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External counterpressure and the MAST suit: Current and future roles
CONCEPTS, COMPONENTS, AND CONFIGURATIONS
External Counterpressure and the MAST Suit: Current and Future Roles Jerome R. Hoffman, MD Los Angeles, California
External counterpressure devices, such as the MAST suit, may be lifesaving not only in acute hypovolemia secondary to abdominal, pelvic and lower extremity trauma, but in a number of other shock states as well. Expanded use of the MAST suit may well include not qnly supra-diaphragmatic injuries, but diverse entities such as pericardial tamponade, tension pneumothorax, and leaking aortic aneurysm, and as an adjunct to cardiopulmonary resuscitation. The limited adverse effects of the MAST suit, in conjunction with its rapidly favorable and rapidly reversible hemodynamic effect, make it an important tool not only in prehospital care and in the emergency department, but in a wide variety of hospital circumstances. For this reason emergency physicians must not only be aware of uses of the MAST suit themselves, but should be prepared to disseminate this information to the general medical c o m m u n i t y . . H o f f m a n JR: External counterpressure and the MAST suit: current and future roles. Ann Emerg Med 9:419-421, August 1980.
external counterpressure devices, military antishock trousers; MAST suit, treatment of shock; military antishock trousers; shock, therapy, military antishock trousers INTRODUCTION A variety of devices have been used to produce external counterpressure on the lower extremities and abdomen. Though Crile first described the successful use of this technique in the t r e a t m e n t of hypovolemic shock, 1 it is only recently t h a t such devices have attracted a t t e n t i o n in the broad medical community. While those of us i n emergency medicine and prehospital care have been gaini n g increased experience with external counterpressure over the past several years, a lead article 2 and editorial 3 in the Journal of the American Medical Association as recently as F e b r u a r y 1979 make it clear t h a t most of the medical c o m m u n i t y r e m a i n u n f a m i l i a r with, and even suspicious of, this technique. There are a n u m b e r of external counterpressure devices, of which the most f r e q u e n t l y used is the Military Anti-Shock Trousers, or MAST suit. (For simplicity's sake, we will refer to the group of these devices as the MAST suit.) The MAST suit is an inflatable trouser device which can produce t i t r a t a b l e increased external pressure on the lower extremities and abdomen. Despite Crile's early work, the technique of external counterpressure was generally abandoned with the advent of blood transfusion; interest was revived, p a r t i c u l a r l y d u r i n g the V i e t n a m War, where field casualties with hemorrhagic shock secondary to lower extremity and abdominal injuries were repeatedly resuscitated using a MASTtype device as part of the regimen, n Since t h a t time, m a n y case reports have From the Department of Medicine, UCLA Hospital and Clinics, The Center for the Health Sciences, Los Angeles, California. Address for reprints: Jerome R. Hoffman, MD, Assistant Professor of Medicine, UCLA Hospit a l and Clinics, The Center for the Health Sciences, Los Angeles, California 90024.
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documented the successful use of the M A S T suit in a variety of situations in which lower extremity, abdominal, and pelvic bleeding has produced hypovolemic shock. 5-1~ The J A M A a r t i c l e 2 cites 174 case reports dealing with MAST suit usage, but correctly notes t h a t the t r u e c l i n i c a l s a m p l e of p a t i e n t s treated with the MAST suit is, i n fact, far larger. MAST suit use i n prehospital care has become almost routine in m a n y large centers over the past several years. 2 Despite the a b u n d a n c e of clinical case reports a n d t h e e v e n g r e a t e r anecdotal experience with the MAST device, only l i m i t e d s t u d i e s h a v e been done to elucidate the hemodyn a m i c effects of the MAST suit. ~2-14 These hemodynamic effects seem to be related primarily to two factors: t h e r e is a r e d i s t r i b u t i o n of venous blood flow from the lower extremities a n d a b d o m e n to o r g a n s above the diaphragm; and there is a direct effect on e x t r a l u m i n a l a r t e r i a l a n d venous pressure in the areas covered by the suit. Application of the trousers is accompanied by a rise in central venous pressure and a n increase in aortic and carotid flow and pressure, with a concomitant decrease in femoral flow and pressure. There is also an increase in systemic vascular resistance, arterial blood pressure (as measured in the upper extremities), and cardiac stroke volume. Cardiac output r e m a i n s unchanged, however, as increased stroke volume is accompanied by decreased heart rate. 12-~4 It has been assumed generally that the b r a d y c a r d i a noted with MAST suit use is a result of a depressor reflex s t i m u l a t i o n s e c o n d a r y to increased arterial pressure in the aorta a n d carotid sinus. This reflex response may be more limited in pat i e n t s with n o r m a l blood p r e s s u r e t h a n in hypovolemic patients with hypotension, 2 as we have also noted it in an ongoing study of patients in paroxysmal atrial tachycardia treated with the MAST suit (J. Hoffman, u n p u b l i s h e d data). Morbidity from the use of the MAST suit, apart from local trophic skin Changes, has been limited generally to mild degrees of lactic acidosis secondary to decreased lower ext r e m i t y blood flow f o l l o w i n g prol o n g e d usage. 