Deep Learning for Detection and Localization of B-Lines in Lung Ultrasound

Lung ultrasound (LUS) is an important imaging modality used by emergency physicians to assess pulmonary congestion at the patient bedside. B-line artifacts in LUS videos are key findings associated with pulmonary congestion. Not only can the interpretation of LUS be challenging for novice operators, but visual quantification of B-lines remains subject to observer variability. In this work, we investigate the strengths and weaknesses of multiple deep learning approaches for automated B-line detection and localization in LUS videos. We curate and publish, BEDLUS, a new ultrasound dataset comprising 1,419 videos from 113 patients with a total of 15,755 expert-annotated B-lines. Based on this dataset, we present a benchmark of established deep learning methods applied to the task of B-line detection. To pave the way for interpretable quantification of B-lines, we propose a novel "single-point" approach to B-line localization using only the point of origin. Our results show that (a) the area under the receiver operating characteristic curve ranges from 0.864 to 0.955 for the benchmarked detection methods, (b) within this range, the best performance is achieved by models that leverage multiple successive frames as input, and (c) the proposed single-point approach for B-line localization reaches an F 1-score of 0.65, performing on par with the inter-observer agreement. The dataset and developed methods can facilitate further biomedical research on automated interpretation of lung ultrasound with the potential to expand the clinical utility.

Psychological Evaluation of Patients With Cancer Presenting to the Emergency Department With Pain: Independent Predictors of Worse Pain Severity, Interference, and Higher Hourly Opioid Administration

PURPOSE

Pain is a common complaint in patients with cancer presenting to the emergency department (ED). This prospective study evaluated whether biopsychosocial factors could help predict cancer patients with risk of higher pain severity, pain interference, and opioid consumption.

METHODS

Patients with cancer presenting to the ED with a complaint of moderate-severe pain (≥ 4/10-numeric rating scale) completed validated self-report measures assessing sociodemographics, cancer-related treatments, pain severity and interference, medication use, and psychological symptoms (depression, anxiety, pain catastrophizing, and sleep disturbance). Opioids administered and subsequent hospitalization were abstracted. Univariable and multivariable regression analyses assessed factors associated with pain-related outcomes.

RESULTS

Participants (n = 175) presented with a variety of cancer types, with 76% having metastatic disease and 42% reporting current outpatient opioid use. Higher pain catastrophizing, lower depressive symptoms, lower income, outpatient opioid use, and historical chronic pain were independently associated with worse pain (P ≤ .05). Higher pain catastrophizing, anxiety, sleep disturbance, outpatient opioid use, and education were independently associated with worse pain interference (P ≤ .05). The sole independent predictor of ED opioid administration was outpatient opioid use. Patients taking outpatient opioids were younger, had lower health literacy, worse pain catastrophizing, sleep disturbance, depression/anxiety, and greater rates of metastatic cancer and cancer-related surgery (P ≤ .05).

CONCLUSION

Biopsychosocial factors, particularly pain catastrophizing, remained significantly associated with worse pain outcomes for patients with cancer in the ED even after controlling for demographic and clinical variables. Patient outpatient opioid use was independently associated with worse pain, interference, and greater opioid administration, identifying this as a marker for who may benefit most from adjuvant pharmacologic and behavioral interventions.

Delta radiomics analysis of Magnetic Resonance guided radiotherapy imaging data can enable treatment response prediction in pancreatic cancer

Background

Magnetic Resonance Image guided Stereotactic body radiotherapy (MRgRT) is an emerging technology that is increasingly used in treatment of visceral cancers, such as pancreatic adenocarcinoma (PDAC). Given the variable response rates and short progression times of PDAC, there is an unmet clinical need for a method to assess early RT response that may allow better prescription personalization. We hypothesize that quantitative image feature analysis (radiomics) of the longitudinal MR scans acquired before and during MRgRT may be used to extract information related to early treatment response.

Methods

Histogram and texture radiomic features (n = 73) were extracted from the Gross Tumor Volume (GTV) in 0.35T MRgRT scans of 26 locally advanced and borderline resectable PDAC patients treated with 50 Gy RT in 5 fractions. Feature ratios between first (F1) and last (F5) fraction scan were correlated with progression free survival (PFS). Feature stability was assessed through region of interest (ROI) perturbation.

Results

Linear normalization of image intensity to median kidney value showed improved reproducibility of feature quantification. Histogram skewness change during treatment showed significant association with PFS (p = 0.005, HR = 2.75), offering a potential predictive biomarker of RT response. Stability analyses revealed a wide distribution of feature sensitivities to ROI delineation and was able to identify features that were robust to variability in contouring.

Conclusions

This study presents a proof-of-concept for the use of quantitative image analysis in MRgRT for treatment response prediction and providing an analysis pipeline that can be utilized in future MRgRT radiomic studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01957-5.

Characterization of urinary protein profile in regular kratom (Mitragyna speciosa korth.) users in Malaysia

Mitragyna speciosa (Korth.) also known as kratom or ketum has been traditionally used for its diverse medicinal value in Southeast Asia. Despite of its therapeutic value, kratom's safety profile remains deficiently elucidated. Our study aims to characterize the urinary protein profile of regular kratom users to determine its toxic effects on renal functioning. A total of 171 respondents (comprising of n = 88 regular kratom users, and n = 83 healthy controls) were recruited for this study. Urine specimens were collected and analyzed using SDS-PAGE, followed by LC/MS/MS analysis. Our results show albumin is the primary, and most abundant form of protein excreted in kratom user's urine specimens (n = 60/64), indicating that kratom users are predisposed to proteinuria. Kratom users had an elevated urinary protein (with an intensity of 66.7 kDa band), and protein: creatinine ratio (PCR) concentrations relative to healthy controls. However, kratom user's urinary creatinine concentration was found to be in the normal range as the healthy control group. While, kratom users who tested positive for illicit drug use had an elevated urinary albumin concentration. Our preliminary findings indicate that regular consumption of freshly brewed kratom solution over a protracted period (for an average of eleven years) seems to induce proteinuria, suggestive of an early stage of kidney injury. Hence, further studies are urgently needed to confirm our findings, and establish kratom's renal impairing effects.

Chronic pain severity, impact, and opioid use among patients with cancer: An analysis of biopsychosocial factors using the CHOIR learning health care system

BACKGROUND

Despite the biopsychosocial underpinnings of chronic noncancer pain, relatively little is known about the contribution of psychosocial factors to chronic cancer pain. The authors aimed to characterize associations between biopsychosocial factors and pain and opioid use among individuals with chronic pain and cancer.

