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Biomedical subjects

K B Johnson

Publications and source records attributed to K B Johnson.

At least 19 recordsLinked to original sources
PubMed2001

Influence of hemorrhagic shock on remifentanil: a pharmacokinetic and pharmacodynamic analysis.

BACKGROUND: Hemorrhagic shock is known to alter significantly the pharmacokinetics of fentanyl, an opioid that requires delivery to the liver for metabolism. The authors hypothesized that the pharmacokinetics and pharmacodynamics of remifentanil, an esterase metabolized opioid that does not require delivery to a metabolic organ, would be altered less by hemorrhagic shock that those of fentanyl. METHODS: Sixteen pigs were assigned randomly to control and shock groups. The shock group was bled using an isobaric hemorrhage model. Remifentanil 10 microg x kg(-1) x min(-1) was infused for 10 min to both groups. Arterial samples were collected for remifentanil concentration assay. Pharmacokinetic parameters were estimated using a three-compartment model. The electroencephalogram spectral edge was used as a measure of drug effect. The pharmacodynamics were characterized using a sigmoid inhibitory maximal effect model. RESULTS: Remifentanil blood levels were higher in the shocked group. The central clearance was slower and the central compartment was smaller in shocked animals. No difference between groups was observed in the magnitude or time course of the remifentanil-induced decrease in spectral edge. CONCLUSIONS: Hemorrhagic shock altered the pharmacokinetics of remifentanil, suggesting that less remifentanil would be required to maintain a target plasma concentration. However, because of its rapid metabolism, the impact of hemorrhagic shock on the concentration decline of remifentanil after termination of the infusion was minimal. Hemorrhagic shock did not alter the pharmacodynamics of remifentanil.

Analgesics, Opioid↗
PubMed2001

Hopkins Teen Central: Assessment of an internet-based support system for children with cystic fibrosis.

UNLABELLED: Support groups are an important therapeutic intervention for patients with chronic debilitating illnesses. Patients who are difficult to assemble in one physical location may benefit from participating in an electronic support group (ESG). ESGs for adolescents have not been evaluated, although studies have shown a benefit to adult ESGs. Our goals were to create a web-based support service for adolescents with cystic fibrosis (CF) and to qualitatively and quantitatively measure the effects that such a support site could have on patients' relationships with the clinic faculty and staff, access to and interaction with peers with CF, and understanding of CF. METHODS: A highly interactive ESG was developed after discussions with a team of CF specialists and patients. Eighteen of 37 teenagers with CF agreed to use this site. Each patient was asked to assess his or her perceived availability of and comfort with the clinic staff and faculty, perceived support available through peers, knowledge about CF, and perceived usefulness of the Internet as a support tool. RESULTS: Participants logged into the site an average of 4 times each month. Teens who owned home computers accessed the site somewhat more frequently than did teens who were provided with home Internet access for the study. Most activity occurred in those sections of the site that described the participants and that allowed them to socialize. Over one half of the participants e-mailed each other at least once a week, with 77% e-mailing peers at least every other week. There was no significant difference in the participants' scores on a quiz about CF at the beginning and the end of the study; however, there was a significant decrease in perceptions about their knowledge about CF. At the conclusion of the study, participants believed that they had more friends who they could relate to than they did at the beginning of the study. Clinic staff noticed an increase in references to peers among the group who were using the site. In addition, 4 of the teens expressed a desire to get together to meet each other as a result of their interactions on the web site. There was no significant change in perceptions about the perceived availability and comfort with the clinic staff and faculty, support available through peers, knowledge about CF, and the usefulness of the Internet as a support environment. Managing the project was extremely easy, with virtually no technical or procedural issues arising during the study. CONCLUSIONS: Teenagers with a chronic disease will actively participate in an ESG. The social and expressive aspects of their involvement with this support group hold much promise.

Adolescent↗
PubMed2000

Quantifying the literature of computer-aided instruction in medical education.

