Effect of injection rate on level and duration of hypobaric spinal anesthesia

The purpose of this study was to determine whether injection rate affects the spread of hypobaric spinal anesthesia. Hypobaric spinal anesthesia was performed on 20 patients for total hip arthroplasty. Dural puncture was performed with a 22-gauge Whitacre needle. All patients received 10 mg of hypobaric tetracaine with epinephrine. An electrically driven syringe pump was used to inject the anesthetic solution at either slow (250 sec) or fast (10 sec) rates. Ten patients received slow injections, and 10 received fast injections. Anesthetic levels, duration of anesthesia, and specific gravities of injectate and CSF were measured. Slow injection resulted in less spread of spinal anesthesia. Four-segment regression of anesthetic levels took significantly longer in the slow injection group. Local anesthetic mixtures used were consistently hypobaric compared to patient CSF. We conclude that slow injection of hypobaric tetracaine through a 22-gauge Whitacre needle produces lower levels of spinal anesthesia that tend to be of longer duration than levels resulting from fast injection.     

The Standard of Care: An Ethical Responsibility of Public Health Dentistry

Wide variation in the diagnosis and treatment of dental problems is indicative of the lack of a standard of care to guide the practitioner and to protect the public. Examples of questionable dental practices are described to illustrate how the public may be overtreated, overcharged, and put at risk of iatrogenic injury, practices that are no longer valid in light of current knowledge of dental diseases and their treatment. Public health dentistry traditionally concerns itself with community preventive, educational, and curative programs. It also has the ethical responsibility—the moral duty and obligation—to recognize and contend with paternalistic professional behavior that, intentionally or otherwise, violates the public trust, and to promote systems that will improve access, quality, and financing of dentistry for everyone.     

Malpractice in pediatric radiology: A survey in the United States and Canada

A survey of the chairmen of pediatric radiology departments in children's hospitals in Canada and the United States was undertaken to gain data on the subject of malpractice in pediatric radiology. Sixty-two members of the Society of Chairmen of Radiology in Children's Hospitals (SCORCH) were surveyed. Forty-two surveys (65%) were returned for analysis. Malpractice premiums paid per pediatric radiologist per year ranged from $499–$29,000 (mean $8,630). Twenty-eight malpractice claims were reported from 1980 to 1992. The largest number of claims involved gastrointestinal/abdomen and chest examinations, areas that were perceived as low risk by the respondents. The incidence of lawsuits against pediatric radiologists in the midwest was statistically higher compared to Canada (p<0.05). Private practice models had a statistically greater incidence of malpractice suits compared to university practice models (p<0.04). No statistical difference between the number of malpractice suits and the number of examinations performed per year or the number of pediatric radiologists in the group was found. We concluded that pediatric radiologists run the risk of malpractice claims. This data may aid in lessening this risk in the future.     

Disease prevention strategies for Army aviators: clues from a descriptive analysis of the flying duty medical examination.

The U.S. government spends approximately $300,000 to train an Army aviator. Maintaining a healthy aviator population is important not only to the completion of the aviation mission, but also for budgetary reasons. We reviewed Army aviator physical examinations and self-reported risk behavior questionnaires from the Aeromedical Epidemiological Data Repository at Fort Rucker, Alabama, to assess aviator health. Overall, aviators are healthy adults; however, the health status of aviators can be improved by reducing tobacco use, limiting cholesterol and fat intake, and wearing hearing protection devices both during and off duty.     

Disruption of synaptosomal calcium channel function by Lambert-Eaton myasthenic immunoglobulin is serum-dependent.

An autoantibody to nerve terminal Ca2+ channels has been suggested to mediate the pathogenesis of the neuromuscular disorder Lambert-Eaton Myasthenic Syndrome (LEMS). We demonstrated previously that in the presence of control human serum, immunoglobulins isolated from a patient with LEMS reduced flux of Ca2+ into isolated nerve terminals during depolarization. The objective of the present study was to determine the role of serum in reducing uptake of 45Ca2+ into rat brain synaptosomes by LEMS IgG. Depolarization-dependent uptake of 45Ca2+ through voltage-gated Ca2+ channels was determined using synaptosomes incubated with control (disease-free) and LEMS IgG with or without control human serum. In the absence of human serum, LEMS IgG did not reduce uptake of 45Ca2+ into synaptosomes. However, in the presence of control human serum (10% of total incubation volume), 45Ca2+ uptake was reduced significantly by LEMS IgG (2 and 4 mg/ml), but not by IgG from disease-free patients or by 10% (v/v) control human serum alone. This concentration of serum was found to be optimal; higher concentrations produced significant reductions in Ca2+ uptake, whereas at lower concentrations the serum/IgG combination was ineffective. The depressant effect of high concentrations of serum alone on 45Ca2+ uptake was mimicked by equal concentrations of bovine serum albumin suggesting that deficits in 45Ca2+ uptake produced by high concentrations of serum were due to increased protein binding of the radiolabel. Heat-inactivating the serum abolished its ability to interact with the LEMS immunoglobulins to depress 45Ca2+ uptake. This suggested a role for complement in this effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Excretion of porphyrins and porphyrin precursors during neuromuscular paralysis produced by dithiobiuret

