Subclinical changes in brain morphology following cardiac operations as reflected by computed tomographic scans of the brain

Neurological complications after pediatric cardiac surgery

Background

The number of pediatric patients who survive open-heart surgery has increased in recent years and the complications seen in this patient group continue to decrease with each technological advance, including new surgical and neuroprotective techniques and the improvement in surgeons' experience with this patient population. However, neurological complications, which are the most feared and difficult to manage, require long-term follow-up, and increase hospital costs remain a leading cause of mortality and morbidity in this cohort.

Results

We evaluated the neurological physical examination, cranial computed tomography (CT), and magnetic resonance (MRI) records of 162 pediatric patients with neurological symptoms lasting more than 24 h after undergoing heart surgery in our clinic between June 2012 and May 2020. The patients' ages ranged from 0 to 205 months, with a mean of 60.59 ± 46.44 months.Of the 3849 pediatric cardiac surgery patients we screened, 162 had neurological complications in the early period (the first 10 days after surgery). The incidence was calculated as 4.2%; 69 patients (42.6%) experienced seizures, 17 (10.5%) experienced confusion, 39 (24.1%) had stupor, and 37 (22.8%) had hemiparesis. Of the patients who developed neurological complications, 54 (33.3%) died. Patients with neurological complications were divided into 3 groups: strokes (n = 90), intracranial bleeding (n = 37), and no radiological results (n = 35). Thirty-four patients (37.8%) in the stroke group died, as did 15 (40%) in the bleeding group, and 5 (14.3%) in the no radiological results group.

Conclusions

Studies on neurological complications after pediatric heart surgery in the literature are currently insufficient. We think that this study will contribute to a more detailed discussion of the issue. Responses to neurological events and treatment in the pediatric group may differ compared to the adult age group. Primary prevention methods should be the main approach in combating neurological complications; their formation mechanisms should be carefully monitored and preventive treatment strategies should be developed.

Cerebral dysfunction after cardiopulmonary bypass: aetiology, manifestations and interventions

Central nervous system dysfunction following cardiac surgery remains a significant cause of morbidity and mortality, with the reported incidence of dysfunction varying widely between studies. Microemboli and global cerebral hypoperfusion are implicated as the major aetiologies of CNS impairment. Preoperative and intraoperative variables influencing the patient's risk of complications remain controversial. Based on a review of previous studies, this paper outlines the major causes and manifestations of CNS impairment as well as the intraoperative interventions currently advocated to improve the cerebral outcome of cardiac patients.

Frequency, predictors, and neurologic outcomes of vaso-occlusive strokes associated with cardiac surgery in children

OBJECTIVE

Our aim was to define the frequency, predictors, and outcomes of stroke associated with cardiac surgery in children with congenital heart disease.

METHODS

We performed a case-control study of children (term birth to 18 years) with congenital heart disease who underwent cardiac surgery at the Hospital for Sick Children between January 1, 1992, and March 1, 2001. Case subjects experienced stroke within 72 hours after cardiac surgery, and control subjects (2 for each case subjects) had cardiac surgery and no stroke. The frequency of arterial ischemic stroke/cerebral sinovenous thrombosis was calculated among children who underwent cardiac surgery during the study period. Predictors for stroke, including age, gender, simple versus complex procedure, reoperation, bypass duration, circulatory arrest, postoperative hematocrit level, and intraoperative activated clotting time, were tested. The presence of clinical and radiologically defined stroke was the main outcome. Neurologic outcomes were assessed in case subjects with the Pediatric Stroke Outcome Measure.

RESULTS

During the study period, 30 children with stroke (28 with arterial ischemic stroke and 2 with cerebral sinovenous thrombosis) were identified among 5526 children undergoing cardiac surgery. This yielded a risk for arterial ischemic stroke/cerebral sinovenous thrombosis of 5.4 strokes per 1000 children undergoing a cardiac operation. Univariate analysis revealed that older age at the time of the procedure, longer duration of cardiopulmonary bypass, number of days in the hospital postoperatively, and reoperation were associated with stroke. In multivariate analyses, only reoperation was associated with stroke.

CONCLUSIONS

The frequency of vaso-occlusive stroke in children with congenital heart disease undergoing cardiac surgery was 5.4 cases per 1000 children. Age, duration of bypass, and reoperation may be associated with stroke risk.

