The effect of hypothermic circulatory arrest time on cerebral function, morphology, and biochemistry

Neuronal injury and tumor necrosis factor-alpha immunoreactivity in the rat hippocampus in the early period of asphyxia-induced cardiac arrest under normothermia

Low survival rate occurs in patients who initially experience a spontaneous return of circulation after cardiac arrest (CA). In this study, we induced asphyxial CA in adult male Sprague-Daley rats, maintained their body temperature at 37 ± 0.5°C, and then observed the survival rate during the post-resuscitation phase. We examined neuronal damage in the hippocampus using cresyl violet (CV) and Fluore-Jade B (F-J B) staining, and pro-inflammatory response using ionized calcium-binding adapter molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), and tumor necrosis factor-alpha (TNF-α) immunohistochemistry in the hippocampus after asphyxial CA in rats under normothermia. Our results show that the survival rate decreased gradually post-CA (about 63% at 6 hours, 37% at 1 day, and 8% at 2 days post-CA). Rats were sacrificed at these points in time post-CA, and no neuronal damage was found in the hippocampus until 1 day post-CA. However, some neurons in the stratum pyramidale of the CA region in the hippocampus were dead 2 days post-CA. Iba-1 immunoreactive microglia in the CA1 region did not change until 1 day post-CA, and they were activated (enlarged cell bodies with short and thicken processes) in all layers 2 days post-CA. Meanwhile, GFAP-immunoreactive astrocytes did not change significantly until 2 days post-CA. TNF-α immunoreactivity decreased significantly in neurons of the stratum pyramidale in the CA1 region 6 hours post-CA, decreased gradually until 1 day post-CA, and increased significantly again 2 days post-CA. These findings suggest that low survival rate of normothermic rats in the early period of asphyxia-induced CA is related to increased TNF-α immunoreactivity, but not to neuronal damage in the hippocampal CA1 region.

Regional cerebral perfusion for surgical correction of neonatal aortic arch obstruction

One-stage repair of aortic arch obstruction and associated cardiac anomalies is a surgical challenge in infants.The purpose of the present study is to review the current outcome using regional cerebral perfusion (RCP) during a procedure correcting interrupted aortic arch (IAA) and also isolated aortic coarctation (CoA) and CoA combined with hypoplastic aortic arch (CoA-HyAA) in our center. Between January 2007 and July 2008, 24 infant patients with interrupted aortic arch (IAA) (n=3), isolated aortic coarctation (iCoA) (n=9) and aortic coarctation with hypoplastic aortic arch (CoA-HyAA) (n=12) underwent one-stage surgical correction in our hospital. End-to-end anastomosis was employed in 12 infants (IAA n=3 and iCoA n=9); for the other 12 patients with CoA-HyAA, an end-to-end extended anastomosis was used in 8 cases, end-to-side anastomosis in 2 cases, and composite heterologous pericardial patch in 2 cases. RCP with 40 mL/kg/min through the innominate artery during aortic arch reconstruction was employed for all pediatric patients. One single-dose histidine-ketoglutarate-tryptophan (HTK) solution was used for myocardial protection during CPB. Cardiopulmonary bypass time and aortic cross-clamp time were 165.6±32.4min and 81.7±30.0min, respectively. The mean regional cerebral perfusion time was 31.0±10.6min; lowest nasopharyngeal temperature was 19.1±1.1°C. Operative mortality rate in both groups was 8.3%. Mean follow-up was 10.5±4.8 months. There was no late mortality or postoperative neurologic, renal or hepatic complications. All patients are asymptomatic and are developing normally. One-stage total arch repair using the RCP technique is an excellent method that may minimize neurologic and renal complications. Our surgical strategy for arch anomaly has a low rate of residual and recurrent coarctation when performed in these infants.

Deep Hypothermic Circulatory Arrest for Complex Cerebral Aneurysms: Lessons Learned

OBJECTIVE

Deep hypothermic circulatory arrest is a useful adjunct for treating complex aneurysms. Decreased cerebral metabolism and resultant ischemic tolerance create an environment suitable for devascularizing high-risk lesions. However, the advent of modern imaging modalities, innovative cerebral revascularization strategies, and the emergence of endovascular stenting and coiling limit the number of aneurysms requiring this surgical intervention. We present 66 patients with intracranial aneurysms who underwent surgical clipping under deep hypothermic arrest and attempt to identify patients well-suited for this procedure.

METHODS

This study was conducted during a 15-year period and examined patients with aneurysms of the anterior and posterior cerebral circulation. Demographics, aneurysm characteristics, and surgical factors were evaluated as predictors of functional outcome.

RESULTS

Patient age and the duration of cardiac arrest were independent predictors of early clinical outcome (P < 0.05). Our experience suggests that the ideal patient is younger than 60 years old and harbors few medical comorbidities. Individuals with large aneurysms of the anterior communicating artery, internal carotid artery bifurcation, posterior inferior cerebellar artery, midbasilar, or vertebral arteries and with an absence of thrombosis and calcium may be most likely to experience favorable outcomes. Circulatory arrest should not exceed 30 minutes. Postoperative computed tomographic scanning and timely anesthetic emergence allow for early detection of hemorrhage. Complete dissection of the aneurysm before bypass and avoiding extreme hypothermia yield a low incidence of life-threatening postoperative hematomas.

CONCLUSION

Hypothermic circulatory arrest is a useful technique for neuroprotection during the clipping of complex cerebral aneurysms. This procedure, however, has several associated risks. Patient factors, pathoanatomic characteristics, and surgical parameters may be used to guide patient selection.

Neurocognitive consequences of surgically corrected congenital heart defects: A review

With advances in surgical procedures, neuropsychological assessment after congenital heart defects and pre, peri- and/or postoperative predictors of adverse outcome has become an important focus in research. We aim to summarize neuropsychological sequelae associated with different types of congenital heart defects, critically review the methodology used in more than 20 empirical studies that were retrieved from biomedical electronic search engines, and identify possible directions for future research. Despite the lack of adequate control groups and long-term studies, there seem to be some cognitive deficits. The largest group of children with isolated congenital heart defects present with normal intellectual capacities. However, they tend to show language deficits and motor dysfunction. Although performances on memory tasks are good, unambiguous conclusions concerning their attentional and executive functioning are still lacking. Serious behavioral problems are not an issue. In addition to a detailed description of the (neuro) psychological consequences of pediatric cardiac surgery, an overview of the predictors of the cognitive defects is provided.

