Abdominal Trauma, Blunt ?>

Abdominal Trauma, Blunt

Abdominal Trauma, Blunt

Introduction

The care of the trauma patient is demanding and requires speed and efficiency. Evaluating patients who have sustained blunt abdominal trauma remains one of the most challenging and resource-intensive aspects of acute trauma care. Missed intra-abdominal injuries and concealed hemorrhage are frequent causes of increased morbidity and mortality, especially in patients who survive the initial phase after an injury.
Physical examination findings are notoriously unreliable for several reasons; a few examples are the presence of distracting injuries, an altered mental state, and drug and alcohol intoxication in the patient. Coordinating a trauma resuscitation demands a thorough understanding of the pathophysiology of trauma and shock, excellent clinical and diagnostic acumen, skill with complex procedures, compassion, and the ability to think rationally in a chaotic milieu. Blunt abdominal trauma usually results from motor vehicle collisions, assaults, recreational accidents, or falls. The most commonly injured organs are the spleen, liver, retroperitoneum, small bowel, kidneys, bladder, colorectum, diaphragm, and pancreas. Men tend to be affected slightly more often than women. Frequency United States By nearly every measure, injury ranks as one of this nation’s most pressing health issues. More than 150,000 people die each year as a result of injuries, such as motor vehicle crashes, fires, falls, drowning, poisoning, suicide, and homicide. Injuries are the leading cause of death and disability for US children and young adults. According to the 2000 statistics from the National Center for Injury Prevention and Control, trauma (unintentional and intentional) was the leading cause of death in persons aged 1-44 years. Further review of the data reveals that in those aged 15-25 years, 14,113 persons died from unintentional injuries, 73% of which were related to vehicular trauma. In individuals aged 25-34 years, 57% of the 11,769 deaths reported were from motor vehicle collisions. In 2001, approximately 30 million people visited emergency departments for the treatment of nonfatal injuries and more than 72,000 people were disabled by injuries. Injury imposes exceptional costs, both in health care dollars and in human losses, to society. International In 1990, approximately 5 million people died worldwide as a result of injury. The risk of death from injury varied strongly by region, age, and sex. Approximately 2 male deaths due to violence were reported for every female death. Injuries accounted for approximately 12.5% of all male deaths, compared with 7.4% of female deaths. Globally, injury accounts for 10% of all deaths; however, injuries in sub-Saharan Africa are far more destructive than in other areas. In sub-Saharan Africa, the risk of death from trauma is highest in those aged 15-60 years, and the proportion of such deaths from trauma is higher than in any other region of the world. In South Africa, for instance, the traffic death rate per unit of distance traveled is only surpassed by Korea, Kenya, and Morocco. Estimates indicate that by 2020, 8.4 million people will die yearly from injury, and injuries from traffic collisions will be the third most common cause of disability worldwide and the second most common cause in the developing world. Pathophysiology Vehicular trauma is by far the leading cause of blunt abdominal trauma in the civilian population. Auto-to-auto and auto-to-pedestrian collisions have been cited as causes in 50-75% of cases. Rare causes of blunt abdominal injuries include iatrogenic trauma during cardiopulmonary resuscitation, manual thrusts to clear an airway, and the Heimlich maneuver. Intra-abdominal injuries secondary to blunt force are attributed to collisions between the injured person and the external environment and to acceleration or deceleration forces acting on the person’s internal organs. Blunt force injuries to the abdomen can generally be explained by 3 mechanisms. The first is when rapid deceleration causes differential movement among adjacent structures. As a result, shear forces are created and cause hollow, solid, visceral organs and vascular pedicles to tear, especially at relatively fixed points of attachment. For example, the distal aorta is attached to the thoracic spine and decelerates much more quickly than the relatively mobile aortic arch. As a result, shear forces in the aorta may cause it to rupture. Similar situations can occur at the renal pedicles and at the cervicothoracic junction of the spinal cord. The second is when intra-abdominal contents are crushed between the anterior abdominal wall and the vertebral column or posterior thoracic cage. This produces a crushing effect, to which solid viscera (eg, spleen, liver, kidneys) are especially vulnerable. The third is external compression forces that result in a sudden and dramatic rise in intra-abdominal pressure and culminate in rupture of a hollow viscous organ (ie, in accordance with the principles of Boyle law). Presentation History The initial assessment of a trauma patient begins at the scene of the injury, with information provided by the patient, family, bystanders, or paramedics. Important factors relevant to the care of a patient with blunt abdominal trauma, specifically those involving motor vehicles, include the following: The extent of vehicular damage Whether prolonged extrication was required Whether the passenger space was intruded Whether a passenger died Whether the person was ejected from the vehicle The