Thiopental and phenytoin by aortic arch flush for cerebral preservation during exsanguination cardiac arrest of 20 minutes in dogs. An exploratory study

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

Emergency preservation and resuscitation for cardiac arrest from trauma

Patients who suffer a cardiac arrest from trauma rarely survive. Surgical control of hemorrhage cannot be obtained in time to prevent irreversible organ damage. Emergency preservation and resuscitation (EPR) was developed to utilize hypothermia to buy time to achieve hemostasis and allow delayed resuscitation. Large animal studies have demonstrated that cooling to tympanic membrane temperature 10 °C during exsanguination cardiac arrest can allow up to 2 h of circulatory arrest and repair of simulated injuries with normal neurologic recovery. The Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT) trial is testing the feasibility and safety of initiating EPR. Study subjects include patients with penetrating trauma who lose a pulse within 5 minutes of hospital arrival and remain pulseless despite standard care. EPR is initiated via an intra-aortic flush of ice-cold saline solution. Following hemostasis, delayed resuscitation and rewarming are accomplished with cardiopulmonary bypass. The primary outcome is survival to hospital discharge without significant neurologic deficits. If trained team members are available, subjects can undergo EPR. If not, subjects can be enrolled as concurrent controls. Ten EPR and 10 control subjects will be enrolled. If successful, EPR could save the lives of trauma patients who are currently dying from exsanguinating hemorrhage.

Suspended animation: the past, present and future of major cardiothoracic trauma

About 50% of the trauma victims die at the scene mostly because of exsanguinating haemorrhage. Most trials of resuscitation fail in face of the ongoing bleeding. Ongoing research/studies to save these victims by inducing rapid hypothermia using cardiopulmonary bypass as an emergency initial measure along with delayed resuscitation show improved outcomes. A comprehensive review of this research and analysis of studies showed that rapid induction of hypothermia within 5 min of cardiac arrest is associated with better survival and improved neurological outcome. This led us to conclude that suspended animation is a lifesaving modality for the treatment of trauma victims, otherwise hurtling towards certain death. This should be integrated into regular clinical practice. The US Food and Drug Administration has given its approval for clinical trials on such an intervention.

Development of the emergency preservation and resuscitation for cardiac arrest from trauma clinical trial

BACKGROUND

Patients who suffer a cardiac arrest from trauma rarely survive, even with aggressive resuscitation attempts, including an emergency department thoracotomy. Emergency Preservation and Resuscitation (EPR) was developed to utilize hypothermia to buy time to obtain hemostasis before irreversible organ damage occurs. Large animal studies have demonstrated that cooling to tympanic membrane temperature 10°C during exsanguination cardiac arrest can allow up to 2 hours of circulatory arrest and repair of simulated injuries with normal neurologic recovery.

STUDY DESIGN

The Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma trial has been developed to test the feasibility and safety of initiating EPR. Select surgeons will be trained in the EPR technique. If a trained surgeon is available, the subject will undergo EPR. If not, the subject will be followed as a control subject. For this feasibility study, 10 EPR and 10 control subjects will be enrolled.

STUDY PARTICIPANTS

Study participants will be those with penetrating trauma who remain pulseless despite an emergency department thoracotomy.

INTERVENTIONS

Emergency Preservation and Resuscitation will be initiated via an intra-aortic flush of a large volume of ice-cold saline solution. Following surgical hemostasis, delayed resuscitation will be accomplished with cardiopulmonary bypass.

OUTCOME MEASURES

The primary outcome will be survival to hospital discharge without significant neurologic deficits. Secondary outcomes include long-term survival and functional outcome.

IMPLICATIONS

Once data from these 20 subjects are reviewed, revisions to the inclusion criteria and/or the EPR technique may then be tested in a second set of EPR and control subjects.

