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Biomedical subjects

B Stevens

Publications and source records attributed to B Stevens.

At least 37 records · Page 2Linked to original sources
PubMed1999

Reliability of an intravenous intermittent access port (saline lock) for obtaining blood samples for coagulation studies.

BACKGROUND: Patients admitted to rule out myocardial infarction often receive a heparin infusion that requires measurement of partial thromboplastin time every 6 to 8 hours until coagulation values stabilize. If the patient's acuity at admission does not necessitate placement of arterial or central catheters, insertion of an intermittent intravenous access port (saline lock) would decrease the need for frequent venipuncture. Many studies on obtaining blood samples via arterial and central catheters have been reported, but no reports have described the method of using a saline lock or the amount of blood discarded during that procedure. OBJECTIVE: To evaluate the efficacy of inserting a saline lock specifically for obtaining blood samples and to determine the amount of blood that must be discarded in order to obtain prothrombin and partial thromboplastin times that match the values from blood samples obtained via venipuncture. METHODS: Coagulation values determined with 2 consecutive blood samples obtained via the saline lock after the first 0.5 mL of blood withdrawn was discarded were compared with measurements determined with a blood sample obtained via venipuncture. RESULTS: Prothrombin and partial thromboplastin times were not significantly different among the 3 blood samples. CONCLUSION: The untoward effects of frequent venipunctures to obtain blood samples for measurement of prothrombin and partial thromboplastin times can be lessened by using an 18-gauge saline lock to obtain blood samples and discarding the first 0.5 mL of blood withdrawn before the samples for coagulation studies are collected.

Adult↗
PubMed1998

Control of myelination by specific patterns of neural impulses.

A cell culture preparation equipped with stimulating electrodes was used to investigate whether action potential activity can influence myelination of mouse dorsal root ganglia axons by Schwann cells. Myelination was reduced to one-third of normal by low-frequency impulse activity (0.1 Hz), but higher-frequency stimulation (1 Hz) had no effect. The number of Schwann cells and the ultrastructure of compact myelin were not affected. The frequency of stimulation that inhibited myelination decreased expression of the cell adhesion molecule L1, and stimulation under conditions that prevented the reduction in L1 blocked the effects on myelination. This link between myelination and functional activity in the axon at specific frequencies that change axonal expression of L1 could have important consequences for the structural and functional relationship of myelinating axons.

Action Potentials↗
PubMed1998

NGF and LIF both regulate galanin gene expression in primary DRG cultures.

Both target-derived and injury-induced factors could be involved in the axotomy-induced increases in galanin expression in dorsal root, ganglion (DRG) neurons. Galanin mRNA levels were studied in primary cultures of E13.5 embryos, grown for 14 days in culture, in response to two candidate molecules, nerve growth factor (NGF) and leukemia inhibitory factor (LIF). In these cultures, NGF withdrawal alone resulted in a significant increase in galanin mRNA. Addition of LIF onto NGF-containing cultures did not produce a significant increase, while addition of LIF to NGF-deprived cultures caused an upregulation of galanin mRNA which was significantly stronger than that of NGF withdrawal alone. Thus, NGF withdrawal and LIF increase act together to up-regulate galanin gene transcription in DRG neurons.

Animals↗
PubMed1998

Assessment of pain in the neonate.

This article critically reviews the measures developed for assessing pain in the human neonate. Information was gathered with a computerized literature search of published articles and abstracts, a manual review of relevant conference proceedings, recently published journals, unpublished reports and manuscripts, and personal files. This identified 16 measures that were critically examined for their psychometric properties (reliability and validity) and clinical use. Special emphasis was placed on the feasibility of using neonatal pain assessment measures for clinical practice to address the research-practice gap. Although considerable progress has been made in the field of neonatal pain assessment, few measures have adequately established psychometric properties and clinical utility. Furthermore, most measures have been developed for research and not for the clinical setting. Issues regarding sensitivity, specificity, and the ability to detect clinically important changes have not been addressed. A sufficient number of infant pain measures have now been developed to assess acute pain. There is a paucity of measures to assess chronic pain in infants, and measures for infants who are low birth weight, critically ill, or ventilated. Future research should be aimed at strengthening the properties of existing measures, and at the development of measures for those infants with chronic pain or special needs.

