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Biomedical subjects

R S Porter

Publications and source records attributed to R S Porter.

At least 19 recordsLinked to original sources
PubMed2001

A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment for crotaline snakebite in the United States.

BACKGROUND: Current therapy for crotaline snakebite includes antivenin (Crotalidae) polyvalent, an antivenom with numerous adverse effects. We compared the efficacy and safety of 2 dosing regimens with a new antivenom, Crotalinae polyvalent immune Fab (Fab AV). METHODS: A single dose of Fab AV alone (as-needed [PRN] group) was compared with an initial dose plus repeated treatments during 18 hours (scheduled group) in a multicenter randomized trial. The study included patients with minimal or moderate envenomation by a crotaline snake within the preceding 6 hours, aged 10 years or older, in whom worsening of the envenomation syndrome was observed before Fab AV treatment. After treatment with Fab AV to achieve initial control, patients were randomized to the scheduled or PRN treatment group. Scheduled group patients received additional doses of Fab AV every 6 hours for 3 doses. The PRN group received no planned additional doses of antivenom. RESULTS: The mean severity score of the 31 patients decreased from 4.35 to 2.39 points (P<.001); there was no difference between scheduled and PRN groups. No patient in the scheduled group received unplanned Fab AV doses, but 8 of 16 patients in the PRN group received unplanned doses (P =.002). Acute reactions occurred in 6 patients (19%), and serum sickness occurred in 6 (23%) of 26 patients who returned for follow-up. CONCLUSIONS: In the first randomized trial of antivenom in the United States, Fab AV effectively terminated venom effects. Since the unplanned use of Fab AV in the PRN group was common, the treatment regimen may require more than 1 initial dose.

Adolescent↗
PubMed2001

Intravenous magnesium is ineffective in adult asthma, a randomized trial.

Intravenous magnesium sulphate (MgSO4) has been tried in the emergency department treatment of asthma since the mid-1980s, but published reports vary as to its efficacy. The literature suggests that it may be effective in the more severely ill asthmatic. We evaluated i.v. MgSO4 in adult asthmatics having a moderate to severe exacerbation. The study was performed in a convenience sample of adult asthmatics between the ages of 18 and 55 presenting to the emergency department with a peak expiratory flow (PEF) of < 100 l/min or < 25% of predicted flow. Patients received either 2.0 grams of MgSO4 or placebo in a randomized, double-blind fashion. All patients received inhaled bronchodilators and i.v. steroids. Outcome variables were: improvement in PEF, subjective respiratory distress as measured by the Borg dyspnoea scale (BDS) and hospital admission. The first visits of 42 patients presenting with acute asthma exacerbations were evaluated, 18 receiving MgSO4 and 24 receiving placebo. The t = 60 peak flow in the MgSO4 group was 174 l/min versus 212 l/min in placebo, p = 0.04. Controlling for age, heart rate, initial PEF and initial BDS in ordinal logistic regression, the t = 60 Borg scale of subjective dyspnoea had an odds ratio of 1.54 in favour of more dyspnoea in MgSO4 (95% C.I., 0.36-6.67; p = 0.56). Five of 18 patients (28%) receiving MgSO4 were admitted compared with 5 of 24 (21%) receiving placebo (p = 0.72). In moderately severe adult asthmatics, 2.0 grams of MgSO4 i.v. resulted in less improvement in peak expiratory flow compared with placebo. MgSO4 did not appear to decrease subjective dyspnoea or the hospital admission rate. This evidence does not support the use of MgSO4 in the treatment of acute asthma.

Adolescent↗
PubMed2001

Prediction of hyperkalemia in dogs from electrocardiographic parameters using an artificial neural network.

