Rapid sequence intubation is commonly performed in the emergency department to secure the airway of critically ill patients. However, blood pressure may decrease during or shortly after intubation because of the patient's underlying illness, the effects of induction medications, and the transition to positive-pressure ventilation. This complication is known as peri-intubation hypotension and is associated with worse clinical outcomes.

This study will evaluate whether a preemptive low dose of intravenous adrenaline, also known as epinephrine, can reduce peri-intubation hypotension in adult emergency department patients undergoing rapid sequence intubation. Participants will be randomly assigned to receive either 10 mcg of intravenous adrenaline or 1 mL of 0.9% sodium chloride placebo immediately before induction. The study will compare hemodynamic changes, vasopressor requirements, safety outcomes, and mortality between the two groups.

Rapid sequence intubation is a standard advanced airway procedure used in emergency departments for critically ill patients who require rapid and secure airway control. Although this procedure is clinically necessary, it may be associated with peri-intubation hypotension, commonly defined as systolic blood pressure below 90 mmHg or mean arterial pressure below 65 mmHg during or after the intubation period. This hemodynamic deterioration may result from the patient's underlying critical illness, the cardiovascular effects of induction agents, reduced venous return after initiation of positive-pressure ventilation, or a combination of these factors.

Preventing hypotension during rapid sequence intubation is an important component of peri-intubation resuscitation. Intravenous fluids and vasopressor infusions are frequently used when hypotension develops, but these interventions may not always be fast enough to prevent early hemodynamic collapse. Push-dose vasopressors are used in emergency and critical care practice to provide short-term hemodynamic support. However, prospective randomized evidence regarding the preemptive use of push-dose adrenaline during emergency department rapid sequence intubation remains limited.

This is a single-center, prospective, randomized, double-blind, placebo-controlled trial conducted in the emergency department of Marmara University Pendik Training and Research Hospital. Adult patients undergoing rapid sequence intubation, who are hypotensive or considered to be at significant risk of hypotension, will be enrolled after informed consent is obtained from the patient or legally authorized representative when applicable.

Participants will be randomized in a parallel-group design to receive either 10 mcg intravenous adrenaline or 1 mL of 0.9% sodium chloride placebo immediately before the administration of induction agents. The intervention and placebo syringes will be identical in volume and appearance. Syringes will be prepared according to the randomization list by an independent non-blinded nurse who will not participate in clinical care, outcome assessment, or data collection. Treating physicians, participants, investigators, care providers, and outcome assessors will remain blinded to group allocation.

The decision to perform intubation, selection and dosing of induction and neuromuscular blocking agents, endotracheal tube size, and post-intubation management will be determined by the treating physician according to standard emergency department practice and current clinical guidance. Study procedures will not delay airway management or standard resuscitative care.

Hemodynamic variables, including systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate, will be recorded at baseline and during the first 60 minutes after intubation. The study will evaluate peri-intubation hypotension, changes in mean arterial pressure, post-intubation vasopressor requirements, new ventricular or supraventricular arrhythmias, reactive hypertension, cardiac arrest, and mortality at predefined time points. The planned enrollment is 128 participants.

Inclusion Criteria:

• Adult patients aged 18 years or older
• Patients in the emergency department for whom the treating physician has made a clinical decision to perform rapid sequence intubation
• Patients who are hypotensive, defined as systolic blood pressure less than 90 mmHg or mean arterial pressure less than 65 mmHg, or who are considered to be at significant risk of hypotension during rapid sequence intubation
• Written informed consent obtained from the patient or from a legally authorized representative when the patient lacks decision-making capacity

Exclusion Criteria:

• Pregnancy
• Known allergy to adrenaline
• Known contraindication to adrenaline administration
• Withdrawal of consent by the patient or legally authorized representative after enrollment

The intervention and placebo syringes will be identical in volume, color, and appearance and will be labeled only with a unique case code. Syringes will be prepared according to the randomization list by an independent non-blinded researcher who will not participate in clinical care, data collection, or outcome assessment. Participants, treating clinicians, investigators, care providers, and outcome assessors will remain blinded to group allocation until completion of data collection.