Use of Topical Anesthetics in the Management of Patients With Simple Corneal Abrasions: Consensus Guidelines From the American College of Emergency Physicians

The management of corneal abrasions has largely excluded dispensing topical local anesthetics for home use due to concern for corneal toxicity. We have reviewed and critically appraised the available literature evidence regarding the use of topical anesthetics in patients with simple corneal abrasions. Using sequential Delphi review, we have developed these clinical guidelines. Herein are evidentiary summaries and consensus recommendations for 8 specific relevant questions. Our key observation is that for only simple corneal abrasions, as diagnosed and treated in accordance with the full protocol described herein, it appears safe to prescribe or otherwise provide a commercial topical anesthetic (ie, proparacaine, tetracaine, oxybuprocaine) for use up to every 30 minutes as needed during the first 24 hours after presentation, as long as no more than 1.5 to 2 mL total (an expected 24-hour supply) is dispensed and any remainder is discarded after 24 hours. Importantly, although published findings suggest absent harm for short courses, more rigorous studies with a greater cumulative sample size and ophthalmologic follow-up are needed.

Nationwide Aquatic Envenomations Reported to US Poison Control Centers from 2011 to 2020

INTRODUCTION

Aquatic envenomations are common injuries along the coastal United States that pose a public health risk and can cause significant morbidity. We examined aquatic envenomation exposures that were called in to poison control centers (PCC) in the United States from 2011 to 2020.

METHODS

The Association of Poison Control Center's (AAPCC) National Poison Data System was queried for all aquatic envenomations reported during the 10 y period from January 1, 2011, to December 31, 2020. Data collected included date, exposure and geographic location, patient age and sex, signs and symptoms, management setting, treatments, and clinical outcome. Duplicated records, confirmed nonexposure, and reports not originating within the United States were excluded.

RESULTS

There were 8517 human aquatic envenomations reported during the study period, 62% (5243) of whom were male; 56% (4264) of patients were 30 y or younger. There were an average of 852 calls per year, with 46% of calls occurring during June to August. California, Texas, and Florida had the highest number of envenomations during the study period. Fish (61%; 5159) and Cnidaria (30%; 2519) envenomations were the most common exposures. Overall, 37% (3151) of exposures were treated in healthcare facilities, with no deaths reported.

CONCLUSIONS

The highest proportion of aquatic envenomations occurred among younger males (≤30 y) during the summer months. While rarely leading to major adverse events, aquatic envenomations were commonly reported injuries to PCC and occurred in all 50 states. Poison control centers continue to be real-time sources of information and data regarding aquatic envenomation trends.

ICU Admission Risk Factors for Latinx COVID-19 Patients at a U.S.-Mexico Border Hospital

OBJECTIVE

Few studies have examined the impact of coronavirus disease 2019 (COVID-19) on the primarily Latinx community along the U.S.-Mexico border. This study explores the socioeconomic impacts which contribute to strong predictors of severe COVID-19 complications such as intensive care unit (ICU) hospitalization in a primarily Latinx/Hispanic U.S.-Mexico border hospital.

METHODS

A retrospective, observational study of 156 patients (≥ 18 years) Latinx/Hispanic patients who were admitted for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at a U.S.-Mexico border hospital from April 10, 2020, to May 30, 2020. Descriptive statistics of sex, age, body mass index (BMI), and comorbidities (coronary artery disease, hypertension, diabetes, cancer/lymphoma, current use of immunosuppressive drug therapy, chronic kidney disease/dialysis, or chronic respiratory disease). Multivariate regression models were produced from the most significant variables and factors for ICU admission.

RESULTS

Of the 156 hospitalized Latinx patients, 63.5% were male, 84.6% had respiratory failure, and 45% were admitted to the ICU. The average age was 67.2 (± 12.2). Those with body mass index (BMI) ≥ 25 had a higher frequency of ICU admission. Males had a 4.4 (95% CI 1.58, 12.308) odds of ICU admission (p = 0.0047). Those who developed acute kidney injury (AKI) and BMI 25-29.9 were strong predictors of ICU admission (p < 0.001 and p = 0.0020, respectively). Those with at least one reported comorbidity had 1.98 increased odds (95% CI 1.313, 2.99) of an ICU admission.

CONCLUSION

Findings show that age, AKI, and male sex were the strongest predictors of COVID-19 ICU admissions in the primarily Latinx population at the U.S.-Mexico border. These predictors are also likely driven by socioeconomic inequalities which are most apparent in border hospitals.

Ramipril for the Treatment of COVID-19: RAMIC, a Randomized, Double-Blind, Placebo-Controlled Clinical Trial

INTRODUCTION

Retrospective studies report that angiotensin-converting enzyme inhibitors (ACEIs) may reduce the severity of COVID-19, but prospective data on de novo treatment with ACEIs are limited. The RAMIC trial was a randomized, multicenter, placebo-controlled, double-blind, allocation-concealed clinical trial to examine the efficacy of de novo ramipril versus placebo for the treatment of COVID-19.