Arch reconstruction without circulatory arrest: current clinical applications and results of therapy

Laboratory and clinical data have confirmed the deleterious effects of deep hypothermic circulatory arrest. Long-term data and rigorous neuropsychiatric data are currently sparse, but that which are available show adverse outcomes following circulatory arrest, and therefore support the use of continuous perfusion techniques. There are no available long-term data on continuous perfusion techniques with respect to neurologic outcomes, but using these techniques the incidence of postoperative seizures or other neurologic events is rare. Currently available bypass systems and microsurgical techniques have allowed continuous flow and regional perfusion to become practical alternatives. Several innovative techniques for avoiding circulatory arrest during neonatal aortic arch reconstruction for univentricular and biventricular hearts are described. It would appear prudent and desirable to provide continuous perfusion now that long-term survival after repair of even the most complex cardiac anomalies including single ventricle defects is commonplace.

Effect of deep hypothermia on cerebral hemodynamics during selective cerebral perfusion with systemic circulatory arrest

OBJECTIVE

We studied the effect of deep hypothermia on cerebral hemodynamics during selective cerebral perfusion with systemic circulatory arrest.

METHODS

Ten anesthesized pigs were placed on cardiopulmonary bypass and cooled to a rectal temperature of 22 degrees C (n = 5) or 15 degrees C (n = 5). During selective cerebral perfusion, the descending aorta was clamped and perfusion of the lower body was discontinued. As the pump flow was changed, we monitored the perfusion pressure, local cerebral blood flow, and local cerebral oxygenation using laser Doppler flowmetry and near-infrared spectroscopy. We also measured the free flow of the left internal thoracic artery during selective cerebral perfusion.

RESULTS

Perfusion pressure and local cerebral blood flow decreased as the pump flow decreased. Oxygenated and deoxygenated hemoglobin in cerebral tissue remained unchanged at a perfusion flow of 10 ml/kg/min, whereas oxygenated hemoglobin decreased and deoxygenated hemoglobin increased progressively and reciprocally as the pump flow decreased. The pump flow for maintaining perfusion pressure above 35 mmHg with stabilized local cerebral oxygenation was significantly higher at 15 degrees C than at 22 degrees C. The internal thoracic artery free flow was higher at 15 degrees C than at 22 degrees C.

CONCLUSIONS

Selective hypothermic cerebral perfusion with systemic circulatory arrest produces an extracranial shunt through the internal thoracic artery, especially under deep hypothermia. Our data suggests that selective cerebral perfusion during deep hypothermia is best managed by perfusion pressure control rather than by flow control.

Neurological Complications of Aortic Surgery

Surgery of the aortic arch involves an inherently high risk of neurological complications. A number of factors have been identified which may predispose the patient to brain injury, and various techniques employed in an attempt to counteract these are outlined. In particular the vulnerability of the brain to ischemia has led to the development of three adjunctive cerebral protective techniques, hypothermic circulatory arrest, retrograde cerebral perfusion and selective antegrade cerebral perfusion, all based upon brain cooling and metabolic inhibition. The relative merits and disadvantages of these techniques are therefore discussed. Finally, pharmacologic adjuncts and potential future developments in aortic arch surgery are discussed.

Cardiopulmonary bypass in infants and children

Cardiopulmonary bypass (CPB) systems have evolved from futuristic visions of surgical pioneers to a safe and efficient tool in the therapy of treatment of cardiac disorders. There are many significant differences in the physiology between neonates and adult patients. There are currently very few congenital cardiac malformations that cannot be addressed effectively with surgical therapy. Yet, the necessity of CPB in the repair of these patients can still result in significant morbidity. A clearer understanding of the effects of CPB, hypothermia, and circulatory arrest is evolving and there is a considerable amount of research in these areas. It seems likely that modification of current CPB systems, minimization of exposure, and surgical techniques to avoid or limit the adverse effects may reduce mortality and morbidity in the future. The problems faced in these complex patients and procedures require that infant and neonatal cardiac surgery be performed in specialized centers with a multidisciplinary approach and specialized personnel. Future improvements in technology will likely result in improved long term outcome for children with congenital cardiac disease. Copyright 2000 by W.B. Saunders Company

Aortic arch repair using hypothermic circulatory arrest technique associated with pharmacological brain protection

OBJECTIVE

Hypothermic circulatory arrest is a standard procedure for the treatment of aortic arch. However, there is a time limit for this procedure. There is now an urgent need to develop prophylactic measures to extend the time limit. We have used a pharmacological mixture of thiopental, nicardipine and mannitol for all patients undergoing circulatory arrest since 1991 to extend the safe limit. The purpose of this study was to analyze the neurological complications demonstrated by these patients and to evaluate the brain-protective effects of our measure.

METHODS

The clinical records of 75 consecutive patients undergoing an aortic arch repair using a hypothermic circulatory arrest technique during the past 8 years were retrospectively reviewed. Systemic cooling was continued until a total disappearance of EEG activity. Prior to circulatory arrest, 15 or 30 mg/kg of thiopental, 20 mg of nicardipine and 300 ml of mannitol were infused into the venous reservoir of a cardiopulmonary bypass circuit. Graft replacement was performed in all patients and the extent of replacement was a total aortic arch in 43 patients, a distal aortic arch in 17, a hemiarch in 13 and a distal aortic arch and a total descending aorta in two.

RESULTS

The duration of circulatory arrest ranged from 16 to 80 min (mean 41.5 min), and it exceeded 45 min in 37 patients. Operative mortality was 10.7% and two patients died of stroke. Three patients had permanent and three other patients had transient neural deficits. The incidence of stroke was 8.0% as a whole, and no correlation between the incidence of neurological complications and the duration of circulatory arrest was found. A multivariate analysis showed that the duration of circulatory arrest was determined as a predictor of neither operative mortality nor postoperative stroke.

CONCLUSIONS

The findings of the present study suggest that our pharmacological brain protection appears to be effective for safely extending hypothermic circulatory arrest.