Behavior↗
PubMed1998

Managing pain after coronary artery bypass surgery.

Nurses are responsible for assessing patients' pain and intervening with modalities such as opioids. However, after coronary artery bypass surgery, patients experience moderate to severe pain and receive inadequate analgesia. These practices are problematic as unrelieved acute pain is harmful and may result in negative consequences that influence recovery. Consistent with the subjectivity and multidimensionality of pain, as described in Gate Control Theory, patients need to be involved as participants in their care where possible. Pain policies and education programs need to reflect current professional guidelines and be proactive in addressing staff and patient gaps in pain knowledge and misbeliefs.

Analgesics, Opioid↗
PubMed1998

Evidence-based pain management for infants.

The impact of pain on infants has been the topic of increasing research interest over the past decade. Although pain is now known to be stressful and the source of immediate and long term consequences, inadequate progress has been made in infant pain management. Research evidence provides the basis for effective pain management. However, the quality of the evidence, inconsistent findings, and the perceived lack of clinical relevance may have hindered the utilization of research on infant pain management in clinical practice. Reconceptualization of the definition of pain, increased methodologic rigor, validated assessment approaches, and systematic reviews of research studies on pain management may provide the opportunity for improved pain management using evidence-based practice.

Anesthetics, Local↗
PubMed1998

Comparison of the uptake of fine and ultrafine TiO2 in a tracheal explant system.

To examine the relationship between particle uptake by pulmonary epithelial cells and particle size, we exposed rat tracheal explants to fine particles (FPs; 0.12 micron) or ultrafine particles (UFPs; 0.021 micron) of titanium dioxide for 3 or 7 days. By electron microscopy, particles were found in the epithelium at both time points, but in the subepithelial tissues, they were found only at 7 days. The volume proportion of both FPs and UFPs in the epithelium increased from 3 to 7 days; it was greater for UFPs at 3 days but was greater for FPs at 7 days. The volume proportion of particles in the subepithelium at 7 days was equal for both dusts, but the ratio of epithelial to subepithelial volume proportion was approximately 2:1 for FPs and 1:1 for UFPs. Mean volume of individual particle aggregates was similar for both dusts at 3 days but was markedly smaller for FPs at 7 days. These observations suggest that the behavior of particles of different size is complex: UFPs persist in the tissues as relatively large aggregates, whereas the size of FP aggregates becomes smaller over time. UFPs appear to enter the epithelium faster, and once in the epithelium, a greater proportion of them is translocated to the subepithelial space compared with FPs. However, if it is assumed that the volume proportion is representative of particle number, the number of particles reaching the interstitial space is directly proportional to the number applied; i.e., overall, there is no preferential transport from lumen to interstitium by size.

Animals↗
PubMed1998

Pigeon fanciers' lung: the mucin antigen is present in pigeon droppings and pigeon bloom.

BACKGROUND: Pigeon intestinal mucin has been implicated as an important antigen pigeon fanciers' lung. This study investigated whether mucin is detectable in pigeon droppings and bloom, the likely antigenic sources in disease. METHODS: Soluble extracts of a number of materials found in a pigeon loft were prepared and specific IgG subclass antibodies to these antigens were measured in 14 antibody-positive pigeon fanciers. Cross-reactivity between these materials and purified pigeon intestinal mucin was investigated by inhibition of anti-mucin ELISA. Mucin was purified from the soluble extracts of these crude antigen mixtures by CsCl density gradient centrifugation. RESULTS: The patterns of IgG subclass responses to purified pigeon intestinal mucin and to the four materials collected from the pigeon loft were similar. Subclass differences between symptomatic and asymptomatic individuals, demonstrable against purified mucin, were similarly seen against pigeon droppings and pigeon bloom. Both pigeon droppings and pigeon bloom were capable of inhibiting IgG binding to purified pigeon mucin, and mucin inhibited substantially the binding of IgG to these materials. Glycoprotein with a density similar to that described for pigeon intestinal mucin was purified from each source. CONCLUSION: Pigeon intestinal mucin is present in a variety of materials found in the environment of the pigeon loft in a form capable of reacting with anti-mucin antibodies in the sera of exposed individuals. Reduction in exposure to these materials may decrease the likelihood of developing pigeon fanciers' lung and minimise reactions in sensitised individuals.

