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HYDROGEN SULFIDE : Does Hyperbaric Oxygen work?

HYDROGEN SULFIDE : Does Hyperbaric Oxygen work?. Case of the week December 12, 2003 Rob Hall MD. H2S Knock-down case of the week!. How is H2S toxic?. Inhibits cytochrome oxidase Thus inhibits oxidative phosphorylation Anaerobic metabolism can ’ t keep up! -------------> CELLULAR HYPOXIA

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HYDROGEN SULFIDE : Does Hyperbaric Oxygen work?

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  1. HYDROGEN SULFIDE:Does Hyperbaric Oxygen work? Case of the week December 12, 2003 Rob Hall MD

  2. H2S • Knock-down case of the week!

  3. How is H2S toxic? • Inhibits cytochrome oxidase • Thus inhibits oxidative phosphorylation • Anaerobic metabolism can’t keep up! • -------------> CELLULAR HYPOXIA • EARLY DEATH • Respiratory paralysis due to toxic effect at the respiratory centers

  4. Permanent Neurologic Sequelae • Prolonged coma • Recurrent seizures • Chronic vegatative states • Tremors • Cognitive impairment

  5. Why might HBOT be effective? • Increased oxygen delivery to tissues • Increased oxyhemoglobin which increases the auto-oxidation of sulfide

  6. What are the TEXTBOOK recommendations for HBOT? • Haddad. 1998. • “May be beneficial in patients in whom CNS symptoms do not resolve spontaneously or with prompt nitrite therapy” • Ford. • “Should be used in neurologically compromised or acidemic patients refractory to conventional therapy” • Goldfrank 2003 • “All patients should receive HBOT if readily available; transport solely for HBOT is unnecessary”

  7. H2S and HBOT…… So what is the evidence??

  8. 1) Vicas. Vet Hum Toxicol 1989 • 30 yo male • H2S contaminated petroleum • Unconcscious on arrival in ED • 3 HBO treatments 13 hr post exposure • 2 further HBO treatment • Increased LOC, memory, verbal interaction, problem solving • Persistent retrograde amnesia

  9. 2) Al-Mahesneh. Vet Hum Toxicol 1989 • Acute exposure to known high [H2S] • Comatose, unresponsive, F/D pupil on arrival in the ED • Flown to hyperbaric chamber (?delay) • HBOT for 3 hours • NO improvement • Patient died at 56hrs after exposure

  10. 3) Snyder. Am J Emerg Med 1995 • Construction pit on of New Jersey coast • Two men knocked – down, several other rescuers knocked down, 1 Dead on scene • Worker 1 • GCS 3 on arrival, sent for HBO • 12 hour delay until HBOT started

  11. 3) Snyder. Am J Emerg Med 1995 • Day1 • One session of 2ATA for 45 min • GCS 3 -> 5 • Day 2 • Two sessions of 1.5 ATA for 90 min each • Day3 – 7 • Two sessions of 1.0 ATA for 90 min each • Day 3 GCS 7, Day 5 GCS 11, Day 7 GCS 15 • Day 8-16 • One session of 1.0 ATA for 90 min

  12. 3) Snyder. Am J Emerg Med 1995 • Persistent Neurological Sequelae • Slow speech, flat affect, inability to concentrate, impaired visual memory, easily distractible, confabulation • Neurologic Sequelae unchanged at 12 and 18 months

  13. 4) Schneider. Occ Med 1998 • 27yo male • Building a sewer system in New Jersey • Rescuer died at the scene • GCS 3 on arrival at ED • Transfer for HBOT 10hrs after exposure • 2 ATA for 45 min bid X “several” days • Regained consciousness on day 5 • GCS 11 on day 7 then improved to 15 • Similar neurological sequelae to last case noted at one month and 4yrs post incident

  14. Neuroimaging • CT head was normal in this case on day of exposure • MRI was normal at 17 months despite persistent neurological sequelae • PET scan at 3 years showed marked decrease in perfusion to thalamus, basal ganglia and abnormal metabolic patterns in the temporal and parietal lobes

  15. NOTE • Normal CT or MRI of brain does not preclude permanent neurologic sequelae!

  16. 5) Smilkstein. J Emerg Med 1985 • 34 yo male • Oil pump waste collection tank • GCS of 7 on arrival to ED • HBOT started 10hrs after exposure • Total of 12 HBOT treatments over 6 days • #1: 2.5 ATA for 45 min • #2: 2.0 ATA for 75 min • #3-12: 2 ATA for 90-120 min • Outcome: stepwise improvement, awake/alert by 48hrs, slight difficulty with complex tasks persisted

  17. 6) Harefuah. 1994 • Another Case report of H2S treated with HBOT • Hebrew!

  18. The RATS have the last word!Bitterman. Tox Appl Pharm 1986 • Rat model: several groups with 20 rats each • LD 75 dose of intraperitoneal sodium sulfide • Various treatments after sulfide injection • Group 1: no treatment • Group 2: sodium nitrite + room air • Group 3: 100% oxygen • Group 4: HBOT at 2 ATA • Group 5: sodium nitrite + 3 ATA HBOT • Various treatments before sulfide injection • Group 7: HBOT 3 ATA • Group 8: sodium nitrite and HBOT 3ATA

  19. The RATS have the last word!Bitterman. Tox Appl Pharm 1986 pretreatement rescue treatments

  20. The RATS have the last word!Bitterman. Tox Appl Pharm 1986 • Conclusions from the rats • Methemoglobinemia alone not beneficial • Oxygen beneficial • HBOT + methemoglobinemia beneficial

  21. SUMMARY: H2S and HBOT • 6 Case reports: 5 +ve, 1 -ve • Case reports have significant delay from exposure to HBOT: does this matter? • 1 Animal model • NO case series • NO controlled trials

  22. Summary • HBOT may have a role in the management of H2S toxicity but it’s efficacy is LARGELY UNKNOWN

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