Therapeutic hypothermia after cardiac arrest

Back from Irreversibility: Extracorporeal Life Support for Prolonged Cardiac Arrest

BACKGROUND

The survival of patients after prolonged cardiac arrest is still inadequate. Extracorporeal life support (ECLS) represents an alternative therapeutic method for patients who do not respond to conventional cardiopulmonary cerebral resuscitation. This technology is used to support the circulation of a patient with severe cardiac failure.

METHODS

Between June 1997 and January 2003, 40 ECLS procedures were performed in patients who presented with refractory cardiac arrest. During external cardiac massage, the patient was connected to an extracorporeal circuit by the insertion of an arterial and venous cannula through the femoral vessels. The extracorporeal circuit included a centrifugal pump and an oxygenator. Mean age was 42 +/- 15 years; the average time of external cardiac massage was 105 +/- 44 minutes.

RESULTS

Once the circulation was restored, 22 patients were disconnected from the extracorporeal circulation because of brain death or multiorgan failure; after 24 hours, among the 18 survivors, 6 were weaned off the pump, 9 were bridged to a ventricular assist device, and 2 patients were directly bridged to cardiac transplantation. Eight patients are alive and without any sequelae at 18 month's follow-up.

CONCLUSIONS

In prolonged cardiac arrest with failing conventional measures, rescue by extracorporeal support provides an ultimate therapeutic option with a good outcome in survivors. Our results encourage the wider application of ECLS for refractory cardiocirculatory arrest in selected patients. The high rate of neurologic death needs further improvements in the early phase of resuscitation maneuvers.

Randomized trial of systemic hypothermia selectively protects the cortex on MRI in term hypoxic-ischemic encephalopathy

Twenty-six infants with hypoxic-ischemic encephalopathy (HIE) were randomized to normothermia or to systemic hypothermia. The hypothermia group had less cortical gray matter signal abnormality on magnetic resonance imaging (MRI) (1/12 vs 7/14 infants in the normothermic group; P = .036), which may indicate differing regional benefit from systemic hypothermia.

Mild hypothermia during prolonged cardiopulmonary cerebral resuscitation increases conscious survival in dogs

OBJECTIVE

Therapeutic hypothermia during cardiac arrest and after restoration of spontaneous circulation enables intact survival after prolonged cardiopulmonary cerebral resuscitation (CPCR). The effect of cooling during CPCR is not known. We hypothesized that mild to moderate hypothermia during CPCR would increase the rate of neurologically intact survival after prolonged cardiac arrest in dogs.

DESIGN

Randomized, controlled study using a clinically relevant cardiac arrest outcome model in dogs.

SETTING

University research laboratory.

SUBJECTS

Twenty-seven custom-bred hunting dogs (19-29 kg; three were excluded from outcome evaluation).

INTERVENTIONS

Dogs were subjected to cardiac arrest no-flow of 3 mins, followed by 7 mins of basic life support and 10 mins of simulated unsuccessful advanced life support attempts. Another 20 mins of advanced life support continued with four treatments: In control group 1 (n = 7), CPCR was with normothermia; in group 2 (n = 6, 1 of 7 excluded), with moderate hypothermia via venovenous extracorporeal shunt cooling to tympanic temperature 27 degrees C; in group 3 (n = 6, 2 of 8 excluded), the same as group 2 but with mild hypothermia, that is, tympanic temperature 34 degrees C; and in group 4 (n = 5), with normothermic venovenous shunt. After 40 mins of ventricular fibrillation, reperfusion was with cardiopulmonary bypass for 4 hrs, including defibrillation to achieve spontaneous circulation. All dogs were maintained at mild hypothermia (tympanic temperature 34 degrees C) to 12 hrs. Intensive care was to 96 hrs.

MEASUREMENTS AND MAIN RESULTS

Overall performance categories and neurologic deficit scores were assessed from 24 to 96 hrs. Regional and total brain histologic damage scores and extracerebral organ damage were assessed at 96 hrs. In normothermic groups 1 and 4, all 12 dogs achieved spontaneous circulation but remained comatose and (except one) died within 58 hrs with multiple organ failure. In hypothermia groups 2 and 3, all 12 dogs survived to 96 hrs without gross extracerebral organ damage (p < .0001). In group 2, all but one dog achieved overall performance category 1 (normal); four of six dogs had no neurologic deficit and normal brain histology. In group 3, all dogs achieved good functional outcome with normal or near-normal brain histology. Myocardial damage scores were worse in the normothermic groups compared with both hypothermic groups (p < .01).

