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Biomedical subjects

H C Thode

Publications and source records attributed to H C Thode.

At least 55 records · Page 3Linked to original sources
PubMed1996

Incremental benefit of individual American College of Surgeons trauma triage criteria.

OBJECTIVE: To determine the incremental benefit of individual American College of Surgeons (ACS) trauma triage criteria for prediction of severe injuries after consideration of concurrent physiologic, anatomic, mechanism, or "other" criteria. METHODS: A prospective cross-sectional study of motor vehicle crash victims transported to any of the 12 hospitals in a suburban/rural county by local ambulance services was performed. Demographic and individual ACS criteria were collected using structured data instruments. EDs provided patient disposition within 24 hours of patient arrival. Medical records were reviewed. Major outcomes were admission, operative interventions (OR), major nonorthopedic operative interventions or death (Maj-OR), and injury severity score (ISS). To optimize sensitivity and specificity of out-of-hospital triage decision rules, receiver operating characteristic (ROC) curves were derived. RESULTS: Of 1,545 patients, 13% were admitted; 6% had OR; 1% had Maj-OR; and 3% had ISSs > or = 16. For all outcomes, the most useful criteria were physiologic and anatomic. Some additional criteria (crash speed > 20 mph, > or = 30-inch vehicle deformity, axle displacement) substantially worsened specificity, with minimal or no improvement in sensitivity. For example, the optimal ROC curve for Maj-OR was determined by a systolic blood pressure < 90 mm Hg, Glasgow Coma Scale (GCS) score < 13, respiratory rate (RR) < 10 or > 29, death of a same-car occupant, penetrating injury, and/or > or = 24-inch opposite-side compartment intrusion (sensitivity, 85%; specificity, 87%). An ISS > or = 16 was predicted by GCS score < 13, RR < 10 or > 29, penetrating injury, 2 proximal long bone fractures, flail chest, > or = 24-inch opposite-side compartment intrusion, patient ejection, rollover, and/or age < 5 or > 55 years (sensitivity, 86%; specificity, 70%). CONCLUSION: Physiologic and anatomic trauma triage criteria predicted increased hospital resource utilization and severe injury. On the other hand, when used concurrently with physiologic, anatomic, and "other" criteria, some mechanism criteria worsen specificity with negligible improvement in sensitivity. In particular, crash speed > 20 mph and > or = 30-inch vehicle deformity had little predictive value for all outcomes.

Accidents, Traffic↗
PubMed1996

Renal gluconeogenesis and blood flow during endotoxic shock.

OBJECTIVES: To determine whether endotoxic shock decreases the renal gluconeogenic capacity and the renal artery blood flow. METHODS: An in-vivo, murine, nonrecirculating kidney perfusion model was studied in a trauma research laboratory. Each of 12 fasted, male Holtzman rats (shock n = 6, control n = 6) was injected with 1 mL of normal saline or endotoxin (20 mg/kg). Five hours after the injection, all the rats were anesthetized and blood samples were obtained for the determination of the plasma glucose. Right renal artery blood flow was measured by an ultrasonic small-animal flow meter. The kidney was then perfused via the renal artery with 37 degrees C, oxygenated, glucose-free Krebs-Henseleit solution in the presence of 100 mumol of phloridzin to inhibit the cellular uptake of glucose. Renal glucose production was determined by measuring glucose in both renal vein effluent and urine. After 30 minutes of equilibration, 5 mmol of lactate and 0.5 mmol of pyruvate were added to the perfusate as a gluconeogenic substrate. Renal vein and ureteral effluent samples were collected after 5, 10, and 15 minutes. RESULTS: The endotoxic shock group showed hypoglycemia (p < 0.05) as well as a decrease in renal artery blood flow (p < 0.05). Gluconeogenic stimulation was demonstrable in both the control and the endotoxic shock groups after 15 minutes of perfusion with substrate (p < 0.05). However, renal gluconeogenesis was significantly attenuated in the endotoxic shock group compared with the control. CONCLUSIONS: Renal glucose production in response to a gluconeogenic substrate is significantly attenuated during the hypoglycemic phase of endotoxic shock. Endotoxic shock also causes a significant decrease of renal artery blood flow.

