Myocardial Contraction Fraction is not a Predictor of Clinical Outcomes in Acute Systolic Heart Failure: A Brief Report

Introduction

The utility of myocardial contraction fraction (MCF), a volumetric measure of myocardial shortening, has not been well evaluated in patients with systolic heart failure (SHF).

Materials and Methods

A single-center, retrospective cohort study of all adults admitted with acute SHF from 2013 to 2018 at an academic medical center. A chart review was performed to identify key echocardiographic transthoracic echocardiogram (TTE), laboratory, and demographic characteristics. MCF was calculated based on M-mode measurements of estimated stroke volume and myocardial volume based on admission TTE. The primary outcome was 30-day combined all-cause readmission/mortality and 365-day all-cause mortality.

Results

A total of 1282 patients were analyzed. The 30-day composite outcome occurred in 310 patients (24.2%), and all-cause death at 365 days occurred in 375 patients (29.3%). There was a weak correlation between the visually estimated ejection fraction (EF) and MCF (r = 0.356, P < 0.001). Neither MCF nor EF was associated with either component of the primary outcome. Other parameters on TTE that were associated with higher risk of primary outcome were higher tricuspid regurgitation (TR) velocity, larger left atrial (LA) diameter, and moderate or greater TR and mitral regurgitation (MR).

Conclusion

Echocardiographic predictors of postdischarge adverse events among patients hospitalized with acute SHF include higher TR velocity, larger LA diameter, and at least moderate MR or TR. MCF does not correlate well with visually assessed EF among patients with acute SHF, and neither MCF nor EF provides prognostic information in this population.

A Randomized Study of Intravenous Hydromorphone Versus Intravenous Acetaminophen for Older Adult Patients with Acute Severe Pain

STUDY OBJECTIVE

We conducted a randomized study to compare the efficacy and adverse event profile of 1,000 mg of intravenous acetaminophen to that of 0.5 mg of intravenous hydromorphone among patients aged 65 years or more with acute pain of severity that was sufficient enough to warrant intravenous opioids.

METHODS

This randomized comparative effectiveness study with 162 participants was conducted in 2 urban emergency departments (EDs). The primary outcome was an improvement in a 0 to 10 pain scale from baseline to 60 minutes later. Secondary outcomes included the need for additional analgesic medication and adverse events that were attributable to the investigational medication. The minimum clinically important difference was an improvement of 1.3 on the 0 to 10 pain scale.

RESULTS

The median baseline pain score was 10 (interquartile range 8 to 10) in both the groups. By 60 minutes, patients taking acetaminophen improved by 3.6 (standard deviation 2.9) on the 0 to 10 pain scale, whereas patients taking hydromorphone improved by 4.6 (standard deviation 3.3) (95% confidence interval [CI] for the difference of 1.0 was 0.1 to 2.0). Additional analgesic medications were required for 37 (46%) of 81 patients taking acetaminophen and 31 (38%) of 81 patients taking hydromorphone (95% CI for the rounded difference of 7% was -8% to 23%). Adverse events were reported by 6 (7%) of 81 patients taking acetaminophen and 10 (12%) of 81 patients taking hydromorphone (95% CI for the difference of 5% was -4% to 14%) and included dizziness, drowsiness, headache, and nausea.

CONCLUSION

Although 0.5 mg of the intravenously administered hydromorphone was statistically superior to 1,000 mg of intravenous acetaminophen administered in older patients with acute severe pain in the ED, this difference was not clinically significant. Regardless of the medication received, many participants experienced minimal or incomplete pain relief.

Echocardiographic Parameters and Outcomes in Methamphetamine-Associated Heart Failure: A Propensity Score-Weighted Analysis

Background

Methamphetamines are a common cause of systolic heart failure (HF). There are limited data on the prognosis associated with hospitalizations for decompensated HF in the setting of methamphetamine use. We aimed to evaluate patient characteristics and outcomes among patients admitted with decompensated HF who had positive drug screens for amphetamines as well as to determine whether any parameters from transthoracic echocardiogram (TTE) can predict outcomes in this population.

Methods

This was a retrospective cohort study of consecutive adult patients admitted to the Loma Linda Medical Center who had an active hospital problem of acute on chronic systolic (or systolic and diastolic) HF from 2013 to 2018. Electronic medical records were mined for relevant patient data. Methamphetamine-associated heart failure (MethHF) group was defined as those with an admission urine drug screen (UDS) that was positive for methamphetamines, whereas non-MethHF was defined by patients with negative methamphetamine on UDS or UDS was not done on physician’s discretion. The primary outcomes of the study were 30-day composite outcome (defined as combined all-cause readmission and all-cause mortality), 365-day all-cause mortality, and length of stay (LOS). Propensity score weighting for these outcomes was performed using demographics, laboratory and clinical variables, and left ventricular ejection fraction (LVEF) as covariates. TTE parameters from presentation were also evaluated to determine if any had prognostic implications.

Results

A total of 1,655 patients were included (101 patients with positive urine methamphetamine and 1,554 patients without). Patients with MethHF were younger, more likely to be male, had fewer comorbidities, had lower LVEF, and were more likely to have right ventricular systolic dysfunction. In propensity-weighted analyses, there were no significant differences in LOS, 30-day composite outcome, or 365-day mortality between the MethHF and non-MethHF group in (P > 0.05 for all). Presence of at least moderate tricuspid valve regurgitation (TR) was the only TTE predictor of 30-day composite outcome (odds ratio (OR) = 4.67, 95% confidence interval (CI): 1.5 - 14.50, P < 0.01) and 365-day mortality (OR = 4.67, 95% CI: 1.5 - 14.50, P < 0.01) in the MethHF group.

Conclusion

Patients with MethHF admitted for decompensated HF had similar outcomes compared to non-MethHF after adjusting for baseline characteristics. TR is the only TTE value to predict outcomes in this population.

Influence of Society for Academic Emergency Medicine Foundation's Research Training Grant on postaward academic federal funding

OBJECTIVES

The objective was to measure the impact of the Society for Academic Emergency Medicine Foundation's (SAEMF) Research Training Grant (RTG) by comparing academic success in grant recipients versus non-recipient applicants. Our primary outcome was subsequent federal funding as a principal investigator (PI) or multiple principal investigator (MPI). Our secondary outcomes included subsequent K-award funding, R-series funding, R01 funding, and academic productivity measured by first author peer-reviewed publications.

METHODS

The authors examined all SAEMF RTG applicants from 2002 through 2019 (n = 109). Data were collected using the National Institutes of Health RePORTER database, a literature search using PubMed, and an online survey sent to all RTG applicants. Relative risks (RRs) with 95% confidence intervals (95% CI) were calculated.

RESULTS

Over 18 years, 18 of 109 (16.5%) RTG applicants were awarded by SAEMF. Subsequent federal funding as PI or MPI was obtained by 11 of the 18 RTG recipients compared to 29 of the 91 nonrecipients (61% vs. 33%, RR = 1.9; 95% CI = 1.2-3.1). The RTG award was also associated with increased probability of receiving a federal Career Development Award (K-series) (RR 2.0; 95% CI 1.1-3.9) and R-series award (RR 2.0; 95% CI 1.1-3.9) but not an R01 award (RR 2.1; 95% CI 0.8-5.3). The median number of first-authored peer reviewed manuscripts did not differ between RTG award recipients (14, IQR 8,44) and nonrecipients (14, IQR 6,30) (p = 0.5) though RTG recipients had a higher percentage of their publications as a first author (49% vs. 33%, p = 0.04).

