Effects of intra-aortic balloon occlusion on hemodynamics during, and survival after cardiopulmonary resuscitation in dogs

OBJECTIVE: To evaluate the effect of balloon occlusion of the proximal descending aorta during cardiopulmonary resuscitation (CPR) on hemodynamics, restoration of spontaneous circulation, and 24-hr survival. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental laboratory in a university hospital. SUBJECTS: Eighteen anesthetized dogs. INTERVENTIONS; Catheters were placed for hemodynamic and blood gas monitoring. An aortic balloon catheter was placed with its tip just distal to the left subclavian artery. After 10 mins of ventricular fibrillation without CPR, 3 mins of Basic Life Support (chest compressions and ventilation with 100% oxygen) was followed by up to 30 mins of Advanced Cardiac Life Support with canine drug dosages. In the treatment group (n = 8), the intra-aortic balloon was inflated when Advanced Cardiac Life Support started and not deflated until shortly after restoration of spontaneous circulation. The control animals (n = 10) were treated with an identical resuscitation but without intra-aortic balloon occlusion. MEASUREMENTS AND MAIN RESULTS: In the treatment group, coronary perfusion pressure was greater during Advanced Cardiac Life Support (p = .026). Restoration of spontaneous circulation was more frequent (7/8 dogs) as compared with the control group (3/10 dogs) (p = .025). There was a trend toward greater 24-hr survival in the treatment group (5/8 dogs) than in the control group (3/10 dogs). CONCLUSIONS: Balloon occlusion of the proximal descending aorta during experimental CPR improves restoration of spontaneous circulation. Further laboratory and human studies are needed to determine the clinical efficacy of this technique.     

Interaction of the Na(+)-Ca2+ exchanger with small molecules on cell Ca2+ signaling

BACKGROUND: Evaluation of outcome after CPR in severe hypothermic patients. DESIGN: Perspective study from October 1995 to April 1996. SETTING: First aid team of Italian Red Cross, Busto Arsizio (Varese), Italy. METHODS: A population of 22 patients in cardiac arrest in which CPR was performed immediately after rescue team's arrival is studied. ECG, core temperature, SpO2 and MAP were monitored whereas vital parameters were present during Basic Life Support. Outcome after CPR was evaluated with GOS scale. RESULTS: It has been observed that severe hypothermia and time of cardiac arrest impact on the clinical outcome after CPR. The high mortality rate after CPR with BLS standard is worsened by a core temperature < or = 33 degrees C. CONCLUSIONS: Severe hypothermia seems to have a dangerous effect upon outcome after cardiopulmonary resuscitation; heating systems for body temperature could prevent this situation improving CPR results.     

Antiproliferative therapy with 5-fluorouracil in erbium:YAG laser sclerostomy ab externo

In the United States debate continues about the necessity of ventilation during CPR because of fear of contracting infectious diseases. Three questions will be considered in this article. First, is ventilation necessary for the treatment of cardiac arrest? Second, is mouth-to-mouth ventilation any better than no ventilation at all? Third, are other techniques of ventilation as effective or more effective than mouth-to-mouth ventilation during basic life support CPR? Although research is still inconclusive with regard to the need for ventilation during CPR, recent findings have clarified the effect of ventilation during low blood flow states and how ventilation influences resuscitation. Ventilation affects oxygenation, carbon dioxide elimination, and pH during times of low rates of blood flow. Ventilation may be unnecessary during the first few minutes of CPR. Under conditions of prolonged, untreated cardiac arrest, ventilation during CPR affects return of spontaneous circulation. Isolated hypoxemia and hypercarbia independently have adverse effects on survival of cardiac arrest. Because ventilation with exhaled gas contains as much as 4% CO2 and less oxygen than air, it may have adverse effects during CPR. Spontaneous gasping may provide sufficient ventilation during CPR. Chest compression alone provides some pulmonary ventilation and gas exchange. Active chest compression-decompression may improve gas exchange better than does standard chest compression. Other forms of manual ventilation may also have a role in CPR.     