METHODS

Eligible participants were aged 18 years and older with a confirmed diagnosis of SARS-CoV-2 infection, recruited from urgent care clinics, emergency departments, and hospital inpatient wards at eight sites in the USA. Participants were randomly assigned to daily ramipril 2.5 mg or placebo orally in a 2:1 ratio, using permuted block randomization. Analyses were conducted on an intention-to-treat basis. The primary outcome was a composite of mortality, intensive care unit (ICU) admission, or invasive mechanical ventilation by day 14.

RESULTS

Between 27 May 2020 and 19 April 2021, a total of 114 participants (51% female) were randomized to ramipril (n = 79) or placebo (n = 35). The overall mean (± SD) age and BMI were 45 (± 15) years and 33 (± 8) kg/m2. Two participants in the ramipril group required ICU admission and one died, compared with none in the placebo group. There were no significant differences between ramipril and placebo in the primary endpoint (ICU admission, mechanical ventilation, or death) (3% versus 0%, p = 1.00) or adverse events (27% versus 29%, p = 0.82). The study was terminated early because of a low event rate and subsequent Emergency Use Authorization of therapies for COVID-19.

CONCLUSION

De novo ramipril was not different compared with placebo in improving or worsening clinical outcomes from COVID-19 but appeared safe in non-critically ill patients with COVID-19.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04366050.

Weaning from mechanical ventilation in intensive care units across 50 countries (WEAN SAFE): a multicentre, prospective, observational cohort study

BACKGROUND

Current management practices and outcomes in weaning from invasive mechanical ventilation are poorly understood. We aimed to describe the epidemiology, management, timings, risk for failure, and outcomes of weaning in patients requiring at least 2 days of invasive mechanical ventilation.

METHODS

WEAN SAFE was an international, multicentre, prospective, observational cohort study done in 481 intensive care units in 50 countries. Eligible participants were older than 16 years, admitted to a participating intensive care unit, and receiving mechanical ventilation for 2 calendar days or longer. We defined weaning initiation as the first attempt to separate a patient from the ventilator, successful weaning as no reintubation or death within 7 days of extubation, and weaning eligibility criteria based on positive end-expiratory pressure, fractional concentration of oxygen in inspired air, and vasopressors. The primary outcome was the proportion of patients successfully weaned at 90 days. Key secondary outcomes included weaning duration, timing of weaning events, factors associated with weaning delay and weaning failure, and hospital outcomes. This study is registered with ClinicalTrials.gov, NCT03255109.

FINDINGS

Between Oct 4, 2017, and June 25, 2018, 10 232 patients were screened for eligibility, of whom 5869 were enrolled. 4523 (77·1%) patients underwent at least one separation attempt and 3817 (65·0%) patients were successfully weaned from ventilation at day 90. 237 (4·0%) patients were transferred before any separation attempt, 153 (2·6%) were transferred after at least one separation attempt and not successfully weaned, and 1662 (28·3%) died while invasively ventilated. The median time from fulfilling weaning eligibility criteria to first separation attempt was 1 day (IQR 0-4), and 1013 (22·4%) patients had a delay in initiating first separation of 5 or more days. Of the 4523 (77·1%) patients with separation attempts, 2927 (64·7%) had a short wean (≤1 day), 457 (10·1%) had intermediate weaning (2-6 days), 433 (9·6%) required prolonged weaning (≥7 days), and 706 (15·6%) had weaning failure. Higher sedation scores were independently associated with delayed initiation of weaning. Delayed initiation of weaning and higher sedation scores were independently associated with weaning failure. 1742 (31·8%) of 5479 patients died in the intensive care unit and 2095 (38·3%) of 5465 patients died in hospital.

INTERPRETATION

In critically ill patients receiving at least 2 days of invasive mechanical ventilation, only 65% were weaned at 90 days. A better understanding of factors that delay the weaning process, such as delays in weaning initiation or excessive sedation levels, might improve weaning success rates.

FUNDING

European Society of Intensive Care Medicine, European Respiratory Society.

Corporate Control of Emergency Departments: Dangers from the Growing Monster

BACKGROUND

Corporate control in emergency departments (EDs) has increased during the past 20 years through hospital consolidation and the growth of ED contract management groups.

OBJECTIVES

To describe the growing corporate influence in the practice of emergency medicine and associated dangers to the public's safety and well-being.

DISCUSSION

Hospital systems through mergers and acquisitions have created regional monopolies providing them the power to charge high fees, which can lead to economic hardship for patients. Hospitals have also increasingly employed physicians and can exert influence over their practice to further increase profits. ED contract management groups (CMGs) obtain the exclusive contract for emergency services and gain control over the livelihood of emergency physicians, decreasing their autonomy and inserting the business interest into the physician-patient relationship, and this may result in harm to patients. Safety issues identified by emergency physicians may not be articulated for fear of being fired, and protocols may direct physicians to order unneeded testing and encourage unnecessary hospital admissions to make higher profits. Of additional concern, some CMGs are involved in graduate emergency medicine education, exposing physicians in training to corporate influence during their formative years.

CONCLUSIONS

Given the potential harm to patients due to corporate influence, there must be serious consideration for legislative or regulatory solutions regarding the increasing corporate control of emergency medicine in the United States.

Bamlanivimab Reduces ED Returns and Hospitalizations and May Reduce COVID-19 Burden on Low-resource Border Hospitals

Introduction

To evaluate the effectiveness of bamlanivimab at reducing return emergency department (ED) visits in primarily Latinx/Hispanic patients with mild or moderate coronavirus disease 2019 (COVID-19). Secondary aims were to evaluate the prevention of subsequent hospitalizations and deaths in a resource-limited United States (U.S.)-Mexico border hospital.