Therapeutic hypothermia

Therapeutic hypothermia, introduced more than 5 decades ago, remains an important neuroprotective factor in the surgery for the correction of congenital heart disease, in particular when intraoperative circulatory arrest is required. Hypothermia decreases cerebral metabolism and energy consumption and reduces the extent of degenerative processes such as the excitotoxic cascade, apoptotic and necrotic cell death, microglial activation, oxidative stress, and inflammation. Neurological outcome has become the focus of several studies in the recent years, and deep hypothermic circulatory arrest durations of more than 40 minutes are associated with increased mid- and long-term disability. Physiologic cerebral flow-metabolism coupling seems to be preserved with moderate and mild hypothermia, but cerebral blood flow autoregulation is probably altered after deep hypothermic circulatory arrest, suggesting disordered cerebral metabolism and oxygen use. Although evidence from animal studies suggests potential benefit from very low temperatures, postoperative development of choreoathetosis has been found to correlate with the degree of intraoperative hypothermia, recommending the use of central temperatures greater than 15 degrees C in the clinical practice. Cooling times longer than 20 minutes are needed to obtain homogeneous brain cooling and effective neuroprotection. Finally, there is evidence that the sites of temperature monitoring used in the clinical practice may underestimate brain temperature after cardiopulmonary bypass, with the risk of postoperative hyperthermic brain damage.

Investigation on the ability of an ultrasound bubble detector to deliver size measurements of gaseous bubbles in fluid lines by using a glass bead model

Detectors based on ultrasonic principles are today's state of the art devices to detect gaseous bubbles that may be present in extracorporeal circuits (ECC) for various reasons. Referring to theoretical considerations and other studies, it also seems possible to use this technology to measure the size of detected bubbles, thus offering the chance to evaluate their potential hazardous effect if introduced into a patient's circulation. Based on these considerations, a commercially available ultrasound bubble detector has been developed by Hatteland Instrumentering, Norway, to deliver bubble size measurements by means of supplementary software. This device consists of an ultrasound sensor that can be clamped onto the ECC tubing, and the necessary electronic equipment to amplify and rectify the received signals. It is supplemented by software that processes these signals and presents them as specific data. On the basis of our knowledge and experience with bubble detection by ultrasound technology, we believe it is particularly difficult to meet all the requirements for size measurements, especially if these are to be achieved by using a mathematical procedure rather than exact devices. Therefore, we tried to evaluate the quality of the offered bubble detector in measuring bubble sizes. After establishing a standardized test stand, including a roller pump and a temperature sensor, we performed several sets of experiments using the manufacturers software and a program specifically designed at our department for this purpose. The first set revealed that the manufacturer's recommended calibration material did not meet essential requirements as established by other authors. Having solved that problem, we could actually demonstrate that the ultrasonic field, as generated by the bubble detector, has been correctly calculated by the manufacturer. Simply, it is a field having the strongest reflecting region in the center, subsequently losing strength toward the ECC tubing's edge. The following set of experiments revealed that the supplementary software not only does not compensate for the ultrasonic field's inhomogeneity, but, furthermore, delivers results that are inappropriate to the applied calibration material. In the last set of experiments, we were able to demonstrate that the signals as recorded by the bubble detector heavily depend upon the circulating fluid's temperature, a fact that the manufacturer does not address. Therefore, it seems impossible to resolve all these sensor related problems by ever-increasing mathematical intervention. We believe it is more appropriate to develop a new kind of ultrasound device, free of these shortcomings. This seems to be particularly useful, because the problem of determining the size of gaseous bubbles in ECC is not yet solved.

Scanning electron microscopic analysis of arterial line filters used in cardiopulmonary bypass

The clinical value of arterial line filters is still a controversial issue. Proponents of arterial line filtration argue that filters remove particulate matter and undissolved gas from circulation while opponents argue the absence of conclusive clinical data. We conducted scanning electron microscope (SEM) studies of arterial line filters used clinically in the cardiopulmonary bypass circuits during adult cardiac surgery and analyzed the types and characteristics of materials entrapped in the arterial line filters. Twelve arterial line filters were obtained during routine hypothermic cardiopulmonary bypass in 12 adult cardiac patients. The arterial line filter was a screen type with a pore size of 40 microm (Baxter Health Care Corporation, Bentley Division, Irvine, CA, U.S.A. ). After opening the housing, the woven polyester strands were examined with SEM. All segments examined (120 segments, each 2.5 x 2. 5 cm) contained no embolic particles larger in their cross-sectional area than the pore size of the filter (40 microm). The origins of embolic particulates were mostly from environmental foreign bodies. This may suggest a possible need for more aggressive filtration of smaller particulates than is generally carried out at the present time.

