emDOCs Podcast – Episode 71: Abdominal Compartment Syndrome

Today on the emDOCs cast with Brit Long, MD (@long_brit), we discuss abdominal compartment syndrome, a challenging diagnosis in the ED.

Episode 71: Abdominal Compartment Syndrome

• Intraabdominal hypertension is an increased pressure in the abdomen, but there’s no end organ injury.
  • Up to 1/2 of patients admitted to the medical ICU have IAH.
• Normal abdominal compartment pressure is 2-5 mm Hg; this is higher in critically ill patients, obese patients, and pregnancy.
• ACS is defined by IAP > 20 mm Hg with organ dysfunction.
• Four underlying causes contribute: decreased abdominal wall compliance, increased intraluminal contents, increased abdominal contents, or capillary leak/fluid resuscitation.
• 3 different types of ACS:
  • Primary is due to some issue in the abdomen itself.
  • Secondary ACS is due to a condition outside of the abdomen.
  • Recurrent ACS occurs again after a prior episode of primary or secondary ACS.
• ACS is best thought of as polycompartment syndrome.
  • GI: The increased pressure directly compresses the bowel, that can reduce blood flow and cause bowel wall edema. This ultimately results in mesenteric ischemia and bacterial translocation into the blood stream.
  • Renal:The pressure directly compresses the kidneys and reduces the blood flow; AKI is one of the first findings in ACS.
  • Liver injury
  • Pulmonary: As the pressure builds, its transduced upwards, which results in increased intrathoracic pressures. The increased pressure reduces movement of the diaphragm; it doesn’t allow the lungs to fully expand. Reduces compliance, results in hypoxemia and hypercapnia.
  • Cardiac: Direct cardiac compression, reduced venous return and cardiac output, increased peripheral vascular resistance.
  • Intracranial: Decrease in cerebral venous outflow, disruption in the blood-brain barrier, increased the ICP.

• History and physical examination may suggest the diagnosis, but they should not be used to exclude ACS.
  • Reduced urinary output, abdominal pain and distension, shortness of breath, refractory hypotension.
  • If intubated, increased pressure alarms, trouble with ventilation
  • Think about ACS in the patient with a risk factor like a high volume resuscitation, or if they have refractory hypotension, they have worsening Cr, or if they’re intubated, you’re having issues with ventilation and high pressure alarms
• Labs and imaging can assist in diagnosis (look for end organ injury).
  • Elevated Cr, decreased GFR, elevated LFTs and lactate.
  • Diaphragm elevation, effusions, lobar collapse on Chest X-ray
  • Direct organ compression, narrowing of the blood vessels, collapsed IVC, elevated diaphragm, thickened abdominal wall, and free air on CT
  • Round belly sign (RBS) = increased ratio of anteroposterior to transverse diameter; 0.80 is concerning
  • Peritoneal-to-abdominal height ratio (PAR) = ratio between the anteroposterior peritoneal compartment diameter (distance from linea alba to posterior part of duodenum) and then you compare that to the anteroposterior abdomen diameter (distance from linea alba to posterior fascia) measured along the midline; 0.52 is concerning
• The gold standard for diagnosis is intra-abdominal pressure measurement, typically through a Foley catheter.

• Pearls: Use warm sterile saline; wait 30 seconds after infusing to check pressures; ensure adequate pain control/sedation
• Pressures are increased in obese patients, or in patients who have had pelvic or bladder radiation.
• Contraindications: traumatic bladder injury, pelvic packing, and  cystectomy.
• Management
  • Optimize abdominal perfusion pressure (MAP – abdominal compartment pressure); target MAP is 60 + abdominal compartment pressure
  • Target intravascular euvolemia and remove excess volume if possible
  • Decompress the abdominal cavity, both intraluminal and extraluminal contents
  • Decompress the thoracic cavity if needed
  • Provide appropriate analgesia and sedation; paralysis may be needed
  • Final component of treatment is surgical decompression with fascial release. This is usually reserved for those who fail these other measures. Best if performed within 4 days of diagnosis

References:

Abdominal Compartment Syndrome: Pearls & Pitfalls