Incidence, Risk Factors, and Outcomes of Intra-Abdominal Hypertension in Critically Ill Patients-A Prospective Multicenter Study (IROI Study).

OBJECTIVES: To identify the prevalence, risk factors, and outcomes of intra-abdominal hypertension in a mixed multicenter ICU population. DESIGN: Prospective observational study. SETTING: Fifteen ICUs worldwide. PATIENTS: Consecutive adult ICU patients with a bladder catheter. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Four hundred ninety-one patients were included. Intra-abdominal pressure was measured a minimum of every 8 hours. Subjects with a mean intra-abdominal pressure equal to or greater than 12 mm Hg were defined as having intra-abdominal hypertension. Intra-abdominal hypertension was present in 34.0% of the patients on the day of ICU admission (159/467) and in 48.9% of the patients (240/491) during the observation period. The severity of intra-abdominal hypertension was as follows: grade I, 47.5%; grade II, 36.6%; grade III, 11.7%; and grade IV, 4.2%. The severity of intra-abdominal hypertension during the first 2 weeks of the ICU stay was identified as an independent predictor of 28- and 90-day mortality, whereas the presence of intra-abdominal hypertension on the day of ICU admission did not predict mortality. Body mass index, Acute Physiology and Chronic Health Evaluation II score greater than or equal to 18, presence of abdominal distension, absence of bowel sounds, and positive end-expiratory pressure greater than or equal to 7 cm H2O were independently associated with the development of intra-abdominal hypertension at any time during the observation period. In subjects without intra-abdominal hypertension on day 1, body mass index combined with daily positive fluid balance and positive end-expiratory pressure greater than or equal to 7 cm H2O (as documented on the day before intra-abdominal hypertension occurred) were associated with the development of intra-abdominal hypertension during the first week in the ICU. CONCLUSIONS: In our mixed ICU patient cohort, intra-abdominal hypertension occurred in almost half of all subjects and was twice as prevalent in mechanically ventilated patients as in spontaneously breathing patients. Presence and severity of intra-abdominal hypertension during the observation period significantly and independently increased 28- and 90-day mortality. Five admission day variables were independently associated with the presence or development of intra-abdominal hypertension. Positive fluid balance was associated with the development of intra-abdominal hypertension after day 1.

Continuous veno-venous hemofiltration to adjust fluid volume excess in septic shock patients reduces intra-abdominal pressure.

OBJECTIVE: To analyze the effect and the time course of continuous veno-venous hemofiltration (CVVH) with net ultrafiltration (UF) on intra-abdominal pressure (IAP) body fluid volumes in septic shock patients with acute kidney injury (AKI). METHODS: Patients were studied at baseline and after 6, 12, 24, 48, 72, and 96 hours of CVVH treatment. IAP was measured via the bladder, and abdominal perfusion pressure (APP) was calculated as mean arterial pressure minus IAP. Fluid volume excess (VE), total body water (TBW), extracellular body water (ECW), and intracellular body water (ICW) were derived from wholebody bioimpedance analysis (BIA). RESULTS: 30 patients entered final analysis, of which 6 died during CVVH (non-survivors). Fluid VE, TBW, ECW, ICW, and IAP significantly decreased in 24 survivors, whereas these variables remained essentially unchangedin non-survivors. APP slowly increased in survivors, while it did not change in nonsurvivors. IAP strongly correlated with VEin survivors: The lower the IAP, the lower the fluid volume excess. CONCLUSION: CVVH with net UF successfully reduced IAP, TBW, ECW, and ICW in critically ill patients who survived 96 h of CVVH. Failure to increase APP was associated with fatal outcome, and, finally, IAP correlated with fluid volume excess. BIA could be helpful to monitor fluid status in patients with AKI.

Matching positive end-expiratory pressure to intra-abdominal pressure prevents end-expiratory lung volume decline in a pig model of intra-abdominal hypertension.

