PubMed Health⌕ Search

Biomedical subjects

B A Blunt

Publications and source records attributed to B A Blunt.

16 recordsLinked to original sources
PubMed1998

Neurogenic hypotension in patients with severe head injuries.

OBJECTIVE: To examine the occurrence of hypotensive episodes in patients with severe traumatic brain injuries that are not of hypovolemic origin and to investigate possible neurogenic or iatrogenic causes of such episodes. METHODS: We reviewed Traumatic Coma Data Bank (TCDB) records of the 248 patients with early hypotension. We attempted to eliminate episodes related to hemorrhagic hypovolemia by excluding patients with (1) extracranial injuries of Abbreviated Injury Scale scores > 3 (n = 99, 40%); (2) postresuscitation hematocrit levels < 35% (n = 76, 30.6%); (3) hematocrit levels decreasing to < 35% during the first 24 hours after injury (n = 47, 19%); and (4) patients with conflicting data (n = 5, 2%). This left 21 patients (8.5%) without discernible extracranial causes for their hypotension. RESULTS: Of these 21 patients, 4 had no extracranial injuries and 4 had only a single injury with Abbreviated Injury Scale score = 1. Hypotensive episodes were not associated with terminal or unsalvageable status. Mortality was 43%. Of the multiple factors investigated, the only two that were strongly associated with these "unexplained" hypotensive episodes were the presence of a diffuse injury pattern on computed tomography (n = 15, 71%) and the early use of mannitol or furosemide (n = 16, 76%) (It was policy at TCDB centers that hypotensive patients not receive diuretics until they were resuscitated.) CONCLUSIONS: (1) Some episodes of severe traumatic brain injury-related hypotension may be of neurogenic origin. (2) The risk/benefit ratio of early diuretic use in patients with severe traumatic brain injuries may be too high to support liberal use. These data strongly support the need for a study involving prospective collection of data describing the early blood pressure courses in such patients.

Adolescent↗
PubMed1996

Dual X-ray absorptiometry quality control: comparison of visual examination and process-control charts.

Dual X-ray absorptiometry (DXA) is widely used to monitor treatment efficacy in reducing the rate of bone mineral loss. In order to assure the validity of these measurements, instrument quality control of the DXA scanners becomes very important. This paper compares five quality control procedures (visual inspection, Shewhart chart with sensitizing rules, Shewhart chart with sensitizing rules and a filter for clinically insignificant mean changes, moving average chart and standard deviation, and cumulative sum chart [CUSUM]) in their ability to identify scanner malfunction by means of (1) an analysis of five longitudinal phantom data sets that had been collected during a clinical trial and (2) an analysis of simulated data sets. The visual inspection method is relatively subjective and depends on the operator's experience and attention. The regular Shewhart chart with sensitizing rules has a high false alarm rate. The Shewhart chart with sensitizing rules and an additional filter for clinically insignificant mean changes has the lowest false alarm rate but a relatively low sensitivity. The CUSUM method has good sensitivity and a low false alarm rate. In addition, this method provides an estimate of the date a change in the DXA scanner performance might have occurred. The method combining a moving average chart and a moving standard deviation chart came closest to the performance of the CUSUM method. Comparing the advantages and disadvantages of all methods, we propose the use of the CUSUM method as a quality control procedure for monitoring DXA scanner performance. For clinical trials use of the more intuitive Shewhart charts may be acceptable at the individual sites provided their scanner performance is followed up by CUSUM analysis at a central quality assurance center.

Absorptiometry, Photon↗
PubMed1996

Magnetic resonance imaging of the calcaneus: preliminary assessment of trabecular bone-dependent regional variations in marrow relaxation time compared with dual X-ray absorptiometry.

RATIONALE AND OBJECTIVES: Marrow transverse relaxation time (T2*) in magnetic resonance (MR) imaging may be related to the density and structure of the surrounding trabecular network. We investigated regional variations of T2* in the human calcaneus and compared the findings with bone mineral density (BMD), as measured by dual X-ray absorpiometry (DXA). Short- and long-term precisions were evaluated first to determine whether MR imaging would be useful for the clinical assessment of disease status and progression in osteoporosis. METHODS: Gradient-recalled echo MR images of the calcaneus were acquired at 1.5 T from six volunteers. Measurements of T2* were compared with BMD and (for one volunteer) conventional radiography. RESULTS: T2* values showed significant regional variation; they typically were shortest in the superior region of the calcaneus. There was a linear correlation between MR and DXA measurements (r = .66 for 1/T2* versus BMD). Differences in T2* attributable to variations in analysis region-of-interest placement were not significant for five of the six volunteers. Sagittal MR images had short- and long-term precision errors of 4.2% and 3.3%, respectively. For DXA, the precision was 1.3% (coefficient of variation). CONCLUSION: MR imaging may be useful for trabecular bone assessment in the calcaneus. However, given the large regional variations in bone density and structure, the choice of an ROI is likely to play a major role in the accuracy, precision, and overall clinical efficacy of T2* measurements.

