- Email: [email protected]
U.S. Army surgical research program
U.S. Army Surgical Research Program Recent Progress and Current Interests D. C.
LTC. LOUIS F. PLZAK, Jr., Washington, COL. LAWRENCE R. ROSE, Washington, MAJ. GEN. JOE M. BLUMBERG,
Washington,
LTG. LEONARD D. HEATON, Washington,
The primary objective of the Army Medical Research and Development Command’s Surgical Research Program is to improve the care of interest is wounded soldiers ; our primary trauma, its effects, and optimal treatment. This broad objective necessitates our participation in many areas of related research. Our basic programs are intended to provide fundamental knowledge and to devise experimental approaches necessary to initiate or expand applied research on problems of obvious military significance. Improvements in the care of combat casualties require a basic understanding of the effect of trauma on the patient and of the mechanism by which various modes of treatment affect the recovery response. Our program is about evenly distributed between extramural contractors, who primarily contribute basic research to our program, and intramural work at relatively less basic and clinical levels. Our program in laser research is an example of our effort to document and evaluate the effects of various types of trauma. Laser investigations conducted by a joint U. S. Army Medical Research and Development Command -U. S. Army Material Command Laser Safety Team at Frankford Arsenal are concerned with the formulation of safety criteria for the employment of military laser devices and laser systems. The remainder of the program is exploring problems of repeated exposure to lasers, wave length-specific effects, long-term effects of laser injury, and changes in cell function at subthreshold energy levels. From the Shock and search Division, U. velopment Command,
356
Trauma Research Branch, Surgical S. Army Medical Research and Washington, D. C.
ReDe-
D. C.
D. C.
D. C.
Our program in anesthesia is an example of a continuing effort to evaluate the adverse effects as well as the beneficial effects of various treatment regimens on the casualty. This information contributes to our development of therapy with minimal “cost” to the patient. We are continuing to support studies on the effects of anesthetic and vasoactive agents on renal, hepatic, and myocardial flow and function in normal and hypovolemic subjects. In hypovolemic states the depressant cardiovascular changes are accentuated by both spinal and epidural anesthesia. Therefore, although epinephrine usually is added to a local anesthetic solution to decrease the rate of absorption of the agent and to offset cardiovascular depression in normal subjects, this supplementation is mandatory when spinal or epidural anesthetics are used during hypovolemia [I]. An ideal anesthetic for field use would not only need to be completely safe, but also require only simple and easily operated equipment, provide rapid onset and recovery, and leave no residual disability. One approach to these requirements is an electrical anesthesia device which is now being evaluated- in primates [Z]. This equipment can achieve a surgical level of anesthesia within three minutes of onset, there is no interference with the cardiorespiratory paramand coordinated motor function reeters, turns within two minutes of its termination. Prior to evaluation of this device in man, its effects on conditioned behavioral responses (executive monkey) and brain histology are being studied after single and repeated exposures lasting from thirty minutes to ten hours. The blood preservation aspect of our proThe
American
Journal
of Surgery
U.S. Army Surgical
gram is concerned with defining the optimal conditions for storage in which the deterioration of blood is minimized. We are concerned not only with the survival of the formed elements but also with the maintenance of their function. The metabolic reactions responsible for maintaining viability are being defined. Adequate ATP levels in the erythrocyte are essential to the maintenance of the integrity of the cell membrane. The addition of adenine and/or inosine to the storage medium will regenerate the intracellular ATP levels ; we are studying the optimal concentration and timing of their addition [3] as well as their metabolism and toxicity 141. Studies of the cell membrane have revealed a decrease in total lipid with senescence; once these alterations have occurred, they are not reversed even when adequate ATP levels are restored by the addition of adenine [5]. Membrane defects increase cellular permeability to calcium which is associated with irreversible erythrocyte contraction. The oxygen dissociation curve of blood stored beyond ten to fourteen days shifts to the left IS]. These erythrocytes do not readily release oxygen which may result in deficient tissue oxygenation. It has been noted that when intracellular phosphate as 2,3-diphosphoglycerate (2,3-DPG) is bound to hemoglobin, this binding results in decreasing the affinity of oxygen to the hemoglobin molecule (71. The level of intracellular 2,3-DPG is regulated by cellular metabolism. A deficiency of 2,3-DPG has been noted in stored blood which can be replenished by the addition of phosphate [8]. Further work is being carried out to optimize the oxygen dissociation curve of transfused blood. Fortification of standard ACD preservation solution with adenine alone will permit the extension of the shelf life of blood from the current three week limit to five or six weeks with acceptable survival rates; it provides metabolically and functionally superior erythrocytes at all periods of storage 19,101. A team recently established at the 93rd Evacuation Hospital, Vietnam, has been conducting a clinical evaluation of ACD-adenine blood in a field environment. Although in the past we have oriented our work toward the erythrocyte, we are now broadening our approach to consider the prevention of storage damage to other blood constituents, such as platelets and coagulation factors, which are Vol. 118, September 1969
Research
Program
also essential in the resuscitation of patients in hemorrhagic shock. Plasma substitutes are used for emergency treatment of hemorrhagic shock, but concern due to allergic reactions, viscosity changes, and coagulation defects has restricted their use. Hydroxyethylstarch (HES) is a plasma expander possessing minimal antigenicity, although, like dextran, it interferes with the clotting mechanism. Recent studies demonstrate that its lower molecular weight fractions do not increase blood viscosity and do not interfere with the microcirculation and tissue oxygen consumption [ll]. Current data suggest that clotting problems may be related to the molecular weight of the fraction, and we are continuing our efforts to improve the separation of HES into sharp molecular weight fractions for further evaluation. A hemoglobin solution free of stromal material has been shown to function as a plasma expander and oxygen carrier [121. Initial studies confirm the absence of renal toxicity and the lack of interference with coagulation factors. We are currently studying the efficacy of the hemoglobin solution in hemorrhagic shock, its effect on primates with pre-existing renal disease, its influence on viscosity, its antigenicity, and its ability to oxygenate tissue. Various polypeptides, comprised of an ordered sequence of alpha-amino acids, are being synthesized. They are capable of expanding the circulating blood volume and are essentially nonantigenic. We anticipate that the knowledge of the structure of these synthetic materials will enable us to understand the relationship between specific chemical configurations and effects on clotting, viscosity, and antigenicity. Basic work on the immunogenicity of polypeptides complements our transplant program which is primarily directed toward understanding the basic immunology of transplant antigens. An immunoregulatory alpha-globulin isolated from fraction IV of normal plasma is being characterized and studied as to the optimal time, dose, and route of administration for maximal immunosuppressive effects [13]. It ap,pears to inhibit macrophage migration by its reaction with lymphocytes producing macrophage immobilization factor. The feasibility of using the inhibition of macrophage migration as an in vitro indication of the immunologic status of a graft recipient is in progress. Anti357
Plzak et al.
