Circumscribed cognitive dysfunction in middle-aged adults with type 2 diabetes

OBJECTIVE

To examine the extent to which type 2 diabetes is associated with poorer performance on measures of learning, memory, psychomotor speed, and problem-solving in middle-aged adults.

RESEARCH DESIGN AND METHODS

This cross-sectional study evaluated 50 adults (age range 34-65 years, mean 50.8) with type 2 diabetes and 50 demographically similar community control subjects without diabetes. Each subject received a thorough physical examination and a detailed neuropsychological assessment. Factor analysis was used to assign specific tests to 1 of 4 cognitive domains (learning, memory for stories, problem-solving, and psychomotor speed). Hierarchical regression analysis was used to identify demographic and biomedical variables associated with cognitive dysfunction.

RESULTS

Learning, memory, and problem-solving skills were unaffected by type 2 diabetes. In contrast, psychomotor slowing was predicted by a diagnosis of diabetes (r2 change = 0.075, P < 0.002) with additional variance in psychomotor efficiency explained independently by HbA1 (r2 = 0.064, P < 0.003) and vibratory threshold (r2 = 0.112, P < 0.0001). The magnitude of psychomotor slowing on specific tests ranged from 12% (Digit Vigilance) to 23% (Grooved Pegboard).

CONCLUSIONS

Middle-aged adults with type 2 diabetes manifest psychomotor slowing that is associated with poorer metabolic control, whereas learning, memory, and problem-solving skills appear to be largely intact. The development of psychomotor slowing may be a manifestation of a "central neuropathy" induced by chronic hyperglycemia.

Why is learning and memory dysfunction in Type 2 diabetes limited to older adults?

Review of the literature on the cognitive correlates and consequences of Type 2 diabetes reveals two very intriguing findings. Not only are verbal learning and memory skills most likely to be disrupted as compared to other cognitive skills (e.g. attention, executive function; psychomotor efficiency), but these mnestic deficits appear to be restricted to individuals with diabetes who are older than 60-65 years of age. Middle-aged adults with either Type 2 or Type 1 diabetes are apparently protected insofar as researchers have only infrequently reported learning and memory impairments in that age group. Why do older adults have such an increased risk of diabetes-associated memory dysfunction? In our view, this phenomenon is a consequence of a synergistic interaction between diabetes-related metabolic derangements and the structural and functional changes occurring in the central nervous system (CNS) that are part of the normal ageing process. To critically evaluate that possibility, we summarise what is known about learning and memory dysfunction in the adult with diabetes, examine the extent to which chronic hyperglycaemia may adversely affect the integrity of the CNS, and selectively review the literature on age-associated changes in brain morphology and cognitive function, paying special attention to the threshold theory of cognitive impairment.

The psychometric and cardiac effects of pseudoephedrine in the hyperbaric environment

STUDY OBJECTIVES

To examine the psychometric and cardiac effects of pseudoephedrine at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the agent's safety in the diving environment.

DESIGN

Double-blind, placebo-controlled, crossover study.

SETTING

Monoplace hyperbaric chamber of a university hospital.

SUBJECTS

Thirty active divers (mean age 38 yrs).

INTERVENTION

A bank of seven tests was used to assess cognitive function during four different simulated dive combinations: placebo-1 atm, placebo3 atm, pseudoephedrine-1 atm, and pseudoephedrine-3 atm.

MEASUREMENTS AND MAIN RESULTS

Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures analysis of variance was used to analyze the effects of pseudoephedrine, depth, and drug-depth interaction. No significant, independent effects of pseudoephedrine were seen on any of the seven psychometric test scores (p>0.05), although the drug tended to increase anxiety scores (p=0.092). Depth resulted in a significant increase in anxiety scores (p=0.021) and a significant decrease in verbal fluency test scores (p=0.041); it had no significant effects on the other five psychometric tests (p>0.05). Pseudoephedrine caused a significant increase (p=0.036) in mean heart rate, and depth caused a significant decrease (p=0.013). Neither pseudoephedrine nor depth affected cardiac rhythm.

