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Biomedical subjects

L M Lewis

Publications and source records attributed to L M Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1992

Gender bias in the evaluation and management of acute nontraumatic chest pain. The St. Louis Emergency Physicians' Association Research Group.

BACKGROUND: Prior studies suggest a gender-based difference in the management of myocardial ischemia in nonacute settings. We examined whether there was a gender difference in the emergency department evaluation and management of patients with acute chest pain. METHODS: A record review from 10 St. Louis metropolitan emergency departments was done on all patients over 35 years old who presented with acute nonpleuritic, nontraumatic chest pain. We reviewed for the presence of cardiac risk factors, prior cardiac disease, time to physician evaluation, and time to initial electrocardiogram. In the patient subgroup admitted from the emergency department with a diagnosis of myocardial infarction or unstable angina, disposition was noted. RESULTS: Women waited longer than men for an initial physician evaluation and an initial electrocardiogram. In the patient subgroup with acute myocardial ischemia, a smaller percentage of women than men (56.0% vs 82.8%) were admitted to an intensive care unit. CONCLUSION: In patients with acute nonpleuritic, nontraumatic chest pain, women were evaluated and managed less aggressively than men.

Acute Disease↗
PubMed1991

Flexion-extension views in the evaluation of cervical-spine injuries.

STUDY OBJECTIVE: To determine the efficacy of flexion-extension (F/E) cervical-spine radiographs in detecting acute cervical-spine instability in emergency patients. DESIGN: We retrospectively reviewed the charts of 141 consecutive trauma patients who had F/E views performed after a routine cervical-spine series (three views) was obtained in the emergency department. Interpretations of the routine series were compared with those of the F/E views to determine if additional useful information was provided by the latter. The charts also were reviewed to determine if any variables were associated with an increased use of F/E views, an increased likelihood of these views demonstrating instability, or any neurologic sequelae resulted from these studies. SETTING: An urban Level I adult trauma center. MEASUREMENTS: The interpretations of the routine series were noted to be either normal, abnormal but without demonstrable fracture/dislocation, or demonstrating a fracture/dislocation. The F/E views were categorized as stable, unstable, or uninterpretable. RESULTS: Cervical-spine instability was demonstrated by F/E views in 11 of the 141 patients (8%), four of whom had normal routine cervical-spine films. Three of these four patients required surgical stabilization. Prolonged neck pain (more than 24 hours), an initially abnormal spine series, and a neurosurgical consult were all associated with an increased use of F/E views. Ten of 11 patients with radiographic instability had significant neck pain by history; the remaining patient was intoxicated. No neurologic sequelae resulted from performing F/E studies. There was one false-negative F/E study, which raises concern about the reliability of this procedure in the ED. CONCLUSION: We believe that a large prospective study is required to determine which patients warrant F/E views.

Adult↗
PubMed1990

A comparison of transcranial Doppler ultrasound (TCD) and radioactive microspheres in determining cerebral perfusion in normal and low flow states.

We have previously utilized the technique of transcranial Doppler (TCD) ultrasound to determine cerebral perfusion in patients undergoing cardiopulmonary resuscitation (CPR). In order to assess if TCD can reliably measure alterations in cerebral perfusion under conditions of normal and low cardiac outputs, we compared TCD measured blood flow velocities in the middle cerebral artery (MCA) of six piglets with radioactive microsphere determinations of total cerebral perfusion at baseline normal sinus rhythm (NSR), during CPR, and following return of spontaneous circulation (ROSC). Peak systolic and mean blood flow velocities were compared to the microsphere perfusion results on 15 different occasions; six during NSR, five during CPR, and four following ROSC. Although qualitative alterations in TCD measurements reflected changes in microsphere perfusion, we could not find a statistically significant correlation between either peak systolic or mean MCA blood flow velocities and microsphere perfusion measurements either overall or in any subgroup. The possible reasons which may explain the findings are discussed.