sera to viral endotoxins may exert an immunosuppressive effect [14] ; attempts are being made to define this mechanism of suppression and to establish a system for predicting the antigenic effect of endotoxin. Improvements in organ preservation technics are also basic to any transplant program. We have recently initiated the support of two studies on the preservation of organs, one relating to the effects of temperature changes on cellular metabolism and preservation and the other investigating the feasibility of using extremely high pressures (10,000 to 15,000 p.s.i.) for freezing point depression in order to provide uniform freezing and thawing of tissue undergoing storage. The work on basic immunology and tissue preservation is also related to our interest in burns. The value of skin grafting in early burn therapy has been clearly shown ; we are now expanding our attempts to provide materials, both natural and synthetic, which might be suitable substitutes for homografts. The use of Sulfamylon@ ointment, a topical antibiotic developed by the U. S. Army Institute of Surgical Research (ISR) at Brooke Army Medical Center, contributes to our decreased burn morbidity and mortality. We are continuing our search for improved analogs of Sulfamylon with less toxicity and greater antibacterial potency as well as for other antibacterial agents. An analog of Sulfamylon has been synthesized at ISR which is free of carbonic anhydrase inhibition and shows satisfactory antibacterial activity. Carbenicillin@ (disodium-acarboxyl penicillin) has produced encouraging results when used either topically or systemically for Pseudomonas burn wound sepsis in animals. It has been demonstrated to be effective in the control of established burn infections. Important new areas of concentration have emerged with the subsidence of burn wound sepsis as the primary cause for mortality from burns. These include melioidosis, septic thrombophlebitis, and gastrointestinal hemorrhage. Metabolic requirements and respiratory problems in burns continue to represent an important area of investigation. Our shock and trauma program supports studies evaluating the effect of hypovolemic and endotoxic shock on cellular and tissue changes. These include effects on cardiopulmonary function, blood viscosity and the microcirculation, tissue oxygen consumption and 358
metabolism, and tissue structure and function. Studies in dogs and primates are correlating pulmonary ultrastructural changes induced by shock with alterations in circulation, function, metabolism, and surfactant. Work continues to characterize the serum lipid and protein alterations seen in shock and to relate these changes to pathologic changes seen in the lung. Laboratories studying the effects of various types of therapy, including resuscitative fluids, splenic extracts, ganglionic blocking agents, steroids, and immunization, are being supported. Denervation of the spleen has been found to protect dogs from lethal endotoxic shock [IS]. Carboxylic esterase isolated from the spleen appears to be responsible for this protection ; its mechanism of action is being studied. Protection from endotoxic shock also has been achieved by the use of an antiserum obtained by the isolation of core antigens from gram-negative bacilli. Another aspect of this work is the development of a method for the early identification of endotoxic shock. The Walter Reed Army Institute of Research, a laboratory in the U. S. Army Medical Research and Development Command, has a surgical research team at the 24th Evacuation Hospital in Vietnam and also had an exploratory surgical research team at the 249th General Hospital in Japan. Much of the emphasis of our program is based on studies made by these teams. The ability of our teams to bring sophisticated laboratory technics to the field hospital has provided us with a unique opportunity to study selectively the effects of massive trauma and current therapeutic regimens in a relatively homogeneous population. The infrequency of pre-existing medical p’roblems in our casualties simplifies the analysis of our data. The most common cause of respiratory insufficiency in Vietnam is penetrating chest injury. The physiologic aspects of the changes resulting from chest injuries was studied by Moseley, Doty, and Pruitt [16,1?‘]. The average admission pOg for thirty-six patients studied was 6’7 mm. Hg, the pCOz 38 mm. Hg, and the pH 7.38. Pulmonary shunting was evaluated during various treatment regimens in eight of these patients. An initial shunt of 44 per cent was reduced to 27 per cent by breathing 100 per cent oxygen and to 14 per cent by the use of a volume cycled respirator. Decreased pulmonary shunting was associated The American Journal of Surgery
U.S. Army Surgical Research Program
with a decreased cardiac index. Although the oxygen consumption remained essentially the same in these patients, the lactate was decreased and clinical improvement was noted. Therefore, this assistance probably enabled the oxygen-starved peripheral tissues to obtain more oxygen. Twenty-seven critically ill patients with hypoxemia (pOa average, 47 mm. Hg; range, 19 to ‘71 mm. Hg) were selected for serial cardiopulmonary function studies. An increased cardiac output was observed to follow severe trauma associated with respiratory insufficiency unless blood volumes were depleted by more than 20 per cent. The hyperdynamic circulatory state is thought to be due to the functional shunting of blood in the pulmonary and peripheral circulations ; this is well tolerated for prolonged periods in previously healthy persons if hypoxemia can be controlled. Doty, Hufnagel, and Moseley [18] studied the distribution of body fluids as a function of resuscitative therapy. Eight of thirteen patients studied received large transfusions (average 6,350 cc. blood and 5,390 cc. Ringer’s lactate solution). Early in the postresuscitation period (one hour) the total body water was decreased by 2 L. (-10 per cent) and the erythrocyte volume by 1 L. (-33 per cent). At seventy-two hours there was a marked increase in extracellular water and plasma volume with a normal total body water. The red cell mass remained depleted at this interval. The extent of under transfusion is usually proportional to the amount of blood transfused. The high level of extracellular water may be due in part to sequestration and in part to the generous use of Ringer’s lactate solution during the resuscitative period. Intravascular microaggregation has been studied by Berman et al. [19,20] in Vietnam using a modification of Swanks screen filtration technic [Zl]. Blood is passed through a tube containing a sereen with a pore size of 20 p at a fixed rate. The pressure generated proximal to the screen is measured. A series of eighty-nine casualties with moderate to severe injuries of the extremities, abdomen, and/or thorax were included in the study. Arterial and venous screen filtration pressures (S.F.P.) were measured and correlated with blood gases, lactates, and base deficits. S.F.P. was elevated in 60 per cent of the ‘patients. Ninety-five per cent of the casualties with elevated arterial and venous S.F.P. had fractures or blast injuries; Vol. 118, September 1969