Methods

We conducted a retrospective, open-label interventional study on 270 eligible adult patients diagnosed with mild-moderate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who met criteria for receiving bamlanivimab from November 1, 2020 to January 31, 2021. The main outcomes of 14-day return visits to the ED and hospitalizations due to COVID-19 were compared between two groups – those who received bamlanivimab (exposed group) and those who did not receive bamlanivimab (unexposed group). Outcomes were analyzed through chi-square tests followed by multivariate regression modeling to adjust for patient demographics, characteristics, and comorbidities.

Results

There were 136 COVID-19 patients who received bamlanivimab in the ED prior to discharge and an unexposed group of 134 COVID-19 patients who were evaluated and discharged from the ED without receiving bamlanivimab. Overall, mean age was 61.7 (S.D. +/−13.9) years, mean body mass index (BMI) 31.0 (S.D. +/−6.6) kg/m², 91.5% identified as Latinx/Hispanic, 51.9% male, and 80.7% reported at least one comorbidity. Most commonly reported comorbidities were obesity (22.6%), hypertension (59.6%), and diabetes (41.1%). The bamlanivimab group had a 22.8% (mean estimate = 0.7717, 95% CI [0.6482, 0.8611]) risk reduction or 84.4% (0.3030, 95% CI = 0.166, 0.554, p=.0001) absolute reduction of ED return visits within 14 days compared to controls after adjusting for chronic kidney disease. The bamlanivimab group had 19.0% (mean estimate=0.8097, 95% CI [0.6451, 0.9087]) risk reduction or 96.2% (0.235, 95% CI 0.100, 0.550, p=0.0008) absolute reduction of subsequent hospitalizations compared to unexposed patients after adjusting for diabetes status.

Conclusion

Bamlanivimab infusions for high-risk COVID-19 patients in the ED substantially reduced the risk of return visits to the ED and hospitalizations in our primarily Latinx/Hispanic population. Monoclonal antibody infusions may help reduce hospital utilization during COVID-19 surges at U.S.-Mexico border hospitals.

Buprenorphine for High-dose Tramadol Dependence: A Case Report of Successful Outpatient Treatment

Introduction

During the coronavirus disease 2019 pandemic caused by the severe acute respiratory syndrome coronavirus 2, deaths from opiate drug overdoses reached their highest recorded annual levels in 2020. Medication-assisted treatment for opiate use disorder has demonstrated efficacy in reducing opiate overdoses and all-cause mortality and improving multiple other patient-centered outcomes. Treatment of tramadol dependence in particular poses unique challenges due to its combined action as opioid agonist and serotonin-norepinephrine reuptake inhibitor. Tramadol puts patients with dependence at risk for atypical withdrawal syndromes when attempting to reduce use. Little evidence is available to guide treatment of tramadol dependence.

Case Report

We present a case of high-dose tramadol addiction that began with misuse of medically prescribed tramadol for treatment of musculoskeletal back pain. The patient’s use reached oral consumption of 5000–6000 milligrams of illicit tramadol daily. She complained of common complications of tramadol use disorder including memory impairment, excessive sedation, and tramadol-induced seizures. The patient was referred to the emergency department in a withdrawal crisis seeking treatment where she was successfully managed with buprenorphine and phenobarbital and then linked to ongoing outpatient treatment.

Conclusion

Our report adds to the limited guidance currently available on the acute management of tramadol withdrawal and treatment of tramadol use disorder. Our case suggests the initiation of high-dose buprenorphine may be an effective and feasible option for emergency clinicians.

Case Report of Thrombosis of the Distal Aorta with Occlusion of Iliac Arteries in COVID-19 Infection

INTRODUCTION

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the coronavirus disease of 2019 (COVID-19) pandemic, has been associated with a variety of prothrombotic sequelae. The pathogenesis of this hypercoagulability has not yet been fully elucidated, but it is thought to be multifactorial with overactivation of the complement pathways playing a central role. There is emerging evidence that the resulting complications are not confined to the venous circulation, and even in patients without typical respiratory symptoms or traditional risk factors, there is a significant rate of arterial thromboembolic disease in patients with SARS-CoV-2 infection.

CASE REPORT

We describe a patient presenting with bilateral leg pain without any respiratory symptoms or fever who ultimately was found to be COVID-19 positive and had thromboembolism of the aorta and bilateral iliac occlusion. This report reviews available evidence on the prevalence of arterial thromboembolism in COVID-19 patients and some proposed mechanisms of the pathophysiology of COVID-19-associated coagulopathy.

CONCLUSION

It is important that the emergency physician maintain a high degree of suspicion for arterial thromboembolic disease in patients who are infected with COVID-19 even in the absence of typical respiratory symptoms. Additionally, COVID-19 should be considered in patients with unexplained thromboembolic disease, as this may increase the detection of COVID-19.

[Polycystic ovary syndrome: what are the obstetrical risks?]