METHODS

The authors conducted a retrospective, cross-sectional study of 700 patients with chronic pain and cancer seeking treatment at an academic tertiary pain clinic. Patients completed demographic questionnaires and validated psychosocial and pain measures. Multivariable, hierarchical linear and logistic regressions assessed the relative contributions of biopsychosocial factors to the primary dependent variables of pain severity, pain interference, and opioid use.

RESULTS

Participants were 62% female and 66% White with a mean age of 59 ± 15 years, and 55% held a college degree or higher. Older age, African American or "other" race, sleep disturbance, and pain catastrophizing were significantly associated with higher pain severity (F(5,657) = 22.45; P ≤ .001; R² = 0.22). Depression, sleep disturbance, pain catastrophizing, lower emotional support, and higher pain severity were significantly associated with pain interference (F(5,653) = 9.47; P ≤ .001; R² = 0.44). Lastly, a poor cancer prognosis (Exp(B) = 1.62) and sleep disturbance (Exp(B) = 1.02) were associated with taking opioids, whereas identifying as Asian (Exp(B) = 0.48) or Hispanic (Exp(B) = 0.47) was associated with lower odds of using opioids.

CONCLUSIONS

Modifiable psychological factors-specifically sleep disturbance, depression, and pain catastrophizing-were uniquely associated with pain and opioid use in patients with chronic pain and diverse cancer diagnoses. Future behavioral pain interventions that concurrently target sleep may improve pain among patients with cancer.

LAY SUMMARY

Feeling depressed, worrying about pain, and bad sleep are related to higher pain symptoms in individuals with chronic pain and cancer. Specifically, those who struggle to sleep have worse pain and use more opioids. Also, individuals who have a bad prognosis for their cancer are more likely to be using opioid pain medications. Although race and cancer are related to chronic pain in patients, psychological well-being is also strongly related to this same pain.

Influence of the level of arterial resection on the replanting and revascularization results in hand surgery: prospective study over 22 months

The objective of this work was to assess whether the injury mechanisms are responsible for histological arterial lesions. This prospective single-center study included adults with wrist or hand arterial injury. Arterial resection of at least 2 mm from the proximal and distal stumps was performed before the arterial anastomosis. Histological analysis of the arterial stumps was performed. An ultrasound was performed 1 month postoperatively to check arterial patency. A clinical and functional evaluation was done at 1 month postoperative, then every 3 months. From 2018 to 2020, 46 patients were included with a maximum follow-up of 13 months. There were 35 cuts, 2 crush injuries, 8 amputation and 1 blast injury. Macroscopically, 37% of the margins were considered damaged. Histological analysis showed significant damage in 59% of the sections (27 out of 46 patients) with 50% for crush injury, 55% for cuts by mechanical tool, 62% for cuts by power tool, 62% for amputations and 100% for blasts. The failure rate was 9%: 2 replantations and 2 asymptomatic thromboses diagnosed by ultrasound. Postoperative pain on VAS was 1.75/10, range of motion was 87%, Quick DASH was 8%, SF36 PCS was 69% and SF36 MCS was 70%. Factors influencing the success or failure of anastomosis were the mechanism of injury (p = 0.02), associated nerve damage (p = 0.014) and length of proximal arterial cut (p = 0.046). Histological arterial lesions seem to correlate with the injury mechanism. Cuts caused by glass or crush injuries do not seem to require arterial resections of more than 2 mm. A continuation of the study with a larger number of subjects may generate statistically significant results.

Oral sedation in dentistry: evaluation of professional practice of oral hydroxyzine in the University Hospital of Rennes, France

PURPOSE

Management of a child's anxiety early in their treatment is essential in dentistry. Sedative medications are used to overcome increased anxiety from previous appointments and to promote the cooperation of children during treatment. Hydroxyzine is currently prescribed to young patients as part of the first level of conscious sedation. The main objective was to evaluate the professional practice of oral hydroxyzine, when prescribed for children presenting anxiety during dental treatment procedure performed by students and senior practitioners.

METHODS

A retrospective study of dental records and questionnaires was conducted at the Dental Care Centre of the University Hospital of Rennes, France. Parameters related to the prescription of hydroxyzine in children were evaluated as potential predictors of the dental session success, with adjustments on potential confounders.

RESULTS

The therapeutic outcome was very encouraging with 78.3% of success during dental sessions under sedation with oral hydroxyzine. Anxiety levels before the dental procedure and the medication compliance of the child were the main predictors of success. On the other hand, lower age (< 6 years old) and longer treatments (such as pulpotomy) worsened the outcome.

CONCLUSIONS

Careful analysis of the literature and results of this work showed the safety of hydroxyzine within the maximum dose authorized without adverse effects, compared to other molecules described and commonly used in dentistry. No adverse effects during dental procedure were noted. This allows for minimal sedation with efficiency for the great majority of pediatric treatment. This solution should be the first step in sedation to help practicing clinicians.

Harmonizing Wearable Biosensor Data Streams to Test Polysubstance Detection

Wearable biosensors, as a key component of wireless body area network (WBAN) systems, have extended the ability of health care providers to achieve continuous health monitoring. Prior research has shown the ability of externally placed, non-invasive sensors combined with machine learning algorithms to detect intoxication from a variety of substances. Such approaches have also shown limitations. The difficulties in developing a model capable of detecting intoxication generally include differences among human beings, sensors, drugs, and environments. This paper examines how approaching wireless communication advances and new paradigms in constructing distributed systems may facilitate polysubstance use detection. We perform supervised learning after harmonizing two types of offline data streams containing wearable biosensor readings from users who had taken different substances, accurately classifying 90% of samples. We examine time domain and frequency domain features and find that skin temperature and mean acceleration are the most important predictors.

Epidemiological and immunological features of obesity and SARS-CoV-2

Obesity is a key correlate of severe SARS-CoV-2 outcomes while the role of obesity on risk of SARS-CoV-2 infection, symptom phenotype, and immune response are poorly defined. We examined data from a prospective SARS-CoV-2 cohort study to address these questions. Serostatus, body mass index, demographics, comorbidities, and prior COVID-19 compatible symptoms were assessed at baseline and serostatus and symptoms monthly thereafter. SARS-CoV-2 immunoassays included an IgG ELISA targeting the spike RBD, multiarray Luminex targeting 20 viral antigens, pseudovirus neutralization, and T cell ELISPOT assays. Our results from a large prospective SARS-CoV-2 cohort study indicate symptom phenotype is strongly influenced by obesity among younger but not older age groups; we did not identify evidence to suggest obese individuals are at higher risk of SARS-CoV-2 infection; and, remarkably homogenous immune activity across BMI categories suggests natural- and vaccine-induced protection may be similar across these groups.