Neurophysiologic monitoring and outcomes in cardiovascular surgery

The first step to make in improving neurologic outcome is to recognize and accept neurologic injury occurs in all patient groups undergoing CPB. Fortunately, that stage has now been passed. Accurate detection and documentation of the incidence of brain injury is the next progression. At the same time, the cause of the injury needs to be established. Since the introduction of CPB, numerous improvements and refinements have been achieved, making it the acceptable, everyday clinical tool that has enabled the development of cardiac surgery. Despite these improvements, CPB-related morbidity persists. The advent of new technologic advances drives the quest for new techniques. New protective strategies for many end organs, including the heart, kidney, and brain, are evolving. No organ system should be viewed in isolation; otherwise, organ-specific protective strategies may arise in conflict. A strategy that confers absolute myocardial protection would be ideal, but at what cost to the protection of the kidneys, intestines, and brain? A neuroprotective strategy would ideally eliminate brain injury and be beneficial for all organs. The only way to continue to make progress is by the scientific evaluation of new techniques. The use of appropriate monitoring and outcome measures is fundamental to this process.

The use of hypothermia: a role in the treatment of neonatal asphyxia?

Perinatal asphyxia remains one of the most devastating neurologic processes. Although the understanding of the pathophysiology after perinatal asphyxia is extensive, there are few therapeutic interventions available to prevent or even mitigate the devastating process that unfolds after injury. The search for a safe and efficacious therapy has prompted scientists and clinicians to consider various promising therapies. One such therapy is therapeutic hypothermia. On the basis of adult, pediatric, and animal research, there is increasing evidence to suggest that therapeutic hypothermia may be an effective intervention to lessen the secondary neuronal injury that ensues after a hypoxic-ischemic insult. In this article the historic and modern-day uses of therapeutic hypothermia are first reviewed. The pathophysiology of neonatal asphyxia is examined next, with emphasis on the changes that occur when therapeutic hypothermia is implemented. Potential side-effects of the therapy in the neonate and the debate over systemic vs selective hypothermia are discussed. Lastly, although hypothermia as a potential treatment modality for neonates with hypoxic-ischemic encephalopathy is supported by numerous studies, the need for well-designed multicenter trials with detailed patient entry criteria and therapeutic conditions is emphasized.

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 platelet in cardiopulmonary bypass

Platelets are the smallest of the blood cells and are known to be activated during cardiopulmonary bypass. They play a role in many associated complications. Both quantitative and qualitative platelet defects have been demonstrated, resulting in microvascular hemorrhage and thromboembolism. As their interactions with endothelium and other blood cells are unraveled, the important contribution they make toward the systemic inflammatory response to operation seen in cardiopulmonary bypass is increasingly evident. In this review, we consider platelet activation during cardiopulmonary bypass, the resultant clinical effects, and potential approaches to therapy and prevention.

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.

Intraoperative echocardiographic study of air embolism during cardiac operations

BACKGROUND

Central nervous system damage remains a feared complication after heart operations. Air embolism (AE) is one of several possible causes of central nervous system damage. In previous studies, intraoperative transesophageal echocardiography (ITEE) has been used to detect AE, but identification of the periods of risk and the origin of AE is lacking.

METHODS

Two groups of patients undergoing elective heart operations were studied with ITEE. Group I consisted of 15 patients undergoing true "open heart" operations, either aortic or mitral valve. Group II consisted of 15 patients undergoing coronary artery bypass grafting.

RESULTS

In group I (valve operation), ITEE detected AE in all patients, particularly in the period between the release of the aortic cross-clamp and the termination of cardiopulmonary bypass. Furthermore, 12 of the 15 patients had new episodes of AE up to 28 minutes after termination of cardiopulmonary bypass. In the majority of cases, ITEE clearly demonstrated that the air originated in the lung veins and was not air retained in the heart. In group II (coronary artery bypass grafting) episodes of AE were only seen in the period between cross-clamp removal and the termination of cardiopulmonary bypass, and only in half of the patients.

CONCLUSIONS

Careful standard cardiac deairing did not prevent AE caused by the delayed release of air trapped in the lung vessels. Routine use of ITEE is recommended to assess the thoroughness of deairing procedures. This will help eliminate AE or at least lead to an increased awareness of the problem of retained air. Minimizing AE during open heart operations should contribute to a reduction in central nervous system damage and improvement of intellectual function after heart operations.