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age and the leading cause of female infertility. This condition is frequently associated with significant metabolic disorders, including obesity and hyperinsulinemia. Therefore, it seems essential to focus on the pregnancy of these patients and possible obstetric complications. Many studies suggest an increase in the risk of obstetric pathology: early miscarriage, gestational hypertension, preeclampsia, gestational diabetes mellitus diagnosed during early pregnancy, prematurity, low birthweight or macrosomia, neonatal complications and cesarean sections. However, it is difficult to conclude clearly about it, because of the heterogeneity of definition of PCOS in different studies. In addition, many confounding factors inherent in PCOS including obesity are not always taken into account and generate a problem of interpretation. However it seems possible to conclude that PCOS does not increase the risk of placental abruption, HELLP syndrome, liver disease, postpartum hemorrhage, late miscarriage and stillbirth.

Is apoptosis a regulatory mechanism during early canine pregnancy?

Fas is a membrane-bound protein which upon activation causes programmed cell death. Fas ligand (FasL) binds Fas on target cells. Both these factors are known to regulate apoptosis at implantation in different species and thus might be involved in the regulation of implantation in dogs. The aim of the study was to assess the expression of Fas and FasL in canine uterine tissue throughout pregnancy as well as in pre-implantation embryos using RT-PCR and RT-qPCR. Uterine tissues was collected from of 21 healthy pregnant bitches (group I: days 10-12, n = 5; group II: days 18-25, n = 6; group III: days 28-45, n = 6) and from 4 non-pregnant bitches (controls: days 10-12). Pregnancy stage was determined by days after mating, that is, 2-3 days after ovulation as determined by vaginal cytology and progesterone measurement. After ovariohysterectomy, uteri from group I bitches were flushed with PBS and the embryos washed and stored frozen at -80°. Tissues from the other groups were taken from the implantation and placentation sites, respectively, covered with Tissue Tek(®) and frozen at -80°. Extraction of RNA was performed with Trizol Reagent and RT-qPCR using SYBR green probes. In pre-implantation embryos, only FasL but not Fas could be detected. In all tissues from pregnant and non-pregnant bitches, both parameters were detectable. Before implantation (group I) expression of FasL resembled that of non-pregnant bitches in early dioestrus and decreased significantly during implantation and thereafter (p < 0.05). Expression of Fas did not change significantly until day 45. The relative expression of Fas exceeded that of FasL at each stage investigated, which is comparable to observations of other species; however, high standard deviations indicate high individual differences. These preliminary results point towards a regulatory function of the Fas/FasL system during early canine pregnancy.

Evidence-based treatment of jellyfish stings in North America and Hawaii

We performed a systematic review of the evidence supporting various treatments for envenomation by jellyfish (cnidarian) and related organisms in North America and Hawaii. Our review produced 19 pertinent primary articles. Current research demonstrates variable response to treatment, often with conflicting results according to species studied, which contributes to considerable confusion about what treatment is warranted and efficacious. Our review suggests that vinegar causes pain exacerbation or nematocyst discharge in the majority of species. Hot water and topical lidocaine appear more widely beneficial in improving pain symptoms and are preferentially recommended. Unfortunately, they may be difficult to obtain at the site of envenomation, such as the beach or diving sites. In these instances, removing the nematocysts and washing the area with saltwater may be considered. If the envenomation is thought to be due to the bluebottle (Physalia), vinegar may be beneficial.

Retrospective review of digoxin exposures to a poison control system following recall of Digitek® tablets

BACKGROUND

In April 2008, Digitek® digoxin tablets were recalled by the manufacturer as possibly containing double the labeled amount of drug. The recall to March 2006 involved 800 million tablets.

OBJECTIVE

The aim of this study was to evaluate whether there was any increase in the number of calls to a poison control system, and any increase in the severity of exposures after the recall compared with before the recall.

METHODS

A retrospective review of all digoxin exposures to a poison control system from March 2004 to February 2008 was conducted, with data extracted from an electronic database (California Poison Control System). Total numbers of exposures were identified. Cases with moderate, major, and death outcomes were also identified and tallied. Chi-squared analysis was performed.

RESULTS

Prior to the recall, there were 679 digoxin exposures. 148 (22%) were listed with moderate, major, or death as outcome. After the recall, there were a total of 610 cases, 165 (27%) with moderate, severe, or death as outcome. There was a statistically significant increase in the total number of moderate, major, and death outcomes after the period of the manufacturing error compared with before (p = 0.028).

CONCLUSION

During the period of manufacturing error, there was a statistically significant increase in digoxin exposures with moderate, major, or death outcomes. The recall of Digitek® tablets may have increased moderate, major, or death outcomes from digoxin exposures in a poison control system database.

A retrospective evaluation of shortened-duration oral N-acetylcysteine for the treatment of acetaminophen poisoning

INTRODUCTION

The use of less than the traditional 72-hour course of oral N-acetylcysteine has been an alternative treatment option following potentially toxic acute and chronic acetaminophen ingestions felt to be at low risk of developing hepatotoxicity. While clinical experience with shortened treatment duration is extensive, there are few studies evaluating the effectiveness and extent to which these regimens may be used.

