Table 1 Definitions of IAH, IAH grades and ACS

Intra-abdominal Hypertension (IAH)

Sustained intra-abdominal pressure (IAP) ≥ 12 mmHg^a

IAH grade I

IAP 12–15 mmHg^a

IAH grade II

IAP 16–20 mmHg^a

IAH grade III

IAP 21–25 mmHg^a

IAH grade IV

IAP > 25 mmHg^a

IAH at admission

First and second IAP measurements after admission were ≥ 12 mmHg

Abdominal Compartment Syndrome (ACS)

Sustained IAP > 20 mmHg associated with new organ dysfunction or failure^a