2,15-1s N e v e r t h e l e s s , several i n v e s t i g a t o r s have applied external counterpressure over periods as long as 40 h r and more without notable systemic acidosis.2,19-2~ This is particularly true when MAST suit pressures of 20 m m Hg to 40 m m
40/420
Hg, rather t h a n the m a x i m a l inflation of 104 m m Hg, have been used. Decreased u r i n a r y output and glome r u l a r filtration rates associated with p r o l o n g e d u s e of M A S T d e v i c e s have never been associated with changes in renal t u b u l a r metabolic f u n c t i o n a n d are of q u e s t i o n a b l e if a n y s i g n i f i c a n c e . 2,1~,19,21-23 O t h e r s i g n i f i c a n t m o r b i d i t y m a y occur in p a t i e n t s with specialized problems. The MAST suit, by d i s t r i b u t i n g a larger volume of blood to structures above the diaphragm, increases the venous r e t u r n to the lungs and thus causes the p u l m o n a r y wedge pressure to rise. This certainly could be deleterious in p a t i e n t s with congestive heart failure and pulmonary edema. Slight decreases in respiratory excursion secondary to abdominal compression have not been shown to have significant clinical effects,l°,~7, 24 but may be i m p o r t a n t in patients with already diminished l u n g function. Concern also has been raised a b o u t increased b l e e d i n g in p a t i e n t s with chest and head injuries with use of the MAST suit. It seems clear t h a t the MAST suit is a valuable adjunct to acute resuscitation of patients with hypovolemic shock secondary to lower ext r e m i t y and abdominal bleeds. This has been well documented, and the JAMA article and accompanying editorial, which adds t h a t ~skeptics a r e e n c o u r a g e d to g i v e it a f a i r trial,"2, z i l l u s t r a t e t h a t such docum e n t a t i o n is now becoming available to more t h a n just those who practice e m e r g e n c y medicine.2,3 Other uses for the MAST device are more controversial. One area in which use of the MAST suit would seem to make sense, but about which there has been no clinical evidence, is t h a t of the relative hypovolemia of such conditions as pericardial tamponade and tension p n e u m o t h o r a x . While total blood volumes in these situations may well be normal, hypot e n s i o n occurs s e c o n d a r y to decreased venous r e t u r n and decreased filling of the h e a r t because of the underlying abnormality. Temporary p r e h o s p i t a l use of the MAST suit, p r i o r to a v a i l a b i l i t y of d e f i n i t i v e therapy, would appear to afford several benefits: it provides a rapid increase i n thoracic blood volume; it increases venous r e t u r n u n d e r pressure; and it is quickly reversible once the u n d e r l y i n g lesion is corrected. Similarly in patients with electromechanical dissociation, the MAST suit m a y h a v e some r e a l v a l u e . T h e m a j o r i t y of such p a t i e n t s are, of
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c o u r s e , n o t s a l v a g e a b l e , as elec-: tromechanical dissociation is gener-1 ally a reflection of a dying heart. It I m a y occasionally reflect massive acute hypovolemia, however, and in such circumstances dramatic volume r e d i s t r i b u t i o n with the MAST suit m i g h t be s u c c e s s f u l , w h i l e tradit i o n a l therapy, with drugs such as isoproterenol, e p i n e p h r i n e and calcium, rarely contributes to long-term survival. It s h o u l d be r e m e m b e r e d t h a t clinical documentation of such use has not yet appeared in the medical literature. There has been a modicum of interest in usage of the MAST suit in o t h e r forms of shock, p a r t i c u l a r l y cardiogenic shock. The sole published report on this subject 25 purports to d e m o n s t r a t e increased survival with prehospital use of the MAST suit in cardiogenic shock. However, careful perusal of that study reveals several major problems in the design, and it is far from clear whether any of the p a t i e n t s who b e n e f i t e d from this therapy did, in fact, suffer from cardiogenic shock. T h e o r e t i c a l l y it is h a r d to i m a g i n e the MAST suit being of use in pump failure, except in that s m a l