almost all of these were hypoxemic (~0, < 75 mm. Hg) on admission or shortly thereafter. No fat was noted on the screens. Although blood stored more than five to seven days will elicit an increased S.F.P. ; arterial samples obtained from patients immediately after receiving up to 60 units of this blood gave normal screen filtration pressures. It is postulated that these microemboli filtered out by the lung contribute to post-traumatic pulmonary insufficiency. At present Major Berman is correlating the changes in microaggregation measured by S.F.P. with blood viscosity. The in vitro addition of 5 mg. per cent of ADP (comparable to plasma concentration during storage) to a platelet concentrate will cause an increased S.F.P. (39 to 300 mm. Hg). The association of arterial hypoxemia with altered blood viscosity and the presence of certain vasoactive substances (ADP, serotonin) is also being studied in the postoperative period. Two patients dying of respiratory insufficiency shortly after sustaining severe wounds and receiving massive transfusions had clots scattered throughout the small pulmonary arterioles at postmortem examination. This prompted Moseley and Doty [ZR] to study the blood infused into 120 battle casualties in Vietnam for the presence of clots. Two standard blood filters, designed to retain particles greater than 170 p, were placed in series in the infusion line. The clotlike material obtained on the first and second filter was weighed and correlated with the age of the blood and the number of units of blood previously passed through the first filter. The amount of clotlike material obtained in the first filter increased with the duration of storage; there was a marked increase in the amount of material passed through the first filter when more than 3 units were infused through the same filter. Henry, Matsumoto, and Hayes IZS] studied the effects of aeromedical evacuation on 102 patients transferred from Vietnam to Japan in an Air Force Cl41 aircraft. The duration of the flights averaged four and a quarter hours. Seventy-two patients were studied on four flights at a cruising altitude of 37,000 feet and a cabin altitude equivalent to 6,700 to 7,200 feet. Serum and urine osmolalities, hematocrit, and blood gases were obtained eight to nine hours prior to departure, thirty minutes after takeoff, thirty to sixty minutes prior to land359
Plzak et al.
ing, and finally immediately after landing. The patients most severely affected by the altitude were those with fractured femurs, fractures of the lower extremities, and chest injuries. Forty-eight seriously injured casualties had an initial p0, of 76.5 mm. Hg which fell to 49.6 mm. Hg in flight and returned to 76.8 mm. Hg on landing in Japan. Coinciding with this hypoxemia is a lowering of the pC0, and a rising pH. Except for the chest injury casualties, the patients in each group demonstrated some ability to compensate for the inflight hypoxemia by increasing their respiratory and pulse rates. The flights at cruising altitudes of 25,000 to 27,000 feet (cabin altitude 3,000 to 3,800) were better tolerated by all groups. The serum osmolality verified the presence of an adequate state of hydration in the patients. There was a significant correlation between low hematocrit, low red blood cell mass, low serum osmolality, and the hypoxemia observed in patients from all groups. This is consistent with the hypothesis advanced by Gutierrez, Berman, and Aaby [24] that low intravascular osmolality may contribute to increased pulmonary exudation and respiratory insufficiency. The effect of altitude on pre-existing pulmonary shunting needs to be defined. It is anticipated that these studies will contribute to the establishment of better criteria for the safe evacuation of wounded troops. A survey of the bacteriologic aspects of wound infections revealed a preponderance of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Most positive blood cultures are due to gram-negative organisms, primarily Ps. aeruginosa and KlebsieIla pneumoniae. This information and sensitivity data are being used to assist in the selection of a suitable topical antibiotic for field use. Local antibiotic therapy for wounds is being developed, not as a substitute for debridement, but as a means of retarding bacterial growth and thereby prolonging the period during which debridement can safely be delayed. Most wounds are closed four days or more after initial debridement. Clinical judgment as to the proper time for delayed closure may be in error due to unrecognized residual sepsis. Premature closure not only is dismaying to the surgeon, but also causes considerable distress to the patient. Matsumoto et al. [25] have studied the problem of the optimal time for de-
layed closure of soft tissue injuries by examining the relationship of lactic dehydrogenase, serum glutamic exalacetic transaminase, and creatinine phosphokinase (CPK) titers to residual infection. Of the enzymes studied, there appeared to be a correlation of infection only with the CPK titer. CPK is released from muscle destroyed by infection. Since Ps. aeruginosa readily causes local infarction and thrombosis with resultant muscle damage, an elevated CPK titer is a particularly sensitive indicator of the presence of this organism. Four wounds that clinically appeared ready for closure were subsequently noted to have had an elevated CPK at the time of closure; these did not heal satisfactorily. Healing was normal in thirty-three patients in whom the CPK levels were within the normal range at the time of secondary closure. These recent studies by our research teams in the field are examples of the type of data which contributes to the orientation of our more basic programs. These studies are also based, in part, on the work emanating from these more basic investigations. The biochemical phenomena of wound healing are being studied in animals and in man utilizing subcutaneously implanted wire mesh cylinders. Neurosurgical laboratories are evaluating the effects of concussion on spinal cord function and circulation and the comparative value of treatment by decompression, hypothermia, and steroids. We are continuing to support work designed to improve the results of peripheral nerve repairs. The beneficial effects of cooling and then retransecting cut nerves prior to anastomosis and the use of silicone sleeves around the anastomosis have been clearly demonstrated. Improved methods of preparing, preserving, and employing nerve grafts are being developed. The bone induction principle in irradiated, decalcified, bone matrix continues to show promise in accelerating the healing of fractures [26]. Bioengineering plays a role in all the problem areas of surgical research. New and improved devices are needed to document the problems, to evaluate experimental solutions to the problems, and to solve the problems. A solid state cardiac monitor has been developed which is capable of discrimination between cardiac standstill, fibrillation, and electrode malplacement. An alarm is sounded when these conditions arise or when the rate exceeds or The
American
Journal
of Surgery
U.S. Army Surgical Research Program
falls below preset limits. We have developed an artificial hand with proportionate grasp which has recently been augmented by the use of a voice-controlled switch to provide the severely disabled amputee with a source of wrist and elbow control. A compact spring is being used to maintain skin traction during the early postamputation period, thus avoiding problems of postoperative skin shrinkage. The need for respiratory support for severely wounded patients has re-emphasized the requirements for improved respirators and for blood oxygenators. A volume-cycled ventilator, also capable of pressure cycling, has been constructed utilizing fluid amplification principles; this unit is now being evaluated by our research team in Vietnam. Oxygenators currently in use are inadequate for prolonged support because of the trauma inflicted on the blood. We are supporting work to evaluate and define “ideal” oxygen transfer surfaces and oxygenator configurations, which minimize the boundary layer problems and increase oxygen transfer efficiency. One project utilizing a rapidly oscillating tubular membrane has recently achieved the theoretical maximal oxygen transfer of 203 cc. 0,/min./m2. with a 5 mil thick silicone membrane [.27]. Surface pH changes have been shown to reflect changes in the blood supply and metabolism of renal tissue [.%I. Berman, Lemieux, and Aaby [29] have apnlied tissue pH measurements to the study of skeletal muscle injured by crush, burn, and high velocity missiles. There is an excellent correlation of the acutely measured pH changes with changes in tissue perfusion. The extension of these studies may have surgical application in the assessment of limb and soft tissue viability after ischemia or trauma. Once problems are identified as having military significance, they become foundations for our various research programs. Studies in depth are necessary to achieve a reasoned and orderly improvement in clinical medicine. Therefore, to make contributions of significance to military medicine, our research program must continue to support basic work in trauma and its associated problems. Our opportunity to study clinical trauma in a healthy population is unparalleled and must not be wasted. Our observations, studies, and results are applicable in the treatment of injuries among civilians. Our objectives and those of civilian surgeons may best be achieved by the Vol.
