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B D Townes

Publications and source records attributed to B D Townes.

At least 19 recordsLinked to original sources
PubMed1992

Electroencephalography during surgery with cardiopulmonary bypass and hypothermia.

After more than 30 yr of use, electroencephalographic (EEG) monitoring during cardiopulmonary bypass has not gained wide clinical acceptance. To assess its utility to predict central nervous system injury, two-channel recordings were made from 78 patients undergoing cardiopulmonary bypass and anesthetized with fentanyl/diazepam/enflurane. The perfusion regimen included the use of high pump flow, a bubble oxygenator, and no arterial tubing filter. Target values were 28-32 degrees C for the minimum rectal temperature, 60-80 mmHg for mean arterial pressure, and 20-25% for hematocrit. Eight descriptors of the Fourier power spectra of the EEG were calculated off-line, and outcome comparisons were made with the results from neuropsychological tests. Among 58 patients yielding complete data of acceptable quality, a statistically significant reduction in total power was observed from prebypass to postbypass, accompanied by an increase in the fractional power in the theta and beta frequency bands and in the spectral edge frequency. The shifts in total and theta power were weakly associated with short-term but not with long-term changes in neuropsychological scores. Nearly 40% of the patients' EEGs were corrupted with electrical noise at some time during bypass. In 15 patients selected for having high-quality recordings and no neuropsychological deficit, an extensive statistical analysis failed to reveal any consistent variation in the EEG descriptors with hypothermia. Under the conditions studied, it appears that for other than gross signal dropout, the strong background variability in the EEG makes it have little value for detecting harbingers of brain injury.

Aged↗
PubMed1992

Neurologic syndrome in 25 workers from an aluminum smelting plant.

BACKGROUND: This article expands on an earlier series of three patients with a neurologic syndrome, who had all worked in an aluminum smelting plant. METHODS: Twenty-five symptomatic workers from the same plant were referred for a standardized evaluation, including completion of a health questionnaire, neurologic examination, and neuropsychologic evaluation. An exposure index was calculated for each worker based on level and duration of exposure in the potroom, where exposures were the greatest. This index was correlated with symptoms, signs, and neuropsychologic test scores. RESULTS: Twenty-two (88%) of the patients reported frequent loss of balance, and 21 (84%) reported memory loss. Neurologic examination revealed signs of incoordination in 21 (84%) of the patients. Neuropsychologic test results showed preservation in certain spheres of functioning, such as verbal IQ, with substantial impairment in others, particularly memory functioning. On memory tests, 70% to 75% showed mild or greater impairment. The majority (17 of 19 tested, or 89%) showed depression on the Minnesota Multiphasic Personality Inventory. The exposure index was significantly correlated with signs and symptoms of incoordination. CONCLUSIONS: This study and others in humans and animals support the existence of a syndrome characterized by incoordination, poor memory, impairment in abstract reasoning, and depression. Aluminum exposure in the potroom seems the most likely cause.

Adult↗
PubMed1992

Central nervous system manifestations in human immunodeficiency virus infection without AIDS.

To characterize neurological and neuropsychological findings associated with human immunodeficiency virus type-I (HIV) infection, 77 seropositive homosexual or bisexual males with no or minor symptoms of HIV were compared prospectively to 44 HIV seronegative men by observers blinded to serological status of the subjects. Neurological symptoms and examination findings were not significantly different between seropositives and seronegatives except for cranial nerve findings, predominantly mild hearing impairment. Mean performance scores for a 15-test neuropsychological battery were within an unimpaired range for both groups, although for five tests, mean scores were significantly poorer in seropositives. After adjustment for vocabulary score, and demographic and psychosocial variables, the mean score of seropositives was significantly worse only for the Benton Visual Retention Test. Magnetic resonance (MR) images of brain were abnormal in 14 (27%) of 52 seropositives and one of 10 seronegatives (value was not significant). HIV was isolated from cerebrospinal fluid (CSF) in 31 (61%) of 51 seropositives. The only clinical or laboratory difference between CSF culture positives and negatives was a higher CSF immunoglobulin synthesis rate in the former subjects (medians of 10.3 versus 0.1 mg/day; p = 0.03). An additional 13 seropositive subjects had immunologic evidence of central nervous system HIV infection, defined by a serum-to-CSF HIV antibody ratio of less than 5.5. Intracranial abnormalities on MR imaging were associated with CSF immunologic responses to HIV. Nervous system involvement occurred in the vast majority of men with early HIV infection, but clinically significant impairment was uncommon.

Adult↗
PubMed1990

Cognition and metacognition at extreme altitudes on Mount Everest.