Animals↗
PubMed1998

A systematic review of lidocaine-prilocaine cream (EMLA) in the treatment of acute pain in neonates.

OBJECTIVE: Neonates routinely undergo painful cutaneous procedures as part of their medical treatment. Lidocaine-prilocaine 5% cream (EMLA) is a topical anesthetic that may be useful for diminishing the pain from these procedures. EMLA is routinely used in children and adults. There is substantial apprehension about its use in neonates because of concerns that it may cause methemoglobinemia. The objective of this review was to determine the efficacy and safety of EMLA as an analgesic for procedural pain treatment in neonates and provide evidence-based recommendations for clinical practice. METHODS: Systematic review techniques were used. Studies were identified using manual and computer-aided searches (Medline, EMBASE, Reference Update, personal files, scientific meeting proceedings). Behavioral (eg, facial action, crying) and physiologic (eg, heart rate, oxygen saturation, blood pressure, respiratory rate) outcome data from prospective nonrandomized controlled studies and randomized controlled trials in full-term and preterm neonates were accepted for inclusion to establish efficacy of EMLA. The risk of methemoglobinemia (defined as methemoglobin concentration >5% and requiring medical intervention) was estimated from all prospective studies. RESULTS: Eleven studies of the efficacy of EMLA were included in the analysis. Infant gestational age at the time of delivery ranged from 26 weeks to full-term. Two studies included data from both neonates and older infants. The following procedures were studied: circumcision (n = 3), heel lancing (n = 4), venipuncture (n = 1), venipuncture and arterial puncture (n = 1), lumbar puncture (n = 1), and percutaneous venous catheter placement (n = 1). Nine studies were randomized controlled trials. The total sample size for each study ranged from 13 to 110 neonates. The dose of EMLA used was 0.5 g to 2 g in 9 studies, and was not specified in the others. The duration of application ranged from 10 minutes to 3 hours. The three studies that investigated the efficacy of EMLA for decreasing the pain of circumcision used a randomized controlled trial design. All of them demonstrated significantly reduced crying time during the procedure in the infants in the EMLA group compared with the infants in the control group. Facial grimacing, assessed in two of the studies, was also significantly lower in the EMLA group. Using meta-analytic techniques, the heart rate outcome data for two studies was summarized. Increases in heart rate compared with baseline values were 12 to 27 beats per minute less for the EMLA group than in the placebo group during various stages of the surgical procedure. Three studies that investigated the pain from heel lancing were randomized controlled trials; the other was a nonrandomized controlled study. None demonstrated a significant benefit of EMLA for any of the outcome measures used to assess pain (ie, behavioral pain scores, infant crying, heart rate, blood pressure, respiratory rate, oxygenation parameters). One randomized controlled study of the pain from venipuncture showed that infants treated with EMLA had significantly lower heart rates and cry duration compared with infants treated with a placebo. In one nonrandomized study, a significantly lower behavioral pain score was observed for infants treated with EMLA compared with the control group. Infant heart rate, however, did not differ between the groups. In one randomized controlled study of pain from percutaneous venous catheter placement, EMLA resulted in a significantly lower increase in heart rate and respiratory rate. Behavioral pain scores were significantly lower during arterial puncture in one nonrandomized controlled study. EMLA did not reduce physiologic changes or behavioral pain scores in one randomized controlled trial in infants undergoing lumbar puncture. Meta-analytic techniques revealed that methemoglobin concentrations did not differ between EMLA-treated and placebo-treated infants (weighted mean di

Acute Disease↗
PubMed1997

Activity-dependent regulation of N-cadherin in DRG neurons: differential regulation of N-cadherin, NCAM, and L1 by distinct patterns of action potentials.

