Biomedical subjects

R L Cothran

Publications and source records attributed to R L Cothran.

4 recordsLinked to original sources

PubMed2001

MR imaging of meniscal contusion in the knee.

OBJECTIVE: We describe focal abnormal signal of the meniscus in the knees of six patients who had a history of acute trauma to the knee. This signal abuts the articular surface of the meniscus on MR imaging but does not meet criteria for a meniscal tear or degeneration. CONCLUSION: Acute trauma to the knee may cause an abnormal signal in the meniscus that does not meet the previously described criteria for a meniscal tear or an intrasubstance degeneration. This abnormal signal could be misinterpreted as a tear because of its contact with the articular surface; this signal is seen most often in our series in the setting of an anterior cruciate ligament tear with adjacent bone contusions. We suggest that this signal may be due to a contusion of the meniscus and that the signal may resolve over time in some patients.

Adult↗

PubMedDate not supplied

Myocardial tolerance to mechanical actuation is affected by biomaterial characteristics.

Direct mechanical ventricular actuation (DMVA) uses a pressure regulated heart cup, fabricated from silicone rubber (SR) for mechanical massage of the heart. Because DMVA has demonstrated potential for long-term circulatory support, investigations are currently exploring the use of more durable materials for fabricating DMVA heart cups. This study assessed the acute effects of heart cups fabricated from SR versus polyurethane (PU) on the myocardium. Dogs (n - 18) received DMVA for 4 hr of ventricular fibrillation (VF) using either SR (n = 10) or PU (n = 8) cups. Microspheres were used to determine perfusion during sinus rhythm (control) and at 2 and 4 hr of support. After support, myocardial biopsies were assayed for high energy phosphate content. Results demonstrated that PU cups required relatively frequent adjustments in drive line parameters that were likely due to material softening during PU cup support. Both PU and SR cups achieved similar hemodynamics during 4 hr of support. Myocardial perfusion, however, demonstrated a marked hyperemia at 4 hr of PU versus SR cup support. Regional high energy phosphate content was significantly decreased in hearts supported by PU versus SR cups. These results suggest that the relatively compliant characteristics of SR materials are important for achieving effective DMVA support without injuring the myocardium.

Adenosine Triphosphate↗

PubMedDate not supplied

Prolonged total circulatory support using direct mechanical ventricular actuation.

Direct mechanical ventricular actuation (DMVA) is a unique, non blood contacting method for biventricular cardiac assist. Although DMVA has successfully provided cardiac assist for more than 7 days in humans, with long-term survival, its potential for long-term circulatory support has not been adequately investigated. DMVA has not been studied in the large ruminants commonly used to evaluate support devices. To develop a large animal experimental model of prolonged total circulatory support using DMVA, Suffolk sheep (n = 10) underwent sterile instrumentation for hemodynamic and chemistry monitoring. After baseline values were obtained, a left lateral thoracotomy and pericardotomy were performed. Upon electrical ventricular fibrillation (VF), DMVA was begun and the thoracotomy closed. Total circulatory support was continued until mean arterial pressure (MAP) persisted below 50% of the baseline value for more than 1 hr, with a goal of 7 days' support. Mean duration (plus or minus the standard deviation [SD]) of circulatory support was 65.9 +/- 56.8 hr (range, 10-168 hr). Pressors were not used during DMVA support. The subject supported for the maximal time (7 days) was defibrillated into sinus rhythm. No CK-MB fraction was greater than 1%, suggesting that DMVA, even with prolonged application during VF, does not result in myocardial injury. Blood urea nitrogen and creatinine levels indicate renal function was preserved. The model described represents the longest period any animal has been supported in VF using DMVA. This new model will be useful in determining what limitations, if any, exist to the prolonged use of DMVA for circulatory support.

Animals↗

PubMedDate not supplied

NMR spin-lattice relaxation in tissues with high concentration of paramagnetic contrast media: evaluation of water exchange rates in intact rat muscle.

High concentrations of GdDTPA in extracellular water of tissue cause the intrinsic relaxation rate of water to become greater than the coupling rate between intracellular and extracellular water compartments. The fast exchange limit is no longer valid and distinctly nonexponential spin-lattice recovery is observed. T1 relaxation recovery was characterized by a double exponential curve when striated rat muscle was immersed in a highly concentrated (110 Mm) isotonic solution of GdDTPA. When the water exchange rate through cell membranes in intact muscle tissue was calculated (using a two-compartment exchange model) and compared to similar data determined from T2 Carr-Purcell-Meiboom-Gill experiments, a significant discrepancy was found.

Animals↗