Toxicology, Environmental & Infectious Diseases Flashcards

A scuba diver surfaces too quickly and develops joint pain, dyspnea, and marbling of the skin. Which chamber pressure is used in hyperbaric oxygen therapy for decompression sickness?

Answer: 2.8 ATA

US Navy Treatment Table 6 uses 2.8 ATA with 100% oxygen to maximize bubble reabsorption and treat decompression illness.

A 30-year-old with fever, painless ulcer on the penis, and bilateral inguinal lymphadenopathy is diagnosed with primary syphilis. He has a documented penicillin allergy with anaphylaxis. What is the recommended alternative?

Answer: Desensitization followed by penicillin G benzathine

Penicillin G benzathine is the only proven treatment for all stages of syphilis; in penicillin-allergic patients with primary syphilis, doxycycline is acceptable but desensitization is preferred in non-pregnant patients with neurosyphilis or pregnancy.

A patient with fever and rigors after returning from sub-Saharan Africa has a peripheral blood smear showing ring-form parasites in >5% of RBCs with multiple parasites per RBC. Which malaria species is most likely?

Answer: Plasmodium falciparum

Plasmodium falciparum causes high-density parasitemia (>5% RBCs infected), multiple ring forms per cell, and is responsible for cerebral malaria and life-threatening complications.

A patient presents with descending flaccid paralysis, dry mouth, diplopia, and ptosis after eating home-canned green beans. Autonomic function is preserved. Which toxin mechanism is responsible?

Answer: Blockade of presynaptic acetylcholine release at the neuromuscular junction

Botulinum toxin cleaves SNARE proteins, blocking presynaptic acetylcholine vesicle release at the neuromuscular junction, causing flaccid paralysis.

Which of the following is a reliable clinical feature distinguishing heat stroke from severe heat exhaustion?

Answer: Central nervous system dysfunction

CNS dysfunction (altered mentation, seizures, coma) is the defining feature of heat stroke and differentiates it from heat exhaustion, where cognition remains intact.

A patient is bitten by a copperhead snake and develops local swelling to the forearm. Which of the following is the STRONGEST indication for antivenom (Crotalidae polyvalent immune Fab)?

Answer: Swelling progressing across one joint boundary

Rapidly progressive edema crossing joint boundaries indicates significant envenomation and warrants antivenom (CroFab) to prevent compartment syndrome and tissue necrosis.

A patient presents with altered mental status, hyperthermia, lead-pipe rigidity, and markedly elevated CPK after starting haloperidol two weeks ago. What distinguishes neuroleptic malignant syndrome (NMS) from serotonin syndrome?

Answer: NMS has slower onset and lead-pipe rigidity; SS has rapid onset and clonus/hyperreflexia

NMS develops over days-weeks with lead-pipe rigidity and lacks the clonus/hyperreflexia of serotonin syndrome, which has rapid onset (hours) after serotonergic drug exposure.