OBJECTIVE: Intra-abdominal hypertension is common in critically ill patients and is associated with increased morbidity and mortality. In a previous experimental study, positive end-expiratory pressures of up to 15 cm H2O did not prevent end-expiratory lung volume decline caused by intra-abdominal hypertension. Therefore, we examined the effect of matching positive end-expiratory pressure to the intra-abdominal pressure on cardio-respiratory parameters. DESIGN: Experimental pig model of intra-abdominal hypertension. SETTING: Large animal facility, University of Western Australia. SUBJECTS: Nine anesthetized, nonparalyzed, and ventilated pigs (48 ± 7 kg). INTERVENTIONS: Four levels of intra-abdominal pressure (baseline, 12, 18, and 22 mm Hg) were generated in a randomized order by inflating an intra-abdominal balloon. At each level of intra-abdominal pressure, three levels of positive end-expiratory pressure were randomly applied with varying degrees of matching the corresponding intra-abdominal pressure: baseline positive end-expiratory pressure (= 5 cm H2O), moderate positive end-expiratory pressure (= half intra-abdominal pressure in cm H2O + 5 cm H2O), and high positive end-expiratory pressure (= intra-abdominal pressure in cm H2O). MEASUREMENTS: We measured end-expiratory lung volume, arterial oxygen levels, respiratory mechanics, and cardiac output 5 mins after each new intra-abdominal pressure and positive end-expiratory pressure setting. MAIN RESULTS: Intra-abdominal hypertension decreased end-expiratory lung volume and PaO2 (-49% [p < .001] and -8% [p < .05], respectively, at 22 mm Hg intra-abdominal pressure compared with baseline intra-abdominal pressure) but did not change cardiac output (p = .5). At each level of intra-abdominal pressure, moderate positive end-expiratory pressure increased end-expiratory lung volume (+119% [p < .001] at 22 mm Hg intra-abdominal pressure compared with 5 cm H2O positive end-expiratory pressure) while minimally decreasing cardiac output (-8%, p < .05). High positive end-expiratory pressure further increased end-expiratory lung volume (+233% [p < .001] at 22 mm Hg intra-abdominal pressure compared with 5 cm H2O positive end-expiratory pressure) but led to a greater decrease in cardiac output (-26%, p < .05). Neither moderate nor high positive end-expiratory pressure improved PaO2 (p = .7). Intra-abdominal hypertension decreased end-expiratory transpulmonary pressure but did not alter end-inspiratory transpulmonary pressure. Intra-abdominal hypertension decreased total respiratory compliance through a decrease in chest wall compliance. Positive end-expiratory pressure decreased the respiratory compliance by reducing lung compliance. CONCLUSIONS: In a pig model of intra-abdominal hypertension, positive end-expiratory pressure matched to intra-abdominal pressure led to a preservation of end-expiratory lung volume, but did not improve arterial oxygen tension and caused a reduction in cardiac output. Therefore, we do not recommend routine application of positive end-expiratory pressure matched to intra-abdominal pressure to prevent intra-abdominal pressure-induced end-expiratory lung volume decline in healthy lungs.

Matching positive end-expiratory pressure to intra-abdominal pressure improves oxygenation in a porcine sick lung model of intra-abdominal hypertension.

INTRODUCTION: Intra-abdominal hypertension (IAH) causes atelectasis, reduces lung volumes and increases respiratory system elastance. Positive end-expiratory pressure (PEEP) in the setting of IAH and healthy lungs improves lung volumes but not oxygenation. However, critically ill patients with IAH often suffer from acute lung injury (ALI). This study, therefore, examined the respiratory and cardiac effects of positive end-expiratory pressure in an animal model of IAH, with sick lungs. METHODS: Nine pigs were anesthetized and ventilated (48 +/- 6 kg). Lung injury was induced with oleic acid. Three levels of intra-abdominal pressure (baseline, 18, and 22 mmHg) were randomly generated. At each level of intra-abdominal pressure, three levels of PEEP were randomly applied: baseline (5 cmH2O), moderate (0.5 × intra-abdominal pressure), and high (1.0 × intra-abdominal pressure). We measured end-expiratory lung volumes, arterial oxygen levels, respiratory mechanics, and cardiac output 10 minutes after each new IAP and PEEP setting. RESULTS: At baseline PEEP, IAH (22 mmHg) decreased oxygen levels (-55%, P <0.001) and end-expiratory lung volumes (-45%, P = 0.007). At IAP of 22 mmHg, moderate and high PEEP increased oxygen levels (+60%, P = 0.04 and +162%, P <0.001) and end-expiratory lung volume (+44%, P = 0.02 and +279%, P <0.001) and high PEEP reduced cardiac output (-30%, P = 0.04). Shunt and dead-space fraction inversely correlated with oxygen levels and end-expiratory lung volumes. In the presence of IAH, lung, chest wall and respiratory system elastance increased. Subsequently, PEEP decreased respiratory system elastance by decreasing chest wall elastance. CONCLUSIONS: In a porcine sick lung model of IAH, PEEP matched to intra-abdominal pressure led to increased lung volumes and oxygenation and decreased chest wall elastance shunt and dead-space fraction. High PEEP decreased cardiac output. The study shows that lung injury influences the effects of IAH and PEEP on oxygenation and respiratory mechanics. Our findings support the application of PEEP in the setting of acute lung injury and IAH.