Cell adhesion molecule (CAM) expression is highly regulated during nervous system development to control cell migration, neurite outgrowth, fasciculation, and synaptogenesis. Using electrical stimulation of mouse dorsal root ganglion (DRG) neurons in cell culture, this work shows that N-cadherin expression is regulated by neuronal firing, and that expression of different CAMs is regulated by distinct patterns of neural impulses. N-cadherin was down-regulated by 0.1 or 1 Hz stimulation, but NCAM mRNA and protein levels were not altered by stimulation. L1 was down-regulated by 0.1 Hz stimulation, but not by 0.3 Hz, 1 Hz, or pulsed stimulation. N-cadherin expression was lowered with faster kinetics than L1 (1 vs. 5 days), and L1 mRNA returned to higher levels after terminating the stimulus. The RSLE splice variant of L1 was not regulated by action potential stimulation, and activity-dependent influences on L1 expression were blocked by target-derived influences. The results are consistent with changes in firing pattern accompanying DRG development and suggest that functional activity can influence distinct developmental processes by regulating the relative abundance of different CAMs.

Action Potentials↗
PubMed1997

Action potential-dependent regulation of gene expression: temporal specificity in ca2+, cAMP-responsive element binding proteins, and mitogen-activated protein kinase signaling.

Specific patterns of neural impulses regulate genes controlling nervous system development and plasticity, but it is not known how intracellular signaling cascades and transcriptional activation mechanisms can regulate specific genes in response to specific patterns of action potentials. Studies using electrical stimulation of mouse dorsal root ganglion neurons in culture show that the temporal dynamics of intracellular signaling pathways are an important factor. Expression of c-fos varied inversely with the interval between repeated bursts of action potentials. Transcription was not dependent on a large or sustained increase in intracellular Ca2+, and high Ca2+ levels separated by long interburst intervals (5 min) produced minimal increases in c-fos expression. Levels of the transcription factor cAMP-responsive element binding protein (CREB), phosphorylated at Ser-133, increased rapidly in response to brief action potential stimulation but remained at high levels several minutes after an action potential burst. These kinetics limited the fidelity with which P-CREB could follow different patterns of action potentials, and P-CREB levels were not well correlated with c-fos expression. The extracellular-regulated kinase (ERK) mitogen-activated protein kinases (MAPK) also were stimulated by action potentials of appropriate temporal patterns. Bursts of action potentials separated by long intervals (5 min) did not activate MAPK effectively, but they did increase CREB phosphorylation. This was a consequence of the more rapid dephosphorylation of MAPK in comparison to CREB. High expression of c-fos was dependent on the combined activation of the MAPK pathway and phosphorylation of CREB. These observations show that temporal features of action potentials (and associated Ca2+ transients) regulate expression of neuronal genes by activating specific intracellular signaling pathways with appropriate temporal dynamics.

Action Potentials↗
PubMed1997

Efficacy and safety of lidocaine-prilocaine cream for pain during circumcision.

BACKGROUND: Neonatal circumcision is a painful surgical procedure often performed without analgesia. We assessed the efficacy and safety of 5 percent lidocaine-prilocaine cream (Emla) in neonates undergoing circumcision. METHODS: We carried out a double-blind, randomized, controlled trial in 68 full-term male neonates: 38 were assigned to receive lidocaine-prilocaine cream, and 30 to receive placebo. One gram of lidocaine-prilocaine or placebo cream was applied to the penis under an occlusive dressing for 60 to 80 minutes before circumcision. Behavioral (facial activity and time spent crying) and physiologic (heart rate and blood pressure) responses were recorded during the procedure. Blood samples were obtained at various times after drug application for measurements of methemoglobin and plasma lidocaine, prilocaine, and o-toluidine (a metabolite of prilocaine). RESULTS: A total of 68 and 59 neonates were included in the safety and efficacy analyses, respectively. Demographic characteristics such as gestational age and birth weight did not differ between the lidocaine-prilocaine and placebo groups. During circumcision, the neonates in the lidocaine-prilocaine group had less facial activity (P= 0.01), spent less time crying (P<0.001), and had smaller increases in heart rate (P=0.007) than the neonates in the placebo group. Facial-activity scores were 12 to 49 percent lower during various steps of the procedure in the lidocaine-prilocaine group. As compared with neonates in the placebo group, infants in the lidocaine-prilocaine group cried less than half as much and had heart-rate increases of 10 beats per minute less. Blood methemoglobin concentrations (expressed as a percentage of the hemoglobin concentration) were similar (1.3 percent) in both groups. Lidocaine and prilocaine were detected in plasma in 23 (61 percent) and 21 (55 percent) of the infants treated with lidocaine-prilocaine cream, respectively. CONCLUSIONS: Lidocaine-prilocaine cream is efficacious and safe for the prevention of pain from circumcision in neonates.

