Andrew M. King

Organophosphate and carbamate poisoning.

Organophosphates (OPs) and carbamates have a wide variety of applications, most commonly as pesticides used to eradicate agricultural pests or control populations of disease-carrying vectors. Some OP and carbamates have therapeutic indications such as physostigmine. Certain organophosphorus compounds, known as nerve agents, have been employed in chemical warfare and terrorism incidents. Both classes inhibit acetylcholinesterase (AChE) enzymes, leading to excess acetylcholine accumulation at nerve terminals. In the setting of toxicity from either agent class, clinical syndromes result from excessive nicotinic and muscarinic neurostimulation. The toxic effects from OPs and carbamates differ with respect to reversibility, subacute, and chronic effects. Decontamination, meticulous supportive care, aggressive antimuscarinic therapy, seizure control, and administration of oximes are cornerstones of management.

Comparison of the lowest instrumented, stable, and lower end vertebrae in "single overhang" thoracic adolescent idiopathic scoliosis: anterior versus posterior spinal fusion.

Study Design. A retrospective multicenter study. Objective. To investigate the relationship between the lowest instrumented, stable, and lower end vertebrae in patients with “single overhang” thoracic (main thoracic) curves treated with anterior or posterior spinal fusion. Summary of Background Data. Previous studies have shown “saving” fusion levels with anterior spinal fusion, as opposed to posterior spinal fusion; however, to our knowledge, none of these studies evaluated the relative position to the lower end vertebra to compare study groups accurately. For clarification, “single overhang” includes Lenke 1A and 1B curves. For these thoracic curves, the lumbar curve does not cross the midline. Materials and Methods. A retrospective multicenter study of adolescent idiopathic scoliosis was performed to identify specifically patients with “single overhang” thoracic (Lenke 1A and 1B) curves with more than a 2-year follow-up. To analyze relative fusion levels, the differences were computed as follows: (1) the difference between the vertebra position for the stable vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or (2) the difference between the vertebra position for the lower end vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or Results. A total of 298 “single overhang” thoracic curves (148 Lenke 1A, 150 Lenke 1B) were identified, of which 293 had either an anterior spinal fusion or posterior spinal fusion; 5 patients underwent a combined anterior-posterior spinal fusion. Anterior spinal fusion was performed in 70 patients (23.9%) and posterior spinal fusion in 223 (76.1%). While comparing the lowest instrumented vertebra to the stable vertebra with anterior spinal fusion, the lowest instrumented vertebra was identified either at the level of the stable vertebra or above in 97% of 1A/B curves (P < 0.001). Using posterior spinal fusion techniques, the lowest instrumented vertebra was identified either at the stable vertebra or above in 65% of the 1A/B curves (P < 0.05). Conclusions. These data confirm that anterior spinal fusion techniques result in a mean shorter fusion of 1.5 vertebral segments/patient when compared to posterior spinal fusion techniques with respect to the position of the lowest instrumented and stable vertebrae for “single overhang” thoracic (Lenke 1A/B) curves. However, because this is a retrospective multicenter study over 10 years, it represents various posterior spinal fusion techniques that do not include all pedicle screw constructs.

Prosthetic Hip-Associated Cobalt Toxicity

Prosthetic hip-associated cobalt toxicity (PHACT) is gaining recognition due to the use of metal-on-metal total hip replacements. Identifying true toxicity from merely elevated cobalt levels can be extremely difficult due to the lack of available data. An extensive review of the medical literature was undertaken to characterize cobalt toxicity from prosthetic hips. As an objective approach to making the diagnosis of PHACT, we suggest the following criteria: (1) elevated serum or whole blood cobalt levels due to a prosthetic hip, (2) at least two test-confirmed findings consistent with cobalt toxicity, and (3) exclusion of other etiologies. Adhering to objective diagnostic data for PHACT is a realistic and prudent method by which to eliminate the subjectivity of vague or difficult to identify complaints. These diagnostic criteria are not meant to evaluate prosthetic hardware failure, but as a means to identify systemic cobalt toxicity. Finally, assessment of cobalt toxicity from prosthetic hips should be done in conjunction with a medical toxicologist.