Animals↗
PubMed1990

Is emergency department resuscitation of out-of-hospital cardiac arrest victims who arrive pulseless worthwhile?

It is still a common practice to continue unsuccessful field resuscitations in the emergency department (ED) even after prolonged estimated down times. The authors studied patients who arrested in the field and did not regain a pulse before their arrival in the ED to determine if any ever leave the hospital neurologically intact. All cardiac arrests in the urban St Louis area that were brought to our facility over a 2 1/2-year period by advanced life support units (excluding all patients with hypothermia, drug overdose, near drowning, and traumatic cardiac arrest) were reviewed. Of 243 such patients 32 (13%) arrived with a pulse. Twenty-three of these patients were admitted and 10 discharged alive, 7 were neurologically intact. Out of 211 patients who arrived without a pulse, 24 (11%) developed a pulse with further resuscitative efforts in the ED. Eighteen of these patients were admitted but only one was discharged neurologically intact. The only survivor in the group without a pulse arrested while en route to the ED. It is concluded that cardiac arrest victims who arrive in the ED without a pulse on arrival or en route have almost no chance of functional recovery.

Aged↗
PubMed1990

High pressure percutaneous transtracheal ventilation: the use of large gauge intravenous-type catheters in the totally obstructed airway.

Percutaneous transtracheal ventilation using a large gauge intravenous-type catheter can be used successfully in the setting of complete upper airway obstruction in animals. In this study, using a large animal model, satisfactory oxygenation and ventilation was achieved by inversely varying the catheter size and the inspiration to expiration ratio (I:E). Specifically, 30 to 63 kg ruminants with an obstructed upper airway were resuscitated for 30 minutes from a hypoxic, hypercarbic, and acidotic state using 12- and 14-gauge catheters connected to a 50 psi oxygen source via a two-way valve with an I:E of 1:4 and 1:9 seconds, respectively. Shorter expiratory time or increased inspiratory time with these intravenous catheters resulted in significant hemodynamic compromise, barotrauma, inadequate carbon dioxide elimination, acidemia, and frequent death.

Airway Obstruction↗
PubMed1990

Transcranial Doppler determination of cerebral perfusion in patients undergoing CPR: methodology and preliminary findings.

STUDY OBJECTIVES: To correlate cerebral arterial blood velocity measurements as determined by transcranial Doppler ultrasound with various resuscitation maneuvers performed in an uncontrolled manner in a series of cardiac arrest patients undergoing standard resuscitation. TYPE OF PARTICIPANTS: Any patient undergoing resuscitation for a nontraumatic cardiac arrest was eligible for the study. INTERVENTIONS: Resuscitation was carried out while flow velocities were monitored in various intracranial arteries by transcranial Doppler ultrasound. Vessel identification was based on the angle and depth of insonation. MEASUREMENTS AND MAIN RESULTS: The internal carotid artery was located more consistently than either middle cerebral or ophthalmic arteries and provided superior waveforms for analysis. Alterations in flow velocity were noted and correlated to various therapeutic interventions. Flow velocities were 70% of normal during the early phase of resuscitation but deteriorated over time until there was no evidence of net forward flow. Even early in CPR, flow was demonstrated only during systole. CONCLUSION: Transcranial Doppler ultrasound appears to be a potentially promising means of determining cerebral flow in patients undergoing CPR.

Brain↗
PubMed1990

Early detection of acute myocardial infarction in patients presenting with chest pain and nondiagnostic ECGs: serial CK-MB sampling in the emergency department.

