Intrabdominal compartment syndrome

Question 1

What is normal intra-abdominal pressure?

Answer 1

5-7 mmHg

Question 2

What is intra-abdominal compartment syndrome?

Answer 2

World society for abdominal compartment syndrome definition:

• ACS is sustained IAP >20 mmHg with new organ dysfunction (APP should be >60 (APP= MAP - IAP))
• it may be primary (abdominal pathology) or secondary (extra-abdominal processes)
• Intra-abdominal hypertension is sustained IAP >12 mmHg:
• grade 1 (12-15)
• grade 2 (16-20)
• grade 3 (21-25)
• grade 4 (>26)

Question 3

What are the risk factors/causes of IAH?

Answer 3

1. Decreased abdominal wall compliance
   - tight primary closure post surgery
   - trauma/burns
   - prone positioning
2. Increased abdominal contents:
   - intraluminal (gastroparesis, pseudo-obstruction)
   - extraluminal (ascites - cirrhosis/pancreatitis/fluid resus/sepsis, haemo/pneumoperitoneum)
3. Mechanical ventilation

Question 4

How is IAP measured?

Answer 4

1. Direct measure - needle or catheter attached to manometer into peritoneal cavity.
2. Indirect (via urinary catheter)
   - ANTT
   - patient in supine position
   - bladder allowed to empty then drainage line clamped distal to transducer line
   - transducer attached in 3-way tap circuit at level of iliac crest and mid axilla line
   - 25ml sterile saline into bladder
   - allowed to settle for 60 secs and transducer zeroed to atmospheric pressure.
   - transducer opened to bladder and pressure measured (usually intermittently at 4-6 hourly intervals)

Question 5

What are the complications of intra-abdominal hypertension?

Answer 5

1. Respiratory:
   - basal atelectasis and reduced compliance
   - hypoxaemia and hypercapnia
2. Cardiovascular
   - impaired venous return (increased intrathoracic pressure and reduced abdominal venous return) reducing cardiac output
   - increased afterload
3. Neurological:
   - raised ICP (intraabdominal and thoracic pressure causing impaired cerebral venous blood flow)
   - hypoxaemia and hypercapnia worsening raised ICP
4. Renal:
   - reduced renal blood flow and filtration gradient
   - external compression of renal outflow
5. GI:
   - visceral ischaemia and oedema
   - impaired portal return
   - biliary stasis

Question 6

How can you manage raised abdominal pressure?

Answer 6

1. Medical management:
   - evacuate intraluminal contents
   - evacuate extraluminal contents
   - improve abdominal wall compliance
   - optimise fluid balance
   - optimise organ perfusion
2. Surgery if refractory to medical therapy
   - laparotomy +/- open abdomen
   - escharotomy