IAH is common in the intensive care unit and depending on case mix can affect up to 50% of patients, with ACS affecting up to 8%. IAH can be graded on the basis of intra-abdominal pressures (IAP):
● Grade I: 12-15 mmHg
● Grade II: 16-20 mmHg
● Grade III: 21-25 mmHg
● Grade IV: >25 mmHg
Measurement of IAP may be performed either directly or indirectly. Direct pressure measurement occurs via a peritoneal transducer, while indirect measurement (most commonly used) involves transduction of a urinary catheter, zeroed at the intersection of the iliac crest in the mid-axillary line. The patient should be supine, without muscle contractions for an accurate measurement1.