OBJECTIVE: To predict severe hyperkalemia from single electrocardiogram (ECG) tracings. METHODS: Ten conditioned dogs each underwent this protocol three times: Under isoflurane anesthesia, 2 mEq/kg/hr of potassium chloride was given intravenously until P-waves were absent from the ECG and ventricular rates decreased > or =20% in < or =5 minutes. Serum potassium levels (K(+)) were measured at regular intervals with concurrent digital storage of lead II of the surface ECG. A three-layer artificial neural network with four hidden nodes was trained to predict K(+) from 15 separate elements of corresponding ECG data. Data were divided into a training set and a test set. Sensitivity, specificity, and diagnostic accuracy for recognizing hyperkalemia were calculated for the test set based on a prospectively defined K(+) = 7.5. RESULTS: The model produced data for 189 events; 139 were placed in the training set and 50 in the test set. The test set had 37 potassium levels at or above 7.5 mmol/L. The neural network had a sensitivity of 89% (95% CI = 75% to 97%) and a specificity of 77% (95% CI = 46% to 95%) in recognizing these. The positive likelihood ratio was 3.87. Overall accuracy of this model was 86% (95% CI = 73% to 94%). Mean (+/-SD) difference between predicted and actual K(+) values was 0.4 +/- 2.0 (95% CI = -0.2 to 1.0). CONCLUSIONS: An artificial neural network can accurately diagnose experimental hyperkalemia using ECG parameters. Further work could potentially demonstrate its usefulness in bedside diagnosis of human subjects.

Animals↗
PubMed2000

Diagnosis and treatment of pediatric fever by caretakers.

Assessment of pediatric temperature is a multistep task involving both manipulative and cognitive skills. Emergency Physicians typically assume that parents possess these skills, but this assumption has never been fully tested. A prospective survey was conducted of caretakers of children < or = 36 months of age presenting to an inner city emergency department or pediatric clinic. Participants were asked to read a Fahrenheit scale mercury thermometer and to demonstrate use of that thermometer to "take" the temperature of an infant doll. They were then asked what temperature constituted a "fever" and what temperature would require antipyretic therapy. Caretakers were also asked how they would treat a fever in the child they had brought for treatment. Proportions of correct responses were tabulated and also compared by age and level of education of caretaker. Eighty-two of 92 caretakers (89.1%) possessed working thermometers in their homes. Thirty-six subjects (39.1%) were able to measure temperature appropriately using the mercury thermometer, 52 (56.5%) were able to read the mercury thermometer correctly, and 28 (30.4%) could both measure and read correctly. Sixty-seven subjects (72.8%) described correct treatment of fever. Overall, 27 subjects (29.3%) could measure, read, and treat fever appropriately. There was no statistically significant difference in age or percentage of high school graduates between caretakers who could successfully measure, read and treat and those who could not. In this inner city patient population, caretakers of any pediatric patient whose discharge instructions contain a reference to patient temperature should receive a brief refresher along with written instructions on temperature measurement and treatment.

Adult↗
PubMed2000

Alcohol and injury in adolescents.

OBJECTIVE: To determine the frequency of alcohol ingestion in adolescent victims of major trauma and determine whether alcohol ingestion is associated with increased injury severity or death. METHODS: Subjects were all patients between 12-25 years of age treated at Pennsylvania trauma centers in 1996 who were reported to the state trauma database. Data on age, mechanism of injury (E-code), blood alcohol concentration (BAC), Injury Severity Score (ISS), and survival were obtained from the state database. BAC positive and negative patients within three groups: ages 12-17, 18-20, and 21-25, were compared to determine any difference in death rate, injury severity or type of injury. RESULTS: 4309 patients aged 12-25 were reported to the state in 1996. 2724 (63.2%) underwent testing for BAC, with 884 (32.5%) of those tested being positive. Testing positive were: 93/726 (12.8%) between 12-17 years old, 249/844 (29.5%) between 18-20 years old, and 542/1154 (47.0%) between 21-25 years old. 567/884 (64.1%) of those testing positive had BAC > or = 100 mg/dl. There were no statistically significant differences in mean ISS or death rate between BAC negative and BAC positive patients in either of the age groups. Regression analysis also showed no relationship between mortality and either the presence of alcohol or the actual level of BAC. Other regression analysis demonstrated a slight downward trend for ISS with increasing intoxication, which was statistically significant at P < 0.01. CONCLUSIONS: Alcohol ingestion is found even in early adolescent trauma patients and is seen to increase throughout the teenage years, occurring in over one-quarter of patients 18 to 20 years of age. Suspicion must be high that ingestion of alcohol has occurred in adolescent trauma. Further efforts should be made to improve the rate of testing in late adolescents, to ensure adequate identification of all alcohol-exposed patients and enable educational interventions. No significant differences in mortality were seen between alcohol positive and negative patients, but there was a trend to decreased injury severity with the presence of alcohol.

