Abdominal Compartment Syndrome

OVERVIEW

Definitions (from Kirkpatrick et al, 2013)

• Intra-abdominal pressure (IAP) is the steady state pressure concealed within the abdominal cavity
• Intra-abdominal Hypertension (IAH) is sustained intra-abdominal pressure (IAP) of > 12mmHg
• Abdominal Compartment Syndrome (ACS) is sustained IAP > 20mmHg with new organ failure
• Abdominal Perfusion Pressure (APP) = MAP – IAP
• A polycompartment syndrome is a condition where two or more anatomical compartments have elevated compartmental pressures
• Abdominal compliance is a measure of the ease of abdominal expansion, which is determined by the elasticity of the abdominal wall and diaphragm. It should be expressed as the change in intra-abdominal volume per change in IAP

Types of ACS

• Primary ACS — injury or disease causing ACS (typically requires early surgical/radiological intervention)
• Secondary ACS — ACS due not due to primary condition
• Recurrent ACS — ACS develops after previous surgical or medical treatment of ACS

Grade of IAH (severity)

• Normal = IAP 5-7 mmHg
• Grade I = IAP 12–15 mmHg
• Grade II = IAP 16–20 mmHg
• Grade III = IAP 21–25 mmHg
• Grade IV = IAP >25 mmHg

Differences in children

• IAP in critically ill children is approximately 4–10 mmHg
• IAH in children is defined by a sustained or repeated pathological elevation in IAP > 10 mmHg
• ACS in children is defined as a sustained elevation in IAP of greater than 10 mmHg associated with new or worsening organ dysfunction that can be attributed to elevated IAP
• The reference standard for intermittent IAP measurement in children is via the bladder using 1 mL/kg as an instillation volume, with a minimal instillation volume of 3 mL and a maximum installation volume of 25 mL of sterile saline

RISK FACTORS

Diminished Abdominal Wall Compliance

• acute respiratory failure (especially with elevated intrathoracic pressure)
• abdominal surgery with fascial closure
• major trauma/burns
• prone positioning
• head > 30 degrees
• high BMI
• central obesity

Increased Intra-luminal Contents

• gastroparesis
• ileus
• colonic pseudo-obstruction

Increased Abdominal Contents

• haemo/pneumoperitoneum
• ascites
• liver dysfunction

Capillary Leak or Fluid Resuscitation

• acidosis (pH < 7.2)
• hypotension
• hypothermia (T < 33 C)
• massive transfusion (> 10 U in 24 hrs)
• coagulopathy
• massive fluid resuscitation
• pancreatitis
• sepsis
• oliguria
• damage control laparotomy

CONSEQUENCES

Gastrointestinal

• direct compression
• thrombosis
  -> bowel wall ischaemia + oedema
  -> translocation of bacterial products leading to additional accumulation

Renal

• direct compression of renal parenchyma and ischaemia
  -> AKI

Respiratory

• reduced compliance
• elevated airway pressures
• decreased TV

Neurological

• increased ICP
• decompressive laparotomy has been shown to reduced intractable intra-cranial hypertension in patients with intra-abdominal hypertension

Cardiovascular

• elevated CVP and PCWP
• however, decreased VR
  -> decreased cardiac output

INVESTIGATIONS

Imaging

• AXR: useless!
• CT: only subtle findings
  -> increased AP diameter, collapse of vena cava, bowel wall thickening, bilateral inguinal herniation
• Ultrasound: AAA

Gold standard is measurement of intra-vesical pressure (see IAP monitor)

MEDICAL MANAGEMENT

Monitor

• measure IAP when patient has 2 or more risk factors or in the presence of new or progressive organ failure

Improve Abdominal Wall Compliance

• sedation & analgesia
• avoid head elevation > 30 degrees
• remove constrictive dressing
• eschars
• neuromuscular blockade

Evacuate Intra-Luminal Contents

• nasogastric decompression
• rectal decompression
• prokinetics
• minimise enteral nutrition
• enemas

Evacuate Abdominal Fluid Collections

• paracentesis
• percutaneous drainage
• surgical evacuation

Correct Positive Fluid Balance

• avoid excessive fluid
• aim for zero to negative balance
• diuretics
• colloids/hypertonic fluids
• haemodialysis/filtration

Organ Support

• maintain a APP > 60mmHg with vasopressors
• optimise ventilation: use transmural airway pressure (Pplattm = Pplat – IAP)
• if using CVP use transmural pressure (CVPtm = CVP – 0.5 x IAP)

SURGICAL MANAGEMENT

• if IAP 25-35 and not responding to medical treatment
  -> decompression with delayed closure (laparostomy)
• on release be aware of hypotension
  -> PEA arrest from reperfusion and a sudden decrease in SVR

References and Links

LITFL

• CCC —  IAP monitor

Journal articles

• Kirkpatrick AW, et al. Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Med (2013) 39:1190–1206 [Free Full Text]

FOAM and web resources

• CCC — IAP monitor
• World Society of the Abdominal Compartment Syndrome