STUDY OBJECTIVES: Patients presenting to the emergency department with chest discomfort are a difficult problem for emergency physicians. Nearly 50% of patients with acute myocardial infarction (AMI) will initially have nondiagnostic ECGs on ED presentation. The purpose of this study was to determine if patients with AMI having nondiagnostic ECGs could be identified using new immunochemical assays for serial CK-MB sampling in the ED. DESIGN: Chest pain patients, more than 30 years old, with pain not caused by trauma or explained by radiographic findings, were eligible for the study. Serial serum samples were drawn on ED presentation (zero hours) and three hours after presentation, then analyzed for CK-MB using four immunochemical methods and electrophoresis. Standard World Health Organization criteria were used to establish the diagnosis of AMI, including new Q-wave formation or elevation of standard in-hospital serum cardiac enzyme markers. SETTING: A tertiary cardiac care community hospital. MEASUREMENTS AND MAIN RESULTS: The serum from 183 patients hospitalized for possible ischemic chest pain was collected and analyzed. Thirty-one of 183 patients (17%) were found to have AMI by standard in-hospital criteria. Sixteen of the 31 patients (52%) with AMI had nondiagnostic ECGs on presentation. Immunochemical determination of serial CK-MB levels provided a sensitive and specific method for detecting AMI in patients within three hours after ED presentation compared with standard electrophoresis. The four immunochemical methods demonstrated a range in sensitivity from 50% to 62.1% on ED presentation versus 92% to 96.7% three hours later. The immunochemical tests demonstrated specificities ranging from 83.0% to 96.4% at three hours, with three of the four tests having specificities of 92% or greater. Electrophoresis had a sensitivity of 34.5% on ED presentation, increasing to 76.9% at three hours, with a specificity of 98.6%. CONCLUSIONS: Immunochemical CK-MB methods allowed rapid, sensitive detection of AMI in the ED. Early detection of AMI offers many potential advantages to the emergency physician. Early detection of AMI, while the patient is in the ED, could direct disposition of this potentially unstable patient to an intensive care setting. Such information may prevent the ED discharge of patients with AMI having nondiagnostic ECGs. The diagnosis of AMI within a six-hour period after symptom onset may allow thrombolytic therapy to be given to patients with AMI not having diagnostic ECGs. This study served as a pilot trial for a multicenter study of the Emergency Medicine Cardiac Research Group, which is currently ongoing.

Adult↗
PubMed1989

The effect of varying extents of Fluosol-DA or normal saline haemodilution on the dose dependent kinetics of phenytoin in the rat.

Phenytoin kinetics were determined in rats in which the blood was moderately haemodiluted with 20 or 40 mL kg-1 of Fluosol-DA or normal saline. Rats received one of three intravenous phenytoin doses (10, 40, 50 mg kg-1) 0.5, 24, 48, or 72 h after haemodilution and were compared with non-exchanged controls. Haemodilution with either 20 or 40 mL kg-1 of Fluosol or saline had no influence on the dose-dependent kinetics of phenytoin. Haemodilution with 40 mL kg-1 of Fluosol decreased the half-life of phenytoin's major metabolite, HPPH, after a 50 mg kg-1 dose. Neither Fluosol nor saline haemodilution affected the normal delay in biliary cycling of HPPH.

Animals↗
PubMed1988

Respiratory-dependent pacing: a dual response from a single sensor.

Five patients with respiratory dependent rate responsive pacemakers (Biorate RDP3, Biotec) were studied using ambulatory telemetry to evaluate the sensitivity of this pacing system to nonrespiratory signals. In each case the pacemaker was implanted in the left infraclavicular position with an impedance sensing electrode inserted into the subcutaneous tissues of the anterior chest wall. The pacing rate was 73 +/- 2 beats per minute at rest and rose by 42 +/- 5 beats per minute when the patients were walking with both arms swinging (mean +/- SEM). Three of the five patients had sensing electrodes that extended across the midline. In this subgroup, pacing rate rose by 26 +/- 4 beats per minute when walking with arms held immobile and by 36 +/- 2 beats per minute during sustained voluntary hyperventilation. These same activities did not elicit any appreciable changes in pacing rate in the remaining two patients whose sensing electrodes were confined to the left hemithorax. Recordings taken from all five patients while they were standing upright and regularly swinging one upper limb showed an increase in pacing rate of 15 + 6 beats per minute with movement of the right arm and 46 + 8 with movement of the left. These observations establish that the Biorate RDP3 pacemaker is capable of responding both to changes in respiratory rate and to movement of the upper limbs. The sensitivity to limb movement is greatest when the chest wall impedance sensor does not extend across the midline and is most evident when the arm ipsilateral to the pacemaker is swung.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

The effect of varying percentages of haemodilution with fluosol-DA or normal saline on antipyrine metabolism in the rat.