A 31p-magnetic resonance study of antegrade and retrograde cerebral perfusion during aortic arch surgery in pigs

To evaluate the effect of hypothermic circulatory arrest on brain metabolism, we used 31P-magnetic resonance spectroscopy to monitor brain metabolites in pigs during 2 hours of ischemia and 1 hour of reperfusion. Twenty-eight pigs were divided into five groups. Anesthesia (n = 5) and hypothermic cardiopulmonary bypass groups (n = 5) served as controls. In the circulatory arrest (n = 6), antegrade perfusion (n = 6), and retrograde (n = 6) brain perfusion groups, the bypass flow rate was 60 to 100 ml.kg-1.min-1. In the antegrade group, the brain was perfused via the carotid arteries at a blood flow rate of 180 to 200 ml.min-1 during circulatory arrest at 15 degrees C. In the retrograde group, the brain was perfused through the superior vena cava at a flow rate of 300 to 500 ml.min-1 during circulatory arrest at 15 degrees C. The intracellular pH was 7.1 +/- 0.1 and 7.3 +/- 0.1 in the anesthesia and hypothermic cardiopulmonary bypass groups, respectively. In the circulatory arrest group, the intracellular pH decreased to 6.2 +/- 0.1 and did not recover to its initial value (7.0 +/- 0.1) during reperfusion (p < 0.05 compared with the value obtained from the control groups at the corresponding time). Inorganic phosphate did not return to its initial level during reperfusion. In three animals in this group, levels of high-energy phosphates, adenosine triphosphate and phosphocreatine, recovered partially but did not reach the levels observed before arrest. In the group receiving antegrade perfusion, cerebral metabolites and intracellular pH were unchanged throughout the protocol. During circulatory arrest in the retrograde perfusion group the intracellular pH decreased to 6.4 +/- 0.1 and recovered fully during reperfusion (7.1 +/- 0.1). High-energy phosphates also returned to their initial levels during reperfusion. These studies show that deep hypothermic circulatory arrest with antegrade brain perfusion provides the best brain protection of the options investigated.

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.

Long-term MRI changes in brain after pediatric open heart surgery

We performed magnetic resonance imaging (MRI) on the brain and neurologic examinations on 23 children after open heart surgery for congenital heart disease. Twenty children also had psychometric assessments. Examinations were performed at a mean age of 66 months (range, 26 to 180 months). Age at operation was less than 1 month in 43% and more than 6 months in 45%. Abnormal scans were found in 17 (74%) and showed diffuse findings consistent with hypoxic-ischemic encephalopathy, with or without areas of cortical infarction; focal cortical infarction alone; and (in one patient) callosal agenesis and abnormal neuronal migration. Normal IQ and neurologic examinations were found in all six of those who had a normal MRI, and five of six children with changes consistent with focal cortical infarction without diffuse change had a normal neurologic examination. Cerebral palsy and mental retardation was common in the group with diffuse abnormality (in eight of nine children), and this was more likely to occur in those who underwent prolonged (> 45 minutes) hypothermic circulatory arrest and operation during early infancy (P = .004). Focal cortical findings without diffuse changes were more likely in those who underwent open heart surgery without hypothermic circulatory arrest and were older than 6 months at operation, and these children were less likely to have frank neurodevelopmental sequelae. Thus, in our population, focal cortical lesions were common after open heart surgery, and, in addition, diffuse brain abnormality on MRI plus neurologic sequelae were common after prolonged hypothermic circulatory arrest.

West syndrome following deep hypothermic infant cardiac surgery

Postoperative seizures are among the more common complications of cardiac surgery in children. These seizures have traditionally been considered benign, transient phenomena with little, if any, prognostic significance. We report 4 infants with early postoperative seizures following cardiac surgery who later developed the previously unreported complication of West syndrome, with infantile spasms, hypsarrhythmia, and developmental delay. This group constitutes 6% of 67 infant spasms evaluated over a 5-year period at Boston Children's Hospital. The postoperative seizures in these 4 patients were more difficult than usual to control with antiepileptic therapy; otherwise no intra- or perioperative features distinguished these infants who later developed West syndrome from infants with apparently benign "postpump seizures."

Cerebral ultrasonography before and after cardiac surgery in infants

Cerebral ultrasonography was performed in 66 infants before and after open heart surgery in order to study the incidence of cerebral complications. The underlying cardiac malformations were ventricular septal defect (n = 28), transposition of the great arteries (n = 11), tetralogy of Fallot (n = 8), complete atrioventricular septal defect (n = 5), total anomalous pulmonary venous drainage (n = 3), truncus arteriosus communis (n = 2), and complex cardiac malformations (n = 9). In 60 of the 66 infants ultrasonography of the brain preoperatively was normal, 3 had minor structural abnormalities, and 3 had ventriculomegaly of various degrees. Postoperatively, 46 infants had a normal brain ultrasound scan; 6 had slight structural abnormalities; and 5 had slight symmetric or asymmetric widening of the ventricles. Five infants showed severe ventriculomegaly with cerebral atrophy, and in 4 patients there was intracerebral hemorrhage, associated in 2 cases with severe ventriculomegaly. On repeat examinations it was found that up to 4 weeks after the operation an initially normal cerebral ultrasound scan could convert to a pathologic one. Most of those children who showed significant deterioration on the cerebral ultrasound scan suffered from complex cardiac malformations or had severe problems during the postoperative period.