METHODS

A large statewide poison center database was reviewed for all acetaminophen exposures involving potentially toxic acute and chronic ingestions, in addition to those taking place at unknown times. Patients were identified who met laboratory criteria for early N-acetylcysteine (NAC) discontinuation (APAP>10 micro/mL, INR<or=1.3, and AST/ALT<or=60 IU) after a minimum of a 140-mg/kg oral NAC loading dose and 5 additional 70-mg/kg doses over 20 hours. A further search of the poison center database was conducted for individuals who received shortened-course (20-48 hours) oral NAC treatment who developed subsequent hepatotoxicity or death.

RESULTS

Of 3303 individuals with potentially toxic acetaminophen ingestions, 1932 met criteria for early NAC discontinuation. Mean treatment duration was 36.4+/-7.7 hours (acute=37.3+/-7.6 hours; chronic=34.8+/-7.4 hours; unknown=35.2+/-7.6 hours). The poison center database search identified no short-course eligible subjects who developed subsequent hepatotoxicity or death following<or=48 hours of oral NAC.

CONCLUSION

Treatment with shortened-course oral NAC in patients meeting criteria for early discontinuation may be an effective treatment option in a sizeable proportion of individuals with potentially toxic acetaminophen ingestions.

Optic nerve sheath diameter does not change with patient position

OBJECTIVES

Optic nerve sheath diameter (ONSD) has been proposed as a marker for increased intracranial pressure. Trendelenburg's position is often used in hypotensive patients and reverse Trendelenburg's position (30 degrees head up) is often used in head injury patients. We asked if there would be any change in OSND in healthy human adults between the supine, Trendelenburg's, and reverse Trendelenburg's positions.

METHODS

Prospective case-control blinded study using consenting healthy adults. Three separate investigators measured the ONSD in each eye of 10 separate volunteers in the supine, Trendelenburg's, and reverse Trendelenburg's positions with 30 degrees angulation from the horizontal. Data were analyzed using the paired t test.

RESULTS

In the supine position, the mean ONSD was 4.6 +/- 0.71 (SD) mm in the right eye and 4.5 +/- 0.56 (SD) mm in the left eye. In Trendelenburg's position, the mean ONSD was 4.4 +/- 0.72 (SD) mm in the right eye and 4.7 +/- 0.53 (SD) mm in the left eye. In reverse Trendelenburg's position, the mean ONSD was 4.4 +/- 0.49 (SD) mm in the right eye and 4.8 +/- 0.76 (SD) mm in the left eye. There was no significant difference in OSND between positions for either eye by analysis of variance. Interobserver agreement was +/-1 mm in at least 90% of the subjects regardless of position.

CONCLUSION

Optic nerve sheath diameter measurement by ultrasound does not significantly change with Trendelenburg's or reverse Trendelenburg's position in comparison with the supine position in healthy individuals.

Evaluation of a rapid bedside toxicology screen in patients suspected of drug toxicity

Although rapid bedside toxicological screening is reliable, it has not been validated in the emergency department (ED) setting. We assessed the accuracy of a 10-min bedside immunoassay, Triage Panel (TP), for 7 drugs of abuse and tricyclic antidepressants (TCA) in ED patients suspected of drug toxicity. This was a prospective observational study conducted at an urban teaching ED (100,000 visits/year) of patients suspected of drug toxicity during a 7-month period. The assay was compared for agreement with combined SYVA EMIT and TLC. GC/MS or HPLC was used for analyzing sensitivity and specificity in discordant findings. A total of 172 cases (ages 0.6-73 years) were screened with TP, and 100 (58%) were found to be positive for at least one drug. Sensitivity (proportion and 95% CI) was as follows: cocaine 30/31 (90.6-100%), phencyclidine no cases, THC 21/24 (80.1-94.3), opiates 14/14 (100), amphetamines 1/1 (NA), barbiturates 10/10 (100), benzodiazepines 20/21 (90.5-99.9), and TCA 13/13 (100). Specificity was above 98% for every drug except TCAs (which was 95%), partly due to interference from iminostilbene (a carbamazepine metabolite) in three cases. Agreement between TP and hospital laboratory was over 90% for every drug class. Both benzodiazepines and THC showed significant disagreement between the two testing modalities. In conclusion, in a series of ED patients suspected of drug toxicity, the TP was an accurate tool to rule out the presence of seven drugs of abuse and TCAs. Further testing will be required to verify the efficacy of the test in populations with a higher prevalence of phencyclidine and amphetamine abuse.

Formate kinetics in methanol poisoning

OBJECTIVE

We sought to describe the kinetics, dialysis clearance, and laboratory markers of formate (FA), the toxic metabolite of methanol (meOH).

METHODS

Data were obtained from a prospective, multicenter study of fomepizole +/- dialysis for methanol poisoning. Inclusion criteria confirmed methanol exposure or suspicion of exposure plus either acidemia or abnormal osmolar gap. Dialysis indications were [meOH] > 50 mg/dL, pH < 7.1, refractory acidosis, or visual toxicity. Serial plasma formate, methanol, pH, and electrolyte measurements were made. Formate was determined by gas chromatography. Endogenous and dialysis elimination half-lives were calculated as t(1/2) = 0.693/Ke, with Ke (elimination constant) derived from the slope of log (FA) vs. time. Half-lives were compared with an unpaired Student's t-test. Dialysis clearance was calculated using the Fick Principle. Pearson correlation analysis compared initial formate with initial pH, serum bicarbonate, and anion gap.