l group of p a t i e n t s designated Class III by the Forrester 26,27 classification of acute myocardial infarct i o n , ie, those in shock f o l l o w i n g acute myocardial infarction because of relative hypovolemia and not intrinsic pump failure. Such p a t i e n t s do occasionally r e s p o n d to v o l u m e t h e r a p y , a n d in t h a t i n s t a n c e , the M A S T s u i t m a y well be of e q u a l value. In the large majority of pat i e n t s with cardiogenic shock, forward pump failure is associated with backward fluid overload and elevated wedge pressures; i n these p a t i e n t s the MAST suit, like volume therapy, is probably deleterious. Its f u r t h e r effect of i n c r e a s i n g t h e a f t e r l o a d a g a i n s t which the failing heart must p u m p would seem to compound the hazard. There also has been recent interest in the use of external counterpressure d u r i n g cardiopulmonary resuscitation (CPR), and several clinical trials now are being u n d e r t a k e n with this in mind. While simplified versions of this method were undert a k e n m a n y years ago, 2s,29 there are l i m i t e d good e x p e r i m e n t a l data on the subject. In a 1974 report, 15 dogs receiving abdominal compression d u r i n g CPR did significantly better t h a n controI clogs and methoxaminet r e a t e d dogs2 A J a p a n e s e study in 1976 demonstrated t h a t increases of coronary and carotid flow up to two-
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fold, as well as i n c r e a s e d s u r v i v a l , could be obtained with selective diastolic abdominal compression during CPR. 3° We now know t h a t circulation during CPR occurs because of increases in i n t r a t h o r a c i c p r e s s u r e during chest compression. 31-34 We might, therefore, predict a decrease in cardiac output (and thus perfusion) when the s t a n d a r d i n t r a t h o racic pressure change b r o u g h t about during CPR occurs in the face of significantly higher resistance produced by a MAST device, p a r t i c u l a r l y when that device is not capable of selective diastolic c o u n t e r p r e s s u r e . On t h e other hand, decreased d i a p h r a g m a t i c excursion s e c o n d a r y to a b d o m i n a l binding might increase the degree of intrathoracic p r e s s u r e r i s e d u r i n g compression, and thus i n c r e a s e total cardiac output wh i le selectively increasing flow to the carotids. F u r t h e r investigation of continuous or intermittent abdominal c o u n t e r p r e s s u r e during cardiac arrest is w a r r a n t e d . Use of the MAST suit in hypovolemic shock s e c o n d a r y to i n j u ries above the d i a p h r a g m r e m a i n s controversial. Op p o n e n ts of its use suggest that redistribution of blood to an area of h e m o r r h a g e will only increase total blood loss and, therefore, is c o n t r a i n d i c a t e d . H o w e v e r , there are two theoretical a d v a n t a g e s even in t h e s e c i r c u m s t a n c e s . T h e first is t h a t t h e a c u t e i n c r e a s e in blood flow to v i t a l o r g a n s (ie, th e heart and brain) m a y be life-saving as a method of buying time, despite eventual increased total blood loss. This, of course, presumes acute hypotension and the e a r ly a v a i l a b i l i t y of more d e f i n i t i v e m e a s u r e s . Second, decreased cerebral blood flow is associated w i t h i n c r e a s e d c e r e b r a l edema. In this case, a M A S T s u i t may, by r e d i s t r i b u t i n g flow, help to decrease cerebral edema. It should be noted that there h a v e been no clinical or e x p e r i m e n t a l trials to e v a l u a t e the effect of e x t e r n a l counterpressure in such an instance.
SUMMARY Emergency physicians h a v e had to deal with the ignorance of and resistance to use of the MAST suit by other physicians. F o r t u n a t e l y , t h e broad medical c o m m u n i t y is becoming a w a r e of t h e M A S T s u i t a n d , perhaps grudgingly, i n t e r e s t e d in its use. Those of us in e m e r g e n c y medicine who have relied on the MAST devices in t h e p a s t m u s t b e c o m e more completely a w a r e of t h e i r uses, potential, and possible contraindications.
9:8 (August) 1980
REFERENCES 1. Crile GW: Blood Pressure in Surgery: Experimental and Clinical Research. Philadelphia, JB Lippincott Co, 1903, p 288-291. 2. Pelligra R, Sandberg EC: Control of intractable abdominal bleeding by external counterpressure. JAMA 241:708-713, 1979.
18. Ransom KJ: Metabolic acidosis with pneumatic trousers in hypovolemic dogs. JACEP 8:184-187, 1979. 19. McLaughlin AP, McCullough DL, Kerr WS Jr, et al: The use of the external counterpressure (g-suit) in management of traumatic retroperitoneal hemorrhage. J Urol 107:940-944, 1972.
3. Carden TS: A fair trial for CPC (editorial). JAMA 241:729, 1979.
20. Batalden DJ, Wickstron PH, Ruiz E, et al: Value of the g-suit in patients with severe pelvic fracture. Arch Surg 109: 326-328, 1974.