CONCLUSION

Pseudoephedrine does not cause significant alterations in psychometric performance at 3 atm of pressure that might increase the risk of diving. Depth causes significant adverse effects on anxiety levels and semantic memory at 3 atm. Pseudoephedrine and depth have significant but opposite effects on heart rate; although, these effects are unlikely to be clinically significant during diving. It is unlikely that pseudoephedrine adds significant risk to the diver.

The psychometric and cardiac effects of dimenhydrinate in the hyperbaric environment

STUDY OBJECTIVES

To examine the psychometric and cardiac effects of dimenhydrinate at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the drug's safety in the diving environment.

DESIGN

Double-blind, placebo-controlled, crossover study

SETTING

Monoplace hyperbaric chamber of a university hospital.

SUBJECTS

Thirty active divers (mean age 38 yrs).

INTERVENTIONS

A bank of seven tests was used to assess cognitive function during four different dive combinations: placebo-1 atm, placebo-3 atm, dimenhydrinate-1 atm, and dimenhydrinate-3 atm.

MEASUREMENTS AND MAIN RESULTS

Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures multivariate analysis of variance was used to analyze the effects of dimenhydrinate, depth, and drug-depth interaction. Dimenhydrinate resulted in a significant decrease in scores of mental flexibility (trail-making, part B, p<0.05) but had no effect on scores in the six other psychometric tests (p>0.05). It had no effect on mean heart rate (p>0.05), although frequent unifocal ventricular ectopic beats occurred in two subjects after ingestion of the drug. Depth resulted in a significant decrease in verbal memory test scores (p=0.001) and mean heart rate (p<0.001).

CONCLUSION

Dimenhydrinate adversely affects mental flexibility. This effect, when added to the adverse effect of depth on memory, may contribute to the dangers of diving.

Hypoglycemia: a complication of diabetes therapy in children

Hypoglycemia is the most common acute complication in insulin-treated type 1 diabetic patients. Most surveys have demonstrated that the tighter the glycemic control, and the younger the patient, the greater the frequency of both mild and severe hypoglycemia. However, people in poor metabolic control, with high glycosylated hemoglobin levels, are not protected from experiencing severe hypoglycemia. Focusing on the pediatric population, we review new or controversial issues surrounding the prevalence of hypoglycemia, its causes, its consequences and preventive strategies, and discuss possible mechanisms underlying the variability of responses to hypoglycemia.

Effects of lovastatin on cognitive function and psychological well-being

PURPOSE

Animal research and cross-sectional studies suggest that serum lipid concentrations may influence cognitive function, mood, and behavior, but few clinical trials have studied these effects.

SUBJECTS AND METHODS

In this double-blind investigation, 209 generally healthy adults with a serum low-density-lipoprotein (LDL) cholesterol level of 160 mg/dL or higher were randomly assigned to 6-month treatment with lovastatin (20 mg) or placebo. Assessments of neuropsychological performance, depression, hostility, and quality of life were conducted at baseline and at the end of the treatment period. Summary effect sizes were estimated as z scores on a standard deviation (SD) scale.

RESULTS

Placebo-treated subjects improved between baseline and posttreatment periods on neuropsychological tests in all five performance domains, consistent with the effects of practice on test performance (all P <0.04), whereas those treated with lovastatin improved only on tests of memory recall (P = 0.03). Comparisons of the changes in performance between placebo- and lovastatin-treated subjects revealed small, but statistically significant, differences for tests of attention (z score = 0.18; 95% confidence interval (CI), 0.06 to 0.31; P = 0.005) and psychomotor speed (z score = 0.17; 95% CI, 0.05 to 0.28; P = 0. 004) that were consistent with greater improvement in the placebo group. Psychological well-being, as measured several ways, was not affected by lovastatin.

CONCLUSION

Treatment of hypercholesterolemia with lovastatin did not cause psychological distress or substantially alter cognitive function. Treatment did result in small performance decrements on neuropsychological tests of attention and psychomotor speed, the clinical importance of which is uncertain.