Absorptiometry, Photon↗
PubMed1995

Accurate assessment of precision errors: how to measure the reproducibility of bone densitometry techniques.

Assessment of precision errors in bone mineral densitometry is important for characterization of a technique's ability to detect longitudinal skeletal changes. Short-term and long-term precision errors should be calculated as root-mean-square (RMS) averages of standard deviations of repeated measurements (SD) and standard errors of the estimate of changes in bone density with time (SEE), respectively. Inadequate adjustment for degrees of freedom and use of arithmetic means instead of RMS averages may cause underestimation of true imprecision by up to 41% and 25% (for duplicate measurements), respectively. Calculation of confidence intervals of precision errors based on the number of repeated measurements and the number of subjects assessed serves to characterize limitations of precision error assessments. Provided that precision error are comparable across subjects, examinations with a total of 27 degrees of freedom result in an upper 90% confidence limit of +30% of the mean precision error, a level considered sufficient for characterizing technique imprecision. We recommend three (or four) repeated measurements per individual in a subject group of at least 14 individuals to characterize short-term (or long-term) precision of a technique.

Absorptiometry, Photon↗
PubMed1995

Current methods and advances in bone densitometry.

Bone mass is the primary, although not the only, determinant of fracture. Over the past few years a number of noninvasive techniques have been developed to more sensitively quantitate bone mass. These include single and dual photon absorptiometry (SPA and DPA), single and dual X-ray absorptiometry (SXA and DXA) and quantitative computed tomography (QCT). While differing in anatomic sites measured and in their estimates of precision, accuracy, and fracture discrimination, all of these methods provide clinically useful measurements of skeletal status. It is the intent of this review to discuss the pros and cons of these techniques and to present the new applications of ultrasound (US) and magnetic resonance (MRI) in the detection and management of osteoporosis.

Absorptiometry, Photon↗
PubMed1994

Sex differences in bone mineral density in 1653 men and women in the sixth through tenth decades of life: the Rancho Bernardo Study.

This cross-sectional population-based study examined the effect of age and sex on bone mineral density (BMD) in the elderly. BMD was measured at the spine and hip using dual-energy x-ray absorptiometry and at midshaft and ultradistal radius using single-photon absorptiometry in 672 men and 981 women aged 50-98 years. In both sexes, mean BMD levels decreased significantly with age at all sites except the male spine. In linear regression models, the slope of loss was significantly greater in women than in men at all sites except the ultradistal radius. The slope was steeper at most sites in women aged 50-59 years than in older women, 60-98 years. In both age groups, mean age-adjusted BMD levels were lower at all sites in women who were past or never users of replacement estrogen than in women who were current estrogen users. Current estrogen users generally had lower slopes of loss with age than never or past estrogen users; however, few of these differences were statistically significant. We conclude that BMD levels decrease in old age in both sexes. Continued bone loss in old age raises the possibility that intervention to retard further loss may still be warranted in the elderly.

Absorptiometry, Photon↗
PubMed1994

Correlates of bone mineral density in the postmenopausal estrogen/progestin interventions trial.

We assessed the cross-sectional relationship of age, menopausal years, body mass, previous estrogen use, and ethnic background to bone mineral status in a sample of 875 healthy postmenopausal women at the time they were recruited from the community to participate in a multicenter clinical trial. The women were 1-10 years postmenopause, 45-64 years of age, and had not received estrogen replacement therapy within 3 months of enrollment. Of the participants, 89% were white, 69% had a spontaneous menopause, and 53% had a history of previous estrogen replacement therapy. Bone mineral density (BMD) of the lumbar spine (L2-4) and proximal femur was measured by dual-energy x-ray absorptiometry. Results were consistent with a significant negative linear regression of BMD on age or years from menopause. Body mass index (BMI) correlated significantly with BMD at all sites (L 2-4 r = 0.28; femoral neck r = 0.34, p < 0.0001). BMD adjusted for age and BMI were higher at both sites in women who had taken estrogen versus those who had not (L2-4 0.976 +/- 0.009 versus 0.932 +/- 0.01; femoral neck 0.740 +/- 0.006 versus 0.708 +/- 0.008, p < 0.05). Adjusted BMD also increased with duration of ERT. Parity was negatively associated with L2-4 BMD (p = 0.03) but did not correlate significantly with BMD at the femoral neck. Black women had the highest L2-4 BMD, and Hispanic women had the highest femoral neck BMD, even when results were adjusted for age and BMI. When data were corrected for differences in bone size, these interethnic differences were no longer significant. We conclude that increased body mass is positively correlated with BMD, and this may confer a degree of skeletal protection to heavier postmenopausal women. Exposure for 5 years to exogenous estrogen is associated with significantly increased age- and BMI-adjusted BMD.