RESULTS

Eleven patients were treated in the study. Eight had detectable formate with mean [FA] of 15.1 mmol/L (range 0.5-34.8). Endogenous elimination half-life was 205 +/- 90 minutes. Elimination half-life during dialysis (n = 5) was 150 +/- 37 minutes, which was not different (t = 0.22; NS). The overall dialysis formate clearance rate was 223 +/- 25 mL/min. Correlation coefficients were: pH vs. formate r2 = 0.93; bicarbonate vs. formate r2 = 0.81; and anion gap vs. formate r2 = 0.76 (all p < 0.05).

CONCLUSIONS

Although dialysis clears formate, it did not significantly enhance endogenous elimination in our series of patients. Low pH, low bicarbonate, and elevated anion gap correlate independently with formate presence.

Hyperbaric oxygen does not prevent neurologic sequelae after carbon monoxide poisoning

Delayed neurologic sequelae occur in up to 40% of severe carbon monoxide (CO) poisonings. Conflicting clinical data support the efficacy of hyperbaric oxygen (HBO) therapy in the acute treatment of CO poisoning.

OBJECTIVE

To determine whether oxygen therapy reduces neurologic sequelae after CO poisoning in mice.

METHODS

Male Swiss-Webster mice were exposed to CO at 1,000 ppm for 40 minutes and then 50,000 ppm until loss of consciousness (LOC) (4-9 additional minutes). Total time of both phases of CO exposure was 40-49 minutes. Treatment included HBO with 3 atmospheres (ATA) 100% oxygen, normobaric oxygen (NBO) with 1 ATA 100% oxygen, or ambient air 15 minutes after LOC. All animals underwent passive avoidance training and memory was assessed by measuring step-down latency (SDL) and step-up latency (SUL) seven days following CO exposure.

RESULTS

Carbon monoxide poisoning induced significant memory deficits (SDL(CO) = 156 sec; SUL(CO) = 75%) compared with nonpoisoned (NP) animals (SDL(NP) = 272 sec; SUL(NP) = 100%). Both HBO and NBO did not prevent these neurologic sequelae. Furthermore, no significant neurobehavioral differences were found between HBO and NBO. Histologic examination of the CA1 layer of the hippocampus for pyknotic cells showed significant damage from CO in the air-treated animals (9.6%) but not in the nonpoisoned animals (3.8%). No significant neuroprotection was seen histologically with NBO and HBO compared with ambient air.

CONCLUSIONS

These results suggest that HBO is not effective in preventing neurologic sequelae in mice and that there is no benefit of HBO over NBO following severe CO neurotoxicity.

Airway obstruction following canebrake rattlesnake envenomation

We report an unusual case of canebrake rattlesnake (Crotalus horridus atricaudatus) envenomation whose major manifestation was orolingual edema and airway compromise. The likely source of swelling was mucosal absorption of venom following the first aid technique of cutting and sucking the bite site. Except for airway compromise, the patient had mild local bite site effects (swelling) and mild systemic findings (depressed fibrinogen and elevated creatinine phosphokinase). He was managed with fiberoptic nasotracheal intubation and Crotalid antivenin with good outcome.

Incidence of aspiration pneumonia in intubated patients receiving activated charcoal

Several case reports and animal studies raise concerns over the risk of aspiration pneumonia when administering activated charcoal (AC) to intubated patients. Therefore, we sought to determine the incidence of aspiration pneumonia in intubated overdose patients who then received AC. We conducted a retrospective review from January 1994 to April 1997 of intubated patients who then received AC. Patients were transferred to, or primarily treated at, an 843-bed tertiary medical center with an annual emergency department volume of 100,000 patients. Objective evidence of infiltrate on chest radiograph during initial 48 h of hospitalization was used to determine the incidence of aspiration pneumonia. Patients with known preexisting pneumonia or with administration of AC before intubation were excluded. There were 64 patients identified. Fourteen were excluded for clinical aspiration before intubation, receiving activated charcoal before intubation, or abnormal immediate post-intubation chest radiographs. The remaining 50 patients, ages 1-64 years, 33% male, overdosing on a large variety of substances, required acute intubation and then received AC. Only two patients of these 50 (4%) with initial negative radiographs developed a new infiltrate after intubation and AC. Administration of AC to intubated overdose patients is associated with a low incidence of aspiration pneumonia.

Carbon monoxide poisoning. Early awareness and intervention can save lives

Each year, particularly during the heating season, thousands of people are poisoned by carbon monoxide, with potentially devastating outcomes. Initial diagnosis can be difficult because symptoms closely resemble those of influenza and are often misinterpreted. Dr Tomaszewski discusses diagnosis and treatment, including the benefits and risks of hyperbaric oxygen therapy.

The effect of hypertonic sodium and dantrolene on propranolol cardiotoxicity

OBJECTIVE

To evaluate whether measures that lower cytosolic calcium (Ca) can reverse propranolol (PROP) toxicity in the isolated, perfused rat heart.