Antipyrine disposition and metabolism in conscious, unrestrained rats after 25 or 50% haemodilution with Fluosol or normal (0.9% NaCl) saline is reported. Rats received an intravenous antipyrine dose (20 mg kg-1) 0.5, 24, 48, or 72 h after haemodilution and its pharmacokinetic parameters have been compared with non-exchanged control animals. Haemodilution 25% with Fluosol initially depressed antipyrine metabolism for 24 h by decreasing the antipyrine urinary excretion rate constant and the formation rate constants of 4-hydroxyantipyrine (4-OH) and 3-hydroxymethylantipyrine (3-OHME). Metabolism was then increased for 48 and 72 h with a slight increase in all rate constants. Haemodilution 50% with Fluosol produced a similar pattern but with significant increases in the 3-OHME formation rate constant found at 48 and 72 h. Haemodilution 25% with saline reduced 4-OH formation for 48 h. Haemodilution 50% with saline significantly reduced antipyrine urinary excretion at all times. After a significant increase in the 4-OH and 3-OHME formation rate constants at 24 h following 50% haemodilution with saline, the rate constants were significantly decreased at 48 and 72 h. Haemodilution 25% with Flusol significantly reduced the antipyrine Vd at 0.5 and 72 h. After haemodilution 50% with Fluosol, the Vd alternated between values greater and less than control throughout the 72 h. Haemodilution 25 or 50% with saline had little influence on Vd.

Animals↗
PubMed1987

Effect of moderate haemodilution with Fluosol-DA or normal saline on low-dose phenytoin and (+/-)-5-(4-hydroxyphenyl)-5-phenylhydantoin kinetics.

Phenytoin kinetics were determined in the rat following moderate (50%) blood exchange with either Fluosol-DA or normal saline. Rats received an intravenous phenytoin dose (10 mg kg-1) 0.5, 24, 48, or 72 h after exchange and were compared with non-exchanged controls. Phenytoin t 1/2 was not altered by exchange with either fluid. Its Cl and Vd were decreased and AUC increased 24, 48, and 72 h after saline exchange and 24 h after Fluosol-DA exchange. (+/-)-5-(4-Hydroxyphenyl)-5-phenylhydantoin (HPPH), a major metabolite of phenytoin, showed a decreased t1/2 and VHPPH 24, 48, and 72 h after exchange with either fluid; t1/2 was also reduced 0.5 h after Fluosol-DA exchange. The decreased Vd and VHPPH may result from changes in cardiac output secondary to haemodilution, or may represent a redistribution in the microcirculation. Fluosol-DA appears to enhance phenytoin and HPPH metabolism 48 and 72 h after exchange.

Animals↗
PubMed1987

Effect of moderate haemodilution with Fluosol-DA or normal saline on indocyanine green and (+)-propranolol kinetics.

Indocyanine green (ICG) and (+)-propranolol kinetics were determined in the rat following moderate (50%) blood exchange with either Fluosol-DA or 0.9% NaCl (saline). Rats received an intravenous ICG dose (5 mg kg-1) before an intravenous dose of (+)-propranolol (2.5 mg kg-1) 0.5, 24, 48 or 72 h after haemodilution and were compared with non-exchanged controls. Haemodilution with Fluosol-DA reduced the ICG elimination rate constant during the first 24 h while a significant reduction was seen 48 h after normal saline exchange. ICG clearances tended to be less than the control value, and were significantly reduced only at 24 h after Fluosol-DA exchange due to a reduced Varea. (+)-Propranolol half-life was significantly increased 48 and 72 h after saline exchange; (+)-propranolol clearance was also significantly reduced 72 h after Fluosol-DA exchange. ICG clearance may be reflecting a hypovolaemic change which occurs after haemodilution, which would reduce the hepatic blood flow. However, (+)-propranolol clearance was not altered, suggesting that the hepatic blood flow is not changed. It is possible that ICG clearance is changed due to alterations in its extraction ratio instead of hepatic blood flow changes.