Animals↗
PubMed1996

Evidence for and impact of selective reporting of trauma triage mechanism criteria.

OBJECTIVE: To determine whether out-of-hospital care charts selectively report trauma triage criteria, and the impact of such documentation on triage guideline development. METHODS: A special structured data instrument that requested the presence or absence of the American College of Surgeons (ACS) trauma triage criteria was completed by emergency medical services (EMS) personnel transporting victims of motor vehicle crashes. The standard written EMS report forms for a subset of 199 patients with at least 1 ACS trauma triage mechanism criterion were reviewed by the investigators. Outcome data were obtained from medical record review. The structured data instrument and the standard EMS report were compared for concordance. The impact of method of data collection on the ability of the ACS criteria to predict patient outcome was determined. RESULTS: EMS reports and structured data instruments similarly noted the presence of anatomic, physiologic, and "other" trauma triage criteria (p > 0.07 for all individual comparisons). Most mechanism-of-injury criteria noted on the data instrument (pedestrian struck > 20 mph; crash speed > 20 mph; vehicle deformity; compartment intrusion; rollover; and ejection) were infrequently documented on the standard EMS report (median 28.5% noted, range 0-100%). Patients who had mechanism criteria noted on the EMS report were more likely to be admitted to the hospital (44% vs 13%; p = 0.006), to require major operative procedures (10% vs 0%; p = 0.005), and to have prolonged lengths of stay (26% vs 9%; p = 0.02) and injury severity scores > or = 16 (15% vs 3%; p = 0.03) than were patients who had mechanism criteria documented only on the structured data instrument. CONCLUSIONS: In the authors' EMS system, standard EMS report documentation underreports ACS trauma triage mechanism criteria. This underreporting appears to bias outcome analysis in the direction of a worse outcome and more resource utilization. Reporting of mechanism-of-injury criteria improves with use of a structured data instrument.

Accidents, Traffic↗
PubMed1996

Association of training level and short-term cosmetic appearance of repaired lacerations.

OBJECTIVE: To determine the association between emergency practitioner level of training and cosmetic appearance of primarily closed wounds as evaluated at the time of suture removal. METHODS: A retrospective analysis of wound registry data was performed. At the time of wound closure, standard data were collected including details of patient demographics, wound characteristics, preparation, closure, and postoperative care, for consecutive patients sutured in the ED. Follow-up data were obtained at the time of the return visit using a previously described cosmetic scale. With the scale, all lacerations were assigned 0 or 1 point each for the presence or absence of six items: a step-off of borders; contour irregularities; margin separation; edge inversion; excessive distortion; and overall appearance. For analysis, the proportion of wounds with a score of 6 (optimal cosmetic appearance in all categories) was associated with practitioner level of training. RESULTS: Five hundred fifty-two patients' wounds were evaluated. The percentages of various practitioners' achieving an optimal cosmetic score were: medical students (MSs), 50%; first-year residents (EM1s), 54%; second-year residents (EM2s), 66%; third-year residents (EM3s), 68%; physician assistants (PAs), 70%; and attending physicians (APs), 66%. The senior practitioners (EM2s, EM3s, PAs, APs) were significantly more likely to obtain a maximal cosmetic score than were the junior practitioners (MSs, EM1s) (68% vs 52%, p = 0.016). CONCLUSION: Significant improvement in short-term cosmetic results following wound repair is associated with a training level beyond PGY1. These data reinforce the need for careful patient selection and close supervision of wound repair by trainees, especially of wound repair by medical students and interns.

Adolescent↗
PubMed1995

Cocaine-associated myocardial infarction. Mortality and complications. Cocaine-Associated Myocardial Infarction Study Group.