Usefulness of central venous oxygen saturation monitoring during cardiopulmonary resuscitation. A comparative case study with end-tidal carbon dioxide monitoring

The usefulness of continuous monitoring of central venous oxygen saturation (ScvO2) in comparison with the capnogram during cardiopulmonary resuscitation (CPR) was demonstrated in a cardiac arrest patient. ScvO2 and end-tidal carbon dioxide (ETCO2) decreased following cessation of chest compression or increased during recovery of systemic circulation. During the complete stasis of systemic circulation, when defibrillation was done, ScvO2 did not change, while ETCO2 gradually decreased. However the larger decrease in ScvO2 temporally occurred when chest compression was resumed. And also the ScvO2 monitoring had great advantage to detecting peripheral tissue oxygenation. ScvO2 seems to be no less accurate and reliable monitoring than the capnogram during CPR procedures. Since the capnogram is non-invasively and easily used in cardiac arrest patients, ScvO2 monitoring combined with the capnogram is a more preferable method for assessing the efficacy of ongoing CPR.     

Cardiac output during cardiopulmonary resuscitation at various compression rates and durations

Cardiac output during cardiopulmonary resuscitation (CPR) was measured by a modified indicator-dilution technique in 20 anesthetized dogs (6-12 kg), during repeated 1- to 2-min episodes of electrically induced ventricular fibrillation, by a mechanical chest compressor and ventilator. With compression rates from 20 to 140/min and compression durations (duty cycles) from 10 to 90% of cycle time, cardiac output (CO) was predicted by the equation: CO = CR . SVmax . [DC/(k1 . CR + DC)] . [(1 -- DC)/k2 . CR + 1 - DC)], where CR is compression rate, DC is duty cycle, SVmax (19 ml) is the effective capacity of the pumping chamber, and k1 (0.00207 min) and k2 (0.00707 min) are ejection and filling constants. This expression predicts maximal CO for DC = 0.40 and cR = 126/min and 90-100% of maximal CO for 0.3 less than DC less than 0.5 and 70 less than CR less than 150/min. Such mathematical analysis may prove useful in the optimization of CPR.     

Comparison of sodium bicarbonate, Carbicarb, and THAM during cardiopulmonary resuscitation in dogs

OBJECTIVES: During cardiopulmonary resuscitation (CPR), elimination of CO2 was shown to be limited by low tissue perfusion, especially when very low perfusion pressures were generated. It has therefore been suggested that sodium bicarbonate (NaHCO3), by producing CO2, might aggravate the hypercarbic component of the existing acidosis and thereby worsen CPR outcome. The objectives of this study were to evaluate the effects of CO2 producing and non-CO2 producing buffers in a canine model of prolonged ventricular fibrillation followed by effective CPR. DESIGN: Prospective, randomized, controlled, blinded trial. SETTING: Experimental animal research laboratory in a university research center. SUBJECTS: Thirty-eight adult dogs, weighing 20 to 35 kg. INTERVENTIONS: Animals were prepared for study with thiopental followed by halothane, diazepam, and pancuronium. Ventricular fibrillation was electrically induced, and after 10 mins, CPR was initiated, including ventilation with an FIO2 of 1.0, manual chest compressions, administration of epinephrine (0.1 mg/kg every 5 mins), and defibrillation. A dose of buffer, equivalent to 1 mmol/kg of NaHCO3, was administered every 10 mins from start of CPR. Animals were randomized to receive either NaHCO3, Carbicarb, THAM, or 0.9% sodium chloride (NaCl). CPR was continued for up to 40 mins or until return of spontaneous circulation. MEASUREMENTS AND MAIN RESULTS: Buffer-treated animals had a higher resuscitability rate compared with NaCl controls. Spontaneous circulation returned earlier and at a significantly higher rate after NaHCO3 (in seven of nine dogs), and after Carbicarb (six of ten dogs) compared with NaCl controls (two of ten dogs). Spontaneous circulation was achieved twice as fast after NaHCO3 compared with NaCl (14.6 vs. 28 mins, respectively). Hydrogen ion (H+) concentration and base excess, obtained 2 mins after the first buffer dose, were the best predictors of resuscitability. Arterial and mixed venous Pco2 did not increase after NaHCO3 or Carbicarb compared with NaCl. CONCLUSIONS: Buffer therapy promotes successful resuscitation after prolonged cardiac arrest, regardless of coronary perfusion pressure. NaHCO3, and to a lesser degree, Carbicarb, are beneficial in promoting early return of spontaneous circulation. When epinephrine is used to promote tissue perfusion, there is no evidence for hypercarbic venous acidosis associated with the use of these CO2 generating buffers.     

