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Objective: Elevated intra-abdominal pressure (IAP) is a frequent cause of morbidity and mortality among the critically ill. IAP is most commonly measured using the intravesicular or "bladder" technique. The impact of changes in body position on the accuracy of IAP measurements, such as head of bed elevation to reduce the risk of ventilator-associated pneumonia, remains unclear., Design: Prospective, cohort study., Setting: Twelve international intensive care units., Patients: One hundred thirty-two critically ill medical and surgical patients at risk for intra-abdominal hypertension and abdominal compartment syndrome., Interventions: Triplicate intravesicular pressure measurements were performed at least 4 hours apart with the patient in the supine, 15 degrees , and 30 degrees head of bed elevated positions. The zero reference point was the mid-axillary line at the iliac crest., Measurements and Main Results: Mean IAP values at each head of bed position were significantly different (p < 0.0001). The bias between IAPsupine and IAP15 degrees was 1.5 mm Hg (1.3-1.7). The bias between IAPsupine and IAP30 degrees was 3.7 mm Hg (3.4-4.0)., Conclusions: Head of bed elevation results in clinically significant increases in measured IAP. Consistent body positioning from one IAP measurement to the next is necessary to allow consistent trending of IAP for accurate clinical decision making. Studies that involve IAP measurements should describe the patient's body position so that these values may be properly interpreted.

Objective: To investigate the effect of different reference transducer positions on intra-abdominal pressure (IAP) measurement. Three reference levels were studied: the symphysis pubis; the phlebostatic axis; and the midaxillary line at the level of the iliac crest., Design: Prospective cohort study., Setting: The intensive care units of participating hospitals, Patients and Participants: One hundred thirty-two critically ill patients at risk for intra-abdominal hypertension (IAH)., Interventions: In each patient, three sets of IAP measurements were obtained in the supine position, using the different reference levels. The IAP measurements obtained at the different reference levels were compared using a paired t-test and Bland-Altman statistics were calculated., Measurements and Results: IAP(phlebostatic) (9.9 +/- 4.67 mmHg) and IAP(pubis) (8.4 +/- 4.60 mmHg) were significantly lower that IAP(midax) (12.2 +/- 4.66 mmHg; p < 0.0001 for both comparisons). The bias between the IAP(midax) and IAP(pubis) was 3.8 mmHg (95% CI 3.5-4.1) and 2.3 mmHg (95% CI 1.9-2.6) between the IAP(midax) and the IAP(phlebostatic). The precision was 3.03 and 3.40, respectively., Conclusions: In the supine position, IAP(midax) is higher than both IAP(phlebostatic) and IAP(pubis), differences found to be clinically significant; therefore, the symphysis pubis or phlebostatic axis reference lines are not interchangeable with the midaxillary level.

Background: Raised intra-abdominal pressure (IAP) or intra-abdominal hypertension (IAH) may induce many adverse effects including the abdominal compartment syndrome. We evaluated a new technique for continuous monitoring of intra-abdominal pressure (CIAP) using a standard three-way bladder catheter in a diverse group of intensive care unit patients., Methods: CIAP measured using a standard three-way bladder catheter was compared with five standard intermittent IAP (IIAP) measurements in 79 patients., Results: Mean (standard deviation) CIAP was identical (15.4 mm Hg [5.8]) for CIAP and IIAP one minute after saline injection. Mean differences between methods were less than 1 mm Hg, and similar whether IIAP was measured at 1 minute, 2 minutes, 3 minutes, 4 minutes, or 5 minutes. Bland-Altman analysis comparing CIAP and IIAP (1 minute) revealed a mean difference (95% confidence interval) of -0.06 mm Hg (-0.51, 0.39). Limits of agreement were -4.12 mm Hg to 4.00 mm Hg. Considering gradations of IAH defined by the World Society of the Abdominal Compartment Syndrome, CIAP was sensitive for detecting slightly elevated IAP (>11 mm Hg) but is less sensitive for distinguishing between higher grades of IAH (e.g., pressures >20 mm Hg or 25 mm Hg). Limits of agreement were best for patients with IAP less than 20 mm Hg, surgical or traumatic diagnoses and for patients with BMI less than 26., Conclusions: Overall, CIAP is an accurate and simple means of measuring IAP when compared with the current standardized method. Elevated CIAP measurements should be confirmed with IIAP measurements if accurate grading is required until further validation and experience is obtained.

