- Email: [email protected]
Thoracic cavity lavage for cardiac arrest
didate will probably then be involved in a busy PGY 1, where program directors are not going to be receptive to requests for absences for interviewing. This situation could well lead to the student spending much more time and energy in selecting his PGY 1 program than in selecting his residency training program. Certainly candidates applying for PGY 2 spots during their PGY 1 have a year more of clinical experience. How significant this is in helping either the candidate or the program director to make a selection is unknown: It is very doubtful that program directors making careful selections based on medical school performance are going to find that the residency performance of the candidates selected is markedly different. Achievers tend to continue to be achievers, especially if they are self-educators as physicians should be. In a meeting on transition from medical school to residency in Washington, DC, Dr John Graettinger; Executive Vice President of the National Resident Matching Program, described the greater diversity in background of those applying to the PGY 2 specialty match as compared with those applying during the fourth year of medical school and the significantly lower success rate in the match for that group. Those who have been out of medical school more than a year tend to be a very heterogeneous group that has less
success with the match. While some may be more mature, most are not on a par academically with senior medical students. Many programs have found that while some members of this third group may exCel, there is also a high potential for "dropping out," particularly among those who have been in practice prior to entering the residency. It seems that a specialty as broad as emergency medicine, with programs of varying length, philosophy, and purpose, can well accommodate these programs with more than one type of matching process. While the availability of both advanced and PGY 2 specialty matches may be confusing to applicants and may lead to loss of top-ranked students by programs participating in the PGY 2 specialty match, there seems to be no overwhelming reason why both cannot be available and well used by the appropriate programs.
Mary Ann Cooper, MD, FACEP Gary R Strange, MD, FACEP University of Illinois Affiliated Hospitals Emergency Medicine Residency Chicago, Illinois 1. Sloan EP, Strange GR, Jayne HA: United States emergency medicine residency length in 1986-87 & I987-88. Ann Emerg Med 1987;16:862-866. 2. Sloan EP, Hayden R, Cooper MA, et al: Factors involved in selection of emergency medicine residents (abstract). Ann Emerg Med 1987;16:505.
T h o r a c i c C a v i t y L a v a g e for C a r d i a c A r r e s t To the Editor: In the article "Comparison of Gastric Lavage and Thoracic Cavity Lavage in the Treatment of Severe Hypothermia in Dogs" [November 1987;1611222-1227], Brunette et al described a method of rewarming investigated by us in 1984.1 In our pilot study involving six severely hypothermic dogs, warmed saline (42 C) was introduced into the thoracic cavity through one chest tube and removed through a tube using Pleurevac ® suction at a rate of 4 L/hour. The rewarming rates achieved using rectal temperatures were similar to the authors' rates. However, several points need to be raised about thoracic cavity lavage. In our study, thoracic cavity lavage (TCL) led to hypoxemia (corrected by the administration of supplemental oxygen) and the development of significant A-a gradients. The etiology of hypoxemia was not addressed by the authors, although in their study there was an average drop in pO 2 of 84 m m Hg in group 2 despite the use of supplemental oxygen, while group 1 had an average rise in pO 2 of 74 m m Hg: In our study, autopsies done immediately at the conclusion of rewarming with thoracic cavity irrigation revealed capillary congestion and varying degrees of microscopic pulmonary damage, which could help explain the hypoxemia dilemma. Elsewhere in the article, the authors leave undetermined the exact role of TCL for patients in full cardiac arrest. In our preliminary study, we tested TCL with closed CPR on two dogs in cardiac arrest, and chest wall subcutaneous edema developed. Intermittent expulsion of saline from the thoracic cavity also Occurred through the thoracostomy 17:9 September 1988
sites when external cardiac compressions were performed, and the overall rewarming rates were slower. These results confirm that further problems may occur when TCL is used for patients in full cardiac arrest. Additionally, at the time of our study, critics raised the issue of myocardial thermal gradients. Mouritzen and Andersen raised the possibility that nonuniform rewarming of the heart could lead to an increased risk of ventricular fibrillation, z Although none of the dogs rewarmed by thoracic irrigation in our study developed ventricular fibrillation during the rewarming phase, two dogs from each of the authors' groups did, and this issue needs to be addressed. Several other questions must also be raised. How did the authors arrive at an infusion rate of 550 mL/min and a lavvage fluid temperature of 39 C? Why were three chest tubes placed instead of just two tubes as was done in our study? Why was gastric lavage used as the control method instead of peritoneal lavage, a faster method of active rewarming? It would seem that further description of the authors' lavage system (ie, heat exchanger, infusion device, fluid bath, and suction device) is necessary to understand the complexity or simplicity of this rewarming technique before it can be deemed a practical method for smaller, rural hospitals.
