Document rBJKxOJVmRMqOzdLNpbZVE1bV

676 CHAPTER 64 1962 Guide And Data Book the personnel who operate such a laboratory are generally extremely careful in processing these dangerous materials so that the probability of contamination and subsequent infec tion to the uninitiated should be quite remote'. BLOOD BANKS The successful operation of a blood bank depends on ade quately satisfying three major factors: procurement, storage and the laboratory technical skill to assign blood properly to the recipient. It is fairly obvious that the last of these in volves the largest amount of continuously applied human ability which depends in turn upon a good supply of available donors and satisfactory storage or banking facilities or both for successful performance and service. The factor of storage will be discussed. ' The technique of blood banking as recognised today is relatively recent and dates in this country to the organisation of the first blood bank at Cook County Hospital in Chicago in 1936. With the development of improved preservative solu tions, allowing blood to be stored safely and effectively for 21 days following withdrawal from tire donor, the blood banking concept spread rapidly and today almost every hospital or medical institution involved indirect patientcare has a blood Hank. literally millions of transfusions have now been given and with this remarkably simple means of providing whole blood at a moment's notice, other procedures and the use of dried plasma and other blood volume expanders presently represent a very small percentage of average hospital usage. The blood storage procedure is relatively ample and by and large depends upon standard refrigeration equipment! The size of the institution or area to be served by the blood these is the walk-in unit with compressor, refrigerating cod and blower of appropriate size and convenient location; the second is a complete unit manufactured for installation consisting of an insulated outer aheii containing slide drawers or shelves suspended in Ferris-wheel fashion. The walk-in type unit is generally the most satisfactory depending of course on the anticipated volume of occupancy. It is equipped with wooden or stainless steel shelves measur ing 2 -- 2M X 7 ft, suspended on wall brackets along the length of the chamber. It is customary to place the shelves in two or more tiers to make the most efficient use of the avail able space. The usual type of walk-in refrigerator door is used and the sill-less type is preferred to facilitate movement in and out of wheeled stretchers. A tile or other impervious floor should be laid and a drain of suitable size is essential to enable easy hosing down or other cleaning. The second type of installation is used for very large med ical facilities or small hospitals which anticipate a maximum accommodation of two or four bodies. These units consist of individual compartments with longitudinal slide drawers measuring about 2*4 X 7 ft. Temperatures are usually in the 4 to 6 C area with enough latitude in the refrigeration apparatus to maintain this temperature while cooling the maximum capacity of -the unit. Maximum storage time does not usually exceed 72 hours, and if longer storage is contemplated, embalming is usually instituted. If facilities for embalming are not readily avail able, deep freezing may be resorted to as a preservative meas ure if appropriate medico-legal or other studies are antici pated. bank usually determines the type of equipment. For example, a large medical center may have a good sized walk-in refrig erator to bank its blood and keep the stock of typing sera and other accessories to the blood assignment process. In addition there may be a large refrigerator, generally two-door, of standard dimensions and construction, in which the blood that has been prepared for and assigned to individual pa tients is kept until requested for use by the physician. Variants of this arrangement will be seen in practically every blood bank. Blood bank refrigerators should be equipped with forced air circulation, a dependable and sensitive thermostat, an alarm system and a recording thermometer. The recom mended temperature is 4 to 6 C. Certain principles of blood bank refrigeration are listed by Kilduffe and DeBakey.4 These include in addition to the prescribed warning signals and recording thermometers, a suggestion that the refrigerator be operated on a separate cir cuit to minimize power failure from mishaps in other ap paratus. Also it is recommended that the equipment be in spected and tested regularly by expert maintenance personnel Simple devices called refrigeration indicators are described by DeGowin and Hardin.1 These devices rely on a principle of melting points of certain fatty acids which liquefy at room temperature or slightly below permitting colored glass beads to change position in a glass container thereby informing the observer of