Adolescent↗
PubMed1999

Polyclonal anti-tumor necrosis factor-alpha Fab used as an ancillary treatment for severe malaria.

Single doses (250, 500, 1,000, or 2,000 units/kg) of an ovine polyclonal-specific Fab fragment directed against tumor necrosis factor-alpha (TNF-alpha) were given to 17 adult patients with severe falciparum malaria immediately before treatment with artesunate in a pilot study to assess safety and optimal dosage with a view to future studies. Clinical and laboratory variables were compared with 11 controls. In the groups given Fab, there was a tendency for a faster resolution of clinical manifestations and reduction of fever but also a tendency towards longer parasite clearance times. Adverse events were more common in the control group and no early anaphylactic or late serum sickness reactions occurred in the Fab treated patients. On admission all patients had markedly elevated levels of TNF-alpha (85-1,532 ng/L) and interleukin-6 (IL-6) (30-27,500 ng/L). Also, 86% had elevated interferon-gamma (IFN-gamma) levels, 75% had increased IL-2 levels, 36% had increased IL-8 levels, and 21% had increased IL-1beta levels. Antibody treatment reduced IFN-gamma concentrations in a dose-related manner, but had no obvious effects on levels of other cytokines in this small study, although unbound TNF-alpha was undetectable after Fab treatment. Circulating concentrations of soluble E-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were not affected by Fab treatment. The Fab exhibited a two-compartment, dose-proportional kinetics with an average elimination half-life of 12.0 hr, with about 20% being excreted renally. These results encourage a randomized, placebo-controlled trial in patients with cerebral malaria and provide some guidance about dosage.

Adolescent↗
PubMed1998

Patterns of injury in belted and unbelted individuals presenting to a trauma center after motor vehicle crash: seat belt syndrome revisited.

STUDY OBJECTIVE: Investigators have described a "seat belt syndrome" consisting variously of injuries to the lumbar or cervical spine, abdominal contents, or all 3. In this study we sought to identify these and any other patterns of injury associated with seat belt use in patients who presented to a trauma center after a motor vehicle crash. METHODS: The charts of all patients involved in motor vehicle crashes who presented as trauma alerts to the study institution between January 1, 1991, and December 31, 1993, were retrospectively reviewed for data regarding belt use and 35 specific injuries in 7 body regions. We calculated the positive likelihood ratio of injury between belted and unbelted patients, along with 95% confidence intervals. RESULTS: We identified 1,124 patients involved in motor vehicle crashes. Of these subjects, 376 were belted and 544 unbelted; in 204 belt status was unknown. Belted patients were more likely to have sustained sternal fracture than were unbelted patients (4% versus .7%; positive likelihood ratio, 1.97; 95% confidence interval, 1.09 to 3.29) but were less likely to have sustained head injury (30.6% versus 46.0%; positive likelihood ratio, .67; 95% confidence interval, .53 to .83). We noted no statistically significant differences in the rates of other specific injuries, including cervical and lumbar fractures and the need for abdominal surgery. CONCLUSION: Severe injuries of all types occur in both belted and unbelted individuals involved in motor vehicle crashes who present to a typical trauma center. With the exception of sternal fractures, injuries previously associated with the seat belt syndrome occurred in similar proportions of belted and unbelted patients. Head injuries were less frequent. Seat belt use cannot serve as a discriminator for specific injury. A diligent search of all body regions is indicated in both belted and unbelted patients.

Abdominal Injuries↗
PubMed1997

Relationship of venom effects to venom antigen and antivenom serum concentrations in a patient with Crotalus atrox envenomation treated with a Fab antivenom.