A 10-year experience with postpump chorea

Postpump chorea (PPC) is the development of choreoathetoid movements within 2 weeks following cardiopulmonary bypass. Over a 10-year period, 668 children underwent open cardiac surgery, of whom 8 (1.2%) developed PPC. Age at surgery ranged from 8 to 34 months. The onset of chorea was 3 to 12 days following surgery. Computed tomography and magnetic resonance imaging showed atrophy but no focal lesions. Cerebral positron emission tomography using [18F]fluorodeoxyglucose in a patient following 12 months of chorea showed patchy areas of decreased glucose metabolism. None of the patients were developmentally normal 22 to 130 months following surgery. Three patients have had transient and 5 have persistent chorea. Neurological deficits ranged from a mild learning disability to progressive hypotonia and obtundation ending in death. One of 4 patients who received haloperidol had a decrease in the severity of chorea. We compared PPC patients with 39 randomly selected controls. During surgery, affected patients spent significantly more time on pump and at temperatures under 36 degrees C, were cooled to lower temperatures than controls, and were more likely to have had a circulatory arrest. One patient developed chorea without a history of circulatory arrest. We conclude that (1) there is a strong association between PPC, deep hypothermia, and circulatory arrest, (2) absence of characteristic macroscopic changes suggests a biochemical or microembolic etiology in some cases, (3) chorea is frequently associated with developmental delay, and (4) the prognosis for complete resolution of chorea is guarded.

Partial brachiocephalic perfusion in aortic arch replacement

Eleven patients who underwent replacement of the aortic arch or adjacent areas for aneurysmal disease between 1989 and 1991, using hypothermic cardiopulmonary bypass at 20 degrees to 23 degrees C with partial brachiocephalic perfusion, were studied. Selective perfusion of the innominate artery was performed in all 11 patients through the right axillary artery, while partial brachiocephalic perfusion was carried out using a separate arterial roller pump with a perfusion flow rate of 10 ml/kg per min. Direct cannulation to the left common carotid and left subclavian artery was not performed in this method. There were 4 men and 7 women who ranged in age from 26 to 78 years, with a mean age of 56 years. The etiology of aneurysmal disease was aortic dissection in 10 patients, and aortitis syndrome in 1. The cardiopulmonary bypass time was 214.3 +/- 39.3 min, aortic cross-clamp time 131.5 +/- 33.4 min, and partial brachiocephalic perfusion time 57.6 +/- 15.1 min. There were three operative deaths (27.3%), the causes being multiple organ failure, acute peritonitis, and infection of the composite graft in the ascending aorta, in one patient each, respectively. However, there were no deaths related to the technique of partial brachiocephalic perfusion and no neurological complications were seen in this series. Thus, we believe that partial brachiocephalic perfusion under hypothermic cardiopulmonary bypass is safe and effective in surgery for aortic aneurysms involving the aortic arch.

Cerebral metabolism and circulatory arrest: effects of duration and strategies for protection

Hypothermic total circulatory arrest (CA) is commonly used to facilitate repair of complex congenital heart defects. However, the "safe" period of CA remains to be defined. Extended periods of hypothermic total circulatory arrest may impair cerebral metabolism and cause ischemic brain injury. This study defines the relationship between increasing durations of CA at 18 degrees C and cerebral metabolism, and examines the protective value of topical cooling of the head or continuous "trickle" flow (5 to 10 mL.kg-1.min-1). Thirty-three 1-week-old piglets were randomized to six experimental groups: control; 15, 30, or 60 minutes of CA; 60 minutes of CA with topical cooling of the head; and 60 minutes of trickle flow. Animals were placed on cardiopulmonary bypass (CPB) at 100 mL.kg-1.min-1 and cooled to 18 degrees C. After the experimental period of CA or trickle flow (or 60 minutes of CPB at normal flow for the control group), animals were rewarmed to 37 degrees C and weaned from CPB. Data were obtained before and immediately after CPB at 37 degrees C, and before and immediately after the experimental period at 18 degrees C. Parameters measured included cerebral blood flow by xenon 133 clearance, arterial and sagittal sinus blood gases, and cerebral metabolism. Hypothermic total circulatory arrest caused an impairment of cerebral metabolism that was directly proportional to CA duration (r2 = 0.73; p = 0.0001), and recovery of metabolic function after 60 minutes of CA improved more than 50% if the head was packed in ice.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral consequences of hypothermic circulatory arrest in adults