CONCLUSION

Mild or moderate hypothermia during prolonged CPCR in dogs preserves viability of extracerebral organs and improves outcome.

Hypoxic-ischemic brain injury in the term infant-current concepts

An enhanced understanding of the cellular characteristics contributing to ongoing brain injury following intrapartum hypoxia-ischemia has resulted in the implementation of targeted neuroprotective strategies in the newborn period. This review briefly covers the pathogenesis of hypoxic-ischemic injury with an emphasis on reperfusion injury; the role of magnetic resonance imaging in the detection of such injury, and focuses on potential strategies both supportive and neuroprotective to prevent ongoing injury with a specific emphasis on modest hypothermia.

Induction of therapeutic hypothermia after cardiac arrest in prehospital patients using ice-cold Ringer’s solution: a pilot study

The cooling and haemodynamic effects of prehospital infusion of ice-cold Ringer's solution were studied in 13 adult patients after successful resuscitation from non-traumatic cardiac arrest. After haemodynamics stabilisation, 30 ml/kg of Ringer's solution was infused at a rate of 100ml/min into the antecubital vein. Arterial blood pressure and blood gases, pulse rate, end-tidal CO(2) and oesophageal temperature were monitored closely. The mean core temperature decreased from 35.8 +/- 0.9 degrees C at the start of infusion to 34.0 +/- 1.2 degrees C on arrival at hospital (P < 0.0001). No serious adverse haemodynamic effects occurred. It is concluded that the induction of therapeutic hypothermia using this technique in the prehospital setting is feasible.

Moderate hypothermia for 359 operations to clip cerebral aneurysms

BACKGROUND

Experimental data have suggested that hypothermia (32-34 degrees C) may improve outcome after cerebral ischaemia, but its efficacy has not yet been established conclusively in humans. In this study we examined the feasibility and safety of deliberate moderate perioperative hypothermia during operations for subarachnoid aneurysms.

METHODS

A total of 359 operations for intracranial cerebral aneurysms were included in this prospective study. By using cold intravenous infusions (4 degrees C) and convective cooling our aim was to reduce the patient's core temperature to more than 34 degrees C within 1 h before operation. The protocol assessed postoperative complications such as infections, prolonged mechanical ventilation, pulmonary complications and coagulopathies.

RESULTS

During surgery, the body temperature was reduced to a mean of 32.5 (SD 0.4) degrees C. Cooling was accomplished at a rate of 4.0 (SD 0.4) degrees C h(-1). All patients were normothermic at 5 (sd 2) h postoperatively. Peri/postoperative complications included circulatory instability (n=36, 10%), arrhythmias (n=17, 5%) coagulation abnormalities and blood transfusion (n=169, 47%), infections (n=29, 8%) and pulmonary complications (infiltrate or oedema while on ventilatory support) (n=97, 27%). Eighteen patients died within 30 days (5%). There was no significant correlation between the extent of hypothermia and any of the complications. However, there was a strong correlation between the occurrence of complications and the severity of the underlying neurological disease as assessed by the Hunt and Hess score.

CONCLUSION

Moderate hypothermia accomplished within 1 h of induction of anaesthesia and maintained during surgery for subarachnoid aneurysms appears to be a safe method as far as the risks of peri/postoperative complications such as circulatory instability, coagulation abnormalities and infections are concerned.

Safety of deliberate intraoperative and postoperative hypothermia for patients undergoing coronary artery surgery: A randomized trial

BACKGROUND

Hypothermia in the perioperative period is associated with adverse effects, particularly bleeding. Before termination of cardiopulmonary bypass, rewarming times and perfusion temperatures are often increased to avoid post-cardiopulmonary bypass hypothermia and the presumed complications. This practice may, however, also have adverse effects, particularly cerebral hyperthermia. We present safety outcomes from a trial in which patients undergoing coronary artery surgery were randomly assigned to normothermia or hypothermia for the entire surgical procedure.

