Abdominal Compartment Syndrome (ACS)

Question 1

What is intraabdominal hypertension (IAH)?

Answer 1

Intra-abdominal hypertension (IAH) is defined by a sustained or repeated pathologic elevation of IAP >= 12 mmHg.

Grading:
• Grade I : 12 – 15 mmHg
• Grade II : 16 – 20 mmHg
• Grade III : 21 – 25 mmHg
• Grade IV : > 25 mmHg

Question 2

What is abdominal compartment syndrome (ACS) ?

Answer 2

Abdominal compartment syndrome (ACS) is defined as a sustained IAP > 20 mmHg recorded by a minimum of 3 standardized measurement conducted 1-6hours apart or an APP < 60 mmHg with immediate new onset organ dysfunction/failure.

Question 3

What is Abdominal perfusion pressure (APP)?

Answer 3

APP = mean arterial pressure (MAP) – IAP.
Normal > 60 mmHg.

Question 4

What are the causes of ACS?

Answer 4

1) Primary ACS:
- Associated with injury or disease in the abdomino- pelvic region that requires surgical or radiological intervention
( Abdominal trauma , pancreatitis , post laparotomy)

2) Secondary ACS:
- conditions that do not originate from the abdomino-pelvic region
( Excessive fluid resuscitation, sepsis , burns)

3) Recurrent ACS:
- Condition in which ACS redevelops following previous surgical or medical treatment of primary or secondary ACS

Question 5

What are the Pathophysiological of ACS?

Answer 5

can be divided into:
- CVS
-Pulmonary
- Renal
-GIT
-CNS
- (local) - Abdominal wall

Question 6

What are the Pathophysiological (CVS) in ACS?

Answer 6

• CVS
  • Diaphragm splinting → cardiac compression → ↓ CO
  • IAH → IVC compression → ↓VR
  • IAH → splinting → ↑ ITP → ↑ CVP & PCWP
  • ↓CO → neuro-humoral stimulation → ↑ SVR

Question 7

What is the pathophysiology (Pulmonary) for ACS?

Answer 7

• Pulmonary
  • IAH → ↑ITP → hypoxia, hypercarbia, atelectasis
  • In ventilated patients → ↑ PEEP, MAP → barotraum
• Elevated diaphragm increased intra-thoracic pressure lead to restriction of lung expansion.
• Alveoli and lung vessels compressed, lung segment collapse causing V/Q mismatch, with increased intra-pulmonary shunting & dead space.

Question 8

What is the pathophysiology (Renal) for ACS?

Answer 8

• Renal
  • ↓ CO → ↑ RAAS & sympathetic → vasocontrict → ↓ renal blood flow
  • Renal vein compression → ↑ VR → ↓ venous drainage

Raised IAP causing decreased in renal blood flow & GFR (from cardiovascular effect), direct compression on renal parenchyma & decreased renal outflow secondary to increased renal vein pressure.

Question 9

What is the pathophysiology (GIT) of ACS?

Answer 9

• GIT
  • IAP > 40 → ↓ SMA, celiac, IMA blood flow
  • IAP > 20 → intestinal mucosal ischemia & oedema.

Question 10

What is pathophysiology (CNS) of ACS?

Answer 10

• CNS
  • ↑ CVP → ↑ ICP → ↓ CPP
• Postulated mechanism: raised CVP causing decreased cerebral venous outflow resulting in an increased in intracranial vascular volume.

Question 11

What is the pathophysiology( local - abdominal wall) of ACS?

Answer 11

• Abdominal wall
  • ↑ radius → ↑ tension (P = 2T/r) → ↓ compliance & ↓ rectus blood flow.

Question 12

How can Intraabdominal pressure be measured?

Answer 12

1) Indirect
* Intravesical measurement (most common)
* Intragastric
* Intracolonic
* IVC catheters

2) Direct
* intra-abdominal probe

Bladder pressure measurement: ( most common)
* Clamp Foley’s catheter
* Instill 25 ml sterile saline into bladder via aspiration port.
* 18G needle attached to pressure transducer is inserted into aspiration port.
* Zero transducer at mid-axillary line level.
* Measure pressure in supine position, end expiration, after 30s.

Question 13

How to manage IAH/ ACS?

Answer 13

1) Evacuate intraluminal contents:
- RT or rectal tube decompression
-Prokinetic agents
-Minimize enteral feeding
-Administer enemas
-Consider colonoscopic decompression if feasible

2) improve abdominal wall compliance:
- Ensure adequate sedation and analgesia
-Remove constrictive dressings ( such as abdominal eschars)
-Avoid prone position ( head of bed > 20 degrees)
-Consider reverse Trendelenberg position
- Neuromuscular bloackade

3) Optimize fluid administration
- Avoid excessive fluid resuscitation
- Aim for zero to negative fluid balance for 3 days
- Resuscitate using hypertonic fluids, colloid
- Diuretic agents if needed
- Consider hemodialysis/ ultrafiltration if needed

4) Optimize systemic / regional perfusion
- Maintain abdominal perfussion pressure 60mmhg and more ( by using vasoactive medication)
- optimize ventilation

5) Evacuate abdominal fluid collections:
- Percutaneous drainage
- Abdominal paracentesis

If IAP > 25 mmHg ( and /or APP < 50mmHg) and new organ dysfunction/ failure is present or IAH/ACS is refractory to medical management
- for surgical andominal decompression