STUDY OBJECTIVE: To describe the association among venom antigenemia, serum antivenom concentrations, and venom effects in a 53-year-old woman who was bitten by a Western Diamondback rattlesnake (Crotalus atrox). METHODS: The patient was enrolled in a multicenter trial of an investigational Fab antivenom. Her clinical condition and coagulation parameters were monitored for 2 weeks after the bite. RESULTS: After antivenom administration, the progression of the venom's effects was arrested. The antivenom reversed some local venom effects, caused venom antigens to disappear from the blood, and resolved the patient's profound thrombocytopenia (before antivenom, 12,000/mm3; 1 hour after antivenom, 227,000/mm3). Local venom effects recurred twice in the 24 hours after antivenom administration but were easily managed with additional Fab antivenom. Venom antigenemia was detected on days 5 and 8 after the initial treatment and was accompanied in one instance by the new onset of hypofibrinogenemia (119 mg/L) that resolved spontaneously and in both instances by renewed profound thrombocytopenia. Repeat Fab antivenom does no days 6 and 9 were followed by increases in platelet count (from 16,000 to 40,000/mm3 and from 11,000 to 20,000/mm3, respectively) and by the reduction or disappearance of venom antigenemia. The patient sustained no significant bleeding complications, and all laboratory values had returned to normal 2 weeks after the bite. CONCLUSION: Initial control of local symptoms and coagulopathy was prompt after the administration of Fab antivenom. Repeat doses during the 24 to 36 hours after a bite may be necessary for local control. Recrudescence of coagulopathy was likely due in part to renewed venom antigenemia after clearance of Fab antivenom. The role of Fab antivenom in the treatment of recurrent coagulopathy requires further study.

Adolescent↗
PubMed1997

Use of ultrasound to determine need for laparotomy in trauma patients.

STUDY OBJECTIVE: To determine whether abdominal ultrasound can be used routinely as the primary screening test to identify the need for laparotomy in trauma patients. METHODS: Ultrasound was used at a Level II trauma center as a primary screening test for evaluation of intraabdominal injury. We reviewed the charts of all patients from trauma codes presenting between January 1, 1991, and December 31, 1993, to determine the results of abdominal ultrasound evaluation and to learn whether laparotomy was required. RESULTS: A total of 2,013 trauma patients presented during the study interval. Ultrasound was performed in 1,631 patients as the primary screening test for abdominal injury (mean time after arrival, 22.9 minutes), abdominal computed tomography (CT) was performed as the primary screen on 8 (mean time, 68.6 minutes), and 93 patients underwent both ultrasound and CT of the abdomen. Of 86 patients requiring laparotomy who were screened by ultrasound, 80 had positive diagnostic findings, for a sensitivity of 93.0%. Of the 1,545 ultrasound-screened patients who did not require laparotomy, 1,390 had negative findings, for a specificity of 90.0%. None of the patients with negative ultrasound results died or sustained identifiable mortality as a consequence of their negative scans. CONCLUSION: Ultrasound is a sensitive and specific test with which to evaluate trauma patients for abdominal injury requiring surgery. Routine abdominal ultrasound can be performed at the bedside in the emergency department as a timely, noninvasive diagnostic test. This use of a screening abdominal ultrasound examination can improve clinical decision-making for the use of emergency laparotomy. Ultrasound may be a better alternative to CT or diagnostic peritoneal lavage for the initial screening evaluation of abdominal trauma.

Abdominal Injuries↗
PubMed1992

Encainide dosing in patients with severe renal dysfunction: report of a case and literature review.

Dosage of encainide for patients with lethal ventricular arrhythmias is based on pharmacodynamic effects and efficacy of arrhythmia suppression, coupled with metabolizer phenotype and extent of renal and hepatic dysfunction. Decreased clearance in patients with renal dysfunction necessitates a reduction in dosage to avoid toxic and dose-related proarrhythmic effects. This case represents a patient with severe renal dysfunction and sustained ventricular tachycardia who achieved electrophysiologically guided suppression of induced ventricular tachycardia at a steady-state encainide dose of only 25 mg daily, significantly lower than package insert or compendial recommendations for initial dosage in patients with renal insufficiency. Documented "therapeutic" metabolite concentrations correlated to electrophysiologic response. Literature review illustrates the complexity of encainide dosage in such individuals and underscores the need for therapeutic drug monitoring to individualize dosage.