Irreversibility: cardiac death versus brain death

The acceptance of brain death (BD) as death of the human being has been progressively accepted beginning in the early 1960s. The issue of irreversibility is directly related to the diagnosis of human death, and it is closely associated with the concept of potentiality, i.e., that some patients still have the potentiality of living. In recent years several authors have proposed to use a cardiocirculatory criterion for death determination in transplant donors. This has aroused ethical and medical controversies regarding concerns to accept that a non-heart-beating donor is really dead. We conclude that the cardiocirculatory criterion of death only assures irreversibility when asystole is prolonged enough to assure that ischemia and anoxia have destroyed the brain. On the contrary, BD fulfills both requirements for death determination: cessation of functions and irreversibility

Emergency preservation and resuscitation with profound hypothermia, oxygen, and glucose allows reliable neurological recovery after 3 h of cardiac arrest from rapid exsanguination in dogs

We have used a rapid induction of profound hypothermia (<10 degrees C) with delayed resuscitation using cardiopulmonary bypass (CPB) as a novel approach for resuscitation from exsanguination cardiac arrest (ExCA). We have defined this approach as emergency preservation and resuscitation (EPR). We observed that 2 h but not 3 h of preservation could be achieved with favorable outcome using ice-cold normal saline flush to induce profound hypothermia. We tested the hypothesis that adding energy substrates to saline during induction of EPR would allow intact recovery after 3 h CA. Dogs underwent rapid ExCA. Two minutes after CA, EPR was induced with arterial ice-cold flush. Four treatments (n=6/group) were defined by a flush solution with or without 2.5% glucose (G+ or G-) and with either oxygen or nitrogen (O+ or O-) rapidly targeting tympanic temperature of 8 degrees C. At 3 h after CA onset, delayed resuscitation was initiated with CPB, followed by intensive care to 72 h. At 72 h, all dogs in the O+G+ group regained consciousness, and the group had better neurological deficit scores and overall performance categories than the O-groups (both P<0.05). In the O+G- group, four of the six dogs regained consciousness. All but one dog in the O-groups remained comatose. Brain histopathology in the O-G+ was worse than the other three groups (P<0.05). We conclude that EPR induced with a flush solution containing oxygen and glucose allowed satisfactory recovery of neurological function after a 3 h of CA, suggesting benefit from substrate delivery during induction or maintenance of a profound hypothermic CA.

Exsanguination cardiac arrest in rats treated by 60min, but not 75min, emergency preservation and delayed resuscitation is associated with intact outcome

Emergency preservation and resuscitation (EPR) is a new approach for resuscitation of exsanguination cardiac arrest (CA) victims to buy time for surgical hemostasis. EPR uses a cold aortic flush to induce deep hypothermic preservation, followed by resuscitation with cardiopulmonary bypass (CPB). We previously reported that 20 min of EPR was feasible with intact outcome. In this report, we tested the limits for EPR in rats. Adult male isoflurane-anesthetized rats were subjected to rapid hemorrhage (12.5 ml over 5 min), followed by esmolol/KCl-induced CA and 1 min of no-flow. EPR was then induced by perfusion with 270 ml of ice-cold Plasma-Lyte to decrease body temperature to 15 degrees C. After 60 min (n=7) or 75 min (n=7) of EPR, resuscitation was attempted with CPB over 60 min, blood transfusion, correction of acid-base balance and electrolyte disturbances, and mechanical ventilation for 2h. Survival, overall performance category (OPC: 1=normal, 5=death), neurological deficit score (NDS), and histological damage score (HDS) were assessed in survivors on day 3. While all rats after 60 min EPR survived, only two out of seven rats after 75 min EPR survived (p<0.05). All rats after 60 min EPR achieved OPC 1 and normal NDS by day 3. Survivors after 75 min EPR achieved best OPC 3 (p<0.05 vs. 60 min EPR). HDS of either brain or individual viscera was not statistically different after 60 versus 75 min EPR, except for kidneys (0+/-0 vs. 1.9+/-1.3, respectively; p<0.05), with a strong trend toward greater injury in all extracerebral organs in the 75-min EPR group (p<0.06). Histological findings were dominated by cardiac lesions observed in both groups and acute renal tubular and liver necrosis in the 75-min EPR group. In conclusion, we have shown that 60 min of EPR after exsanguination CA is associated with survival and favorable neurological outcome, while 75 min of EPR results in significant mortality and neurological damage in survivors. Surprisingly, extracerebral lesions predominated at 75-min EPR group. This model should serve as a screening model both for testing new pharmacological adjuncts to improve survival after exsanguination CA, and for elucidating the underlying mechanisms of ischemia/reperfusion injury.