The FACTRETRIEVAL2 test battery, which assesses both retrieval of general information from memory and metacognition about that retrieval, was administered to people before and after a recent expedition to Mount Everest and at extreme altitudes above 6,400 m (higher than any mountain in North America or Europe). The major findings were as follows: First, the same extreme altitudes already known to impair learning did not affect either accuracy or latency of retrieval, and this robustness of retrieval occurred for both recall and forced-choice recognition. Second, extreme altitude did affect metacognition: The climbers showed a decline in their feeling of knowing both while at extreme altitude and after returning to Kathmandu (i.e., both an effect and an aftereffect of extreme altitude). Third, extreme altitude had different effects than alcohol intoxication (previously assessed by Nelson. McSpadden, Fromme, & Marlatt, 1986). Alcohol intoxication affected retrieval without affecting metacognition, whereas extreme altitude affected metacognition without affecting retrieval; this different pattern for extreme altitude versus alcohol intoxication implies that (a) hypoxia does not always yield the same outcome as alcohol intoxication and (b) neither retrieval nor metacognition is strictly more sensitive than the other for detecting changes in independent variables.

Adult↗
PubMed1990

Psychosis following styrene exposure: a case report of neuropsychological sequelae.

A patient with a significant history of substance abuse was exposed to styrene and other solvents in the workplace. He became acutely psychotic, experiencing visual hallucinations. The psychosis was controlled with neuroleptic medications and avoidance of solvent exposure, but he continued to show significant deficits in visual-spatial and memory abilities. These deficits cleared with time away from the workplace. The case is of interest in terms of neuropsychological sequelae of solvent exposure and potential interaction of solvents with alcohol and recreational drugs.

Adult↗
PubMed1990

A randomized study of carbon dioxide management during hypothermic cardiopulmonary bypass.

Eighty-six patients undergoing coronary artery bypass graft (n = 63) or intracardiac (n = 23) surgery were randomly assigned with respect to the target value for PaCO2 during cardiopulmonary bypass. In 44 patients the target PaCO2 was 40 mmHg, measured at the standard electrode temperature of 37 degrees C, while in 42 patients the target PaCO2 was 40 mmHg, corrected to the patient's rectal temperature (lowest value reached: mean 30.1, SD 1.9 degrees C). Other salient features of bypass management include use of bubble oxygenators without arterial filtration, flows of 1.8-2.4 l.min-1.m-2, mean hematocrit of 23%, and mean arterial blood pressure of approximately 70 mmHg, achieved by infusion of phenylephrine or sodium nitroprusside. Neuropsychologic function was assessed with series of tests administered on the day prior to surgery, just before discharge from the hospital (mean 8.0, SD 5.8 days postoperatively, n = 82), and again 7 months later (mean 220.7, SD 54.4 days postoperatively, n = 75). The scores at 8 days showed wide variability and generalized impairment unrelated to the PaCO2 group or to hypotension during cardiopulmonary bypass. At 7 months no significant difference was observed in neuropsychologic performance between the PaCO2 groups. Regarding cardiac outcome, there were no significant differences between groups in the appearance of new Q-waves on the electrocardiogram, the postoperative creatine kinase-MB fraction, the need for inotropic or intraaortic balloon pump support, or the length of postoperative ventilation or intensive care unit stay. These findings support the hypothesis that CO2 management during cardiopulmonary bypass at moderate hypothermia has no clinically significant effect on either neurobehavioral or cardiac outcome.

Carbon Dioxide↗
PubMed1990

The relationship between the pediatric neurological examination and neuropsychological assessment measures for young children.

Children with some degree of neurological dysfunction have traditionally been assessed by means of pediatric neurological examinations and/or neuropsychological test batteries. The present study investigated the relationship between these two different assessment methods in a normal population of 129 kindergarten and second grade students. Results indicated that of the 396 correlations conducted for each grade, 18% of the kindergarten and 15% of the second grade sample correlations were significant at the .01 level. Given the relatively few positive correlations, and the fact that there were few consistent patterns within and across grade levels, it was concluded that these two assessment procedures measure different areas of functioning and constitute two separate components of a broad evaluation of the relationship between behavior and the adequacy of brain functions.

Age Factors↗
PubMed1989

The cost to the central nervous system of climbing to extremely high altitude.