Administration, Oral↗
PubMed1992

Hemodynamic and neurohumoral responses to intravenous nicorandil in congestive heart failure in humans.

Nicorandil is a vasodilator drug that combines potassium channel opening properties with nitrate effects. The resulting potent and unique vasodilating properties suggest a potential therapeutic role in congestive heart failure. We therefore studied the acute hemodynamic and neurohumoral responses to nicorandil, given as single intravenous bolus doses of 158, 251, 398, or 630 micrograms/kg, to 22 patients with chronic congestive heart failure (ejection fraction less than 40%). Hemodynamic responses occurred within 5 min of dosing and terminated within 240 min. The heart rate was significantly increased only at 5 min after the 158 micrograms/kg dose, and was unchanged after all other doses. The mean arterial pressure was reduced only by the 398 and 630 micrograms/kg doses. The pulmonary capillary wedge pressure and right atrial pressure were significantly reduced by all doses within the initial 30 min; this reduction in pulmonary capillary wedge pressure was better sustained over time by the two larger doses, whereas the reduction in right atrial pressure was sustained only by the 158 micrograms/kg dose. The cardiac index was reduced by the 158 micrograms/kg dose, but increased after 251, 398, and 630 micrograms/kg of nicorandil. Plasma nicorandil concentrations were positively correlated with changes in cardiac index, systemic arterial pressure, pulmonary capillary wedge pressure, heart rate, and systemic vascular resistance. When measured 1 h after dosing, plasma immunoreactive ANF decreased, norepinephrine concentrations did not change, and plasma renin activity increased, but only at the 630 micrograms/kg dose level.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Clinical pharmacology education in a division of cardiology.

A working model of how clinical pharmacology education can be interwoven into the matrix of an academic cardiology program that includes didactic teaching, clinical research, and patient care has been presented. Essential to the success of such a program is the commitment and dedication of both its full-time and voluntary faculty. Moreover, a comprehensive plan of organization and allocation of efforts is vital to the success of such a complex undertaking. As we look to the future, the discipline of clinical pharmacology will be increasingly relevant to the practicing cardiologist.

Cardiology↗
PubMed1991

Efficacy of computer-assisted instruction in the continuing education of paramedics.

STUDY OBJECTIVE: To determine the relative effectiveness of lecture, video, and computer-assisted instruction (CAI) for the continuing education of paramedics. DESIGN: The study was a statewide, cross-sectional, and prospective. It used premethod, post method and 60-day evaluations addressing both cognitive knowledge and attitude toward the method. Subjects were required to complete a 20-question cognitive examination and a ten-point satisfaction inventory. Each study site was randomly assigned a method by a computer-generated table. SETTING: The study involved 11 sites, systematically distributed throughout Michigan. TYPE OF PARTICIPANTS: 111 Michigan licensed paramedics. RESULTS: CAI subjects scored an average of 79.6% on the post-test, while lecture and video subjects scored 70.5% and 68.9%, respectively. At 60 days, CAI subjects scored 70.9%, while lecture and video subjects averaged 59.4 and 59.1, respectively. The difference among the scores was significant post method (P = .01) and at 60 days (P = .02). The subject method preference was lecture, video, and CAI premethod; lecture, CAI, and video immediately post method; and lecture, CAI, and video at 60 days. CONCLUSION: Although lecture was the preferred method, CAI was best able to impart knowledge and enhance participant knowledge retention.

Achievement↗
PubMed1991

Predicting pharmacodynamic response to tissue plasminogen activator: a preliminary report.

