Temporary neurological dysfunction after deep hypothermic circulatory arrest: A clinical marker of long-term functional deficit

Background. With increasing clinical experience, it has become clear that t wo distinct forms of neurological injury occur after operations on the thor acic aorta that require temporary exclusion of the cerebral circulation. Tr aditionally, evaluation of neurological outcome was limited to reporting th e incidence of postoperative stroke related to ischemic infarcts due to par ticulate embolization. More recently, the symptom complex defined as "tempo rary neurological dysfunction" (TND) was recognized as a functional manifes tation of subtle and presumably transient brain injury, but whether this ea rly postoperative syndrome is associated with long-term deficits of cogniti ve and intellectual functions has not been established. Methods. With Institution Review Board approval, 105 patients undergoing el ective thoracic aortic surgery were entered into a protocol involving neuro psychological evaluation with a battery of tests preoperatively, and 1 and 6 weeks postoperatively. Patients who could not be tested adequately or had documented strokes were eliminated from final analysis. Seventy-one patien ts completed the neuropsychological evaluation, which consisted of eight te sts consolidated into five domains: attention, cognitive speed, memory, exe cutive function, and fine motor function. Independent observers also determ ined whether temporary dysfunction was present, and graded its severity bas ed on a fixed but subjective clinical scale, ranging from simple disorienta tion and lethargy or confusion (grade 1-2) to prolonged extreme agitation o r psychotic behavior requiring treatment with psychotropic drugs (grade 3-5 ). Data were normalized to baseline values, and were analyzed using analysi s of variance, analysis of covariance (ANCOVA), and chi(2) as necessary. Results. A previous analysis had shown that patients who could not be teste d or had poor scores 1 week postoperatively were more likely to perform poo rly at 6 weeks (odds ratio 5.27, p < 0.01). in the current study, in order to determine the clinical relevance of TND, patients were analyzed retrospe ctively according to their performance in neuropsychological testing: patie nts with no change or a decline of less than 50% in tests of memory, motor function, and attention 1 week postoperatively (group 1, n = 49) were compa red with those with a negative change exceeding 50% in the same functions a t 1 week (group 2, n = 22). The overall incidence of TND was 28.1% (20/71). The incidence of TND in group 2 (14/22, 63%) was significantly higher than in group 1 (6/49, 12%; p = 0.0006). Similarly, the severity of TND las ass essed by clinical score > 2) was also significantly higher in group 2 (11/1 4) compared with group 1 (0/6; p = 0.006.). Conclusions. The incidence and severity of clinically apparent temporary ne urological dysfunction correlates significantly with poor performance on ne uropsychological tests I week postoperatively. Such poor performance predic ts continued deficits in memory and motor function at 6 weeks. Thus, TND ma y not be a benign self-limited condition as previously supposed, but rather a clinical marker for insidious but significant neurological injury associ ated with measurable long-term deficits in cerebral function. A concerted e ffort to reduce the incidence of this complication is therefore necessary. (C) 1999 by The Society of Thoracic Surgeons.