CONCLUSIONS

SAEMF RTG awards were associated with increased probability of future federal funding, including career development awards and R-series awards but not R01 awards. RTG recipients also had a higher percentage of their peer reviewed publications as first author.

Characteristics of medical students interested in emergency medicine with intention to practice in underserved areas

OBJECTIVES

Emergency departments serve a wide variety of racial, ethnic, socioeconomic, and gender backgrounds. It is currently unknown what characteristics of students who express interest in emergency medicine (EM) are associated with a simultaneous desire to work in medically underserved areas. We hypothesize that those who are underrepresented in medicine, are female, learn another language, and have more student debt will be more likely to practice in a medically underserved area.

METHODS

Data from the National Board of Medical Examiners, Association of American Medical Colleges (AAMC) Student Record System, and the AAMC Graduation Questionnaire were collected on a national cohort of 92,013 U.S. medical students who matriculated from 2007 through 2012. Extracted variables included planned practice area, intention to practice in underserved areas, race/ethnicity, sex, medical school experiences, age at matriculation, debt at graduation, and first-attempt USMLE Step 1 score.

RESULTS

EM-intending students who identified as female, non-Hispanic Black/African American, or Latinx/Hispanic; had a larger debt at graduation; had experiences with health education in the community; had global health experience; and had learned more than one language were more likely to report an intention to practice in underserved areas.

CONCLUSION

With the increasing importance of physician diversity to match those of the community being served, this study identifies factors associated with a desire of EM students to work in underserved areas. Medical schools and EM residencies may wish to consider these factors in their admissions process.

Evaluation of Specimen Types and Saliva Stabilization Solutions for SARS-CoV-2 Testing

Identifying SARS-CoV-2 infections through aggressive diagnostic testing remains critical to tracking and curbing the spread of the COVID-19 pandemic. Collection of nasopharyngeal swabs (NPS), the preferred sample type for SARS-CoV-2 detection, has become difficult due to the dramatic increase in testing and consequent supply strain. Therefore, alternative specimen types have been investigated that provide similar detection sensitivity with reduced health care exposure and the potential for self-collection. In this study, the detection sensitivity of SARS-CoV-2 in nasal swabs (NS) and saliva was compared to that of NPS using matched specimens from two outpatient cohorts in New York State (total n = 463). The first cohort showed only a 5.4% positivity, but the second cohort (n = 227) had a positivity rate of 41%, with sensitivity in NPS, NS, and saliva of 97.9%, 87.1%, and 87.1%, respectively. Whether the reduced sensitivity of NS or saliva is acceptable must be assessed in the settings where they are used. However, we sought to improve on it by validating a method to mix the two sample types, as the combination of nasal swab and saliva resulted in 94.6% SARS-CoV-2 detection sensitivity. Spiking experiments showed that combining them did not adversely affect the detection sensitivity in either. Virus stability in saliva was also investigated, with and without the addition of commercially available stabilizing solutions. The virus was stable in saliva at both 4°C and room temperature for up to 7 days. The addition of stabilizing solutions did not enhance stability and, in some situations, reduced detectable virus levels.

Disparities in Acute Pain Treatment by Cognitive Status in Older Adults With Hip Fracture

BACKGROUND

We examined the disparities in emergency department (ED) pain treatment based on cognitive status in older adults with an acute hip fracture.

METHODS

Observational study in an academic ED in the Bronx, New York. One hundred forty-four adults aged 65 years and older with acute hip fracture were administered the Telephone Interview for Cognitive Status (TICS) while in the ED. The primary outcome was receipt of any parenteral analgesic. The risk factor of interest was cognitive impairment (TICS ≤ 25). Secondary outcomes included receipt of any opioid, receipt of any analgesic, total dose of analgesics in intravenous morphine equivalent units (MEQ), and time to receiving first analgesic.

RESULTS

Of the 87 (60%) study patients who were cognitively impaired, 60% received a parenteral analgesic compared to 79% of the 57 cognitively unimpaired patients (RR 0.76 [95% CI 0.61, 0.94]). The effect of cognitive impairment on receiving any opioids (RR: 0.81, 95% CI 0.67, 0.98) and any analgesic (RR: 0.85; 95% CI: 0.71, 1.01) was similar. The median analgesic dose in cognitively impaired patients was significantly lower than in cognitively unimpaired patients (4 MEQ vs 8 MEQ, p = .003).

CONCLUSION

Among older adults presenting to the ED with acute hip fracture, cognitive impairment was independently associated with lower likelihood of receiving analgesia and lower amount of opioid analgesia.

A Randomized Trial Comparing the Efficacy of Five Oral Analgesics for Treatment of Acute Musculoskeletal Extremity Pain in the Emergency Department

STUDY OBJECTIVE

We compare the efficacy and adverse effects of 5 oral analgesics in emergency department (ED) patients aged 21 to 64 years with acute musculoskeletal pain.

METHODS

This was a randomized clinical trial conducted in 2 urban EDs. Patients received 400 mg ibuprofen/1,000 mg acetaminophen, 800 mg ibuprofen/1,000 mg acetaminophen, 30 mg codeine/300 mg acetaminophen, 5 mg hydrocodone/300 mg acetaminophen, or 5 mg oxycodone/325 mg acetaminophen. The primary outcome was change in pain before administration of medication (baseline) to 1 hour postbaseline. A numeric rating scale was used, varying from 0="no pain" to 10="worst imaginable pain." Secondary outcomes included receipt of rescue medication and adverse effects at 1 and 2 hours postbaseline. ANOVA was used to test differences in the primary outcome between treatment groups.

RESULTS

Six hundred participants, predominantly men and Latino, were enrolled. Change in pain from baseline to 60 minutes did not differ by treatment (P=.69). The mean change in pain in numeric rating scale units was 400 mg ibuprofen/1,000 mg acetaminophen 3.0 (95% confidence interval [CI] 2.6 to 3.5); 800 mg ibuprofen/1,000 mg acetaminophen 3.0 (95% CI 2.5 to 3.5), 30 mg codeine/300 mg acetaminophen 3.4 (95% CI 2.9 to 3.9), 5 mg hydrocodone/300 mg acetaminophen 3.1 (95% CI 2.7 to 3.5), and 5 mg oxycodone/325 mg acetaminophen 3.3 (95% CI 2.8 to 3.7). Rescue medication was received before 1 hour had elapsed by 2 patients receiving 400 mg ibuprofen/1,000 mg acetaminophen (1.7%), 3 patients receiving 800 mg ibuprofen/1,000 mg acetaminophen (2.5%), zero patients receiving 30 mg codeine/300 mg acetaminophen (0.0%), 3 patients receiving 5 mg hydrocodone/300 mg acetaminophen (2.5%), and zero patients receiving 5 mg oxycodone/325 mg acetaminophen (0.0%) (P=.21). More patients who received opioids were nauseated or vomited compared with those who did not: 6.7% versus 1.7% (5.0% difference; 95% CI 1.7% to 8.2%). The findings at 2 hours were similar.

CONCLUSION

No analgesic was more efficacious than others 1 or 2 hours after baseline. There was significantly more nausea and vomiting among patients treated with opioids.

Randomized Clinical Trial of Intravenous (IV) Acetaminophen as an Adjunct to IV Hydromorphone for Acute Severe Pain in Emergency Department Patients

BACKGROUND

A fundamental challenge for emergency department (ED) clinicians is to relieve severe, acute pain while simultaneously avoiding adverse events associated with opioid analgesics. Because there is evidence that intravenous (IV) acetaminophen is an effective adjuvant analgesic in postoperative settings, we examined whether it also has a role in the ED.