PURPOSE: To characterize the literature about computer-aided instruction (CAI) as it relates to medical education. METHOD: A descriptive study using the Medline and ERIC databases, reviewing articles pertaining to CAI for medical professionals. The literature was evaluated with respect to type of article, journal, language, and year of publication. RESULTS: The search yielded 2,840 citations, 92% of which were in English. The number of journals with at least one citation was 747. Less than 5% of the 5,147 authors had three or more articles published in the CAI literature. Of the citations with abstracts, 60% were demonstrations of a CAI application, 11% were media-comparative studies, and 13% were analyses of the CAI field. While the pace of article publication increased markedly over time, the percentages of article types did not change significantly over time. Less than 10% of CAI articles appeared in core medical journals. CONCLUSION: Medical CAI is an increasingly popular topic of research and publication. However, these studies appear in journals with smaller circulations, are predominantly demonstration articles, and are generally written by authors with two or fewer publications. Evaluation articles remain less common. A series of analytic articles has appeared offering substantive suggestions for better research design. These suggestions appear to have gone unheeded. CAI investigators need be more aware of the gaps in the existing body of CAI publications, and the inherent difficulties of this type of research, if this literature is to move beyond this early stage of development.

Computer-Assisted Instruction↗
PubMed2000

Effectiveness of a clinical pathway for inpatient asthma management.

BACKGROUND: Clinical pathways for asthma are tools that have the potential to improve compliance with nationally recognized management guidelines, but their effect on patient outcomes has not been documented. OBJECTIVES: To determine the effect of an asthma clinical pathway on patients' length of stay, use of nebulized beta-agonist therapy while hospitalized, and use of acute care clinics for 2 weeks after discharge. DESIGN/METHODS: The study was a randomized, controlled trial. Patients between the ages of 2 and 18 years admitted with an asthma exacerbation and not under the care of an asthma specialist were eligible for the study. Patients were randomized either to a conventional ward (control group) or to a ward using the clinical pathway (intervention group). For 2 weeks after discharge, we collected data to determine whether patients visited a health care provider for worsening asthma. RESULTS: One hundred ten patients (26%) were enrolled. Control and intervention groups had similar demographic and asthma severity profiles. The intervention group had an average length of stay 13 hours shorter than did the control group. In addition, at every dosing interval, the intervention group received less nebulized beta-agonist therapy. There were no deaths in either group. CONCLUSION: A clinical pathway for inpatient asthma decreased the length of stay and beta-agonist medication use with no adverse outcomes or increased acute-care encounters through 2 weeks after discharge.

Administration, Inhalation↗
PubMed1999

Balloon rupture during stent implantation: A novel technique of salvage with a new manual power injector.

Pinhole leak or rupture of a stent delivery balloon is a well-recognized technical problem encountered in vascular interventions. This event leads to inadequate stent expansion. These stents cannot be fully deployed with the same balloon and frequently the balloon cannot be retrieved without dislodging the stent. We describe a technique for successful stent deployment in such situations using the Oz Power Syringe, a new manual power injector. Cathet. Cardiovasc. Intervent. 48:74-77, 1999.

Aged↗
PubMed1999

Internet TV set-top devices for web-based projects: smooth sailing or rough surfing?

BACKGROUND: The explosion of projects utilizing the World Wide Web in the home environment offer a select group of patients a tremendous tool for information management and health-related support. However, many patients do not have ready access to the Internet in their homes. For these patients, Internet TV set-top devices may provide a low cost alternative to PC-based web browsers. METHODS: As a part of a larger descriptive study providing adolescents with access to an on-line support group, we investigated the feasibility of using an Internet TV set-top device for those patients in need of Internet access. RESULTS: Although the devices required some configuration before being installed in the home environment, they required a minimum of support and were well accepted by these patients. However, these patients used the Internet less frequently than their peers with home personal computers--most likely due to a lack of easy availability of the telephone or television at all times. CONCLUSION: Internet TV set-top devices represent a feasible alternative access to the World Wide Web for some patients. Any attempt to use these devices should, however, be coupled with education to all family members, and an attempt at providing a dedicated television and phone line.

Adolescent↗
PubMed1999

Restricted natural language processing for case simulation tools.