Despite widespread use of hypothermic circulatory arrest (HCA) in aneurysm surgery and for repair of congenital heart defects, there is continued concern about possible adverse cerebral sequelae. The search for ways to improve implementation of HCA has inspired retrospective clinical studies to try to identify risk factors for cerebral injury, and clinical and laboratory investigations to explore the physiology of HCA. At present, risk factors associated with less favorable cerebral outcome after HCA include: prolonged duration of HCA (usually greater than 60 min); advanced patient age; rapid cooling (less than 20 min); hyperglycemia either before HCA or during reperfusion; preoperative cyanosis or lack of adequate hemodilution; evidence of increased oxygen extraction before HCA or during reperfusion; and delayed reappearance of electroencephalogram (EEG) or marked EEG abnormality. Strategies advocated to increase safety of HCA include: pretreatment with barbiturates and steroids; use of alpha-stat pH regulation during cooling and rewarming; intraoperative monitoring of EEG; slow and adequate cooling, including packing of the head in ice; monitoring of jugular venous oxygen content; hemodilution; and avoidance of hyperglycemia. Current investigation focuses on delineating the relationship of cerebral blood flow (CBF) to cerebral oxygen consumption and glucose metabolism during cooling, HCA, rewarming, and later recovery, and identifying changes in acute intraoperative parameters, including the presence of intracerebral enzymes in cerebral spinal fluid, with cerebral outcome as assessed by neurological evaluation, quantitative EEG, and postmortem histology. Clinically, intraoperative monitoring of EEG and measurement of CBF by tracer washout or Doppler flows are contributing to better understanding of the physiology of HCA, and in the laboratory, nuclear magnetic resonance (NMR) spectroscopy has provided valuable insights into the kinetics of intracerebral energy metabolism. Promising strategies for the future include investigation of other pharmacological agents to increase cerebral protection, and use of "cerebroplegia" or intermittent perfusion between intervals of HCA to improve cerebral tolerance for longer durations of HCA.

Magnetic resonance imaging of the brain before and after open heart operations

Magnetic resonance imaging of the brain was performed in 29 adult male patients before and 1 week after elective coronary artery bypass grafting to study the cerebral effect of cardiopulmonary bypass. The mean age of the patients was 60 years (range, 45 to 69 years). During cardiopulmonary bypass, either a bubble oxygenator without an arterial line filter (n = 9), a bubble oxygenator with a depth adsorption filter (n = 10), or a flat-sheet membrane oxygenator without a filter (n = 10) was used. The mean bypass time was 88 minutes (standard deviation, 31 minutes) and did not differ significantly between the three groups. Preoperative magnetic resonance imaging revealed high signal intensity foci on T2-weighted images (white matter abnormalities) in 17 (59%; 95% confidence limits, 39% to 76%) of the 29 patients, all of which were nonspecific and of the common type considered to be related to aging, and all were unchanged at the postoperative examination. Preoperative and postoperative frontal horn indices, bicaudate diameters, and third ventricle widths did not differ significantly regardless of oxygenator type or whether or not an arterial line filter was used during cardiopulmonary bypass. Two patients (7%; 95% confidence limits, 1% to 23%), both receiving bubble oxygenation (1 without a filter and 1 with an arterial line filter) sustained a cerebral infarction during cardiopulmonary bypass.

Brain protection during circulatory arrest

Previous nuclear magnetic resonance studies in this laboratory have shown a beneficial biochemical effect of antegrade cerebroplegia (CP-A) during hypothermic circulatory arrest. This study compared CP-A with other methods of cerebral protection during hypothermic circulatory arrest to assess the clinical utility of this technique. Twenty-three sheep were divided into four groups: systemic hypothermia alone (SYST) and systemic hypothermia combined with external cranial cooling (EXTNL), retrograde cerebroplegia (CP-R), or CP-A. Cardiopulmonary bypass was started, and the sheep were cooled to 15 degrees C and subjected to 2 hours of circulatory arrest. Cardiopulmonary bypass was restarted, and the animals were rewarmed and weaned from cardiopulmonary bypass. Serial neurological examinations were performed and hourly scores assigned until the animals were extubated. Postanesthetic neurological scores improved in all groups throughout the 6-hour recovery period except the CP-R group. The improvement over time for these scores was similar for the EXTNL and CP-A groups and significantly better than for the SYST or CP-R groups (p = 0.004). The CP-A group had 5 of 7 animals with deficit-free survival despite the similarity in recovery of baseline brainstem function. We conclude that both antegrade infusion of cerebroplegia and external cranial cooling confer distinct cerebroprotective effects after a protracted period of hypothermic circulatory arrest when compared with the other methods studied.