METHODS

Consenting patients over the age of 60 years presenting for a first, elective coronary artery surgery with cardiopulmonary bypass were randomly assigned to having their nasopharyngeal temperature maintained at either 37 degrees C (group N; 73 patients) or 34 degrees C (group H; 71 patients) throughout the intraoperative period, with no rewarming before arrival in the intensive care unit. All received tranexamic acid.

RESULTS

There was no clinically important difference in intraoperative blood product or inotrope use. Temperatures on arrival in the intensive care unit were 36.7 degrees C +/- 0.38 degrees C and 34.3 degrees C +/- 0.38 degrees C in groups N and H, respectively. Blood loss during the first 12 postoperative hours was 596 +/- 356 mL in group N and 666 +/- 405 mL in group H (mean difference +/- 95% confidence interval, 70 +/- 126 mL; P =.28). There was no significant difference in blood product utilization, intubation time, time in the hospital, myocardial infarction, or mortality. The mean time in the intensive care unit was 8.4 hours less in the hypothermic group (P =.02).

CONCLUSIONS

Our data support the safety of perioperative mild hypothermia in patients undergoing elective nonreoperative coronary artery surgery with cardiopulmonary bypass. These findings suggest that complete rewarming after hypothermic cardiopulmonary bypass is not necessary in all cases.

Neurotensin-induced hypothermia improves neurologic outcome after hypoxic-ischemia

OBJECTIVE

External cooling is commonly used to force induction of mild hypothermia but requires equipment, has a slow onset of action, and must be prolonged to provide permanent neurologic benefits after hypoxic-ischemia. It is unknown whether the method for inducing mild hypothermia affects neurologic outcome after near-drowning. The objective of the study was to induce mild hypothermia with neurotensin analog NT77 or external cooling in a rat model of near-drowning. We hypothesize that NT77 would be more effective for improving neurologic outcome than external cooling of the same duration.

DESIGN

Rats were randomized to a normothermic control, neurotensin-induced hypothermia, brief external cooling, or prolonged external cooling group after asphyxial cardiac arrest.

SETTING

Laboratory investigation.

SUBJECTS

Forty-eight rats.

INTERVENTIONS

Mild hypothermia was induced by external cooling for 4 hrs (brief external cooling) or 24 hrs (prolonged external cooling) or by neurotensin-induced hypothermia administration 30 mins after asphyxial cardiac arrest in rats.

MEASUREMENTS

Outcome was assessed by a neurologic deficit score, the Morris water maze, and CA1 hippocampus histology 15 days after resuscitation.

MAIN RESULTS

Neurologic deficit score at 72 hrs after asphyxial cardiac arrest was lower with neurotensin-induced hypothermia (score, 0) and prolonged external cooling (score, 0) vs. normothermic control (score, 20) and brief external cooling (score, 18; p <.05). Latency time in the Morris water maze 15 days after asphyxial cardiac arrest was decreased with neurotensin-induced hypothermia (14+/-11 secs) and prolonged external cooling (18+/-9 secs) vs. normothermic control (74+/-17 secs) and brief external cooling (78+/-18 secs, p <.05). There was less ischemic neuronal damage with neurotensin-induced hypothermia (28+/-24%) and prolonged external cooling (21+/-14%) vs. normothermic control (61+/-32%) and brief external cooling (51+/-32%).

CONCLUSIONS

Neurotensin-induced hypothermia improved neurologic outcome after asphyxial cardiac arrest in rats vs. brief external cooling but was comparable to prolonged external cooling.

The problems with the validity of the diagnosis of brain death

The diagnosis of brain death as 'death' and organ transplantation have been closely historically linked since the mid twentieth century. It will be argued in this article that the development of a neurological definition of death was introduced to justify the removal of fresh viable organs for transplantation. Brain death cannot be diagnosed reliably using 'established practices'. Improved understanding of the pathophysiology of raised intracranial pressure has challenged our understanding of brain death. We need to move forward in our conceptualization of phenomenon of profound coma associated with massive brain damage. If examination for 'brain death' is to be carried out at all, there needs to be an examination and re-evaluation of practices and protocols.

