroke, hemorrhagic shock, and others with new pharmaceutical agents targeted to the rennin-angiotensin system to lower blood pressure and metabolic nitric oxide for vasodilation. Transonic blood flowmeters are essential instrumentation for cardiac output, renal blood flow, mesenteric, carotid, portal vein and femoral artery flow measurement. Publications citing Transonic flow measurement grew by thousands. The 2012 Transonic publication, Tool and Technique for Hemodynamic Studies in Rodents, captures over 20 years of this application knowledge and surgical protocols. To receive your own free copy, please sign up here.