In Vivo Interactions Between Cobalt or Ferric Compounds and the Pools of Sulphide in the Blood During and After H2S Poisoning

Abstract

Hydrogen sulphide (H2S), a chemical hazard in oil and gas production, has recently become a dreadful method of suicide, posing specific risks and challenges for the first responders. Currently, there is no proven effective treatment against H2S poisoning and its severe neurological, respiratory or cardiac after-effects. We have recently described that H2S is present in various compartments, or pools, in the body during sulphide exposure, which have different levels of toxicity. The general goals of our study were to (1) determine the concentrations and kinetics of the various pools of hydrogen sulphide in the blood, i.e., gaseous (CgH2S) versus total sulphide, i.e., reacting with monobromobimane (CMBBH2S), during and following H2S exposure in a small and large mammal and (2) establish the interaction between the pools of H2S and a methemoglobin (MetHb) solution or a high dose of hydroxocobalamin (HyCo). We found that CgH2S during and following H2S infusion was similar in sedated sheep and rats at any given rate of infusion/kg and provoked symptoms, i.e., hyperpnea and apnea, at the same CgH2S. After H2S administration was stopped, CgH2S disappeared within 1 min. CMBBH2S also dropped to 2-3μM, but remained above baseline levels for at least 30 min. Infusion of a MetHb solution during H2S infusion produced an immediate reduction in the free/soluble pool of H2S only, whereas CMBBH2S increased by severalfold. HyCo (70 mg/kg) also decreased the concentrations of free/soluble H2S to almost zero; CgH2S returned to pre-HyCo levels within a maximum of 20 min, if H2S infusion is maintained. These results are discussed in the context of a relevant scenario, wherein antidotes can only be administered after H2S exposure.

Effects of infusion of human methemoglobin solution following hydrogen sulfide poisoning

“…To our knowledge, all previous studies on the efficacy of MetHb have demonstrated beneficial effects against H 2 S-induced lethality, particularly in rodents, when nitrite-induced methemoglobinemia was injected prior to 6,25 or during H 2 S exposure 15 . We have recently found 13 that infusion of a similar levels of methemoglobin in rat during H 2 S exposure produces an immediate reduction in CgH 2 S by more than half, while CMBBH 2 S increased by several folds. The latter reflects the creation of a new sink (ferric iron) capable of combining free H 2 S.…”

“…Expired H 2 S was determined as previously described 13,15 . The fraction of H 2 S was continuously measured from the second mixing chamber, allowing the calculation of the partial pressure of expired H 2 S (P E H 2 S) and of the alveolar pressure (P A H 2 S) assuming to be equivalent to H 2 S arterial partial pressures (PaH 2 S) (see 15 for further details).…”

“…To overcome some of the side effects of nitrite-induced methemoglobinemia (drop in blood pressure, unpredictable methemoglobin (MetHb) levels, potentiation of the effects of H 2 S by Nitric Oxide, we used an infusion of a solution of methemoglobin 13 and have showed that, during H 2 S infusion, the presence of methemoglobin dramatically decreases the amount of free/diffusible H 2 S in the blood. MetHb is effective at concentrations starting at 4-5% 11 and is capable of combining with H 2 S as soon as it enters in the blood, as shown in both sheep 14 and rat models 11 .…”

“…MetHb is effective at concentrations starting at 4-5% 11 and is capable of combining with H 2 S as soon as it enters in the blood, as shown in both sheep 14 and rat models 11 . Consequently, the pool of combined H 2 S, which represents the largest pool of H 2 S in the blood during sulfide exposure, increases in the presence of MetHb 13 . The “antidotal” properties of methemoglobin against H 2 S poisoning must however be relevant when used in a scenario faithful to H 2 S intoxication in human, that is following H 2 S exposure.…”

Calculation of Conditional Equilibrium in Serial Multiple Precipitation of Metal Sulfides With Hydrogen Sulfide Stream Generated From Sodium Sulfide: A Didactic Tool for Chemistry Teaching

“…3 This state was consulted also in European Commission with these conclusions: · The reason of the educational regress in natural sciences is mostly due to the deductive approach based on remembering and understanding without training how to use the obtained information in the concrete standard and non-standard situations · Inquiry Based Science Education (IBSE) creates the area for student's own research by applying the inductive approach · It is very convenient conceptually to find the optimal ratio between deductive and inductive approaches As an example we may mention hydrogen sulfide H 2 S. It is well known for its smell like rotten eggs and its high toxicity as nerve agents. [4][5][6] It irritates the eyes and respiratory tract. 7 H 2 S is denser than air and moderately soluble in water with a slight acidic reaction.…”