The effect of non-invasive ventilation on intra-abdominal pressure.

BACKGROUND: Non-invasive ventilation is a well-established treatment modality in patients with respiratory failure of different aetiologies. A previous case report described how non-invasive ventilation caused gastric distension and intra-abdominal hypertension with subsequent cardio-respiratory arrest and clinical recovery following resuscitative efforts including gastric decompression with a nasogastric tube. METHODS: The aim of this prospective multicentre observational study was to assess the effect of non-invasive ventilation on intra-abdominal pressure. Following informed consent, intra-abdominal pressure and PaCO2 were measured before and after the application of non-invasive ventilation for up to three days in critically ill patients requiring non-invasive ventilation. RESULTS: Thirty-five patients were enrolled; mean (±SD) age of 67.8 (±12.5) years, median (interquartile range) body mass index of 27.9 (24.5-30.0) kg m-2, Acute Physiology and Chronic Health Evaluation II score of 15.8 (±6.4). On admission and after 24 hours of non-invasive ventilation, intra-abdominal pressure was 11.0 (7.5-15.0) mm Hg and 11.0 (8.5-14.5) mm Hg (P = 0.82) and PaCO2 was 44.4 (±11.4) mm Hg and 51.3 (±14.3) mm Hg (P = 0.19), respectively. CONCLUSIONS: The application of non-invasive ventilation was not associated with an increase in intra-abdominal pressure over 72 hours in this small observational study. Thus, it appears that intra-abdominal pressure does not frequently increase when applying non-invasive ventilation in critically ill patients with respiratory failure.

Fluid Management, Intra-Abdominal Hypertension and the Abdominal Compartment Syndrome: A Narrative Review.

BACKGROUND: General pathophysiological mechanisms regarding associations between fluid administration and intra-abdominal hypertension (IAH) are evident, but specific effects of type, amount, and timing of fluids are less clear. OBJECTIVES: This review aims to summarize current knowledge on associations between fluid administration and intra-abdominal pressure (IAP) and fluid management in patients at risk of intra-abdominal hypertension and abdominal compartment syndrome (ACS). METHODS: We performed a structured literature search from 1950 until May 2021 to identify evidence of associations between fluid management and intra-abdominal pressure not limited to any specific study or patient population. Findings were summarized based on the following information: general concepts of fluid management, physiology of fluid movement in patients with intra-abdominal hypertension, and data on associations between fluid administration and IAH. RESULTS: We identified three randomized controlled trials (RCTs), 38 prospective observational studies, 29 retrospective studies, 18 case reports in adults, two observational studies and 10 case reports in children, and three animal studies that addressed associations between fluid administration and IAH. Associations between fluid resuscitation and IAH were confirmed in most studies. Fluid resuscitation contributes to the development of IAH. However, patients with IAH receive more fluids to manage the effect of IAH on other organ systems, thereby causing a vicious cycle. Timing and approach to de-resuscitation are of utmost importance, but clear indicators to guide this decision-making process are lacking. In selected cases, only surgical decompression of the abdomen can stop deterioration and prevent further morbidity and mortality. CONCLUSIONS: Current evidence confirms an association between fluid resuscitation and secondary IAH, but optimal fluid management strategies for patients with IAH remain controversial.

Unusual presentation of infective endocarditis in ICU.

