Chemical apparatus and process disinfecting – deodorizing – preser – Blood treating device for transfusible blood
Reexamination Certificate
2000-01-14
2003-04-29
Sykes, Angela D. (Department: 3762)
Chemical apparatus and process disinfecting, deodorizing, preser
Blood treating device for transfusible blood
C604S006130, C604S006140, C604S113000, C435S001200, C435S284100
Reexamination Certificate
active
06555057
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices and methods. More particularly, the present invention relates generally to methods, systems, and kits for protecting, perfusing, and optionally cooling the cerebral vasculature of a patient with oxygenated blood or other media.
Cerebral ischemia, i.e., reduction or cessation of blood flow to the cerebral tissue, can be characterized as either focal or global. Focal cerebral ischemia refers to reduced perfusion to the cerebral tissue resulting from a partial or complete occlusion in the intracranial or extracranial cerebral arteries, e.g., stroke, subarachnoid hemorrhage spasms, iatrogenic vasospasm. Global cerebral ischemia refers to reduced perfusion to the cerebral tissue resulting from systemic circulatory failure caused by, e.g., cardiac arrest, shock, circulatory arrest, and septicemia.
Cardiac arrest is a major contributor to global cerebral ischemia. Cardiac arrest refers to cessation or significant reduction of a patient's cardiac output and effective circulation to vital organs, most importantly the brain. Cardiac arrest can result from a number of causes, such as electrical dysfunction, mechanical failure, circulatory shock, or an abnormality in ventilation. Within minutes of blood flow cessation, tissue becomes ischemic (oxygen deprived), particularly in the heart and brain. Brain tissue is perhaps most immediately at risk, with severe, irreversible damage occurring minutes after the initial cardiac arrest. Patients in cardiac or circulatory arrest are usually treated by a combination of forced ventilation of the lungs and forced compression of the heart. Most commonly, cardiopulmonary resuscitation (CPR) is applied to the patient, with manual chest compression and mouth-to-mouth resuscitation. Advanced cardiac support (ACS) may also be provided in the form of drugs, defibrillation, and other techniques. Less commonly, open chest massage of the heart may be performed, particularly in a hospital setting where skilled surgeons may be present. Open chest heart massage is probably the most effective technique at resuscitating a patient and avoiding ischemic brain damage, but the technique is quite invasive and not available in most emergency situations.
CPR and other techniques that are directed at mechanical heart compression and lung ventilation do not usually provide adequate brain oxygenation. In addition, vasoconstrictors, e.g., epinephrine, administered during CPR are often either ineffective or given in dosages too high to produce systemic blood pressure required for cerebral perfusion. In the best cases, conventional cardiac resuscitation techniques will provide no more than 1 l/min of total blood circulation (with only about 200 ml/min passing through the cerebral vasculature) and no more than 5 to 15 mmHg of blood pressure. Normal circulation and blood pressure are 5 l/min and 80 to 100 mmHg, respectively, with about 1 l/min passing through the cerebral vasculature. Such flows are usually not adequate at normothermia. Even when CPR techniques are applied within the first several minutes of a cardiac arrest, the percentage of patients who survive without significant brain damage is very low. Significantly, most patients suffering from cardiac arrest die because of cerebral hypoperfusion.
Recognizing such problems, alternative techniques for treating patients in cardiac arrest have been proposed of particular interest to the present invention, the emergency use of cardiopulmonary bypass machines for supporting and cooling systemic circulation has been proposed. Generally, access is provided with a pair of catheters, where one of the catheters may be balloon-tipped to partition the circulation and permit the desired bypass. While such systems are theoretically effective, they do not isolate the cerebral vasculature and do not necessarily provide sufficient oxygenation of the brain. Moreover, the need to deploy intravascular catheters is time consuming and must be performed by highly skilled and trained personnel.
Surgical procedures on the aorta are required for the treatment of a number of conditions, such as aortic aneurysms, occlusional diseases, aortic dissection, and the like. Exemplary procedures include conventional aortic aneurysm repair and grafting, endarterectomy for the treatment of aortic atheroma, stenting for the treatment of aortic atheroma or dissection, and the like. Such procedures frequently require that the aorta be surgically opened to permit reconstruction or other surgical modification. Surgically accessing and opening the aorta will usually further require that the patient's circulation be arrested, i.e., blood flow through the aorta cannot be accommodated while the aorta is being surgically accessed. Cessation of systemic circulation places a patient at great risk, particularly in the cerebral vasculature where ischemia can rapidly lead to irreversible brain damage.
A number of techniques have been proposed to at least-partially protect a patient having arrested circulation during a variety of aortic procedures. It will be appreciated that conventional cardiopulmonary bypass (CABG) techniques will generally not be useful when the aorta does not remain in tact. Thus, various alternative protective protocols have been proposed.
Retrograde aortic perfusion (RAP) can be used when a procedure is being performed on the aorta between the heart and the aortic arch. The aorta is clamped beneath the aortic arch and retrograde aortic perfusion established, typically via femoral access. Advantageously, such retrograde perfusion can continue throughout the procedure since the operative site within the aorta is isolated by the clamp. RAP, however, is disadvantageous in a number of respects. In particular, retrograde perfusion often results in significant cerebral embolization from dislodgment of atheromatous material in the descending aorta and aortic arch. Such risk, as well as the limited region of the aorta that can be operated on, makes PAP less than ideal. Moreover, RAP is not useful for procedures distal or proximal to the isolated region of the aorta and is useful only at the beginning of procedures performed within the isolated aortic region.
Another approach for protecting the brain during aortic arch procedures is referred to as hypothermic circulatory arrest (HCA). HCA relies on inducing marked hypothermia in the entire body prior to stopping blood circulation altogether. Circulation remains stopped during the entire aortic procedure, thus placing the patient at significant risk of ischemia (despite the hypothermia). The patient is at further risk because the whole body has been cooled, thus increasing the duration of the surgery to accommodate the time needed to return to normal body temperature. HCA has also been associated with systemic coagulopathy (impaired coagulation) in a significant number of patients. Coagulopathy can require blood and plasma transfusion, both of which have been associated with the risk of viral infection. Aortic surgery performed with HCA has a very high morbidity, typically about 20%.
In order to retain some cerebral circulation during the time the aortic arch is accessed, HCA may be combined with retrograde cerebral venous perfusion (RCP). A catheter is placed in the superior vena cava and oxygenated blood introduced. Flow is established in a retrograde direction up the vena cava into the brachial and jugular veins. Unfortunately, very little of the oxygenated blood will reach the cerebral vessels for a number of reasons. For example, as much as 85% of the blood will enter the brachial veins and go to the arms with as little as 205 of the blood entering the brain. Moreover, the jugular venous valves may inhibit the blood from reaching the cerebral vessels. Blood that does reach the cerebral veins immediately flows outwardly through the extensive collateral circulation without perfusing the brain tissue. The amount of blood that returns to the aorta from the carotid arteries represents no more than about 5% of the total
Barbut Denise R.
Patterson Russel H.
Bianco Patricia M.
CoAxia, Inc.
O'Melveny & Myers LLP
Sykes Angela D.
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