4. Cutler BS, Daggett W: Application of the g-suit to the control of hemorrhage in massive trauma. Ann Surg 173:511-514, 1971.
21. Burdick JF, Warshaw AL, AbboLt WM: External counterpressure to control postoperative intra-abdominal hemorrhage. Am J Surg 129:369-373, 1975.
5. Gardner WJ, Taylor HP, Dohn DF: Acute blood loss requiring 58 transfusions: The use of anti-gravity suit as an aid to post-partum intra-abdominal hemorrhage. JAMA 167:985-986, 1958.
22. Roth JS, Rutherford RB: Regional blood flow effect of g-suit application during hemorrhagic shock. Surg Gynecol Obstet 133:637-643, 1971.
6. Gardner WJ, Storer J: The use of the g-suit in control of intra-abdominal bleeding. Surg Gynecol Obstet 123:792-798, 1966. 7. Ludewig RM, Wangensteen SL: Aortic bleeding and the effect of external counterpressure. Surg Gynecol Obstet 128:252258, 1969. \
8. Wangensteen SL, Ludewig RM, Cox JM, et al: The effect of external counterpressure on arterial bleeding. Surgery 64:922-927, 1968. 9. Redding JS: Abdominal compression in cardiopulmonary resuscitation. Anesth Analg 50:668-675, 1971. 10. Espinosa MS, Updegrove JS: Clinical experience with the g-suit. Arch Surg 101:36, 1970. 11. McCullough DL, McLaughlin AP, Warshawsky AB: The gravity suit. A useful device in complicated urologic hemorrhage. Urology 6:468-470, 1975. 12. Wangensteen SL, Ludewig RM, Eddy DW: Effect of external counterpressure on the intact circulation. Surg Gynecol Obstet 127:253-258, 1968. 13. Gray S, Shaver JA, Kroetz FW, et al: Acute and prolonged effects of g-suit inflation on cardiovascular dynamics. Circulation (supp II) 35, 36:125, 1967. 14. Gray S, Shaver JA, Kroetz FW, et al: Acute and prolonged effects of g-suit inflation on cardiovascular dynamics. Aerospace Med 40:40-43, 1969. 15. Wangensteen SL, deHoll JD, Ludewig RM, et al: The detrimental effect of the g-suit in hemorrhagic shock. An n Surg 170:187-192, 1969. 16. Shenasky JH, Gillenwater JY: The renal hemodynamic and functional effects of external counterpressure. Surg Gynecol Obstet 134:253-258, 1972. 17. Civetta JM, Nussenfeld JD, Rowe TR, et al: Prehospital use of the military antishock trouser (MAST). JACEP 5:581-587, 1976.
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23. Cangiano TL, Kest L: Use of a g-suit for uncontrollable bleeding after percutaneous renal biopsy. J Urol 107:360-361, 1972. 24. Ransom KJ: Respiratory function following application of MAST trousers. JACEP 7:15-17, 1978. 25. Wayne MA: The MAST suit in the treatment of cardiogenic shock. JACEP 7:107-109, 1978. 26. Forrester JF, Diamond G, Chatterjee K, et al: Medical therapy of acute myocardial infarction by application of hemodynamic subsets, part I. N Engl J Med 295:1356-1362, 1976. 27. Forrester JF, Diamond G, Chatterjee K, et al: Medical therapy of acute myocardial infarction by application of hemodynamic subsets, part II. N Engl J Med 295:1404-1413, 1976. /
.
28. Schiff M: Recueil des Memo~res Physiologiques, vol 3, Lausanne, Benda, 1896. 29. Wiggers CJ: The physiologic basis for cardiac resuscitation from ventricular fibrillation - - method for serial defibrillation. Am Heart J 40:413-422, 1940. 30. Ohomoto T, Miura I, Kouno S: A new method of external cardiac massage to improve diastolic a u g m e n t a t i o n and prolong survival time. Ann Thorac Surg 21:284-290, 1976. 31. Criley JM, Blaufuss AH, Kissel GL: Cough-induced cardiac compression: selfadministered form of cardiopulmonary resuscitation. JAMA 236:1246-1250, 1976. 32. Niemann JT, Rosborough J, Hausknecht M, et al: Cough-CPR: documentation of systemic perfusion in man and in an experimental model. A '~window" to the mechanism of blood flow in external CPR. Crit Care Med 8:141-146, 1980. 33. Rudikoff MT, Maughan WL, Effron M, et al: Mechanism of blood flow during cardiopulmonary resuscitation. Circulation 61:345-352, 1980. 34. Babbs CF: New versus old theories of blood flow during cardiopulmonary resuscitation. Crit Care Med 8:191-195, 1980.
