Document 6bYXGRM8915N6NxvMqwYxyjp3

678 CHAPTER 64 1962 Guide And Dato Boot a trough through which cooling or warming liquids are passed from two reservoirs. The reservoir temperatures are kept at 2 C and 45 G with the flow arranged to integrate with the stage and progress of the surgical procedure. Roller pumps are used to transmit blood from an extra corporeal storage container to the body vascular system via the cooling (or warming) system, and to maintain circulation during the operation. The body temperature is reduced to about 10 C, resulting in complete cardiac cessation, as well as apparent cessation of all other vital functions. This procedure has been used suc cessfully for surgery lasting one hour or more. As noted it is used only in highly selected cases where other less drastic techniques are unsatisfactory, and is fraught with higher danger to the'patient. Many problems naturally exist in these applications of refrigeration anesthesia, being mostly in regard to patient safety, the best method of cooling (rapid or slow), optimum temperature for carrying out operating procedures, correla tion with length of operating procedure, etc. Actually all of these relate to the stage of development of the technique, and depend upon the accumulation of con siderably more satisfactory information for future success. Responsibility for the success of this anesthesia procedure rests squarely upon the physician-anesthetist who watches over the patients' vital signs before, during and following the operation. In addition to the experience needed for t.hia deli cate task, information from several recording thermometers to monitor the temperature of various areas of the body is valuable. Local Hypothermic Anesthesia Similar methods of ice poking or circulated cooling fluid are used for local anesthesia, principally for extremity am putation. The method is similar in all respects except that only the limb is encased, rather than the whole body, and a tourniquet is applied shortly after the cooling is begun, ginro the human body has great capacity to compensate for local external temperature changes. General anesthesia is not re quired. Refrigeration usually takes two to four hours for the production of anesthesia, depending on the area to be anes thetized. When ice alone is used, frostbite does not generally occur, and the skin temperature does not usually fall below 4 C. Care must be taken with mpnhanirAl refrigeration that. these conditions are reproduced. This type of anesthesia 'is usually reserved for the elderly or poor risk patients, who have additional ailments which preclude the use of other anesthesia. In summary, it may be stated that hypothermia may be induced locally, or applied to the entire body, inducing an algesia (Insensibility to pain). Current interest in physiolog ical problems and clinical application is responsible for con tinuing study. Although knowledge of this subject is far from complete, it is apparent that general hypothermia: 1. May be induced by cooling the blood stream or cooling the body surface. 2. Dangerously enhances ventricular fibrillation (independent heart muscle fiber action resulting in incoordinate contraction) in man, especially at temperatures below 25 C. 3. Depresses the respiratory center. 4. Lowers pulse rate, blood pressure and output. 5. Is reversible by rewarming, if not carried below level. critic^ REFERENCES 1 L. C. Gage: Hospital refrigeration needs (Industrial Refru^. ' Bon, August 1957, p. 30). * S. W. Chase and C. H. Herndon: The fate of autogenous aorf homogeneous bone grafts (Journal of Bone and Joint Sura**!. Vol. 37-A 1955, p. 809). ^ * P. H. DeVries, L. L. Kempe, and W. 0. Btinker: Sterilisation of Bone Transplant* by Cobalt-60 Radiation (University of Mirk; gan Medical Bulletin, VoL 21,1955, p. 29). Q1" * R- A. Kilduffe and M. DeB&key: The Blood Bank and ike Technique and Therapeutics of Transfusions (C. V. Mosbv Pnk. Ushers, St. Louis, 1942). * E. L. DeGowin, R. C. Hardin, and J. B. Alaever: Blood Transfusion (W, B. Saunders, Publisher, Philadelphia, 1949). * R. L. de C. H. Saunders: Preservation of cadavers by plastici zation (Anatomical Record, VoL 115, 1953, p. 43). 1 W. 0. McQumston: Anesthesia in cardiac surgery (ilnAum OfSurgery, Vol. 61,1950, p. 892). * F. J. Lewis and M. Taufic: Closure of atrial septal <W<w. (Suraen VoL 33, 1953, p. 52). * J. W. Dundee, T. C. Gray, P. R. Mesham, and W. E. B Scott: Hypothermia and autonomic block in man (British Medi cal Journal VoL H, 1953, p. 1237). ** C. E. Drew, G. Keen, and D. B. Benazon: Profound hypo thermia (Lancet, VoL I, 1959, p. 745). BIBUOGRAPHY W. H. L. Domette: The use of temperature monitoring devices in anesthesia (Anesthesia and Analgesia Current Researdies. VoL 35, 1956. p. 584). B. Fisher, C. Adams, R. Wilde, and E. R. Fisher: The steriliza tion and storage of lyophilized blood vessels (Annals of Surgery Vol. 143, 1956, p. 73). * E. W. Floadorf: Freeze-Drying (Reinhold Publishing Co.. New York, 1949). E. W. Floadorf and G. W. Hyatt: Preservation of bone grafts by freeze-drying (Surgery, VoL 31, 1952. p. 716). E. R. Hipp and G. R. Minor: A freeze-dried artery bank (Ftrpurio Medical Monthly, Vol. 82, 1955, p. 125). R. E. Horton: Storage and use of arterial grafts (Brifuft Journal of Plastic Surgery, Vol. 7, 1955, p. 9). T. Komoda and M. Morito: Experimental study on the speci men contamination in electron microscopy (Journal of tSlec- tronmieroscopy, VoL 9,1960, p. 