Nonfatal tramadol overdose may cause false-positive phencyclidine on Emit-II assay

False-positive results are a common finding with qualitative urine drug screens. This report describes 2 patients with positive phencyclidine (PCP) screens using the Emit II Plus Drugs-of-Abuse Test (Siemens Healthcare Diagnostics, Inc, Tarrytown, NY) after tramadol ingestion. Our first case was a 43-year-old woman with a history of bipolar disorder who presented to the emergency department(ED) for medical clearance after ingesting an unknown amount of tramadol. Her urine drugs-of-abuse screen was positive for PCP. A comprehensive gas chromatography/mass spectrometry qualitative urine drug screen demonstrated valproic acid metabolites, nicotine, gabapentin, benztropine, and a large peak of tramadol. Our second case was a 3-year-old boy with a medical history of previous ingestions presented to the ED for altered mental status and suspected ingestion. His urine drugs-of-abuse screen was positive for PCP. A comprehensive gas chromatography/mass spectrometry qualitative urine drug screen demonstrated a large peak of tramadol. Molecular similarity analysis can predict cross-reactivity of drug of abuse and therapeutic drug monitoring assays. This computational analysis demonstrated that tramadol and its metabolite possess enough similarity to PCP to produce positives due to interaction with the assay antibody (or antibodies). Tramadol and its metabolites can cause a false-positive Emit II+ PCP screen, and clinicians should use caution when interpreting urine drugs-of-abuse screens that use immunoassays.

Intradural calcifying fibroblastic proliferation associated with a nerve root: a reactive process mimicking a nerve sheath tumor.

Study Design. Case Report. Objective. To share our experience about the unique histological appearances of a calcified intradural, extramedullary lesion involving a nerve root. Summary of Background Data. A 53-year-old man presented with a long history of low back pain and a few months of occasional left groin pain with no neurological deficit. Imaging of the spine revealed a calcified intradural extramedullary lesion at L1, separate from vertebrae. Intraoperatively, the lesion was found to involve closely one of the roots and was heavily calcified but relatively easy to excise. The histology revealed calcifying fibroblastic proliferation associated with a nerve root. This is an unusual pathological entity, which appears distinct from the rare but occasionally reported reactive process known, as heterotopic bone formation in a nerve or “neuritis ossificans,” and it is important to distinguish it from other calcified intradural neoplasms. Methods. The histology of an excised calcified intradural extramedullary lesion was initially reviewed by our local neuropathologist. A second opinion was requested from Prof. Malcolm, who is a histopathologist and bone specialist. The unique histological features of the lesion were confirmed. The literature (no date limitations) was reviewed. Results. A calcified intradural extramedullary lesion, closely related to nerve root was found to have unique histological features, not reported in the literature so far. Conclusion. The histological features of the calcified lesion that we report here have not been described before. It is highly likely they represent a reactive process. We think these features are useful to be added to the differential diagnosis of a calcified intradural extramedullary lesion involving a nerve root.

A Patient With Alcoholic Ketoacidosis and Profound Lactemia

BACKGROUND Alcoholic ketoacidosis (AKA) is a complex syndrome that results from disrupted metabolism in the setting of excessive alcohol use and poor oral intake. Dehydration, glycogen depletion, high redox state, and release of stress hormones are the primary factors producing the characteristic anion gap metabolic acidosis with an elevated β-hydroxybutyrate (β-OH) and lactate. CASE REPORT We present the case of a 47-year-old man who presented to the emergency department with metabolic acidosis and profoundly elevated lactate levels who had AKA. He recovered completely with intravenous fluids and parenteral glucose administration. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should always consider the immediately life-threatening causes of a severe anion gap metabolic acidosis and treat aggressively based on the situation. This case highlights the fact that AKA can present with an impressively elevated lactate levels. Emergency physicians should keep AKA in the differential diagnosis of patients who present with a similar clinical picture.

