Relationship between post-cardiotomy delirium, clinical neurological changes, and EEG abnormalities

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

For half a century, it has been known that some patients experience neurocognitive dysfunction after cardiac surgery; however, defining its incidence, course, and causes remains challenging and controversial. Various terms have been used to describe neurocognitive dysfunction at different times after cardiac surgery, ranging from "postoperative delirium" to "postoperative cognitive dysfunction or decline." Delirium is a clinical diagnosis included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Postoperative cognitive dysfunction is not included in the DSM-5 and has been heterogeneously defined, though a recent international nomenclature effort has proposed standardized definitions for it. Here, the authors discuss pathophysiologic mechanisms that may underlie these complications, review the literature on methods to prevent them, and discuss novel approaches to understand their etiology that may lead to novel treatment strategies. Future studies should measure both delirium and postoperative cognitive dysfunction to help clarify the relationship between these important postoperative complications.

Electroencephalographic changes after pediatric cardiac surgery with cardiopulmonary bypass: is slow wave activity unfavorable?

Pediatric cardiac surgery with cardiopulmonary bypass (CPB) is frequently associated with neurologic deficits. We describe the postoperative EEG changes, assess their possible causes, and evaluate their relevance to neurologic outcome. Thirty-one children and five neonates with congenital heart disease were included. EEG recording started after intubation and continued until 22-96 h after CPB. In addition to conventional analysis, spectral analysis was performed for occipital and frontal electrodes, and differences between pre- and postoperative delta power (delta-deltaP) were calculated. Maximum values of occipital delta-deltaP that occurred within 48 h after CPB were correlated with clinical variables and with perioperative markers of oxidative stress and inflammation. Occipital delta-deltaP correlated with frontal delta-deltaP, and maximum delta-deltaP correlated with conventional rating. Distinct rise of deltaP was detected in 18 of 21 children without any acute or long-term neurologic deficits but only in five of 10 children with temporary or permanent neurologic deficits. Furthermore, maximally registered delta-deltaP was inversely associated with duration of CPB and postoperative ventilation. Maximal delta-deltaP was also inversely associated with the loss of plasma ascorbate (as an index of oxidative stress) and plasma levels of IL-6 and IL-8. Slow wave activity frequently occurs within 48 h after CPB. However, our data do not support the notion that EEG slowing is associated with adverse neurologic outcome. This is supported by the fact that EEG slowing was associated with less oxido-inflammatory stress.

Postcardiotomy delirium: an overview

Any one of a number of psychologic patterns may appear cardiotomy: (1) Some patients may be elated and confident after awakening from anesthesis and have no severe changes of affect or neurologic deficit. Denial seems to be for them an adequate defense against anxiety. (2) Others are disoriented and manifest neurologic disturbance immediately after awakening, without a lucid interval. The sensorium begins to clear five days after surgery. (3) Some patients go into delirium after being lucid for as long as a week and have hallucinations, illusions, and motor excitation for a few days-or over several weeks. Pathologic brain changes that are apparently anatomical correlates of neurologic deficits in delirium include anoxic lesions of the hippocampus, and infarcted foci. Physiologic factors that contribute to this reaction include: long periods of extracorporeal circulation, arterial hypotension during surgery, emboli, and low postoperative cardiac output. Age, and the type and severity of heart impairment are also factors. Psychologic factors to be taken into account include preexisting psychopathology and the failure of denial under the stress of physical symptoms or hospitalization. Delirium is fostered by sensory overload (or deprivation) in the recovery room and intensive care unit, and by staff tension. Modification of the intensive care unit environment, the administration of antipsychotic drugs, and metabolic correctives are recommended. Preoperative psychologic evaluation, with therapy as needed, preliminary familiarization with perioperative procedures, as well as collaboration between psychiatrist and surgeon, can do much to prevent post-cardiotomy delirium.

Delirium after cardiac surgery: a critical review

Numerous articles have been published investigating the incidence of and risk factors for delirium after cardiac surgery. Smith and Dimsdale reviewed the literature on postcardiotomy delirium in 1987 using a meta-analysis of 44 research studies. However, doubts about their methods and results caused the authors to re-examine the literature using these 44 references as well as computerized literature searches to gather research and review papers from medical journals. Delirium after cardiac surgery appeared to be ill-defined in most of these studies. The methods and instruments used to assess delirium proved to be very different, and the patient samples were rather heterogeneous. Therefore, in most cases, the results are not comparable. Only a small number of the studies that were examined fit the criteria for statistical meta-analysis. On the basis of our analysis, a tentative conclusion may be drawn that the incidence of postcardiotomy delirium has declined slightly and that no strong risk factors have yet been identified.