Effect of selective aortic arch perfusion on median frequency and peak amplitude of ventricular fibrillation in a canine model

STUDY OBJECTIVE: To determine whether the computer-derived measures of median frequency or peak amplitude of ventricular fibrillation (VF), obtained by fast Fourier transform of the VF waveform, change during selective aortic arch perfusion in a canine model of cardiac arrest. METHODS: Eight mongrel dogs (including 4 control animals) were sedated, intubated, catheterized, and instrumented to record the electrocardiogram (digitally at 100 Hz, filtered with a finite impulse response filter at 2 Hz), right atrial pressure, and aortic pressure during resuscitation in a model of VF-induced cardiac arrest. After 10 minutes of VF-induced arrest, cardiopulmonary resuscitation (CPR) with a mechanical chest compression device was initiated. Beginning 2 minutes later, the 4 study animals received, every 2 minutes, 45 seconds of selective aortic arch perfusion (SAAP) with autologous blood infusions under high pressure. Defibrillation was attempted after 3 minutes of CPR and every minute thereafter. Both study and control groups received standard-dose epinephrine (.01 mg/kg) every 3 minutes by means of an intraaortic catheter. The median frequency, peak amplitude, and coronary perfusion pressure (CPP) during the 5-second period just before defibrillation were obtained with the use of computer algorithms. RESULTS: All SAAP animals and 1 control animal were resuscitated. Baseline measures of median frequency (8.4 +/- 1.5 versus 6.6 +/- 1.0 Hz) and peak amplitude (.18 +/- .05 versus .36 +/- .13 mV) were not different between the SAAP and control groups, respectively, at the start of CRP. SAAP infusion resulted in significant increases in the SAAP group compared with the control group: median frequency, 9.6 +/- .4 versus 7.3 +/- 1.4 Hz; peak amplitude, .74 +/- .21 versus .39 +/- .15 mV; and CPP, 40.5 +/- 7.1 versus 18.0 +/- 15.0 mm Hg, respectively. Median frequency correlated with CPP (r2 = .67). Peak amplitude did not correlate with CPP (r2 = .06). CONCLUSION: Median frequency and peak amplitude increase with SAAP during cardiac arrest in a canine model. This method of resuscitation was reliable in allowing restoration of a stable perfusing rhythm after defibrillation. Changes in measures of peak amplitude and median frequency may reflect interventions that enhance the likelihood of successful defibrillation and may thereby offer a noninvasive means of monitoring interventions during cardiac arrest.     

Lipid peroxidation in healthy fetuses, preterm and fullterm neonates

Thrombolytic therapy has been accepted in the treatment of acute myocardial infarction. Given historical recommendations that thrombolytic therapy is contraindicated in patients receiving CPR, its potential clinical benefit for facilitating conversion of rhythm in patients in refractory cardiac arrest has not been investigated. We present three case reports in which patients with confirmed acute myocardial infarction had a witnessed cardiac arrest in the ED. Standard Advanced Cardiac Life Support measures failed in all three cases. A bolus infusion of tissue plasminogen activator was administered during CPR in refractory ventricular fibrillation (two cases) and pulseless ventricular tachycardia (one case). Patients were given tissue plasminogen activator and had defibrillation, followed by a spontaneous return of circulation, with resuscitation and subsequent discharge. No postarrest sequelae were observed as a result of thrombolytic use during the resuscitative process. We conclude that bolus thrombolytic infusions during CPR may facilitate spontaneous return of circulation in select patients with confirmed acute myocardial infarction, witnessed cardiac arrest in the ED, and refractory ventricular fibrillation or tachycardia.     

Factors influencing CPR outcome in Siriraj Hospital

This prospective study of cardiopulmonary resuscitation was surveyed in Siriraj Hospital from 1 March 1996 to 31 May 1996. In a 3-month-period, 94 resuscitated patients were reported with initial survivors 31 cases (33%) and 3 patients (3%) were alive until discharged from the hospital. Most of the resuscitated patients belonged to the emergency department (47%) with the lowest survival rate (23%). The common causes of cardiac arrest were heart diseases (31%) and respiratory failure (21%). All survivors who were able to be discharged from the hospital had suffered cardiac arrest from heart diseases. After resuscitation, only half of the initial survivors received postarrest care in the intensive care units, the rest remained in general wards and outpatient department. By using logistic regression for multivariate analysis, the survival rate was correlated with locations of CPR, duration of CPR and duration of attempt endotracheal intubation. The initial survival outcome of CPR was not related to sex, age, time of day of CPR, duration of hospitalization before CPR, types of arrhythmia, delay in doctors' arrival and performers of CPR.     