METHODS

This was a two-arm, double-blind randomized clinical trial. All patients received 1 mg of IV hydromorphone. Patients were then randomized to receive 1 g of IV acetaminophen or placebo. The primary outcome was the between-group difference in change in pain from baseline (before treatment) to 60 minutes after administration of study drugs, measured on an 11-point numeric rating scale (NRS).

RESULTS

Of 828 patients screened, 162 were enrolled and 159 had the primary outcome. Patients allocated to acetaminophen + hydromorphone had a mean decline in pain from baseline to 60 minutes of 6.2 NRS units; those receiving placebo + hydromorphone had a mean decline of 5.4, a difference of 0.8 NRS units (95% confidence interval [CI] = -0.01 to 1.8). Two patients in each group received additional analgesics in the first 60 minutes of the study. At 120 minutes the NRS pain difference was 0.6 (95% CI = -0.4 to 1.6). A total of 26.9% of patients who received acetaminophen wanted more analgesia versus 37.7% of those given placebo (difference = -10.8%, 95% CI = -24.3% to 4.4%). The incidence of adverse effects was similar in both groups.

CONCLUSIONS

The addition of 1 g of IV acetaminophen to 1 mg of IV hydromorphone provided neither clinically meaningful nor statistically superior analgesia than hydromorphone alone.

Physician Renewal of Chronically Prescribed Controlled Substances Based on Urine Drug Test Results

Objective: The effect of specific urine drug testing (UDT) results on physician prescribing habits has not been well described. The primary objective was to report renewal rates of chronically prescribed controlled substances based on types of inconsistent UDT results. Methods: We conducted a retrospective chart review over a 5-month period comparing prescription renewals rates for patients with consistent versus inconsistent UDTs. Inconsistent UDTs were defined by prescribed drug not detected or the presence of heroin, cocaine, nonprescribed opioids, nonprescribed benzodiazepines, or marijuana. Results: Of the 474 UDTs reviewed, 214 (45.1%) were inconsistent. The most common findings among inconsistent UDTs, including overlapping results, were prescribed drug not detected (26.8%) and the presence of marijuana (20.7%), nonprescribed opioids (9.9%), and nonprescribed benzodiazepines (6.1%). In contrast, cocaine (5.5%) and heroin (0.4%) were less likely to be found on UDTs for this population. The relative risk (RR) of prescription renewal was 0.64 (95% CI 0.57-0.71) for inconsistent UDTs versus consistent UDTs. Within the inconsistent UDTs, the renewal rates when marijuana (79.6%) or nonprescribed opioids or benzodiazepines (63.6%) were present were much higher than when heroin or cocaine were present (0.0%; P < .001). Patients whose prescribed controlled substance was not detected had a 55.8% renewal rate. Conclusions: Prescription renewal rates were high when patient UDTs contained nonprescribed marijuana, opioids, and benzodiazepines, or when the prescribed drug was not detected. Prescription renewal rates were low when illicit drugs, such as heroin and cocaine, were detected.

Randomized Clinical Trial of Intravenous Acetaminophen as an Analgesic Adjunct for Older Adults With Acute Severe Pain

OBJECTIVES

Older adults are at risk for undertreatment of pain. We examined intravenous (IV) acetaminophen as an analgesic adjunct to IV opioids in the care of older emergency department (ED) patients with acute severe pain.

METHODS

This was a randomized clinical trial conducted in two EDs in the Bronx, New York. Eligible adults aged 65 years and older with acute severe pain were randomized to 0.5 mg of IV hydromorphone and 1 g of IV acetaminophen or 0.5 mg of IV hydromorphone and 100 mL of normal saline placebo. The primary outcome was the between group difference in improvement of numerical rating scale (NRS) pain scores at 60 minutes. Secondary outcomes were the between-group differences in the proportion of patients who chose to forgo additional pain medications at 60 minutes; the proportion who developed side effects; the proportion who required rescue analgesia; and between-group differences in NRS pain scores at 5, 15, 30, and 45 minutes.

RESULTS

Eighty-one patients were allocated to each arm. Eighty patients in the IV acetaminophen arm and 79 patients in the placebo arm had sufficient data for analysis. At 60 minutes, patients in the hydromorphone + IV acetaminophen group improved by 5.7 NRS units while those in the hydromorphone + placebo group improved by 5.2 NRS units, for a difference of 0.6 NRS units (95% confidence interval [CI] = -0.4 to 1.5). A total of 28.7% of patients in the hydromorphone + IV acetaminophen group wanted more analgesia at 60 minutes versus 29.1% in the hydromorphone + placebo group, for a difference of -0.4% (95% CI = -14.3% to 13.5%). These differences were neither clinically nor statistically significant. Safety profiles were similar in both groups.

CONCLUSION

In this randomized clinical trial, the addition of IV acetaminophen to IV hydromorphone as an adjunctive analgesic for acute, severe, pain in older adults provided neither clinically nor statistically superior pain relief when compared to hydromorphone alone within the first hour of treatment.

Comparative Effectiveness of Patient-Controlled Analgesia for Treating Acute Pain in the Emergency Department

STUDY OBJECTIVE

We assess the effectiveness of patient-controlled analgesia in the emergency department (ED). We hypothesized that decline in pain intensity from 30 to 120 minutes after initial intravenous opioid administration is greater in patients receiving morphine by patient-controlled analgesia compared with usual care and would differ by a clinically significant amount.

METHOD

This was a pragmatic randomized controlled trial of patient-controlled analgesia and usual care (opioid and dose at physician's discretion) in 4 EDs. Entry criteria included age 18 to 65 years and acute pain requiring intravenous opioids. The primary outcome was decline in numeric rating scale pain score 30 to 120 minutes postbaseline. Secondary outcomes included satisfaction, time to analgesia, adverse events, and patient-controlled analgesia pump-related problems. We used a mixed-effects linear model to compare rate of decline in pain (slope) between groups. A clinically significant difference between groups was defined as a difference in slopes equivalent to 1.3 numeric rating scale units.

RESULTS

Six hundred thirty-six patients were enrolled. The rate of decline in pain from 30 to 120 minutes was greater for patients receiving patient-controlled analgesia than usual care (difference=1.0 numeric rating scale unit; 95% confidence interval [CI] 0.6 to 1.5; P<.001) but did not reach the threshold for clinical significance. More patients receiving patient-controlled analgesia were satisfied with pain management (difference=9.3%; 95% CI 3.3% to 15.1%). Median time to initial analgesia was 15 minutes longer for patient-controlled analgesia than usual care (95% CI 11.4 to 18.6 minutes). There were 7 adverse events in the patient-controlled analgesia group and 1 in the usual care group (difference=2.0%; 95% CI 0.04% to 3.9%), and 11 pump-programming errors.

CONCLUSION

The findings of this study do not favor patient-controlled analgesia over usual ED care for acute pain management.

Effect of a Single Dose of Oral Opioid and Nonopioid Analgesics on Acute Extremity Pain in the Emergency Department: A Randomized Clinical Trial

IMPORTANCE

The choice of analgesic to treat acute pain in the emergency department (ED) lacks a clear evidence base. The combination of ibuprofen and acetaminophen (paracetamol) may represent a viable nonopioid alternative.

OBJECTIVES

To compare the efficacy of 4 oral analgesics.

DESIGN, SETTINGS, AND PARTICIPANTS

Randomized clinical trial conducted at 2 urban EDs in the Bronx, New York, that included 416 patients aged 21 to 64 years with moderate to severe acute extremity pain enrolled from July 2015 to August 2016.

INTERVENTIONS

Participants (104 per each combination analgesic group) received 400 mg of ibuprofen and 1000 mg of acetaminophen; 5 mg of oxycodone and 325 mg of acetaminophen; 5 mg of hydrocodone and 300 mg of acetaminophen; or 30 mg of codeine and 300 mg of acetaminophen.

