Heart-Lung Machines

Heart, artificial Heartguard 30 Heart-lung machine Heart pacers Heart valves... 

Anesthesiology and intensive care medicine (control of blood damage in a heart-lung machine)... 

The hypothalamic temperature controller (Bl) can be inactivated by neuroleptics (p. 236), without impairment of other centers. Thus, it is possible to lower a patient s body temperature without activating counter-regulatory mechanisms (thermogenic shivering). This can be exploited in the treatment of severe febrile states (hyperpyrexia) or in open-chest surgery with cardiac by-pass, during which blood temperature is lowered to 10°C by means of a heart-lung machine. 

Current long-term mechanical support devices such as left ventricular assist devices (LVADs) require use of the heart lung machine and extensive surgery. The... 

It is indicated in hypovolaemic shock, loss of blood and plasma (e.g., trauma, burns, preoperative autologous blood or plasma donation), and for priming the heart-lung machine. In addition, it can be used as a vehicle for various drugs. 

Clark oxygen electrode. [D. t. Sawyer, A. Sobkowiak, and J. L. Roberts, Jr., Electrochemistry for Chemists, 2nd eel. (New York Wiley. 1995).] A modern, commercial oxygen electrode is a three-electrode design with a Au cathode, a Ag anode, a Ag I AgBr reference electrode, and a 50-(im-thick fluorinated ethylene-propylene polymer membrane. Leland Clark, who invented the Clark oxygen electrode, also invented the glucose monitor and the heart-lung machine. 

Recently, the ability of thin films of polytetrafluoroethylene to transmit oxygen and carbon dioxide but not water has been used to construct a heart-lung machine (Crescenzi, Hofstra, Sze, Foster, and Claff). 

Heart, embryonic development and changes at birth Heart-lung machine Heat... 

The first cardiopulmonary bypass procedure was conducted on May 6, 1953 using a heart-lung machine invented by John and Mary Gibbon [3]. Today cardiopulmonary bypass procedures are routine. Figure 23.3 shows the increase in cardiopulmonary bypass procedures in United States from 1979 to 2002 [4]. From 1995 to 2002 about 700,000 cardiopulmonary bypass procedures were conducted each year in the United States. Among these, more than 50% of cardiopulmonary bypass procedures were conducted on patients above 65 years, while 40% were conducted on patients between 45 and 64 years of age. 

Organ replacement Heart-lung machine Artificial kidney (hemodialyzer) Artificial heart Silicone rubber Cellulose, polyacrylonitrile Polyurethane... 

The need for infant heart-lung machines and their require-ments are discussed. Bubble, disk, and membrane oxygenators are compared. Membrane oxygenators are essentially non-traumatic to blood and make possible extended perfusion of the hypoxic infant. 

Thrombotic complications are frequently encountered when blood is exposed to the surfaces of hemodialysis devices, heart-lung machines, arterial grafts, artificial heart components and other prosthetic devices. The blood platelets are particularly vulnerable to these adverse effects which may include a decrease in platelet count, shortened platelet survival and attendant higher platelet turnover, and altered platelet function. However the interaction of platelets with an artificial surface exposed to blood must be preceded by the interaction of the molecular components of plasma, particularly the plasma proteins, with the surface (1,2). This is due to the prepon-... 

The most widely used heart assist device, other than the heart-lung machine routinely used in surgery, is the intraaortic balloon pump (lABP) which consists of a PEUU balloon mounted on a hollow catheter. The lABP is Inserted into the aorta via the femoral artery and is then expanded and contracted by an external pumping system to match the heart beat. While this device does provide significant Improvement in circulation and also allows the heart to rest partially after a myocardial infarction, the mortality rate is still 65-90 ( 8). 

The first recognized heart-lung machine was huilt hy Jacohi in 1895. This machine appears to have been a technical success in oxygenating the hlood, but a medical failure in terms of patient survival. 

Low-density polyethylene and polypropylene in the form of flat-sheet and hollow-fiber membranes are used in plasmapheresis and as oxygenators in the heart-lung machine. Other materials commonly used in plasmapheresis are cellulose acetate, polycarbonate, and polysulfone [129]. 

Prevention of thrombus formation is important in clinical applications where blood is in contact such as hemodialysis membranes and tubes, artificial heart and heart-lung machines, prosthetic valves, and artificial vascular grafts. In spite of the use of anticoagulants, considerable platelet deposition and thrombus formation take place on the artificial surfaces [Branger, 1990]. 

Under the tradename Copel LR Resin, silicone polycarbonates found applications ranging from oxygen enrichment membranes (including heart-lung machines), aerospace canopies and interlayers for bullet-proof glazing. They are prepared by the phosgenation of bisphenol A and chlorine terminated polydimethylsiloxane oligomer in methylene chloride with pyridine as a base acceptor (Eq. 7). 

Heparin has been used in medicine and surgery for nearly 40 years and in this time has maintained a well-earned reputation as an effective and safe drug [1]. I may claim a share in this as I was a member of the research team at the University of Toronto which developed heparin for clinical use. The major clinical uses of heparin are for the prevention of thrombosis and the prevention of clotting of blood. Thrombosis is the complex plugging of blood vessels which can occur in veins after operation and child-birth and can occur in arteries as the result of diet, age and stress. Clotting of blood is a serious problem in the use of heart-lung machines, artificial kidneys, etc. and the prevention of this by heparin is most important. My presentation reviews points about this drug which indicates its actions are due to its polyelectrolyte nature. 

The concentration of heparin in tissues from which it is isolated is about 10-50 ppm. Hence, it is a trace substance. Further it combines easily with protein. Hence, its extraction from tissue economically has required considerable ingenuity. Methods for this involve the use of concentrated electrolyte solutions and proteolytic enzymes. Standards set for this compound do not appear to meet the problem presented in identifying this compound and this is responsible for the variability that occurs. This variability is important in standardizing heparin for clinical use [7, 8]. The variations seen in activity values by different tests indicate there are probably similar variations in activity of the preparations for different clinical uses - e.g. prevention of postoperative thrombosis, prevention of clotting in the heart-lung machine, etc. 

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