What is the recommended IAP (Intra-Abdominal Pressure) regimen?

IAP Monitoring and Management Regimen

Measure IAP at least every 4-6 hours (or continuously) in all critically ill patients with risk factors for intra-abdominal hypertension, using the intravesicular technique with the patient supine at end-expiration, and immediately initiate stepwise medical management when IAP ≥12 mmHg to maintain IAP <15 mmHg. 1

Key Definitions and Thresholds

• Normal IAP: ≤12 mmHg 1, 2
• Intra-abdominal Hypertension (IAH): Two consecutive IAP measurements >12 mmHg within 4-6 hours 1, 2
• Abdominal Compartment Syndrome (ACS): IAP >20 mmHg with new organ dysfunction/failure 1, 3

IAP Measurement Technique

Use intravesicular (bladder) pressure measurement as the gold standard, with the following standardized approach 1, 4:

• Instill maximum 25 mL sterile normal saline into the bladder 5
• Position patient completely supine (flat) 1, 4
• Measure at end-expiration 1, 4
• Ensure abdominal muscle relaxation (no active contraction) 4
• Zero the transducer at the mid-axillary line where it crosses the iliac crest 4
• Mark this zero reference point on the patient to improve reproducibility 4

Common pitfall: Do not rely on clinical examination (abdominal girth or palpation of abdominal tenseness)—this has only 40% sensitivity and is grossly inaccurate 6.

Monitoring Frequency Algorithm

For patients with IAH (IAP ≥12 mmHg): 1

• Measure IAP every 4-6 hours minimum, or continuously if available 1, 2
• Continue measurements throughout the critical illness period 1

Once IAH resolves (IAP <12 mmHg): 1

• Discontinue routine IAP measurements 1
• Monitor patient clinically for deterioration 1

Stepwise Medical Management Algorithm

When IAP ≥12 mmHg, implement interventions sequentially until IAP decreases to <15 mmHg 1, 3:

Step 1: Evacuate Intraluminal Contents

• Insert nasogastric tube and rectal tube 1, 3
• Initiate gastro-colonic prokinetic agents 1
• Administer enemas for colonic decompression 1, 3
• Consider neostigmine for established colonic ileus unresponsive to other measures 3

Step 2: Improve Abdominal Wall Compliance

• Ensure adequate sedation and analgesia 1, 3
• Consider brief trial of neuromuscular blockade as temporizing measure 3
• Adjust body position to minimize IAP 3
• Remove constrictive dressings or abdominal eschars 1

Step 3: Evacuate Intra-abdominal Occupying Lesions

• Perform abdominal ultrasound to identify fluid collections or lesions 1, 3
• Percutaneous catheter drainage (PCD) when technically feasible 3

Step 4: Optimize Fluid Administration

• Avoid excessive fluid resuscitation 1
• Aim for zero to negative fluid balance after initial resuscitation completed 1, 3
• Consider judicious diuresis once hemodynamically stable 1, 3
• Consider ultrafiltration/hemodialysis in appropriate patients 3

Step 5: Optimize Systemic/Regional Perfusion

• Goal-directed fluid resuscitation 1
• Consider hypertonic fluids or colloids for resuscitation 1

Critical note: The World Society of the Abdominal Compartment Syndrome made no recommendation regarding use of diuretics, renal replacement therapy, or albumin specifically for IAH management after acute resuscitation, so these should be used based on overall clinical context 1.

Surgical Intervention Threshold

Proceed immediately to decompressive laparotomy when: 1, 3

• IAP ≥20 mmHg with new organ dysfunction/failure (ACS diagnosis) 1, 3
• Medical management fails to reduce IAP below 20 mmHg 3

Special consideration for trauma patients: Consider prophylactic open abdomen in patients with physiologic exhaustion undergoing laparotomy 1, 3

Special Population: Acute Pancreatitis

In severe acute pancreatitis with IAP <15 mmHg: 1

• Initiate early enteral nutrition via nasojejunal (preferred) or nasogastric tube 1
• Monitor IAP and clinical condition continuously during enteral feeding 1

Contraindication: Abdominal compartment syndrome is an absolute contraindication to enteral nutrition 1

Critical Pitfalls to Avoid

• Never wait for late signs of ACS (these indicate irreversible organ damage has occurred) 3, 7
• Never measure IAP with patient in elevated position or with active abdominal muscle contraction (falsely elevates readings) 1, 4
• Never use excessive instillation volumes in the bladder (>25 mL falsely elevates IAP) 5
• Never ignore IAP trends in patients receiving massive fluid resuscitation—overresuscitation is a major contributor to IAH development 3
• Never delay surgical decompression once ACS is diagnosed and medical management fails—mortality remains 50% even with intervention 3

Abdominal Perfusion Pressure Consideration

While abdominal perfusion pressure (APP = MAP - IAP) has been proposed as an analogue to cerebral perfusion pressure and may predict visceral perfusion better than IAP or MAP alone, the World Society of the Abdominal Compartment Syndrome made no recommendation regarding its routine use in resuscitation or management 1, 8. Use APP monitoring only in specialized circumstances with appropriate expertise.