Abdominal Compartment Syndrome

Abdominal compartment syndrome (ACS) is defined as a sustained intra-abdominal pressure (IAP) > 20 mmHg that is associated with new organ dysfunction. However, organ dysfunction can occur with pressures as low as 10 mmHg. Risk for ACS is increased in pediatrics, trauma, liver transplantation, abdominal conditions such as rapidly accumulating ascites, retroperitoneal conditions such as ruptured abdominal aortic aneurysm or pelvic fracture, following rapid massive volume resuscitation, patients with circumferential abdominal burns, and burn patients receiving > 6 ml/kg/% total body surface area of the burn.

Because patients with ACS are often critically ill and intubated, symptoms can be difficult to recognize. In addition to a tense distended abdomen, patients often have progressive oliguria and increased ventilator requirements. Other indicators include hypotension, tachycardia, jugular venous distension, acute respiratory failure, restlessness, altered mental status, and new lactic acidosis. Imaging is often not helpful in the diagnosis of ACS.

Clinically, IAP can be measured in the bladder lumen using a Foley catheter. A transducer is attached to a stopcock at the point where the catheter connects to the drainage system. The transducer is zeroed at the level of the midaxillary line, the drain is clamped, and 20-25 ml of sterile saline is instilled into the bladder. Intra-luminal pressure is measured at the end of expiration (near FRC) with the patient in the supine position to promote abdominal muscle relaxation. Keep in mind that this measurement is less accurate in patients with chronically increased IAP due to morbid obesity or pregnancy.

Management of ACS consists of supportive care and surgical decompression. Supportive measures aimed to decreased IAP include maintaining a negative fluid balance, avoiding head of bed elevation, therapeutic paracentesis if ascites is present, and paralysis/PEEP in ventilated patients. Surgical decompression is indicated in all patients with intra-abdominal pressures > 25 mmHg. Another measure used to determine the need for surgery is abdominal perfusion pressure (APP). APP= MAP-IAP. An APP < 50 mmHg is more sensitive and specific for predicting mortality than IAP alone. If surgical decompression is needed in a burn patient, anesthetic implications include an increased risk of intra-abdominal Pseudomonas infections.