BACKGROUND: The frequency of complications in patients with cocaine-associated myocardial infarction is unknown. This study was performed to determine the short-term morbidity and mortality secondary to cocaine-associated myocardial infarction. METHODS: We performed a retrospective cohort study at 29 hospital centers throughout the United States. Patients with cocaine-associated myocardial infarction that occurred between 1987 and 1993 were identified through record review. The primary outcome measures were in-hospital mortality and the incidence and timing of major cardiovascular complications. RESULTS: Cocaine-associated myocardial infarction was identified 136 times in 130 patients. Patients were generally young (mean age, 38 years), nonwhite (72%), tobacco smokers (91%) with a history of cocaine use in the past 24 hours (88%). The initial electrocardiogram disclosed infarction in 44% and ischemia in an additional 18% of patients. Myocardial infarctions were evenly distributed between anterior (45%) and inferior (44%) and were most often non-Q-wave (61%). Complications occurred 64 times in 49 patients (36%; 95% confidence interval, 28% to 44%), including congestive heart failure in nine patients, ventricular tachycardia in 23 patients, supraventricular tachycardia in six patients, and brady-dysrhythmias in 26 patients. Most patients who had complications (90%) had them within 12 hours of presentation. Acute in-hospital mortality was 0% (95% confidence interval, 0% to 2%). CONCLUSIONS: The mortality of patients hospitalized with cocaine-associated myocardial infarction was low. The majority of complications occurred within 12 hours of presentation.

Adult↗
PubMed1995

Level of training, wound care practices, and infection rates.

This prospective, nonrandomized descriptive study compares the traumatic wound infection rates in patients based on level of training of emergency department (ED) practitioners. Wounds were evaluated in 1,163 patients. A wound registry data sheet was prospectively completed on all patients sutured in the ED. All practitioners were assigned a unique identification number. Follow-up data was obtained at the time of the return visit. Patients failing to return were contacted by telephone. Data were analyzed for patient wound infection rates by practitioner level of training. Patient wound infection rates by practitioner level of training were: medical students, 0/60 (0%); all resident physicians, 17/547 (3.1%); physician assistants, 11/305 (3.6%); and attending physicians 14/251 (5.6%), P was not significant. Comparison of junior (medical students and interns) to senior practitioners (all other practitioners) found no difference in infection rates (8/262 [3.1%] v 34/901 [3.8%], P = .58). In conclusion, carefully selected patients sutured by closely supervised medical students and junior residents have infection rates as low as those sutured by more experienced practitioners.

Adolescent↗
PubMed1995

Comparison of plain, warmed, and buffered lidocaine for anesthesia of traumatic wounds.

STUDY OBJECTIVE: To compare pain on infiltration, need for additional anesthesia, and pain on suturing in patients given plain, warm, and buffered lidocaine preparations before the suturing of traumatic wounds in the emergency department. DESIGN: Randomized, prospective, single-blinded convenience sample. SETTING: University hospital ED. PARTICIPANTS: Patients with traumatic lacerations. Patients allergic to lidocaine and patients with abnormal mental status or altered pain sensorium were excluded. INTERVENTIONS: All wounds were anesthetized by use of a standard injection technique. Wound margins were anesthetized with plain, buffered, or warm lidocaine in a randomized fashion. Pain of infiltration was recorded for each margin by means of a previously validated visual-analogue pain scale. RESULTS: The main outcome parameter was pain of infiltration. Need for additional anesthesia and pain on suturing were secondary outcome parameters. We evaluated 45 patients. Pain on injection varied by the type of lidocaine (mean pain scores: plain, 8.2; buffered, 4.7 [P < .05 versus plain]; warm, 4.9 [P < .05 versus plain]). There was no significant difference between the mean pain scores of the groups given warm and buffered lidocaine (P = NS). Need for additional anesthesia and pain on suturing did not vary by the type of anesthesia. The order of injection was not found to influence results. Mean pain scores were not different for margins 1 and 2 in any of the groups (P = NS). CONCLUSION: Both buffered and warmed lidocaine were as efficacious as plain lidocaine, and they had significantly less pain associated with infiltration than did plain lidocaine. In EDs with fluid warmers, warmed lidocaine may be the most convenient, well-tolerated, efficacious lidocaine preparation for anesthesia of traumatic wounds.