upward deviations of temperature. These simple indicators would serve a purpose in some areas, but would be unacceptable in blood banks, since more reliable recorders exist. Cadaver Preservation and Storage The use of refrigeration as an integral part of cadaver preservation and storage follow toe pattern of refrigeration wherever large objects are to be kept cold for varying pe riods of time. Actually the demand for this sort of application is limited largely to medical schools or other institutions where human or animal anatomical studies are made. Re frigeration is needed subsequent to suitable embalming or other preparation. With the increasing demand for cadavers for medical teaching and study, coupled with the increasing difficulty of procurement as a result of some of the social and economic adjustments of the past, equipment for long term adequate storage is essential. This is not a field that has stimulated extensive literature, but the basic principles are well understood by those in terested or involved in this subject, and each institution prob- ably has its own modifications to suit its needs or views. Saun ders* presents a detailed description of one type of refrigera tion application to this problem which fulfills the needs of his particular situation. In this case the refrigerator is con structed with removable shelves, similar to that described under morgue refrigeration. A variant of this method in use in many medical institu tions involves the principle of suspending the cadaver by a tongs or head harness attached by a chain to a wheeled trolley. The trolley in turn runs on an overhead track which proceeds from above the embalming table into the refrigera tor, enabling one attendant to move toe cadaver about with ease. This involves an aperture in or above the refrigerator door to accommodate the track. PATHOLOGY AND ANATOMY LABORATORIES Morgue Refrigeration Refrigeration is supplied by a suitable built-in cooling unit and blower, or more than one as the situation demands. It o estimated that a room 12 X 40 X 8 ft will accommodate 100 Medical center or hospital morgue refrigeration is usually accomplished by one of two types of construction.-The first of cadavers. The desired temperature is 2 to 3 C. The walls, ceiling and floor should be well insulated and painted with * light colored water repellent paint. A tile or terraszo floor13 Medical Applications 677 --tfactory and a drain or drains in the floor should be proto facilitate cleaning. The suspended cadavers are _.Aiiy encased in plastic bags, or sprayed with a vinyl resin baring moisture resistance as well as bacteriostatic and fgogistatic qualities. The refrigeration aspects of this ar rangement amde from some unpleasant aesthetic considera^3 ^ similar to those in industrial or other large room refrigeration ventures. It is sometimes advantageous to provide a deep freeze room as part of this major cadaver storage for the preservation of rertain unembalmed materials to be kept for further study. Hus iixt should be contrived as a room opening into the larger storage area with a deep freeze type door and equipped pith a cooling system and blower to provide a temperature of about --20 C. Usually a space of approximately 8X8X8 (t lined by 12 in. wall shelving at convenient intervals to the will suffice and allow for segregation and cataloguing of the specimens. REFRIGERATION IN CLINICAL MEDICINE Medical applications of refrigeration are confined largely to laboratories as indicated above. Clinical medicine which is ffpnr^mad with the immediate diagnosis, treatment and care of the patient by the physician has used direct refrigeration very sparingly, confining it hugely to the traditional ice pack for sprains, headaches, and other local analgesia, and the use of solid CO* in the removal, of certain skin blemishes. Recently a whole new field of clinical refrigeration--hypo thermic anesthesia--has been opened and is presently under intense exploration. Hypothermic Anesthesia In 1950, McQuinston7 introduced the concept of lowering the body temperature during anesthesia to reduce oxygen demand, especially in children undergoing cardiac operations. First use of hypothermia in open heart operations was re ported by Lewis and Taufic* in 1953, and was employed in the closure of atrial septal defects (communicating holes in heart chambers). In 1953 also, Dundee et al* set forth a series of indications for hypothermia including (1) the desirable hypotension (low blood pressure) to control hemorrhage for either the patient or for the surgeon because hypothermia might more safely lower the pressure and also diminish the oxygen demand, (2) patients with severe anemia which could not be corrected preoperatively, (3) operations on the heart aod great vessels in which cerebral circulation may need to be stopped, (4) thyrotoxicosis (excessive activity of the thyroid gland) which could not