Therapeutic hypothermia

Hypothermia is common during anaesthesia and surgery owing to anaesthetic-induced inhibition of thermoregulatory control. Perioperative hypothermia is associated with numerous complications. However, for certain patient populations, and under specific clinical conditions, hypothermia can provide substantial benefits. Lowering core temperature to 32-34 degrees C may reduce cell injury by suppressing excitotoxins and oxygen radicals, stabilizing cell membranes, and reducing the number of abnormal electrical depolarizations. Evidence from animal studies indicates that even mild hypothermia provides substantial protection against cerebral ischaemia and myocardial infarction. Mild hypothermia has been shown to improve outcome after cardiac arrest in humans. Randomized trials are in progress to evaluate the potential benefits of mild hypothermia during aneurysm clipping and after stroke or acute myocardial infraction. However, as hypothermia can cause unwanted side-effects, further research is needed to better quantify the risks and benefits of therapeutic hypothermia.

Transplantation of lungs from non-heart-beating donors after functional assessment ex vivo

BACKGROUND

If lungs from patients dying of heart attacks are to serve as donor organs in a safe way, their function should be properly assessed before transplantation. The aim of this study was to investigate donor lung function evaluation in a realistic large animal model.

METHODS

Twelve 60-kg pigs were used. Five minutes after ventricular fibrillation was induced, cardiopulmonary resuscitation was initiated and maintained for 20 minutes. After a 10-min hands-off period, heparin was administered through a central venous catheter followed by 20 chest compressions. Intrapleural cooling was initiated after 65 minutes of warm ischemia. Cooling proceeded for 6 hours within the cadaver, after which lung function was assessed ex vivo. Recipient pigs underwent left lung transplantation followed by right pneumonectomy, thus making these animals 100% dependent for their survival on the function of the donor lungs.

RESULTS

The assessment showed that all lungs had adequate function to serve as donor lungs. All recipient animals were in good condition during the 24-hour observation period after the operation. The blood gas function did not differ significantly from that in the healthy donor animals before induction of ventricular fibrillation; pulmonary vascular resistance was within normal range.

CONCLUSIONS

Lungs from non-heart-beating donors topically cooled in situ for 6 hours after 65 minutes of warm ischemia were assessed ex vivo and found to have normal function. They were then transplanted and retained normal function during a 24-hour observation period.

Therapeutic hypothermia for acute stroke

Experimental evidence and clinical experience show that hypothermia protects the brain from damage during ischaemia. There is a growing hope that the prevention of fever in stroke will improve outcome and that hypothermia may be a therapeutic option for the treatment of stroke. Body temperature is directly related to stroke severity and outcome, and fever after stroke is associated with substantial increases in morbidity and mortality. Normalisation of temperature in acute stroke by antipyretics is generally recommended, although there is no direct evidence to support this treatment. Despite its obvious therapeutic potential, hypothermia as a form of neuroprotection for stroke has been investigated in only a few very small studies. Therapeutic hypothermia is feasible in acute stroke but owing to serious side-effects--such as hypotension, cardiac arrhythmia, and pneumonia--it is still thought of as experimental, and evidence of efficacy from clinical trials is needed.

Hypothermia after cardiac arrest: a treatment that works

PURPOSE OF REVIEW

Sudden death from cardiac arrest is a major health problem that still receives too little publicity. Current therapy after cardiac arrest concentrates on resuscitation efforts because, until now, no specific therapy for brain protection after restoration of spontaneous circulation was available. Therapeutic mild or moderate resuscitative hypothermia is a novel therapy with multifaceted chemical and physical effects by preventing or mitigating the derangements seen in the postresuscitation syndrome.

RECENT FINDINGS AND SUMMARY

In 2002, two prospective, randomized studies reported improved outcomes when deliberate hypothermia was induced in comatose survivors after resuscitation from cardiac arrest. However, several issues with regard to resuscitative cooling are still unanswered and should be studied further. These include the optimal timing to initiate cooling, the optimal cooling period, the optimal temperature level, and rewarming strategy. Even important questions, such as which cooling technique will be available in the near future that would combine ease of use with high efficacy, are not answered yet.