Absorptiometry, Photon↗
PubMed1994

Early, routine paralysis for intracranial pressure control in severe head injury: is it necessary?

OBJECTIVE: To investigate the efficacy of early, routine use of neuromuscular blocking agents for intracranial pressure management in patients with severe head injury. DESIGN: Retrospective review of data from the Traumatic Coma Data Bank. The Traumatic Coma Data Bank was a collaborative project of the National Institute of Neurological Disorders and Stroke that involved four Level I trauma centers. The Traumatic Coma Data Bank prospectively collected data on 1,030 severe head-injured patients (Glasgow Coma Score of < or = 8) between 1984 and 1987. SETTING: Four Level I trauma centers coordinated by the National Institute of Neurological Disorders and Stroke. PATIENTS: A total of 514 Traumatic Coma Data Bank patients who met study inclusion criteria were divided into two groups: group 1 consisted of 239 patients who were pharmacologically paralyzed starting within the first intensive care unit (ICU) shift or < or = 6 hrs into the second shift and lasting for at least 12 hrs. Group 2 contained the remaining 275 patients who did not fulfill these criteria. MEASUREMENTS AND MAIN RESULTS: We analyzed the acute care course of these patients from the time of injury through admission, resuscitation, and ICU stay, as well as their rehabilitation follow-up results for < or = 1 yr. These two groups did not differ significantly regarding admission intracranial computed tomography diagnosis, admission Glasgow motor score, percentage of monitored time that intracranial pressure was > or = 20 mm Hg, or frequency of initial intracranial pressure > or = 20 mm Hg. In group 2, more patients were aged > 40 yrs (24% vs. 15% in group 1) or had admission hypotension (33% in group 2 vs. 25% in group 1). Multivariate regression analysis showed that ICU stay was significantly longer in group 1 (mean 7.76 days) than group 2 (mean 4.84 days; p < .001). The occurrence of pneumonia was significantly higher in group 1 (29% vs. 15%, p < .001). There was a tendency toward a higher occurrence of sepsis in group 1, but this difference did not reach statistical significance (11% vs. 7%, p = .08). The final Glasgow Outcome Scale scores for the two groups were not significantly different in those survivors with good and moderate outcomes. Although there were more deaths in group 2 (39% vs. 24%, p < .001), there were more vegetative or severely disabled survivors in group 1 (8% vs. 4% and 21% vs. 13%, respectively). CONCLUSIONS: Our findings suggest that early, routine, long-term use of neuromuscular blocking agents in patients with severe head injuries to manage intracranial pressure does not improve overall outcome and may actually be detrimental because of the prolongation of their ICU stay and the increased frequency of extracranial complications associated with pharmacologic paralysis. We suggest that routine early management of the head-injured patient in the ICU should be accomplished using sedation alone and that neuromuscular blockade should be generally reserved for patients with intracranial hypertension who require escalation of treatment intensity.

Adolescent↗
PubMed1994

The localizing value of asymmetry in pupillary size in severe head injury: relation to lesion type and location.

Reliable Assessment of the probability that a head injury patient harbors a surgical intracranial lesion is critical to both triage and treatment. The authors analyzed data from 608 patients with severe head injuries (Glasgow Coma Scale score, < or = 8) in the Traumatic Coma Data Bank to assess the reliability of pupillary asymmetry in predicting the presence and location of an intracranial mass lesion. Of 210 patients with pupillary asymmetry of > or = 1 mm, 63 (30%) had intracranial mass lesions, 52 (25%) of which were extra-axial in location, 38 (73%) of these located ipsilateral to the larger pupil. Of 51 patients with asymmetry of > or = 3 mm, 22 (43%) had intracranial mass lesions, 18 (35%) of which were extra-axial in location, 14 (64%) of these located ipsilateral to the larger pupil. For both asymmetry categories, strong interactions were found with age and mechanism of injury, the highest incidence of extra-axial lesions occurring in older patients injured other than as occupants of motor vehicles. The authors developed regression equations that provide a graphic means to predict the presence of an intracranial hematoma using data on pupillary asymmetry, age, and mechanism of injury. This predictive model, interpreted in a hospital- and patient-specific fashion, should be of significant use in directing triage, activating diagnostic and therapeutic resources, and evaluating the utility of exploratory trephination.

