Acid-base disorders are common among critically ill patients admitted to the emergency department, and were present in up to 97% of patients, in a study carried out in a resuscitation suite [1]. Most of these acid-base disturbances include acidemia, defined as a pH lower than 7.4 whether as pure acidemia or complex disorders combined with alkalemia [2,3].

Tissue acidosis, expressed as acidemia, is an expression of numerous pathologies that are prevalent in patients referred to the emergency department and resuscitation suite. Most important of those are hemodynamic instability, respiratory failure, renal and hepatic insufficiency, severe infections, trauma, different metabolic disorders and toxic ingestions. Accordingly, acidemia has been shown to be a poor prognostic factor [4].

Moreover, acute severe tissue acidosis, affects several body systems and may lead to hemodynamic instability, immune, neurologic and metabolic compromise [4]. The presence of those pathologies, together with acidemia being a manifestation of a critical illness, is the reason that extreme acidemia, usually defined as a pH value that falls below 6.8–7.0, is considered to be incompatible with life [5,6].

However, there are several reports of patients surviving extreme acidemia, in rare cases, even when pH dropped to 6.35. Acidemia in those reports was secondary to a variety of etiologies, including hemorrhage, toxic ingestions, drowning and metabolic disorders [[7], [8], [9], [10], [11]].

As the mortality rate in this patient group is still unknown, describing the prognostic impact of severe acidemia on emergency department arrival may have a significant influence in decision making in the first hours of resuscitation.

In this retrospective cohort study, we aim to assess the mortality rate in patients who had extreme acidemia during the 12 first hours of emergency department admission, and to examine whether we can find prognostic factors, which may improve decision-making during resuscitation and resource allocation.