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What is it?
It is the measurement of the pressure inside the abdominal compartment.
How can it be done?
It can be measured directly by inserting a catheter into the abdominal compartment, or indirectly, by monitoring the pressure in the bladder, stomach or other cavities.
All patients who are edematous, critically ill or who have abdomonal distension for any reason are at risk. ARDS, intraabdominal disorders and inflammatory states are important risk factors.
Why is it done?
The pressure inside the abdominal compartment can increase following trauma, as a result of the accumulation of blood, fluid or edema. Non-traumatic bowel ischemia/infarction or gastrointestinal hemorrhage can also lead to increased pressure in the abdominal compartment as ischemic cells swell or fluids collect. Coagulopathies with abdominal bleeding, cirrhosis, or profound hypothermia are other potential causes. Once the pressure in the abdominal compartment overcomes the pressure inside the capillaries that are responsible for perfusing the organs, ischemia and infarction of organs can occur.
Abdominal compartment pressure monitoring is done to help recognize life threatening elevations in pressure before ischemia or infarction of the abdominal organs occurs. When a patient exhibits a distended and taut abdomen, the measurement of abdominal compartment pressure can provide direction regarding the need for decompressive surgery.
What values are important?
Normal intra-abdominal pressure is 0 - 5 mmHg. Pressures > 13 mmHg may be sufficient to restrict perfusion to the organs of the gut.
abdominal compartment pressures is between 16-25 mmHg, hypervolemic volume
expansion therapy can be used to maintain the perfusion pressure gradient
for the abdominal organs.
When compartment pressures exceed 25 mmHg, General Surgery should be consulted for consideration of decompression to prevent organ damage.
Pressure may rise rapidly with active bleeding. Edema (which occurs with any ischemic insult) will generally result in a later rise in the pressure (27 hours or more post insult).
What findings are clinically significant?
Patients with abdominal compartment syndrome should be monitored for the following:
Oliguria due to renal ischemia
Increased airway resistance/reduced tidal volumes/hypoxemia/hypercarbia due to restriction of the diaphragm
Hypotension and decreased cardiac output as a result of decreased venous return and/or volume loss into the abdominal compartment
Gastrointestinal bleeding/blood diarrhea/rising lactate due to ischemia of the bowel
Impaired distal extremity circulation secondary to pressure on the aorta
The most common findings of abdominal compartment syndrome are renal and cardiopulmonary complications. In head injury, increased abdominal compartment pressure can increase ICP.
Bladder pressure is measured as a surrogate of intra-abdominal pressure. Intra-abdominal pressure will be transmitted to the bladder, and will generally correlate well with intra-abdominal pressures. The pressure trend can also provide information regarding the clinical progression.
Some patients may experience gut ischemia prior to elevation of the compartment pressure. It is also possible that bladder pressure may not capture an elevation of the abdominal compartment pressure if there is a loculated area. While abdominal compartment pressure monitoring via the bladder may provide valuable information regarding patients with abdominal hypertension, abdominal compartment syndrome should not be ruled out in the presence of a normal pressures if persistent clinical findings exist.
How can I measure pressure quickly?
compartment syndrome pressure can be measured very quickly, by hooking
a pressure monitoring system up to the luer lock connection of the drainage collecting tubing. Measurement via the drainage tubing sampling port (versus catheter) allows measurements from any catheter that is connected to continuous drainage.
The pressure monitoring circuit can be left connected to avoid opening of a closed circuit. Intermittent connection is often preferred to facility patient care/turning.
If the circuit is intermittently connected for pressure monitoring, it is important to ensure aseptic technique is maintained. The sampling port should be covered with an alcohol-based cap (like IV connections) and the ends of any tubing/syringes are kept sterile.
Prior to measuring pressure, the bladder should be empty. A volume of 25 ml of saline should be instilled into the empty bladder to allow pressure to facilitate pressure wave transmission while maintaining a constant bladder volume with each measurement.
All pressures should be taken with the patient lying supine, head flat and transducer level confirmed. Each measurement should be taken at end expiration.
|Figure 1: Set up showing syringe connected to stopcock on pressure tubing. End of pressure tubing is connected to luer lock sampling port on drainage tubing.|
1. Follow the 4 Moments of Hand Hygiene.
2. Prime the pressure circuit with the normal saline (the flush solution does not require heparin or pressurization) and connect the syringe to the stopcock as shown in the Figure 1.
3. Position the head of bed flat. This relaxes the abdominal wall to decrease any muscular influence on the bladder pressure.
4. Level the transducer with the bladder. This should be the mid-axillary line when the bed is flat.
5. Prior to measuring bladder pressure, the catheter remains open to continuous drainage, therefore, the bladder should be empty.
6. Clamp the drainage bag firmly as shown in the diagram (be sure it is fully clamped or the pressure will be falsely low).
7. Fill the bladder with 25 ml of normal saline using the 60 cc syringe. Turn the stopcock to the syringe to the "off" position after the saline is instilled. This ensures that the volume of fluid in the bladder is constant with each measurement, but not enough to influence pressure. Some fluid is required to transmit the pressure to the transducer.
8. Obtain the pressure measurement. The abdominal blood flow should produce fluctuations in the waveform with the heart beat. Should the waveform (displayed in a small scale) fail to produce fluctuations, flush the line and transducer (troubleshoot as you would any dampened waveform).
9. Unclamped the drainage catheter and discard the 25 ml. Do not include the first 25 ml as output.
10. If the circuit is disonnected, ensure that the pressure tubing end is protected by a sterile connection and place a new alcohol based cap on the luer lock sampling port.
11. Document the pressure in the graphic record and report readings greater than 12 mmHg to the physician. Repeat q4-6 h and monitor trend until no longer required.
12. Continue to monitor for signs of abdominal compartment pressure elevation (e.g., dereased urine output, hypotension, low cardiac ouput, increased airway resistance or impaired ventilation, increased lactate or creatinine).
Clinical Educator, CCTC
Revised: May 8, 2008, March 24, 2017
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