MAIN OUTCOMES AND MEASURES

The primary outcome was the between-group difference in decline in pain 2 hours after ingestion. Pain intensity was assessed using an 11-point numerical rating scale (NRS), in which 0 indicates no pain and 10 indicates the worst possible pain. The predefined minimum clinically important difference was 1.3 on the NRS. Analysis of variance was used to test the overall between-group difference at P = .05 and 99.2% CIs adjusted for multiple pairwise comparisons.

RESULTS

Of 416 patients randomized, 411 were analyzed (mean [SD] age, 37 [12] years; 199 [48%] women; 247 [60%] Latino). The baseline mean NRS pain score was 8.7 (SD, 1.3). At 2 hours, the mean NRS pain score decreased by 4.3 (95% CI, 3.6 to 4.9) in the ibuprofen and acetaminophen group; by 4.4 (95% CI, 3.7 to 5.0) in the oxycodone and acetaminophen group; by 3.5 (95% CI, 2.9 to 4.2) in the hydrocodone and acetaminophen group; and by 3.9 (95% CI, 3.2 to 4.5) in the codeine and acetaminophen group (P = .053). The largest difference in decline in the NRS pain score from baseline to 2 hours was between the oxycodone and acetaminophen group and the hydrocodone and acetaminophen group (0.9; 99.2% CI, -0.1 to 1.8), which was less than the minimum clinically important difference in NRS pain score of 1.3. Adverse events were not assessed.

CONCLUSIONS AND RELEVANCE

For patients presenting to the ED with acute extremity pain, there were no statistically significant or clinically important differences in pain reduction at 2 hours among single-dose treatment with ibuprofen and acetaminophen or with 3 different opioid and acetaminophen combination analgesics. Further research to assess adverse events and other dosing may be warranted.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02455518.

Comparative Analgesic Efficacy of Oxycodone/Acetaminophen Versus Hydrocodone/Acetaminophen for Short-term Pain Management in Adults Following ED Discharge

OBJECTIVES

The objective was to test the hypothesis that oxycodone/acetaminophen provides superior analgesia to hydrocodone/acetaminophen for the treatment of acute extremity pain following emergency department (ED) discharge.

METHODS

This was a prospective, randomized, double-blind clinical trial of nonelderly adult ED patients with acute musculoskeletal extremity pain, randomly allocated at discharge to receive oxycodone/acetaminophen (5 mg/325 mg) or hydrocodone/acetaminophen (5 mg/325 mg). The primary outcome was the between-group difference in improvement in numerical rating scale (NRS) pain scores over a 2-hour period following the most recent ingestion of study drug, obtained during telephone contact 24 hours after ED discharge. Secondary outcomes included proportionate decrease in pain, comparative side-effect profiles, and patient satisfaction.

RESULTS

A total of 240 patients were enrolled. The final sample consisted of 220 patients, 107 randomly allocated to oxycodone/acetaminophen and 113 to hydrocodone/acetaminophen. At 24 hours after ED discharge, the mean NRS pain scores prior to the most recent dose of outpatient pain medication were 7.8 and 7.9 in the oxycodone/acetaminophen and hydrocodone/acetaminophen groups, respectively. The mean decreases in pain scores over 2 hours were 4.4 NRS units in the oxycodone/acetaminophen group versus 4.0 NRS units in the hydrocodone/acetaminophen group, for a difference of 0.4 NRS units (95% confidence interval = -0.2 to 1.1 NRS units). Satisfaction with the analgesics was similar.

CONCLUSIONS

This study design could not detect a clinically or statistically significant difference in analgesic efficacy between oxycodone/acetaminophen (5 mg/325 mg) and hydrocodone/acetaminophen (5 mg/325 mg) for treatment of acute musculoskeletal extremity pain in adults following ED discharge. Both opioids reduced pain scores by approximately 50%.

Comparative Analgesic Efficacy of Oxycodone/Acetaminophen vs Codeine/Acetaminophen for Short-Term Pain Management Following ED Discharge

OBJECTIVE

To test the hypothesis that oxycodone/acetaminophen provides analgesia superior to codeine/acetaminophen following emergency department (ED) discharge.

DESIGN

Prospective, randomized, double-blind, trial.

SETTING

Adult inner city ED.

SUBJECTS

ED patients with acute extremity pain who were discharged home.

METHODS

Patients randomized to oxycodone/acetaminophen (5 mg/325 mg) or codeine/acetaminophen (30 mg/300 mg). The primary outcome, obtained via telephone one day after ED discharge, was the between-group difference in improvement in numerical rating scale (NRS) pain scores over a 2-hour period following the most recent ingestion of study drug. Secondary outcomes included proportion of patients with >50% pain reduction, side-effect profile, and patient satisfaction.

RESULTS

Two hundred and forty patients were enrolled. Mean baseline NRS scores were 7.9 in both groups. Mean decrease over 2 hours was 4.5 NRS units in the oxycodone/acetaminophen group vs 4.2 NRS units in the codeine/acetaminophen group, for a clinically and statistically nonsignificant difference of 0.2 NRS units (95% CI -0.4-0.9 NRS units). Similarly, 66% vs 61% achieved >50% pain relief for a nonsignificant difference of 5% (95% CI -8% to 17%). Side-effect profile and patient satisfaction were similar.

CONCLUSION

Our hypothesis that oxycodone/acetaminophen provides analgesia superior to codeine/acetaminophen was rejected. Although pain within each group was reduced by more than half, the between-group difference was not significant. Pending independent validation, these unexpected findings suggest that codeine/acetaminophen, a Schedule III agent, may be a clinically reasonable outpatient opioid alternative to oxycodone/acetaminophen, a more tightly restricted Schedule II agent thought to be more prone to misuse.

Gender differences in acute and chronic pain in the emergency department: results of the 2014 Academic Emergency Medicine consensus conference pain section

Pain is a leading public health problem in the United States, with an annual economic burden of more than $630 billion, and is one of the most common reasons that individuals seek emergency department (ED) care. There is a paucity of data regarding sex differences in the assessment and treatment of acute and chronic pain conditions in the ED. The Academic Emergency Medicine consensus conference convened in Dallas, Texas, in May 2014 to develop a research agenda to address this issue among others related to sex differences in the ED. Prior to the conference, experts and stakeholders from emergency medicine and the pain research field reviewed the current literature and identified eight candidate priority areas. At the conference, these eight areas were reviewed and all eight were ratified using a nominal group technique to build consensus. These priority areas were: 1) gender differences in the pharmacological and nonpharmacological interventions for pain, including differences in opioid tolerance, side effects, or misuse; 2) gender differences in pain severity perceptions, clinically meaningful differences in acute pain, and pain treatment preferences; 3) gender differences in pain outcomes of ED patients across the life span; 4) gender differences in the relationship between acute pain and acute psychological responses; 5) the influence of physician-patient gender differences and characteristics on the assessment and treatment of pain; 6) gender differences in the influence of acute stress and chronic stress on acute pain responses; 7) gender differences in biological mechanisms and molecular pathways mediating acute pain in ED populations; and 8) gender differences in biological mechanisms and molecular pathways mediating chronic pain development after trauma, stress, or acute illness exposure. These areas represent priority areas for future scientific inquiry, and gaining understanding in these will be essential to improving our understanding of sex and gender differences in the assessment and treatment of pain conditions in emergency care settings.

