Carbon Monoxide Poisoning: Pathogenesis, Management, and Future Directions of Therapy

Mass Casualty Triage in the Case of Carbon Monoxide Poisoning: Lessons Learned

ABSTRACTCarbon monoxide (CO) can cause mass intoxication, but no standard triage algorithm specifically addresses CO poisoning. The roles of some recent diagnostic tools in triage as well as treatment with hyperbaric oxygen are controversial. We describe a mass casualty case of CO poisoning involving 77 patients, with a focus on the triage and treatment options decided on-site. The reasons for choosing these options are reviewed, and the pitfalls that occurred and the lessons learned from this major incident are described. We discuss the potential to improve the management of such an event and strategies to accomplish this, including simplifying triage and administering oxygen to all exposed persons for 6 h. (Disaster Med Public Health Preparedness. 2018; 12: 373-378).

Gaseous Mediators and Mitochondrial Function: The Future of Pharmacologically Induced Suspended Animation?

The role of nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S) as poisonous gases is well-established. However, they are not only endogenously produced but also, at low concentrations, exert beneficial effects, such as anti-inflammation, and cytoprotection. This knowledge initiated the ongoing debate, as to whether these molecules, also referred to as “gaseous mediators” or “gasotransmitters,” could serve as novel therapeutic agents. In this context, it is noteworthy, that all gasotransmitters specifically target the mitochondria, and that this interaction may modulate mitochondrial bioenergetics, thereby subsequently affecting metabolic function. This feature is of crucial interest for the possible induction of “suspended animation.” Suspended animation, similar to mammalian hibernation (and/or estivation), refers to an externally induced hypometabolic state, with the intention to preserve organ function in order to survive otherwise life-threatening conditions. This hypometabolic state is usually linked to therapeutic hypothermia, which, however, comes along with adverse effects (e.g., coagulopathy, impaired host defense). Therefore, inducing an on-demand hypometabolic state by directly lowering the energy metabolism would be an attractive alternative. Theoretically, gasotransmitters should reversibly interact and inhibit the mitochondrial respiratory chain during pharmacologically induced suspended animation. However, it has to be kept in mind that this effect also bears the risk of cytotoxicity resulting from the blockade of the mitochondrial respiratory chain. Therefore, this review summarizes the current knowledge of the impact of gasotransmitters on modulating mitochondrial function. Further, we will discuss their role as potential candidates in inducing a suspended animation.

Five-coordinate H64Q neuroglobin as a ligand-trap antidote for carbon monoxide poisoning

Carbon monoxide (CO) is a leading cause of poisoning deaths worldwide, with no available antidotal therapy. We introduce a potential treatment paradigm for CO poisoning, based on near-irreversible binding of CO by an engineered human neuroglobin (Ngb). Ngb is a six-coordinate hemoprotein, with the heme iron coordinated by two histidine residues. We mutated the distal histidine to glutamine (H64Q) and substituted three surface cysteines with less reactive amino acids to form a five-coordinate heme protein (Ngb-H64Q-CCC). This molecule exhibited an unusually high affinity for gaseous ligands, with a P50 (partial pressure of O2 at which hemoglobin is half-saturated) value for oxygen of 0.015 mmHg. Ngb-H64Q-CCC bound CO about 500 times more strongly than did hemoglobin. Incubation of Ngb-H64Q-CCC with 100% CO-saturated hemoglobin, either cell-free or encapsulated in human red blood cells, reduced the half-life of carboxyhemoglobin to 0.11 and 0.41 min, respectively, from ≥200 min when the hemoglobin or red blood cells were exposed only to air. Infusion of Ngb-H64Q-CCC to CO-poisoned mice enhanced CO removal from red blood cells, restored heart rate and blood pressure, increased survival, and was followed by rapid renal elimination of CO-bound Ngb-H64Q-CCC. Heme-based scavenger molecules with very high CO binding affinity, such as our mutant five-coordinate Ngb, are potential antidotes for CO poisoning by virtue of their ability to bind and eliminate CO.