A 10-year experience with toxic epidermal necrolysis

Toxic epidermal necrolysis is a devastating medication-induced desquamation disorder with a reported mortality rate of 30% to 60% in adults. Data from previously reported series suggest that age, delay in referral to a burn center, total body surface area (TBSA) involvement, and systemic steroid treatment are poor prognostic indicators. We reviewed the records of 39 patients treated in our burn center over the past 10 years and found that the mortality rate was significantly correlated with age, thrombocytopenia, and delay in presentation. Steroid treatment and TBSA involvement were not significantly related to the mortality rate. Thirty-nine adult patients with greater than 20% TBSA epithelial necrosis were cared for in our center from January 1987 to March 1998. Wounds were treated with topical antimicrobial medications and porcine xenografts in a bacteria-controlled nursing unit. We reviewed the records of these patients for 28 clinical characteristics and looked for clinical correlates of mortality by single analysis of variance. The mortality rate was 44% (17 of 39 patients); the cause of death was most commonly multiple-organ dysfunction syndrome, for which a microbial etiologic agent was not always identified. Autopsies were performed on 11 of the 17 patients who died; there was evidence of multiple-organ damage. The patients who survived and the patients who died did not differ significantly in TBSA epithelial necrosis (66%+/-6% vs 72%+/-5%, respectively), admission platelets, number of nosocomial infections, number of complications, preadmission exposure to steroids, or extent of mucosal involvement. When compared with the patients who died, the patients who survived were (1) 20 years younger (47.5+/-4.2 years vs 64.5+/-5.3 years), (2) admitted to the hospital sooner after the onset of their rash (3.5+/-0.4 days vs 5.9+/-1.0 days), (3) much less likely to experience early thrombocytopenia (platelet nadir, 154+/-24 vs 70+/-18), (4) more likely to be febrile on presentation, and (5) less likely to have been treated with antibiotics before referral to our unit. These differences were statistically significant. The most common etiologic agents were antibiotics, anticonvulsants, and nonsteroidal anti-inflammatory drugs. Our results for a group of older patients with toxic epidermal necrolysis with extensive skin involvement suggest that age, delay in hospitalization, thrombocytopenia, and early empiric antibiotic treatment are associated with a poor prognosis.

Current expectations for survival in pediatric burns

BACKGROUND

Conventional wisdom and published reports suggest that children, particularly those younger than 48 months, have higher mortality rates after burns than young adults. However, coincident with refinements in resuscitation, operative techniques, and critical care, survival rates for children with burns seem to have improved. To document this change and to define current expectations, a review of deaths during two 7-year intervals separated by a decade was done.

DESIGN

We examined the clinical course of children who died after admission for care of acute thermal burns during two 7-year intervals: calendar years 1974 to 1980 inclusive (group 1) and 1991 to 1997 inclusive (group 2). Dying children were stratified by total body surface area (TBSA) burned: small (0%-39%), midsize (40%-59%), and large (60%-100%) TBSA burns. Children who arrived with anoxic brain injury or in a moribund state with refractory shock were excluded from analysis (4 children in group 1 and 5 in group 2); 2 of these children in group 2 died and became solid organ donors.

SETTING

Regional pediatric burn center.

PATIENTS

Six hundred seventy-eight children in group 1 and 1150 children in group 2.

MAIN OUTCOME MEASURE

Survival.

RESULTS

In children with 0% to 39% TBSA burns, mortality was 0.6% in group 1 and 0% in group 2 (Fisher exact test, P = .04; chi2 test, P = .02). In children with 40% to 59% TBSA burns, mortality was 7.7% in group 1 and 0% in group 2 (Fisher exact test, P = .07; chi2 test, P = .047). In children with 60% to 100% TBSA bums, mortality was 33.3% ingroup 1 and 14.3% in group 2 (Fisher exact test, P = .04; chi2 test, P = .02). Although 59% of the children in group 2 were younger than 48 months, including 55% of those with 40% to 59% TBSA burns and 41% of those with 60% to 100% TBSA burns, there were no deaths in this age group.

CONCLUSION

Survival rates after burns have improved significantly for children. At present, most children, even young children and children with large burns, should survive.