Adolescent↗
PubMed1995

Adequacy of hospital discharge data for determining trauma morbidity patterns.

To determine the adequacy of hospital discharge data for describing the nature and severity of multiple trauma, injury data coded from full hospital records were compared with injury data coded from discharge summaries for 83 plane crash survivors admitted to 14 different hospitals. Full hospital records indicated that 33% sustained intracranial, 39% thoracic, and 27% abdominal/pelvic injuries. Thirty-five percent had spinal fractures, 40% upper limb fractures, and 70% lower limb fractures. Discharge summary data missed 52% of the intracranial injuries, 28% of the thoracic injuries, and 30% of the spinal fractures, yet only missed 5% of the lower limb and 15% of the skull, pelvic, and upper limb fractures. These differences point to concerns regarding the use of discharge data for determining the nature, severity, and sequelae of injuries. The observed underreporting of neurological injury suggests a need to re-evaluate discharge data systems for measuring brain and spinal cord injury patterns, particularly given the increasing reliance on these systems for health policy and programmatic decision making.

Hospital Records↗
PubMed1995

Association of out-of-hospital criteria with need for hospital admission.

OBJECTIVE: To validate high-risk historical and physiologic out-of-hospital criteria as predictors of the need for hospitalization following ED evaluation. METHODS: Consecutive patients entered into the Suffolk County advanced life support system were enrolled. Previously proposed historical and physiologic "high-risk" criteria for hospitalization were prospectively collected. Criteria were associated with the need for hospital admission following ED evaluation. RESULTS: 1,238 patients were enrolled; 391 were released from an ED after transport. Most patients (843/1,238; 68%) were admitted to a hospital; and four died in the ED. Factors associated with an increased likelihood of admission or death among the transported patients were: bradycardia (90% admitted, p < 0.02); hypotension (80%, p < 0.03); hypertension (89%, p < 0.03); and age > 55 years (81%, p < 0.0001). Unresponsiveness and other abnormal vital signs were not associated with admission on univariate analysis. Logistic regression analysis identified two other factors associated with admission or death: tachycardia (72% admitted, p < 0.01) and head injury (78% admitted, p < 0.001). CONCLUSIONS: Abnormal pulse or blood pressure, head injury, and age > 55 years are associated with patients' requiring hospital admission after accessing the emergency medical services system. These criteria may aid the design of out-of-hospital refusal-of-care policies.

Adolescent↗
PubMed1995

Effective treatment for acute alkali injury to the esophagus using weak-acid neutralization therapy: an ex-vivo study.

OBJECTIVE: 1) To evaluate whether neutralization therapy with weak acid is effective in reducing observed histopathologic esophageal tissue injury secondary to liquid alkali, 2) to quantify the temperature change of the neutralizing agent, and 3) to determine the effect of interval to therapy on injury severity. METHODS: Harvested Sprague-Dawley rat esophagi were catheterized and placed in an oxygenated saline bath (37 degrees C) for 60 minutes and then fixed in 10% formalin. Nine groups (n = 10) were perfused with 50% sodium hydroxide (NaOH). Six of the groups were treated by neutralization with cooled orange juice (OJ) or cola that was maintained between 2 degrees C and 4 degrees C. This was performed at 0, 5, or 30 minutes after injury. In addition, two positive control groups were exposed to OJ or cola at time 0 and were not exposed to strong alkali. A third control group was exposed to strong alkali but was not administered any subsequent treatment. The temperature of the neutralizing agent was recorded prior to instillation and after exiting the esophagus. Blinded pathologic scoring of 0 (no injury) to 3 (severe) was recorded performed for six histopathologic categories: epithelial cell viability, cornified epithelial cell differentiation, granular cell differentiation, epithelial cell nuclei, muscle cells, and muscle cell nuclei. Comparisons were made among treatment times using the Kruskal-Wallis test and linear trend analysis. RESULTS: For each histopathologic category and each treatment mode, the Kruskal-Wallis test showed significant differences between the groups (p < 0.002) over time. Trend analyses showed more severe injury with delayed neutralization therapy (p < 0.05) for each treatment mode and histopathologic category. CONCLUSION: Early neutralization therapy with OJ or cola reduces acute esophageal alkali injury. Additional in-vivo study is needed before neutralization therapy is adopted for clinical use.