Neurological evaluation and intelligence testing in the child with operated congenital heart disease

BACKGROUND

The immediate and intermediate-term neurodevelopmental outcome in infants undergoing open heart procedures using deep hypothermic cardiopulmonary bypass was assessed prospectively.

METHODS

One hundred consecutive infants (age 2 to 174 days) were operated on using either deep hypothermic bypass only (group A, n = 28), or with associated circulatory arrest (group B, n = 72). Early neurological outcome was recorded. Survivors underwent mental development evaluation after 31 to 55 months. Fifty other children of similar demographic profile but without heart disease were also tested as controls.

RESULTS

In group A, there were two neurological deaths. In group B, 5 patients had clinical seizures, 1 had monoparesis and 1 had hyperkinetic syndrome with decreased attention span. Mean mental performance quotient was 90.0+/-8.2 in group A, and 89.1+/-6.8 in group B, (group A vs. B, p = 0.60). Mean mental performance quotient in the control group was 101.4+/-8.4, which was significantly higher than the patient population (p << 0.001). No correlation was found between duration of circulatory arrest and postoperative mental performance quotient.

CONCLUSIONS

There was significant retardation of mental development in infants operated with deep hypothermic cardiopulmonary bypass. However, use of total circulatory arrest and its duration did not affect clinical outcome up to preschool age.

Regional low-flow perfusion provides cerebral circulatory support during neonatal aortic arch reconstruction

OBJECTIVE

Because of concerns regarding the effects of deep hypothermia and circulatory arrest on the neonatal brain, we have developed a technique of regional low-flow perfusion that provides cerebral circulatory support during neonatal aortic arch reconstruction.

METHODS

We studied the effects of regional low-flow perfusion on cerebral oxygen saturation and blood volume as measured by near-infrared spectroscopy in 6 neonates who underwent aortic arch reconstruction and compared these effects with 6 children who underwent cardiac repair with deep hypothermia and circulatory arrest.

RESULTS

All the children survived with no observed neurologic sequelae. Near-infrared spectroscopy documented significant decreases in both cerebral blood volume and oxygen saturations in children who underwent repair with deep hypothermia and circulatory arrest as compared with children with regional low-flow perfusion. Reacquisition of baseline cerebral blood volume and cerebral oxygen saturations were accomplished with a regional low-flow perfusion rate of 20 mL x kg(-1) x min(-1).

CONCLUSIONS

Regional low-flow perfusion is a safe and simple bypass management technique that provides cerebral circulatory support during neonatal aortic arch reconstruction. The reduction of deep hypothermia and circulatory arrest time required may reduce the risk of cognitive and psychomotor deficits.

Serum S100B and hypothermic circulatory arrest in adults

BACKGROUND

Cerebral injury is the most important complication of cardiac operations with cardiopulmonary bypass. Prolonged total circulatory arrest (TCA) can expose patients to an even greater risk of cerebral injury. We sought to detect the degree of cerebral injury in adults who had thoracic aortic operations with TCA by measuring S100B protein, which is released into the circulation after cerebral injury.

METHODS

Serial measurements of S100B protein, a highly specific serum marker of astroglial damage, were performed in 26 patients who had complex aortic operations, of whom 13 required cardiopulmonary bypass alone (for aortic root replacement), and in 13 patients who required an additional period of TCA (for type A aortic dissections and arch aneurysms). Blood samples were taken preoperatively, at skin closure, and 5 and 24 hours postoperatively.

RESULTS

There were significant increases in serum S100B concentrations in all patients, and peak levels occurred at skin closure. The magnitude of the increase in S100B was significantly greater at all postoperative time points and persisted longer in the TCA group. There was a significant correlation between the duration of the TCA and S100B concentration at 5 hours (r = 0.66, p = 0.01) and 24 hours (r = 0.63, p = 0.02) postoperatively.

CONCLUSIONS

S100B levels were higher in all patients who had complex aortic operations and were significantly greater in patients requiring a period of TCA. The duration of the TCA period correlated with S100B levels 5 hours and at 24 hours postoperatively. Circumstantial evidence, in accordance with other studies, suggests that S100B protein is a marker for cerebral injury during cardiac operations.

Mechanisms of brain injury during infant cardiac surgery

Neurological injury is a major and often debilitating complication of congenital heart disease and open-heart surgery. Paradoxically, the full impact of this complication has been underscored by the marked decrease in mortality and the rescue of infants with desperate and previously lethal heart conditions. Although recent focus has been on mechanisms of brain injury originating during open-heart surgery, this article also emphasizes the importance of mechanisms initiated or perpetuated during the preoperative and postoperative periods. In addition to the usually implicated mechanism of hypoxia-ischemia, recent genetic advances suggest an important role for genetic deletion syndromes. Inflammatory cascades have been implicated in the end-organ injury seen after cardiopulmonary bypass and might play a role in neurological dysfunction. These mechanisms are reviewed, with an emphasis on recent developments in our understanding of brain injury in this population.

The pursuit of effective neuroprotection during infant cardiac surgery

Advances in infant cardiac surgery have resulted in a dramatic decline in mortality rates; however, neurological morbidity remains an important concern. The effectiveness of a number of interventional strategies to prevent or minimize brain injury during open heart surgery are currently being investigated. This article provides an overview of two approaches: (1) interventions to enhance intraoperative cerebral oxygenation so as to prevent hypoxic-ischemic insults, and (2) the application of cerebral rescue therapies to attenuate the cascade of brain injury. Infant cardiac surgery provides a controlled environment in which to apply these neuroprotective approaches, so as to optimize the quality of life of these vulnerable children.