118, September
1969
continued inclusion of academically oriented, inquisitive surgeons on our research teams and by their participation in our extramural research programs. References 1.
2.
3.
4.
5.
6.
7.
8.
9.
10. 11.
12.
13.
14.
BONICA, J., KENNEDY, W., AKAMATSU, T., and GERBERSHAGEN, H. Comparative evaluation of regional and general anesthesia. Annual Progress Report, 1968. WILSON, A.. SANCES. A.. and LARSON. S. Effects of’ electrical anesthesia on acquisition and retention of behavior patterns in primates. In : Electrotherapeutic Sleep and Electroanesthesia, p. 225. Amsterdam, 1967. Excerpta Medica Foundation. STRUMIA, M., EUSEBI, A., and STRUMIA, P. The preservation of blood for transfusion. VI. J. Lab. & Clin. Med.. 71: 138. 1968. BARTLETT,G. Review of the metabolism of adenine. Metabolism of adenine in the rabbit. Report to the Blood Resources Program, 1968. HARADIN, A. R., WEED, R., and REED, C. F. Changes in physical properties of stored erythrocytes: relation to in vivo survival. Transfusion, in press. BUNN, H., MAY, M., KOCHOLATY,W., and SHIELDS,C. Hemoglobin function in stored blood. J. Clin. Invest., 48: 311, 1969. CHANUTIN. A. and CURNISH.R. Effect of organic and inorganic phosphates on the oxygen equilibrium of human erythrocytes. Arch. Biochem., 121: 96,1967. CHANUTIN, A. Effect of storage of blood in ACD-adenine-inorganic phosphate plus nucleosides on metabolic intermediates of human red cells. Transfusion, 7 : 409,1967. MATSUDA.T.. TAUBE.R.. BAKER.R.. DERN. R.. ELWY~, D., and SHOEMAKER:W. Red’cell survival of 42 days ACD-adenine preserved blood after transfusion into trauma patients. J. Lab. & Clin. Med.. in Dress. SHIELDS, C. Comparison studies of whole blood stored in ACD and CPD with adenine. Transfusion, 8 : 1,1968. LITWIN, M., STOLIAR,J., CHAPMAN, K., and RUBENSTEIN, P. Blood physical-chemical changes following infusion of dextran 70, hydroxyethylated starch, or saline. To be published. RABINER, S., HELBERT, J., LOPAS, H., and FRIEDMAN,L. Evaluation of a stroma-free hemoglobin solution for use as a plasma expander. J. Exper. Med., 126: 1127,1967. COOPERBAND, S., DAVIS, R., SCHMID, K., and MANNICK, J. Mechanism of action of an immunoreaulators human alnha globulin. J. Clin. Invest., in-press. _ KOLKER.P.. HAMPERS.C.. and HAGER.E. Skin graft’ survival by treatment with homologous anti-typhoid sera. S. Forum, in
press.
15.
FINE, J., PALMERIO,C., and RUTENBERG,S. 361
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16.
17.
18.
19.
20.
21.
22. 23.
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New developments in the treatment of refractory shock. Arch. Surg., 96: 163,1968. MOSELEY,R., DOTY, D., and PRUITT,B. Physiologic changes following chest injury in combat casualties. Surg. Gynec. & Obst., in press. DOTY, D., MOSELEY,R., and PRUITT,B. Hemodynamic consequences of respiratory insufficiency following trauma. J. Thoracic & Cardiovasc. Surg., in press. DOTY, D., HUFNAGEL,H., and MOSELEY,R. The distribution of body fluids following hemorrhage and resuscitation in combat casualties. To be published. BERMAN, I., GUTIERREZ,V., BURRAN, E., and BOATRIGHT,R. Intravascular micro aggregation in combat casualties. S. Forum, in press. BERMAN,I. and GUTIERREZ, V. The role of intravascular micro aggregation in post traumatic pulmonary insufficiency. To be published. SWANK, R. L., ROTH, J., and JANSEN, J. Screen filtration pressure method and adhesiveness and aggregations of blood cells. J. Appl. Physiol., 19: 340, 1964. MOSELEY,R. and DOTY, D. Changes in the filtration characteristics of stored blood. To be submitted for publication. HENRY, J., MATSUMOTO,T., and HAYES, G.
24.
25.
26.
27.
28.
29.
In flight blood gas studies on casualties evacuated from Viet Nam to Japan. Submitted for publication. GUTIERREZ,V., BERMAN, I., and AABY, G. Relationship of crystalloid administration during resuscitation to serum solids and development of arterial hypoxemia. Submitted for publication. MATSUMOTO, T., MOSELEY, R., WITE, S., HENRY, J., and NEMHAUSER,G. Surgical research in the communications zone. Enzyme fluctuations in wounded combat soldiers during the convalescent period. Arch. Surg, in press. URIST, M., DOWELL,T., HAY, P., and STRATES, B. Inductive substrates for bone formation. In: Clinical Orthopedics No. 59, p. 59. Philadelphia, 1968. J. B. Lippincott Co. DRINKER, P., BARTLETT,R., BIALER, R., and NOYES, B. Augmentation of membrane gas transfer by induced secondary flows. Surgery, in press. DMOCHOWSKI,J., COUCH, N. KEMPF, R., and APPLETON,D. Electrometric surface pH of the ischemic kidney and the effect of hypothermia. J. S. Res., 6: 45, 1966. BERMAN, I., LEMIEUX,M., and AABY, G. Responses of skeletal muscle pH to injury: a new technique for determination of tissue viability. Surgery, in press.