Long-term outcome of children surviving massive burns

CONTEXT

Major advances in treatment of burn injuries in the last 20 years have made it possible to save the lives of children with massive burns, but whether their survival comes at the cost of impaired quality of life is unknown.

OBJECTIVE

To investigate the long-term quality of life in children who have survived massive burns.

DESIGN AND SETTING

Retrospective, cross-sectional study conducted in a regional pediatric burn center.

PATIENTS

Eighty subjects who were younger than 18 years at the time of injury, who survived massive burns involving > or =70% of the body surface, and who were admitted to the burn center between 1969 and 1992 were evaluated an average (SD) of 14.7 (6.0) years after injury.

MAIN OUTCOME MEASURES

Short Form 36 (SF-36) scores of the 60 patients aged at least 14 years were compared with national norms and the impact of clinical variables on individual domain scores was assessed.

RESULTS

The SF-36 domain scores of the study patients, who had survived massive burns at a mean (SD) age of 8.8 (5.5) years, were generally similar to the normal population). However, 15% and 20% of the burn patients had scores in the physical functioning and physical role domains, respectively, that were more than 2 SDs below the relevant norm, indicating that a few patients had continuing serious physical disability. Better functional status of the family predicted a higher score in physical role (P = .04). The child's early reintegration with preburn activities predicted higher scores in general health (P = .03), physical functioning (P = .003), and physical role (P = .01). Children followed up consistently in the multidisciplinary burn clinic for 2 years had higher physical functioning (P = .04).

CONCLUSIONS

In this study, while some children surviving severe burns had lingering physical disability, most had a satisfying quality of life. Comprehensive burn care that included experienced multidisciplinary aftercare played an important role in recovery.

Hypoglycemia in children with type 1 diabetes mellitus. Risk factors, cognitive function, and management

This article examines the relationship between hypoglycemia and brain function in children with type 1 diabetes. Hypoglycemic episodes occurring in the first 5 years of life may permanently disrupt cognitive function in a subset of children with diabetes, and a single acute episode of hypoglycemia may produce a transient reduction in mental efficiency, alter the electroencephalogram, and increase regional cerebral blood flow. Because iatrogenic development of hypoglycemic unawareness and autonomic failure are the most likely mediators of moderately severe hypoglycemia, medical management efforts should be directed at the prevention of frequently recurring, mild hypoglycemia.

Management of severe toxic epidermal necrolysis in children

Toxic epidermal necrolysis (TEN) is a severe form of erythema multiforme that results in extensive epidermal sloughing; the condition is associated with a mortality of up to 70%. From 1991 to 1998, 10 children with severe toxic epidermal necrolysis were referred to a regional pediatric burn facility. Wounds were managed with strategy involving prevention of wound desiccation and superinfection, including the frequent use of biologic wound coverings. Children unable to guard their airway because of extensive oropharyngeal involvement were prophylactically intubated. Enteral nutrition was stressed. Steroids were not used and antibiotics were administered to managed specific foci of infection only. The 2 boys and 8 girls had an average age of 7.2+/-1.8 years (range 6 months to 15 years) and sloughed surface area of 76+/-6% of the body surface (range 50 to 95%). Antibiotics (3 children), anticonvulsants (3 children), nonsteroidals (2 children), and viral syndrome or unknown agents (2 children) were felt to have triggered the syndrome. Six children (60%) required intubation for an average of 9.7+/-1.8 days (range 2 to 14 days). Buccal mucosal involvement occurred in 9 (90%) and ocular involvement in 9 (90%). Although infectious complications were common (2 pneumonias, 2 urinary infections, 1 bacteremia, 2 central line infections, and 2 candidemias), all children survived after lengths of stay in the burn unit averaging 19+/-3 (range 6 to 40) days. The most common long-term morbidity was keratitis sicca (2 children, 20%), finger nail deformities (3 children, 30%), and variegated skin pigment changes (5 children, 50%). Although having both a cutaneous and visceral wound that predispose them to infectious complications, most children with TEN will survive if managed with a strategy emphasizing biologic wound closure, intensive nutritional support, and early detection and treatment of septic foci. Burn units have the resource set required to manage severe TEN and early referral of such children may have a favorable impact on survival.