Characterizing Trends in Synthetic Cannabinoid Receptor Agonist Use from Patient Clinical Evaluations during Medical Toxicology Consultation

Synthetic cannabinoid receptor agonists (SCRAs) are a new class of compounds with profound psychoactive effects and potential toxicity. This study characterizes patterns in SCRA abuse using qualitative interviews with individuals receiving medical toxicology consultation. Patients with suspected exposure to a new psychoactive substance were interviewed by medical toxicologists upon presentation for acute care. Investigators collected clinical and qualitative data including knowledge, attitudes, beliefs, and practices related to psychoactive substance use. Responses were categorized by identifying themes, and statistics were generated to describe patterns of use. Overall, 69% (86) of the 124 cases of novel psychoactive substance use entered into the registry were associated with exposure to SCRAs. Most patients (68.8%) had used SCRAs at least once before the presenting episode. 47.7% considered SCRAs to be very easy to obtain, and 44.2% reported paying for the substances while 32.6% acquired it for free. Nearly half (48.8%) of patients reported their primary reason for use was to get high; a small proportion used SCRAs to avoid testing positive on drug screening (6.9%) or as an alternative to marijuana (4.6%). Findings suggest an independent and stable culture is developing around the use of SCRAs separate from their appeal as an "undetectable" alternative to marijuana.

Self-Report Data on Regular Consumption of Illicit Drugs and HIV Risk Behaviors after Kratom (Mitragyna Speciosa korth.) Initiation among Illicit Drug Users in Malaysia

This study sought to determine the relationship between kratom (Mitragyna speciosa) initiation and regular consumption of illicit drugs and HIV risk behaviors in a cohort of illicit drug users in Malaysia. 260 illicit drug users with current kratom use were recruited through convenience sampling for this cross-sectional study. All were male, with the majority being Malays (95%, n = 246/260). Results suggest that kratom initiation was associated with significant decrease in the regular use of heroin (odds ratio (OR) = 0.50, 95% confidence interval (CI): 0.40- 0.72; p = .0001), methamphetamine (OR = 0.23, CI: 0.16- 0.35; p < .0001), and amphetamine (OR = 0.17, CI: 0.09- 0.34; p < .0001). Kratom initiation was also associated with reduction in regular HIV risk behaviors such as having sex with sex workers (OR = 0.20, CI: 0.12-0.32; p < .0001), using drugs before sexual intercourse (OR = 0.20, CI: 0.13- 0.31; p < .0001), injecting behaviors (OR = 0.10, CI: 0.04- 0.25; p < .0001), sharing of injection equipment (OR = 0.13, CI: 0.04- 0.43; p < .0001), and injecting with other injection drug users (IDUs) (OR = 0.07, CI: 0.02- 0.24; p < .0001).

Self-reported prevalence and severity of opioid and kratom (Mitragyna speciosa korth.) side effects

ETHNOPHARMACOLOGICAL RELEVANCE

Mitragyna speciosa (Korth.) is a traditional medicinal plant widely used in Southeast Asia for its opioid-like effects. Although kratom produces analgesia through binding of mitragynine and other alkaloids at the mu-opioid receptor (MOR), the association of long-term kratom use with adverse opioid-like effects remains unknown.

AIM OF THE STUDY

To determine the self-reported prevalence and severity of opioid-related adverse effects after kratom initiation in a cohort of illicit opioid users.

MATERIALS AND METHODS

A total of 163 illicit opioid users with current kratom use history were recruited through convenience sampling from the northern states of Peninsular Malaysia. Face-to-face interviews were conducted using a semi-structured questionnaire.

RESULTS

Respondents were all males, majority Malays (94%, n = 154/163), with a mean age of 37.10 years (SD = 10.9). Most were single (65%, n = 106/163), had 11 years of education (52%, n = 85/163) and employed (88%, n = 144/163). Half reported using kratom for over >6 years (50%, n = 81/163), and 41% consumed >3 glasses of kratom daily (n = 67/163). Results from Chi-square analysis showed kratom initiation was associated with decreased prevalence of respiratory depression, constipation, physical pain, insomnia, depression, loss of appetite, craving, decreased sexual performance, weight loss and fatigue.

CONCLUSIONS

Our findings indicate that kratom initiation (approximately 214.29 mg of mitragynine) was associated with significant decreases in the prevalence and severity of opioid adverse effects.

A technology-augmented intervention to prevent peer violence and depressive symptoms among at-risk emergency department adolescents: Protocol for a randomized control trial

BACKGROUND

Peer violence and depressive symptoms are increasingly prevalent among adolescents, and for many, use the emergency department (ED) as their primary source of healthcare. Brief in-person interventions and longitudinal text-message-based interventions are feasible, acceptable, and may be effective in reducing peer violence and depressive symptoms when delivered in the ED setting. This paper presents the study design and protocol for an in-ED brief intervention (BI) and text messaging program (Text).

METHODS

This study will be conducted in a pediatric ED which serves over 50,000 pediatric patients per year. Recruitment of study participants began in August 2018 and anticipated to continue until October 2021. The study will enroll 800 adolescents (ages13-17) presenting to the ED for any reason who self-report past-year physical peer violence and past-two week mild-to-moderate depressive symptoms. The study will use a factorial randomized trial to test both overall intervention efficacy and determine the optimal combination of intervention components. A full 2 × 2 factorial design randomizes patients at baseline to 1) BI or no BI; and 2) Text or no Text. Peer violence and depressive symptoms improvements will be measured at 2, 4, and 8 months through self-report and medical record review.

DISCUSSION

This study has important implications for the progress of the greater field of mobile health interventions, as well as for adolescent violence and depression prevention in general. This proposal has high clinical and public health significance with high potential scalability, acceptability, and impact.