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External Counterpressure and the MAST Suit: Current and Future Roles Jerome R. Hoffman, MD Los Angeles, California
External counterpressure devices, such as the MAST suit, may be lifesaving not only in acute hypovolemia secondary to abdominal, pelvic and lower extremity trauma, but in a number of other shock states as well. Expanded use of the MAST suit may well include not qnly supra-diaphragmatic injuries, but diverse entities such as pericardial tamponade, tension pneumothorax, and leaking aortic aneurysm, and as an adjunct to cardiopulmonary resuscitation. The limited adverse effects of the MAST suit, in conjunction with its rapidly favorable and rapidly reversible hemodynamic effect, make it an important tool not only in prehospital care and in the emergency department, but in a wide variety of hospital circumstances. For this reason emergency physicians must not only be aware of uses of the MAST suit themselves, but should be prepared to disseminate this information to the general medical c o m m u n i t y . . H o f f m a n JR: External counterpressure and the MAST suit: current and future roles. Ann Emerg Med 9:419-421, August 1980.
external counterpressure devices, military antishock trousers; MAST suit, treatment of shock; military antishock trousers; shock, therapy, military antishock trousers INTRODUCTION A variety of devices have been used to produce external counterpressure on the lower extremities and abdomen. Though Crile first described the successful use of this technique in the t r e a t m e n t of hypovolemic shock, 1 it is only recently t h a t such devices have attracted a t t e n t i o n in the broad medical community. While those of us i n emergency medicine and prehospital care have been gaini n g increased experience with external counterpressure over the past several years, a lead article 2 and editorial 3 in the Journal of the American Medical Association as recently as F e b r u a r y 1979 make it clear t h a t most of the medical c o m m u n i t y r e m a i n u n f a m i l i a r with, and even suspicious of, this technique. There are a n u m b e r of external counterpressure devices, of which the most f r e q u e n t l y used is the Military Anti-Shock Trousers, or MAST suit. (For simplicity's sake, we will refer to the group of these devices as the MAST suit.) The MAST suit is an inflatable trouser device which can produce t i t r a t a b l e increased external pressure on the lower extremities and abdomen. Despite Crile's early work, the technique of external counterpressure was generally abandoned with the advent of blood transfusion; interest was revived, p a r t i c u l a r l y d u r i n g the V i e t n a m War, where field casualties with hemorrhagic shock secondary to lower extremity and abdominal injuries were repeatedly resuscitated using a MASTtype device as part of the regimen, n Since t h a t time, m a n y case reports have From the Department of Medicine, UCLA Hospital and Clinics, The Center for the Health Sciences, Los Angeles, California. Address for reprints: Jerome R. Hoffman, MD, Assistant Professor of Medicine, UCLA Hospit a l and Clinics, The Center for the Health Sciences, Los Angeles, California 90024.
9:8 (August) 1980
Ann
Emerg M e d
419/39
documented the successful use of the M A S T suit in a variety of situations in which lower extremity, abdominal, and pelvic bleeding has produced hypovolemic shock. 5-1~ The J A M A a r t i c l e 2 cites 174 case reports dealing with MAST suit usage, but correctly notes t h a t the t r u e c l i n i c a l s a m p l e of p a t i e n t s treated with the MAST suit is, i n fact, far larger. MAST suit use i n prehospital care has become almost routine in m a n y large centers over the past several years. 2 Despite the a b u n d a n c e of clinical case reports a n d t h e e v e n g r e a t e r anecdotal experience with the MAST device, only l i m i t e d s t u d i e s h a v e been done to elucidate the hemodyn a m i c effects of the MAST suit. ~2-14 These hemodynamic effects seem to be related primarily to two factors: t h e r e is a r e d i s t r i b u t i o n of venous blood flow from the lower extremities a n d a b d o m e n to o r g a n s above the diaphragm; and there is a direct effect on e x t r a l u m i n a l a r t e r i a l a n d venous pressure in the areas covered by the suit. Application of the trousers is accompanied by a rise in central venous pressure and a n increase in aortic and carotid flow and pressure, with a concomitant decrease in femoral flow and pressure. There is also an increase in systemic vascular resistance, arterial blood pressure (as measured in the upper extremities), and cardiac stroke volume. Cardiac output r e m a i n s unchanged, however, as increased stroke volume is accompanied by decreased heart rate. 12-~4 It has been assumed generally that the b r a d y c a r d i a noted with MAST suit use is a result of a depressor reflex s t i m u l a t i o n s e c o n d a r y to increased arterial pressure in the aorta a n d carotid sinus. This reflex response may be more limited in pat i e n t s with n o r m a l blood p r e s s u r e t h a n in hypovolemic patients with hypotension, 2 as we have also noted it in an ongoing study of patients in paroxysmal atrial tachycardia treated with the MAST suit (J. Hoffman, u n p u b l i s h e d data). Morbidity from the use of the MAST suit, apart from local trophic skin Changes, has been limited generally to mild degrees of lactic acidosis secondary to decreased lower ext r e m i t y blood flow f o l l o w i n g prol o n g e d usage. 