Acids↗
PubMed1995

Poor correlation of short- and long-term cosmetic appearance of repaired lacerations.

OBJECTIVE: To describe the consistency of a cosmetic scale for repaired lacerations and to determine whether the appearance of lacerations at the time of suture removal correlates with the appearance six to nine months later. METHODS: A convenience sample of patients who had lacerations repaired in a university teaching hospital were evaluated at the time of suture removal and six to nine months following repair. All lacerations were assigned 0 or 1 point each for the presence or absence of a step-off borders, contour irregularities, margin separation, edge inversion, excessive distortion, and overall appearance. A total cosmetic score (0-6) was calculated by adding the scores for the categories above. The consistency of the cosmetic scale was assessed by comparison of scores given by two different practitioners evaluating each patient at suture removal and long-term follow-up. The 38 evaluating practitioners were assigned based on availability and did not necessarily perform serial evaluations of the same patient. RESULTS: The 41 participating patients had a median age of 19 years (range, 2-82 years). Wounds were located predominantly on the head (73%) and upper extremity (22%). Long-term follow-up was performed at a median of 219 days (range, 155-280 days) after suture removal. Interpractitioner concordance regarding optimal appearance (score of 6 vs < or = 5) was moderate (kappa = 0.52) at the time of suture removal and substantial at the time of long-term follow-up (kappa = 0.68). However, the correlation of actual scores at the time of suture removal vs at long-term follow-up was poor (r = 0.17, p = 0.29). CONCLUSION: For our clinicians, the six-item categorical scale appears consistent as a tool for the assessment of the cosmetic appearance of wounds. However, correlation between laceration appearance at the time of suture removal and six to nine months later is poor.

Adult↗
PubMed1995

Histopathologic evaluation of the therapeutic efficacy of water and milk dilution for esophageal acid injury.

OBJECTIVE: To determine whether acid-induced injury to the esophagus is decreased by early dilutional therapy with water or milk. METHODS: A controlled in-vitro animal model for acid injury to the esophagus was carried out using esophagi harvested from 70 Sprague-Dawley rats of both sexes and weighing 250-350 g. One control and six experimental groups each containing ten esophagi were instilled with 1 mL of 0.5 normal solution of hydrogen chloride (N HCl). Dilution with water or milk was performed at 0, 5, or 30 minutes postinjury in the experimental groups. No dilution was performed with the control group. Specimens were maintained in an oxygenated saline bath for a 60-minute experimental period and then fixed in 10% formalin for histologic evaluation. Injury severity was rated by blinded histopathologic examination using scores of 0 (no injury), 1 (minor), 2 (moderate), and 3 (severe) for the histopathologic categories: cornified epithelial cells (CEs), granular cells (GCs), granular cell nuclei (GNs), and basal cells (BCs). Red blood cells were scored as positive or negative for lysis. RESULTS: The controls showed the most severe outcomes. Significant differences in injury occurred for all time periods and histopathologic categories, except for the GN/water and BC/milk histopathologic category/treatment groups. However, a linear trend analysis was significant for all histopathologic categories except BC. These analyses support decreased injury in the earlier treated groups. Injury severity was highest in the most superficial cell layer (CE). CONCLUSIONS: Emergency therapy with water or milk reduces acute acid injury to the esophagus. Earlier treatment is associated with decreased injury severity. This research supports the use of dilutional therapy with water or milk for acute acid injury to the esophagus.