The American Journal of Surgery
LTC. LOUIS F. PLZAK, Jr., Washington, COL. LAWRENCE R. ROSE, Washington, MAJ. GEN. JOE M. BLUMBERG,
Washington,
LTG. LEONARD D. HEATON, Washington,
The primary objective of the Army Medical Research and Development Command’s Surgical Research Program is to improve the care of interest is wounded soldiers ; our primary trauma, its effects, and optimal treatment. This broad objective necessitates our participation in many areas of related research. Our basic programs are intended to provide fundamental knowledge and to devise experimental approaches necessary to initiate or expand applied research on problems of obvious military significance. Improvements in the care of combat casualties require a basic understanding of the effect of trauma on the patient and of the mechanism by which various modes of treatment affect the recovery response. Our program is about evenly distributed between extramural contractors, who primarily contribute basic research to our program, and intramural work at relatively less basic and clinical levels. Our program in laser research is an example of our effort to document and evaluate the effects of various types of trauma. Laser investigations conducted by a joint U. S. Army Medical Research and Development Command -U. S. Army Material Command Laser Safety Team at Frankford Arsenal are concerned with the formulation of safety criteria for the employment of military laser devices and laser systems. The remainder of the program is exploring problems of repeated exposure to lasers, wave length-specific effects, long-term effects of laser injury, and changes in cell function at subthreshold energy levels. From the Shock and search Division, U. velopment Command,
356
Trauma Research Branch, Surgical S. Army Medical Research and Washington, D. C.
ReDe-
D. C.
D. C.
D. C.
Our program in anesthesia is an example of a continuing effort to evaluate the adverse effects as well as the beneficial effects of various treatment regimens on the casualty. This information contributes to our development of therapy with minimal “cost” to the patient. We are continuing to support studies on the effects of anesthetic and vasoactive agents on renal, hepatic, and myocardial flow and function in normal and hypovolemic subjects. In hypovolemic states the depressant cardiovascular changes are accentuated by both spinal and epidural anesthesia. Therefore, although epinephrine usually is added to a local anesthetic solution to decrease the rate of absorption of the agent and to offset cardiovascular depression in normal subjects, this supplementation is mandatory when spinal or epidural anesthetics are used during hypovolemia [I]. An ideal anesthetic for field use would not only need to be completely safe, but also require only simple and easily operated equipment, provide rapid onset and recovery, and leave no residual disability. One approach to these requirements is an electrical anesthesia device which is now being evaluated- in primates [Z]. This equipment can achieve a surgical level of anesthesia within three minutes of onset, there is no interference with the cardiorespiratory paramand coordinated motor function reeters, turns within two minutes of its termination. Prior to evaluation of this device in man, its effects on conditioned behavioral responses (executive monkey) and brain histology are being studied after single and repeated exposures lasting from thirty minutes to ten hours. The blood preservation aspect of our proThe
American
Journal
of Surgery
U.S. Army Surgical
gram is concerned with defining the optimal conditions for storage in which the deterioration of blood is minimized. We are concerned not only with the survival of the formed elements but also with the maintenance of their function. The metabolic reactions responsible for maintaining viability are being defined. Adequate ATP levels in the erythrocyte are essential to the maintenance of the integrity of the cell membrane. The addition of adenine and/or inosine to the storage medium will regenerate the intracellular ATP levels ; we are studying the optimal concentration and timing of their addition [3] as well as their metabolism and toxicity 141. Studies of the cell membrane have revealed a decrease in total lipid with senescence; once these alterations have occurred, they are not reversed even when adequate ATP levels are restored by the addition of adenine [5]. Membrane defects increase cellular permeability to calcium which is associated with irreversible erythrocyte contraction. The oxygen dissociation curve of blood stored beyond ten to fourteen days shifts to the left IS]. These erythrocytes do not readily release oxygen which may result in deficient tissue oxygenation. It has been noted that when intracellular phosphate as 2,3-diphosphoglycerate (2,3-DPG) is bound to hemoglobin, this binding results in decreasing the affinity of oxygen to the hemoglobin molecule (71. The level of intracellular 2,3-DPG is regulated by cellular metabolism. A deficiency of 2,3-DPG has been noted in stored blood which can be replenished by the addition of phosphate [8]. Further work is being carried out to optimize the oxygen dissociation curve of transfused blood. Fortification of standard ACD preservation solution with adenine alone will permit the extension of the shelf life of blood from the current three week limit to five or six weeks with acceptable survival rates; it provides metabolically and functionally superior erythrocytes at all periods of storage 19,101. A team recently established at the 93rd Evacuation Hospital, Vietnam, has been conducting a clinical evaluation of ACD-adenine blood in a field environment. Although in the past we have oriented our work toward the erythrocyte, we are now broadening our approach to consider the prevention of storage damage to other blood constituents, such as platelets and coagulation factors, which are Vol. 118, September 1969
Research
Program
also essential in the resuscitation of patients in hemorrhagic shock. Plasma substitutes are used for emergency treatment of hemorrhagic shock, but concern due to allergic reactions, viscosity changes, and coagulation defects has restricted their use. Hydroxyethylstarch (HES) is a plasma expander possessing minimal antigenicity, although, like dextran, it interferes with the clotting mechanism. Recent studies demonstrate that its lower molecular weight fractions do not increase blood viscosity and do not interfere with the microcirculation and tissue oxygen consumption [ll]. Current data suggest that clotting problems may be related to the molecular weight of the fraction, and we are continuing our efforts to improve the separation of HES into sharp molecular weight fractions for further evaluation. A hemoglobin solution free of stromal material has been shown to function as a plasma expander and oxygen carrier [121. Initial studies confirm the absence of renal toxicity and the lack of interference with coagulation factors. We are currently studying the efficacy of the hemoglobin solution in hemorrhagic shock, its effect on primates with pre-existing renal disease, its influence on viscosity, its antigenicity, and its ability to oxygenate tissue. Various polypeptides, comprised of an ordered sequence of alpha-amino acids, are being synthesized. They are capable of expanding the circulating blood volume and are essentially nonantigenic. We anticipate that the knowledge of the structure of these synthetic materials will enable us to understand the relationship between specific chemical configurations and effects on clotting, viscosity, and antigenicity. Basic work on the immunogenicity of polypeptides complements our transplant program which is primarily directed toward understanding the basic immunology of transplant antigens. An immunoregulatory alpha-globulin isolated from fraction IV of normal plasma is being characterized and studied as to the optimal time, dose, and route of administration for maximal immunosuppressive effects [13]. It ap,pears to inhibit macrophage migration by its reaction with lymphocytes producing macrophage immobilization factor. The feasibility of using the inhibition of macrophage migration as an in vitro indication of the immunologic status of a graft recipient is in progress. Anti357
Plzak et al.