Designing a minimally-invasive, ultrasound-guided, percutaneous flexor tendon sheath lavage technique: a cadaver study

The goal of this study was to develop a minimally-invasive, ultrasound-guided percutaneous flexor tendon sheath lavage technique on cadaver model. Two catheters were inserted using ultrasound guidance at the proximal and distal ends of the tendon sheath in 20 fingers from cadaveric forearms. Percutaneous injection of a saline solution colored with methylene blue resulted in anterograde lavage of the flexor tendon sheath. The technique was successful in 13 out of 20 cases. The proximal catheter was in the correct position in 17 cases and the distal catheter was correctly positioned in 15 cases. The flexor tendons were continuous in all cases and had puncture wounds in 9 cases. Based on our study, this minimally-invasive, ultrasound-guided percutaneous lavage of the flexor tendon sheath was effective in 65% of cases and safe in 100% of cases in the index, middle and ring fingers. If this percutaneous lavage fails, it is always possible to switch to a conventional open technique.

Recognition and Management of Pediatric Salt Toxicity

OBJECTIVES

Immediate recognition of salt toxicity and aggressive resuscitative measures are critical in the treatment of this lethal poisoning. Despite heroic measures, pediatric deaths due to salt toxicity still occur from irreversible neurological damage. The objective of this article is to review the relevant literature and offer a therapeutic algorithm for the management of pediatric patients presenting with salt toxicity.

METHODS

A literature search for cases of salt toxicity was conducted. Articles in English that were available electronically through PubMed and Google Scholar were reviewed.

RESULTS

Nineteen cases and case series of salt toxicity were located using our search strategy. Salt poisoning has a distinct pathophysiology compared with hypernatremia, most notable for the lack of formation of idiogenic osmoles.

CONCLUSIONS

The approach to treatment differs between salt toxicity and hypernatremia, focusing on rapid correction of serum osmolality rather than gradual normalization of serum sodium concentrations. Consultation of nephrology and child protection services are strongly recommended in the comprehensive treatment approach.

Over the influence: The HIV care continuum among methamphetamine-using men who have sex with men

BACKGROUND

HIV-positive persons who use stimulants such as methamphetamine experience greater difficulties in navigating the HIV care continuum. In the era of HIV treatment as prevention (TasP), little is known about the prevalence and correlates of success along the HIV care continuum among people who use stimulants.

SETTING

San Francisco, California USA METHODS: Cross-sectional study that enrolled 129 HIV-positive men who have sex with men (MSM) from 2013 through 2017 who had biologically confirmed, recent methamphetamine use. Multivariable logistic regressions were built to identify correlates of success across the HIV care continuum.

RESULTS

Although two-thirds (87/129) of participants had undetectable HIV viral load (<40 copies/mL), only one-in-four (32/129) reported taking at least 90% of their antiretroviral therapy (ART). Those who were homeless in the past year (adjusted odds ratio [aOR] = 0.20; 95% CI = 0.06-0.65) had 80% lower odds of being undetectable and adherent to ART. Substance use disorder treatment was associated with 77% lower odds of being engaged in HIV care (aOR = 0.23; 95% CI = 0.06-0.84) but also close to 3-fold greater odds of being adherent to ART (aOR = 2.91; 95% CI = 1.12-7.60).

CONCLUSION

Despite the fact that many HIV-positive, methamphetamine-using MSM are able to achieve undetectable viral load in this sample, difficulties with ART adherence threaten to undermine the clinical and public health benefits of TasP. Expanded efforts to boost the effectiveness of TasP in this population should focus on meeting the unique needs of homeless individuals, optimizing ART adherence, and facilitating the integration of HIV care with substance use disorder treatment.

Two-team management of vascular injuries concomitant with osteo-articular injuries in 36 patients over six years

BACKGROUND

Patients with both vascular and osteoarticular injuries require multidisciplinary management. Vascular injuries may be function- and/or life-threatening. The lower limbs are predominantly affected. Traffic, domestic, and work-related accidents contribute most of the cases. The primary objective of this study was to describe the management of patients with concomitant vascular and osteo-articular injuries, with special attention to the rates of amputation and fasciotomy. The secondary objective was to suggest a management sequence to optimise our surgical practice.

HYPOTHESIS

The management sequence is a crucial consideration in patients with both vascular and osteo-articular injuries.

MATERIAL AND METHODS

A 6-year, retrospective, observational study was conducted in patients with concomitant vascular and osteo-articular injuries.

RESULTS

The study included 36 patients with a mean age of 40.6±22.1 years. The main sources of injury were traffic accidents (n=19, 52.8%), crush injury (n=8, 22.2%), and falls (n=5, 13.9%). A compound fracture was present in 20 (55.6%) patients. Evidence of ischaemia in 25 (69.4%) patients, and bleeding in 11 (30.6%) patients. Pre-operative imaging, by ultrasonography or computed tomography, was performed in 27 (75.0%) patients. The lower limb was involved in 30 (83.3%) patients, who had osteoarticular injuries to the femur and leg combined with injury to the popliteal artery. Fasciotomy was performed in 11 (30.6%) patients and secondary amputation in 7 (19.4%) patients. The limb salvage rate was 80.6%. Median patient survival was 9.3 [0-74.8] months.

DISCUSSION

Coordinated work by two surgical teams is crucial to manage concomitant vascular and osteo-articular injuries. The management sequence must be defined clearly. Computed tomography angiography is the investigation of choice and should be performed at the slightest suspicion of vascular injury.

LEVEL OF EVIDENCE

IV, retrospective observational study.

Automatic Detection of Opioid Intake Using Wearable Biosensor

A plethora of research shows that recreational drug overdoses result in major social and economic consequences. However, current illicit drug use detection in forensic toxicology is delayed and potentially compromised due to lengthy sample preparation and its subjective nature. With this in mind, scientists have been searching for ways to create a fast and easy method to detect recreational drug use. Therefore, we have developed a method for automatic detection of opioid intake using electrodermal activity (EDA), skin temperature and tri-axis acceleration data generated from a wrist worn biosensor. The proposed system can be used for home and hospital use. We performed supervised learning and extracted 23 features using time and frequency domain analysis to recognize pre- and post- opioid health conditions in patients. Feature selection procedures are used to reduce the number of features and processing time. For supervised learning, we compared three classifiers and selected the one with highest accuracy and sensitivity: decision tree, k-nearest neighbors (KNN) and eXtreme Gradient Boosting utilizing modified features. The results show that the proposed method can detect opioid use in real-time with 99% accuracy. Moreover, this method can be applied to identify other use of additional substances other than opioids. The numerical analysis is completed on data collected from 30 participants over a span of 4 months.

