Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome
Executive Summary
The 2013 updated consensus from the World Society of the Abdominal Compartment Syndrome (WSACS) establishes standardized definitions and clinical practice guidelines for Intra-abdominal Hypertension (IAH) and Abdominal Compartment Syndrome (ACS). The primary objective of these guidelines is to facilitate early detection through protocolized Intra-abdominal Pressure (IAP) monitoring and to provide a tiered management approach to prevent the progression of IAH to overt ACS.
Critical takeaways include:
Standardized Measurement: The trans-bladder technique remains the reference standard for IAP measurement, with a recommended instillation volume of 25 mL of sterile saline.
Thresholds: IAH is defined as a sustained IAP ≥ 12 mmHg in adults and > 10 mmHg in children. ACS is defined as IAP > 20 mmHg (adults) or > 10 mmHg (children) associated with new or worsening organ dysfunction.
Mandatory Monitoring: IAP measurement is recommended for any critically ill patient presenting with known risk factors.
Management Hierarchy: Management involves medical therapies (sedation, fluid management, enteral decompression), minimally invasive options (percutaneous drainage), and definitive surgical intervention (decompressive laparotomy) for overt ACS.
The Open Abdomen: For patients with open abdominal wounds, the use of Negative Pressure Wound Therapy (NPWT) is recommended to facilitate early fascial closure.
1. Consensus Definitions and Classifications
The WSACS has refined the terminology to ensure clinical consistency across adult and pediatric populations.
1.1 Adult Definitions
1.2 IAH Grading
IAH is categorized by severity to guide intervention:
Grade I: IAP 12–15 mmHg
Grade II: IAP 16–20 mmHg
Grade III: IAP 21–25 mmHg
Grade IV: IAP > 25 mmHg
1.3 Pathological Classifications
Primary IAH/ACS: Associated with injury or disease in the abdominopelvic region (e.g., trauma, abdominal surgery).
Secondary IAH/ACS: Conditions originating outside the abdominopelvic region (e.g., massive fluid resuscitation, sepsis).
Recurrent IAH/ACS: Redevelopment of the condition following previous medical or surgical treatment.
Polycompartment Syndrome: Elevated pressures in two or more anatomical compartments.
2. Risk Factors and Diagnosis
Clinical examination is insufficient and inaccurate for detecting raised IAP; therefore, identifying risk factors is essential for triggering objective monitoring.
2.1 Major Risk Factors
Diminished Abdominal Wall Compliance: Major trauma, burns, abdominal surgery, prone positioning, or mechanical ventilation.
Increased Intraluminal Contents: Gastroparesis, ileus, or colonic pseudo-obstruction.
Increased Abdominal Contents: Hemoperitoneum, ascites, acute pancreatitis, or intra-abdominal tumors.
Capillary Leak & Fluid Resuscitation: Acidosis, hypothermia, massive fluid resuscitation (positive fluid balance), and sepsis.
2.2 Diagnostic Standards
The WSACS recommends:
Measurement Technique: Intermittent IAP should be measured via the bladder.
Standardization: Use a maximum instillation volume of 25 mL of sterile saline.
Positioning: Measure at end-expiration in the supine position, ensuring no abdominal muscle contractions are present. The transducer should be zeroed at the midaxillary line.
3. Clinical Management Guidelines
Management is divided into strong Recommendations (clear benefit) and weaker Suggestions (limited evidence but potential benefit).
3.1 Strong Management Recommendations (GRADE 1)
IAP Monitoring: Measure IAP when any known risk factor is present [1C].
Protocolized Care: Use protocolized monitoring and management of IAP [1C].
Prevention: Implement efforts to avoid sustained IAH [1C].
Surgical Decompression: Perform decompressive laparotomy for overt ACS in adults [1D].
Fascial Closure: Pursue early or same-hospital-stay abdominal fascial closure for patients with an open abdomen [1D].
Wound Therapy: Utilize Negative Pressure Wound Therapy (NPWT) for open abdominal wounds [1C].
3.2 Management Suggestions (GRADE 2)
Analgesia/Sedation: Ensure optimal pain and anxiety relief [2D].
Neuromuscular Blockade: Use brief trials as a temporizing measure to reduce abdominal muscle tone [2D].
Body Positioning: Consider the contribution of head-of-bed elevation to IAP; however, avoid positions that exacerbate pressure [2D].
Gastrointestinal Decompression: Use nasogastric or rectal tubes to remove intraluminal air/contents [1D]. Use neostigmine for colonic ileus non-responsive to simple measures [2D].
Fluid Management: Avoid a positive cumulative fluid balance after initial resuscitation [2C]. Use enhanced plasma-to-RBC ratios for massive hemorrhage [2D].
Percutaneous Catheter Drainage (PCD): Use PCD to remove obvious intraperitoneal fluid to alleviate IAH or avoid laparotomy [2C/2D].
3.3 Areas with No Recommendation
Due to insufficient evidence, the WSACS could not make recommendations regarding:
Using APP as a primary resuscitation endpoint.
The use of diuretics, renal replacement therapy, or albumin to mobilize fluid specifically for IAH management.
Prophylactic open abdomen in non-trauma surgery.
The use of acute component-parts separation or biologic meshes for early closure.
4. The Open Abdomen
The "Open Abdomen" is defined as a condition requiring temporary closure because the skin and fascia are not closed after laparotomy.
4.1 Classification Scheme for Complexity
To facilitate comparison and outcomes, the WSACS proposed an updated classification system:
Grade 1: No fixation (1A: Clean; 1B: Contaminated; 1C: Enteric leak).
Grade 2: Developing fixation (2A: Clean; 2B: Contaminated; 2C: Enteric leak).
Grade 3: Frozen abdomen (3A: Clean; 3B: Contaminated).
Grade 4: Established enteroatmospheric fistula (EAF) with a frozen abdomen.
4.2 Definitive Closure
The WSACS suggests avoiding the routine use of bioprosthetic meshes for early closure of the open abdomen. The primary focus should be on medial fascial traction and preventing visceral adherence to achieve primary fascial closure before hospital discharge.
5. Pediatric-Specific Guidelines
The Pediatric Guidelines Sub-Committee adapted adult definitions to reflect pediatric physiology.
While many adult management strategies were accepted for children (e.g., PCD, decompressive laparotomy for overt ACS), the committee could not recommend enhanced plasma ratios or specific same-stay closure protocols for pediatric care.
6. Conclusion and Future Research
While IAH and ACS are common and linked to poor outcomes, the overall quality of evidence remains low. The WSACS highlights a critical need for:
Defining "normal" IAP values in specific populations such as the obese and pregnant.
Determining the role of IAH (without overt ACS) in gut ischemia and neurological dysfunction.
Design of robust intervention trials to refine management protocols.
The 2013 guidelines emphasize that these recommendations should serve as a framework for institutional care but must not be used to censure clinical judgment at the bedside.