Pankaj B Patel, MD Emergency Department Chinle Hospital Chinle, Arizona 1. Patel PB, Caplen S, Bellini R, et al: Chest tube mediastinal irrigation:
Annals of EmergencyMedicine
998/195
CORRESPONDENCE
An alternative approach to the treatment of severe hypothermia in dogs (abstract). Ann Emerg Med 1984;13:991. 2. Mouritzen CV, Andersen MN: Myocardial temperature gradients and ventricular fibrillation during hypothermia. J Thorac Cardiovasc Surg 1965;49:937-944.
In Reply: I thank Dr Patel for his comments. He raises several interesting questions that i would like to address. The thoracic cavity lavage that Dr Patel used in his study (reference 1) was accomplished by using two thoracostomy tubes not connected tO a continuous system that could deliver constant flow rates and temperature. Dr Patel demonStrated a rectal temperature increase rate of 3.76 C/hr using a flow rate of 33 L/hr. Our system used a flow rate of 33 L/ hr and had a rectal rewarming rate of 4.5 C/hn These rectal temperature rates are probably comparable. It is tree that the thoracic cavity lavage animals demonstrated a decrease in their pO 2 values immediately following the lavage process, leading to an increased A-a gradient. However, no animal was ever hypoxemic (reduced saturation). The etiology of this increased A-a gradient is not known. Dr Patel sacrificed his animals immediately, with no clinical outcome available. AS stated in our article, all animals were followed clinically, with minimal pulmonary sequelae and normal blood gases at 24 hours. We feel that the rewarming method of choice for patients in cardiac arrest from severe hypothermia is cardiopulmonary bypass. If this is not feasible, then thoracotomy with
mediastinal lavage provides for direct cardiac massage and very efficient core rewarming. The role of closed thoracic lavage in human beings, with or without cardiac arrest, has not been determined. We feel Clinical trials are warranted and needed to determine the utility of this technique. Differential myocardial rewarming might play a role in the development of significant dysrhythmias. We did not see any difference in development of ventricular fibrillation during rewarming in our two groups. The infusion rate and lavage fluid temperature were determined empirically. A third chest tube was placed into the right hemithorax because the canine mediastinum is frequently incomplete, allowing lavage fluid to enter the right chest cavity. Indeed, we recovered a significant amount of fluid from the right thorax during the lavage. Although we tried very hard, we were unable to use the system described in the peritoneal cavity. The canine omentum prevented the flow rates and adequate return that were used in the thorax. We wanted to compare the same system at different lavage sites rather than compare two different systems at different sites. Finally, the system was composed of a heat exchanger (Dideco, Inc), a fluid bath (Cardiovascular Instruments Corp), an infusion device (Cardiovascular Instrument Corp), and an Emerson pump as a suction device.
Douglas Brunette, MD Hennepin County Medical Center Minneapolis, Minnesota
Chest Tube Irrigation for Postinjury Hypothermia To the Editor: We commend Brunette et al for completing a very practical canine study to which we would like to add corroboration f r o m clinical experience. A l t h o u g h the dog's incomplete mediastinum may favor thoracic lavage compared with t h e human counterpart , and peritoneal lavage may be more efficient than gastric, the results of this study are too compelling to ignore the clinical implications. Our interest in "accidental" hypothermia has focused on the injured patient in whom an abrupt fall in body temperature may have a disastrous effect on coagulation function, a common scenario following major hepatic trauma. TM For th e past seven years, we have routinely warmed resuscitation crystalloid solution to 40 C in incubators maintained both in the trauma room of the emergency department and designated trauma room in the operating room. In addition, the anesthesiologists place cascades On the ventilators in the OR to heat and humidify inhalation products. In our earlier experience we used open thoracic and abdominal lavage, but were uniformly disappointed in the rate of heat exchange. Moreover, the irrigating saline frequently spilled into the operative field, obscuring the visceral lesion as well as the rate of ongoing blood loss. About two years ago, we fortuitously irrigated the chest tubes of a hypothermic patient who had undergone laparotomy, and were im196/999
pressed with the rapid rise in core temperature. With additional clinical confirmation of this observation, closed thoracic lavage became our preferred method for reversing intraoperative hypothermia. We believe heat exchange is far more efficient when the chest is closed rather than open to ambient temperature. At a subsequent trauma meeting, we discovered that C William Schwab, MD, of Philadelphia and colleagues had learned the same principle. In fact, we had contemplated a joint clinical report on the procedure, as well as an animal model to verify the phenomenon. The excellent study by the Hennepin County group fortunately renders the latter exercise unnecessary. Our technique for intraoperative thoracic lavage of the hypothermic trauma patient consists of placing two 28-F chest tubes in the uninjured pleural cavity. Normal saline, warmed to 40 C, is infused and retrieved by simple gravity. The circulating OR nurse reconciles output versus input to ensure the unlikely occurrence of tension hydrothorax due to chest tube malfunction. Because the visceral pleura has not been violated, these chest tubes may be removed in the early pOstoperative period despite the need for continued mechanical ventilation. We have not observed cardiac, pulmonary, or pleural complications from this technique; this probably represents an experience of more than 50 acutely
Annals of Emergency Medicine
17:9 September 1988
success with the match. While some may be more mature, most are not on a par academically with senior medical students. Many programs have found that while some members of this third group may exCel, there is also a high potential for "dropping out," particularly among those who have been in practice prior to entering the residency. It seems that a specialty as broad as emergency medicine, with programs of varying length, philosophy, and purpose, can well accommodate these programs with more than one type of matching process. While the availability of both advanced and PGY 2 specialty matches may be confusing to applicants and may lead to loss of top-ranked students by programs participating in the PGY 2 specialty match, there seems to be no overwhelming reason why both cannot be available and well used by the appropriate programs.
