In a trauma patient with possible brain injury, the goal is to keep enough blood flow to the brain and other organs while we work on bleeding control. Cerebral perfusion pressure depends on the mean arterial pressure minus the intracranial pressure, and when brain injury is suspected (GCS 7), you want a higher perfusion pressure to prevent ischemia if ICP is elevated. In the prehospital setting, a practical minimum systolic blood pressure of about 90 mm Hg is used to ensure adequate perfusion without over-resuscitating before hemorrhage control. Values well below that (60–70) risk dangerous hypoperfusion to the brain and other organs, while 80 is often not enough in a brain-injured patient. Therefore, aiming for at least 90 mm Hg supports cerebral and systemic perfusion until definitive bleeding control is achieved.

Cavitation is the displacement of tissue away from the projectile’s path as energy from the projectile is deposited into the tissues. This rapid energy transfer creates a temporary cavity that can be much larger than the bullet track, causing extensive damage beyond the actual wound path. The wound left along the path is the permanent cavity, but the surrounding tissue is stretched and displaced outward by cavitation. This SAMPLEdistinguishes cavitation from contusion (a bruise from blunt impact) and crepitation (a crackling sound or feel from air or emphysema), and from conization, which is unrelated to ballistic injury.

The secondary survey is the thorough, systematic head-to-toe assessment you perform after the major life threats have been addressed in the primary survey. It centers on completing a comprehensive examination of all body regions, reassessing the patient’s condition, and collecting important contextual information such as the mechanism of injury, vitals, and the patient’s history. This approach helps uncover injuries that aren’t immediately life-threatening but could worsen if missed, and it guides ongoing treatment and disposition decisions. After stabilizing airway, breathing, and circulation, you methodically inspect from head to toe, reassess vital signs to catch any early deterioration, and obtain a concise history (including mechanism of injury) to correlate findings with the patient’s presentation. The other options don’t fit because a quick airway check is part of the primary survey, imaging is not performed universally as part of the secondary survey, and a mere review of systems with minimal exam does not constitute the comprehensive head-to-toe assessment and reassessment that defines the secondary survey.

Adequate spontaneous ventilation means enough alveolar ventilation to support gas exchange, which depends on both tidal volume and rate. In adults, a practical rest range is about 500 mL per breath with roughly 12 breaths per minute, giving roughly 4–7 L/min of alveolar ventilation after accounting for dead space. The best choice here uses a tidal volume of 600 mL at 12 breaths per minute. With an estimated dead space of about 150 mL, alveolar ventilation per breath is 600 − 150 = 450 mL. Multiplying by 12 breaths per minute gives about 5.4 L/min of alveolar ventilation, which is adequate for gas exchange at rest. The other options fall short because their alveolar ventilation is too low: 500 mL at 8/min yields around 2.8 L/min; 300 mL at 16/min yields around 2.4 L/min; and 100 mL at 40/min provides negligible alveolar ventilation despite the high rate. That makes them inadequate for maintaining proper CO2 removal and O2 delivery.