Accidents, Traffic↗
PubMed1993

Early and late systemic hypotension as a frequent and fundamental source of cerebral ischemia following severe brain injury in the Traumatic Coma Data Bank.

The outcome from severe head injury (GCS < or = 8 mmHg) was prospectively studied in patients from the Traumatic Coma Data Bank. We investigated the impact on outcome of hypotension (SBP < 90 mmHg) occurring from injury through resuscitation (early hypotension; N = 717) or in the Intensive Care Unit [ICU] (late hypotension; N = 493). Early hypotension occurred in 248 patients (34.6%) and was associated with a doubling of mortality (55% vs. 27%). If shock was present on admission, the mortality was 65%. These effects were independent of age, admission GCS motor score, presence of hypoxia, or associated severe extracranial trauma, suggesting that the influence of multiple system trauma in head injured patients is primarily due to associated hypotension. Late hypotension occurred in 156 of 493 patients (32%) and was the only hypotensive episode in 117 (24%). For 117 patients whose only hypotensive episode occurred in the ICU, 66% either died or were vegetative survivors, compared to 17% of patients who never suffered an hypotensive episode. Logistic regression modelling suggested that early and late shock were the most powerful independent predictors of mortality in this group of patients. These data demonstrate that hypotension is a common and devastating secondary brain insult in severe head injury patients, occurring not only during transport and resuscitation but also "right under our noses" in the ICU. We suggest that vigorous attention to eliminate or minimize such insults has the potential of markedly improving outcome from severe head injury.

Adolescent↗
PubMed1993

The role of secondary brain injury in determining outcome from severe head injury.

As triage and resuscitation protocols evolve, it is critical to determine the major extracranial variables influencing outcome in the setting of severe head injury. We prospectively studied the outcome from severe head injury (GCS score < or = 8) in 717 cases in the Traumatic Coma Data Bank. We investigated the impact on outcome of hypotension (SBP < 90 mm Hg) and hypoxia (Pao2 < or = 60 mm Hg or apnea or cyanosis in the field) as secondary brain insults, occurring from injury through resuscitation. Hypoxia and hypotension were independently associated with significant increases in morbidity and mortality from severe head injury. Hypotension was profoundly detrimental, occurring in 34.6% of these patients and associated with a 150% increase in mortality. The increased morbidity and mortality related to severe trauma to an extracranial organ system appeared primarily attributable to associated hypotension. Improvements in trauma care delivery over the past decade have not markedly altered the adverse influence of hypotension. Hypoxia and hypotension are common and detrimental secondary brain insults. Hypotension, particularly, is a major determinant of outcome from severe head injury. Resuscitation protocols for brain injured patients should assiduously avoid hypovolemic shock on an absolute basis.

Abbreviated Injury Scale↗
PubMed1992

Extracranial complications of severe head injury.

In order to define the role of intracranial and extracranial complications in determining outcome from severe head injury, 734 patients from the Traumatic Coma Data Bank were analyzed. Nine classes of intracranial and 13 classes of extracranial complications occurring within the first 14 days after admission were analyzed, while controlling for age, admission Glasgow Coma Scale motor score, early hypoxia or hypotension, and severe extracranial trauma. Outcome for survivors was based on the last recorded Glasgow Outcome Scale score, obtained a median of 521 days after injury. Intracranial complications did not significantly alter outcome for the study group. Of the extracranial complications, pulmonary, cardiovascular, coagulation, and electrolyte disorders occurred most frequently at 2 to 4 days. Infections developed later, peaking at 5 to 11 days. Gastrointestinal, renal, and hepatic complications followed no specific time course. Electrolyte abnormalities were the most frequent occurrence (59% of patients) but did not alter outcome. Pulmonary infections (41%), shock (29%, systemic blood pressure < or = 90 mm Hg for 30 minutes or more), coagulopathy (19%), and septicemia (10%) were significant independent predictors of an unfavorable outcome. Backward-elimination, stepwise logistic regression modeling indicated that the estimated reduction of unfavorable outcome was 2.9% for the elimination of pneumonia, 3.1% for coagulation disturbances, 1.5% for septicemia, and 9.3% for shock. These data suggest that extracranial complications are highly influential in determining the outcome from severe head injury and that significant improvements in outcome in a sizeable proportion of patients could be accomplished by improving the ability to prevent or reverse pneumonia, hypotension, coagulopathy, and sepsis.

