Pearl of the Day: Anticholinergic Toxicity

Anticholinergic Toxicity Background - sources: antihistamines, belladonna, mydriatic agents (e.g., tropicamide, cyclopentolate), TCAs, benztropine, phenothiazines, clozapine, olanzapine, Amanita muscaria - can be absorbed through ingestion, smoking, or ocular use - muscarinic blockade delays gastric emptying -> absorption and peak clinical effects are delayed - cholinergic receptors: muscarinic, nicotinic - central anticholinergic syndrome: fever, agitation, delirium, coma - peripheral anticholinergic syndrome: tachycardia, flushed dry skin, dry mouth, ileus, urinary retention - risk of toxicity is dose related

Signs/Symptoms - dry as a bone, red as a beet, hot as a hare, blind as a bat, mad as a hatter, stiff as a pipe - usually sinus tachycardia (wide-complex tachydsyrhythmias with diphenhydramine occur from sodium-channel blockade, not anticholinergic effect) - delirium described as restlessness, irritability, disorientation, auditory and visual hallucinations (e.g., Lilliputian hallucinations) - dysarthria described as staccato speech, high-pitched cries - myoclonus

Diagnosis/Work-up - BMP, CPK, urine toxicology - positive drug screen only indicates exposure, does not imply overdose - differential diagnosis: viral encephalitis, Reye's syndrome, head trauma, post-ictal state, neuroleptic malignant syndrome

Treatment - activated charcoal if ingestion within 1 hour, though may be beneficial beyond 1 hour of ingestion - multidose activated charcoal not recommended with impaired GI motility - supportive care, IVF, temperature monitoring and treatment - agitation -> benzodiazepines IV; avoid physical restraints - wide-complex tachydysrhythmias -> sodium bicarbonate IV

Physostigmine - 0.5 - 2 mg (pediatrics 0.02 mg/kg) by slow IV over 5 min - reversible acetylcholinesterase inhibitor that crosses blood-brain barrier - adverse effects of bradycardia and seizures more likely in patients without anticholinergic effects -> should not be used as diagnostic challenge - mixed evidence - may be better at controlling agitation and reversing delirium than benzodiazepines - indications: seizure, delirium, narrow QRS supraventricular tachydysrhythmias, hemodynamic deterioration - effects may occur within 15 - 20 min, requires continuous cardiac monitoring for bradycardia - may repeat dosing - asymptomatic for 6 hours -> no repeat dosing required - contraindications: asthma, intestinal/bladder obstruction, cardiac conduction disturbances, sodium-channel antagonist poisoning

Disposition - symptomatic patients (including those receiving physostigmine) require hospital obervation for at least 24 hours - patients with mild symptoms that resolve within 6 hours may be discharged

Resources Tintinalli's Emergency Medicine, 8th Edition https://lifeinthefastlane.com/ccc/anticholinergic-syndrome/

Pearl of the Day: Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes Disease Background - hip disorder that occurs between ages 2 - 13 (mostly ages 4 - 9) - avascular necrosis or osteochondrosis in femoral head - repeated episodes of ischemia leading to infarction and necrosis - reossification and remodeling occur over 2 - 4 years -> femoral head collapses -> increased risk of subluxation

Signs/Symptoms - insidious onset - may have mild pain for weeks to months - pain may be referred to anteromedial thigh or knee - muscle spasms, soft tissue contractures, proximal thigh atrophy, limb shortening - decreased hip abduction and internal rotation

Diagnosis/Work-up - initial stages (1 - 3 months): capital femoral epiphysis fails to grow -> radiographs demonstrate widening of cartilage space of affected hip - later, Caffey's sign (subchondral stress fracture line in femoral head) - new bone deposited on avascular trabeculae, calcification of necrotic marrow -> crushing of avascular trabeculae in dome of epiphysis - subluxation and extrusion of femoral head from acetabulum - initial X-rays may be negative, may require bone scan and MRI - differential dx: toxic synovitis, slipped capital femoral epiphysis, acute rheumatic fever, tuberculous arthritis, tumors

Treatment - non-weight bearing - referral to pediatric orthopedist

Resources Tintinalli's Emergency Medicine, 8th Edition

Pearl of the Day: Acute Infectious and Traveler's Diarrhea

Acute Infectious and Traveler's Diarrhea Background - causes: norovirus > non-Shiga toxin producing E. coli > C. difficile > invasive bacteria, Shiga toxin-producing E. coli, protozoa - increased probability of bacterial diarrhea with foreign travel to Asia, Africa, Latin America, Middle East - other risk factors: food contamination, rainy season while traveling, use of proton pump inhibitor, previous history of traveler's diarrhea, type of travel (e.g., adventure travel, living with native inhabitants)

Signs/Symptoms - at least three unformed stools within 24 hours in association with at least one symptom of GI disease (e.g., nausea, vomiting, fever, abdominal pain, cramps, fecal urgency) - usually 4- 5 loose stools without fever, lasting for 3 - 4 days

Work-up - stool studies indicated for severe abdominal pain, fever, or bloody stool - fecal leukocytes - stool culture (for Salmonella, Shigella, Campylobacter, E. coli O157:H7) - assay for Shiga toxin - microscopy or antigen assay for E. histolytica - exposure to untreated water, illness > 7 days -> evaluate for protozoal infections (enzyme assay for E. histolytica, Giardia intestinalis, Cryptosporidium parvum antigens)

Management - primarily supportive care - antibiotics reduce duration of illness by 24 hours, recommended for patients with ≥3 unformed stools in 8 hours - antibiotics contraindicated for bloody diarrhea due to risk of hemolytic uremic syndrome - all patients, regardless of work-up, improve on ciprofloxacin (may be given as single dose; full three-day course if presence of invasive disease) - trimethoprim/sulfamethoxazole also shortens duration, but inferior to ciprofloxacin - azithromycin for children and pregnant women, areas with fluoruinolone resistance - loperamide shortens duration of symptoms when combined with antibiotics - avoid use of antimotility agents (may prolong fever, increase risk of toxic megacolon, HUS)

Resources Tintinalli's Emergency Medicine, 8th Edition https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1539099/