Randomized clinical trial of hydrocodone/acetaminophen versus codeine/acetaminophen in the treatment of acute extremity pain after emergency department discharge

OBJECTIVES

The objective was to test the hypothesis that hydrocodone/acetaminophen (Vicodin [5/500]) provides more efficacious analgesia than codeine/acetaminophen (Tylenol #3 [30/300]) in patients discharged from the emergency department (ED). Both are currently Drug Enforcement Administration (DEA) Schedule III narcotics.

METHODS

This was a prospective, randomized, double-blind, clinical trial of patients with acute extremity pain who were discharged home from the ED, comparing a 3-day supply of oral hydrocodone/acetaminophen (5 mg/500 mg) to oral codeine/acetaminophen (30 mg/300 mg). Pain was measured on a valid and reproducible verbal numeric rating scale (NRS) ranging from 0 to 10, and patients were contacted by telephone approximately 24 hours after being discharged. The primary outcome was the between-group difference in improvement in pain at 2 hours following the most recent ingestion of the study drug, relative to the time of phone contact after ED discharge. Secondary outcomes compared side-effect profiles and patient satisfaction.

RESULTS

The median time from ED discharge to follow-up was 26 hours (interquartile range [IQR] = 24 to 39 hours). The mean NRS pain score before the most recent dose of pain medication after ED discharge was 7.6 NRS units for both groups. The mean decrease in pain scores 2 hours after pain medications were taken were 3.9 NRS units in the hydrocodone/acetaminophen group versus 3.5 NRS units in the codeine/acetaminophen group, for a difference of 0.4 NRS units (95% confidence interval [CI] = -0.3 to 1.2 NRS units). No differences were found in side effects or patient satisfaction.

CONCLUSIONS

Both medications decreased NRS pain scores by approximately 50%. However, the oral hydrocodone/acetaminophen failed to provide clinically or statistically superior pain relief compared to oral codeine/acetaminophen when prescribed to patients discharged from the ED with acute extremity pain. Similarly, there were no clinically or statistically important differences in side-effect profiles or patient satisfaction. If the DEA reclassifies hydrocodone as a Schedule II narcotic, as recently recommended by its advisory board, our data suggest that the codeine/acetaminophen may be a clinically reasonable Schedule III substitute for hydrocodone/acetaminophen at ED discharge. These findings should be regarded as tentative and require independent validation in similar and other acute pain models.

Randomized clinical trial of efficacy and safety of a single 2-mg intravenous dose of hydromorphone versus usual care in the management of acute pain

OBJECTIVES

The objective was to test the efficacy and safety of 2 mg of intravenous (IV) hydromorphone (Dilaudid) against "usual care" in emergency department (ED) patients with acute severe pain.

METHODS

This was a randomized clinical trial. Patients allocated to 2 mg of IV hydromorphone received their medication in a single dose. Those randomized to usual care received any IV opioid, with type, dose, and frequency chosen by the ED attending. All patients received 2 L/min. nasal cannula oxygen. The primary outcome was the difference in the proportion of patients who achieved clinically satisfactory analgesia by 30 minutes. This was defined as the patient declining additional analgesia when asked the question, "Do you want more pain medicine?" A 10% absolute difference was chosen a priori as the minimum difference considered clinically significant.

RESULTS

Of 175 subjects randomized to each group, 164 in the 2 mg hydromorphone group and 161 in the usual care group had sufficient data for analysis. Additional pain medication was declined by 77.4% of patients in the 2 mg hydromorphone group at 30 minutes, compared to 65.8% in the usual care group. This difference of 11.6% was statistically and clinically significant (95% confidence interval [CI] = 1.8% to 21.1%). Safety profiles were similar and no patient required naloxone. There was more pruritus in the hydromorphone group (18.3% vs. 8.7%; difference = 9.6%, 95% CI = 2.6% to 16.6%).

CONCLUSIONS

Using a simple dichotomous patient-centered endpoint in which a difference of 10% in proportion obtaining adequate analgesia was considered clinically significant, 2 mg of hydromorphone in a single IV dose is clinically and statistically more efficacious when compared to usual care for acute pain management in the ED.

Problems with measurement of the minimum clinically significant difference in acute pain in elders

OBJECTIVES

A standard value for the minimum clinically significant difference (MCSD) in pain in nonelderly ED patients has been identified and has facilitated research in this age group. It is not clear that this value is similar in older patients. The standard method for calculating the MCSD in pain is to average scores on a numerical rating scale (NRS) over contiguous time periods. This method is based on the assumption that the MCSD remains constant over time. In an earlier hypothesis-generating study of elderly patients, this assumption was not met for the arithmetic MCSD, making it difficult to identify a single benchmark for measuring efficacy in analgesia trials in elders. The proportional MCSD was more stable, suggesting that it might constitute a better measure of analgesic efficacy in elderly patients. The objective of the study was to test the hypotheses that: 1) the arithmetic MCSD in adults 65 years and older declines over time and that 2) the proportional MCSD remains constant.

METHODS

This was an observational, prospective, cohort study of emergency department (ED) patients ≥65 years with acute pain. Pain intensity was rated on a standard 11-point NRS upon study entry and every 30 minutes for 2 hours. The arithmetic MCSD was defined as the mean change in pain between contiguous 30-minute intervals when change in pain was described as "a little less" or "a little more." The proportional MCSD was calculated as the arithmetic MCSD divided by pain intensity at the beginning of the interval. We used generalized estimating equations (GEEs) to test trend over time.

RESULTS

A total of 214 patients were enrolled: mean (± standard deviation [SD]) age was 74 (±7.5) years, 66% were female, 63% were Hispanic, and 23% were African American. The median initial NRS was 8. The MCSD decreased 2.1 NRS units (95% confidence interval [CI] = 1.7 to 2.4) between 0 and 30 minutes, 1.4 units (95% CI = 1.0 to 1.7) between 30 and 60 minutes, 1.3 units (95% CI = 1.0 to 1.5) between 60 and 90 minutes, and 0.8 units (95% CI = 0.6 to 1.0) between 90 and 120 minutes (p < 0.001 for trend). The proportional MCSD also varied from 27% (95% CI = 23% to 32%) between 0 and 30 minutes, 19% (95% CI = 13% to 24%) between 30 and 60 minutes, 22% (95% CI = 18% to 27%) between 60 and 90 minutes, and 13% (95% CI = 9% to 18%) between 90 and 120 minutes (p < 0.001 for trend).

CONCLUSIONS

Both the arithmetic and the proportional MCSD in elderly patients in acute pain declined over time. Because both measures were numerically unstable, there does not appear to be a single value for the MCSD that can be used to identify the MCSD in pain for use in analgesic efficacy trials in elderly patients. A different metric may be needed to study pain and assess comparative analgesic efficacy in elderly patients.

Identifying the minimum clinically significant difference in acute pain in the elderly

STUDY OBJECTIVE

To identify the minimum clinically significant difference in pain in elderly emergency department (ED) patients.

METHODS

This was an observational, prospective study of a convenience sample of patients aged 65 years or older with acute pain. Patients rated their pain on an 11-point numeric rating scale (NRS) on entering the study and every 30 minutes for 2 hours. The arithmetic minimum clinically significant difference was defined as the mean difference between current and preceding NRS scores when the subject described his or her pain as "a little less pain" or "a little more pain." The proportional minimum clinically significant difference was change in NRS in a 30-minute interval divided by the NRS at the beginning of the interval. We used generalized estimating equations to adjust for nonindependence of pain scores and to test trend over time.