Adolescent↗
PubMed1991

Visual impairment and retinopathy in people with normal glucose tolerance, impaired glucose tolerance, and newly diagnosed NIDDM.

OBJECTIVE: Prevalence rates of visual impairment and retinopathy were compared in 1992 people with normal glucose tolerance, impaired glucose tolerance (IGT), or newly diagnosed non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Glucose tolerance status was based on an oral glucose tolerance test after exclusion of those with a history of diabetes and/or diabetes medication use in an upper middle-class community of older white adults in southern California between 1984 and 1987. RESULTS: Although many sex-specific comparisons were made between glucose tolerance groups, only a few emerged as statistically significant. Among those, women with IGT had significantly higher age-adjusted rates of visual impairment (10.8%) than women with normal glucose tolerance (4.4%). Among men, those with IGT had significantly higher age-adjusted rates of visual impairment (7.9%) than men with newly diagnosed NIDDM (4.0%). CONCLUSIONS: Low frequencies of retinopathy were found in all three glucose tolerance groups.

Age Factors↗
PubMed1991

Evaluation of fasting plasma glucose as screening test for NIDDM in older adults. Rancho Bernardo Study.

OBJECTIVE: To examine the efficiency of fasting plasma glucose (FPG) as a screening test for non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH AND METHODS DESIGN: A population-based evaluation was made of FPG as screening test for NIDDM in an upper middle-class white community of Rancho Bernardo, California. NIDDM was defined by 2-h postchallenge plasma glucose (PCPG) level greater than or equal to 11.1 mM, the cutoff point recommended by the World Health Organization. Participants comprised a population-based sample of 1851 men and women 50-79 yr of age that represented 80% of surviving participants surveyed between 1972 and 1974 for the Lipid Research Clinic Prevalence Study. Those with insulin-dependent diabetes were excluded. RESULTS: Analyses were stratified by age after logistic regression indicated that FPG and age (but not gender) were significantly related to probability of disease. As FPG cutoff points increased, sensitivity and percentage of the population to be recalled for confirmation decreased, whereas specificity and positive predictive value increased. Negative predictive value was consistently in the 90% range. Specificity did not change with age. In contrast, at virtually every FPG cutoff point, sensitivity decreased with increasing age. For example, at FPG greater than or equal to 6.7 mM, sensitivity was 65.6% for those 50-64 yr of age and 40.0% for those 65-79 yr of age. At FPG greater than or equal to 7.2 mM, these sensitivities were 46.9 and 28.5%, respectively. Positive predictive value increased with increasing age, reflecting the increasing prevalence of NIDDM with age. CONCLUSIONS: Poorer sensitivity with increasing age reflects the fact that the numerator of the sensitivity equation is not affected by age (mean FPG did not vary significantly between age-groups), whereas the denominator increases with age (mean PCPG increased from 6.6 mM for subjects 50-64 yr of age to 8.2 mM for subjects 65-79 yr of age). Nevertheless, because the clinical significance of increasing PCPG with age in older adults is unknown, age-specific screening criteria probably are not warranted.

Age Factors↗
PubMedDate not supplied

Predictors of outcome following severe head trauma: follow-up data from the Traumatic Coma Data Bank.

Outcome as a function of employment status or return to school was evaluated in severely head-injured patients. A priori we selected the most salient demographic, physiological, neuropsychological and psychosocial outcome predictors with the aim of identifying which of there variables captured at baseline or 6 months would best predict employability at 6 or 12 months. Based on the patients evaluated at 6 months, 18% of former workers had returned to gainful employment and 62% of former students had returned to school. For those not back to work or school at 6 months, 31% of the former workers and 66% of the former students had returned by 12 months. Age, length of coma, speed for both attending and motor movements, spatial integration, and intact vocabulary were all significantly related to returning to work or school. The three most potent predictors for returning to work or school were intactness of the patient's verbal intellectual power, speed of information processing and age.

Activities of Daily Living↗