role of safety devices such as seat belts and airbags The presence of alcohol or drug use The presence of a head or spinal cord injury Whether psychiatric problems were evident Priorities in resuscitation and diagnosis are established based on hemodynamic stability and the degree of injury. The goal of the primary survey, as directed by the Advanced Trauma Life Support protocol, is to identify and expediently treat life-threatening injuries. The protocol includes the following: Airway, with cervical spine precautions Breathing Circulation Disability Exposure Key elements of the pertinent history include the following: Allergies Medications Past medical and surgical history Time of last meal Immunization status Events leading to the incident Social history, including history of substance abuse Information from family and friends Resuscitation is performed concomitantly and continues as the physical examination is completed. The secondary survey is the identification of all injuries via a head-to-toe examination. It is imperative for all personnel involved in the direct care of a trauma patient to exercise universal precautions against body fluid exposure. The incidence of infectious diseases (eg, HIV, hepatitis) is significantly higher in trauma patients than in the general public, with some centers reporting rates as high as 19%. Even in medical centers with relatively low rates of communicable diseases, safely determining who is infected with such pathogens is impossible. The standard barrier precautions include a hat, eye shield, face mask, gown, gloves, and shoe covers. Unannounced trauma arrival is probably the most common situation that leads to a breach in barrier precautions. Personnel must be instructed to adhere to these guidelines at all times, even if it means a 30-second delay in patient care. Physical examination The evaluation of a patient with blunt abdominal trauma must be accomplished with the entire patient in mind, with all injuries prioritized accordingly. This implies that injuries involving the head, the respiratory system, or the cardiovascular system may take precedence over an abdominal injury. The abdomen should neither be ignored nor the sole focus of the treating clinician and surgeon. In an unstable patient, the question of abdominal involvement must be expediently addressed. This is accomplished by identifying free intra-abdominal fluid using diagnostic peritoneal lavage (DPL) or the Focused Assessment with Sonography for Trauma (FAST) examination. The objective is to rapidly identify patients who need a laparotomy. The initial clinical assessment of patients with blunt abdominal trauma is often difficult and notably inaccurate. Associated injuries often cause tenderness and spasms in the abdominal wall and make diagnosis difficult. Lower rib fractures, pelvic fractures, and abdominal wall contusions may mimic the signs of peritonitis. In a collected series of 955 patients, Powell et al reported that clinical evaluation alone has an accuracy rate of only 65% for detecting the presence or absence of intraperitoneal blood.1 In general, accuracy increases if the patient is examined repeatedly and at frequent intervals. However, repeated examinations may not be feasible in patients who need general anesthesia and surgery for other injuries. The greatest compromise of the physical examination occurs in the setting of neurologic dysfunction, which may be caused by head injury or substance abuse. The most reliable signs and symptoms in alert patients are pain, tenderness, gastrointestinal hemorrhage, hypovolemia, and evidence of peritoneal irritation. However, large amounts of blood can accumulate in the peritoneal and pelvic cavities without any significant or early changes in the physical examination findings. The abdominal examination must be systematic. The abdomen is inspected for abrasions or ecchymosis. The seat belt sign, ie, a contusion or abrasion across the lower abdomen, is highly correlated with intraperitoneal pathology. Visual inspection for abdominal distention, which may be due to pneumoperitoneum, gastric dilatation, or ileus produced by peritoneal irritation, is important. Ecchymosis involving the flanks (Grey Turner sign) or the umbilicus (Cullen sign) indicates retroperitoneal hemorrhage, but this is usually delayed for several hours to days. Rib fractures involving the lower chest may be associated with splenic or liver injuries. Auscultation of bowel sounds in the thorax may indicate the presence of a diaphragmatic injury. Palpation may reveal local or generalized tenderness, guarding, rigidity, or rebound tenderness, which suggests peritoneal injury. A rectal examination should be performed to search for evidence of bony penetration resulting from a pelvic fracture, and the stool should be evaluated for gross or occult blood. The evaluation of rectal tone is important for determining the patient’s neurologic status, and palpation of a high-riding prostate suggests urethral injury. A nasogastric tube should be placed routinely (in the absence of contraindications, eg, basilar skull fracture) to decompress the stomach and to assess for the presence of blood. If the patient has evidence of a maxillofacial injury, an orogastric tube is preferred. As the assessment continues, a Foley catheter is placed and a sample of urine is sent for analysis for microscopic hematuria. If injury to the urethra or bladder is suggested because of an associated pelvic fracture, then a retrograde urethrogram is performed before catheterization. Because of the wide spectrum of injuries, frequent