Anesthesia, Local↗
PubMed1997

The efficacy of sucrose for relieving procedural pain in neonates--a systematic review and meta-analysis.

The objective was to determine the efficacy and optimal dose of sucrose for relieving procedural pain in neonates. Data were obtained using MEDLINE, EMBASE, Reference Update and personal files and assessed for quality of the methods. Data from all randomized controlled trials where term and preterm neonates received a heelstick or venipuncture were examined for the efficacy of different sucrose doses (0.18 g, 0.24 g, 0.48 g or 0.50 g, 1.0 g) and water (placebo). The primary outcome was the proportion of time crying during 3 min after the painful stimulus. Data were combined across studies using a random effects model, adapted for use with single groups, producing a point estimate and 95% confidence interval (CI). Thirteen trials were identified; eight were rejected as data were inappropriate, non-extractable, or the primary outcome was not measured. Five studies provided data on 271 infants. The proportion of time crying did not differ between 0.18 g of sucrose and water (p > 0.05) but was significantly lower in all other sucrose groups. There were no differences in proportion of time crying between term and preterm neonates. Sucrose reduced the proportion of time crying during painful procedures in neonates. The 0.18 g dose of sucrose was ineffective. Doses of 0.24 g (2 ml of 12% sucrose solution) were most effective. A dose of 0.50 g provided no additional benefit.

Analgesics↗
PubMed1996

Premature Infant Pain Profile: development and initial validation.

OBJECTIVE: Inadequate assessment of pain in premature infants is a persistent clinical problem. The objective of this research was to develop and validate a measure for assessing pain in premature infants that could be used by both clinicians and researchers. DESIGN: The Premature Infant Pain Profile (PIPP) was developed and validated using a prospective and retrospective design. Indicators of pain were identified from clinical experts and the literature. Indicators were retrospectively tested using four existing data sets. PATIENTS AND SETTINGS: Infants of varying gestational ages undergoing different painful procedures from three different settings were utilized to develop and validate the measure. METHODS AND RESULTS: The largest data set (n = 124) was used to develop the PIPP. The development process included determining the factor structure of the data, developing indicators and indicator scales and establishing internal consistency. The remaining three data sets were utilized to establish beginning construct validity. CONCLUSIONS: The PIPP is a newly developed pain assessment measure for premature infants with beginning content and construct validity. The practicality and feasibility for using the PIPP in clinical practice will be determined in prospective research in the clinical setting.

Gestational Age↗
PubMed1996

Management of painful procedures in the newborn.

Management of painful procedures in the neonate is less than optimal. Although evidence exists to support the infant's capacity to feel pain at birth, health professionals do not prescribe or administer adequate analgesia. This is largely because of the lack of published data on the safety and efficacy of pharmacologic interventions and lack of sufficient understanding of the benefits of nonpharmacologic measures. In this review, recent research on the safety and efficacy of pharmacologic and nonpharmacologic interventions for managing painful procedures in the neonate is summarized.

Analgesics↗
PubMed1996

Developmental changes in response to heelstick in preterm infants: a prospective cohort study.

Twenty-eight preterm infants of 28 weeks gestational age were observed four times over eight weeks in order to determine changes in their pain response. Both routine and sham heelstick procedures were used. Physiological (heart rate and oxygen saturations) and behavioural parameters (three upper facial actions) were used as outcomes. The responses to real heelstick were significantly greater than to sham heelstick for heart rate and all facial actions except one at 28 weeks gestational age, but not for oxygen saturation. The magnitude of response to both real and sham heelstick increased over time. Thus, the older the infant, the more robust and recognisable the response. Since even the youngest infants showed a differential response to pain, professionals caring for such infants need to be able to recognize their more subtle pain responses.

Child Development↗
PubMed1996

Pain management in newborns: how far have we progressed in research and practice?

Compelling research supports the newborn infant's capacity for pain. Yet, pain is frequently underestimated and undertreated. This is a result of limited understanding of pain pathway development, immediate and long-term consequences, measurement tools and approaches, and safety and efficacy of pain-relieving interventions. This paper reviews recent research in relation to management of pain in the newborn, and presents implications for practice and future research.

Female↗