Regional readiness for sodium nitrite-induced methemoglobinemia: availability of methemoglobin testing and methylthioninium chloride (methylene blue) stocking in the Upper Midwestern United States

Introduction: Sodium nitrite is a potent oxidizer, which may precipitate rapidly lethal methemoglobinemia. Prompt diagnosis and treatment may salvage otherwise fatal cases. It is unclear if emergency departments are prepared for increasing cases. We describe the availability and geographic distribution of real-time methemoglobin testing and methylthioninium chloride (methylene blue) availability in three contiguous United States.

Methods: This is a cross-sectional survey of hospitals served by a regional poison center in the Upper Midwestern United States. Hospitals were identified by cross-referencing poison center, health department, and state trauma databases. We queried methemoglobin testing capabilities of each site as well as immediate methylthioninium chloride availability. Resulting data are described with descriptive statistics, and predictors of testing and treatment availability are evaluated in multivariable logistic regression.

Results: We identified 320 hospitals with emergency care, analyzing 228 (71.3%) after exclusions. Real-time methemoglobin testing was available at 56 sites (30.6% of 183 respondents). Of hospitals describing methylthioninium chloride availability, 59.4% (130/219) reported having it on-site. A significant difference in real-time methemoglobin testing existed across largest and smallest population strata in adjusted analysis (OR: 64.6: 95% CI: 4.1-1,037). Similarly disparate availability of methylthioninium chloride was observed. Spatial distribution of methemoglobin testing and methylthioninium chloride availability demonstrated notable urban-rural disparities.

Discussion: These data demonstrate a wide disparity in the availability of real-time methemoglobin testing and methylthioninium chloride availability, suggesting that the region is ill-prepared to care for severe methemoglobinemia. Our analysis points to a disconnect between our current poison center recommendations and the capacities of our consulting institutions.

Conclusions: We demonstrate urban-rural disparities in diagnostic and therapeutic capacity for the management of acute methemoglobinemia in this region, as well as significant geographic variations in methylthioninium chloride stocking and poisoning preparedness. Poison centers must therefore maintain an awareness of antidote availability for this emerging toxicological emergency.