Background: Intra-abdominal hypertension (IAH) is increasingly recognized as an important parameter in critically ill (ICU) patients. IAH affects perfusion to all abdominal components including the abdominal wall (AW). Near infrared spectroscopy (NIRS) measures changes in three chromophores including oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), and cytochrome aa3 (Cyt), providing information concerning dysoxia. We sought to examine whether NIRS measurement of the AW was safe, and correlated with intra-abdominal pressure (IAP) in ICU patients., Methods: A NIU-Pro001 system recorded NIRS data over 24 hours from the AW of 9 ICU patients at risk for IAH. IAP was recorded from the bladder. Changes in chromophore values are interpolated from best-fit polynomial curves., Results: Sixty-six paired IAP and NIRS readings were taken from 9 ICU (4-12 observations/patient) patients. No measurement related adverse reactions occurred. The mean (range) first values measured in these patients were; IAP 17.2 mm Hg (9-31); HbO2 0.41 micromol/L (-8.4 to 7.6); Hb 2.6 micromol/L (-3.1 to 12.2); and Cyt 0.65 micromol/L (-3.4 to 4.8). A significant, inverse (or negative) association was found between DeltaNIRS HbO2 level and DeltaIAP (coefficient, -0.1588; p = 0.008). No association was found between DeltaNIRS Hb or DeltaCyt and DeltaIAP., Conclusion: NIRS of the AW appears safe. NIRS measurement of changes in HbO2 appears to be associated with DeltaIAP, and warrant further study in greater numbers of ICU patients with more frequent IAP readings, over longer periods of critical illness.

Introduction: The Secondary Abdominal Compartment Syndrome (SACS) refers to cases of the ACS that do not originate from the abdomino-pelvic region. With greater awareness of the physiologic consequences of raised intra-abdominal hypertension (IAH), cases of the SACS are being increasingly described. The prior treatment or the presence of a partially open abdomen does not preclude the ACS if the abdomen and viscera continue to swell or the clinician is not vigilant in monitoring intra-abdominal pressure (lAP). Such recurrent cases (RACS) have been defined as those which redevelop following the previous medical or surgical treatment of primary or SACS. Although there has been a diverse range of etiologies implicated, these cases seem to be linked by the common occurrence of severe shock requiring aggressive fluid resuscitation. The aim of this paper is to thus to review the historical background, awareness, definitions, pathophysiological implications and treatment options for SACS and RACS., Methods: This review will focus on the available literature regarding SACS and RACS. A Medline and Pubmed search was performed using the keywords; secondary abdominal compartment syndrome AND secondary AND tertiary AND recurrent AND abdominal compartment syndrome AND intra-abdominal pressureAND intra-abdominal hypertension. Bibliographies of recovered papers were hand-searched for other appropriate references. The resulting references were included in the current review on the basis of relevance and scientific merit, Results: There has been remarkably little specific study of these entities outside of specific groups such as those injured by thermal or traumatic injury. The epidemiology, risk factors for, treatment of and most importantly, strategies for prevention all remain scientifically unknown and therefore based on opinion. Notable, although small, studies suggest that specific resuscitation practices may avert these conditions., Conclusions: ACS can occur in any patient who is critically ill and subject to visceral and somatic swelling, regardless of whether the inciting pathology is extra-abdominal. The ACS may also reoccur with recurrent shock and swelling even if previous therapies had partially addressed IAH. Therefore IAP measurements should be considered a routine monitoring for the critically ill, especially those subjected to shock and requiring a subsequent resuscitation. Much further study is required to understand the differences in etiology, diagnosis, pathophysiology, and treatment for all cases of the ACS.