Selective Cerebral Perfusion Via Innominate Artery in Aortic Arch Replacement Without Deep Hypothermic Circulatory Arrest

To attain satisfactory results in aortic arch surgery a reliable method of cerebral protection, avoidance of emboli, and control of hemorrhage is mandatory. Deep hypothermic circulatory arrest is the most common technique at present but gives only a limited period of protection, whereas a complicated aortic arch operation may require more time than anticipated. Therefore the selective cannulation and perfusion of the innominate artery has not been widely used until now because it is uncertain whether the left hemisphere of the brain is adequately perfused. Between 1990 and 1995, 21 of 69 patients within the last 36 months, consisting of 15 men and 6 women averaging 45 +/- 13.4 years, underwent operative treatment for aneurysm (n = 9) or type A dissection (n = 12) involving the aortic valve and aortic arch; selective innominate perfusion (SCP [i]) in moderate hypothermia (28 degreesC) for brain protection was used. Extended perioperative monitoring included bilateral somatosensory-evoked potentials (SEP), transcranial Doppler sonography (TCD), a computer-aided topographical electro-encephalometry (CATEEM), and analysis of the arterial and venous oxygen saturation and desaturation. Mean time periods were 229.7 +/- 56.5 minutes for extracorporeal circulation, 151.7 +/- 34.1 minutes for aortic cross-clamping, and 67.05 +/- 34.03 for selective cerebral perfusion via the innominate artery. Not once did the intraoperative monitoring reveal hints of cerebral damage due to inadequate perfusion. All patients survived surgery but two could not be weaned from the respirator; one died 2 days and the other 6 days after the operation due to multiple organ failure (MOF). Another two patients died after 13 days due to untreatable septic syndrome with pulmonary insufficiency. All four patients died within 30 days, during which time they had aortic dissection involving the complete aortic arch and severe aortic valvular incompetence (grade IV). There was no late death and follow-up time of 19.76 +/- 8.04 months revealed an overall mortality rate of 19%. Only temporary neurological affections (left-sided hemiparesis) were found in two patients (9.5%). Additionally, we observed neuropsychological disturbances in one of these. Our first experience with selective cerebral perfusion via innominate artery and the attendant CATEEM monitoring for assessment of adequate bilateral cerebral perfusion suggests that this method is a useful addition to the armamentarium in complicated aortic arch surgery.

Cerebral physiology in paediatric cardiopulmonary bypass

PURPOSE

To analyze studies of neurological injury after open-heart surgery in infants and children and to discuss the effects of cardiopulmonary bypass, hypothermia and deep hypothermic circulatory arrest on cerebral blood flow, cerebral metabolism and brain temperature.

SOURCE

Articles were obtained from the databases, Current Science and Medline, from 1966 to present. Search terms include cardiopulmonary bypass (CPB), hypothermia, cerebral blood flow (CBF), cerebral metabolism and brain temperature. Information and abstracts obtained from meetings on the topic of brain and cardiac surgery helped complete the collection of information.

PRINCIPAL FINDINGS

In adults the incidence of neurological morbidity is between 7 to 87% with stroke in about 2-5%, whereas the incidence of neurological morbidity increases to 30% in infants and children undergoing cardiopulmonary bypass. Besides the medical condition of the patient, postoperative cerebral dysfunction and neuronal ischaemia associated with cardiac surgery in infants and small children are a combination of intraoperative factors. Deep hypothermic circulatory arrest impairs CBF and cerebral metabolism even after termination of CPB. Inadequate and/or non-homogenous cooling of the brain before circulatory arrest, as well as excessive rewarming of the brain during reperfusion are also major contributory factors.

CONCLUSION

Newer strategies, including the use of low-flow CPB, pulsatile CPB, pH-stat acid-base management and a cold reperfusion, are being explored to ensure better cerebral protection. Advances in monitoring technology and better understanding of the relationship of cerebral blood flow and metabolism during the different modalities of cardiopulmonary bypass management will help in the medical and anaesthetic development of strategies to improve neurological and developmental outcomes.

Prolongation of total permissible circulatory arrest duration by deep hypothermic intermittent circulatory arrest

OBJECTIVE

We determined whether the duration of permissible circulatory arrest could be prolonged by deep hypothermic intermittent circulatory arrest.

METHODS

Twenty-five beagles were cooled on bypass to 18 degrees C to initiate deep hypothermia that was maintained for 3 hours. Five protocols were then studied: group 1, uninterrupted bypass during hypothermia; group 2, arrest for 40 minutes during hypothermia; group 3, arrest for 60 minutes during hypothermia; group 4, arrest for 80 minutes during hypothermia; and group 5, intermittent circulatory arrest, consisting of six cycles of 20 minutes of arrest followed by 10 minutes of systemic recirculation during hypothermia (total, 120 minutes of arrest). The oxyhemoglobin concentration in the brain was measured with near infrared spectrophotometry.

RESULTS

In groups 2, 3, and 4, the oxyhemoglobin concentration in the brain decreased continuously after arrest, finally reaching a plateau after 24.9 +/- 1.2 minutes. This finding suggested that the available cerebral oxyhemoglobin was depleted. In contrast, the available cerebral oxyhemoglobin was not depleted during hypothermic intermittent arrest in group 5. The mitochondrial respiratory control index was significantly lower in group 4 than in the other groups (p < 0.05). However, there were no significant differences in the respiratory control index for groups 1, 2, 3, and 5. Moreover, the formation of brain edema was significantly lower in group 5 than in the other groups (p < 0.05).

CONCLUSIONS

These results indicate that deep hypothermic intermittent arrest can increase the duration of total permissible circulatory arrest and will be a useful modality when prolonged arrest is anticipated.

Anesthesia for deep hypothermic circulatory arrest in adults: experience with the first 50 patients

OBJECTIVE

To evaluate the efficacy of a simple method of central nervous system (CNS) protection in patients undergoing deep hypothermic circulatory arrest (DHCA) lasting less than 30 minutes, for a variety of complex cardiovascular procedures.

DESIGN

A retrospective case review.

SETTING

A university teaching hospital.

PARTICIPANTS

Fifty consecutive patients (25 women, 25 men) undergoing elective or emergency cardiovascular operations requiring DHCA between August 1991 and December 1996.

INTERVENTIONS

Patients underwent DHCA for a variety of surgical procedures. Neurologic protection was with thiopental, ice packs to the head, and systemic core hypothermia to a nasopharyngeal temperature (NPT) of 18 degrees to 20 degrees C.

MEASUREMENTS AND MAIN RESULTS

The mean duration of circulatory arrest was 18 +/- 10 minutes (range, 5 to 42 minutes). The mean NPT at time of arrest was 18.7 degrees +/- 1.7 degrees C. Three patients (6%) had gross CNS morbidity, one of whom died. The circulatory arrest times for these three patients were 8, 39, and 40 minutes. Perioperative mortality was 8% (n = 4). The circulatory arrest times for the patients who died were 12, 13, 23, and 39 minutes.