Suspended animation for delayed resuscitation

'Suspended animation for delayed resuscitation' is a new concept for attempting resuscitation from cardiac arrest of patients who currently (totally or temporarily) cannot be resuscitated, such as traumatic exsanguination cardiac arrest. Suspended animation means preservation of the viability of brain and organism during cardiac arrest, until restoration of stable spontaneous circulation or prolonged artificial circulation is possible. Suspended animation for exsanguination cardiac arrest of trauma victims would have to be induced within the critical first 5 min after the start of cardiac arrest no-flow, to buy time for transport and resuscitative surgery (hemostasis) performed during no-flow. Cardiac arrest is then reversed with all-out resuscitation, usually requiring cardiopulmonary bypass. Suspended animation has been explored and documented as effective in dogs in terms of long-term survival without brain damage after very prolonged cardiac arrest. In the 1990s, the Pittsburgh group achieved survival without brain damage in dogs after cardiac arrest of up to 90 min no-flow at brain (tympanic) temperature of 10 degrees C, with functionally and histologically normal brains. These studies used emergency cardiopulmonary bypass with heat exchanger or a single hypothermic saline flush into the aorta, which proved superior to pharmacologic strategies. For the large number of normovolemic sudden cardiac death victims, which currently cannot be resuscitated, more research in large animals is needed.

Suspended animation can allow survival without brain damage after traumatic exsanguination cardiac arrest of 60 minutes in dogs

BACKGROUND

We have previously shown in dogs that exsanguination cardiac arrest of up to 120 minutes without trauma under profound hypothermia induced by aortic flush (suspended animation) can be survived without neurologic deficit. In the present study, the effects of major trauma (laparotomy, thoracotomy) are explored. This study is designed to better mimic the clinical scenario of an exsanguinating trauma victim, for whom suspended animation may buy time for resuscitative surgery and delayed resuscitation.

METHODS

Fourteen dogs were exsanguinated over 5 minutes to cardiac arrest. Flush of saline at 2 degrees C into the femoral artery was initiated at 2 minutes of cardiac arrest and continued until a tympanic temperature of 10 degrees C was achieved. The dogs were then randomized into a control group without trauma (n = 6) or a trauma group (n = 8) that underwent a laparotomy and isolation of the spleen before hemorrhage and then, at the start of cardiac arrest, spleen transection and left thoracotomy. During cardiac arrest, splenectomy was performed. After 60 minutes of no-flow cardiac arrest, reperfusion with cardiopulmonary bypass was followed by intensive care to 72 hours.

RESULTS

All 14 dogs survived to 72 hours with histologically normal brains. All control dogs were functionally neurologically intact. Four of eight trauma dogs were also functionally normal. Four had neurologic deficits, although three required prolonged mechanical ventilation because of airway edema and evidence of multiple organ failure. Blood loss from the chest and abdomen was variable and was associated with poor functional outcomes.

CONCLUSION

Rapid induction of profound hypothermic suspended animation (tympanic temperature, 10 degrees C) can enable survival without brain damage after exsanguination cardiac arrest of 60 minutes even in the presence of trauma, although prolonged intensive care may be required. This technique may allow survival of exsanguinated trauma victims, who now have almost no chance of survival.

[Therapeutic hypothermia after cardiac arrest]

The use of therapeutic hypothermia following different hypoxic-ischaemic insults has played an important role in various concepts of non-specific protection of cells for a long time. Although the use of deep therapeutic hypothermia after cardiac arrest in the last century did not lead to an improved outcome, recent data have demonstrated very positive effects of mild therapeutic hypothermia. The data from the European multicenter trial as well as those from Australia have clearly demonstrated a decrease in mortality and a better neurological outcome for patients being cooled to 32-34 degrees C for 12 or 24 h. In 2003, this led to the implementation of mild therapeutic hypothermia (32-34 degrees C) into the International Liaison Committee on Resuscitation (ILCOR) recommendations and guidelines for the treatment of unconscious patients after prehospital cardiac arrest. This article gives an overview on existing concepts and future perspectives of therapeutic mild hypothermia.

