Blunt trauma, blunt injury, non-penetrating trauma or blunt force trauma is physical trauma to a body part, either by impact, injury or physical attack. The latter is usually referred to as blunt force trauma. Blunt trauma is the initial trauma, from which develops more specific types such as contusions, abrasions, lacerations, and/or bone fractures. Blunt trauma is contrasted with penetrating trauma, in which an object such as a bullet enters the body.
Blunt abdominal trauma (BAT) comprises 75% of all blunt trauma and is the most common example of this injury. The majority occurs in motor vehicle accidents, in which rapid deceleration may propel the driver into the steering wheel, dashboard, or seatbelt causing contusions in less serious cases, or rupture of internal organs from briefly increased intraluminal pressure in the more serious, dependent on the force applied. It is important to note that initially there may be little in the way of overt clinical signs to indicate that serious internal abdominal injury has occurred, making assessment more challenging and requiring a high degree of clinical suspicion.
There are two basic physical mechanisms at play with the potential of injury to intra-abdominal organs: compression and deceleration. The former occurs from a direct blow, such as a punch, or compression against a non-yielding object such as a seat belt or steering column. This force may deform a hollow organ thereby increasing its intra-luminal or internal pressure, leading to rupture. Deceleration, on the other hand, causes stretching and shearing at the points at which mobile structures, such as the bowel, are anchored. This can cause tearing of the mesentery of the bowel, and injury to the blood vessels that travel within the mesentery. Classic examples of these mechanisms are a hepatic tear along the ligamentum teres and injuries to the renal arteries.
In rare cases, this injury has been attributed to medical techniques such as the Heimlich Maneuver, attempts at cardiopulmonary resuscitation and manual thrusts to clear an airway. Although these are rare examples, it has been suggested that they are caused by applying unnecessary pressure when administering such techniques. Finally, the occurrence of splenic rupture with mild blunt abdominal trama in those convalescing from infectious mononucleosis is well reported.
In all but the most obviously trivial injuries, the first concern is to exclude anything that might be quickly or immediately life-threatening. This is resolved by ascertaining that the subject's airway is open and competent, that breathing is unlabored, and that circulation—i.e. pulses that can be felt—is present. This is sometimes described as the "A, B, C's"—Airway, Breathing, and Circulation—and is the first step in any resuscitation or triage. Then, the history of the accident or injury is amplified with any medical, dietary (timing of last oral intake) and past history, from whatever sources such as family, friends, previous treating physicians that might be available. This method is sometimes given the mnemonic "SAMPLE". The amount of time spent on diagnosis should be minimized and expedited by a combination of clinical assessment and appropriate use of technology, such as diagnostic peritoneal lavage (DPL), or bedside ultrasound examination (FAST) before proceeding to laparotomy if required. If time and the patient's stability permits, CT examination may be carried out if available. Its advantages include superior definition of the injury, leading to grading of the injury and sometimes the confidence to avoid or postpone surgery. Its disadvantages include the time taken to acquire images, although this gets shorter with each generation of scanners, and the removal of the patient from the immediate view of the emergency or surgical staff.
Recently, criteria have been defined that might allow patients with blunt abdominal trauma to be discharged safely without further evaluation. The characteristics of such patients would include:
To be considered low risk, patients would need to meet all low-risk criteria.
In the US, the majority of contact-collision injuries, usually blunt trauma, should have been witnessed in high school or collegiate games where the athletic training staff are trained to keep their eyes on the play. This may allow some departure from Advanced Trauma Life Support guidelines in the initial assessment, although the principles always apply. The major priority then becomes separating contusions and musculo-tendinous injuries from injuries to solid organs and the gut and recognizing potential for developing blood loss, and reacting accordingly. Blunt injuries to the kidney from helmets, shoulder pads, and knees are also described in American football, association football, martial arts, and all-terrain vehicle accidents.
In every case where the presumption of internal injury has been sufficient to trigger the diagnostic steps outlined above, intravenous access will be established and crystalloid solutions and/or blood will be administered at rates sufficient to maintain the circulation. Thereafter, further treatment will depend on the grade of organ damage estimated by the prior investigations and will vary from close observation with the ability to intervene quickly, or surgery, open or laparoscopic. In the case of blunt adbominal trauma, there is no shown benefit from surgery unless active bleeding is present.