sera to viral endotoxins may exert an immunosuppressive effect [14] ; attempts are being made to define this mechanism of suppression and to establish a system for predicting the antigenic effect of endotoxin. Improvements in organ preservation technics are also basic to any transplant program. We have recently initiated the support of two studies on the preservation of organs, one relating to the effects of temperature changes on cellular metabolism and preservation and the other investigating the feasibility of using extremely high pressures (10,000 to 15,000 p.s.i.) for freezing point depression in order to provide uniform freezing and thawing of tissue undergoing storage. The work on basic immunology and tissue preservation is also related to our interest in burns. The value of skin grafting in early burn therapy has been clearly shown ; we are now expanding our attempts to provide materials, both natural and synthetic, which might be suitable substitutes for homografts. The use of Sulfamylon@ ointment, a topical antibiotic developed by the U. S. Army Institute of Surgical Research (ISR) at Brooke Army Medical Center, contributes to our decreased burn morbidity and mortality. We are continuing our search for improved analogs of Sulfamylon with less toxicity and greater antibacterial potency as well as for other antibacterial agents. An analog of Sulfamylon has been synthesized at ISR which is free of carbonic anhydrase inhibition and shows satisfactory antibacterial activity. Carbenicillin@ (disodium-acarboxyl penicillin) has produced encouraging results when used either topically or systemically for Pseudomonas burn wound sepsis in animals. It has been demonstrated to be effective in the control of established burn infections. Important new areas of concentration have emerged with the subsidence of burn wound sepsis as the primary cause for mortality from burns. These include melioidosis, septic thrombophlebitis, and gastrointestinal hemorrhage. Metabolic requirements and respiratory problems in burns continue to represent an important area of investigation. Our shock and trauma program supports studies evaluating the effect of hypovolemic and endotoxic shock on cellular and tissue changes. These include effects on cardiopulmonary function, blood viscosity and the microcirculation, tissue oxygen consumption and 358
metabolism, and tissue structure and function. Studies in dogs and primates are correlating pulmonary ultrastructural changes induced by shock with alterations in circulation, function, metabolism, and surfactant. Work continues to characterize the serum lipid and protein alterations seen in shock and to relate these changes to pathologic changes seen in the lung. Laboratories studying the effects of various types of therapy, including resuscitative fluids, splenic extracts, ganglionic blocking agents, steroids, and immunization, are being supported. Denervation of the spleen has been found to protect dogs from lethal endotoxic shock [IS]. Carboxylic esterase isolated from the spleen appears to be responsible for this protection ; its mechanism of action is being studied. Protection from endotoxic shock also has been achieved by the use of an antiserum obtained by the isolation of core antigens from gram-negative bacilli. Another aspect of this work is the development of a method for the early identification of endotoxic shock. The Walter Reed Army Institute of Research, a laboratory in the U. S. Army Medical Research and Development Command, has a surgical research team at the 24th Evacuation Hospital in Vietnam and also had an exploratory surgical research team at the 249th General Hospital in Japan. Much of the emphasis of our program is based on studies made by these teams. The ability of our teams to bring sophisticated laboratory technics to the field hospital has provided us with a unique opportunity to study selectively the effects of massive trauma and current therapeutic regimens in a relatively homogeneous population. The infrequency of pre-existing medical p’roblems in our casualties simplifies the analysis of our data. The most common cause of respiratory insufficiency in Vietnam is penetrating chest injury. The physiologic aspects of the changes resulting from chest injuries was studied by Moseley, Doty, and Pruitt [16,1?‘]. The average admission pOg for thirty-six patients studied was 6’7 mm. Hg, the pCOz 38 mm. Hg, and the pH 7.38. Pulmonary shunting was evaluated during various treatment regimens in eight of these patients. An initial shunt of 44 per cent was reduced to 27 per cent by breathing 100 per cent oxygen and to 14 per cent by the use of a volume cycled respirator. Decreased pulmonary shunting was associated The American Journal of Surgery
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with a decreased cardiac index. Although the oxygen consumption remained essentially the same in these patients, the lactate was decreased and clinical improvement was noted. Therefore, this assistance probably enabled the oxygen-starved peripheral tissues to obtain more oxygen. Twenty-seven critically ill patients with hypoxemia (pOa average, 47 mm. Hg; range, 19 to ‘71 mm. Hg) were selected for serial cardiopulmonary function studies. An increased cardiac output was observed to follow severe trauma associated with respiratory insufficiency unless blood volumes were depleted by more than 20 per cent. The hyperdynamic circulatory state is thought to be due to the functional shunting of blood in the pulmonary and peripheral circulations ; this is well tolerated for prolonged periods in previously healthy persons if hypoxemia can be controlled. Doty, Hufnagel, and Moseley [18] studied the distribution of body fluids as a function of resuscitative therapy. Eight of thirteen patients studied received large transfusions (average 6,350 cc. blood and 5,390 cc. Ringer’s lactate solution). Early in the postresuscitation period (one hour) the total body water was decreased by 2 L. (-10 per cent) and the erythrocyte volume by 1 L. (-33 per cent). At seventy-two hours there was a marked increase in extracellular water and plasma volume with a normal total body water. The red cell mass remained depleted at this interval. The extent of under transfusion is usually proportional to the amount of blood transfused. The high level of extracellular water may be due in part to sequestration and in part to the generous use of Ringer’s lactate solution during the resuscitative period. Intravascular microaggregation has been studied by Berman et al. [19,20] in Vietnam using a modification of Swanks screen filtration technic [Zl]. Blood is passed through a tube containing a sereen with a pore size of 20 p at a fixed rate. The pressure generated proximal to the screen is measured. A series of eighty-nine casualties with moderate to severe injuries of the extremities, abdomen, and/or thorax were included in the study. Arterial and venous screen filtration pressures (S.F.P.) were measured and correlated with blood gases, lactates, and base deficits. S.F.P. was elevated in 60 per cent of the ‘patients. Ninety-five per cent of the casualties with elevated arterial and venous S.F.P. had fractures or blast injuries; Vol. 118, September 1969