2,15-1s N e v e r t h e l e s s , several i n v e s t i g a t o r s have applied external counterpressure over periods as long as 40 h r and more without notable systemic acidosis.2,19-2~ This is particularly true when MAST suit pressures of 20 m m Hg to 40 m m
40/420
Hg, rather t h a n the m a x i m a l inflation of 104 m m Hg, have been used. Decreased u r i n a r y output and glome r u l a r filtration rates associated with p r o l o n g e d u s e of M A S T d e v i c e s have never been associated with changes in renal t u b u l a r metabolic f u n c t i o n a n d are of q u e s t i o n a b l e if a n y s i g n i f i c a n c e . 2,1~,19,21-23 O t h e r s i g n i f i c a n t m o r b i d i t y m a y occur in p a t i e n t s with specialized problems. The MAST suit, by d i s t r i b u t i n g a larger volume of blood to structures above the diaphragm, increases the venous r e t u r n to the lungs and thus causes the p u l m o n a r y wedge pressure to rise. This certainly could be deleterious in p a t i e n t s with congestive heart failure and pulmonary edema. Slight decreases in respiratory excursion secondary to abdominal compression have not been shown to have significant clinical effects,l°,~7, 24 but may be i m p o r t a n t in patients with already diminished l u n g function. Concern also has been raised a b o u t increased b l e e d i n g in p a t i e n t s with chest and head injuries with use of the MAST suit. It seems clear t h a t the MAST suit is a valuable adjunct to acute resuscitation of patients with hypovolemic shock secondary to lower ext r e m i t y and abdominal bleeds. This has been well documented, and the JAMA article and accompanying editorial, which adds t h a t ~skeptics a r e e n c o u r a g e d to g i v e it a f a i r trial,"2, z i l l u s t r a t e t h a t such docum e n t a t i o n is now becoming available to more t h a n just those who practice e m e r g e n c y medicine.2,3 Other uses for the MAST device are more controversial. One area in which use of the MAST suit would seem to make sense, but about which there has been no clinical evidence, is t h a t of the relative hypovolemia of such conditions as pericardial tamponade and tension p n e u m o t h o r a x . While total blood volumes in these situations may well be normal, hypot e n s i o n occurs s e c o n d a r y to decreased venous r e t u r n and decreased filling of the h e a r t because of the underlying abnormality. Temporary p r e h o s p i t a l use of the MAST suit, p r i o r to a v a i l a b i l i t y of d e f i n i t i v e therapy, would appear to afford several benefits: it provides a rapid increase i n thoracic blood volume; it increases venous r e t u r n u n d e r pressure; and it is quickly reversible once the u n d e r l y i n g lesion is corrected. Similarly in patients with electromechanical dissociation, the MAST suit m a y h a v e some r e a l v a l u e . T h e m a j o r i t y of such p a t i e n t s are, of
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c o u r s e , n o t s a l v a g e a b l e , as elec-: tromechanical dissociation is gener-1 ally a reflection of a dying heart. It I m a y occasionally reflect massive acute hypovolemia, however, and in such circumstances dramatic volume r e d i s t r i b u t i o n with the MAST suit m i g h t be s u c c e s s f u l , w h i l e tradit i o n a l therapy, with drugs such as isoproterenol, e p i n e p h r i n e and calcium, rarely contributes to long-term survival. It s h o u l d be r e m e m b e r e d t h a t clinical documentation of such use has not yet appeared in the medical literature. There has been a modicum of interest in usage of the MAST suit in o t h e r forms of shock, p a r t i c u l a r l y cardiogenic shock. The sole published report on this subject 25 purports to d e m o n s t r a t e increased survival with prehospital use of the MAST suit in cardiogenic shock. However, careful perusal of that study reveals several major problems in the design, and it is far from clear whether any of the p a t i e n t s who b e n e f i t e d from this therapy did, in fact, suffer from cardiogenic shock. T h e o r e t i c a l l y it is h a r d to i m a g i n e the MAST suit being of use in pump failure, except in that s m a l l group of p a t i e n t s designated Class III by the Forrester 