CONCLUSION

The anesthetic management of DHCA described is simple, effective, and safe, and can be performed in any institution that performs cardiac surgery.

Deep hypothermic intermittent circulatory arrest--an adjunct technique for operations on aneurysms involving the aortic arch

Aneurysms involving the aortic arch were repaired in 12 patients using a technique known as deep hypothermic intermittent circulatory arrest (DHICA). This technique consists of repeated cycles of 20 min of circulatory arrest and 10 min of cerebral and systemic reperfusion. Aneurysms were of the following types: 2 true atherosclerotic aneurysm, 8 aortic dissections, and 2 traumatic aneurysm. There were 2 operative deaths caused by coagulopathy as a result of hepatic failure and difficulty with left ventricular venting. The frequency of circulatory arrest ranged from 2 to 5 cycles, and total circulatory arrest ranged from 20 to 71 min (mean 43.6 min). The lowest tympanic temperature ranged from 17.7 to 19.2 degrees C. No permanent cerebral complications occurred in 10 patients. We believe that this adjunct technique offers excellent results in the surgical treatment of aneurysms involving the aortic arch.

Regional tissue blood flow and pH in the brain during deep hypothermic retrograde brain perfusion

Deep hypothermic retrograde brain perfusion is used to protect the brain during aortic arch operations. However, all experiments have failed to demonstrate retrograde blood flow in the brain tissue. We developed an experimental model of sagittal sinus and simultaneous superior vena cava perfusion. Brain tissue blood flow was mapped with colored microspheres during deep hypothermic retrograde brain perfusion in 9 dogs. Regional brain pH was mapped photometrically using neutral red as a pH-indicating dye after 90 min of retrograde brain perfusion in 28 dogs and after 60 min of circulatory arrest in 8 dogs. Cerebral surface blood flow was also measured during retrograde brain perfusion. They were analyzed as functions of driving pressure between sagittal sinus and aorta. Total brain blood flow (ml/min/100 g) was 1.4 +/- 1.3, 3.8 +/- 2.6, and 4.6 +/- 2.6 when the driving pressure was 15, 25, and 35 mmHg, respectively (P < 0.05, 15 mmHg vs 25 mmHg). Regional cerebral blood flow (ml/min/100 g) with a driving pressure of 25 mmHg was 12.1 +/- 9.4, 7.0 +/- 5.6, 4.4 +/- 2.8, and 2.2 +/- 1.4 in the frontal cortex, anterior, mid, and posterior cerebrum, respectively. Cerebral cortex pH was 6.86 +/- 0.23, 7.15 +/- 0.18, and 6.46 +/- 0.13 after 90 min of retrograde brain perfusion with driving pressure of less than 20 mmHg, after that of above 20 mmHg, and after 60 min of circulatory arrest, respectively. Brain tissue pH, blood flows measured with microspheres, and laser flowmetry were highest when driving pressure was between 25 and 35 mmHg. We conclude that retrograde brain perfusion may provide maximum brain protection with driving pressure of 25 to 35 mmHg.

Psychiatric complications of cardiac surgery postoperative delirium syndrome

Psychiatric disturbances due to cardiopulmonary bypass, especially postoperative delirium syndrome, are among the immediate complications of open-heart surgery. In a series of 32 male and 18 female patients the prevalence of such disorders was investigated and search was made for possible risk factors for their occurrence. Psychiatric, neurologic and electroencephalographic evaluation was made pre- and postoperatively, in addition to haemodynamic, echocardiographic, angiographic and regional cerebral blood flow studies. Nine of the 50 patients had significantly reduced perfusion of certain cerebral lobes in single photon emission computed tomography, and in six of them the psychiatric tests indicated postoperative delirium; three of these six also had moderate electroencephalographic changes. The cerebral hypoperfusion persisted on day 15 in four patients, while psychiatric tests were negative. The study showed possible risk factors to be patient age, long aortic cross-clamp time, high-dose inotropic support and excessive transfusion of blood or blood products.

Morphological investigation of the neuroprotective effects of graded hypothermia after diverse periods of global cerebral ischemia in gerbils

Hypothermia is known to be the most effective method to protect the neuronal damage induced by ischemia. In the present study, we investigated the histopathological consequences of hippocampal CA1 pyramidal neurons as well as the glial reactions in the hippocampus, after diverse periods of ischemic insult at graded intra-ischemic hypothermia ranging from 32 to 20 degrees C. Gerbils were exposed to forebrain ischemia by clamping the bilateral common carotid arteries for 5-120 min depending upon the temperatures. The morphological study was performed 7 days after ischemia or sham-operation. Histopathological evaluation of delayed neuronal death (DND) was performed by Cresyl violet (CV) staining and MAP2 immunoreactivity. Glial reactions were examined by GFAP immunostaining and isolectin B4 histochemistry, corresponding to astrocytes and microglia, respectively. The forebrain ischemia at 32 degrees C for 10 min and at 28 degrees C for 20 min did not induce DND in the CA1 region. However, the ischemia at 32 degrees C for 20 min and at 28 degrees C for 30 min caused extensive degeneration of CA1 pyramidal neurons as observed in normothermic ischemic animals. Under the condition of deep hypothermia, the ischemia for 60 min at 24 degrees C and for 120 min at 20 degrees C which were the longest durations of each temperature within the limitation of the animal survival following 7 days, induced no DND in CA1 pyramidal neurons. The reactive changes of astrocytes were observed not only in ischemic animals with DND, but also in ischemic animals without DND. Computer image analysis showed that the area fraction of GFAP-positive structures in the CA1 region was significantly increased in both ischemic cases with and without DND compared with each sham group. In contrast, the distribution of activated microglia was much more restricted to the CA1 region and they were always accompanied by DND at 7 days postischemia. The present results demonstrate the remarkable neuroprotective effect of deep hypothermia that has been widely used in cardiovascular surgeries as the cerebroprotective strategy during total circulatory cessation. The findings also suggest that even under the condition of hypothermia, glial reactions may play an important role in neuronal survival and death after ischemia.