The perception of safe driving ability during hypoglycemia in patients with type 1 diabetes mellitus

PURPOSE

Insulin-induced hypoglycemia and its sequelae of cognitive impairment may place patients with type 1 diabetes at risk when driving and when making decisions about driving. Little is known about the factors that influence judgments of safe driving ability during hypoglycemia in these patients.

PATIENTS AND METHODS

Thirty men and 30 women with uncomplicated type 1 diabetes (age [mean +/- SD] 33 +/- 9 years, duration 9 +/- 3 years, hemoglobin A1c level 8.7% +/- 1.0%) underwent a stepped hypoglycemic insulin clamp. Serum glucose levels were reduced from 120 mg/dL to 80, 70, 60, 50, and then 40 mg/dL during 190 minutes. At each glucose plateau, patients completed a symptom questionnaire and neuropsychological test, estimated their glucose level, and reported whether they could drive safely.

RESULTS

The proportion of patients judging that they could drive safely decreased as serum glucose levels decreased from 70% at 120 mg/dL to 22% at 40 mg/dL. Men and middle-aged patients were more likely to consider it safe to drive during hypoglycemia than women and those under 25 years of age. Those who were symptomatic and those who recognized hypoglycemia were less likely to report safe driving ability during hypoglycemia. Most patients who were cognitively impaired appeared to recognize this and reported that they could not drive safely at a serum glucose level of 40 mg/dL.

CONCLUSIONS

Adults with type 1 diabetes need educational reinforcement of safe driving habits, particularly to check glucose levels before driving. Glucose levels less than 70 mg/dL should be treated before driving. This information is as important for middle-aged, experienced drivers as it is for younger, inexperienced drivers.

The metabolic basis of the increase of the increase in energy expenditure in severely burned patients

BACKGROUND

Severe burn trauma is characterized by an elevated rate of whole-body energy expenditure.

APPROACH

In this short review, we have attempted to assess the metabolic characteristics of and basis for the persistent increase in energy expenditure during the flow phase of the injury. We consider some aspects of normal energy metabolism, including the contribution of the major adenosine triphosphate (ATP)-consuming reactions to the standard or basal metabolic rate. Rate estimates are compiled from the literature for a number of these reactions in healthy adults and burned patients, and the values are related to the increased rates of whole-body energy expenditure with burn injury.

RESULTS

Whole-body protein synthesis, gluconeogenesis, urea production, and substrate cycles (total fatty acid and glycolytic-gluconeogenic) account for approximately 22%, 11%, 3%, 17%, and 4%, respectively, of the burn-induced increase in total energy expenditure.

CONCLUSIONS

These ATP-consuming reactions, therefore, seem to explain approximately 57% of the increase in energy expenditure. The remainder of the increase may be due, in large part, to altered Na(+)-K(+)-ATPase activity and increased proton leakage across the mitochondrial membrane.

Neuropsychological study of frontal lobe function in psychotropic-naive children with obsessive-compulsive disorder

OBJECTIVE

The authors' goal was to evaluate cognition in children with obsessive-compulsive disorder (OCD) early in their illness.

METHOD

They administered neuropsychological tests to 21 pediatric patients with OCD and 21 healthy children matched for age, sex, socioeconomic status, and intelligence. The children with OCD were not depressed, and none had ever received psychotropic medication. The neuropsychological tests were used to assess the relationship between psychiatric symptoms and cognitive function.

RESULTS

The children with OCD performed as well as the healthy children on the neuropsychological tests. Psychiatric symptoms and cognitive performance were not related.

CONCLUSIONS

Nondepressed children with recently diagnosed OCD who had never received psychotropic medication demonstrated no cognitive impairment according to their performance on neuropsychological tests. The authors conclude that OCD symptoms may not interfere with cognitive abilities early in the illness.

Acute hand burns in children: management and long-term outcome based on a 10-year experience with 698 injured hands

OBJECTIVE

To document long-term results associated with an coordinated plan of care for acutely burned hands in children.