reevaluation is an essential component in the management of patients with blunt abdominal trauma. Pediatric patients are assessed and treated at least initially as adults with respect to the primary and secondary surveys. However, obvious anatomical and clinical differences exist and these must be kept in mind: the child’s physiologic response to injury is different; communication is not always possible; physical examination findings become more important; the pediatric patient’s blood volume is less, predisposing them to rapid exsanguination; technical procedures tend to be more time consuming and challenging; and a child’s relatively large body surface area contributes to rapid heat loss. Perhaps, the most significant difference between pediatric and adult blunt trauma is that, for the most part, pediatric patients can be resuscitated and treated nonoperatively. Some pediatric surgeons often transfuse up to 40 mL/kg of blood products in an effort to stabilize a pediatric patient. Obviously, if this fails and the child continues to be unstable, laparotomy is indicated. Tertiary examination This concept was first introduced by Enderson et al to assist in the diagnosis of any injuries that may have been missed during the primary and secondary surveys.2 The tertiary survey involves a repetition of the primary and secondary surveys and a revision of all laboratory and radiographic studies. In one study, a tertiary trauma survey detected 56% of injuries missed during the initial assessment within 24 hours of admission. Indications Aggressive radiographic and surgical investigation is indicated in patients with persistent hyperamylasemia or hyperlipasemia, conditions that suggest significant intra-abdominal injury. Stable patients with inconclusive physical examination findings should undergo radiographic studies of the abdomen. DPL is indicated in blunt trauma as follows: Patients with a spinal cord injury Those with multiple injuries and unexplained shock Obtunded patients with a possible abdominal injury Intoxicated patients in whom abdominal injury is suggested Patients with potential intra-abdominal injury who will undergo prolonged anesthesia for another procedure An indication for immediate blood transfusion is hemodynamic instability despite the administration of 2 L of fluid to adult patients; this instability indicates ongoing blood loss. Indications for laparotomy in a patient with blunt abdominal injury include the following: Signs of peritonitis Uncontrolled shock or hemorrhage Clinical deterioration during observation Hemoperitoneum findings after FAST or DPL examinations Finally, surgical intervention is indicated in patients with evidence of peritonitis based on physical examination findings. Relevant Anatomy The abdomen can be arbitrarily divided into 4 areas. The first is the intrathoracic abdomen, which is the portion of the upper abdomen that lies beneath the rib cage. Its contents include the diaphragm, liver, spleen, and stomach. The rib cage makes this area inaccessible for palpation and complete examination. The second is the pelvic abdomen, which is defined by the bony pelvis. Its contents include the urinary bladder, urethra, rectum, small intestine, and, in females, the ovaries, fallopian tubes, and uterus. Injury to these structures may be extraperitoneal in nature and therefore difficult to diagnose. The third is the retroperitoneal abdomen, which contains the kidneys, ureters, pancreas, aorta, and vena cava. Injuries to these structures are very difficult to diagnose based on physical examination findings. Evaluation of the structures in this region may require a CT scan, angiography, and an intravenous pyelogram. The fourth is the true abdomen, which contains the small and large intestines, the uterus (if gravid), and the bladder (when distended). Perforation of these organs is associated with significant physical findings and usually manifests with pain and tenderness from peritonitis. Plain x-ray films are helpful if free air is present. Additionally, DPL is a useful adjunct. Contraindications While not a contraindication to surgical repair, the evaluation of a patient with blunt abdominal trauma must be prioritized based on the most urgent problems. This implies that injuries involving the head, the respiratory system, or the cardiovascular system may take precedence over an abdominal injury. Although a nasogastric tube is routine in order to decompress the stomach and assess for the presence of blood, it is contraindicated in patients with basilar skull fracture. An orogastric tube is preferred if the patient has evidence of a maxillofacial injury. Operative treatment is not indicated in every patient with positive FAST scan results. Hemodynamically stable patients with positive FAST findings may require a CT scan to better define the nature and extent of their injuries. Operating on every patient with positive FAST scan findings may result in an unacceptably high laparotomy rate. The only absolute contraindication to DPL is the obvious need for laparotomy. Relative contraindications include morbid obesity, a history of multiple abdominal surgeries, and pregnancy. Resuscitative thoracotomy is not recommended in patients with blunt thoracoabdominal trauma who have pulseless electrical activity upon arrival in the emergency department. The survival rate in this situation is virtually 0%. These patients may be allowed a thoracotomy in the emergency department only if they have signs of life upon arrival to the emergency department.

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