METHODS

Isolated rat hearts were perfused on a Langendorff apparatus with Krebs-Henseleit-bicarbonate (KHB) buffer solution. Toxicity was produced by perfusing the hearts with PROP (5 micrograms/mL) for 30 minutes. Subsequently, the hearts were treated for 30 minutes with buffer containing PROP plus experimental treatment. Three treatments were chosen: hypertonic sodium (Na) (160 mmol), to stimulate Na-Ca exchange, dantrolene (DAN) (10 mumol), to inhibit Ca release from sarcoplasmic reticulum, and combined hypertonic Na and DAN. The hearts were paced after 20 minutes of treatment. Heart rate (HR), left ventricular peak systolic pressure (LVP), the first derivative of LVP (dP/dt), and coronary flow were measured.

RESULTS

PROP decreased HR and rendered the hearts refractory to pacing. PROP did not alter dP/dt. PROP increased LVP consistent with increased cytosolic Ca. Combined hypertonic Na and DAN treatment restored the ability to pace PROP-toxic hearts to the basal HR. Individually, hypertonic Na or DAN treatment partially restored the ability to pace toxic hearts. As experimental treatments increased HR, dP/dt and LVP decreased, consistent with decreased cytosolic Ca availability.

CONCLUSION

These data are consistent with the hypothesis that bradycardia during beta-blocker cardiotoxicity is mediated by altered Ca homeostasis.

Insulin improves survival in a canine model of acute beta-blocker toxicity

STUDY OBJECTIVE

To compare the efficacy of a novel antidote, insulin, with standard treatments, glucagon and epinephrine, in a canine model of acute beta-blocker toxicity.

METHODS

Anesthetized dogs were fitted with instruments by means of thoracotomy and vascular cutdown for multiple cardiodynamic, hemodynamic, metabolic, and electrical measures. After basal measurements were taken, animals received intravenous propranolol (.25 mg/kg/minute) continuously for the remainder of the experiment. Toxicity was defined as a 25% decrease in the product of heart rate times mean blood pressure. Thirty minutes after the development of toxicity, toxic measures were taken (treatment 0 minutes), and then the animals (n = 6 each group) received either sham (saline solution), insulin (4 IU/minute with glucose clamped), glucagon (50 micrograms/kg bolus, then 150 micrograms/kg/hour infusion), or epinephrine (1 microgram/kg/minute). Animals were monitored until death or for 240 minutes.

RESULTS

Propranolol decreased contractility, left ventricular pressure, and systemic blood pressure, and resulted in death of all sham-treated animals by 150 minutes. Six of six insulin-treated, four of six glucagon-treated, and one of six epinephrine-treated animals survived. Survival was greater for insulin-treated animals, compared with either glucagon-treated (P < .05) or epinephrine-treated animals (P < .02) by the log-rank test. Insulin-treated animals were characterized by improved cardiodynamics and hemodynamics, increased myocardial glucose uptake, and decreased serum potassium.

CONCLUSION

Insulin is a superior antidote compared with glucagon or epinephrine in an anesthetized canine model of acute beta-blocker toxicity.

Spontaneous hemoperitoneum from brodifacoum overdose

Brodifacoum is a 4-hydroxycoumarin derivative that is commonly used as a rodenticide. Human exposures have produced severe coagulopathies resulting in hematuria, gastrointestinal bleeding, intracranial hemorrhage, and death. This is the first report of spontaneous hemoperitoneum secondary to brodifacoum ingestion. The patient was successfully managed with fresh frozen plasma, packed red blood cells, and vitamin K1. No surgical intervention was performed. The patient required ongoing daily vitamin K1 therapy for longer than 6 months.

Prophylaxis against middle ear barotrauma in US hyperbaric oxygen therapy centers

The most common complication of hyperbaric oxygen (HBO) treatment is middle ear barotrauma, which can lead to permanent hearing loss and vertigo. Unconscious patients and infants present a special diagnostic challenge because of difficulties in communicating pain and equalizing pressure across the ears. This study involved a phone survey to all hospital-based HBO centers in the United States concerning routine practice for middle ear barotrauma prophylaxis. Results indicate that more than a fifth of centers always do routine prophylactic myringotomies on intubated patients (30 of 126) and infants (19 of 86). Less than half of centers never performed the procedure as routine prophylaxis. A third of centers (49 of 145) routinely administered prophylactic drugs before HBO treatment. Topical nasal decongestants, particularly oxymetazoline, were preferred to systemic oral medications (chi2 = 20.8, P<.001). These results show that there is great variance in clinical practice with regard to middle ear barotrauma prophylaxis among US HB0 centers. Many centers are using unproven therapies such as topical nasal decongestants.