For Interactive Patient II, a multimedia case simulation designed to improve history-taking skills, we created a new natural language interface called GRASP (General Recognition and Analysis of Sentences and Phrases) that allows students to interact with the program at a higher level of realism. Requirements included the ability to handle ambiguous word senses and to match user questions/queries to unique Canonical Phrases, which are used to identify case findings in our knowledge database. In a simulation of fifty user queries, some of which contained ambiguous words, this tool was 96% accurate in identifying concepts.

Computer Simulation↗
PubMed1999

The use of a new mechanically advantaged syringe for performing coronary intervention.

OBJECTIVE: To determine the utility of a new mechanically advantaged syringe in the performance of percutaneous coronary intervention. BACKGROUND: A new mechanically advantaged syringe has been developed to perform cardiovascular imaging. We wanted to assess the utility of this device in the performance of small catheter percutaneous coronary intervention. Data from coronary interventions performed with the standard technique at our institution, using a 10 ml manual syringe, were compared to the use of a new mechanically advantaged syringe. Contrast utilization during the standard technique was assessed by obtaining data from fifty consecutive successful single-vessel coronary interventions (angioplasty with or without stenting). After an initial learning experience with the mechanically advantaged syringe, fifty consecutive successful single-vessel coronary interventions were assessed. Most interventions performed using the mechanically advantaged syringe were with 6 French catheters. Detailed contrast utilization information was gathered. RESULTS: During the standard method of performing coronary intervention, 216 +/- 114 ml of contrast were used. Utilizing the mechanically advantaged OZ Power Syringe (Cardiovascular Innovations Inc., Athens, Texas), the contrast use was reduced to 66 +/- 39 ml (p < 0.0001) per case. The syringe also allowed excellent visualization despite using a smaller guide catheter system. CONCLUSION: The OZ Power Syringe can be utilized effectively in percutaneous coronary intervention. Our preliminary data suggest that there may be reduced contrast use without sacrificing image quality.

Angioplasty, Balloon, Coronary↗
PubMed1998

Remifentanil and propofol combination for awake craniotomy: case report with pharmacokinetic simulations.

Remifentanil and propofol infusions were used to provide neuroleptanalgesia during an awake craniotomy to resect a left frontoparietal glioblastoma near the motor speech center. This operation presented anesthetic requirements ranging from adequate analgesia during bone flap removal to an appropriate level of consciousness during cortical speech mapping. We performed pharmacokinetic simulations to estimate the effect site concentrations of propofol and remifentanil as the infusion rates were modulated to meet the dynamic sedation and analgesic needs of the operation. Simulations revealed that changes in infusion rates were quickly followed by changes in the effect site concentrations which corresponded well with the desired changes in patient sedation and analgesia. We propose that remifentanil and propofol in combination may be a useful technique for awake craniotomy.

Anesthesia, Intravenous↗
PubMed1997

The rubber meets the road: integrating the Unified Medical Language System Knowledge Source Server into the computer-based patient record.

Ongoing improvements in the content of the Unified Medical Language System, coupled with the recent release of the Internet-based Knowledge Source Server (KSS), have prompted us to develop an interface between the KSS and our computer-based patient record. We confronted many challenges while developing a robust interface to an Internet-based server, and in integrating the process of codification into the workflow of clinicians. An initial evaluation of the interface in the clinical environment suggests that acceptable performance is attainable. The benefits of using an Internet-accessible tool in a clinical information system appear to justify the effort required.

Humans↗
PubMed1997

The role of histamine in mediating the decompensatory phase of hemorrhagic shock in the rat.