A critique of instruments and methods to detect, diagnose, and rate delirium

This document reviews existing instruments for evaluation of delirium. Instruments have been grouped into four categories: tests that screen for cognitive impairment, delirium diagnostic instruments, delirium-specific numerical rating scales, and laboratory and paraclinical exams. Analysis of instruments was based on comparison of their psychometric properties as well as subjective judgment. Guidelines are suggested for choosing the appropriate instrument according to the type of clinical evaluation or delirium research envisaged. Important factors in choosing an instrument, besides the appropriateness of its psychometric characteristics, include administration time constraints, level of rater expertise, and patient capabilities. By familiarizing investigators with the variety of evaluation instruments available, this work should permit more appropriate instrument selection in future studies on delirium.

Quantitative EEG before and after open heart surgery in children. A significant decrease in the beta and alpha 2 bands postoperatively

Quantitative EEGs of 30 patients undergoing open heart surgery were investigated before, 6 days, 11 days and 44 days after operation. The study was conducted in order to investigate whether quantitative EEGs can show postoperative changes in children after open heart surgery. In 28 children, no new neurological signs of cerebral involvement were seen postoperatively. The most striking feature in these children was a significant decrease in the beta and the alpha 2 bands 6 and 11 days postoperatively. The pattern in the delta band was dominated by an increase 6 days postoperatively. Except for a slight decrease in alpha 2 waves, all variables were restored to preoperative values at 44 days after the operation. We found a significant decrease in plasma sodium and chloride after surgery but children with no or slight declines (1-3 mmol/l) also showed increased slow activity postoperatively. Therefore we conclude that an organic brain syndrome, although usually mild and transient, is a general phenomenon after open heart surgery.

Pupillary signs during cardiac surgery. Their use in the prediction of major cerebral deficit following cardiopulmonary bypass

Pupil sizes and reactions to light were studied in 100 patients who had cardiopulmonary bypass. Behaviour of the pupils was observed at six stages during the operation. Most patients (71) had pupils of equal size and similar reaction to light at all times. Twenty-three patients developed unequal pupils at some stage, while six had equal pupils throughout but exhibited differing reaction to light. Major cerebral deficit was significantly more common after operation in patients who developed inequality in pupil size than those who did not (p less than 0.05). No relationship was seen between dissimilar pupil reaction to light and the development of neurological complications. The clinical estimation of pupil size may help to identify those patients who may exhibit postoperative major neurological 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.

Clinical and prognostic correlates of EEG in open-heart surgery patients

Sixty-five patients undergoing cardiac valve replacement were followed for one year by electroencephalography (EEG). Occurrence of delta or sharp wave disturbances of low frequency of dominant activity before operation was found to have prognostic significance. The degree of EEG change after operation correlated with clinical signs of cerebral involvement, and predicted the later course.

Detection of entrapped intracardiac air with intraoperative echocardiography

Embolization of entrapped intracardiac air represents a significant risk to the patient undergoing open heart surgery. To date, there have been no menas available to ensure that the heart is free of air prior to restoration of the circulation. To assess whether M mode echocardiography can accurately detect intracardiac air, we studied 10 dogs during cardiopulmonary bypass. Randomly, air was or was not injected into the left ventricular cavity of the fibrillating heart. Intracardiac air could be recognized by the presence of a stippled granular pattern, or a loss of the discrete linear echoes or decreased far field echoes, or any combination of these three. In all, 131 random observations were made. When 1.0 cc of air was injected, sensitivity and specificity were both 100 percent, but when 0.2 cc was injected, sensitivity and specificity decreased to 86 and 58 percent, respectively. thus, M mode echocardiography appears to provide a sensitive and specific tool for detecting intracardiac air.