Acids↗
PubMed1994

Therapeutic effects of water and milk for acute alkali injury of the esophagus.

STUDY BACKGROUND: Alkali ingestions cause progressive and devastating injury to the esophagus by liquefaction necrosis. However, the therapeutic efficacy of water or milk dilution for alkali-induced esophageal injury has not been determined. This study used our previously reported model of alkali-induced esophageal injury to evaluate the effectiveness of water and milk dilution. HYPOTHESIS: Early dilution with water or milk is efficacious in decreasing esophageal damage from alkali exposure. METHODS: The esopgagi of 75 Sprague-Dawley rats were harvested, and each end was cannulated with a 20-gauge catheter. Specimens were maintained in an oxygenated saline solution (at 37 degrees C) during a 60-minute experimental period and then fixed immediately in 10% Formalin solution for histologic examination. Esophagi from six experimental groups (total of 60) were perfused with 50% NaOH solution at time 0. Water or milk dilution was performed immediately at 0 minutes, 5 minutes after injury, and 30 minutes after injury. Blinded pathologic examination was performed using a score of 0 (no injury), 1 (minimal), 2 (moderate), or 3 (severe) for the following six histologic categories: epithelial viability, cornified epithelial cell differentiation, granular cell differentiation, epithelial cell nuclei, muscle cells, and muscle cell nuclei. RESULTS: Positive and negative controls showed expected outcomes. Significant progressions of injury over time were seen for every histologic category for both water and milk dilution. The injury scores for the milk-treated group at 0 minutes were less than or equal to the injury score for the water-treated group for all categories. However, these differences were significant only for the cornified epithelial cells. CONCLUSION: Early dilution therapy with water or milk reduces acute alkali injury of the esophagus and supports use of these forms of emergency treatment.

Acute Disease↗
PubMed1994

Evaluation of a new rapid quantitative immunoassay for serum myoglobin versus CK-MB for ruling out acute myocardial infarction in the emergency department.

STUDY OBJECTIVE: To compare the predictive values of serum myoglobin and creatine kinase (CK)-MB for ruling out acute myocardial infarction in the emergency department. DESIGN: Prospective, observational study. SETTING: University teaching hospital. PARTICIPANTS: One hundred eighty nine consecutive patients aged 30 years and older who presented within 12 hours from onset of chest discomfort, dyspnea, syncope, congestive heart failure, symptomatic dysrhythmia, pulmonary edema, or epigastric pain were entered into the study. Patients with trauma or renal failure were excluded. INTERVENTIONS: Standardized history and physical examination and blood sampling for serum myoglobin (S-Mgb) and CK-MB were done at the time of presentation (T0) and 1 hour later (T1). RESULTS: Using World Health Organization criteria, 22 acute myocardial infarction patients were identified. Mean time from symptom onset to presentation was 3.2 hours. S-Mgb was more sensitive than CK-MB at T0 and T1, 55% versus 23% (P < .05) and 73% versus 41% (P < .05), respectively. Respective specificities of S-Mgb versus CK-MB were 98% versus 99% (P = NS) at T0 and 97% versus 99% (P = NS) at T1. Negative predictive values of S-Mgb versus CK-MB were 94% versus 91% (P = NS) at T0 and 96% versus 93% (P = NS) at T1. The S-Mgb assay yielded quantitative results allowing the difference between the T0 and T1 values to be analyzed. A difference of 40 or more ng/mL between T0 and T1 was considered positive. When using a positive result in either the T0 or T1 value or a difference between the two values of 40 or more ng/mL, the sensitivity of S-Mgb was 91% (P < .05 versus CK-MB), the specificity was 96% (P = NS versus CK-MB), and the negative predictive value was 99% (95% confidence interval for S-Mgb, 97.0 to 100 versus CK-MB, 95% confidence interval, 88.9 to 96.6). CONCLUSION: In the first hour of presentation to the ED, the rapid quantitative assay for S-Mgb was statistically more sensitive than CK-MB and had an excellent negative predictive value for ruling out acute myocardial infarction in patients with typical or atypical symptoms. Due to the relatively small sample size, we could not exclude the possibility that differences in specificity might become statistically significant (beta error) with a larger sample size of acute myocardial infarction patients.

