Current Projects

Longitudinal Study of Integrated CT Surgery Residency Applicants: Future Career Choices

Contributors: Chirag Buch, Nitin A. Das, Edward Y. Sako, MD, PhD

With the availability of the 6 year integrated program for cardiothoracic surgery residency, the new medical graduates have a career choice to make early in their life. But it is a limited opportunity and not everyone manages to get into a program. So for those who do not secure a spot, do they continue to pursue this interest with the traditional pathway? As an educationist, Dr. Sako is curious about the effects of this new paradigm.

 

Familiarity as a Factor in Residency Selection

Contributors: Merideth Geib, Nitin A. Das, Edward Y. Sako, MD, PhD

Multiple factors are involved in both choosing and being chosen by a residency program.  In this study the prevalence of experiences beyond the application review and interview process are examined.

Biochemical Changes in Lung After Reperfusion Injury and its Attenuation with Tacrolimus – Dose Response

Principal Investigator: Nitin A. Das

This project is funded by Morrison Trust.

Ischemia –reperfusion (I-R) injury is unavoidable event during a solid organ transplant and it increases the risk of rejection by upregulation of surface antigens in the donor organ. In a recently published study, our lab demonstrated attenuation of I-R injury in lung transplants using nanoparticle tacrolimus (nTac) when administered by inhalation to the donor lung prior to procurement(1). It was noted that this benefit was reduced when the tissue level of nTac was lower in the isograft and a possible dose-response effect was postulated which needs further evaluation.

Objective: To define the optimal dose of tacrolimus to the donor lung prior to harvest that would reduce I-R injury by evaluating the biochemical changes in the lung and blood with varying doses.

Preliminary data: Bayer, Das, et al. demonstrated attenuation of I-R injury, with functional improvement (better oxygenation) and lower pro-inflammatory cytokine and cellular infiltrate in the isograft when pre-treated with nTac by inhalation prior to procurement(1).

Study Design: This study will evaluate the release of cytokines and chemokines in the transplanted lungs and systemic circulation after period of ischemia and reperfusion. We will correlate these levels with the level of tacrolimus and reduction of I-R injury in the lungs.

 

Lung Expansion and Aeration Monitor in a Pig Model

Contributors: Daniel T. DeArmond, MD, Nitin A. Das, Joel E. Michalek PhD

Brief Description: Surgery of the lung, for example removing a tumor in the lung, and trauma to the lung, for example a gunshot wound to the lung, have the potential to lead to partial or complete collapse of the lung; this condition can develop rapidly or in a delayed manner and may be fatal or lead to significant patient complications.  Collapse of the lung in these situations is most often caused by air or fluid/blood accumulating in the space between the lung and the rib cage.  Because the rib cage is a rigid structure and the lung is relatively compressible, the build-up of air or fluid/blood in the space between the rib cage and the lung pushes on the lung and causes the lung to collapse.  This type of lung collapse is treated by placing a large tube into the space between the rib cage and the lung to suction out the air and/or fluid/blood and re-expand the lung; importantly, this treatment is not always successful.  Early detection of lung collapse in these scenarios can save lives, minimize complications, and potentially lower the costs of patient care but currently there is no direct, real-time way to monitor the space between the rib cage and lung.  There is a missed opportunity in this clinical realm in that the tubes that are placed into the space between the lung and the rib cage to suction air and/or fluid/blood could easily be connected to a pressure sensor which could give care-givers real-time, continuous information about the status of lung-expansion.  Such a pressure sensor could monitor the success of treatment of lung collapse by detecting a pressure change when the lung was re-expanded and could monitor the ongoing maintenance of lung expansion in patients who had recently undergone lung surgery or lung trauma in real time.  In a similar manner, it could also be used in the setting of heart surgery to make sure that blood was not accumulating around the heart, a common problem after heart surgery which can decrease the pumping strength of the heart and lead to complications or death after heart surgery.  In our lab, we have developed a pressure sensor based on the electrical properties of the lung and the heart.  We have used this device to prove that we can detect lung collapse and confirm the restoration of lung re-expansion in experimental rats.  We have shown that our pressure sensor is more sensitive than chest x-ray (the current gold standard) at detecting lung collapse in rats.  We hope in the future to be able to translate the use of this device into humans but the next step is to test in a large mammalian animal model as this is the next closest model to humans.