Our laboratory has previously reported that plasma histamine levels rise significantly and coincidentally with the onset of the decompensatory phase of isobaric hemorrhagic shock in rats. The histamine levels seen in shock were comparable to those that induce profound vasodilatation in many vascular beds under normovolemic conditions. We, therefore, sought to determine whether the elevation in plasma histamine contributes to the cardiovascular collapse seen in the decompensatory phase of hemorrhagic shock. Sprague-Dawley rats were bled according to an isobaric bleeding protocol which maintained the mean arterial blood pressure (MAP) at 40 mmHg until death. Selected H1 (diphenhydramine) and/or H2 (cimetidine and famotidine) antagonists were administered at 75% of the estimated peak shed blood volume (PSBV), a point preceding the rise in plasma histamine. Plasma histamine levels in all groups were similar throughout the time course of hemorrhagic shock. None of the histamine receptor antagonists affected the time of onset or the rate of decompensation. Suspecting that hypotension may alter the animal's response to histamine, we investigated the effect of exogenous histamine administration on MAP before and after hemorrhage. In unbled animals, bolus histamine infusions (.6 mg/kg) dropped the MAP by 62.0 +/- 2.7 mmHg, however, in animals bled to 40 mmHg, histamine dropped the MAP by 7.2 +/- 2.7 mmHg (p = .002). On the basis of the results of these two interventions, we conclude that histamine is not an important mediator of the cardiovascular collapse seen in the decompensatory phase of hemorrhagic shock in the rat.

Adaptation, Physiological↗
PubMed1996

Functional classification of antidepressants based on antagonism of swim stress-induced fos-like immunoreactivity.

Autoradiographic analysis of 14C-2-deoxyglucose (2-DG) uptake and immunocytochemical assessment of Fos-like immunoreactivity (Fos-LI) were used to assess swim stress-induced changes in metabolic activity in brain and to define the effect of chronic treatment with antidepressants from different pharmacological classes. Saline-treated rats processed in the forced swim test exhibited marked increases in Fos-LI in limbic cortical regions, lateral septum, medial amygdala and paraventricular nucleus of the hypothalamus (PVN). Uptake of 2-DG was increased by swim stress in some of the same brain regions where Fos-LI was induced, with the notable exception of a lack of a change in the PVN. Rats received injections for 3 wk with imipramine, desipramine, fluoxetine, nisoxetine, tranylcypromine or mianserin before being processed in the forced swim test. Chronic treatment with imipramine and desipramine alone induced Fos-LI in the central nucleus of the amygdala and the dorsolateral bed nucleus of the stria terminalis. After tranylcypromine treatment, Fos-LI was induced in many brain regions including limbic cortex, amygdala and paraventricular nucleus of the hypothalamus. None of the other antidepressants induced Fos-LI in any brain region examined. Chronic administration of imipramine, desipramine and nisoxetine antagonized the swim induced expression of Fos-LI in the PVN and in limbic cortical regions, including the medial prefrontal ventrolateral orbital and cingulate cortices. Chronic treatment with fluoxetine, tranylcypromine and mianserin did not alter swim stress-induced Fos-LI in any brain region. Thus, only antidepressant drugs that affect norepinephrine uptake (i.e., imipramine, desipramine and nisoxetine) antagonized swim stress-induced Fos-LI. In contrast to the action of chronic imipramine on Fos-LI induced by swim, chronic administration of imipramine did not antagonize the stress-induced changes in 2-DG uptake in limbic cortical regions. Acute administration of propranolol, which blocks beta-adrenergic receptors, reduced the number of cells staining for Fos-LI in limbic cortical regions, resembling the effects produced by chronic imipramine, desipramine and nisoxetine. In the PVN, neither propranolol nor prazosin (an alpha 1 antagonist) blocked the swim-induced Fos-LI, suggesting that swim-induced Fos-LI in the PVN is not under control of beta- or alpha 1-adrenergic receptors. These latter results imply that adaptation of noradrenergic receptors by chronic imipramine may not be related to the antagonism of stress-induced Fos-LI. The clear functional differences of the various antidepressant agents on swim stress-induced Fos-LI after chronic administration provide a functional classification of antidepressant drug action not previously identified.

Animals↗
PubMed1996

Discharging patients with prescriptions instead of medications: sequelae in a teaching hospital.