All thrombolytic agents have produced significant variation in clinical response (patency, reocclusion, bleeding) when administered in recommended doses in patients with myocardial infarction. We have evaluated the in vitro clot lysis response in 19 normal subjects and the pharmacodynamic response to tissue plasminogen activator (TPA) in 9 patients with myocardial infarction using a new, fresh, whole blood clot lysis system. Further, we have developed a Bayesian forecasting system for predicting response to TPA. Sensitivity to TPA (slope of the concentration/log response curve) varied significantly in patients with myocardial infarction (mean, 1.05 +/- 1.1). The mean clearance, volume of distribution, and half life were 55 +/- 13 L/h, 41 +/- 47 L, and 0.41 +/- 0.46 h. Using from zero to three clot lysis feedback times, the mean percentage mean absolute error varied from 65 to 16.4%. A relationship between mean clot lysis time and clinical reperfusion was established. Thus, a system for quantitating and predicting response to TPA was developed and successfully tested. Future extensive clinical trials will be necessary to evaluate fully the use of this system in clinical practice.

Bayes Theorem↗
PubMed1991

Chronic stability of bipolar epicardial plunge electrodes in dogs.

We constructed and surgically implanted 114 chronic bipolar epicardial plunge electrodes for programmed left ventricular stimulation in closed chest dogs; 88 electrodes could be analyzed in animals surviving infarct surgery. Electrode plunges were constructed of silver wire, with conduction strands of silver-plated copper wire, in medical grade silicone tubing. Electrodes were implanted epicardially through left thoracotomy and secured with prolene. Wires exited the fifth intercostal space and were tunneled subcutaneously and secured at the dorsal aspect of the neck. Baseline thresholds (mA) were recorded at a paced cycle length of 300 ms and pulse duration of 1 ms. At least 5 days after implantation, under light Nembutal sedation, thresholds were reassessed before programmed stimulation. Each lead was tested repeatedly over 5-177 (mean 28) days. The number of leads decreased with time due to animal attrition from ventricular arrhythmias. Mean pacing threshold at implantation was 0.25 mA. Mean and median threshold values reached plateau after 1 week and showed little change thereafter for the duration of the study. More than 50% of the leads maintained thresholds less than 1.5 mA through the entire study. In animals that survived, 86% of the electrodes remained useful for the duration of the protocol. These data support the use of this electrode system as effective and reliable for chronic electrophysiologic studies in dogs.

Animals↗
PubMed1991

Coronary artery thrombolysis: comparison of approved agents.

Three agents approved for the lysis of thrombi in coronary arteries--alteplase, anistreplase and streptokinase--have undergone critical clinical experimental trials in Europe and the United States. Global comparison of their efficacy shows that alteplase is slightly more effective (71 percent) in restoring patency than anistreplase (60 percent) and streptokinase (58 percent). Streptokinase and anistreplase are allergenic, and repeat administration is not feasible in the short-term, a distinct advantage for alteplase. More accurate dosing of thrombolytic agents and skillful use of aspirin and heparin improve the efficacy of thrombolytic therapy but can also increase the risk of bleeding. A recanalization rate of 90 percent or more could be achieved if the thrombolytic agent is administered within the first hour after thrombosis. Administration this soon after the development of thrombosis may be possible if the agent is given outside the hospital by practicing physicians or, perhaps, paramedics.

Anistreplase↗
PubMed1991

Thrombolysis for pulmonary embolism.

More than 10 years ago, thrombolytic therapy with urokinase and streptokinase for pulmonary embolism was found to have considerable advantages over standard heparin therapy. After the introduction of alteplase, a recombinant tissue plasminogen activator, further studies confirmed this benefit. However, thrombolytic therapy for pulmonary embolism has not gained universal acceptance, even though it now has U.S. Food and Drug Administration approval. Clear advantages of thrombolytic therapy over conventional heparin therapy are improved pulmonary capillary blood volume, accelerated clot lysis and accelerated pulmonary perfusion. Earlier reversal of right-sided heart failure, a lower incidence of recurrent pulmonary embolism, a reduced risk of chronic pulmonary hypertension and reduced mortality have been claimed as advantages, but these have not been adequately proved. A recent survey suggests that about half of all patients with pulmonary embolism are potential candidates for thrombolytic therapy. In a subset of patients with hemodynamic compromise, thrombolysis has definite advantages over heparin therapy.

Clinical Trials as Topic↗