Understanding Pulmonary Valve Architecture and Variation: Implications for the Ross Procedure

Contributors: Hayden Joseph*, Conner Ryan*, Will Fancher, Nitin A. Das, Lauren C. Kane, S Adil Husain, John H. Calhoon (*authors share equal credit)

Anatomical variation in pulmonary valve architecture has not been well defined.  An understanding of such variances may impact surgical techniques employed for operations such as the Ross Procedure.

 

Central Venous Catheters: A Qualitative Analysis of Patient And Nursing Preference

Contributors: Hayden Joseph*, Conner Ryan*, Nitin A. Das, John H. Calhoon, MD

There appears to be no consensus about complication rates of infection, thrombotic event and arterial injury when comparing central venous catheter (CVC) insertion sites. The aim in this study is to gain an understanding of patient and nursing preference for central line location, internal jugular vein (IJ) versus subclavian vein (SC), based on qualitative measures of comfort, ease of use, function, and satisfaction.

 

An In-vitro Model for Evaluation of Extubation

Contributors: William N. Fancher*, Nitin A. Das, Lauren C. Kane, John H. Calhoon

*Funded by the American Association for Thoracic Surgery Graham Foundation

In clinical practice a common method of extubation involves complete deflation of the cuff prior to ETT removal.  This technique may result in retention of subglottic secretions as the ETT passes through the vocal cords, with subsequent aspiration.  We hypothesize that passive deflation of the cuff by cutting the pilot tube will result in less retained secretions compared to active, complete deflation using a syringe.

 

Total Anomalous Pulmonary Venous Connection: Factors Affecting Outcomes

Contributors: Elizabeth Tapley, Elaine Campbell MD, Nitin A. Das, Adil S. Husain MD, Lauren C. Kane MD, John H. Calhoon, MD

 

Aprotinin Use In Bilateral Lung Transplantation Requiring Cardiopulmonary Bypass: Data Refutes Clinical Impression

Contributors: Eilers AE, Albahra S, Das NA, Prihoda TJ, Baisden CE, DeArmond DT, and Johnson SB

Aprotinin was used extensively in cardiothoracic as an agent to reduce blood loss and transfusion requirements until taken off the market in 2008 secondary to mounting litigation and concerns that it may cause neurologic and/or renal impairment.  It was our clinical impression however that aprotinin was very effective at minimizing blood loss in patients undergoing bilateral lung transplantation utilizing cardiopulmonary bypass (CPB), and that it did so without causing significant neurologic or renal impairment. The purpose of this study was to review our own experience using aprotinin in this specific patient population.

 

Esophageal Stenting: Indications, Outcomes and Expectations

Contributors: Scott B. Johnson, MD, Nitin A. Das and Helen Mari L. Merritt, DO

The use of esophageal stents is evolving as a useful adjunct in the treatment of complex esophageal disorders. We reviewed our own stenting experience to examine patient outcomes, complications and rates of re-intervention as they relate to indications and underlying patient diagnoses.

• Incidence of sternal wound infection and correlation with timing of pre-op antibiotic (John H. Calhoon, MD)
• Length of antibiotic treatment necessary after surgical treatment of endocarditis (John H. Calhoon, MD.)
• Mapping the cardiac conduction system (Chirag Buch, John H. Calhoon, MD.)
• Cervical anastomotic complications with and without Penrose drain after esophagectomy (Scott B. Johnson, MD)
• Evaluation of mechanotransduction in attenuation of ischemic injury to rat lung (Nitin A. Das)
• Development of Ex-Vivo Lung Perfusion at UT Health San Antonio (Nitin A. Das)
• Heart I-R injury in mice with tacrolimus (Nitin A. Das)
• Stem cells in rat lung transplantation (rejection and I-R injury) (Nitin A. Das)