To assess the possibility that climbing to extremely high altitude may result in hypoxic injury to the brain, we performed neuropsychological and physiologic testing on 35 mountaineers before and 1 to 30 days after ascent to altitudes between 5488 and 8848 m, and on 6 subjects before and after simulation in an altitude chamber of a 40-day ascent to 8848 m. Neuropsychological testing revealed a decline in visual long-term memory after ascent as compared with before; of 14 visual items of information on the Wechsler Memory Scale, fewer were recalled after ascent by both the simulated-ascent group (a mean [+/- SD] of 10.14 +/- 1.68 items before, as compared with 7.00 +/- 3.35 items after; P less than 0.05) and the mountaineers (12.33 +/- 1.96 as compared with 11.36 +/- 1.88; P less than 0.05). Verbal long-term memory was also affected, but only in the simulated-ascent group; of a total of 10 words, an average of 8.14 +/- 1.86 were recalled before simulated ascent, but only 6.83 +/- 1.47 afterward (P less than 0.05). On the aphasia screening test, on which normal persons make an average of less than one error in verbal expression, the mountaineers made twice as many aphasic errors after ascent (1.03 +/- 1.10) as before (0.52 +/- 0.80; P less than 0.05). A higher ventilatory response to hypoxia correlated with a reduction in verbal learning (r = -0.88, P less than 0.05) and with poor long-term verbal memory (r = -0.99, P less than 0.01) after ascent. An increase in the number of aphasic errors on the aphasia screening test also correlated with a higher ventilatory response to hypoxia in both the simulated-ascent group (r = 0.94, P less than 0.01) and a subgroup of 11 mountaineers (r = 0.59, P less than 0.05). We conclude that persons with a more vigorous ventilatory response to hypoxia have more residual neurobehavioral impairment after returning to lower elevations. This finding may be explained by poorer oxygenation of the brain despite greater ventilation, perhaps because of a decrease in cerebral blood flow caused by hypocapnia that more than offsets the increase in arterial oxygen saturation.

Adult↗
PubMed1989

Diagnosis of attention deficit disorder with hyperactivity in Chinese boys.

Parental and teacher ratings of adjustment on the Achenbach Child Behavior Checklist and Teacher Rating Form were obtained on 39 subjects diagnosed as having attention deficit disorder with hyperactivity (ADDH), 31 subjects with ADDH plus learning disability (ADDH-LD), and 29 controls. Subjects were all males between the ages of 9 and 11 years and resided in Changsha, People's Republic of China. Significant group differences were found between the two clinical groups and the control group. Ratings by parents and teachers of the ADDH and ADDH-LD groups indicated more behavior problems and poorer social adjustment than controls. ADDH and ADDH-LD groups were not significantly different from one another except on ratings of school and learning problems.

Attention Deficit Disorder with Hyperactivity↗
PubMed1989

Neurobehavioral outcomes in cardiac operations. A prospective controlled study.

To assess the severity and duration of new organic brain dysfunction after cardiac operations, we used an extensive battery of neuropsychologic tests to evaluate 65 patients undergoing coronary artery bypass grafting and 25 patients undergoing intracardiac operations with cardiopulmonary bypass. Patients were tested the day before the operation, before discharge from the hospital, and approximately 7 months later. Compared to 47 nonsurgical control subjects tested at comparable time intervals, surgical subjects showed generalized impairment of neuropsychologic abilities near the time of discharge from the hospital. At follow-up testing, there was no evidence of residual impairment among the surgically treated patients as a whole. In fact, they showed greater improvement compared to initial test scores than did control subjects. However, performance of 10 patients (11%) declined on half of the neuropsychologic variables between preoperative and follow-up testing. Neurobehavioral outcome was not related to the type of operation (coronary bypass versus intracardiac), to factors of cardiopulmonary bypass (duration, aortic occlusion time, hypotension, arterial carbon dioxide tension, minimum hematocrit value, minimum temperature). The only predictor of negative outcome was advanced age. We conclude that, although neurobehavioral impairment is common during hospitalization after cardiac operations, the prognosis for eventual full recovery is favorable, although less so among the elderly.

Anxiety↗
PubMed1988

Neurobehavioral and psychosocial functioning of women exposed to high altitude in mountaineering.

The effects of chronic hypoxemia upon cognition and behavior were studied in women exposed to high altitude in mountaineering. Neuropsychological tests and psychosocial and physiological questionnaires were given to eight women before, during, and immediately after a Himalayan climb to 20,500 feet. Cognitive functioning remained relatively intact with only two significant decrements, complex abstract reasoning and word-finding ability. Significant changes were found on all psychosocial and physiological questionnaires. Feelings of acceptance of others and anxiety declined significantly. Physical symptoms were greatest during the first five days of ascent. Subjects' self-ratings of mental functioning were significantly better after the expedition than either before or during the climb. Self-assessments were correlated with emotions and physical symptoms, not with actual performances on the test battery. It is suggested that complex cognitive tasks and psychosocial functioning be studied in more detail as these were more influenced by exposure to high altitude in mountaineering.

Adult↗
PubMed1988

Test-retest reliability of the Reitan-Indiana Neuropsychological Test Battery for Children Aged 5 Through 8.