Unsuspected Clenbuterol Toxicity in a Patient Using Intramuscular Testosterone

Clenbuterol is a beta-agonist that has been abused by fitness-oriented individuals for muscle growth and weight loss. We report a case of a 46-year-old man who presented tachycardic, hypokalemic, and hyperglycemic after injecting testosterone obtained from Brazil. He developed refractory hypotension and was started on an esmolol infusion for suspected beta-agonist toxicity. Laboratory analysis showed a detectable clenbuterol serum concentration. Analysis of an unopened ampule contained boldenone undecylenate, clenbuterol, and vitamin E. This case illustrates a novel exposure that caused beta-agonist toxicity and was treated successfully with rapid-onset beta blocker.

A New Mining Method to Detect Real Time Substance Use Events from Wearable Biosensor Data Stream

Detecting real time substance use is a critical step for optimizing behavioral interventions to prevent drug abuse. Traditional methods based on self-reporting or urine screening are inefficient or intrusive for drug use detection, and inappropriate for timely interventions. For example, self-report suffers from distortion or recall bias; while urine screening often detects drug use that occurred only within the previous 72 hours. Methods for real-time substance use detection are severely underdeveloped, partly due to the novelty of wearable biosensor technique and the lack of substantive clinical data for evaluation. We propose a new real-time drug use event detection method using data obtained from wearable biosensors. Specifically, this method is built upon the slide window technique to process the data stream, and a distance-based outlier detection method to identify substance use events. This novel method is designed to examine how to detect and set up the thresholds of parameters in real-time drug use event detection for wearable biosensor data streams. Our numerical analyses empirically identified the thresholds of parameters used to detect the cocaine use and showed that this proposed method could be adapted to detect other substance use events.

Radiation exposure and the orthopedic surgeon's hand: Measurement of the equivalent dose over 13 months

Exposure to ionizing radiation in the operating room is governed by practical prevention and protection measures on the international, national and local levels. We evaluated the equivalent dose to the hand of an orthopedic surgeon over 13 months. An orthopedic surgeon wore a ring dosimeter on the ring finger of his right hand for all surgical procedures requiring intraoperative fluoroscopy between March 2014 and April 2015. Monthly doses were evaluated by the IRSN over the study period. The number and type of procedures were compiled as well as the type of fluoroscopy unit used. Four hundred procedures were performed during this period, including 182 with fluoroscopy. The equivalent cumulative dose at the hand was 4,75 mSv. No correlation was found with the type of procedure or type of fluoroscopy unit (conventional or mini C-arm). Equivalent doses were below the annual regulatory limit in France of 500 mSv. These results are consistent with those reported in the literature. However, recent studies have noted that both younger surgeons in training and more experienced surgeons must remember to use radiation protection measures.

[Treatment of extra-articular distal radius fractures in active elderly patients]

Extra-articular distal radius fractures in active elderly patients are common and predominantly affect females. The high number of patients lost to follow-up compromises the evaluation of outcomes. Treatment aims to control the comminution and allow fast recovery of pre-injury activity levels. Fixation with volar locking plates is the gold standard. The role of bone substitutes in this type of injury is unclear.

A Depression Prevention Intervention for Adolescents in the Emergency Department

PURPOSE

To evaluate acceptability and feasibility of a theoretically based two-part (brief in-person + 8-week automated text message) depression prevention program, "intervention for DepressiOn and Violence prevention in the Emergency department" (iDOVE), for high-risk adolescents.

METHODS

English-speaking emergency department (ED) patients (age 13-17, any chief complaint) were sequentially approached for consent on a convenience sample of shifts and screened for inclusion based on current depressive symptoms and past-year violence. After consent, baseline assessments were obtained; all participants were enrolled in the two-part intervention (brief in-ED + 8-week two-way text messaging). At 8 weeks, quantitative and qualitative follow-up assessments were obtained. Measures included feasibility, acceptability, and preliminary data on efficacy. Qualitative data were transcribed verbatim, double coded, and interpreted using thematic analysis. Quantitative results were analyzed descriptively and with paired t tests.

RESULTS

As planned, 16 participants (eight each gender) were recruited (75% of those who were eligible; 66% nonwhite, 63% low income, mean age 15.4). The intervention had high feasibility and acceptability: 93.8% completed 8-week follow-up; 80% of daily text messages received responses; 31% of participants requested ≥1 "on-demand" text message. In-person and text message portions were rated as good/excellent by 87%. Qualitatively, participants articulated: (1) iDOVE was welcome and helpful, if unexpected in the ED; (2) the daily text message mood assessment was "most important"; (3) content was "uplifting"; and (4) balancing intervention "relatability" and automation was challenging. Participants' mean ΔBDI-2 (Beck Depression Inventory) from baseline to 8-week follow-up was -4.9, (p = .02).

CONCLUSIONS

This automated preventive text message intervention is acceptable and feasible. Qualitative data emphasize the importance of creating positive, relevant, and interactive digital health tools for adolescents.

PTSD, cyberbullying and peer violence: prevalence and correlates among adolescent emergency department patients

OBJECTIVE

Posttraumatic stress disorder (PTSD) is often underdiagnosed and undertreated among adolescents. The objective of this analysis was to describe the prevalence and correlates of symptoms consistent with PTSD among adolescents presenting to an urban emergency department (ED).

METHODS

A cross-sectional survey of adolescents aged 13-17 years presenting to the ED for any reason was conducted between August 2013 and March 2014. Validated self-report measures were used to measure mental health symptoms, violence exposure and risky behaviors. Multivariate logistic regression analysis was performed to determine adjusted differences in associations between symptoms consistent with PTSD and predicted correlates.

RESULTS

Of 353 adolescents, 23.2% reported current symptoms consistent with PTSD, 13.9% had moderate or higher depressive symptoms and 11.3% reported past-year suicidal ideation. Adolescents commonly reported physical peer violence (46.5%), cyberbullying (46.7%) and exposure to community violence (58.9%). On multivariate logistic regression, physical peer violence, cyberbullying victimization, exposure to community violence, female gender and alcohol or other drug use positively correlated with symptoms consistent with PTSD.

CONCLUSIONS

Among adolescents presenting to the ED for any reason, symptoms consistent with PTSD, depressive symptoms, physical peer violence, cyberbullying and community violence exposure are common and interrelated. Greater attention to PTSD, both disorder and symptom levels, and its cooccurring risk factors is needed.

PULSE-SMART: Pulse-Based Arrhythmia Discrimination Using a Novel Smartphone Application

BACKGROUND

Atrial fibrillation (AF) is a common and dangerous rhythm abnormality. Smartphones are increasingly used for mobile health applications by older patients at risk for AF and may be useful for AF screening.