Mary Ann Cooper, MD, FACEP Gary R Strange, MD, FACEP University of Illinois Affiliated Hospitals Emergency Medicine Residency Chicago, Illinois 1. Sloan EP, Strange GR, Jayne HA: United States emergency medicine residency length in 1986-87 & I987-88. Ann Emerg Med 1987;16:862-866. 2. Sloan EP, Hayden R, Cooper MA, et al: Factors involved in selection of emergency medicine residents (abstract). Ann Emerg Med 1987;16:505.
T h o r a c i c C a v i t y L a v a g e for C a r d i a c A r r e s t To the Editor: In the article "Comparison of Gastric Lavage and Thoracic Cavity Lavage in the Treatment of Severe Hypothermia in Dogs" [November 1987;1611222-1227], Brunette et al described a method of rewarming investigated by us in 1984.1 In our pilot study involving six severely hypothermic dogs, warmed saline (42 C) was introduced into the thoracic cavity through one chest tube and removed through a tube using Pleurevac ® suction at a rate of 4 L/hour. The rewarming rates achieved using rectal temperatures were similar to the authors' rates. However, several points need to be raised about thoracic cavity lavage. In our study, thoracic cavity lavage (TCL) led to hypoxemia (corrected by the administration of supplemental oxygen) and the development of significant A-a gradients. The etiology of hypoxemia was not addressed by the authors, although in their study there was an average drop in pO 2 of 84 m m Hg in group 2 despite the use of supplemental oxygen, while group 1 had an average rise in pO 2 of 74 m m Hg: In our study, autopsies done immediately at the conclusion of rewarming with thoracic cavity irrigation revealed capillary congestion and varying degrees of microscopic pulmonary damage, which could help explain the hypoxemia dilemma. Elsewhere in the article, the authors leave undetermined the exact role of TCL for patients in full cardiac arrest. In our preliminary study, we tested TCL with closed CPR on two dogs in cardiac arrest, and chest wall subcutaneous edema developed. Intermittent expulsion of saline from the thoracic cavity also Occurred through the thoracostomy 17:9 September 1988
sites when external cardiac compressions were performed, and the overall rewarming rates were slower. These results confirm that further problems may occur when TCL is used for patients in full cardiac arrest. Additionally, at the time of our study, critics raised the issue of myocardial thermal gradients. Mouritzen and Andersen raised the possibility that nonuniform rewarming of the heart could lead to an increased risk of ventricular fibrillation, z Although none of the dogs rewarmed by thoracic irrigation in our study developed ventricular fibrillation during the rewarming phase, two dogs from each of the authors' groups did, and this issue needs to be addressed. Several other questions must also be raised. How did the authors arrive at an infusion rate of 550 mL/min and a lavvage fluid temperature of 39 C? Why were three chest tubes placed instead of just two tubes as was done in our study? Why was gastric lavage used as the control method instead of peritoneal lavage, a faster method of active rewarming? It would seem that further description of the authors' lavage system (ie, heat exchanger, infusion device, fluid bath, and suction device) is necessary to understand the complexity or simplicity of this rewarming technique before it can be deemed a practical method for smaller, rural hospitals.
Pankaj B Patel, MD Emergency Department Chinle Hospital Chinle, Arizona 1. Patel PB, Caplen S, Bellini R, et al: Chest tube mediastinal irrigation:
Annals of EmergencyMedicine
998/195
CORRESPONDENCE
An alternative approach to the treatment of severe hypothermia in dogs (abstract). Ann Emerg Med 1984;13:991. 2. Mouritzen CV, Andersen MN: Myocardial temperature gradients and ventricular fibrillation during hypothermia. J Thorac Cardiovasc Surg 1965;49:937-944.