SUMMARY AND BACKGROUND DATA

Optimal hand function is a crucial component of a high-quality survival after burn injury. This can be achieved only with a coordinated approach to the injuries. Long-term outcomes associated with such a plan of care have not been previously reported.

METHODS

Over a 10-year period, 495 children with 698 acutely burned hands were managed at a regional pediatric burn facility; 219 children with 395 injured hands were followed in the authors' outpatient clinic for at least 1 year and an average of >5 years. The authors' approach to the acutely burned hand emphasizes ranging and splinting throughout the hospital stay, prompt sheet autograft wound closure as soon as practical, and the selective use of axial pin fixation and flaps. Long-term follow-up, hand therapy, and reconstructive surgery are emphasized.

RESULTS

Normal functional results were seen in 97% of second-degree and 85% of third-degree injuries; in children with burns involving underlying tendon and bone, 70% could perform activities of daily living and 20% had normal function. Reconstructive hand surgery was required in 4.4% of second-degree burns, 32% of third-degree burns, and 65% of those with injuries involving underlying bone and tendon.

CONCLUSIONS

When managed in a coordinated long-term program, the large majority of children with serious hand burns can be expected to have excellent functional results.

Substance use disorders and the risk of HIV infection in gay men

OBJECTIVE

Previous studies have suggested that high rates of recent alcohol or drug use are associated with increased risk for HIV infection in gay men. To examine whether this relationship is mediated by substance use per se or by more enduring patterns of problematic substance use, lifetime DSM-III-R alcohol and other drug dependence disorders were ascertained and used to predict self-reported serostatus.

METHOD

Gay men (N = 187) who had been tested for HIV and knew their serostatus (31 are HIV+) completed demographic, drug use and sexual practices questionnaires. Formal DSM-III-R psychiatric diagnoses were made on the basis of an individual interview, using the Structured Clinical Interview for DSM-III-R.

RESULTS

Subjects had lifetime rates of alcohol dependence and drug dependence disorders that were two to three times higher than the general population, and 58% of the subjects who met criteria for alcohol dependence also met criteria for other substance dependence. Logistic regression analysis indicated that serostatus was best predicted by presence of both alcohol and drug dependence, and by race. When analyses were repeated in seronegative men, using unprotected anal sex as the outcome and recent substance use as predictors, no relationship between alcohol and behavior was found.

CONCLUSIONS

Data do not support the view that alcohol use alone increases the risk of HIV infection in gay men. Finding that risk for HIV is highest in men with histories of both alcohol and drug problems suggests that the link between HIV infection and substance use may be mediated by "third variables" that may include personality characteristics and situational factors.

Evaluating the Effects of Treatment for Medical Disorders: Has the Value of Neuropsychological Assessment Been Fully Realized?

Cognitive functioning can be affected by medical disorders and by the regimens used to treat them. To evaluate the cognitive risks and benefits of specific medical treatments, an increasing number of medical clinical trials have included a formal neuropsychological evaluation. This selective review has three goals: (a) to survey the range of assessment techniques used with different patient populations (e.g., those with diabetes, chronic obstructive pulmonary disease [COPD], hypertension, HIV, or cardiac disease) and treatment regimens (e.g., medical management, pharmacotherapy, surgery), (b) to demonstrate how cognitive outcome measures can contribute to an understanding of the value of certain treatments, and (c) to identify critical conceptual and methodological problems. The utility of this approach is incontrovertible-most large-scale medical trials have found either no adverse cognitive side effects or improved cognitive functioning following treatment. Nevertheless, before cognitive measures are routinely included in medical clinical trials, investigators will have to resolve problems that include the measurement of behavior change over time and the identification of clinically significant impairment.

Death in the burn unit: sterile multiple organ failure

It has been our impression over the years that the most common cause of death in our burn patients is multiple organ failure, despite the clinical absence of uncontrolled infection at the time of death. A six year review of all deaths in our unit confirmed this impression, revealing that multiorgan failure is indeed the most common cause of death (48 patients, 67 per cent), followed rather distantly by early withdrawal of support (15 patients, 21 per cent), resuscitation failure (4 patients, 6 per cent) and isolated pulmonary failure (4 patients, 6 per cent). Finally, we found that our patients dying of multiorgan failure, although often having had multiple small infections during their course, were indeed clinically uninfected at the time of death. These findings are consistent with the supposition that uncontrolled systemic inflammation, initially triggered by tissue injury and isolated infection, persists despite control of these infections and leads to multiple organ failure and death.