Cardiotoxicodynamics: Toxicity of Cardiovascular Xenobiotics

Maintaining adequate tissue perfusion depends on a variety of factors, all of which can be influenced by xenobiotics (substances foreign to the body, including pharmaceuticals, chemicals, and natural compounds). Volume status, systemic vascular resistance, myocardial contractility, and cardiac rhythm all play a significant role in ensuring hemodynamic stability and proper cardiovascular function. Direct effects on the nervous system, the vasculature, or the heart itself as well as indirect metabolic effects may play a significant role in the development of cardiotoxicity. This article is dedicated to discussion of the disruption of cardiovascular physiology by xenobiotics.

A 29-year analysis of acute peak salicylate concentrations in fatalities reported to United States poison centers

Abstract Background/Objectives: The threshold salicylate concentration commonly recommended to initiate extracorporeal elimination, in the absence of significant end-organ toxicity, is 100 mg/dL. Unfortunately, the grade of evidence to support this decision is low. Our primary aim is to describe highest reported salicylate concentrations in patients who died from acute salicylate ingestions. Our secondary aim is to determine if age or coingestants varied with highest reported salicylate concentration. Methods: We analyzed acute salicylate fatalities reported to the National Poison Data System (NPDS) between 1 January 1986 and 31 December 2014. Included were patients who died during the index hospitalization and for which acute salicylate toxicity was the primary cause of death. We used descriptive statistics with standard deviations (SD) or 95% confidence intervals (CI) where appropriate. We created a general linear model that evaluated the association of age and coingestions with salicylate concentrations. We divided the patients into age quartiles to assess a possible interaction between age and salicylate concentration. Results: We identified 602 acute salicylate fatalities that fit inclusion criteria. The mean peak reported fatal salicylate concentration across all age groups was 99.19 mg/dL (± 50.2 mg/dL). The median peak fatal salicylate concentration was 97.0 mg/dL. The oldest quartile had a lower mean concentration (age >57 years; 90.4 mg/dL) than the youngest quartile (age <30 years; 111.6 mg/dL, mean difference 21.2 mg/dL, 95%CI 6.1–36.3). Fatalities with a coingestant had a lower mean concentration of 91.5 mg/dL compared to 104.8 mg/dL among those ingesting salicylates alone (mean difference 13.4 mg/dL, 95%CI 21.4–5.3). Increasing age and the presence of any coingestions were negatively associated with fatal concentrations (estimates; 95%CI 0.41; 0.61–0.021 and −14.43; 22.45–6.42, respectively). When opioids were a coingestant, mean concentration was 72.8 (mean difference 32.1 95%CI 23.1–41.1). Conclusions: Using the current recommended hemodialysis threshold of 100 mg/dL, more than half of the patients would be deprived of this critical life-saving therapy. Additionally, increasing age and ingestion of other substances, especially opioids, are associated with lower peak fatal salicylate concentrations. A prospective, randomized controlled trial considering salicylate concentrations and other clinical factors may provide further guidance for hemodialysis.

Carbon Monoxide Poisoning Due to “Mud Bogging”

Mud bogging is a sport in which motor vehicles may become trapped in mud that clogs exhaust pipes. Four cases of carbon monoxide poisoning related to mud bogging are described.

Pygmy rattlesnake envenomation treated with Crotalidae Polyvalent Immune Fab Antivenom

UNLABELLED Documented envenomations by the pygmy rattlesnake (Sistrurus miliarius barbouri) are rare. While there have been no documented fatalities, several older case reports describe significant morbidity. We describe the first known case of pygmy rattlesnake envenomation that was treated with Crotalidae Polyvalent Immune Fab Antivenom (CroFab®). CASE A 28-year-old man with no significant past medical history presented after being envenomated on the right hand by his friends pet pygmy rattlesnake. He developed swelling and pain in his hand and forearm. He responded well to a ten vial loading dose and a 18 h maintenance protocol of CroFab and was discharged the following day without developing any hematological or electrolyte derangements. CONCLUSION This is the first documented use of CroFab for S. m. barbouri envenomation. The outcome of this case suggests that CroFab is a safe treatment modality in this setting.