Bacterial endocarditis remains a challenging condition to manage owing to its variety of different presentations. This report describes a 55-year-old woman with endocarditis who presented confused with shoulder and back pain. Initial diagnosis was made difficult by a negative echocardiogram but aided by striking peripheral stigmata. She was treated for infective endocarditis as she met all five Duke's minor criteria for infective endocarditis. Gallium scan was a useful investigation in identifying lumbar spine and acromioclavicular joint septic foci. This case highlights the challenges of diagnosing endocarditis. It also describes how gallium scans can be useful in identifying occult septic emboli in these patients.

Intra-abdominal hypertension and hypoxic respiratory failure together predict adverse outcome - A sub-analysis of a prospective cohort.

PURPOSE: To assess whether the combination of intra-abdominal hypertension (IAH, intra-abdominal pressure ≥ 12 mmHg) and hypoxic respiratory failure (HRF, PaO2/FiO2 ratio < 300 mmHg) in patients receiving invasive ventilation is an independent risk factor for 90- and 28-day mortality as well as ICU- and ventilation-free days. METHODS: Mechanically ventilated patients who had blood gas analyses performed and intra-abdominal pressure measured, were included from a prospective cohort. Subgroups were defined by the absence (Group 1) or the presence of either IAH (Group 2) or HRF (Group 3) or both (Group 4). Mixed-effects regression analysis was performed. RESULTS: Ninety-day mortality increased from 16% (Group 1, n = 50) to 30% (Group 2, n = 20) and 27% (Group 3, n = 100) to 49% (Group 4, n = 142), log-rank test p < 0.001. The combination of IAH and HRF was associated with increased 90- and 28-day mortality as well as with fewer ICU- and ventilation-free days. The association with 90-day mortality was no longer present after adjustment for independent variables. However, the association with 28-day mortality, ICU- and ventilation-free days persisted after adjusting for independent variables. CONCLUSIONS: In our sub-analysis, the combination of IAH and HRF was not independently associated with 90-day mortality but independently increased the odds of 28-day mortality, and reduced the number of ICU- and ventilation-free days.

A pilot randomised controlled trial comparing reactive air and active alternating pressure mattresses in the prevention and treatment of pressure ulcers among medical ICU patients.

BACKGROUND: Data on the prevention and treatment of pressure ulcers (PU's) among ICU patients is sparse. OBJECTIVE: To compare PU outcomes in medial ICU patients nursed on either a reactive mattress overlay (ROHO, ROHO Inc, Belleville, IL, USA) or an active alternating pressure mattress (NIMBUS3, ArjoHuntleigh, Luton Bedfordshire, UK). DESIGN: Pilot prospective single blind randomised controlled clinical trial. INTERVENTION: Two types of pressure redistributing mattress. PATIENTS: Two groups of eight patients. METHODS: Patients included in the study were those at high risk (Norton scale <8) or with a PU on admission. RESULTS: The two groups had similar patient characteristics. However, the NIMBUS 3 group presented with more ulcers per patient on admission (62.5%) and more severe ulcers (20% category 3) while four patients (50%) presented with a single superficial ulcer in the ROHO group. HEALING: The progress of the ulcers showed significant decreases in PU surface area (p=0.05), total PUSH tool score (p=0.01) in the NIMBUS 3 group compared to the ROHO group. In the NIMBUS 3 group 82% of the ulcers improved versus none in the ROHO group (p=0.002) and 18% remained stable versus 33%. None of the ulcers deteriorated in the NIMBUS 3 group versus 67% in the ROHO group (p=0.006). Full thickness wounds (Category 3) were present in 22% of the NIMBUS 3 group versus 0% of the ROHO group on admission and in 0% versus 66.7% (p=0.008) respectively at the end of the pilot study. PREVENTION: Non-blanching erythema occurred equally in both arms at baseline; skin remained intact for the NIMBUS 3 group while 50% in the ROHO group worsened with superficial tissue loss. CONCLUSION: This small pilot study suggests that 'active' alternating therapy is a useful adjunct in the care of highly vulnerable patients, while the outcomes may be less favourable when using 'reactive', constant low pressure devices.

The impact of body position on intra-abdominal pressure measurement: a multicenter analysis.

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.