Lost in translation: taking neuroprotection from animal models to clinical trials

Caffeinol has been proposed as a neuroprotectant for human trials. This review covers a variety of animal models used and various attempts to take animal protocols to human trials. The accompanying paper discusses the rabbit model that was used to identify the efficacy of tissue plasminogen activator (tPA) treatment. To date, this is the only model that was able to achieve laboratory to clinical translational success. Use of caffeinol as a cytoprotective agent in rat models yielded exciting results, which led to clinical trials. However, caffeinol given with tPA in rabbits leads to increased hemorrhage. Caffeinol alone does not prove to be neuroprotective, as vasodilation by itself is not efficacious. However, vasodilation combined with thrombolysis (caffeinol with tPA) poses an increased risk of hemorrhage. For a more translational approach to study neuroprotection and neuroprotective agents in human trials, it is necessary to demonstrate the efficacy of the procedure and purported agents in several animal models.

Suspended animation for resuscitation from exsanguinating hemorrhage

In dogs, isotonic saline at 0-4 degrees C, flushed into the aorta at a rate of 1-2 L/min, with drainage of the vena cava, can achieve deep to profound hypothermia of vital organs at a cooling rate of up to 3 degrees C per minute. This achieves preservation of viability of the organism during predictable durations of no flow: cardiac arrest of 15-20 mins at Tty of 30-35 degrees C, cardiac arrest of 30 mins at Tty of 25 degrees C, cardiac arrest of 60 mins at Tty of 15 degrees C, and cardiac arrest of 90 mins at Tty of 10 degrees C. So far, pharmacologic approaches have not resulted in any breakthrough effect on outcome above that achieved with hypothermia, except perhaps the antioxidant tempol. Additional studies of novel drugs and, perhaps, combination therapies remain warranted. The optimal fluids to have in the circulation during circulatory arrest and reperfusions need to be determined. As laboratory studies to optimize suspended animation proceed, clinical trials should be initiated. In addition, devices should be developed to facilitate induction of suspended animation, eventually in the field.

Survival without brain damage after clinical death of 60-120 mins in dogs using suspended animation by profound hypothermia

OBJECTIVES

This study explored the limits of good outcome of brain and organism achievable after cardiac arrest (no blood flow) of 60-120 mins, with preservation (suspended animation) induced immediately after the start of exsanguination cardiac arrest.

DESIGN

Prospective experimental comparison of three arrest times, without randomization.

SETTING

University research laboratory.

SUBJECTS

Twenty-seven custom-bred hunting dogs (17-25 kg).

INTERVENTIONS

Dogs were exsanguinated over 5 mins to cardiac arrest no-flow of 60 mins, 90 mins, or 120 mins. At 2 mins of cardiac arrest, the dogs received, via a balloon-tipped catheter, an aortic flush of isotonic saline at 2 degrees C (at a rate of 1 L/min), until tympanic temperature reached 20 degrees C (for 60 mins of cardiac arrest), 15 degrees C (for 60 mins of cardiac arrest), or 10 degrees C (for 60, 90, or 120 mins of cardiac arrest). Resuscitation was by closed-chest cardiopulmonary bypass, postcardiac arrest mild hypothermia (tympanic temperature 34 degrees C) to 12 hrs, controlled ventilation to 20 hrs, and intensive care to 72 hrs.

MEASUREMENTS AND MAIN RESULTS

We assessed overall performance categories (OPC 1, normal; 2, moderate disability; 3, severe disability; 4, coma; 5, death), neurologic deficit scores (NDS 0-10%, normal; 100%, brain death), regional and total brain histologic damage scores at 72 hrs (total HDS >0-40, mild; 40-100, moderate; >100, severe damage), and morphologic damage of extracerebral organs. For 60 mins of cardiac arrest (n = 14), tympanic temperature 20 degrees C (n = 6) was achieved after flush of 3 mins and resulted in two dogs with OPC 1 and four dogs with OPC 2: median NDS, 13% (range 0-27%); and median total HDS, 28 (range, 4-36). Tympanic temperature of 15 degrees C (n = 5) was achieved after flush of 7 mins and resulted in all five dogs with OPC 1, NDS 0% (0-3%), and HDS 8 (0-48). Tympanic temperature 10 degrees C (n = 3) was achieved after flush of 11 mins and resulted in all three dogs with OPC 1, NDS 0%, and HDS 16 (2-18). For 90 mins of cardiac arrest (n = 6), tympanic temperature 10 degrees C was achieved after flush of 15 mins and resulted in all six dogs with OPC 1, NDS 0%, and HDS 8 (0-37). For 120 mins of cardiac arrest (n = 7), three dogs had to be excluded. In the four dogs within protocol, tympanic temperature 10 degrees C was achieved after flush of 15 mins. This resulted in one dog with OPC 1, NDS 0%, and total HDS 14; one with OPC 1, NDS 6%, and total HDS 20; one with OPC 2, NDS 13%, and total HDS 10; and one with OPC 3, NDS 39%, and total HDS 22.