almost all of these were hypoxemic (~0, < 75 mm. Hg) on admission or shortly thereafter. No fat was noted on the screens. Although blood stored more than five to seven days will elicit an increased S.F.P. ; arterial samples obtained from patients immediately after receiving up to 60 units of this blood gave normal screen filtration pressures. It is postulated that these microemboli filtered out by the lung contribute to post-traumatic pulmonary insufficiency. At present Major Berman is correlating the changes in microaggregation measured by S.F.P. with blood viscosity. The in vitro addition of 5 mg. per cent of ADP (comparable to plasma concentration during storage) to a platelet concentrate will cause an increased S.F.P. (39 to 300 mm. Hg). The association of arterial hypoxemia with altered blood viscosity and the presence of certain vasoactive substances (ADP, serotonin) is also being studied in the postoperative period. Two patients dying of respiratory insufficiency shortly after sustaining severe wounds and receiving massive transfusions had clots scattered throughout the small pulmonary arterioles at postmortem examination. This prompted Moseley and Doty [ZR] to study the blood infused into 120 battle casualties in Vietnam for the presence of clots. Two standard blood filters, designed to retain particles greater than 170 p, were placed in series in the infusion line. The clotlike material obtained on the first and second filter was weighed and correlated with the age of the blood and the number of units of blood previously passed through the first filter. The amount of clotlike material obtained in the first filter increased with the duration of storage; there was a marked increase in the amount of material passed through the first filter when more than 3 units were infused through the same filter. Henry, Matsumoto, and Hayes IZS] studied the effects of aeromedical evacuation on 102 patients transferred from Vietnam to Japan in an Air Force Cl41 aircraft. The duration of the flights averaged four and a quarter hours. Seventy-two patients were studied on four flights at a cruising altitude of 37,000 feet and a cabin altitude equivalent to 6,700 to 7,200 feet. Serum and urine osmolalities, hematocrit, and blood gases were obtained eight to nine hours prior to departure, thirty minutes after takeoff, thirty to sixty minutes prior to land359
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ing, and finally immediately after landing. The patients most severely affected by the altitude were those with fractured femurs, fractures of the lower extremities, and chest injuries. Forty-eight seriously injured casualties had an initial p0, of 76.5 mm. Hg which fell to 49.6 mm. Hg in flight and returned to 76.8 mm. Hg on landing in Japan. Coinciding with this hypoxemia is a lowering of the pC0, and a rising pH. Except for the chest injury casualties, the patients in each group demonstrated some ability to compensate for the inflight hypoxemia by increasing their respiratory and pulse rates. The flights at cruising altitudes of 25,000 to 27,000 feet (cabin altitude 3,000 to 3,800) were better tolerated by all groups. The serum osmolality verified the presence of an adequate state of hydration in the patients. There was a significant correlation between low hematocrit, low red blood cell mass, low serum osmolality, and the hypoxemia observed in patients from all groups. This is consistent with the hypothesis advanced by Gutierrez, Berman, and Aaby [24] that low intravascular osmolality may contribute to increased pulmonary exudation and respiratory insufficiency. The effect of altitude on pre-existing pulmonary shunting needs to be defined. It is anticipated that these studies will contribute to the establishment of better criteria for the safe evacuation of wounded troops. A survey of the bacteriologic aspects of wound infections revealed a preponderance of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Most positive blood cultures are due to gram-negative organisms, primarily Ps. aeruginosa and KlebsieIla pneumoniae. This information and sensitivity data are being used to assist in the selection of a suitable topical antibiotic for field use. Local antibiotic therapy for wounds is being developed, not as a substitute for debridement, but as a means of retarding bacterial growth and thereby prolonging the period during which debridement can safely be delayed. Most wounds are closed four days or more after initial debridement. Clinical judgment as to the proper time for delayed closure may be in error due to unrecognized residual sepsis. Premature closure not only is dismaying to the surgeon, but also causes considerable distress to the patient. Matsumoto et al. [25] have studied the problem of the optimal time for de-
layed closure of soft tissue injuries by examining the relationship of lactic dehydrogenase, serum glutamic exalacetic transaminase, and creatinine phosphokinase (CPK) titers to residual infection. Of the enzymes studied, there appeared to be a correlation of infection only with the CPK titer. CPK is released from muscle destroyed by infection. Since Ps. aeruginosa readily causes local infarction and thrombosis with resultant muscle damage, an elevated CPK titer is a particularly sensitive indicator of the presence of this organism. Four wounds that clinically appeared ready for closure were subsequently noted to have had an elevated CPK at the time of closure; these did not heal satisfactorily. Healing was normal in thirty-three patients in whom the CPK levels were within the normal range at the time of secondary closure. These recent studies by our research teams in the field are examples of the type of data which contributes to the orientation of our more basic programs. These studies are also based, in part, on the work emanating from these more basic investigations. The biochemical phenomena of wound healing are being studied in animals and in man utilizing subcutaneously implanted wire mesh cylinders. Neurosurgical laboratories are evaluating the effects of concussion on spinal cord function and circulation and the comparative value of treatment by decompression, hypothermia, and steroids. We are continuing to support work designed to improve the results of peripheral nerve repairs. The beneficial effects of cooling and then retransecting cut nerves prior to anastomosis and the use of silicone sleeves around the anastomosis have been clearly demonstrated. Improved methods of preparing, preserving, and employing nerve grafts are being developed. The bone induction principle in irradiated, decalcified, bone matrix continues to show promise in accelerating the healing of fractures [26]. Bioengineering plays a role in all the problem areas of surgical research. New and improved devices are needed to document the problems, to evaluate experimental solutions to the problems, and to solve the problems. A solid state cardiac monitor has been developed which is capable of discrimination between cardiac standstill, fibrillation, and electrode malplacement. An alarm is sounded when these conditions arise or when the rate exceeds or The
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falls below preset limits. We have developed an artificial hand with proportionate grasp which has recently been augmented by the use of a voice-controlled switch to provide the severely disabled amputee with a source of wrist and elbow control. A compact spring is being used to maintain skin traction during the early postamputation period, thus avoiding problems of postoperative skin shrinkage. The need for respiratory support for severely wounded patients has re-emphasized the requirements for improved respirators and for blood oxygenators. A volume-cycled ventilator, also capable of pressure cycling, has been constructed utilizing fluid amplification principles; this unit is now being evaluated by our research team in Vietnam. Oxygenators currently in use are inadequate for prolonged support because of the trauma inflicted on the blood. We are supporting work to evaluate and define “ideal” oxygen transfer surfaces and oxygenator configurations, which minimize the boundary layer problems and increase oxygen transfer efficiency. One project utilizing a rapidly oscillating tubular membrane has recently achieved the theoretical maximal oxygen transfer of 203 cc. 0,/min./m2. with a 5 mil thick silicone membrane [.27]. Surface pH changes have been shown to reflect changes in the blood supply and metabolism of renal tissue [.%I. Berman, Lemieux, and Aaby [29] have apnlied tissue pH measurements to the study of skeletal muscle injured by crush, burn, and high velocity missiles. There is an excellent correlation of the acutely measured pH changes with changes in tissue perfusion. The extension of these studies may have surgical application in the assessment of limb and soft tissue viability after ischemia or trauma. Once problems are identified as having military significance, they become foundations for our various research programs. Studies in depth are necessary to achieve a reasoned and orderly improvement in clinical medicine. Therefore, to make contributions of significance to military medicine, our research program must continue to support basic work in trauma and its associated problems. Our opportunity to study clinical trauma in a healthy population is unparalleled and must not be wasted. Our observations, studies, and results are applicable in the treatment of injuries among civilians. Our objectives and those of civilian surgeons may best be achieved by the Vol.
