Abdominal compartment syndrome

Abdominal compartment syndrome (ACS) occurs when the abdomen becomes subject to increased pressure reaching past the point of intra-abdominal hypertension (IAH). ACS is present when intra-abdominal pressure rises and is sustained at > 20 mmHg and there is new organ dysfunction or failure.

Pathophysiology

• Abdominal compartment syndrome occurs when tissue fluid within the peritoneal and retroperitoneal space (either edema, retroperitoneal blood or free fluid in the abdomen) accumulates in such large volumes that the abdominal wall compliance threshold is crossed and the abdomen can no longer stretch.
• Once the abdominal wall can no longer expand, any further fluid leaking into the tissue results in fairly rapid rises in the pressure within the closed space.
• Initially this increase in pressure does not cause organ failure but does prevent organs from working properly – this is called intra-abdominal hypertension and is defined as a pressure over 12 mm Hg in adults.
• ACS is defined by a sustained IAP(intra-abdominal pressure) above 20 mm Hg with new-onset or progressive organ failure.

Cause

The underlying cause of the disease process is capillary permeability caused by the systemic inflammatory response syndrome (SIRS) that occurs in every critically ill patient. SIRS leads to leakage of fluid out of the capillary beds into the interstitial space in the entire body with a profound amount of this fluid leaking into the gut wall, mesentery and retroperitoneal tissue.

• Peritoneal tissue edema secondary to diffuse peritonitis, abdominal trauma
• Fluid therapy due to massive volume resuscitation
• Retroperitoneal hematoma secondary to trauma and aortic rupture
• Peritoneal trauma secondary to emergency abdominal operations
• Reperfusion injury following bowel ischemia due to any cause
• Retroperitoneal and mesenteric inflammatory edema secondary to acute pancreatitis
• Ileus and bowel obstruction
• Intra-abdominal masses of any cause
• Abdominal packing for control of bleeding
• Closure of the abdomen under undue tension
• Ascites (intra-abdominal fluid accumulation)
• Acute pancreatitis with abscesses formation

Clinical course

• Abdominal compartment syndrome follows a destructive pathway similar to compartment syndrome of the extremities.
• When increased compression occurs in such a hollow space, organs will begin to collapse under the pressure.
• As the pressure increases and reaches a point where the abdomen can no longer be distended it starts to affect the cardiovascular and pulmonary systems.
• When abdominal compartment syndrome reaches this point without surgery and help of a silo the patient will most likely die.
• There is a high mortality rate associated with abdominal compartment syndrome.

Diagnosis

• Abdominal compartment syndrome is defined as an intra-abdominal pressure above 20 mmHg with evidence of organ failure.
• Abdominal compartment syndrome develops when the intra-abdominal pressure rapidly reaches certain pathological values, within several hours (intra-abdominal hypertension is observed), and lasts for 6 or more hours.
• The key to recognizing abdominal compartment syndrome is the demonstration of elevated intra-abdominal pressure which is performed most often via the urinary bladder, and it is considered to be the "gold standard".
• Multiorgan failure includes damage to the cardiac, pulmonary, renal, neurological, gastrointestinal, abdominal wall, and ophthalmic systems.
• The gut is the most sensitive to intra-abdominal hypertension, and it develops evidence of end-organ damage before alterations are observed in other systems.

Treatment

Treatment algorithm for IAH/ ACS

Operative decompression

The mortality rate associated with abdominal compartment syndrome is significant, ranging between 60% and 70%. The poor outcome relates not only to abdominal compartment syndrome itself but also to concomitant injury and hemorrhagic shock.

• openabdomen.org
• wsacs.org