Properties of recombinant bacteriophage T4 tail sheath protein and its deletion fragments

We aimed to determine whether our results were any better or worse than other published reports and to examine the efficacy of the West Midlands Ambulance Service (WMAS) policy of applying cardiopulmonary resuscitation (CPR) and manual ventilation to all unwitnessed cardiac arrests in preference to immediate defibrillation. All cardiac arrests were studied from October 1994 to September 1996. In all unwitnessed arrests, crews undertook CPR and manually ventilated the lungs via a mask or an endotracheal tube with a bag and valve or a mechanical resuscitator using an FIO2 of 1 or 0.21 for at least 2 min before defibrillation was attempted. There were 3403 diagnosed cardiac arrests but, in these, the diagnosis was not certain. CPR and advanced life support (ALS) were applied in 3380 patients and return of spontaneous circulation (ROSC) was obtained in 554, giving a success rate of 16.4%. A total of 364 patients were accepted into hospital, 90 patients died in A&E but 274 patients were admitted to ICU/CCU. Seventy died within 24 h, 69 died after 24 h and 135 were discharged alive and well without cerebral damage. The final success to discharge rate was 49.27%. Of those discharged, 69 had a circulatory arrest period of more than 4 min but in only 10 was a bystander available to start CPR. The European Resuscitation Council Guidelines recommending immediate defibrillation for unwitnessed arrests are not supported by these results. The apparent lack of cerebral damage and the percentage success suggests that resuscitation considerations should be as brain orientated as they are heart orientated. The elapsed time periods reported challenge several shibboleths.     

Interposed abdominal compression in mechanical cardiopulmonary resuscitation. Description of a clinical case

Among the different techniques proposed to integrate the standard cardiopulmonary resuscitation (sCPR) protocol, mechanical CPR (mCPR) and interposed abdominal compression (IAC) were found to be particularly effective for the simplicity of the procedure and the significant results obtained. A case of a 54-year old male with cardiogenic shock following viral infection, in which prolonged mechanical cardiopulmonary resuscitation with interposed abdominal compression was performed, is presented. Five hours after admission in the ICU, the patient's condition worsened with subsequent cardiac arrest with pulseless electrical activity (PEA). Mechanical CPR was promptly started, subsequently associated with IAC and prolonged for 1 hour and 20 minutes. Although the patient survived for only eight hours following cardiac arrest, prolonged IAC-mCPR allowed to start extra corporeal circulation (CPP). The patient was then transferred to the cardiosurgical operating theatre for ventricular assistance by centrifugal pump (VAP). Cardiovascular data obtained from patients monitoring did not shown any cardiac lesions or adverse effects as observed by autoptic examination and suggest the reliability of this mechanical method, which allows a better performance when compared to standard CPR. In prolonged resuscitations a few contraindications to both mCPR and IAC suggest the application of the associated techniques at all times in cardiac arrest, combining the benefits of both procedures.     

Visceral, hematologic and bacteriologic changes and neurologic outcome after cardiac arrest in dogs. The visceral post-resuscitation syndrome

We studied the post-resuscitation syndrome in 42 healthy dogs after normothermic ventricular fibrillation cardiac arrest (no blood flow) of 7.5, 10, or 12.5 min duration, reversed by standard external cardiopulmonary resuscitation (CPR) (< or = 10 min) and followed by controlled ventilation to 20 h and intensive care to 72 h. We reported previously, in the same dogs, no difference in resuscitability, mortality, or neurologic outcome between the three insult groups. There was no pulmonary dysfunction, but post-arrest cardiovascular failure, of greater severity in the 12.5 min arrest group. This report concerns renal, hematologic, hepatic and bacteriologic changes. Renal function recovered within 1 h after arrest, without permanent dysfunction. Clotting derangements at 1-24 h postarrest reflect transient disseminated intravascular coagulation with hypocoagulability, more severe after longer arrests, which resolved by 24 h after arrest. Hepatic dysfunction was transient but more severe in the animals that did not recover consciousness and correlated with neurologic dysfunction, but not with brain histologic damage. Bacteremia was present in all animals postarrest. We conclude that in the previously healthy organism after cardiac arrest of 7.5-12.5 min no flow, visceral and hematologic changes, although transient, can retard neurologic recovery.     