Urinary excretion of porphyrin precursors delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) and total porphyrins was measured during intoxication of rats with 2,4-dithiobiuret (DTB), a chemical which produces delayed-onset neuromuscular weakness, in an attempt to ascertain whether or not DTB poisoning in the rat would serve as an animal model of the neurologic symptoms of acute intermittent porphyria. Daily administration of DTB (1 mg/kg/day, i.p.) produced flaccid skeletal muscle weakness first detected after 4 to 5 days of treatment. Onset of skeletal muscle weakness was associated with a significant increase in urinary excretion of ALA. The excretion of PBG and total porphyrin was also increased; however, the increase was not significant. The increase in porphyrins and porphyrin precursors was due to increased urine output which coincided with the onset of neuromuscular weakness; urinary concentrations of ALA, PBG, and porphyrins were not increased by DTB. Measurements of free-erythrocyte protoporphyrin, taken after 7 days of DTB treatment, indicated a significant elevation of free erythrocyte protoporphyrin concentration. The pattern of alterations in the heme precursors associated with DTB-induced paralysis in rats is quite different from that observed in humans afflicted with acute intermittent porphyria. Therefore, we conclude that DTB-induced paralysis in the rat does not represent an accurate animal model of acute intermittent porphyria.     

Hyponatremia-associated cognitive impairment in traumatic brain injury

The case of a traumatic brain injury (TBI) patient with dramatic cognitive deterioration in the absence of medical aetiology other than simultaneous decline in serum sodium led to an investigation of the association between declines in sodium levels and cognitive status. In a population of 50 persons undergoing TBI rehabilitation, 12 (24%) had relative (3 mEq/L) decreases in serum sodium while five (10%) experienced absolute hyponatremia (136 mEq/L). Correlation with cognitive status was significant when the absolute hyponatremia group was compared with those whose sodium levels remained above 136 mEq/L. A case-matched study of the relative hyponatremia group yielded no significant association between sodium-level decreases and cognitive status. These data support previous conclusions indicating wide variation in individual responses to changes in serum sodium. The threshold for significant effects of hyponatremia may be higher in patients with TBI than in populations studied previously.     

Carcinoma of the breast: detection with MR imaging versus xeromammography

Detectability of breast cancer with magnetic resonance (MR) imaging versus xeromammography was quantitatively compared. MR images were obtained of breasts of 120 women who underwent xeromammography. T1 values were determined for masses larger than 2 cm. Cancer was histologically confirmed in 39 breasts and was considered excluded from 81 due to results of biopsy, cyst aspiration, or sonography or absence of change in xeromammographic findings over time. Images were blindly interpreted by three observers, and results were expressed as receiver operating characteristic curves. Detectability of breast cancer was substantially better with xeromammography than with MR imaging for all observers (P less than .03, 10(-6), and .001). On MR images, spiculation of a mass, distorted architecture, skin thickening, and nipple or skin retraction were specific but relatively insensitive indicators of cancer. Masses with smooth, distinct margins and signal intensity greater than that of fat on T2-weighted images were always benign. Other findings and T1 values were not diagnostically useful. The authors conclude that xeromammography is superior to MR imaging in detection of breast cancer.     

Portal radiographs: digital enhancement of contrast

The quality of low-contrast portal radiographs for radiation therapy can be improved with electronic contrast enhancement. After the image is copied digitally with a laser scanner microdensitometer into 4,096 gray-scale levels (12 bits) and 1,686 X 2,048 pixels, a special software package permits linear, logarithmic, exponential, or sigmoid transformations of the optical density. The precise representation of the portal image can then be interactively adjusted to emphasize the desired anatomy. Clinical examples demonstrate the value of the digital enhancement approach.