Cerebral hemodynamics and metabolism during infant cardiac surgery. Mechanisms of injury and strategies for protection

There is an established link between congenital heart disease and acquired brain injury, which relates to the dependence of the nervous system on a consistent and responsive supply of oxygen and glucose. The advances in the field of infant cardiac surgery have presented new and different challenges to the arena of child neurology. This review provides an overview of the mechanisms of neurologic injury and cerebral hemodynamics and metabolism during cardiac surgery. This review discusses current and future strategies for the management of children with congenital heart disease.

Techniques for retrograde cerebral perfusion in the treatment of aortic lesions via left thoracotomy

Retrograde cerebral perfusion under deep hypothermic circulatory arrest is a simple and useful adjunct in aortic surgery and is performed by many surgeons in the treatment of aortic arch pathology. In recent years, this technique has been recommended in the surgery of distal arch and proximal descending aortic lesions through a left thoracotomy inclusion. The aim of the technique is to increase the right atrial pressure for retrograde cerebral perfusion. After cooling using femorofemoral bypass, circulatory arrest is initiated. The right atrial pressure is increased to 20 mmHg, and retrograde cerebral circulation results. In this article, five patients with distal aortic arch and proximal descending thoracic aortic lesions who were operated on by using this technique were evaluated. It is suggested that this technique can be used with a lateral thoracotomy approach that is suitable for procedures on a distal aortic arch and proximal descending aorta.

Perioperative electroencephalographic seizures in infants undergoing repair of complex congenital cardiac defects

Many infants with cardiac anomalies undergo repair early in life. Both commonly used support techniques, deep hypothermic circulatory arrest (DHCA) and low-flow cardiopulmonary bypass (LFB), may be associated with adverse neurological outcomes, including seizures. In a single center study, 171 infants undergoing correction for D-transposition of the great arteries were randomized to one of these support techniques. Incidence and onset times of EEG seizures during continuous EEG-video monitoring in the first 48 h postoperatively and clinical seizures in the first postoperative week were compared. EEG seizures were characterized by time, duration, and localization of onset. Incidence of EEG seizures (20%) was more than 3 times that of clinical seizures (6%). Most infants with EEG seizures had multiple seizures beginning between 13 and 36 h postoperatively. Durations ranged from 6 s to 980 min. Onset of EEG seizures occurred most commonly in frontal and central regions. Factors associated with EEG seizures included randomization to DHCA, longer duration of circulatory arrest, and diagnosis of VSD. In this study EEG seizures were common following this type of cardiac surgery, illustrating the importance of EEG monitoring in detecting seizures. This data adds insight into mechanisms of seizures in infants undergoing cardiac surgery.

Neurologic sequelae of deep hypothermic circulatory arrest in cardiac transplant infants

BACKGROUND

Considerable controversy exists experimentally and clinically regarding adverse neurologic effects that may follow deep hypothermic circulatory arrest. Moreover, the techniques of DHCA have never been standardized.

METHODS

We prospectively studies the neurodevelopmental outcome in 38 infants undergoing cardiac transplantation using DHCA before the age of 4 months (mean age, 37.0 days). Neurodevelopmental outcome in the 22 boys and 16 girls was tested up to 2.5 years after transplantation using Bayley scale of infant development. Bayley scores were compared with the rate of core cooling and the length of DHCA in all patients. Deep hypothermic circulatory arrest was accomplished using an asanguineous prime resulting in hematocrits of 5% +/- 5% and ionized Ca2+, 0.4 +/- 0.1 mmol/L. No surface precooling was used, but the head was packed in ice. Mean cooling time was 14.0 +/- 3.5 minutes, resulting in rectal temperatures of 18 degrees +/- 2.5 degrees C. Duration of DHCA ranged from 42 to 70 minutes (mean duration, 56.0 +/- 6.6 minutes).

RESULTS

Postoperatively, the mean Bayley psychomotor development index was 91 (range, 50 to 130) and mental development index was 88 (range, 50 to 130). No relationship was found between either the rate of cooling or the duration of DHCA and Bayley scores (r = 0.227 and r = 0.322, respectively).

CONCLUSIONS

These data suggest that neither the rate of cooling nor DHCA times between 42 and 70 minutes using profoundly low hematocrits and low ionized calcium levels has any measurable effect on neurologic outcome up to 2.5 years postoperatively. It is possible that adverse neurologic outcomes from DHCA reflect particular methods of achieving DHCA.

Cerebral perfusion and hypothermic circulatory arrest

Since DeBakey's replacement of an aortic arch aneurysm using cardiopulmonary bypass and individual perfusion of the brachiocephalic and carotid arteries, selective cerebral perfusion has been used as an effective method of cerebral protection. Although interest in this technique waned with the evolution of hypothermic circulatory arrest, complications arising from long and challenging aortic procedures have led to a renewed interest in perfusion of the cerebral circulation. During aortic arch surgery, antegrade and retrograde cerebral perfusion techniques have been used in an effort to prolong the "safe" duration during which conventional cardiopulmonary bypass flow to the brain is interrupted. Although the degree to which retrograde cerebral flow is able to perfuse cerebral tissue remains controversial, its use may afford protection through other mechanisms as well. This paper will review techniques, benefits, and limitations of antegrade and retrograde cerebral perfusion and their role in conjunction with hypothermic systemic circulatory arrest.

The relationship between intelligence and duration of circulatory arrest with deep hypothermia

A total of 114 children (51 with tetralogy of Fallot, 30 with transposition of the great arteries, and 33 with ventricular septal defect) who had these defects repaired with the use of deep hypothermia and circulatory arrest were assessed for intellectual and neuropsychologic function at an average of 9 to 10 years after the operation. Children with preoperative intellectual handicaps or postoperative neurologic complications were excluded. These children were compared with 54 who had atrial septal defects repaired with the use of cardiopulmonary bypass. The only significant difference in the neuropsychologic measures was that the bypass group had reaction times 2 to 3 seconds shorter on average than those of the hypothermic circulatory arrest group. Although there was no significant difference in intelligence quotient between the groups, a relationship between intelligence quotient and arrest time was found. Regression analysis of intelligence quotient against duration of arrest showed a significant decrease in intelligence quotient with increasing arrest time (slope = -0.36; p = 0.002; 95% confidence interval, -0.59, -0.14) indicating a decrease of 3 to 4 intelligence quotient points for each extra 10 minutes of arrest time. It appears that deep hypothermia with circulatory arrest for cardiac operations in children does not fully protect the brain, with a linear relationship existing between the amount of impairment and the duration of circulatory arrest.