CONCLUSIONS

In a systematic series of studies in dogs, the rapid induction of profound cerebral hypothermia (tympanic temperature 10 degrees C) by aortic flush of cold saline immediately after the start of exsanguination cardiac arrest-which rarely can be resuscitated effectively with current methods-can achieve survival without functional or histologic brain damage, after cardiac arrest no-flow of 60 or 90 mins and possibly 120 mins. The use of additional preservation strategies should be pursued in the 120-min arrest model.

Cerebral resuscitation potentials for cardiac arrest

Permanent brain damage after cardiac arrest and resuscitation is determined by many factors, predominantly arrest (no-flow) time, cardiopulmonary resuscitation (low-flow) time, and temperature. Research since around 1970 into cardiopulmonary-cerebral resuscitation has attempted to mitigate the postischemic-anoxic encephalopathy. These efforts' results have recently shown outcome benefits as documented in clinically relevant outcome models in dogs and in clinical trials. Pharmacologic strategies have so far yielded relatively disappointing results. In a recent exploration of 14 drugs in dogs, only the antioxidant tempol administered at the start of prolonged cardiac arrest improved functional outcome in dogs. Cerebral blood flow promotion by hypertensive reperfusion and hemodilution has resulted in improved outcome in dogs, and brief hypertension after restoration of spontaneous circulation is associated with improved outcome in patients. Postarrest hypercoagulability of blood seems to yield to therapeutic thrombolysis, which is associated with improved cerebral outcome in animals and patients. In a clinically relevant dog outcome model, mild postarrest cerebral hypothermia (34 degrees C), initiated with reperfusion and continued for 12 hrs, combined with cerebral blood-flow promotion increased from 5 to >10 mins the previously longest normothermic no-flow time that could be reversed to complete cerebral recovery. Mild hypothermia by surface cooling after prolonged cardiac arrest in patients has been found effective in recent clinical studies in Australia and Europe. Preliminary data on the recent randomized study in Europe have been reported. For presently unresuscitable cardiac arrests, research since the 1980s in dog outcome models of prolonged exsanguination cardiac arrest has culminated in brain and organism preservation during cardiac arrest (no-flow) durations of up to 90 mins, perhaps 120 mins, at a tympanic temperature of 10 degrees C and complete recovery of function and normal histology. This "suspended animation for delayed resuscitation" strategy includes use of an aortic flush of cold saline (or preservation solution) within the first 5 mins of no flow. This strategy should also be explored for the larger number of patients with unresuscitable out-of-hospital cardiac arrests. Suspended animation for prolonged preservation of viability could buy time for transport and repair during hypothermic no flow followed by resuscitation, or it could serve as a bridge to prolonged cardiopulmonary bypass.

Antioxidant Tempol enhances hypothermic cerebral preservation during prolonged cardiac arrest in dogs

