David B. Loran

Deep venous thrombosis prophylaxis in trauma: improved compliance with a novel miniaturized pneumatic compression device

OBJECTIVE Intermittent pneumatic compression (IPC) devices prevent lower-extremity deep venous thrombosis (LEDVT) when used properly, but compliance remains an issue. Devices are frequently discontinued when patients are out of bed, and they are rarely used in emergency departments. Trauma patients are at high risk for LEDVT; however, IPCs are underused in this population because of compliance limitations. The hypothesis of this study was that a new miniaturized, portable, battery-powered pneumatic compression device improves compliance in trauma patients over that provided by a standard device. METHODS This was a prospective trial in which trauma patients (mean age, 46 years; revised trauma score, 11.7) were randomized to DVT prophylaxis with a standard calf-length sequential IPC device (SCD group) or a miniaturized sequential device (continuous enhanced-circulation therapy [CECT] group). The CECT device can be battery-operated for up to 6 hours and worn during ambulation. Timers attached to the devices, which recorded the time each device was applied to the legs and functioning, were used to quantify compliance. For each subject in each location during hospitalization, compliance rates were determined by dividing the number of minutes the device was functioning by the total minutes in that location. Compliance rates for all subjects were averaged in each location: emergency department, operating room, intensive care unit, and nursing ward. RESULTS Total compliance rate in the CECT group was significantly higher than in the SCD group (77.7% vs. 58.9%, P =.004). Compliance in the emergency department and nursing ward were also significantly greater with the CECT device (P =.002 and P =.008 respectively). CONCLUSIONS Previous studies have demonstrated that reduced compliance with IPC devices results in a higher incidence of LEDVT. Given its ability to improve compliance, the CECT may provide superior DVT prevention compared with that provided by standard devices.

Seventy-two hour gas exchange performance and hemodynamic properties of NOVALUNG iLA as a gas exchanger for arteriovenous carbon dioxide removal.

Objective: Acute respiratory failure is complicated by acidosis and altered end-organ perfusion. NOVA-LUNG®iLA is an interventional lung assist (ILA) device for arteriovenous carbon dioxide removal (AVCO2R). The present study was conducted to evaluate the device for short-term CO2 removal performance and hemodynamic response. Methods: Six adult sheep received cannulation of the jugular vein and carotid artery. The ILA-AVCO2R circuit was placed on the sheep for 72 hours. Hemodynamics and PaCO2 were measured; CO2 removal was calculated while varying sweep gas flow rates (Qg), device blood flow rates (Qb), and PaCO2. Results: Hemo-dynamic variables remained normal throughout the 72 hour study. CO2 removal increased with increases in Qgor Qb. Mean CO2 removal was 119.3 ml/min for Qb 1L/min, Qg 5 L/min, and PaCO2 40 - 50 mmHg.PaCO2 was directly proportional to CO2 clearance (R-0.72, p B/0.001). Conclusion: NOVALUNG®iLA can provide near total CO2 removal with Qb 1 - 2 L/min,Qg 5 L/min, and minimal flow resistance (3.889/0.82 mmHg/L/min). PaCO2 correlates with CO2 removal and is dependent on Qb and Qg.

Predictors of alveolar air leaks.

Persistent air leaks are caused by the failure of the postoperative lung to achieve a configuration that is physiologically amenable to healing. The raw pulmonary surface caused by the dissection of the fissure often is separated from the pleura, and the air leak fails to close. Additionally, higher air flow thorough an alveolar-pleural fistula seems to keep the fistula open. Other factors that interfere with wound healing, such as steroid use, diabetes, or malnutrition, can result in persistence of the leak. A thoracic surgeon can minimize the incidence of air leak through meticulous surgical technique and can identify patients in whom the balance of risks (Table 1) and benefits warrant operative intervention based on an understanding of the underlying pathophysiology.

Pneumothorax in patients with acute respiratory distress syndrome: pathophysiology, detection, and treatment.

Pneumothorax is a frequent and potentially fatal complication of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). Prompt recognition and treatment of pneumothoraces is necessary to minimize morbidity and mortality. The radiologic and clinical signs of pneumothoraces in ARDS patients may have unusual and subtle features. Furthermore, small pneumothoraces in these patients can cause severe hemodynamic or pulmonary compromise. Sparse clinical literature exists on when or how to treat pneumothoraces once they develop in patients with ARDS. In this article, the authors review the pathogenesis, radiologic signs, clinical significance, and treatment of pneumothoraces in ARDS patients. Treatment options include traditional tube thoracostomy, open thoracotomy, and image-guided percutaneous catheters.

Development of ambulatory arterio-venous carbon dioxide removal (AVCO2R) : The downsized gas exchanger prototype for ambulation removes enough CO2 with low blood resistance

We are developing an ultra compact gas exchanger to allow ambulation during arterial-venous CO2 removal (AVCO2R). The ambulatory AVCO2R gas exchanger (135 ml prime volume and 1.3 M2 gas exchange surface area) is made of polymethylpentene hollow fibers. The gas exchanger was attached to sheep carotid artery (12F) and jugular vein (14F) by percutaneous cannulae for 6 hours (n = 5). Device CO2 removal was measured and calculated at a constant blood flow rate of 1 L/min coupled with varying sweep gas from 1 to 15 L/min, and at constant sweep gas flow of 2 L/min coupled with varying blood flow from 0.5 to 1.25 L/min to determine capacity of CO2 removal at Pa CO2 = 40–50 mm Hg. Blood gases, CO2 removal and hemodynamics were recorded at 0, 3, and 6 hours. CO2 removal increased with sweep gas flow rate and with increase of device blood flow. Hemodynamics remained unchanged throughout study. Gas exchanger resistance remained stable at 2.3 ± 0.53 mm Hg/L/min. CO2 removal with 1 L/min blood flow and 2 L/min sweep gas was 110 ± 12 then stabilized at 85 ± 14 mL/min to 6 hours. The compact ambulatory AVCO2R gas exchanger achieves stable, near total CO2 removal for at least 6 hours with a simple arteriovenous shunt.

Development of "plug and play" TransApical to aorta VAD.

Our TransApical to Aorta pump, a simple and minimally invasive left ventricular (LV) assist device, has a flexible, thin-wall conduit connected by six struts to a motor with ball bearings and a turbine extending into the blood path. Pulsatile flow is inherent in the design as the native heart contraction preloads the turbine. In six healthy sheep, the LV apex was exposed by a fifth intercostal left thoracotomy. The pump was inserted from the cardiac apex through the LV cavity into the ascending aorta. Aortic and LV pressure waveforms, pump flow, motor current, and pressure were directly measured. All six cannula pumps were smoothly advanced on the first attempt. Pump implantation was <15 minutes (13.6 ± 1.8 minutes). Blood flow was 2.8 l/min to 4.4 l/min against 86 ± 8.9 mm Hg mean arterial blood pressure at maximum flow. LV systemic pressure decreased significantly from 102.5 ± 5.55 mm Hg to 58.8 ± 15.5 mm Hg at the fourth hour of pumping (p = 0.042), and diastolic LV pressure decreased from 8.4 ± 3.7 to 6.1 ± 2.3 mm Hg (p > 0.05). The pump operated with a current of 0.4 to 0.7 amps and rotation speed of 28,000 to 33,000 rpm. Plasma free hemoglobin was 4 ± 1.41 mg/dl (range, 2 to 5 mg/dl) at termination. No thrombosis was observed at necropsy. A left ventricular assist device using the transapical to aorta approach is quick, reliable, minimally invasive, and achieves significant LV unloading with minimal blood trauma.