The present study attempted to assess the test-retest reliability of the Reitan-Indiana Neuropsychological Test Battery for Children aged 5 through 8 and to establish the magnitude of practice effects for a normal sample of school aged children. The sample population included 191 kindergarten and 193 second grade students who were administered the entire Reitan-Indiana Battery during the first year of the study and again at one year follow-up. Correlation analyses of random half samples of the population revealed 35 of the 39 test indices measured were stable for at least one of the half samples for the younger (kindergarten-first grade) sample with the same being true for 31 of the 39 variables assessed for the older (second-third grade) sample.

Child↗
PubMed1987

Relationships between IQ and neuropsychological measures in neuropsychiatric populations: within-laboratory and cross-cultural replications using WAIS and WAIS-R.

Several studies have reported positive correlations between measures of intelligence (a quasi-subject variable) and level of performance on neuropsychological tests; few, however, have presented test results by IQ grouping, which could be useful for comparative purposes. The present study examined the relationships of WAIS and WAIS-R Full Scale IQ to performance on a neuropsychological battery consisting of the Halstead-Reitan Battery (HRB), the Wide Range Achievement Test (WRAT), and the Wechsler Memory Scale (WMS). Four mixed neuropsychiatric samples provided cross-cultural and within-laboratory replications, two tested with WAIS and two with WAIS-R. Means and standard deviations for each measure were presented by five IQ levels within each sample. IQ was strongly related to scores on problem-solving tasks, auditory and linguistic measures, memory tasks, academic achievement levels, and tactual imperceptions, while motor functioning and sensory suppressions were less strongly related to IQ. IQ level was related to educational level in all samples. Correlations of years of education with dependent variables in the two WAIS-R samples were strong and replicable for WRAT scores, verbal memory measures, linguistic errors on the Aphasia Screening Test, and finger-tapping speeds but not for other HRB measures. Finally, IQ-HRB relationships were compared to those reported for other populations.

Achievement↗
PubMed1987

The Luria-Nebraska and Halstead-Reitan Neuropsychological Test batteries: a cross-cultural study in English and Arabic.

In the present study, the Luria-Nebraska and the Halstead-Reitan Neuropsychological Test batteries were administered to 112 male and female Arabic and English speaking Egyptians enrolled at the American University in Cairo. The aims of the study were to establish normative data, test the effects of language and order of administration upon performance, and examine practice effects and test-retest reliability of the two batteries. Only minimal differences were found between the Arabic and the English administrations. Results revealed strong test-retest reliability coefficients for the HRB and moderate ones for the LNNB. Practice effects were detected on six LNNB scales as well as on the HRB complex problem solving tests (Category and Tactual Performance Test). No other effects were detected. Thus, the initial performance on one battery did not interfere with nor enhance performance on the other battery.

Adolescent↗
PubMed1986

Neuropsychological changes in a young, healthy population after controlled hypotensive anesthesia.

We investigated the effect of controlled hypotension during halothane anesthesia on brain functions as measured by neuropsychological tests. Anesthesia in 17 patients included controlled hypotension, whereas in another 27 patients hypotension was not induced during surgery for correction of facial abnormalities. Intraoperative EEG recording showed no significant changes in EEG power during the induction of hypotension. Hypotensive anesthesia was not associated with greater postoperative impairment than normotensive anesthesia. Both groups did show short-term postoperative impairment of memory and learning. For at least the first 24 hrs after administration of a general anesthetic agent such as halothane, there is interference with consolidation of memory. This impairment was not apparent in follow-up examinations 6 months later.

Adult↗
PubMed1986

Hemodilution of polycythemic mountaineers: effects on exercise and mental function.

We studied the effects of acute, isovolemic hemodilution on the exercise ability and mental function of four polycythemic mountain climbers (mean hematocrit 58 +/- 1.25%) during the American Medical Research Expedition to Mt. Everest (AMREE). The subjects were studied at 5400 m (PB = 400 mm Hg). Approximately 15% of their blood volume was removed and replaced with an equal volume of 5% human albumin solution. Final hematocrits were 50.5 +/- 1.5%. Before and after hemodilution, the subjects performed psychological and exercise tests. Maximum work level, oxygen uptake, minute ventilation, and blood oxygen saturation did not change. After hemodilution, heart rate increased slightly at all work levels, and there was a small but significant improvement on the psychological tests. It is concluded that this degree of hemodilution was well tolerated and that a hematocrit of greater than 50% conferred no advantage for exercise and may have impaired cerebral function. Although, in these circumstances, isovolemic hemodilution improved cerebration, we feel that this potentially hazardous maneuver is rarely indicated.

Adult↗