The authors are systematically exploring pharmacologic preservation for temporarily unresuscitable exsanguination cardiac arrest in dogs. They hypothesized that the antioxidant Tempol improves cerebral outcome when added to aortic saline flush at the start of cardiac arrest. In study A, no drug (n = 8), Tempol 150 mg/kg (n = 4), or Tempol 300 mg/kg (n = 4) was added to 25 mL/kg saline flush at 24 degrees C (achieving mild cerebral hypothermia) at the start of 20-minute cardiac arrest. In study B, no drug (n = 8) or Tempol 300 mg/kg (n = 7) was added to 50 mL/kg saline flush at 2 degrees C (achieving moderate cerebral hypothermia) at the start of 40-minute cardiac arrest. Cardiac arrest was reversed with cardiopulmonary bypass. Mild hypothermia lasted for 12 hours, controlled ventilation was sustained to 24 hours, and intensive care was provided for up to 72 hours. In study A, overall performance category 1 or 2 (good outcome) was achieved in all eight dogs treated with Tempol compared with three of eight dogs in the control group ( P = 0.03). In study B, good outcome was achieved in all seven dogs treated with Tempol versus only two of 8 dogs in the control group ( P = 0.007). In both studies, neurologic deficit scores were significantly better in the Tempol group, but not total histologic damage scores. At 72 hours, electron paramagnetic resonance spectroscopy of Tempol revealed direct evidence for its presence in the brain. Single- and double-strand DNA damage, nitrotyrosine immunostaining, total antioxidant reserve, and ascorbate acid levels were similar between groups, and thiol levels were decreased after Tempol in study B. The authors conclude that when added to aortic saline flush at the start of prolonged cardiac arrest, the antioxidant Tempol can enhance mild or moderate hypothermic cerebral preservation in terms of improved functional outcome. The mechanisms involved in this beneficial effect need further clarification.

Fructose-1,6-bisphosphate and MK-801 by aortic arch flush for cerebral preservation during exsanguination cardiac arrest of 20 min in dogs. An exploratory study

In our exsanguination cardiac arrest (CA) outcome model in dogs we are systematically exploring suspended animation (SA), i.e. preservation of brain and heart immediately after the onset of CA to enable transport and resuscitative surgery during CA, followed by delayed resuscitation. We have shown in dogs that inducing moderate cerebral hypothermia with an aortic arch flush of 500 ml normal saline solution at 4 degrees C, at start of CA 20 min no-flow, leads to normal functional outcome. We hypothesized that, using the same model, but with the saline flush at 24 degrees C inducing minimal cerebral hypothermia (which would be more readily available in the field), adding either fructose-1,6-bisphosphate (FBP, a more efficient energy substrate) or MK-801 (an N-methyl-D-aspartate (NMDA) receptor blocker) would also achieve normal functional outcome. Dogs (range 19-30 kg) were exsanguinated over 5 min to CA of 20 min no-flow, and resuscitated by closed-chest cardiopulmonary bypass (CPB). They received assisted circulation to 2 h, mild systemic hypothermia (34 degrees C) post-CA to 12 h, controlled ventilation to 20 h, and intensive care to 72 h. At CA 2 min, the dogs received an aortic arch flush of 500 ml saline at 24 degrees C by a balloon-tipped catheter, inserted through the femoral artery (control group, n=6). In the FBP group (n=5), FBP (total 1440 or 4090 mg/kg) was given by flush and with reperfusion. In the MK-801 group (n=5), MK-801 (2, 4, or 8 mg/kg) was given by flush and with reperfusion. Outcome was assessed in terms of overall performance categories (OPC 1, normal; 2, moderate disability; 3, severe disability; 4, coma; 5, brain death or death), neurologic deficit scores (NDS 0-10%, normal; 100%, brain death), and brain histologic damage scores (HDS, total HDS 0, no damage; >100, extensive damage; 1064, maximal damage). In the control group, one dog achieved OPC 2, one OPC 3, and four OPC 4; in the FBP group, two dogs achieved OPC 3, and three OPC 4; in the MK-801 group, two dogs achieved OPC 3, and three OPC 4 (P=1.0). Median NDS were 62% (range 8-67) in the control group; 55% (range 34-66) in the FBP group; and 50% (range 26-59) in the MK-801 group (P=0.2). Median total HDS were 130 (range 56-140) in the control group; 96 (range 64-104) in the FBP group; and 80 (range 34-122) in the MK-801 group (P=0.2). There was no difference in regional HDS between groups. We conclude that neither FBP nor MK-801 by aortic arch flush at the start of CA, plus an additional i.v. infusion of the same drug during reperfusion, can provide cerebral preservation during CA 20 min no-flow. Other drugs and drug-combinations should be tested with this model in search for a breakthrough effect.