be controlled by medical treatment, (5) neurosurgery, and (6) hyperpyrexia (high fever) of pituitary (gland) or post-operative origin or in thyroid crises. It has been used in anumber of difficult major procedures in poor risk patients. The hypothermic state is produced in three ways:.by im mersing the anesthetized patient in ice water; by surround ing the patient with plastic bags containing flaked ice; and by cooling the patient with water-antifreeze admixture, pre cooled by refrigeration, and pump-circulated through a tube coiled within a rubber blanket which surrounds the patient. The first method using immersion in ice water requires 30 to 60 min for effective cooling. Temperature continues to. drop After the patient is removed from the tub, and the continuing fall is approximately H as much as that which occurs while the patient is in the ice water. This ratio, however, is not constant, a disturbing factor not solved to date. The patient u ordinarily left in the tub until the temperature has dropped about 60 percent of the desired value to about 31 G, effecting a final temperature of about 27 C. Continuous electrocar diography (tracing of heart electric potentials) is employed to provide information regarding the condition of the heart of the patient throughout the procedure. Pulse rate and blood pressure decrease as the patient cools. Shivering is controlled by relaxing drugs such as curare or cyclopropane anwgihwrin. When the patient's temperature reaches 30 to 28 C, toe need for further anesthetic agents is markedly reduced. When the estimated temperature is achieved (60 percent of toe desired fall) the patient is removed from the ice water thoroughly dried with bath towels. The patient is then care fully and protectively wrapped. In some cases diathermy coils are carefully applied to the hips and abdomen, to be used to avoid a dangerously low temperature or stand ready for prompt warming in the event of weakening*of the heart. Its greatest use is to warm toe patient at the conclusion of the operation. Warm water immersion can also be used for this latter purpose. The second method using plastic bags containing flaked ice is also satisfactory and the general principle is the same. It is not quite as rapid as the immersion method, but faster than toe third method which uses the precooled circulating fluid. To be most effective the bags must be placed all over the body, covering all but the face. An important feature of this method is an adequate source of flaked ice. The last method mentioned involves toe use of a mobile apparatus which has both heating and cooling units, as well as a fluid tank and a circulating pump. The machine operates on toe principle of compressor and coil cooling of a water-antifreeze mixture in the built-in tank. This cooled mixture is then circulated by a pump through a rubber blanket, which is inlaid with rubber tubing forming a continuous connected U pat tern, similar to the wiring of an electric blanket. Sponge rub ber cylinders of diameter equal to that of the rubber tubing fill the interstices between the tubing as it undulates through the blanket. The tank of water is large enough to supply continuous cooling to two of these blankets, laid underneath and on top of the patient and joined laterally by zippers. The blanket thus surrounds the patient's body and is further covered by wool blankets to provide additional insulation. This system will drop the temperature of a small child about 1 deg C every 6 min, and of the adult about 1 deg C every 24 min. Precautions regarding continuing downward tempera tures are similar to those described above under toe ice water immersion method. The first two methods are faster although the last method has many advantages of convenience and ease of application. This same unit may also be used for warming toe patient. The heating unit is activated and the fluid mixture warmed and circulated through the blanket. The top blanket is re moved during the operation, although some models have longitudinal slits which may be opened and through which the operation may be accomplished. Recent problems with extracorporeal circulation relating to maintenance of a satisfactory safe level for an appropriate time interval have led to development of a system of very rapid deep hypothermia for special cases nmng a heat ex changer in which body core temperature can be reduced ap proximately 1 C deg per minute. The heat exchanger as described by Drew et alt0 consists-of* four stainless-steel tubes 04 inch internal diameter), each of which is five feet in length and highly polished on the inside. The tubes are arranged in parallel and connected together with Y-shaped stainless steel connectors and short lengths of polyvinyl ethylene chloride tubing. (This arrangement is preferred to a coil because it offers less resistance and the straight tubes are easy to clean.) The tubes are suspended in