Abdominal compartment syndrome

Learning objectives

Difference between intra-abdominal pressure (IAP) and abdominal compartment syndrome (ACS)
Recognize ACS and the pathophysiological consequences of ACS
Management of ACS

Normal intra-abdominal pressure (IAP) ranges between 0-5 mmHg while in critically-ill patients, an IAP of 5-7 mmHg is considered normal
Intra-abdominal hypertension is defined as a sustained intra-abdominal pressure (IAP) ≥12 mmHg
Abdominal compartment syndrome (ACS) is defined as IAP rises > 20 mmHg thereby leading to new organ dysfunction
Abdominal perfusion pressure (APP) is calculated as the mean arterial pressure (MAP) minus the IAP
A critically ill patient with high mortality & morbidity

Acute ACS

Primary: due to injury or disease in the abdominopelvic region (e.g., pancreatitis, abdominal trauma)
Secondary: does not originate in the abdomen or pelvis (e.g., fluid resuscitation, sepsis, burns)

Chronic ACS

Artificially raised IAP

External compression, for example, prolonged prone positioning for spinal surgery with insufficient provision for abdominal movement

Diminished abdominal wall compliance	Acute respiratory failure, especially with elevated intrathoracic pressure Abdominal surgery with subjectively tight primary closure Major trauma/burns Prone positioning, head of bed elevated > 30° High BMI, central obesity
Increased intra-luminal contents	Gastroparesis Ileus Colonic pseudo-obstruction
Increased abdominal contents	Hemoperitoneum/pneumoperitoneum Ascites/liver dysfunction
Capillary leak/fluid resuscitation	Metabolic acidosis ( pH < 7.2) Hypotension Perioperative hypothermia Polytransfusion (>10 units of blood/24 h) Coagulopathy (platelets < 55 000 mm-3, prothrombin time > 15 s, partial thromboplastin time > 2 times normal, or international standardized ratio >1.5) Massive fluid resuscitation (> 5 litre/24 h) Pancreatitis Oliguria Sepsis Trauma Burns Damage control laparotomy

Central nervous system	Increased intra-cranial pressure
Cardiovascular system	Increased systemic vascular resistance Pulmonary vascular resistance Decreased venous return with concomitant venous congestion
Gastrointestinal and hepatic system	Decreased coeliac, mesenteric, hepatic and hepatic portal blood flow Increased oedema, bacterial translocation and liver dysfunction
Renal system	Increased renal tubular pressure and urinary obstruction Decreased renal blood flow and urine output
Respiratory system	Increased ventilation-perfusion mismatch, ventilatory pressure, basal atelectasis and PaCO2 Decreased chest wall and pulmonary compliance and PaO2

Indirect measurement of IAP using intragastric, intracolonic, intravesical (bladder), or inferior vena cava catheters

Patients with two or more risk factors should have IAP monitoring
Treatment:
- Regimens lowering IAP
- Open the abdominal wound and perform a temporary closure of the abdominal wall with mesh or a plastic bag (Bogota bag)
- Regiments aiming at organ support
Keep abdominal perfusion pressure (APP) (systemic blood pressure – intra-abdominal pressure) > 60mmHg

Consequences of decompression:
- Sudden ↓ cardiac output & SVR
- Reperfusion: risk of systemic acidosis & hyperkalemia
- Possible fatal arrhythmia & arrest
- Sudden change in respiratory compliance (avoid overventilation)
Avoid bradycardia (preload is compromised & CO may be heart rate dependent)
Maintain high preload particularly once decompressed