RESULTS

One hundred ninety-five patients were enrolled (mean age 74 years; 73% women; 51% Hispanic; 33% black). The arithmetic minimum clinically significant difference averaged over all periods was 1.5 (95% confidence interval 1.3 to 1.6), the proportional minimum clinically significant difference was 25% (95% confidence interval 20% to 29%). The arithmetic minimum clinically significant difference unexpectedly decreased over time: 2.1 from baseline to 30 minutes, 1.4 from 30 to 60 minutes, 1.3 from 60 to 90 minutes, and 1.0 from 90 to 120 minutes (P<.001). In contrast, the proportional differences were more stable: 27% from baseline to 30 minutes, 22% from 30 to 60 minutes, 22% from 60 to 90 minutes, and 28% from 90 to 120 minutes (P=.89).

CONCLUSION

The arithmetic minimum clinically significant difference in older ED patients was 1.5 NRS units and decreased over time, whereas the proportional change was 25% and more stable.

Two milligrams i.v. hydromorphone is efficacious for treating pain but is associated with oxygen desaturation

OBJECTIVE

To evaluate the safety and efficacy of a single dose of 2 mg i.v. hydromorphone administered to emergency department patients in acute severe pain.

DESIGN

Prospective interventional.

SETTING

Urban academic emergency department. PATIENT, PARTICIPANTS: Nonelderly adults (21- 64-years-old) with acute severe pain and baseline oxygen saturation (SO2) > or = 95 percent.

INTERVENTIONS

Two milligrams i.v. hydromorphone administered over 2-3 minutes.

MAIN OUTCOME MEASURES

The primary outcome was use of naloxone as a reversal agent. Secondary outcomes included degree of pain relief as measured on a numerical rating scale, frequency of oxygen desaturation (SO2 < 95 percent), and side effects.

RESULTS

Of the 269 patients, none received i.v. naloxone. Median pain scores fell from 10 (worst pain possible) at baseline to 1 within 5 minutes and to 0 (no pain) at 30 minutes. SO2 was > or = 95 percent at all time points in 68 percent of patients (95 percent CI 62-73 percent), while 26 percent (95 percent CI 21-32 percent) had one or more SO2 levels between 90-94 percent, and 6 percent (95 percent CI 4-10 percent) had SO2 values below 90 percent at one or more time points. The lowest SO2 was 82 percent. The incidence of nausea and vomiting were 16 percent and 7 percent, respectively.

CONCLUSIONS

Two milligrams i.v. hydromorphone provides efficacious and rapid pain relief in nonelderly adults presenting to the ED with acute severe pain. However, oxygen desaturation below 95 percent occurred in about one third of patients. Although no noticeable clinical signs of hypoxemia occurred, a conservative interpretation of this finding suggests that 2 mg i.v. hydromorphone is too much opioid to be given routinely to patients in pain as a single initial dose.

Response to morphine in male and female patients: analgesia and adverse events

BACKGROUND

There is little agreement about a differential response of men and women to opioid analgesics. Some experimental and clinical studies have shown that women have a better response to opioids, others have found no difference, and still others have found opioids to be more effective analgesics for men than women.

OBJECTIVES

To assess sex differences in analgesic response to morphine and incidence of adverse events in patients receiving a dose of 0.1 mg intravenous morphine/kg.

METHODS

Secondary analysis of the control arms of 6 randomized clinical trials that compared 0.1 mg/kg intravenous morphine with other opioids or other doses of morphine in patients aged 21 to 65 with acute pain. The setting was an academic medical center Emergency Department serving primarily Latino and African-American patients. Change in self-reported pain intensity from baseline to 30 minutes postbaseline on a validated and reproducible 11-point numerical rating scale and count of adverse events were the primary outcomes.

RESULTS

The sample consisted of 211 women and 144 men. The mean change in pain from baseline to 30 minutes postbaseline was 3.7 in women, 3.6 men (difference=0.04; 95% confidence interval: -0.52, 0.60). In women without nausea before administration of morphine, the incidence of adverse events was 18.3% versus 10.7% in men without initial nausea (difference=7.6%; 95% confidence interval: -2.0, 17.2).

DISCUSSION

Men and women presenting to the Emergency Department did not have a differential response to a single weight-based dose of morphine for alleviation of acute pain. Women without baseline nausea had more adverse events than men.

Safety and Efficacy of Hydromorphone as an Analgesic Alternative to Morphine in Acute Pain: A Randomized Clinical Trial

STUDY OBJECTIVE

We compare a standard weight-based dose of intravenous hydromorphone (Dilaudid) to a standard weight-based dose of intravenous morphine in adults presenting to the ED with acute severe pain.

METHODS

This was a prospective, randomized, double-blind, clinical trial conducted in an academic medical center. Of the 198 adult patients presenting to the ED with acute severe pain who were randomized to receive either intravenous hydromorphone at 0.015 mg/kg or intravenous morphine at 0.1 mg/kg, 191 patients had sufficient data for analysis. The main outcome measure was the difference between the 2 groups in pain reduction at 30 minutes as measured on a validated numeric rating scale. Adverse effects, pain reduction at 5 minutes and 2 hours postbaseline, and additional analgesics and antiemetics were tracked as secondary outcome measures.

RESULTS

The mean change of pain from baseline to 30 minutes postbaseline in patients allocated to intravenous hydromorphone was -5.5 numeric rating scale units versus -4.1 in patients allocated to intravenous morphine (difference -1.3; 95% confidence interval -2.2 to -0.5). Adverse effects were similar in both groups, with the exception of pruritus, which did not occur in patients receiving hydromorphone (0% versus 6% [difference -6%; 95% confidence interval -11% to -1%]). No patient required naloxone.

CONCLUSION

For the treatment of acute, severe pain in the emergency department, intravenous hydromorphone at 0.015 mg/kg represents a feasible alternative to intravenous morphine at 0.1 mg/kg.

Intravenous Bolus of Ultra-Low-Dose Naloxone Added to Morphine Does Not Enhance Analgesia in Emergency Department Patients

There is some evidence from in vitro, animal, and postoperative clinical studies that low doses of opioid antagonists combined with morphine increase analgesia. The theoretical model of this effect posits that ultra-low doses of opioid antagonists selectively antagonize excitatory, but not inhibitory, opioid receptor-mediated signaling. To determine whether this effect occurs in emergency department patients presenting with severe acute pain, we conducted a randomized, double-blind placebo-controlled trial to assess the relative analgesic effect of morphine administered with 3 different doses of naloxone versus morphine alone. Patients received 0.1 mg/kg morphine intravenously (IV) over 2 min plus one of 3 different doses of naloxone (0.1 ng/kg, 0.01 ng/kg, or 0.001 ng/kg) or normal saline. A 0 to 10 numerical rating scale (NRS) was used to measure pain intensity at baseline and every 30 min up to 4 hours. One hundred fifty-six patients with a median NRS of 10 (IQR: 8-10) were studied. There were no clinically or statistically significant differences in the mean pain intensity of patients in the 4 treatment groups over the 4-hour study period, nor were there differences in the administration of additional analgesics or incidence of side effects.

PERSPECTIVE

Ultra-low doses of naloxone in the 0.001 ng/kg to 0.1 ng/kg range do not enhance the analgesia provided by morphine alone among emergency department patients with acute, severe pain. This suggests that naloxone in these doses is not an effective adjunct to morphine for control of acute pain.

A randomized clinical trial to assess the efficacy of the Epley maneuver in the treatment of acute benign positional vertigo

OBJECTIVES

To compare the efficacy of the Epley maneuver with that of a placebo maneuver in patients presenting to the emergency department (ED) with benign positional vertigo (BPV).

METHODS

This was a prospective, randomized, single-blind placebo-controlled trial. Consecutive adult ED patients presenting to a university teaching hospital with BPV were randomized to treatment with either the Epley or placebo maneuver. The severity of vertigo was evaluated on a 0 to 10-point scale before and after the maneuvers.