Confidence Intervals↗
PubMed1993

Where is the likelihood ratio test powerful for detecting two component normal mixtures?

We compare the power of the likelihood ratio test, the Engelman-Hartigan test, two outlier tests, four goodness-of-fit tests, and eight tests of normality to detect a mixture consisting of two components that are normally distributed with different means but equal variances. We consider the entire range of mixing proportions pi, 0 < pi < 1. For pi > .85 or pi < .15, overall Fisher's skewness statistic is best with Filliben's probability plot correlation coefficient test somewhat less powerful. A combined skewness and kurtosis test, the Anderson-Darling test, and the likelihood ratio test are also competitive. For .35 < pi < .65, the Engelman-Hartigan test is best. For other mixing proportions, the likelihood ratio test is best. For situations in which the preferred test had power 50% or more, the power of the likelihood ratio test is also above 50% and within 15 percentage points of the preferred test.

Alleles↗
PubMed1991

The likelihood ratio test for the two-component normal mixture problem: power and sample size analysis.

We find, through simulation and modeling, an approximation to the alternative distribution of the likelihood ratio test for two-component mixtures in which the components have different means but equal variances. We consider the range of mixing proportions from 0.5 through .95. Our simulation results indicate a dependence of power on the mixing proportion when pi less than .2 and pi greater than .80. Our model results indicated that the alternative distribution is approximately noncentral chi-square, possibly with 2 degrees of freedom. Using this model, we estimate a sample of 40 is needed to have 50% power to detect a difference between means equal to 3.0 for mixing proportions between .2 and .8. The sample size increases to 50 when the mixing proportion is .90 (or .1) and 82 when the mixing proportion is .95 (or .05). This paper contains a complete table of sample sizes needed for 50%, 80%, and 90% power.

Alleles↗
PubMed1990

Gamma distribution model describes maturational curves for delta wave amplitude, cortical metabolic rate and synaptic density.

We analyzed the available ontogenetic data (birth to 30 years of age) for: amplitude of delta EEG (DA) waves during sleep; cortical metabolic rate (CMR) measured with positron emission tomography; and synaptic density (SD) in frontal cortex. Each is at the adult level at birth, increases to about twice this level by 3 years of age, and then gradually falls back to the adult level over the next two decades. Statistical analyses revealed that individual gamma distribution models fit each data set as well as did the best ad hoc polynomial. A test of whether a single gamma distribution model could describe all three data sets gave good results for DA and CMR but the fit was unsatisfactory for SD. However, because so few data were available for SD, this test was not conclusive. We proposed the following model to account for these changes. First, cortical neurons are stimulated by birth to enter a proliferative state (PS) that creates many connections. Next, as a result of interactions in the PS, neurons are triggered into a transient organizational state (OS) in which they make enduring connections. The OS has a finite duration (minutes to years), and is characterized by high rates of information-processing and metabolism. Levels of CMR, SD and DA, therefore, are proportional to the number of neurons in the OS at any time. Thus, the cortex after birth duplicates, over a vastly greater time scale, the overproduction and regression of neural elements that occurs repeatedly in embryonic development. Finally, we discussed the implications of post-natal brain changes for normal and abnormal brain function. Mental disorders that have their onset after puberty (notably schizophrenia and manic-depressive psychoses) might be caused by errors in these late maturational processes. In addition to age of onset, this neurodevelopmental hypothesis might explain several other puzzling features of these subtle disorders.

Adolescent↗