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continued inclusion of academically oriented, inquisitive surgeons on our research teams and by their participation in our extramural research programs. References 1.
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BONICA, J., KENNEDY, W., AKAMATSU, T., and GERBERSHAGEN, H. Comparative evaluation of regional and general anesthesia. Annual Progress Report, 1968. WILSON, A.. SANCES. A.. and LARSON. S. Effects of’ electrical anesthesia on acquisition and retention of behavior patterns in primates. In : Electrotherapeutic Sleep and Electroanesthesia, p. 225. Amsterdam, 1967. Excerpta Medica Foundation. STRUMIA, M., EUSEBI, A., and STRUMIA, P. The preservation of blood for transfusion. VI. J. Lab. & Clin. Med.. 71: 138. 1968. BARTLETT,G. Review of the metabolism of adenine. Metabolism of adenine in the rabbit. Report to the Blood Resources Program, 1968. HARADIN, A. R., WEED, R., and REED, C. F. Changes in physical properties of stored erythrocytes: relation to in vivo survival. Transfusion, in press. BUNN, H., MAY, M., KOCHOLATY,W., and SHIELDS,C. Hemoglobin function in stored blood. J. Clin. Invest., 48: 311, 1969. CHANUTIN. A. and CURNISH.R. Effect of organic and inorganic phosphates on the oxygen equilibrium of human erythrocytes. Arch. Biochem., 121: 96,1967. CHANUTIN, A. Effect of storage of blood in ACD-adenine-inorganic phosphate plus nucleosides on metabolic intermediates of human red cells. Transfusion, 7 : 409,1967. MATSUDA.T.. TAUBE.R.. BAKER.R.. DERN. R.. ELWY~, D., and SHOEMAKER:W. Red’cell survival of 42 days ACD-adenine preserved blood after transfusion into trauma patients. J. Lab. & Clin. Med.. in Dress. SHIELDS, C. Comparison studies of whole blood stored in ACD and CPD with adenine. Transfusion, 8 : 1,1968. LITWIN, M., STOLIAR,J., CHAPMAN, K., and RUBENSTEIN, P. Blood physical-chemical changes following infusion of dextran 70, hydroxyethylated starch, or saline. To be published. RABINER, S., HELBERT, J., LOPAS, H., and FRIEDMAN,L. Evaluation of a stroma-free hemoglobin solution for use as a plasma expander. J. Exper. Med., 126: 1127,1967. COOPERBAND, S., DAVIS, R., SCHMID, K., and MANNICK, J. Mechanism of action of an immunoreaulators human alnha globulin. J. Clin. Invest., in-press. _ KOLKER.P.. HAMPERS.C.. and HAGER.E. Skin graft’ survival by treatment with homologous anti-typhoid sera. S. Forum, in
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New developments in the treatment of refractory shock. Arch. Surg., 96: 163,1968. MOSELEY,R., DOTY, D., and PRUITT,B. Physiologic changes following chest injury in combat casualties. Surg. Gynec. & Obst., in press. DOTY, D., MOSELEY,R., and PRUITT,B. Hemodynamic consequences of respiratory insufficiency following trauma. J. Thoracic & Cardiovasc. Surg., in press. DOTY, D., HUFNAGEL,H., and MOSELEY,R. The distribution of body fluids following hemorrhage and resuscitation in combat casualties. To be published. BERMAN, I., GUTIERREZ,V., BURRAN, E., and BOATRIGHT,R. Intravascular micro aggregation in combat casualties. S. Forum, in press. BERMAN,I. and GUTIERREZ, V. The role of intravascular micro aggregation in post traumatic pulmonary insufficiency. To be published. SWANK, R. L., ROTH, J., and JANSEN, J. Screen filtration pressure method and adhesiveness and aggregations of blood cells. J. Appl. Physiol., 19: 340, 1964. MOSELEY,R. and DOTY, D. Changes in the filtration characteristics of stored blood. To be submitted for publication. HENRY, J., MATSUMOTO,T., and HAYES, G.
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In flight blood gas studies on casualties evacuated from Viet Nam to Japan. Submitted for publication. GUTIERREZ,V., BERMAN, I., and AABY, G. Relationship of crystalloid administration during resuscitation to serum solids and development of arterial hypoxemia. Submitted for publication. MATSUMOTO, T., MOSELEY, R., WITE, S., HENRY, J., and NEMHAUSER,G. Surgical research in the communications zone. Enzyme fluctuations in wounded combat soldiers during the convalescent period. Arch. Surg, in press. URIST, M., DOWELL,T., HAY, P., and STRATES, B. Inductive substrates for bone formation. In: Clinical Orthopedics No. 59, p. 59. Philadelphia, 1968. J. B. Lippincott Co. DRINKER, P., BARTLETT,R., BIALER, R., and NOYES, B. Augmentation of membrane gas transfer by induced secondary flows. Surgery, in press. DMOCHOWSKI,J., COUCH, N. KEMPF, R., and APPLETON,D. Electrometric surface pH of the ischemic kidney and the effect of hypothermia. J. S. Res., 6: 45, 1966. BERMAN, I., LEMIEUX,M., and AABY, G. Responses of skeletal muscle pH to injury: a new technique for determination of tissue viability. Surgery, in press.
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