This prospective observational cohort study aims to investigate the incidence and determinants of post-intubation cardiac instability (PICI) among emergency department (ED) patients with physiologically difficult airways (PDA), defined by profound physiological disturbances including severe hypoxemia, hypotension, metabolic acidosis, or shock states. Emergency intubation in such patients, is associated with a heightened risk of peri-intubation cardiovascular collapse and adverse outcomes. Despite this, current airway guidelines focus largely on anatomical difficulty, neglecting the profound physiological derangements that more strongly predict morbidity and mortality.

Existing literature indicates that post-intubation hypotension and cardiac arrest are not uncommon in critically ill patients, with an estimated incidence of cardiovascular instability ranging from 30% to 45%. Russotto et al.’s INTUBE study, involving nearly 3,000 ICU patients, reported a 43.4% incidence of peri-intubation cardiovascular collapse. Similar findings were observed in ED settings, where the presence of shock, hypoxemia, or acidosis was strongly linked to poor outcomes. Emerging tools such as the Difficult Airway Physiological Score (DAPS) further underscore the prognostic importance of physiological parameters over anatomical markers.

The primary objective of this study is to quantify the incidence of PICI in ED patients meeting PDA criteria. Secondary objectives include identifying independent physiologic predictors of PICI, comparing the effects of different induction agents (e.g., ketamine vs etomidate), evaluating the influence of first-pass success and pre-intubation vasopressor use, and developing a preliminary risk stratification tool. Additionally, the study will assess the impact of post-intubation hemodynamic management on short-term outcomes, including 24-hour mortality.

The study will enroll at least 550 adult ED patients requiring intubation and exhibiting PDA features (hypotension, hypoxemia, or acidosis). Patients intubated outside the ED, those in pre-intubation cardiac arrest, or those re-intubated within 24 hours will be excluded. The primary outcome is the incidence of PICI, defined by standardized criteria including sustained hypotension, new or increase in vasopressor requirement, or cardiac arrest within 30 minutes of intubation. Secondary outcomes include ICU/hospital length of stay and mortality at 24 hours, 7 days, and 28 days.