26,27 classification of acute myocardial infarct i o n , ie, those in shock f o l l o w i n g acute myocardial infarction because of relative hypovolemia and not intrinsic pump failure. Such p a t i e n t s do occasionally r e s p o n d to v o l u m e t h e r a p y , a n d in t h a t i n s t a n c e , the M A S T s u i t m a y well be of e q u a l value. In the large majority of pat i e n t s with cardiogenic shock, forward pump failure is associated with backward fluid overload and elevated wedge pressures; i n these p a t i e n t s the MAST suit, like volume therapy, is probably deleterious. Its f u r t h e r effect of i n c r e a s i n g t h e a f t e r l o a d a g a i n s t which the failing heart must p u m p would seem to compound the hazard. There also has been recent interest in the use of external counterpressure d u r i n g cardiopulmonary resuscitation (CPR), and several clinical trials now are being u n d e r t a k e n with this in mind. While simplified versions of this method were undert a k e n m a n y years ago, 2s,29 there are l i m i t e d good e x p e r i m e n t a l data on the subject. In a 1974 report, 15 dogs receiving abdominal compression d u r i n g CPR did significantly better t h a n controI clogs and methoxaminet r e a t e d dogs2 A J a p a n e s e study in 1976 demonstrated t h a t increases of coronary and carotid flow up to two-
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fold, as well as i n c r e a s e d s u r v i v a l , could be obtained with selective diastolic abdominal compression during CPR. 3° We now know t h a t circulation during CPR occurs because of increases in i n t r a t h o r a c i c p r e s s u r e during chest compression. 31-34 We might, therefore, predict a decrease in cardiac output (and thus perfusion) when the s t a n d a r d i n t r a t h o racic pressure change b r o u g h t about during CPR occurs in the face of significantly higher resistance produced by a MAST device, p a r t i c u l a r l y when that device is not capable of selective diastolic c o u n t e r p r e s s u r e . On t h e other hand, decreased d i a p h r a g m a t i c excursion s e c o n d a r y to a b d o m i n a l binding might increase the degree of intrathoracic p r e s s u r e r i s e d u r i n g compression, and thus i n c r e a s e total cardiac output wh i le selectively increasing flow to the carotids. F u r t h e r investigation of continuous or intermittent abdominal c o u n t e r p r e s s u r e during cardiac arrest is w a r r a n t e d . Use of the MAST suit in hypovolemic shock s e c o n d a r y to i n j u ries above the d i a p h r a g m r e m a i n s controversial. Op p o n e n ts of its use suggest that redistribution of blood to an area of h e m o r r h a g e will only increase total blood loss and, therefore, is c o n t r a i n d i c a t e d . H o w e v e r , there are two theoretical a d v a n t a g e s even in t h e s e c i r c u m s t a n c e s . T h e first is t h a t t h e a c u t e i n c r e a s e in blood flow to v i t a l o r g a n s (ie, th e heart and brain) m a y be life-saving as a method of buying time, despite eventual increased total blood loss. This, of course, presumes acute hypotension and the e a r ly a v a i l a b i l i t y of more d e f i n i t i v e m e a s u r e s . Second, decreased cerebral blood flow is associated w i t h i n c r e a s e d c e r e b r a l edema. In this case, a M A S T s u i t may, by r e d i s t r i b u t i n g flow, help to decrease cerebral edema. It should be noted that there h a v e been no clinical or e x p e r i m e n t a l trials to e v a l u a t e the effect of e x t e r n a l counterpressure in such an instance.
SUMMARY Emergency physicians h a v e had to deal with the ignorance of and resistance to use of the MAST suit by other physicians. F o r t u n a t e l y , t h e broad medical c o m m u n i t y is becoming a w a r e of t h e M A S T s u i t a n d , perhaps grudgingly, i n t e r e s t e d in its use. Those of us in e m e r g e n c y medicine who have relied on the MAST devices in t h e p a s t m u s t b e c o m e more completely a w a r e of t h e i r uses, potential, and possible contraindications.
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REFERENCES 1. Crile GW: Blood Pressure in Surgery: Experimental and Clinical Research. Philadelphia, JB Lippincott Co, 1903, p 288-291. 2. Pelligra R, Sandberg EC: Control of intractable abdominal bleeding by external counterpressure. JAMA 241:708-713, 1979.
18. Ransom KJ: Metabolic acidosis with pneumatic trousers in hypovolemic dogs. JACEP 8:184-187, 1979. 19. McLaughlin AP, McCullough DL, Kerr WS Jr, et al: The use of the external counterpressure (g-suit) in management of traumatic retroperitoneal hemorrhage. J Urol 107:940-944, 1972.
3. Carden TS: A fair trial for CPC (editorial). JAMA 241:729, 1979.
20. Batalden DJ, Wickstron PH, Ruiz E, et al: Value of the g-suit in patients with severe pelvic fracture. Arch Surg 109: 326-328, 1974.