Retrograde cerebral perfusion with hypothermic blood provides efficient protection of the brain: a neuropathological study

Retrograde cerebral perfusion is a method that is recently being used for protection of the brain during operations on the aortic arch. This method is useful but is said to provide a limited time for protecting the brain. We designed an experiment in dogs to investigate neuropathologically the effect of protecting the brain for 120 minutes under: (1) circulatory arrest (CA); (2) retrograde cerebral perfusion with moderately cooled blood (RCPMC); and (3) retrograde cerebral perfusion with deeply cooled blood (RCPDC). We calculated the number of the abnormal cells of 400 hippocampal neurons per dog light microscopically. The number was 199 +/- 23 (mean +/- 1 SD) in the CA group, 149 +/- 50 in the RCPMC group, and 72 +/- 33 in the RCPDC group. The difference between the CA group and the RCPMC group was not statistically significant (p < 0.05), but there was a significant difference between the RCPMC and RCPDC groups (p < 0.05). The degree of cerebral protection provided by retrograde cerebral perfusion for 120 minutes is not sufficient when using moderately cooled blood. If we use deeply cooled blood at a temperature of about 10 degrees C, we should obtain a sufficient degree of protection of the brain.

Developmental and neurologic status of children after heart surgery with hypothermic circulatory arrest or low-flow cardiopulmonary bypass

BACKGROUND

Deep hypothermia with either total circulatory arrest or low-flow cardiopulmonary bypass is used to support vital organs during heart surgery in infants. We compared the developmental and neurologic sequelae of these two strategies one year after surgery.

METHODS

Infants with D-transposition of the great arteries who underwent an arterial-switch operation were randomly assigned to a method of support consisting predominantly of circulatory arrest or a method consisting predominantly of low-flow bypass. Developmental and neurologic evaluations and magnetic resonance imaging (MRI) were performed at one year of age.

RESULTS

Of the 171 patients enrolled in the study, 155 were evaluated. After adjustment for the presence or absence of a ventricular septal defect, the infants assigned to circulatory arrest, as compared with those assigned to low-flow bypass, had a lower mean score on the Psychomotor Development Index of the Bayley Scales of Infant Development (a 6.5-point deficit, P = 0.01) and a higher proportion had scores < or = 80 (i.e., 2 SD or more below the population mean) (27 percent vs. 12 percent, P = 0.02). The score on the Psychomotor Development Index was inversely related to the duration of circulatory arrest (P = 0.02). The risk of neurologic abnormalities increased with the duration of circulatory arrest (P = 0.04). The method of support was not associated with the prevalence of abnormalities on MRI scans of the brain, scores on the Mental Development Index of the Bayley Scale, or scores on a test of visual-recognition memory. Perioperative electroencephalographic seizure activity was associated with lower scores on the Psychomotor Development Index (P = 0.002) and an increased likelihood of abnormalities on MRI scans of the brain (P < 0.001).

CONCLUSIONS

Heart surgery performed with circulatory arrest as the predominant support strategy is associated with a higher risk of delayed motor development and neurologic abnormalities at the age of one year than is surgery with low-flow bypass as the predominant support strategy.

Total arch graft replacement in patients with acute type A aortic dissection

Treatment of acute type A aortic dissection with emergency total aortic arch graft replacement remains controversial. Between December 1988 and July 1993, 30 patients with this fatal disease underwent graft replacement of both the ascending aorta and total aortic arch on an emergency basis. All operations were performed with the aid of extracorporeal circulation, blood cardioplegia, selective cerebral perfusion, and open distal anastomosis. The overall early mortality rate was 23.3% (7 patients), but that in patients with complications with shock and renal/mesenteric ischemia was 57% and 66.7%, respectively. On the other hand, the mortality rate in the 23 patients (77%) in whom neither of these two risk factors was present was low (8.7%). The overall 4-year survival rate was 66.5% +/- 8.7%, and that for patients without these two risk factors was 87.0% +/- 7.0%. The present data suggest that simultaneous total arch replacement may be justified in selected patients with acute type A aortic dissection.

Retrograde cerebral circulation for distal aortic arch surgery through a left thoracotomy

We have devised a simple hypothermic retrograde cerebral circulation technique for protecting the brain during aortic arch surgery. The central venous pressure is simply elevated (15 to 18 mmHg) while the aortic arch is open and the descending aorta occluded, causing oxygen-saturated venous blood from the lower half of the body, which is undergoing deep hypothermic (15 degrees C to 18 degrees C) perfusion, to circulate in the brain in a retrograde fashion, supplying it with oxygen. Twenty-six cases of distal aortic arch aneurysm treated using this method, through a left thoracotomy with femoral vein cannulation, were evaluated. Retrograde cerebral circulation time was 59.6 +/- 13.1 minutes (40 to 93 min). Retrograde flow was 43.9 +/- 13.0 (25 to 62) mL/min. Significant oxygen and apparent lactate extraction were noted in the brain. Early death resulted in 3 of the first 14 cases (21.4%) from embolism, and in 1 of the other 12 cases (8.3%) from massive bleeding and multiple organ failure. Only one late death occurred. No death was attributed to the method itself. This method, with its simplified operative procedure using a lateral thoracotomy, supplied oxygen to the brain and protected it during interruption of the cerebral circulation. Careful management of the atherosclerotic aorta is needed.