OBJECTIVE: This study measures the incidence of discrepancies among written prescriptions, medication regimens transcribed onto patient discharge instruction sheets (DCIs), and labels on medications dispensed by community pharmacies after discharge of patients from an academic medical center. METHODS: During a 2-month study period, we collected copies of prescriptions and DCIs. We also called care givers after discharge and asked them to read the medication labels that were filled from discharge prescriptions. Care givers were also asked whether they received instruction from community pharmacies. RESULTS: Data were collected on 335 prescriptions for 192 patients. Differences among the prescriptions, DCIs, and medication labels were found for 40 (12%) of the medications prescribed at discharge, representing 19% of the patients studied. Nineteen prescriptions had prescriber errors in dosing frequencies or dosage formulations. Three prescriptions were filled with different medication concentrations or strengths than requested. Prescriptions were altered by the community pharmacists for unexplained reasons in 6 cases, whereas the DCIs and original prescriptions differed in 12 cases. Only 44% of families were counseled about proper medication administration by their pharmacists. CONCLUSIONS: A potential for medication errors exists when pediatric patients are discharged with unfilled prescriptions. The potential may be worsened when discharge instructions are created from a prescription rather than from the label of a dispensed medication. Educational and risk-management efforts should emphasize the importance of writing complete, legible prescriptions and consulting appropriate reference materials to ensure that dose formulations and guidelines are accurate. Whenever possible, prescriptions should be filled before patients are discharged, so that the dispensed medications can be reviewed, and health care providers can provide accurate discharge instructions.

Academic Medical Centers↗
PubMed1996

The effect of hypothermia on potassium and glucose changes in isobaric hemorrhagic shock in the rat.

Hypothermia has been shown to decrease oxygen consumption requirements and improve survival during hemorrhagic shock. however, hypothermia applied therapeutically does not prevent the development of a lactic acidosis during hemorrhage. We re-examined the development of a hemorrhage-induced lactic acidosis and other metabolic parameters (glucose, plasma electrolytes, and arterial blood gases) at various temperatures (29-37 degrees C) to better define the protective action of hypothermia in hemorrhagic shock. Five groups of male, Sprague-Dawley rats were bled to a mean arterial blood pressure (MABP) of 40 mmHg over a 15 min period and held there by further blood removal until death. The final level and rate of development of the lactic acidemia was the same in all groups. However, the rate of decline in plasma glucose and rate of rise in plasma potassium were temperature dependent. These results suggest that temperature-dependent changes in serum glucose and potassium may contribute to the protective effect of hypothermia during hemorrhagic shock.

Acidosis, Lactic↗
PubMed1995

Metabolic and functional mapping of the neural network subserving inferior collicular seizure generalization.

The sensory-motor portion of the inferior collicular cortex is capable of seizure genesis that is characterized initially by coincident wild running behaviors and localized electrographic afterdischarge. With repeated stimulations, this seizure activity spreads into the forebrain, producing generalized tonic-clonic or myoclonic seizure activity. In order to characterize the neural network subserving this caudal-rostral seizure generalization, three mapping techniques were used: 2-deoxyglucose (2-DG) utilization, c-fos expression and local anesthetic microinjection. Kindled seizure generalization from the inferior collicular cortex produced a global increase in 2-DG accumulation, while relative 2-DG increases were found in the inferior collicular cortex, dorsal lateral lemniscus, dorsal central gray, peripeduncular nucleus, medial geniculate nucleus, substantia nigra, entopeduncular nucleus, ventroposterior and centromedian thalamus and tenia tectum, as well as the perirhinal, somatosensory and frontal cortices. Kindled seizure generalization also increased c-fos-like immunoreactivity (FLI) in the inferior collicular cortex, cuneiform nucleus, dorsal lateral nucleus of the lateral lemniscus, peripeduncular nucleus, caudal central gray, dentate gyrus of the hippocampus, rhinal fissure area of the perirhinal cortex and the frontal cortex. Microinjections of procaine into the amygdala, perirhinal cortex, entopeduncular nucleus, substantia nigra, peripeduncular nucleus, dorsal central gray, and pontine reticular nucleus all prevented generalized seizure behaviors, but had no effect on the wild running seizures. Conversely, procaine microinjection into the area of the cuneiform nucleus/pedunculopontine tegmental nucleus prevented the wild running seizure but did not block the generalized seizure activity. Neither wild running, nor generalized seizures were altered following procaine microinjections into the anterior thalamus, sub-thalamus, lateral hypothalamus, hippocampus or deep superior colliculus. Thus, specific forebrain sites form a widespread neural network that mediates the generalization of seizure activity from the inferior collicular cortex into the forebrain.

Animals↗