Cellular aggregation and destruction during blood circulation and oxygenation

Platelet and leucocyte aggregation and severe haemolysis may occur in blood during the preparation of an extracorporeal circuit for open-heart surgery. Experiments with dog blood showed that both processes result from bubble oxygenation but not from circulation of diluted blood and that they appear to be inhibited by the presence of acid citrate dextrose and heparin, or citrate phosphate dextrose and heparin, but not by heparin alone.

Prognostic value of electroencephalography in cardiac surgery

One hundred seventeen patients undergoing cardiac operations over a two-year period were studied. Electroencephalograms were recorded preoperatively, in the recovery room (up to 12 hours following operation), 24 hours later, and further as required. Operative and anesthesia data were correlated with EEG findings. All patients had normal EEGs preoperatively. This unusual occurrence may largely reflect the absence of congenital heart disease and the small number of valvular lesions in our patients. Prognosis was not significantly influenced by age. Bypass time appeared directly related to outcome by group but not individually. Hypotension prior to pumping occurred most often and mean blood loss was greatest in the patients who had abnormal EEGs in the recovery room with progressively worsening patterns until death. In the recovery room many patients were awake, while others were either drowsy, lethargic, or asleep. Some were comatose. The level of consciousness was not as prognostic as was the EEG. The pattern of EEGs in the first few postoperative days is more important than any single record by itself. All those who showed progressive deterioration in the first two or three days died shortly thereafter.

Hypotension-induced changes in cerebral function during cardiac surgery

In a series of 75 patients undergoing cardiac operations with the assistance of cardiopulmonary bypass (CPB), 15 patients were subjected to relatively large hypotensive stresses during CPB as measured by the depth and duration of the fall in cerebral perfusion pressure. Of these 15 patients, eight manifested cerebral dysfunction postoperatively ranging from temporary exacerbation of pre-existing focal neurological deficits to irreversible coma. In each of these eight cases, EEG disturbances which first appeared at the time of hypotensive episodes during CPB persisted postoperatively and correlated with the nature and evolution of the clinical deficit. In two of the patients who did not regain consciousness postoperatively, neuropathological studies revealed bilateral laminar cortical necrosis, primarily involving cerebral cortex in one case and cerebellar cortex in the other, with accentuation in arterial border zones. Of seven other patients who suffered comparable exposures to hypotension during CPB, none evidenced cerebral dysfunction postoperatively. The most important determinants of this selective vulnerability to low extracorporeal perfusion pressure appeared to be the "reperfusion" pressure established after the hypotensive episode, postoperative blood pressure and cardiac output, and brain temperature at the time of the hypotension. Advanced age and history of cerebrovascular insufficiency were the greatest risk factors among patient variables.

[Neurological complications of heart surgery. Review of their pathogenesis and bases for their treatment]

São relatadas as complicações neurológicas assinaladas em 320 pacientes submetidos a cirurgias cardíacas, com uma incidência de 7,8%. As etiologias mais comuns encontradas foram a embolia aérea (4,0%) e isquemia cerebral após hipotensão sistêmica (2,4%). Os autores analisam a patogenia das complicações cerebrais e tentam correlacioná-las com o fluxo sangüíneo cerebral, com o metabolismo cerebral e com a dinâmica dos pequenos vasos cerebrais. Uma revisão a respeito dos métodos para tratamento da isquemia cerebral é apresentada.

Neurological damage related to open-heart surgery. A clinical survey

A survey has been carried out on all cases submitted to open-heart surgery at one hospital during 1970 to determine which operative features were associated with the occurrence of neurological damage.

Four hundred and seventeen subjects survived the operative period. Neurological dysfunction, defined as impairment of consciousness, voluntary movement or vision, apparent within three days of operation, was noted in 80 patients (19·2%). Twenty-one of these 80 patients died in the postoperative period, neurological damage contributing to the fatal outcome in 11 cases. The remaining 59 patients survived to leave hospital but 17 were left with some residual neurological disability.

A number of features were found to be positively correlated with the development of neurological damage when considered alone, but multiple regression analysis revealed that only three factors were significantly associated, independent of all other variables. These factors were age, duration of perfusion, and a history of previous neurological disorder.

The use of a Temptrol oxygenator was associated with a lower incidence of neurological dysfunction to a degree which was probably significant (p<0·02). The small number of patients perfused with the Temptrol oxygenator (30 cases) reduces the clinical importance of this finding.