77). H. B. Lehr, W. S. Blakemore, P. N. Sawyer, F. Clauser, and J. Johnson: An apparatus for the preparation of homologous arterial grafts by freeze-drying (Surgery, VoL 37, 1955. p. 576). H. T. Meryman: Freezing and drying of biological materials (New York Academy of Sciences, I960). W. W. Mnshin: Anesthesia for the Poor Risk (C. C Thomas Publishers, 1948). J. P. Reidy: Homogenous bone grafts (British Journal of Plastic Surgery, Vol 9, 1956, p. 89). L. R. Sauvage, S. A. Wesoiowski, and R. D. Pine: Review of the principles and description of manifold type vacuum systems (Surgery, VoL 37, 1955, p. 585). E, T. Smith: Five years experience with refrigerated bone (Southern Medical Journal, Vol. 49, 1956, p. 704). E. W. Floadorf: Chapter on quick freezing and freezing-drying process (Biophysical Research Methods, F. M. Uber, editor. Inter science Publishers, 1950)- R, W. Virtue: Hypothermic Anesthesia (C. C Thomas Pub lishers, 1955). 8. A. Wesoiowski, L. R. Sauvage, and R. D. Pine: Quantitative observations during the freeze-dry processing of arterial segments (Journal of Thoracic Surgery, Vol. 30, 1955, p. 9). CHAPTER 65 CRYOGENICS liquefaction af Helium; Liquefaction of Hydrogen: Problems and Properties, Liquefaction Cycles and Equipment} Measurement of low Temperatures; Thermal Insulation.- High Vacuum Reflective Insulation, Conductivities of Supports, Multiple layer Insulation, Unevacuated Porous Insulations, Evacuated Powders, Rigid Foam Insulation; Properties of Structural Materials: Spedflc Heat, Thermal Expansion, Thermal Conductivity, Mechanical Properties; Cryogenic Fluid Properties ALTHOUGH man has been interested in the nature of f\ things at very low temperatures from early times it was about the first of the 20th century that any real inves tigations were made. The liquefaction of hydrogen (--423 F by James Dewar in 1898) followed soon by the liquefaction of folium (--452 F by Kftmmprling Onnes in 1908) made it p^cgihlp. to study nature near absolute zero (--460 F). Before this it was possible to reach temperatures only as low as -300 F to --350 F n"ng liquid air or one of its primary constituents; oxygen or nitrogen. Up until World War 11 research and development in the field of cryogenics were carried on only in a few of the major universities in the United States and Europe and in a few government laboratories. A great upsurge in cryogenic re- eearch took place about 1947. This was made passible, partly by the helium fiquefier (developed by S. C. Collins at Massachusetts Institute of Technology) and partly by the growing interest in uses of liquefied gases. The few commer cial interests in thin field up to this tune were primarily centered in production nnd uses of liquid oxygen and liquid nitrogen.- This area dm has exhibited a tremendous expan sion in tiie last fifteen years. As a result of investigations, developments, and increased interest in applications in the very low temperature ranges, the new field of cryogenic engineering has emerged. It is gen erally associated with the development, production, and use of equipment in the temperature range of --250 F to near absolute zero. It includes the measurements of properties of mginAorirtg materials; nhfimie&l and physical processing of bases; the liquefaction of gases; pumping, transport, storage aod use of liquefied gases; and development of a wide range of equipment., instruments, gadgets, and techniques for such work. Probably the most important field of application for cryo genics today is in the iwlaale and rocket industry for defense and space programs. There are many other important de velopments, however, that have accounted for the great interest in this fipld and its growth to a billion dollar a year industry. The name cryogenics was coined from the Greek, cryo(Fryos) meaning icy cold, and genic (genes) to become or produce. It is appropriate in that it refers to the coldest area known in nature. Fig. 1 illustrates this temperature range, separating it from the range generally referred to as ultra low temperature. This chapter presents the fundamental principles and con siderations in the liquefaction of helium and hydrogen as com pared to the simple Linde cycle used in the liquefaction of air or either of its constituents, nitrogen or oxygen; describes the haaift methods of temperature measurement in the cryo genic temperature range; covers the principal methods of in sulation "d temperature isolation; and discusses the basic properties of many engineering materials at low temperatures. The chapter also includes a number of tables and graphs of of cryogenic data that are considered most helpful to the re frigerating engineer who may occasionally encounter prob lems in the cryogenic engineering range. LIQUEFACTION OF HEUUM The normal boiling point of helium is 4.2 K (--452.1 F) And the critical temperature (the highest temperature at which the liquid ph can exist) is only 1 K deg (1.8 F) higher. Other properties of helium are indicated in Figs. 2 and 3, in the temperature-entropy diagram of helium Fig. 2, linA* of constant pressure and constant enthalpy have been ftddqd "nd in Fig. 3 linas of constant temperature have been superimposed upon an enthalpy-pressure diagram. Many ordinary refrigerants condense at room temperature * 52 F O -44 r\ ICC - PROFANE - IO - 127 - 159 - * - ETHANE -- ETHYLENE -258 -297 -515 --SCO THANE OatYOEN AIR; CO NITROGEN fig. 1 .... Cryogenic Thermometer Showing Normal Boiling Temperatures At Atmospheric Pressure 679