Animals↗
PubMed1978

Bis(2-ethylhexyl)phthalate concentrations in the serum of hemodialysis patients.

Bis(2-ethylhexyl) phthalate is extracted from artificial kidneys, both in vivo and in vitro. Perfusion of whole blood through arterial-,venous tubing (that supplied with the dialyzer) for 1 h in vitro yielded 3.23 mg of the compound, while similar perfusion of the tubing plus the artificial kidney yielded 6.10 mg. Its mean concentration after dialysis in patients undergoing hemodialysis was 751 microgram/liter of serum. Patients who had undergone more than 50 hemodialysis treatments showed significantly higher postdialysis concentrations than patients who had undergone fewer. Uptake of bis(2-ethylhexyl) phthalate by the blood during a dialysis session followed two patterns. One set of patients showed a maximum concentration at 3 h, the second set showed a steady increase until the end of dialysis. Bis(2-ethylhexyl) phthalate appeared to be rapidly cleared from blood, most being removed within 5 to 7 h of completion of dialysis.

Chromatography, Gas↗
PubMed1977

Determination of plasticizer levels in serum of hemodialysis patients.

Serum DEHP levels were measured on 27 hemodialysis patients at various time intervals. The following results were obtained: 1) Predialysis levels of DEHP occurred in only one of 22 samples. 2) Postdialysis serum levels reached a mean of 751 nGm DEHP/ml serum. 3) Samples from patients with less than 50 hemodialysis treatments gave a mean of 558 nGm/ml, while those with more than 50 treatments gave a mean of 973 nGM/ml. These numbers were found to be significantly different at a 95% confidence level. 4) No difference in DEHP levels were found for males and females. 5) The appearance of DEHP during dialysis and its disappearance after dialysis were found to be biphasic. 6) No correlation was found between serum DEHP and triglyceride levels in postdialysis serum samples.

Female↗
PubMed1975

The evolutionary significance of ultrastructural variations in the micronuclear spindle apparatus in the genus Paramecium.

Ultrastructural variations of micronuclear mitosis in three species of Paramecium have been reviewed for the purpose of hypothesizing possible evolutionary relationships. P. bursaria is considered to be the most primitive species because it has complex kinetochore-equivalents termed microlamellae which attach to microfilaments. P. multimicronucleatum is considered more advanced since it has typical kinetochores which intercalate between the kinetochores and polar microfilaments. P. aurelia is considered the most advanced member of the genus, and has typical diffuse or well defined kinetochores and chromosomal microtubules while it lacks obvious meshworks of microfilaments. A hypothetical model of chromosome movement in the genus involves the interaction of microtubules and microfilaments.

Animals↗
PubMedDate not supplied

Managing panic attacks in emergency patients.

Patients experiencing panic attacks often seek help at emergency departments. However, the symptoms of panic can be difficult to distinguish from some common medical emergencies. Furthermore, many emergency medicine clinicians may not be equipped to deal effectively with panic attacks and related psychiatric conditions such as panic disorder and agoraphobia. Early misdiagnosis and inadequate management of panic attacks can have devastating long-term clinical and financial consequences. The purpose of this paper is to provide information designed to increase the comfort and efficacy of emergency physicians and allied professionals in dealing with panic attacks. The authors offer guidelines regarding differential diagnosis, present strategies for management of acute symptoms of panic and anxiety, and make recommendations for brief postpanic clinical intervention.

Anxiety Disorders↗