OBJECTIVES

To test whether an enhanced smartphone app for AF detection can discriminate between sinus rhythm (SR), AF, premature atrial contractions (PACs), and premature ventricular contractions (PVCs).

METHODS

We analyzed two hundred and nineteen 2-minute pulse recordings from 121 participants with AF (n = 98), PACs (n = 15), or PVCs (n = 15) using an iPhone 4S. We obtained pulsatile time series recordings in 91 participants after successful cardioversion to sinus rhythm from preexisting AF. The PULSE-SMART app conducted pulse analysis using 3 methods (Root Mean Square of Successive RR Differences; Shannon Entropy; Poincare plot). We examined the sensitivity, specificity, and predictive accuracy of the app for AF, PAC, and PVC discrimination from sinus rhythm using the 12-lead EKG or 3-lead telemetry as the gold standard. We also administered a brief usability questionnaire to a subgroup (n = 65) of app users.

RESULTS

The smartphone-based app demonstrated excellent sensitivity (0.970), specificity (0.935), and accuracy (0.951) for real-time identification of an irregular pulse during AF. The app also showed good accuracy for PAC (0.955) and PVC discrimination (0.960). The vast majority of surveyed app users (83%) reported that it was "useful" and "not complex" to use.

CONCLUSION

A smartphone app can accurately discriminate pulse recordings during AF from sinus rhythm, PACs, and PVCs.

Advanced molecular biologic techniques in toxicologic disease

The advancement of molecular biologic techniques and their capabilities to answer questions pertaining to mechanisms of pathophysiologic events have greatly expanded over the past few years. In particular, these opportunities have provided researchers and clinicians alike the framework from with which to answer clinical questions not amenable for elucidation using previous, more antiquated methods. Utilizing extremely small molecules, namely microRNA, DNA, protein, and nanoparticles, we discuss the background and utility of these approaches to the progressive, practicing physician. Finally, we consider the application of these tools employed as future bedside point of care tests, aiding in the ultimate goal of unsurpassed patient care.

Ethylene glycol elimination kinetics and outcomes in patients managed without hemodialysis

STUDY OBJECTIVE

Ethylene glycol remains an important toxic cause of metabolic acidosis and acute renal failure. Traditionally, inhibition of alcohol dehydrogenase along with hemodialysis has been used for treatment. Because of reported long elimination half-life of ethylene glycol during alcohol dehydrogenase inhibition, hemodialysis has been used in patients who are otherwise doing well to clear ethylene glycol. We study ethylene glycol elimination kinetics in patients treated with fomepizole, but without hemodialysis.

METHODS

This was a retrospective, multicenter cohort study of patients older than 15 years who were treated at one of 3 medical centers during an 8-year period. Inclusion criteria were peak serum ethylene glycol concentration greater than 20 mg/dL, lack of renal failure on admission, treatment with fomepizole but without hemodialysis, and availability of serial serum ethylene glycol concentrations, allowing calculation of elimination half-life. The primary outcome variable was ethylene glycol elimination half-life; mortality and onset of renal failure were secondary outcome variables.

RESULTS

During the study period, 85 patients were treated for ethylene glycol toxicity, of whom 40 met inclusion criteria. The mean serum ethylene glycol elimination half-life was 14.2 hours (SD=3.7 hours; 95% confidence interval 13.1 to 15.3 hours). One patient presented with metabolic acidosis on admission and developed mild transient renal insufficiency but did not require hemodialysis. No patient died.

CONCLUSION

The mean elimination half-life of ethylene glycol in this population was shorter than previously reported without hemodialysis, and this select group of patients did well without enhanced elimination by hemodialysis.

Profiles of importance, readiness and confidence in quitting tobacco use

OBJECTIVE

This study examined whether rulers of importance, readiness and confidence (IRC) in quitting smoking could be used to identify subgroups of smokers, with the future goal of potentially tailoring interventions to specific readiness profiles.

METHODS

Consecutive emergency department patients ≥18 years old were considered for enrolment. Participants provided information on their tobacco use and motivation to quit smoking using 10-point IRC rulers. We used latent profile analysis on the IRC rulers to identify subgroups of smokers and examined associations between profile membership and participant's nicotine dependence and demographics.

RESULTS

A total of 1549 patients were screened, yielding a sample of 609 tobacco users. According to statistical fit indices, a four-profile solution fits best: 32% displayed maximum importance and readiness with strong confidence, 43% of the sample displayed relatively average levels of all three variables, 17% displayed below average importance with least favourable readiness and confidence and 7% displayed least favourable importance and readiness but relatively high confidence. Profiles were then shown to differ on nicotine dependence and educational level.

CONCLUSIONS

Four distinct profiles of IRC responses were observed. Identifying and describing these patterns has the potential to enhance future targeted intervention efforts and has implications for theory development.

Intersection of chronic pain treatment and opioid analgesic misuse: causes, treatments, and policy strategies

Treating chronic pain in the context of opioid misuse can be very challenging. This paper explores the epidemiology and potential treatments for chronic pain and opioid misuse and identifies educational and regulation changes that may reduce diversion of opioid analgesics. We cover the epidemiology of chronic pain and aberrant opioid behaviors, psychosocial influences on pain, pharmacological treatments, psychological treatments, and social treatments, as well as educational and regulatory efforts being made to reduce the diversion of prescription opioids. There are a number of ongoing challenges in treating chronic pain and opioid misuse, and more research is needed to provide strong, integrated, and empirically validated treatments to reduce opioid misuse in the context of chronic pain.

Case files of the University of Massachusetts fellowship in medical toxicology: lethal dose of opioids contained in an elastomeric capsule labeled as vancomycin

A 67 year-old male presented to the emergency department with alteration in mental status. On arrival he had vital signs: pulse 110, BP 173/83, respiratory rate 4, oxygen saturation 57% and temperature 36.1 degrees Celsius. His past medical history included hypertension, vitamin B12 deficiency, hyperlipidemia, and recurrent cellulitis treated with vancomycin. The patient had no response to noxious stimuli, pinpoint pupils, and agonal respirations. Secondary to his wife's vehement denial that he had access to or history of using any narcotics, he was intubated after 2.2mg IV naloxone failed to reverse respiratory depression. Thirty minutes before presentation, however, he had received an intravenous infusion of vancomycin administered by his wife at home. The vancomycin, obtained from a home infusion medication supply company, was contained in one of five sealed elastomeric capsules delivered earlier that day. A qualitative comprehensive toxicology screen of urine for 1043 substances identified morphine, codeine, naloxone, lidocaine and caffeine. The original elastomeric container was not available for testing, but another container from the same delivery was submitted for testing to the state forensic laboratory. This intact container was labeled as Vancomycin 1g in 240mL of normal saline. The forensic laboratory confirmed that the alkaloidal contents of the elastomeric capsule were 10% codeine, 4.4% 6-monoacetyl morphine, and 84% morphine. No vancomycin was identified in the infusion bottles. The case was referred to the local police department and the state department of health drug control board. The home infusion company was also immediately notified to prevent similar occurrence.