《2010年美国心脏协会心肺复苏与心血管急救指南》的亮点

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Serum neuron-specific enolase as early predictor of outcome after cardiac arrest

OBJECTIVE: To examine the prognostic value of serum neuron-specific enolase for early prediction of outcome in patients at risk for anoxic encephalopathy after cardiac arrest. DESIGN: Prospective study. SETTING: Coronary intensive care unit of the University of Heidelberg. PATIENTS: Forty-three patients (66.8 +/- 12.7 [SD] yrs, range 33 to 85) who had had either primary or secondary cardiac arrest, followed by cardiopulmonary resuscitation (CPR). INTERVENTIONS: Serial blood samples and clinical examinations. MEASUREMENTS AND MAIN RESULTS: Serum neuron-specific enolase concentrations were determined after CPR on 7 consecutive days. Twenty-five patients remained comatose and subsequently died; 18 patients survived the first 3 months and had no relevant functional deficit at 3-month follow-up. Neuron-specific enolase concentrations were correlated with neurologic outcome. Concentrations of >33 ng/mL predicted persistent coma with a high specificity (100%) and a positive predictive value of 100%. Overall sensitivity was 80%, with a negative predictive value of 78%. Serum concentrations of neuron-specific enolase exceeded this cutoff value no more than 3 days after cardiac arrest in 95% of patients in whom these concentrations had exceeded 33 ng/mL. CONCLUSIONS: In patients who have been resuscitated after cardiac arrest, serum neuron-specific enolase concentrations of >33 ng/mL predict persistent coma with a high specificity. Values below this cutoff level do not necessarily indicate complete recovery, because this method has a sensitivity of 80%.     

Non-invasive continuous haemodynamic and PETCO2 monitoring during peroperative cardiac arrest

We describe a cardiac arrest which occurred during general anaesthesia in the prone position for surgical correction of lumbar kyphosis in a patient with Marfan's syndrome. Peroperative monitoring was routine with ECG, non-invasive arterial pressure, oximetry, PETCO2 and central venous pressure, plus aortic blood flow and and systolic time intervals via an oesophageal echo-Doppler device. Forty-five minutes after the start of surgery, a sudden decrease in aortic blood flow followed by a decrease in PETCO2 suggested acute cardiac failure despite continuation of the ECG signal. Initial CPR in the prone position produced a slight increase in PETCO2. When the patient was turned to the supine position and the legs elevated, chest compression was more efficient and spontaneous circulation was rapidly restored. Circulatory arrest could be explained by incompletely treated hypovolaemia, or by myocardial depression (decrease in aortic blood flow and lengthened pre-ejection period) combined with excessive hypotension in a patient with Marfan's syndrome, thus compromising coronary blood flow producing ST segment depression. Continuous non-invasive aortic blood flow and PETCO2 monitoring proved valuable in the early detection and treatment of circulatory arrest and in the evaluation of the efficiency of peroperative CPR.     

Current concepts in cardiopulmonary resuscitation

The "chain of survival" is important in the resuscitation of a patient who has had a cardiac arrest. The provision of Basic Life Support (BLS) and Advanced Cardiac Life Support (ACLS) is essential in this "chain of survival." Both BLS and ACLS have undergone several revisions since their initial inception. This article reviews (1) the current established and investigational issues of cardiopulmonary resuscitation, (2) the incidence and outcomes of anesthesia-related cardiac arrest, (3) the use of cardiopulmonary bypass in resuscitation, and (4) cerebral protection during and after resuscitation.     