RESULTS

Eleven patients were randomized to the Epley group and 11 to the placebo group before the trial was terminated, based on a planned interim analysis. The median decreases in vertigo severity were 6 (95% confidence interval [95% CI] = 4 to 9) for the Epley group and 1 (95% CI = 0 to 3) for the placebo group (p = 0.001).

CONCLUSIONS

The Epley maneuver is a simple bedside maneuver that appears to be more efficacious than a placebo maneuver in the treatment of acute BPV among ED patients.

Diplopia in a patient with carcinomatous meningitis: a case report and review of the literature

In a patient with a history of malignancy, an isolated neurologic sign or symptom may indicate metastasis to the central nervous system. To exclude this possibility, a lumbar puncture should still be performed after a nondiagnostic cranial computed tomography (CT) scan even in the absence of signs of infection. A case is presented of a 59 year-old man recently diagnosed with non-Hodgkin's lymphoma that presented to the Emergency Department (ED) with the sole complaint of diplopia. Examination was unremarkable except for a left abducens nerve palsy. Cranial CT scan was normal but initial cerebrospinal fluid results were suggestive of carcinomatous meningitis, and cytology results later confirmed this diagnosis. A review of diplopia and carcinomatous meningitis is presented, along with a suggested conservative diagnostic algorithm for cancer patients presenting with neurologic signs or symptoms.

Site-directed mutagenesis of the ionizable groups in the active site of Zymomonas mobilis pyruvate decarboxylase: effect on activity and pH dependence

Pyruvate decarboxylase (PDC, EC 4.1.1.1) is a thiamin diphosphate-dependent enzyme about which there is a large body of structural and functional information. The active site contains several absolutely conserved ionizable groups and all of these appear to be important, as judged by the fact that mutation diminishes or abolishes catalytic activity. Previously we have shown [Schenk, G., Leeper, F.J., England, R., Nixon, P.F. & Duggleby, R.G. (1997) Eur. J. Biochem. 248, 63-71] that the activity is pH-dependent due to changes in kcat/Km while kcat itself is unaffected by pH. The effect on kcat/Km is determined by a group with a pKa of 6.45; the identity of this group has not been determined, although H113 is a possible candidate. Here we mutate five crucial residues in the active site with ionizable side-chains (D27, E50, H113, H114 and E473) in turn, to residues that are nonionizable or should have a substantially altered pKa. Each protein was purified and characterized kinetically. Unexpectedly, the pH-dependence of kcat/Km is largely unaffected in all mutants, ruling out the possibility that any of these five residues is responsible for the observed pKa of 6.45. We conjecture that the kcat/Km profile reflects the protonation of an alcoholate anion intermediate of the catalytic cycle.

Mutagenesis at asp27 of pyruvate decarboxylase from Zymomonas mobilis. Effect on its ability to form acetoin and acetolactate

Pyruvate decarboxylase (PDC) is one of several enzymes that require thiamin diphosphate (ThDP) and a bivalent cation as essential cofactors. The three-dimensional structure of PDC from Zymomonas mobilis (ZMPDC) shows that Asp27 (D27) is close to ThDP in the active site, and mutagenesis of this residue has suggested that it participates in catalysis. The normal product of the PDC reaction is acetaldehyde but it is known that the enzyme can also form acetoin as a by-product from the hydroxyethyl-ThDP reaction intermediate. This study focuses on the role of D27 in the production of acetoin and a second by-product, acetolactate. D27 in ZMPDC was altered to alanine (D27A) and this mutated protein, the wild-type, and two other previously constructed PDC mutants (D27E and D27N) were expressed and purified. Determination of the kinetic properties of D27A showed that the affinity of D27A for ThDP is decreased 30-fold, while the affinity for Mg2+ and the Michaelis constant for pyruvate were similar to those of the wild-type. The time-courses of their reactions were investigated. Each mutant has greatly reduced ability to produce acetaldehyde and acetoin compared with the wild-type PDC. However, the effect of these mutations on acetaldehyde production is greater than that on acetoin formation. The D27A mutant can also form acetolactate, whereas neither of the other mutants, nor the wild-type PDC, can do so. In addition, acetaldehyde formation and/or release are reversible in wild-type ZMPDC but irreversible for the mutants. The results are explained by a mechanism involving thermodynamic and geometric characteristics of the intermediates in the reaction.

Effects of deletions at the carboxyl terminus of Zymomonas mobilis pyruvate decarboxylase on the kinetic properties and substrate specificity

The three-dimensional structure of Zymomonas mobilis pyruvate decarboxylase shows that the carboxyl-terminal region of the protein occludes the active site. This observation is consistent with earlier suggestions that the active site is inaccessible to solvent during catalysis. However, the carboxyl-terminal region must move aside to allow entry of the substrate, and again to permit the products to leave. Here we have examined the role of the carboxyl terminus by making 15 variants of the enzyme with serial deletions. The activity is largely unaffected by removal of up to seven residues but deletion of the next two, R561 and S560, results in a drastic loss of activity. Five of these deletion mutants were purified and fully characterized and showed progressive decreases in activity, in the ability to discriminate between pyruvate and larger substrates, and in cofactor affinity. Several substitution mutants at residues R561 and S560 were prepared, purified, and fully characterized. The results indicate important roles for the side-chain of R561 and the backbone atoms of S560. It is suggested that the carboxyl-terminal region of pyruvate decarboxylase is needed to lock in the cofactors and for the proper closure of the active site that is required for discrimination between substrates and for decarboxylation to occur.

Effect of mutagenesis at serine 653 of Arabidopsis thaliana acetohydroxyacid synthase on the sensitivity to imidazolinone and sulfonylurea herbicides

Resistance to sulfonylurea and imidazolinone herbicides can occur by mutations in acetohydroxyacid synthase (EC 4.1.3.18). Changing serine 653 to asparagine is known to cause insensitivity to imidazolinones but not to sulfonylureas. Here, S-653 of the Arabidopsis thaliana enzyme was mutated to alanine, threonine and phenylalanine. The purified mutated enzymes resemble wild-type in their enzymatic properties. The threonine and phenylalanine mutants are imidazolinone-resistant and the latter is also slightly sulfonylurea-resistant. The alanine mutant remains sensitive to both herbicides. The results suggest that the beta-hydroxyl group is not required for imidazolinone binding and that the size of the side-chain determines resistance.

Aspartate-27 and glutamate-473 are involved in catalysis by Zymomonas mobilis pyruvate decarboxylase

Zymomonas mobilis pyruvate decarboxylase (EC 4.1.1.1) was subjected to site-directed mutagenesis at two acidic residues near the thiamin diphosphate cofactor in the active site. Asp-27 was changed to Glu or Asn, and Glu-473 was mutated to Asp (E473D) or Gln (E473Q). Each mutant protein was purified to near-homogeneity, and the kinetic and cofactor-binding properties were compared with those of the wild-type protein. Despite the very conservative nature of these alterations, all mutants had a very low, but measurable, specific activity ranging from 0.025% (E473Q) to 0.173% (E473D) of the wild type. With the exception of E473Q, the mutants showed small decreases in the affinity for thiamin diphosphate, and binding of the second cofactor (Mg2+) was also weakened somewhat. With E473Q, both cofactors seemed to be very tightly bound so that they were not removed by the treatment that was effective for the wild-type enzyme and other mutant forms. All mutants showed minor changes in the Km for substrate, but these alterations did not account for the low activities. These low specific activities, accompanied by little change in the Km for pyruvate, are consistent with a quantitative model of the catalytic cycle in which the main effect of the mutations is to slow the decarboxylation step with a minor change in the rate constant for pyruvate binding.