CONCLUSION

We are reporting the first known case of opioid overdose from an adulterated elastomeric capsule that was labeled as containing an antimicrobial agent.

Lyme meningoradiculitis: prospective evaluation of biological diagnosis methods

The symptoms of Lyme meningoradiculitis and the value of biological examinations in an endemic area were determined in a prospective study in which data were collected on all patients consecutively hospitalised for Lyme meningoradiculitis at our institution during an 18-month period. Specific antibody titres in the serum and cerebrospinal fluid (CSF) were determined by Vidas enzyme-linked-immunosorbent-assay (IgG + IgM), Dade-Behring enzyme immunoassay (EIA) (IgM; IgG) and Western blot analysis (IgG). We also searched for Borrelia burgdorferi in the CSF by PCR analysis and following culture on a specific medium. A control group was recruited, consisting of 16 consecutive patients who had been referred during the same period with suspected but not confirmed Lyme meningoradiculitis. Eleven patients were included. Borrelia EIA of the serum revealed that 40% of the patients had both elevated specific IgM titres and intrathecal synthesis of specific IgG; 40% of the patients was negative for IgM but had isolated intrathecal synthesis of IgG; 20% of the patients had elevated specific IgM titres without intrathecal synthesis of IgG. PCR analysis and the CSF culture were positive in one case only (B. garinii). The results of this study highlight the importance of systematic serological testing for B. burgdorferi in the CSF in the case of early neuroborreliosis suspicion, even in the absence of IgM serum antibodies, which was the case in 40% of the patients in the present study. Nevertheless, intrathecal anti-B. burgdorferi IgG synthesis, which remains the "gold standard" for the diagnosis of neuroborreliosis, was not detectable in 20% of the patients for whom diagnosis was subsequently confirmed by demonstration of specific serum IgM.

Hyperinsulinemia-euglycemia therapy: a useful tool in treating calcium channel blocker poisoning

Hyperinsulinemia-euglycemia (HIE) therapy, when initiated promptly and aggressively, may offer considerable advantages in the treatment of calcium channel blocker poisoning. Although its mechanism of action is uncertain, HIE improves the efficiency with which the poisoned myocardium uses metabolic fuel, the end result of which is improvements in inotropy and other cardiovascular parameters. Although HIE is not universally accepted, the reports included in the previous issue of Critical Care should prompt clinicians to consider HIE an appropriate therapy specifically for calcium channel blocker poisoning.

Issues in the management of dietary supplement use among hospitalized patients

Herbs and dietary supplements (HDS) are in widespread use in the United States, and are especially prevalent among chronically ill patients. This population is more likely to be admitted to health care facilities where they may continue to use HDS. The risk of adverse effects from HDS used during admission places significant liability on clinicians and hospitals. We describe the response of health care facilities in the Boston, Massachusetts area to this problem, and propose elements of a hospital policy which increases patient safety and satisfaction and minimizes the likelihood for adverse effects from HDS.

Pneumocystis carinii pneumonia in patients with hematologic malignancies: a descriptive study

Objectives. A retrospective multicentric study was conducted over a five-year period to evaluate the clinical and laboratory characteristics and outcome of patients with proven Pneumocystis carinii pneumonia (PCP) complicating hematologic malignancies.Results. The study included 60 HIV-negative patients with 18 non-Hodgkin's malignant lymphoma (30%), 13 chronic lymphocytic leukaemia (21.7%), 10 acute leukemia (16.6%), 5 multiple myeloma (8.3%), 4 Waldenström's diseases (6.6%), 4 chronic myeloid leukemia (6.6%), 3 myelodysplasia (5%), 2 Hodgkin's diseases (3.3%) and 1 thrombopenia. Bronchoalveolar lavage was diagnostic in all patients. Forty-nine patients received cytotoxic drugs (81.7%), 25 (41.7%) a long-term corticotherapy and 15 (25%) underwent bone marrow transplantation. Twenty-seven patients (45%) required admission in the intensive care unit, 35 (58.3%) received an adjunctive corticotherapy and 18 mechanical ventilation (30%). Twenty patients (33.3%) died of PCP. A previous long-term corticotherapy (p=0.04), high respiratory (p=0.05) and pulse rates (p=0.02), elevated C reactive protein (p=0.01) and mechanical ventilation (OR=13.37; IC: 1.9-50) were associated with a poor prognosis. Adjunctive corticotherapy did not modify the prognosis.Conclusions. These results suggest that PCP can occur during the course of various hematologic malignancies, not only lymphoproliferative disorders. Prognosis remains poor. The diagnosis should be advocated more frequently and earlier to improve the prognosis.

Acquisition of Mn(II) in addition to Fe(II) is required for full virulence of Salmonella enterica serovar Typhimurium

The roles of the genes feoB (ABC ferrous iron transporter), mntH (proton-dependent manganese transporter), and sitABCD (putative ABC iron and/or manganese transporter) in Salmonella pathogenicity were investigated by using mutant strains deficient in one, two, or three transporters. Our results indicated that sitABCD encodes an important transporter of Mn(II) and Fe(II) which is required for full virulence in susceptible animals (Nramp1(-/-)) and for replication inside Nramp1(-/-) macrophages in vitro. The mntH sitABCD double mutant (mutant MS) showed minimal Mn(II) uptake and increased sensitivity to H(2)O(2) and to the divalent metal chelator 2,2'-dipyridyl (DP) and was defective for replication in macrophages. In vivo MS appeared to be as virulent as the sitABCD mutant in Nramp1(-/-) animals. The ferrous iron transporter Feo was required for full virulence in 129/Sv Nramp1(-/-) mice, and infection with multiple mutants lacking FeoB was not fatal. The sitABCD feoB mutant (mutant SF) and the mntH sitABCD feoB mutant (mutant MSF) showed minimal Fe(II) uptake and were slightly impaired for replication in susceptible macrophages. MSF showed reduced growth in minimal medium deficient in divalent cations. The role of the mntH gene, which is homologous to mammalian Nramp genes, was also investigated after overexpression in the double mutant MS. MntH preferred Mn(II) over Fe(II) and could suppress MS sensitivity to H(2)O(2) and to DP, and it also improved the intracellular survival in Nramp1(-/-) macrophages. This study indicates that acquisition of Mn(II), in addition to Fe(II), is required for intracellular survival and replication of Salmonella enterica serovar Typhimurium in macrophages in vitro and for virulence in vivo.

