Abdominal Compartment Syndrome 

Although compartment syndrome is well recognized to occur in the extremities, it also occurs in the abdomen and, some believe, in the intracranial cavity. Compartment syndrome occurs when a fixed compartment, defined by myofascial elements or bone, becomes subject to increased pressure, leading to ischemia and organ dysfunction.

The exact clinical conditions that define abdominal compartment syndrome (ACS) are controversial; however, organ dysfunction caused by intra-abdominal hypertension (IAH) is considered to be abdominal compartment syndrome. The dysfunction may be respiratory insufficiency secondary to compromised tidal volumes, decreased urine output caused by falling renal perfusion, or any organ dysfunction caused by increased abdominal compartment pressure.

Abdominal compartment syndrome was recognized clinically in the 19th century when Marey and Burt observed its association with declines in respiratory function. In the early 20th century, Emerson's animal experiments demonstrated mortality associated with abdominal compartment syndrome. Initially, cardiorespiratory compromise was thought to be the cause; however, renal failure was hypothesized by Wendt and was later studied by Thorington and Schmidt.

More recently, Kron and Iberti developed a simple method of accurately measuring intra-abdominal pressure. This has led to a better understanding of the relationship between IAH and abdominal compartment syndrome.

Three categories

As the diagnosis of abdominal compartment syndrome became easier to establish, it was observed to occur as a consequence of a variety of primary clinical events. Abdominal compartment syndrome can be divided into the following 3 categories:

• Primary or acute abdominal compartment syndrome occurs when intra-abdominal pathology is directly and proximally responsible for the compartment syndrome
• Secondary abdominal compartment syndrome occurs when no visible intra-abdominal injury is present but injuries outside the abdomen cause fluid accumulation
• Chronic abdominal compartment syndrome occurs in the presence of cirrhosis and ascites or related disease states, often in the later stages of the disease

In the ED and ICU

In the emergency department and intensive care unit, abdominal compartment syndrome is recognized with growing frequency as the cause of morbidity such as metabolic acidosis, decreased urine output, and decreased cardiac output. The cause of these events might easily be mistaken for other pathologic events such as hypovolemia if the clinician is not alert to the morbidity associated with abdominal compartment syndrome.

Therapy should include fluid resuscitation and transfusion if needed. Pharmacologic therapy is less effective than mechanical drainage. Paracentesis may be a superior alternative to decompressive laparotomy in this patient population. (See Treatment and Medication.)

For patient education information, see the Circulatory Problems Center; Esophagus, Stomach, and Intestine Center; and Liver, Gallbladder, and Pancreas Center, as well as Aortic Aneurysm, Abdominal Pain in Adults, Pancreatitis, Chronic Kidney Disease, Sepsis (Blood Infection), and Cirrhosis.

Organ dysfunction with abdominal compartment syndrome is a product of the effects of IAH on multiple organ systems. Abdominal compartment syndrome follows a destructive pathway similar to compartment syndrome of the extremity.

Problems begin at the organ level with direct compression; hollow systems such as the intestinal tract and portal-caval system collapse under high pressure. Immediate effects such as thrombosis or bowel wall edema are followed by translocation of bacterial products, leading to additional fluid accumulation, which further increases intra-abdominal pressure.

At the cellular level, oxygen delivery is impaired, leading to ischemia and anaerobic metabolism. Vasoactive substances such as histamine and serotonin increase endothelial permeability; further capillary leakage impairs red cell transport; and ischemia worsens.

Simon et al demonstrated a significantly lowered threshold for injury from IAH in pigs after hemorrhage and fluid resuscitation.^[1] Oxygen delivery may play an important role.

Although the abdominal cavity (ie, the peritoneal and, to a lesser extent, retroperitoneal cavities) is much more distensible than an extremity, it reaches an endpoint at which the pressure rises dramatically. This is less apparent in chronic cases because the fascia and skin slowly stretch and thus tolerate greater fluid accumulation.

As pressure rises, abdominal compartment syndrome impairs not only visceral organs but also the cardiovascular and the pulmonary systems; it may also cause a decrease in cerebral perfusion pressure. Therefore, abdominal compartment syndrome should be recognized as a possible cause of decompensation in any critically injured patient.

Abdominal compartment syndrome occurs when the IAP is too high, similar to compartment syndrome in an extremity. The 3 types of abdominal compartment syndrome (primary, secondary, and chronic) have different and sometimes overlapping causes.

Primary ACS

Causes of primary (ie, acute) abdominal compartment syndrome include the following:

• Penetrating trauma
• Intraperitoneal hemorrhage
• Pancreatitis
• External compressing forces, such as debris from a motor vehicle collision or after a large structure explosion
• Pelvic fracture
• Rupture of abdominal aortic aneurysm
• Perforated peptic ulcer

Secondary ACS

Secondary abdominal compartment syndrome may occur in patients without an intra-abdominal injury, when fluid accumulates in volumes sufficient to cause IAH. Causes include the following:

• Large-volume resuscitation: The literature shows significantly increased risk with infusions greater than 3 L
• Large areas of full-thickness burns: Hobson et al demonstrated abdominal compartment syndrome within 24 hours in burn patients who had received an average of 237 mL/kg over a 12-hour period.^[2]
• Penetrating or blunt trauma without identifiable injury
• Postoperative
• Packing and primary fascial closure, which increases incidence
• Sepsis

Chronic

Causes of chronic abdominal compartment syndrome include the following:

• Peritoneal dialysis
• Morbid obesity
• Cirrhosis
• Meigs syndrome
• Intra-abdominal mass

According to recent literature, the frequency of abdominal compartment syndrome in trauma ICU admissions is anywhere from 5-15% and 1% of general trauma admissions. Much of the recent literature on abdominal compartment syndrome has originated from outside the United States, where frequency and morbidity appear to be the same.

Racial, sexual, and age-related differences in incidence

Nothing has been published indicating a racial or sexual difference in the incidence or mortality of abdominal compartment syndrome.

Abdominal compartment syndrome has been documented in all age groups. The IAP that leads to morbidity (>25 mm Hg) appears to be similar in the pediatric population.

If left untreated, abdominal compartment syndrome is almost uniformly fatal. Eddy and colleagues documented a mortality of 68% for patients with documented abdominal compartment syndrome seen from 1984-1996.^[3] Most of the population was male (70%), and most had experienced blunt trauma (80%). In the subsequent literature, mortality rates have ranged from 25-75%.

The high mortality in abdominal compartment syndrome, even with treatment, reflects the fact that the condition affects multiple organ systems. Furthermore, abdominal compartment syndrome is often a sequela to severe injuries that independently carry a high morbidity and high mortality. Malbrain et al demonstrated that by itself, elevation of abdominal pressure correlates with increased mortality before the actual development of abdominal compartment syndrome.^[4]