Implant reconstruction following removal of tumors of the head and neck

Functional maxillofacial rehabilitation following tumor ablation depends on many variables. These include the magnitude of hard or soft tissue defects, the use of adjunctive chemotherapy or radiation therapy, and the presence of underlying systemic disease. The physiologic effects of tumor ablation and radiation therapy on local tissues and grafted bone are discussed in this article in relation to the ultimate use of implant supported prostheses. Cases are presented to illustrate a variety of clinical situations.

Herbicide-resistant forms of Arabidopsis thaliana acetohydroxyacid synthase: characterization of the catalytic properties and sensitivity to inhibitors of four defined mutants

Acetohydroxyacid synthase (AHAS) catalyses the first step in the synthesis of the branched-chain amino acids and is the target of several classes of herbicides. Four mutants (A122V, W574S, W574L and S653N) of the AHAS gene from Arabidopsis thaliana were constructed, expressed in Escherichia coli, and the enzymes were purified. Each mutant form and wild-type was characterized with respect to its catalytic properties and sensitivity to nine herbicides. Each enzyme had a pH optimum near 7.5. The specific activity varied from 13% (A122V) to 131% (W574L) of the wild-type and the Km for pyruvate of the mutants was similar to the wild-type, except for W574L where it was five-fold higher. The activation by cofactors (FAD, Mg2+ and thiamine diphosphate) was examined. A122V showed reduced affinity for all three cofactors, whereas S653N bound FAD more strongly than wild-type AHAS. Six sulphonylurea herbicides inhibited A122V to a similar degree as the wild-type but S653N showed a somewhat greater reduction in sensitivity to these compounds. In contrast, the W574 mutants were insensitive to these sulphonylureas, with increases in the Kiapp (apparent inhibition constant) of several hundred fold. All four mutants were resistant to three imidazolinone herbicides with decreases in sensitivity ranging from 100-fold to more than 1000-fold.

Expression, purification and characterization of Arabidopsis thaliana acetohydroxyacid synthase

Acetohydroxyacid synthase (EC 4.1.3.18) is the enzyme that catalyses the first step in the synthesis of the branched-chain amino acids valine, leucine and isoleucine. The AHAS gene from Arabidopsis thaliana with part of the chloroplast transit sequence removed was cloned into the bacterial expression vector pT7-7 and expressed in the Escherichia coli strain BL21(DE3). The expressed enzyme was purified by an extensive procedure involving (NH4)2SO4 fractionation followed by hydrophobic and anion-exchange chromatography. The purified enzyme appears as a single band on SDS/PAGE with a molecular mass of about 61 kDa. On gel filtration the enzyme is a dimer, migrating as a single peak with molecular masses of 109 and 113 kDa in the absence and presence of FAD respectively. Ion spray MS analysis yielded a mass of 63864 Da. The enzyme has optimum activity in the pH range 6.5-8.5 and exhibits absolute dependence on the three cofactors FAD, Mg2+ and thiamine diphosphate for activity. It displays negatively co-operative kinetics with respect to pyruvate concentration. A model was derived to explain the non-hyperbolic substrate-saturation curve, involving interaction between the active sites of the dimer. The Km for the first active site was found to be 8.01 +/- 0.66 mM; the Km for the second active site could not be accurately determined but was estimated to be approx. 100 mM. The enzyme is insensitive to valine, leucine and isoleucine but is strongly inhibited by the sulphonylurea herbicide, chlorsulphuron, and the imidazolinone herbicide, imazapyr. Inhibition by both herbicides exhibits slow-binding kinetics, whereas chlorsulphuron also shows tight-binding inhibition.

MAST 96

The Military Anti-Shock Trouser, or MAST suit, is a controversial device that has been used to support blood pressure in hypotensive trauma patients. Most studies on humans have shown that the device has limited clinical utility. In this study, a telephone survey of all 50 State Emergency Medical Services was conducted to determine the nature and extent of MAST suit usage in the United States. The trend in MAST suit usage in San Diego County over the last 7 years was also analyzed. Thirty (60%) states still require MAST suits to be carried on ambulances. In San Diego County, MAST suit inflations for adult, hypotensive (systolic blood pressure < 90 mmHg,) blunt trauma patients has declined from 37% in 1987, to 2% in 1993. Despite a lack of data supporting efficacy in areas of severe hypotensive shock, blunt trauma, long transport times, and pelvic fractures, states continue to expend resources on the MAST suit. It is for this reason that we believe that the clinical use of the MAST suit should be based upon medical control philosophy rather than legislation.

Low plasma cholesterol predicts an increased risk of lung cancer in elderly women

BACKGROUND

There have been significant efforts in the United States to lower high cholesterol levels. Studies of men, however, have found a higher total cancer mortality rate at lower levels of plasma cholesterol. Many of these studies have found that lung cancer is more closely associated than other cancers with low cholesterol. Of the studies that include women, none has demonstrated a statistically significant inverse association between low cholesterol and lung cancer.

METHODS

We examined the relation between very low plasma cholesterol levels ( < 160 mg/dl) and lung cancer death in an 18-year prospective study of 2,011 men and 2,327 women.

RESULTS

After adjusting for age, body mass index, smoking, and education, the relative hazard of lung cancer mortality for those with low cholesterol ( < 160 mg/dl) compared with all other cholesterol levels ( > or = 160 mg/dl) was 1.75 among men (P = 0.28) and 3.29 among women (P = 0.02). Excluding those who died within 5 years of baseline did not change the results.

CONCLUSIONS

Both men and women with baseline plasma cholesterol levels < 160 mg/dl were more likely to die of lung cancer. This difference was statistically significant in women. The association could not be explained by occult malignancy, smoking, or socioeconomic status.

Functional assay of plasma antithrombin using polyethylene glycol (PEG) defibrinated plasma

Polyethylene glycol(PEG) was used to precipitate fibrinogen to prepare defibrinated plasma in the two stage clotting assay of antithrombin activity. Five percent PEG-8000 precipitated fibrinogen from plasma without loss of antithrombin activity in the defibrinated plasma. Fibrin degradation products(FDP) as high as 640 ug/ml did not interfere the two stage clotting assay using PEG defibrinated plasma possibly because part of FDP was precipitated by PEG in the process of plasma defibrination. The two stage clotting assay was very sensitive to the changes of antithrombin activity in the range of 60%-100% of normal level. The assay was reproducible and correlated with chromogenic assay. The decrease of plasma antithrombin activity in a baboon septic shock model was demonstrated with this assay.

Retrospective study comparing the pathophysiology of antibiotic-treated and untreated Escherichia coli- and Staphylococcus aureus-infused baboons

Escherichia coli and Staphylococcus aureus are the most common pathogens encountered in septic shock. This is a descriptive study in which the pathophysiologic response to infusions of LD100 concentrations of E. coli and S. aureus are staged and compared. Equivalent concentrations of both organisms were infused over a 2 hr period into antibiotic-treated and untreated animals with the following results: 1) The apparent clearance of E. coli was less than that of S. aureus over the 2-hr infusion period, but far greater during the next 8 hr in both antibiotic-treated and untreated animals. Thus the clearance of E. coli fits a one-compartment (intravascular), and that of S. aureus fits a two-compartment (intra- and extravascular) model. 2) The intensity of the cardiovascular, temperature, and metabolic response to E. coli was greater, whereas that of the disseminated intravascular coagulant (DIC) response to S. aureus was greater. We conclude, therefore, that the response to E. coli consists of four stages with no invasion and colonization of tissues, whereas the response to S. aureus consists of two stages with invasion and colonization of tissues.