A specific taurine recognition site in the rabbit brain is responsible for taurine effects on thermoregulation

(1) Taurine and GABA are recognized as endogenous cryogens. In a previous study, some structural analogues of taurine, namely 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine 1,1-dioxide (TAG), 2-aminoethylarsonic (AEA), 2-hydroxyethanesulfonic (ISE) and (+/-)cis-2-aminocyclohexane sulfonic acids (CAHS) have been shown to displace [(3)H]taurine binding from rabbit brain synaptic membrane preparations, without interacting either with GABA-ergic systems, nor with taurine uptake mechanism, thus behaving like direct taurinergic agents. (2) To answer the question whether the role of taurine as an endogenous cryogen depends on the activation of GABA receptors or that of specific taurine receptor(s), taurine or the above structural analogues were injected intracerebroventricularly in conscious, restrained rabbits singularly or in combination and their effects on rectal (RT)- and ear-skin temperature and gross motor behavior (GMB) were monitored. (3) Taurine (1.2 x 10(-6)-4.8 x 10(-5) mol) induced a dose-related hypothermia, vasodilation at ear vascular bed and inhibition of GMB. CAHS, at the highest dose tested (4.8 x 10(-5) mol) induced a taurine-like effect either on RT or GMB. On the contrary ISE, injected at the same doses of taurine, induced a dose-related hyperthermia, vasoconstriction and excitation of GMB. AEA and TAG caused a dose-related hyperthermia, but at doses higher than 1.2 x 10(-7) mol caused death within 24 h after treatment. (4) CAHS (4.8 x 10(-5) mol) antagonized the hyperthermic effect induced by TAG (1.2 x 10(-6) mol), AEA (1.2 x 10(-8) mol) or ISE (4.8 x 10(-5) mol). (5) In conclusion, these findings may indicate the existence of a recognition site specific for taurine, responsible for its effects on thermoregulation.

Head cooling with mild systemic hypothermia in anesthetized piglets is neuroprotective

Hypothermia is potentially therapeutic in the management of neonatal hypoxic-ischemic brain injury. However, not all studies have shown a neuroprotective effect. It is suggested that the stress of unsedated hypothermia may interfere with neuroprotection. We propose that selective head cooling (SHC) combined with mild total-body hypothermia during anesthesia enhances local neuroprotection while minimizing the occurrence of systemic side effects and stress associated with unsedated whole-body cooling. Our objective was to determine whether SHC combined with mild total-body hypothermia while anesthetized for a period of 24 hours reduces cerebral damage in our piglet survival model of global hypoxia-ischemia. Eighteen anesthetized piglets received a 45-minute global hypoxic-ischemic insult. The pigs were randomized either to remain normothermic or to receive SHC. We found that the severity of the hypoxic-ischemic insult was similar in the SHC versus the normothermic group, and that the mean neurology scores at 30 and 48 hours and neuropathology scores were significantly better in the SHC group versus the normothermic group. We conclude that selective head cooling combined with mild systemic hypothermia and anesthesia is neuroprotective when started immediately after the insult in our piglet model of hypoxic-ischemic encephalopathy.

Drowning and near-drowning

Water immersion is a frequent cause of accidental death and hospital admission. This article outlines the pathogenesis and principles of treatment. Drowning is defined as death by asphyxia due to submersion in a liquid medium. Near-drowning is defined as immediate survival after asphyxia due to submersion.

Evaluation of LUCAS, a new device for automatic mechanical compression and active decompression resuscitation

LUCAS is a new gas-driven CPR device providing automatic chest compression and active decompression. In an artificial thorax model, superior pressure and flow were obtained with LUCAS compared with manual CPR. In a randomized study on pigs with induced ventricular fibrillation significantly higher cardiac output, carotid artery blood flow, end-tidal CO(2), intrathoracic decompression-phase aortic- and coronary perfusion pressures were obtained with LUCAS-CPR (83% ROSC) compared to manual CPR (0% ROSC). In normothermic fibrillating pigs, the ROSC rate was 100% after 15 min and 38% after 60 min of LUCAS-CPR (no drug treatment). The ROSC rate increased to 75% if surface cooling to 34 degrees C was applied during the first 30 min of the 1-h resuscitation period. Experience with the first 20 patients has shown that LUCAS is light (6.5 kg), easy to handle, quick to apply (10-20 s), maintains a correct position, and works optimally during transport both on stretchers and in ambulances. In one hospital patient with a witnessed asystole where manual CPR failed, LUCAS-CPR achieved ROSC within 3 min. One year later the patient's mental capacity was fully intact. To conclude, LUCAS-CPR gives significantly better circulation during ventricular fibrillation than manual CPR.