Cerebral blood flow in hypertensive patients: an initial report of reduced and compensatory blood flow responses during performance of two cognitive tasks

We asked whether the altered cerebral vasculature associated with essential hypertension might dampen or redirect the regional cerebral blood flow (rCBF) response to cognitive work. Relative rCBF was assessed with [(15)O]water positron emission tomography during a working memory task, a memory span task, and two perceptual control tasks. Unmedicated hypertensive patients and control subjects differed in rCBF response during both memory tasks. Hypertensives showed relatively diminished rCBF responses in right hemisphere areas combined with compensatory activation of homologous areas in the left cerebral cortex. Essential hypertension appears to selectively influence the circulatory reserve of portions of cerebral cortex and secondarily induce recruitment of other cortical areas to process certain tasks.

A rabbit model for metabolic studies after burn injury

BACKGROUND

A rabbit burn model was developed and characterized, which will allow conduct of repeated, noninvasive and more sophisticated in vivo metabolic studies to explore the pathophysiology of burn injury, owing to its larger blood volume and tissue mass than the rat.

MATERIALS AND METHODS

A 20% body surface, full thickness burn was applied to the backs of six anesthetized rabbits by immersion into a boiling-water bath for 10 s, followed by resuscitation with saline. Resting energy expenditure (REE) was measured daily in pre- and postburn periods. Whole body protein kinetics were evaluated using L-[1(-13)C]leucine tracer, on the preburn and the third postburn day. Fasting plasma glucose was also measured.

RESULTS

A significant elevation of REE began on the second postburn day and reached 34 +/- 8% above the preburn level (P < 0.05, paired t test) on the third postburn day. The fasting plasma leucine flux and oxidation were significantly elevated from their preburn levels (both P < 0.05), indicating an accelerated proteolysis and a more negative body protein balance (P < 0.05); however, the rate of whole body protein synthesis did not differ significantly pre- and postburn injury. Fasting plasma glucose also increased (P < 0.001). on the third postburn day. The burn scar remained intact during the study, without any sign of infection.

CONCLUSIONS

The metabolic changes observed in this animal model can be attributed to burn injury per se and they mimic those for flow phase in burn patients. This rabbit burn model should be suitable for exploring mechanistic aspects of the burn-induced changes in metabolism and nutrient balance.

Objective estimates of the probability of death from burn injuries

BACKGROUND

Over the past 20 years, there has been remarkable improvement in the chances of survival of patients treated in burn centers. A simple, accurate system for objectively estimating the probability of death would be useful in counseling patients and making medical decisions.

METHODS

We conducted a retrospective review of all 1665 patients with acute burn injuries admitted from 1990 to 1994 to Massachusetts General Hospital and the Shriners Burns Institute in Boston. Using logistic-regression analysis, we developed probability estimates for the prediction of mortality based on a minimal set of well-defined variables. The resulting mortality formula was used to determine whether changes in mortality have occurred since 1984, and it was tested prospectively on all 530 patients with acute burn injuries admitted in 1995 or 1996.

RESULTS

Of the 1665 patients (mean [+/-SD] age, 21+/-20 years; mean burn size, 14+/-20 percent of body-surface area), 1598 (96 percent) lived to discharge. The mean length of stay was 21+/-29 days. Three risk factors for death were identified: age greater than 60 years, more than 40 percent of body-surface area burned, and inhalation injury. The mortality formula we developed predicts 0.3 percent, 3 percent, 33 percent, or approximately 90 percent mortality, depending on whether zero, one, two, or three risk factors are present. The results of the prospective test of the formula were similar. A large increase in the proportion of patients who chose not to be resuscitated complicated comparisons of mortality over time.

CONCLUSIONS

The probability of mortality after burns is low and can be predicted soon after injury on the basis of simple, objective clinical criteria.