Vanishing calcification of the brain in an infant after open heart surgery

Neurological complications after cardiac operations with the aid of cardiopulmonary bypass and hypothermia are well known. A 6 months-old child is described with severe neurological complications after cardiac surgery for Fallot's tetralogy. On the CT scan cortical calcification was seen to vanish. Such calcification has not been reported in similar patients. Possible causes are discussed but the precise pathophysiology of this phenomenon remains unclear.

Effect of intraoperative intervention on neurological outcome based on electroencephalographic monitoring during cardiopulmonary bypass

Neurological complications of cardiopulmonary bypass procedures are well documented. The present two-part study was undertaken to (1) determine if on-line computerized electroencephalographic changes correlated with neurological outcome and (2) compare neurological outcome with that of a second group of patients who received intraoperative interventions based on electroencephalographic data. Part 1 consisted of monitoring 50 patients. A power drop index was developed that correlated with new global neurological deficits. New global deficits occurred in 44% of the patients. In part 2, this information was used to design intervention criteria. Treatment protocols used previously accepted methods of increasing cerebral blood flow, ie, increasing pump flow, raising mean arterial pressure, and increasing CO2 content in the ventilator blend. Global neurological deficits were reduced to 5% in a group of 41 clinically similar patients (p less than 0.001). Cerebral perfusion pressures were similar in both groups. The single correlating factor was the power drop index as identified by computerized EEG. Our conclusion is that simple intervention guided by computerized EEG can reduce global neurological deficits in patients having cardiopulmonary bypass procedures.

Long-term cerebral outcome after open-heart surgery. A five-year neuropsychological follow-up study

A prospective 5 years' neuropsychological, neurological, cardiological and electroencephalographical follow-up study was carried out in 44 patients who had undergone open-heart surgery for valve replacement. A distinct interrelationship was found between the clinical outcome immediately after operation and the neuropsychological long-term course despite the rapid recovery of occasional clinical disorders related to operative procedures. In fact, the psychometric performance scores of those who did not develop clinical signs of cerebral dysfunction induced in operation showed a significant difference only years after operation. Similarly, the harmful effects of long perfusion time (extracorporeal circulation) in operation were reflected in the long-term neuropsychological performance. Some evidence seemed to suggest that the correction of the prolonged circulatory disorder might possibly afford real enhancement of higher cerebral functions. The long-term results not only emphasize the importance of a careful clinical evaluation but also emphasize the necessity of considering the subclinical level of events both before and after operation when assessing the overall outcome and cerebral safety of cardiac surgery patients.

Cerebral blood flow during cardiopulmonary bypass in man: effect of arterial filtration

Cerebral blood flow was recorded in 39 patients undergoing cardiac surgery by intraarterial injection of xenon 133. There were three subgroups of patients: 10 patients had a 20 micron arterial filter (Johnson) and 11 a 40 micron filter (Pall), and 18 had no arterial filtration. All patients had a 40 micron (Pall) filter in the coronary suction line. Significant changes in cerebral blood flow occurred during extracorporeal circulation (p less than 0.0001). For all patients cerebral blood flow increased from a resting prebypass level of 30 to 46 and 57 ml/100 g a minute during initial and stable hypothermic extracorporeal circulation respectively. Both measurements were obtained at 26 degrees C and the recordings were made on average 12 and 55 minutes after the extracorporeal circulation was started. During rewarming cerebral blood flow increased to 64, 53, 41, and 36 ml/g a minute at 31 degrees, 33 degrees, 35 degrees, and 37 degrees C respectively, and when measured four and 16 minutes on average after bypass it was 44 and 41 ml/100 g a minute. This general brain hyperperfusion was noticed in all patients with a high enough mean blood pressure to produce hyperaemia. Interposing 20 and 40 micron arterial filters reduced cerebral blood flow but did not prevent this hyperaemia. The cerebral autoregulation, which maintains a constant cerebral blood flow within wide limits of perfusion pressures, was not affected by arterial filtration. The lower limit of blood pressure at which a further reduction in blood pressure was followed by a reduction in cerebral blood flow was around 60 mm Hg in all three groups.

The protective effect of profound hypothermia on the canine central nervous system during one hour of circulatory arrest

Circulatory arrest during profound hypothermia is a safe technique of cardiac surgery when used in selected instances. Despite its proven safety, the degree of cerebral protection offered by this technique is still poorly defined. Ten dogs anesthetized with Pentothal (thiopental sodium) were surface cooled to 32 degrees C. They were placed on cardiopulmonary bypass, cooled to 13 degrees C (cerebral temperature), and then underwent one hour of circulatory arrest. At the end of the arrest period, the dogs were rewarmed, resuscitated, and successfully weaned from bypass. A control group of 6 dogs were subjected to the same protocol but without the one-hour period of circulatory arrest. There were no group differences in animal weight, duration of surface cooling, cardiopulmonary bypass, or rewarming, mean flow, or mean arterial pressure. After a 7-day observation period, the dogs were killed with rapid tissue fixation using formalin. No neurological deficits were noted in any of the dogs during the observation period. The fixed brains were examined by a neuropathologist. No gross or microscopic evidence of cerebral hypoxia was seen in any of the animals. We conclude that one hour of circulatory arrest under profoundly hypothermic temperatures produces no detectable neurological changes or histological evidence of cerebral hypoxia.

