Clinical results with a new acoustic device to identify the epidural space

Fifty patients scheduled for surgery under lumbar epidural anaesthesia were included in a study to evaluate the possibility of localising the epidural space solely by means of an acoustic signal. With an experimental set-up, the pressure generated during the epidural puncture procedure was translated into a corresponding acoustic signal. One anaesthetist held the epidural needle with both hands and detected the epidural space by means of this acoustic signal. At the same time, a second anaesthetist applied the loss of resistance technique and functioned as control. In all patients the epidural space was located with the acoustic signal. This was confirmed by conventional loss of resistance in 49 (98%) of the patients; in one patient (2%) it was not. We conclude that it is possible to locate the epidural space using an acoustic signal alone.     

Thoracic epidural puncture guided by an acoustic signal: clinical results

BACKGROUND AND OBJECTIVE: In previous studies we have demonstrated that it is possible and safe to identify the lumbar epidural space by an acoustic and visible signal. The use of an experimental set-up constructed for this purpose, the acoustic puncture assist device, the lumbar epidural puncture procedure became both audible and visible. In the present study we have extended the use of the device to localize the thoracic epidural space. We have also evaluated whether the device can be used as a practical tool to confirm correct catheter placement. METHODS: In 100 consecutive patients a prototype of the acoustic puncture assist device was connected to the epidural needle in order to localize the epidural space. The device translates the pressure encountered by the needle tip into a corresponding acoustic and visible signal and enables the anaesthesiologist to detect the epidural space by means of the acoustic signal. After catheter insertion, local anaesthetic was administered. Subsequently the epidural block was tested. In 10 patients the device was also connected to the epidural catheter after its insertion into the epidural space. RESULTS: In all 100 patients included in the study the epidural space was successfully located by means of the acoustic signal. The only recorded complication was intravascular catheter placement in two patients. CONCLUSIONS: It is possible to localize the thoracic epidural space guided by an acoustic signal. The method was shown to be safe, reliable and simple. Potential implications of this technique include better needle control, improved monitoring for training purposes and for clinical documentation of the thoracic epidural puncture as well as identifying correct catheter placement.     

Method of proximal anastomosis with a new assist device

Various devices have been invented for proximal anastomosis performed during coronary bypass surgery. Enclose II allows a handling of the needle to be similar to a single cross clamp proximal anastomosis with almost no blood loss. However, when creating the anastomotic hole, it is difficult to determine whether an incision into the aortic wall will extend to the intima, and in some instances there is a risk that the hemostatic membrane may be injured. With Enclose II's hemostatic confirmation tube, the hemostatic membrane is opened and the tube is inserted into the aortic wall. The vent plug of the extension tube is opened, blood fills between the aortic wall and the instrument, and air is removed. An isotonic saline solution is injected and the pressure checked to insure that no air enters. An incision into the aortic wall is then made with a scalpel. When the intima is pierced, isotonic saline solution will gush out. In this way, one can prevent injury to the hemostatic membrane and ensure a correctly pierced anastomotic hole in the intima--even with just 1 punch.     

Clinical experience with a pumpless extracorporeal lung assist device

We present three patients with respiratory failure in whom conventional mechanical lung ventilation resulted in unacceptably high levels of carbon dioxide, severe acidosis and high vasopressor requirements. A pumpless arteriovenous extracorporeal carbon dioxide removal device (Novalung) was inserted. Arterial carbon dioxide levels were reduced rapidly with a corresponding increase in pH, reduction in vasopressor requirements and reduction in inspiratory pressures. One patient required the additional use of high frequency oscillatory ventilation. There were no complications associated with use of the device. We conclude that use of extracorporeal carbon dioxide removal devices should be considered at an early stage in the management of respiratory failure refractory to conventional ventilatory techniques.     

Numerical study of a new ventricular assist device

The present work presents a numerical study of two axial ventricular assist devices (VADs) with two different designs. The geometry of the first design was inspired by DeBakey's rotary blood pump and the geometry of the second design is based on BioCirc’s pediatric VAD. The goal is to see which of the two designs has promising capabilities in terms of pressure differential, flow rate, and thrombosis before proceeding to deeper investigations. In this study a computational fluid dynamics tool was used to simulate and calculate the hemodynamics in the two investigated models. Both models were investigated for a flow rate of 5 L/min at rotational speeds between 10 000 and 15 000 rpm.     

Initial clinical experience with a new temporary left ventricular assist device

A new, simple left ventricular assist system has been developed and its use in experimental animals has been evaluated. The system achieves ventricular drainage by a transaortic valve cannula and utilizes a new centrifugal pump; the blood access is unique in requiring only a simple end-to-side synthetic graft anastomosis to the ascending aorta. Adequate pulsatility is obtained by concomitant use of an intraaortic balloon pump. This case report documents our initial clinical experience with this system in a postoperative patient with profound left ventricular failure unresponsive to all usual treatment. There was temporary recovery of left ventricular function upon decannulation after five and a half days of assist pumping. Despite the eventual death of the patient, the system functioned adequately, suggesting that it has good potential for use in a small, selected group of patients.     

Bridge to transplantation with a left ventricular assist device

A 61-year-old female patient was diagnosed with dilated cardiomyopathy with severe left ventricle dysfunction. Two days after admission, continuous renal replacement therapy was performed due to oliguria and lactic acidosis. On the fifth day, an intra-aortic balloon pump was inserted due to low cardiac output syndrome. Beginning 4 days after admission, she was supported for 15 days thereafter with an extracorporeal left ventricular assist device (LVAD) because of heart failure with multi-organ failure. A heart transplant was performed while the patient was stabilized with the LVAD. She developed several complications after the surgery, such as cytomegalovirus pneumonia, pulmonary tuberculosis, wound dehiscence, and H1N1 infection. On postoperative day 19, she was discharged from the hospital with close follow-up and treatment for infection. She received follow-up care for 10 months without any immune rejection reaction.     

Technique and results with a roller pump left and right heart assist device

During the last 10 years we have inserted a roller pump-driven left heart assist device in 72 patients and a right heart assist device in 7 patients for profound heart failure after a variety of cardiac surgical procedures. In addition a percutaneous left heart assist device (transseptal insertion of left atrial cannula via a femoral vein) was employed in 5 patients with profound cardiogenic shock after acute myocardial infarction. Thirty patients (41.7%) were weaned from the left heart assist device and 21 (29.2%) were discharged from the hospital. Two patients (40.0%) were weaned from the right heart assist device, but both later died during the postoperative period. Of the 5 patients in whom a percutaneous left heart assist device was inserted, 4 underwent successful emergency percutaneous transluminal coronary angioplasty, but all 5 patients died. Causes of death included severe coagulopathy, irreversible extensive myocardial infarction and cardiac failure, refractory arrhythmias, severe "shock" lung, and multisystem failure. In summary, satisfactory results can be achieved with a roller pump-driven left and right heart assist device for severe postoperative heart failure. Further experience should be obtained with the percutaneous technique to assess its efficacy in treating patients with acute myocardial infarction and cardiogenic shock.