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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 edema and/or fluid collects. 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.
Measuring Abdominal Compartment Pressure
When a patient exhibits a distended, taut abdomen, the measurement of abdominal compartment pressure can provide direction regarding the need for decompressive surgery.
Normal intra-abdominal pressure is 0 - 5 mmHg. Pressures > 13 mmHg may be sufficient to restrict perfusion to the organs of the gut. If the abdominal compartment pressures isbetween 16-25 mmHg, hypervolemic volume expansion therapy can be used to maintain the perfusion pressure gradient for the abdominal organs. When compartment pressuresexceed 25 mmHg, decompression surgery should be considered 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).
Patients with abdominal compartment syndrome should be monitored for oliguria due to renal ischemia, increased peak airway pressures/reduced tidal volumes/hypoxemia/hypercarbia due to a compromised diaphragm, hypotension and decreased cardiac output as a result of decreased venous return and/or volume loss into the abdominal compartment, gastrointestinal bleeding due to ischemia of the bowel, and 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 significantly increase ICP.
One quick and simple way to assess intra-abdominal pressure is to use an existing Foley catheter to monitor bladder pressure. Intra-abdominal pressure will be transmitted to the bladder, and will generally correlate well to intra-abdominal pressures. The pressure trend can also provide information regarding the clinical progression.
A few words of caution....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 pressure persistent clinical findings exist.
The following procedure describes a technique for measuring bladder pressure as a reflection of intra-abdominal compartment pressure. Other techniques that can also be used, for example, abdominal compartment pressure can also be measured through a peritoneal catheter or gastric catheter. Multiple site monitoring may be useful if the clinical findings suggest that the patient is worse than indicated by a single site pressure.
In addition to pressure monitoring, gastric mucosal pH monitoring (tonometry) can be used to assess for evidence of gastric ischemia. This may provide an earlier indication of gut ischemia than compartment pressure monitoring alone.
Abdominal compartment syndrome pressure can be measured very quickly, by hooking a pressure monitoring system up to the Foley catheter.
Ideally, a 3 - way Foley catheter is desirable. This allows pressure to be monitored via the irrigation limb. Use of the irrigation limb avoids the need to repeatedly access a closed system and reduces the risk for needle stick injuries. When initially choosing a catheter for a patient at risk for abdominal compartment syndrome, consider inserting a 3 - way catheter to facilitate future monitoring, should it become necessary.
Alternatively, if a 2-way catheter is already insitu connect the pressure tubing into the luer lok of the rubber sampling port of the urinary drainage bag.
plus diagrams of the set-up for both 2-way and 3-way Foley catheters are
1. Perform hand hygiene and don non-sterile gloves. Prime the pressure circuit with the normal saline (the flush solution does not require heparin or pressurization)
2. Connect the pressure tubing (leave the arterial line extension with stopcock in place) to the Foley as follows:
4. Fill the bladder with 25 cc of normal saline using the 60 cc syringe. This ensures that the volume of fluid in the bladder is constant for each measurement. Fluid is required to transmit the pressure to the transducer.
5. Ensure that the transducer is level with the bladder (which should be approximately mid axillary line).
6. Close the stopcock off to the syringe, and obtain the mean pressure reading. 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 as you would to troubleshoot dampening of any pressure waveform.
pressure q 2 - 4 hours and document findings on patient's flowsheet.
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Ivatury, R., et al. (1998). Intra-abdominal hypertension after life-threatening penetrating abdominal trauma: prophylaxis, incidence, and clinical relevance to gastric mucosal pH and abdominal compartment syndrome. Journal of Trauma: Injury, Infection and Critical Care. Jun; 44(6): 1016-23.
Offner, P. & Burch, J. (1998). Abdominal compartment syndrome, part 1: presentation and workup: cardiopulmonary and renal findings are among the most prominent signs. Journal of Critical Illness. Oct; 13(10): 634-8.
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