Temperature-dependent splicing of beta-globin pre-mRNA

A T-->G mutation at nucleotide 705 of human beta-globin intron 2 creates an aberrant 5' splice site and activates a cryptic 3' splice site upstream. In consequence, the pre-mRNA is spliced via aberrant splice sites, despite the presence of the still functional correct sites. Surprisingly, when IVS2-705 HeLa or K562 cells were cultured at temperatures below 30 degrees C, aberrant splicing was inhibited and correct splicing was restored. Similar temperature effects were seen for another beta-globin pre-mRNA, IVS2-745, and in a construct in which a beta-globin intron was inserted into a coding sequence of EGFP. Temperature-induced alternative splicing was affected by the nature of the internal aberrant splice sites flanking the correct sites and by exonic sequences. The results indicate that in the context of thalassemic splicing mutations and possibly in other alternatively spliced pre-mRNAs, temperature is one of the parameters that affect splice site selection.

Veno-venous extracorporeal blood shunt cooling to induce mild hypothermia in dog experiments and review of cooling methods

Mild hypothermia (33-36 degrees C) might be beneficial when induced during or after insults to the brain (cardiac arrest, brain trauma, stroke), spinal cord (trauma), heart (acute myocardial infarction), or viscera (hemorrhagic shock). Reaching the target temperature rapidly in patients inside and outside hospitals remains a challenge. This study was to test the feasibility of veno-venous extracorporeal blood cooling for the rapid induction of mild hypothermia in dogs, using a simple pumping-cooling device. Ten custom-bred hunting dogs (21-28 kg) were lightly anesthetized and mechanically ventilated. In five dogs, two catheters were inserted through femoral veins, one peripheral and the other into the inferior vena cava. The catheters were connected via a coiled plastic tube as heat exchanger (15 m long, 3 mm inside diameter, 120 ml priming volume), which was immersed in an ice-water bath. A small roller-pump produced a veno-venous flow of 200 ml/min (about 10% of cardiac output). In five additional dogs (control group), a clinically practiced external cooling method was employed, using alcohol over the skin of the trunk and fanning plus ice-bags. During spontaneous normotension, veno-venous cooling delivered blood into the vena cava at 6.2 degrees C standard deviation (SD 1.4) and decreased tympanic membrane (Tty) temperature from 37.5 to 34.0 degrees C at 5.2 min (SD 0.7), and to 32.0 degrees C at 7.9 min (SD 1.3). Skin surface cooling decreased tympanic temperature from 37.5 to 34.0 degrees C at 19.9 min (SD 3.7), and to 32.0 degrees C at 29.9 (SD 5.1) (P=0.001). Heart rates at Tty 34 and 32 degrees C were significantly lower than at baseline in both groups, but within physiological range, without difference between groups. There were no arrhythmias. We conclude that in large dogs the induction of mild systemic hypothermia with extracorporeal veno-venous blood shunt cooling is simple and four times more rapid than skin surface cooling.

Termination of resuscitation: the art of clinical decision making

Despite all of the progress in reanimating patients in cardiac arrest over the last half century, resuscitation attempts usually fail to restore spontaneous circulation. Thus, the most common of all resuscitation decisions after initiation remains the decision to stop. An entire library of research and guidelines for terminating resuscitative efforts has been developed in the past decade. However, this most central decision is often left open to chance, provider preference, family wishes, futility judgments, and resource concerns-a host of subjective considerations at the bedside and beyond. This article sheds light on these considerations, acknowledging the pivotal role that resuscitation science and guidelines can play in the multifactorial decision to discontinue resuscitative efforts.

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.