Five-year neurological and EEG outcome after open-heart surgery

A five-year neurological and EEG follow-up was carried on 55 patients who had undergone open-heart surgery for valve replacement in order to investigate the long-term results of the treatment. The five-year survival rate was 89%. The prevalence of permanent neurological abnormalities after operation was 9%. Transient ischaemic attacks occurred in five patients but no more severe cerebrovascular accidents were encountered. The rate of embolic events was 2.8 per 100 patient-years. Various subjective symptoms and complaints showed a highly beneficial outcome. Also the five-year EEG outcome was encouraging; the prevalence of abnormal EEG had fallen from the value before operation of 45% to 25%. The harmful influence of long perfusion time (extracorporeal circulation) during operation was found to be reflected in the long-term EEG outcome and, significantly, not only in the patients who had, but also in those who had not developed clinical abnormalities complicating the immediate course after operation. Although a valvular surgery patient faces a number of CNS problems before, during and after operation, the overall long-term outcome of successful surgery seems highly beneficial in neurological terms.

Clinical evaluation of the microporous hollow fiber oxygenator

This report concerns a clinical evaluation for a newly devised hollow fiber oxygenator, Capiox II. It functions on a one-pump system, and is simple to set up and operate. This equipment was used for 118 patients undergoing cardiac surgery at Tokyo University Hospital from February 1982 through February 1983. The gas transfer capacity proved to be satisfactory. The employment of an air-oxygen blender prevented overoxygenation, and reasonable levels of PaO2 and PaCO2 were demonstrated with a FiO2 0.7, V/Q ratio 0.7 at normothermia. The destruction of platelets was much less with the use of this oxygenator, as compared to findings with the BOS-10. Hemolysis by Capiox II appeared to be lower than that by BOS-10, but the difference was not statistically significant. Differences were distinct in the amount of microbubbles; strikingly, no bubble was evidenced in Capiox II by the ultrasound bubble detector, during general procedures. We conclude that Capiox II is of excellent clinical value, and should be used especially for infants as well as adult patients with possible long perfusions. The merits and demerits of this equipment are given attention.

Evidence suggestive of diffuse brain damage following cardiac operations

In 37 patients regional cerebral blood flow (rCBF) was measured by single photon emission computerised tomography (SPECT) after inhalation of xenon-133 before and within the first 10 days after open heart surgery for acquired or congenital heart disease. None of the patients had motor deficits postoperatively and no focal abnormalities were disclosed by the rCBF tomograms. However, rCBF was generally reduced and mean CBF fell from a normal value of 53.5 to 44.7 ml/100 g X min (p less than 0.001). Changes in rCBF occurred uniformly throughout the brain. The reduction in CBF correlated positively with increasing years (p less than 0.05), duration of extracorporeal circulation (p less than 0.05), and low mean arterial blood pressure during the bypass (p less than 0.02). It was generally more pronounced after valve replacement than after coronary bypass (p less than 0.16). In 11 patients investigated 1 year after surgery CBF remained slightly reduced, 50.5 ml/100 g X min (p less than 0.05). No CBF reduction occurred in a control group of 15 patients who underwent carotid endarterectomy or extracranial-intracranial shunt operations. The findings are consistent with the suggestion that the extracorporeal circulation causes early postoperative central nervous system dysfunction.

Acute cerebral dysfunction after open-heart surgery. A reaction-time study

A sensitive measure of subtle CNS dysfunction, the continuous reaction time (CRT), was used in 19 patients to quantify the immediate effects of open-heart surgery and extracorporeal circulation (ECC) on the CNS. The control group comprised 17 patients undergoing thoracic surgical procedures without ECC. The reaction time was significantly prolonged after surgery both in the ECC patients and in the controls. CRT was unrelated to the duration of anaesthesia in both groups, but in the ECC group deterioration of CRT showed positive correlation with (a) the duration of ECC, (b) the duration of perfusion pressure below 50 mmHg during ECC and (c) the PCO2 during ECC. These three factors may be of pathogenetic significance in the development of CNS dysfunction following open-heart surgery. The acute changes in reaction time resolved within a week of surgery, but on questioning two months later half of the ECC patients reported intellectual disturbance, primarily impairment of memory and lability of mood.