The effects of extracellular ions on beta-blocker cardiotoxicity

The mechanism of beta-blocker induced cardiotoxicity is poorly understood. One possible explanation is that beta-blockers induce ion dyshomeostasis, resulting in cardiac hyperpolarization. The intent of this study was to determine if modifying extracellular ions would reverse cardiotoxicity from two beta-blockers: propranolol (PROP) and atenolol (ATEN). Two treatments were studied: low extracellular K+ and high extracellular Na+. Isolated rat hearts were perfused on a Langendorff apparatus with Krebs-Henseleit- Bicarbonate buffer (KHB) solution. Toxicity (Tox) was induced by perfusing hearts for 30 min with KHB + PROP [5 microgram/ml] or KHB + ATEN [2.5 mg/ml]. Subsequently, hearts were perfused with KHB containing either PROP or ATEN, but modified by lowering K+ [2.3 mM] or raising Na+ [160 mM] for a 30-min treatment (Tx) period. Hearts were paced near the end of treatment. Cardiodynamics were monitored via a balloon-tipped catheter in the left ventricle. The first derivative of LV pressure (dP/dt) with respect to time served as our index of myocardial performance. Tx groups were as follows: (1) KHB only, (2) PROP only, (3) PROP + K, (4) PROP + Na, (5) ATEN only, (6) ATEN 4 K, and (7) ATEN + Na. PROP induced negative chronotropic effects and rendered the hearts refractory to pacing. ATEN demonstrated similar chronotropic toxicity plus decreased myocardial contractility. Tx with low extracellular K+ and high extracellular Na+ increased HR and restored the ability to pace, thereby reversing toxicity. These data suggest that beta-blocker toxicity is mediated via hyperpolarization.

Urine toxicology screens in drivers suspected of driving while impaired from drugs

OBJECTIVE

Police departments, in conjunction with the National Highway Traffic Safety Administration, have developed a standardized evaluation aimed at identifying drivers impaired by drugs other than ethanol. These evaluations are performed by specially trained police officers known as Drug Recognition Experts.

METHODS

We retrospectively reviewed the evaluations of 242 drivers detained for driving while impaired in the City and County of Denver from January 1, 1988 to June 30, 1990.

RESULTS

All drivers had urine toxicology screens performed, which were positive for a mean 1.2 +/- 0.9 SD (range zero to four) for drugs having the potential for causing driving impairment. The 193/242 urine screens (79.8%) testing positive showed the following drugs: cannabis 162 (66.9%), stimulants (including cocaine metabolites) 80 (33.1%), depressants (benzodiazepines and barbiturates) 24 (9.9%), narcotics 12 (5.0%), inhalants (toluene) 1 (0.4%), hallucinogens (LSD) 1 (0.4%), and other 3 (1.2%). Drug Recognition Experts, based on their initial evaluation, were able to predict correctly some or all of the drugs found on the urine screens in 178/242 (73.6%) of cases. Overall agreement between the Drug Recognition Experts opinions and urine screen results had a kappa value (p < 0.05) of 0.41.

CONCLUSIONS

There was a high rate (79.8%) of positive urine toxicology screens in drivers suspected of nonethanol drug impairment. In most cases, Drug Recognition Experts were able to reliably predict the results of these screens.

Effect of acute ethanol ingestion on orthostatic vital signs

STUDY OBJECTIVE

To determine the effect of acute ethanol intoxication on the results of orthostatic tilt testing.

DESIGN

Prospective, randomized crossover study. Subjects received ethanol (1.1 gm/kg) or an equal volume of water added to nonalcoholic beer. Orthostatic vital signs, ethanol concentration, and relative volume status were checked initially and hourly for 8 hours.

PARTICIPANTS

Twenty healthy human volunteers, 10 men, and 10 women.

RESULTS

Peak ethanol concentration was 116 +/- 18 mg/dL (mean +/- SD) 1 hour after ingestion. ANOVA for repeated measures revealed a significant difference in orthostatic pulse change and relative volume deficit between the ethanol and placebo groups (P < .05). Post hoc testing revealed significant differences between the two groups at two, five, seven and eight hours post ingestion for pulse change, and two to eight hours for volume status (Bonferroni's corrected t test, P < .0055). At 2 and 5 to 8 hours, there were significantly more positive tilt tests (+/- 30 beat/minute increase) in the ethanol group than in the placebo group (P < .05). Starting at 2 hours, the ethanol group had a statistically significant relative fluid deficit averaging .5 L by 3 hours. There was no difference in postural blood pressure changes between the two groups.

CONCLUSION

In healthy volunteers, ethanol intoxication resulted in exaggerated postural pulse changes and in a greater proportion of positive orthostatic tilt test results than in a placebo group. These changes were accompanied by significant relative fluid deficits.

Methamphetamine toxicity prevented by activated charcoal in a mouse model

STUDY OBJECTIVE

To determine the effectiveness of activated charcoal in preventing toxicity from oral methamphetamine HCI.

DESIGN

Randomized, prospective, nonblinded, controlled animal study.

SETTING

Animal care facility.

PARTICIPANTS

CD-1 male mice.

INTERVENTIONS

Mice were given 100 mg/kg methamphetamine HCI (lethal dose 60) in water by oral gavage. Within 1 minute of methamphetamine administration, mice received either 1 g/kg activated charcoal or an equivalent volume of water as control.

MEASUREMENTS AND MAIN RESULTS

Mice were observed for time to onset of symptoms (piloerection, agitation, and tremor) and mortality at 1, 24, and 48 hours. Activated charcoal delayed onset of symptoms (5.53 +/- 1.25 minutes versus 4.27 +/- 1.22 minutes, P < .002) and decreased mortality compared to controls at 1 hour (1 of 20 versus 10 of 20, P < .003) and 24 hours (five of 20 versus 12 of 20, P < .05). There was no difference between groups in mortality at 48 hours.

CONCLUSION

A single dose of activated charcoal given after oral methamphetamine delayed onset of toxicity and decreased early mortality in mice. There was no effect on overall mortality.