4. Cutler BS, Daggett W: Application of the g-suit to the control of hemorrhage in massive trauma. Ann Surg 173:511-514, 1971.
21. Burdick JF, Warshaw AL, AbboLt WM: External counterpressure to control postoperative intra-abdominal hemorrhage. Am J Surg 129:369-373, 1975.
5. Gardner WJ, Taylor HP, Dohn DF: Acute blood loss requiring 58 transfusions: The use of anti-gravity suit as an aid to post-partum intra-abdominal hemorrhage. JAMA 167:985-986, 1958.
22. Roth JS, Rutherford RB: Regional blood flow effect of g-suit application during hemorrhagic shock. Surg Gynecol Obstet 133:637-643, 1971.
6. Gardner WJ, Storer J: The use of the g-suit in control of intra-abdominal bleeding. Surg Gynecol Obstet 123:792-798, 1966. 7. Ludewig RM, Wangensteen SL: Aortic bleeding and the effect of external counterpressure. Surg Gynecol Obstet 128:252258, 1969. \
8. Wangensteen SL, Ludewig RM, Cox JM, et al: The effect of external counterpressure on arterial bleeding. Surgery 64:922-927, 1968. 9. Redding JS: Abdominal compression in cardiopulmonary resuscitation. Anesth Analg 50:668-675, 1971. 10. Espinosa MS, Updegrove JS: Clinical experience with the g-suit. Arch Surg 101:36, 1970. 11. McCullough DL, McLaughlin AP, Warshawsky AB: The gravity suit. A useful device in complicated urologic hemorrhage. Urology 6:468-470, 1975. 12. Wangensteen SL, Ludewig RM, Eddy DW: Effect of external counterpressure on the intact circulation. Surg Gynecol Obstet 127:253-258, 1968. 13. Gray S, Shaver JA, Kroetz FW, et al: Acute and prolonged effects of g-suit inflation on cardiovascular dynamics. Circulation (supp II) 35, 36:125, 1967. 14. Gray S, Shaver JA, Kroetz FW, et al: Acute and prolonged effects of g-suit inflation on cardiovascular dynamics. Aerospace Med 40:40-43, 1969. 15. Wangensteen SL, deHoll JD, Ludewig RM, et al: The detrimental effect of the g-suit in hemorrhagic shock. An n Surg 170:187-192, 1969. 16. Shenasky JH, Gillenwater JY: The renal hemodynamic and functional effects of external counterpressure. Surg Gynecol Obstet 134:253-258, 1972. 17. Civetta JM, Nussenfeld JD, Rowe TR, et al: Prehospital use of the military antishock trouser (MAST). JACEP 5:581-587, 1976.
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23. Cangiano TL, Kest L: Use of a g-suit for uncontrollable bleeding after percutaneous renal biopsy. J Urol 107:360-361, 1972. 24. Ransom KJ: Respiratory function following application of MAST trousers. JACEP 7:15-17, 1978. 25. Wayne MA: The MAST suit in the treatment of cardiogenic shock. JACEP 7:107-109, 1978. 26. Forrester JF, Diamond G, Chatterjee K, et al: Medical therapy of acute myocardial infarction by application of hemodynamic subsets, part I. N Engl J Med 295:1356-1362, 1976. 27. Forrester JF, Diamond G, Chatterjee K, et al: Medical therapy of acute myocardial infarction by application of hemodynamic subsets, part II. N Engl J Med 295:1404-1413, 1976. /
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28. Schiff M: Recueil des Memo~res Physiologiques, vol 3, Lausanne, Benda, 1896. 29. Wiggers CJ: The physiologic basis for cardiac resuscitation from ventricular fibrillation - - method for serial defibrillation. Am Heart J 40:413-422, 1940. 30. Ohomoto T, Miura I, Kouno S: A new method of external cardiac massage to improve diastolic a u g m e n t a t i o n and prolong survival time. Ann Thorac Surg 21:284-290, 1976. 31. Criley JM, Blaufuss AH, Kissel GL: Cough-induced cardiac compression: selfadministered form of cardiopulmonary resuscitation. JAMA 236:1246-1250, 1976. 32. Niemann JT, Rosborough J, Hausknecht M, et al: Cough-CPR: documentation of systemic perfusion in man and in an experimental model. A '~window" to the mechanism of blood flow in external CPR. Crit Care Med 8:141-146, 1980. 33. Rudikoff MT, Maughan WL, Effron M, et al: Mechanism of blood flow during cardiopulmonary resuscitation. Circulation 61:345-352, 1980. 34. Babbs CF: New versus old theories of blood flow during cardiopulmonary resuscitation. Crit Care Med 8:191-195, 1980.
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