Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-08-04
2004-04-27
Hayes, Michael J. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S004010, C604S102010
Reexamination Certificate
active
06726651
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices to be used during cardiovascular, pulmonary, and neurologic procedures where a cardiopulmonary bypass machine is used. More specifically, the present invention incorporates a cardiopulmonary bypass machine and an aortic catheter to provide neurological protection through differential perfusion and suction.
BACKGROUND OF THE INVENTION
In general, there has been a steady decline in the amount of cardiac morbidity and operative mortality directly associated with cardiopulmonary bypass (CPB) in recent years. Enhanced myocardial protection, more complete coronary revascularization, improved operating technique resulting in enhanced graft patency rates, and better general patient support such as improved cardiac anesthesia and intensive care practices have been cited as some of the primary reasons for better surgical outcomes. Blumenthal J A, et al. “Methodological Issues in the Assessment of Neuropsychologic Function After Cardiac Surgery,”
Ann Thorac Surg;
59:1345-50 (1995). However, despite the overall decrease in morbidity and mortality, the incidence of neurologic deficit, in the form of, fatal cerebral injury, stroke, retinal microvascular pathology, impaired level of consciousness, seizures, spinal cord injury, peripheral nerve injury and neuropsychologic deficit has increased.
The occurrence of neurologic deficit, after a cardiac procedure, depends upon a number of factors including: the type of operation, the age of the patient population, the prospective versus retrospective nature of the studies, and the sensitivity of the tests performed. Mills, “Risk Factors for Cerebral Injury and Cardiac Surgery,”
Ann Thorac Surg
1995, 59:1296-1299. Evidence has suggested that the incidence of stroke, the most dramatic form of neurologic deficit approaches 9% in patients greater than 75 years of age. In addition, severe aortic atheroma is a disease strongly linked to stroke and rises sharply with an increase in age. These correlative factors combined with a subsequent change in population demographics have allowed more high-risk patients, most notably the elderly, to be treated by cardiac surgery and unfortunately, with the attendant risk of neurologic deficit. Nevertheless, even though there is a greater risk of neurologic deficit with an increase in age, the inherent complications of cardiac surgery place all age groups, not just the elderly, at risk.
Neuropsychological testing, a means to quantify subtle cognitive changes in patients due to cerebral damage, has shown that as many as two-thirds of patients undergoing CPB demonstrate some type of neuropsychological deficit postoperatively. The affects of neuropsychologic deficit on any single patient are wide ranging and depend upon the patient's activity level and intellectual pursuits before surgery, however, common disabilities incurred by patients are impaired memory, concentration and hand eye coordination, with a predictably negative impact on life. Rogers A T, Newman S P, Stump D A, Prough D S: Neurologic Effects of Cardiopulmonary Bypass, in Gravlee G P, Davis R F Utley J R:
Cardiopulmonary Bypass Principles and Practice.
Baltimore: Williams and Wilkins, 1993, pp. 542-576.
In patients undergoing CPB surgery, substantial amounts of clinical data have shown that the primary etiological mechanisms contributing to neurologic and neuropsychologic deficit are cerebral embolization and hypoperfusion. Cerebral embolic infarction occurs when emboli, such as: platelet aggregation, aggregates of fibrin, clusters of microbubbles, boluses of air, and atherosclerotic plaques, are released into the general blood circulation and lodge in the brain. Hypoperfusion, a second theorized culprit, can potentially create cerebral ischemia, which may result in permanent cerebral infarction due to a lack of oxygenated blood flow to the brain.
Transcranial Doppler Ultrasonography (TCD) and Transcarotid Doppler Echocardiography have been used to measure and detect embolic signals, thereby quantifying when in surgical procedures embolic events are most likely to occur. Results have shown that atheromatous plaque can be released into the general blood circulation when there is cannulation of the aorta, manipulation of the heart and ascending aorta, and application or release of the cross-clamp or side biting clamp to the aorta. Furthermore, boluses of air or “surgical air” can enter the general blood circulation when there is cannulation of the heart or aorta and removal of the cross clamp, at the site of venous cannulation and when a surgical intervention requires the opening of the cardiac chambers. In addition, some believe that the extracorporeal circuit can be an ongoing source of potential embolic events. For instance, blood born emboli, such as platelet aggregation and fibrin can occur when anticoagulated blood contacts a foreign surface throughout the extracorporeal circuit and microbubbles may be formed within bubble oxygenators and membrane oxygenators in the extracorporeal circuit. Nevertheless, of all the types of emboli and the sources thereof, it is still unclear as to what type of embolic insult is of greatest detriment to the patient: total embolic volume, constitution of emboli, collateral arterial blood supply of the territory affected or the quality of preexisting parenchymal brain function. Barbut et al., “Aortic Atheromatosis and Risks of Cerebral Embolization,”
J Card
&
Vasc Anesth;
Vol 10, No 1: pp 24-30 (1996).
As is evident from the foregoing discussion, emboli can be released in a number of different ways and in a number of different forms. In addition, an increase in perfusion to resolve the problem of hypoperfusion can potentially expose the brain to more embolic debris since more blood flow is going to the cerebral circulation. Alternatively, a reduction in perfusion lowers the overall flow, volume and cycles of blood to the brain, which has the resultant effect of providing less opportunity for emboli to be introduced into the cerebral blood circulation, but may increase the deleterious effects of hypoperfusion.
Therefore, what has been needed and heretofore unavailable is a method and device for reducing cerebral embolism and eliminating hypoperfusion by assuring that adequate blood flow is being supplied to the brain. Substantial strides have been made addressing either embolic insult or hypoperfusion, but not both in the same device. The present invention solves both of these immediate problems, as well as others.
For example, various strategies have been proposed to mitigate the danger of embolic events during CPB surgery. The use of transesophageal echocardiography (TEE) has been used to assess the extent and severity of atherosclerotic plaque, in patients being diagnosed as having aortic atheroma, in order to optimize cannulation sites and minimize the release of plaque into the general blood circulation arising from aortic cannulation. Arterial line filters, bubble traps, air bubble detectors and the wide spread use of membrane oxygenators have reduced the amount of gaseous emboli released into the general blood circulation. Furthermore, rigorous deairing techniques have been shown to help remove “surgical air”, and a general awareness that the manipulation of the heart and aorta can potentially create an embolic event has substantially changed surgical techniques to try and limit these maneuvers. However, none of these techniques address hypoperfusion.
Even more recently, patent literature has disclosed devices and methods for reducing the amount of emboli during surgical interventions. Advances have been made which incorporate filters to trap emboli that may be released during CPB surgery. Patents describing these features include: U.S. Pat. Nos. 5,662,671, 5,769,816 and 5,846,260; WO 97/17100, WO 97/42879, WO 98/02084 and commonly owned, copending patent application Ser. No. 09/158,405 filed on Sep. 22, 1998, by Macoviak et al. In addition, WO 98/24377 describes a carotid filter for accomplishing the same general result
Esch Brady
Lee Mike
Macoviak John A.
Olsen Eric
Robinson Janine
Cardeon Corporation
Fulwider Patton Lee & Utecht LLP
Hayes Michael J.
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