Novel locus required for expression of high-level macrolide-lincosamide-streptogramin B resistance in Staphylococcus aureus

The yycF1(Ts) mutation in Staphylococcus aureus conferred hypersensitivity to macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics on strains either containing or lacking ermB. The overexpression of the S. aureus Ssa protein restored the yycF1 mutant to wild-type levels of susceptibility. Inactivation of ssa in an unmutagenized strain dramatically reduced ermB-based resistance. Conditional loss of function or expression of ssa in the yycF1 mutant is proposed to result in the observed hypersensitivity to MLS(B) antibiotics.

Polyphyletic origins of bacterial Nramp transporters

The redox-active metals iron and manganese are required for energy metabolism, protection against oxidative stress and defense against infections. In eukaryotes, both divalent metals are transported by Nramp transporters. The sequence of these transporters was remarkably conserved during evolution. Several bacterial Nramp homologs (MntH) are also proton-dependent manganese transporters. Here, we present phylogenetic evidence for the polyphyletic origins of three groups of MntH proteins and for possible Nramp horizontal gene transfer with eukaryotes. We propose that the evolution of the MntH/Nramp family is related to adaptation to oxidative environments, including those arising during infection of animals and plants.

Use of a genetic approach to evaluate the consequences of inhibition of efflux pumps in Pseudomonas aeruginosa

Drug efflux pumps in Pseudomonas aeruginosa were evaluated as potential targets for antibacterial therapy. The potential effects of pump inhibition on susceptibility to fluoroquinolone antibiotics were studied with isogenic strains that overexpress or lack individual efflux pumps and that have various combinations of efflux- and target-mediated mutations. Deletions in three efflux pump operons were constructed. As expected, deletion of the MexAB-OprM efflux pump decreased resistance to fluoroquinolones in the wild-type P. aeruginosa (16-fold reduction for levofloxacin [LVX]) or in the strain that overexpressed mexAB-oprM operon (64-fold reduction for LVX). In addition to that, resistance to LVX was significantly reduced even for the strains carrying target mutations (64-fold for strains for which LVX MICs were >4 microg/ml). We also studied the frequencies of emergence of LVX-resistant variants from different deletion mutants and the wild-type strain. Deletion of individual pumps or pairs of the pumps did not significantly affect the frequency of emergence of resistant variants (at 4x the MIC for the wild-type strain) compared to that for the wild type (10(-6) to 10(-7)). In the case of the strain with a triple deletion, the frequency of spontaneous mutants was undetectable (<10(-11)). In summary, inhibition of drug efflux pumps would (i) significantly decrease the level of intrinsic resistance, (ii) reverse acquired resistance, and (iii) result in a decreased frequency of emergence of P. aeruginosa strains highly resistant to fluoroquinolones in clinical settings.

[Cutaneous Scedosporium infection revealed by bullous-necrotic purpura]

BACKGROUND

Non-mycetomatous cutaneous scedosprium is an uncommon mycosis observed in immunodepressed subjects. We report a case with an inaugural presentation of bullous and necrotic purpura.

CASE REPORT

A 79-year-old man on intermittent corticosteroid therapy for bronchospasm was admitted for bullous and necrotic purpura and fever. Subcutaneous nodules with a sporotrichoid aspect developed despite wide-spectrum antibiotics. Microbiology samples cultured on Sabouraud medium evidenced Scedosporium apiospermum. The pathogenic nature of the infection was proven on a skin biopsy showing numerous myceleal filaments with Gomori-Grocott staining despite negative PAS. No pulmonary involvement was evidenced. The patient was treated unsuccessfully with itraconazole. A Pseudomonas lung infection was fatal.

DISCUSSION

Scedosporium apiospermum, an ubiquitous ascomycetes anamorphous to Pseudallescheria boydii, is the cause of a growing number of human infections due to widespread use of immunosuppressors. Skin and lung localizations predominate. The inaugural bullous and necrotic purpural skin manifestations in this case are unusual. In addition, the patient was only minimally immunodepressed and despite demonstrated in vitro sensitivity, itraconazole was ineffective clinically. Treatment is not well defined, but surgery is essential in combination with empirically chosen antifungals.

Genotypic changes in human immunodeficiency virus type 1 associated with loss of suppression of plasma viral RNA levels in subjects treated with ritonavir (Norvir) monotherapy

Ten subjects received 600 to 1,200 mg of the human immunodeficiency virus type 1 (HIV-1) protease inhibitor ritonavir per day. Following 2 weeks of therapy, plasma HIV RNA levels decreased by a mean of 1. 57 (range, 0.89 to 1.96) log units. With continued therapy, HIV RNA levels began to rise in eight subjects. The initial rise in plasma RNA levels was temporally associated with the development and quantitative increase in the V82 resistance mutation. Doubling times of the V82A mutant virus were estimated to be 2.4 to 4.8 days. An L63P/A mutation was commonly present at baseline even in subjects with a durable virologic response. The concomitant acquisition of an L63P/A mutation with the V82A/F mutation at the time when plasma RNA levels rebounded suggests a role for the L63P/A mutation in improving the fitness of the V82A/F mutation. Subsequent additional genotypic changes at codons 54 and 84 were often associated with further increases in plasma RNA levels. Ongoing viral replication in the presence of drugs resulted in the appearance of additional genotypic changes, including the L90M saquinavir resistance mutation, and decreased phenotypic susceptibility. The relative fitness of the protease V82A ritonavir resistance mutation and reverse transcriptase T215Y/F zidovudine resistance mutation following drug withdrawal were estimated to be 96 to 98% that of the wild type. Durability of the virologic response was associated with plasma RNA levels at the nadir. A virologic response beyond 60 days was not observed unless plasma HIV RNA levels were suppressed below 2,000 copies/ml, consistent with estimates from V82A doubling times for selection of a single resistance mutation to dominate the replicating population.