Substrate specificity of human prolyl-4-hydroxylase

BACKGROUND: The mechanism responsible for the forward blood flow associated with external chest compression is still controversial. Evidence for both blood flow caused by direct cardiac compression and blood flow generated by a general increase in intrathoracic pressure has been found in experimental as well as clinical studies. No data are available concerning the mechanism causing forward blood flow in hypothermic patients undergoing cardiopulmonary resuscitation. Therefore, echocardiographic findings during external chest compression in seven hypothermic arrest victims are reported. METHODS: All transesophageal echocardiographic studies performed at the Anaesthesia department between 1994 and 1997 were reviewed and seven hypothermic patients with transesophageal echocardiography performed during cardiopulmonary resuscitation were identified. RESULTS: An open mitral valve or a circumferential reduction in aortic diameter during the compression phase was found in four of seven patients, indicating that primarily an increase in intrathoracic pressure (thoracic pump mechanism) generated forward blood flow. In three patients, mitral valve closure during external chest compression indicated that direct cardiac compression (cardiac pump mechanism) contributed to forward blood flow. Two patients studied during active compression-decompression cardiopulmonary resuscitation demonstrated enhanced right ventricular filling and aortic valve opening during active decompression of the thorax. CONCLUSIONS: In contrast to normothermic arrest victims, an open mitral valve during external chest compression is a common finding during hypothermia, indicating that thoracic pump mechanism is important for forward blood flow during cardiopulmonary resuscitation in hypothermic arrest victims. Aortic valve opening in two hypothermic arrest victims suggests forward blood flow also during active decompression of the thorax with the Cardiopump.     

Lidocaine prolongs the safe duration of circulatory arrest during deep hypothermia in dogs

PURPOSE: To test the hypothesis that lidocaine prolongs the safe period of circulatory arrest during deep hypothermia. METHODS: Sixteen dogs were subjected to cooling, first surface cooling to 30 degrees C and then core cooling to 20 degrees C rectal temperature). The circulation was then stopped for 90 min. In the lidocaine group, 4 mg.kg-1 lidocaine was injected into the oxygenator two minutes before circulatory arrest and 2 mg.kg-1 at the beginning of reperfusion and rewarming. The control group received equivalent volumes of normal saline. Post-operatively, using a neurological deficit scoring system (maximum deficit score-100; minimum-zero indicating that no scored deficit could be detected). Neurological function was evaluated hourly for six hours and then daily for one week, the pharmacokinetic parameters were calculated using one compartment model. RESULTS: On the seventh day, the neurological deficit score and overall performance were better in the lidocaine (0.83 +/- 2.04) than in the control group (8.33 +/- 4.08 P < 0.05). During the experiment, the base excess values were also better in the lidocaine than in the control group (at 30 min reperfusion: -4.24 +/- 1.30 vs -8.20 +/- 2.82 P < 0.01, at 60 min reperfusion was -3.34 +/- 1.87 vs -7.52 +/- 2.40 (P < 0.01). On the eighth day the extent of pathological changes were milder in the lidocaine group than that in the control group. The elimination half life of lidocaine was 40.44 +/- 7.99 during hypothermia and 2.01 +/- 4.56 during rewarming. CONCLUSIONS: In dogs lidocaine prolongs the safe duration of circulatory arrest during hypothermia.     

Mortality among workers in the pulp-paper industry. A successive follow up of the cohort

Neuropathologic findings are described, for the first time, in a neonatal dog model of circulatory arrest in normothermic conditions, and the findings are compared to those reported in neonatal dogs with hypothermic circulatory arrest. Total circulatory arrest was produced in 3- to 6-day-old anesthetized, paralyzed and ventilated, normothermic dogs either by asphyxiation or cardioplegia. Duration of circulatory arrest was 8-20 min and 10-40 min in asphyxiated and cardioplegic animals, respectively. The animals were resuscitated and maintained under controlled systemic physiologic conditions until neuropathologic examination after 8 or 24 h of recovery. The results suggest that the minimal durations of circulatory arrest for brain damage to occur following asphyxia or cardioplegia are 10 and 15 min, respectively. Ischemic lesions in both groups consisted of neuronal necrosis and involved mainly the brain stem structures, particularly the reticular nuclei and the spinal cord gray matter. The medulla was more severely involved than midbrain and pons. There was a direct correlation between the length of circulatory arrest and the severity of damage in the medulla (P = 0.001) and overall brain stem damage (P = 0.004) in animals with cardioplegia, but not in animals with asphyxia. These findings are compared to the neuropathologic changes previously described in newborn dogs subjected to hypothermic circulatory arrest, in which ischemic lesions are focused on the cerebral cortex and basal ganglia. It is concluded that hypothermia in this model not only prolongs the period of circulatory arrest that is required to produce brain damage, but also shifts the pattern of regional ischemic vulnerability from caudal to more rostral structures.