In Reply: I thank Dr Patel for his comments. He raises several interesting questions that i would like to address. The thoracic cavity lavage that Dr Patel used in his study (reference 1) was accomplished by using two thoracostomy tubes not connected tO a continuous system that could deliver constant flow rates and temperature. Dr Patel demonStrated a rectal temperature increase rate of 3.76 C/hr using a flow rate of 33 L/hr. Our system used a flow rate of 33 L/ hr and had a rectal rewarming rate of 4.5 C/hn These rectal temperature rates are probably comparable. It is tree that the thoracic cavity lavage animals demonstrated a decrease in their pO 2 values immediately following the lavage process, leading to an increased A-a gradient. However, no animal was ever hypoxemic (reduced saturation). The etiology of this increased A-a gradient is not known. Dr Patel sacrificed his animals immediately, with no clinical outcome available. AS stated in our article, all animals were followed clinically, with minimal pulmonary sequelae and normal blood gases at 24 hours. We feel that the rewarming method of choice for patients in cardiac arrest from severe hypothermia is cardiopulmonary bypass. If this is not feasible, then thoracotomy with
mediastinal lavage provides for direct cardiac massage and very efficient core rewarming. The role of closed thoracic lavage in human beings, with or without cardiac arrest, has not been determined. We feel Clinical trials are warranted and needed to determine the utility of this technique. Differential myocardial rewarming might play a role in the development of significant dysrhythmias. We did not see any difference in development of ventricular fibrillation during rewarming in our two groups. The infusion rate and lavage fluid temperature were determined empirically. A third chest tube was placed into the right hemithorax because the canine mediastinum is frequently incomplete, allowing lavage fluid to enter the right chest cavity. Indeed, we recovered a significant amount of fluid from the right thorax during the lavage. Although we tried very hard, we were unable to use the system described in the peritoneal cavity. The canine omentum prevented the flow rates and adequate return that were used in the thorax. We wanted to compare the same system at different lavage sites rather than compare two different systems at different sites. Finally, the system was composed of a heat exchanger (Dideco, Inc), a fluid bath (Cardiovascular Instruments Corp), an infusion device (Cardiovascular Instrument Corp), and an Emerson pump as a suction device.
Douglas Brunette, MD Hennepin County Medical Center Minneapolis, Minnesota
Chest Tube Irrigation for Postinjury Hypothermia To the Editor: We commend Brunette et al for completing a very practical canine study to which we would like to add corroboration f r o m clinical experience. A l t h o u g h the dog's incomplete mediastinum may favor thoracic lavage compared with t h e human counterpart , and peritoneal lavage may be more efficient than gastric, the results of this study are too compelling to ignore the clinical implications. Our interest in "accidental" hypothermia has focused on the injured patient in whom an abrupt fall in body temperature may have a disastrous effect on coagulation function, a common scenario following major hepatic trauma. TM For th e past seven years, we have routinely warmed resuscitation crystalloid solution to 40 C in incubators maintained both in the trauma room of the emergency department and designated trauma room in the operating room. In addition, the anesthesiologists place cascades On the ventilators in the OR to heat and humidify inhalation products. In our earlier experience we used open thoracic and abdominal lavage, but were uniformly disappointed in the rate of heat exchange. Moreover, the irrigating saline frequently spilled into the operative field, obscuring the visceral lesion as well as the rate of ongoing blood loss. About two years ago, we fortuitously irrigated the chest tubes of a hypothermic patient who had undergone laparotomy, and were im196/999
pressed with the rapid rise in core temperature. With additional clinical confirmation of this observation, closed thoracic lavage became our preferred method for reversing intraoperative hypothermia. We believe heat exchange is far more efficient when the chest is closed rather than open to ambient temperature. At a subsequent trauma meeting, we discovered that C William Schwab, MD, of Philadelphia and colleagues had learned the same principle. In fact, we had contemplated a joint clinical report on the procedure, as well as an animal model to verify the phenomenon. The excellent study by the Hennepin County group fortunately renders the latter exercise unnecessary. Our technique for intraoperative thoracic lavage of the hypothermic trauma patient consists of placing two 28-F chest tubes in the uninjured pleural cavity. Normal saline, warmed to 40 C, is infused and retrieved by simple gravity. The circulating OR nurse reconciles output versus input to ensure the unlikely occurrence of tension hydrothorax due to chest tube malfunction. Because the visceral pleura has not been violated, these chest tubes may be removed in the early pOstoperative period despite the need for continued mechanical ventilation. We have not observed cardiac, pulmonary, or pleural complications from this technique; this probably represents an experience of more than 50 acutely
Annals of Emergency Medicine
17:9 September 1988