The use of somatosensory evoked potentials to determine the optimal degree of hypothermia during circulatory arrest

We sequentially recorded subcortical (P14) and cortical (N20) somatosensory evoked potentials (SEPs) in 32 patients undergoing deep hypothermic circulatory arrest (CA). Under normal hemodynamic conditions, hypothermia initially produced N20 disappearance at a mean nasopharyngeal temperature of 20.4 +/- 2.6 degrees C (range 14.5 to 26.1 degrees C) and P14 disappearance at a mean of 16.9 +/- 2.0 degrees C (range 12.4 to 20.2 degrees C). On rewarming, P14 reappeared at mean temperature of 19.3 +/- 4.0 degrees C (range 13.5 to 29.2 degrees C) and N20 at a mean of 21.1 +/- 4.1 degrees C (range 14.3 to 29.6 degrees C). The delay of SEP reappearance after restoration of blood flow correlated significantly with CA duration (r = 0.74 for P14, and r = 0.62 for N20; p < 0.01). Neurological recovery was uneventful in 23 patients; 5 patients presented with neurological sequelae (minor or transient in 4; no recovery from anesthesia and death after 48 hours in 1), and 4 patients died during operation. Twenty-three of 24 surviving patients in whom P14 disappearance was the criterion that hypothermia was deep enough to perform CA (duration: 17 to 94 min) had a normal neurological outcome. By contrast, all surviving patients in whom cortical SEPs disappeared at higher temperatures presented neurological sequelae. In conclusion, the neurophysiological monitoring of brain stem activity, as specifically provided by SEPs, enables determination of the optimal temperature for CA, and demonstrates superiority of SEP monitoring over the use of EEG.

Optimal perfusion pressure for experimental retrograde cerebral perfusion

We evaluated cerebral metabolism during retrograde cerebral perfusion (RCP) and circulatory arrest during profound hypothermia, and also investigated the effects of perfusion pressure on RCP. Twenty-four adult mongrel dogs were placed on cardiopulmonary bypass and cooled to a nasopharyngeal temperature of 20 degrees C. At this temperature, hypothermic circulatory arrest (HCA; n = 6), and RCP with a perfusion pressure of 10 mmHg (RCP10; n = 6), 20 mmHg (RCP20; n = 6), and 30 mmHg (RCP30; n = 6) were carried out for 60 minutes. RCP was performed with oxygenated blood via the bilateral maxillary veins, and the retrograde flow rate was regulated to maintain a mean perfusion pressure of 10, 20, or 30 mmHg in the external jugular vein. At 60 minutes of RCP, we measured nasopharyngeal temperature; regional cerebral blood flow (rCBF); cerebral oxygen consumption, carbon dioxide excretion, and excess lactate; cerebral tissue adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and energy charge; and cerebral tissue water content. In the RCP10 group, there was excess cerebral lactate, and ATP and energy charge were low. In the RCP30 group, the water content of cerebral tissue was significantly higher than in other groups. In the RCP20 group, temperature was maintained in a narrow range, oxygen consumption and carbon dioxide excretion could be observed, there was no excess lactate, and ATP and energy charge were significantly higher than in the HCA group. In conclusion, RCP can provide adequate metabolic support for the brain during circulatory arrest, and a perfusion pressure of 20 mmHg is most appropriate for RCP.

Cerebral metabolic effects of sequential periods of hypothermic circulatory arrest

During repair of congenital heart defects, extended periods of hypothermic circulatory arrest (CA) have been shown to cause short-term cerebral metabolic and flow abnormalities as well as long-term neuropsychologic dysfunction. Occasionally, a second period of CA is required during the same operative setting to revise a complicated repair. However, the metabolic effects of two consecutive periods of CA on the brain are unclear. In this study, we compared the recovery of cerebral metabolism after 60 minutes of CA with that after two sequential 30-minute periods of CA separated by a brief period of rewarming (30'SEQ). Fifteen neonatal piglets (2 to 3 kg) were placed on cardiopulmonary bypass at 100 mL.kg-1 x min-1 and cooled to 18 degrees C. Each animal then underwent either 60 minutes of uninterrupted cardiopulmonary bypass at 18 degrees C, 60 minutes of CA, or two 30-minute periods of CA separated by a brief period of rewarming. After these experimental periods, animals were rewarmed to 37 degrees C and weaned from cardiopulmonary bypass. Data were obtained before cardiopulmonary bypass and after cardiopulmonary bypass at 37 degrees C and included measurements of cerebral blood flow by xenon 133 clearance, arterial and sagittal sinus blood gases, and cerebral metabolism (mL O2.100 g-1 x min-1). Our results demonstrated that acute recovery of cerebral metabolism was significantly impaired after 60 minutes of CA and that recovery of cerebral metabolism after two sequential 30-minute periods of CA was significantly better than after 60 minutes of continuous CA.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the perioperative neurologic effects of hypothermic circulatory arrest versus low-flow cardiopulmonary bypass in infant heart surgery

BACKGROUND

Hypothermic circulatory arrest is a widely used support technique during heart surgery in infants, but its effects on neurologic outcome have been controversial. An alternative method, low-flow cardiopulmonary bypass, maintains continuous cerebral circulation but may increase exposure to known pump-related sources of brain injury, such as embolism or inadequate cerebral perfusion.

METHODS

We compared the incidence of perioperative brain injury after deep hypothermia and support consisting predominantly of total circulatory arrest with the incidence after deep hypothermia and support consisting predominantly of low-flow cardiopulmonary bypass in a randomized, single-center trial. The criteria for eligibility included a diagnosis of transposition of the great arteries with an intact ventricular septum or a ventricular septal defect and a planned arterial-switch operation before the age of three months.

RESULTS

Of 171 patients with D-transposition of the great arteries, 129 (66 of whom were assigned to circulatory arrest and 63 to low-flow bypass) had an intact ventricular septum, and 42 (21 assigned to circulatory arrest and 21 to low-flow bypass) had a ventricular septal defect. After adjustment for diagnosis, assignment to circulatory arrest as compared with low-flow bypass was associated with a higher risk of clinical seizures (odds ratio, 11.4; 95 percent confidence interval, 1.4 to 93.0), a tendency to a higher risk of ictal activity on continuous electroencephalographic (EEG) monitoring during the first 48 hours after surgery (odds ratio, 2.5; 95 percent confidence interval, 1.0 to 6.4), a longer recovery time to the first reappearance of EEG activity (only in the group with an intact ventricular septum, P < 0.001), and greater release of the brain isoenzyme of creatine kinase in the first 6 hours after surgery (P = 0.046). Analyses comparing durations of circulatory arrest produced results similar to those of analyses comparing treatments.

CONCLUSIONS

In heart surgery in infants, a strategy consisting predominantly of circulatory arrest is associated with greater central nervous system perturbation in the early postoperative period than a strategy consisting predominantly of low-flow cardiopulmonary bypass. Assessment of the effect of these findings on later outcomes awaits follow-up of this cohort.