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ICU Protocol

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Intra-Abdominal Pressure

1. Definitions

Intra-Abdominal Pressure (IAP) is the measurement of the pressure inside the abdominal compartment.

Normal IAP is 5-7 mm Hg during critical illness.

Intra-abdominal Hypertension (IAH) is defined by pressure > 12 mm Hg.

Abdominal Compartment Syndrome (ACS) is defined as sustained pressures > 20 mm Hg with evidence of organ dysfunction.

Abdominal Perfusion Pressure (APP) should be > 60 mmHg and calculated as: APP= MAP – IAP. APP is dependent upon an adequate MAP and low IAP.

2. Intra-Abdominal Pressure Monitoring

IAP should be measured in any patient who may have elevated abdominal pressure (bleeding, trauma, obstruction, abdominal surgery) and are in risk of IAH and ACS.

It can be measured directly by inserting a catheter into the abdominal compartment, or indirectly, by monitoring the pressure in the bladder from an indwelling Foley catheter.

Measurement of urinary bladder pressure is the standard method to screen for IAH and ACS.

3. Method for Abdominal pressure monitoring

Wash hands and follow universal antiseptic precautions.

An assembly is made with a set of pressure tubing with transducer and arterial line extension, normal saline, Kelly clamp, 50 ml luer-lock syringe, urinary drainage bag with a sampling port close to the catheter connection as shown in Figure 1.

Fill the syringe with saline and infuse 25 mL of saline in to the bladder.

Calibrate the transducer to zero at the level of midaxillary line (level of pubic symphysis) by opening stop cock to air.

IAP is measured 30–60 s after instillation at end-expiration in the supine position with head of bed flat in the absence of active muscles contraction.

If pressure is elevated in initial screening deep sedation may be considered to rule-out false positive due to abdominal wall resistance.

Report an IAP reading greater than 12mm Hg to the on-duty doctor.

Disconnect pressure tubing and place a sterile end-cap on the sampling port and unclamp the foley catheter.

Figure 1: Intrabdominal Pressure Monitoring Set

4. Management of Intra-abdominal Hypertension and Abdominal Compartment Syndrome

Position patient to lower intra-abdominal pressures (avoid head of bed > 30 degrees).

Reduce abdominal wall tension (deep sedation, add neuromuscular blockers if inadequate).

Reduce intra-luminal gastrointestinal contents (nasogastric decompression, laxatives, prokinetic agents, minimize enteral nutrition, rectal decompression).

Evacuation of intra-abdominal contents (percutaneous drainage of ascites, surgical decompression).

Optimize fluid balance (avoid positive cumulative fluid balance, diuretics, renal replacement therapy).

Maintain an adequate abdominal perfusion pressure>60 mm Hg (use vasopressors if needed).

Consider surgical decompression for refractory IAH>30 mm Hg and deteriorating organ function.

Further Readings:

1. Kirkpatrick, A. W., Roberts, D. J., De Waele, J., Jaeschke, R., Malbrain, M. L., De Keulenaer, B., ... & Pediatric Guidelines Sub-Committee for the World Society of the Abdominal Compartment Syndrome. (2013). Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive care medicine, 39, 1190-1206.

2. Milanesi, R., & Caregnato, R. C. A. (2016). Intra-abdominal pressure: an integrative review. Einstein (Sao Paulo), 14, 423-430.

3. Cheatham, M. L., Malbrain, M. L., Kirkpatrick, A., Sugrue, M., Parr, M., De Waele, J., ... & Wilmer, A. (2007). Results from the international conference of experts on intra-abdominal hypertension and abdominal compartment syndrome. II. Recommendations. Intensive care medicine, 33, 951-962.

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