Normal Intra-abdominal Pressure Research Articles

Impact of intra-abdominal pressure on retrohepatic vena cava shape and flow in mechanically ventilated pigs

Conflicting results have been found regarding correlations between right atrial pressure (RAP) and inferior vena cava (IVC) diameter in mechanically ventilated patients. This finding could be related to an increase in intra-abdominal pressure (IAP). This study was designed to clarify whether variations in IVC flow rate caused by positive pressure ventilation are associated with changes in the retrohepatic IVC cross-section (ΔIVC) during major changes in volume status and IAP. Nine pigs were anesthetized, mechanically ventilated and equipped. IAP was set at 0, 15 and 30 mmHg during two conditions, i.e. normovolemia and hypovolemia, generated by blood removal to obtain a mean arterial pressure value lower than 60 mmHg. At each IAP increment, cardiac output, IVC flow and surface area were respectively assessed by flowmeters and transesophageal echocardiography. At normal IAP, even in presence of respiratory changes in IVC flows, no ΔIVC were observed during the two conditions. At high IAP, neither ΔIVC nor modulations of IVC flow were observed whatever the volemic status. The majority of animals with an IVC area of less than 0.65 cm2 showed evidence of IAP greater than RAP values. Negative RAP–IAP pressure gradients were found to occur with an IVC area of less than 0.65 cm2, suggesting that IVC dimensions determined using standard ultrasound techniques may indicate the direction of the RAP–IAP gradient. The clinical relevance of the present findings is that volume status should not be estimated from retrohepatic IVC dimensions in cases of high IAP.

A rare reason of abdominal compartment syndrome: non-Hodgkin lymphoma

Abdominal compartment syndrome (ACS) is characterized by intra-abdominal hypertension (IAH) which affects all body systems. In healthy individuals, normal intra-abdominal pressure (IAP) is <5 to 7 mmHg. The upper limit of IAP is generally accepted to be 12 mmHg. ACS has been classified into primary, secondary, and tertiary subtypes. Non-Hodgkin lymphoma (NHL) is a rare reason for ACS. We report here one case of NHL as a primary retroperitoneal mass in an 80-year-old male patient who presented with IAH.

Intra-abdominal hypertension in patients with sellar region tumors

BackgroundData on intra-abdominal hypertension [IAH] and secondary abdominal compartment syndrome [ACS] due to neurological insults are limited.MethodsThis was a prospective observational study conducted between January 2010 and January 2011 in the neurological ICU [NICU]. Forty-one consecutive patients with sellar region tumors [SRT] were enrolled into the study. If conservative therapy was ineffective in patients with ACS, thoracic epidural anesthesia [EA] was performed. Primary endpoint was defined as the efficacy of conservative treatment and EA in patients with IAH and ACS; secondary endpoint, the influence of IAH and ACS on outcomes.ResultsOf the 41 patients, 13 (31.7%) had normal intra-abdominal pressure and 28 (68.3%) developed IAH, of whom 9 (22%) had ACS (group II). On average, IAH developed on the second postoperative day, while ACS, between the third and the fifth day. Multiple organ dysfunction developed in 3 (23.1%) patients of group I and in 23 (82%) patients of group II (p = 0.0003). Ileus due to gastrointestinal dysmotility was present in 6 (46.2%) patients of group I and in all patients of group II (p = 0.0001). Significant risk factors for ileus were diencephalon dysfunction (whole group - in 33 patients (80.5%); group I - in 6 patients (46.2%); group II - in 27 patients (96.4%), p = 0.0002) and sepsis (whole group - in 8 patients (19.5%); group I - no cases; group II - in 8 patients (28.6%), p = 0.03). Conservative treatment was effective in the majority of patients (78.9%) with IAH and only in 3 (33%) patients with ACS. Thoracic EA was performed in four patients with ACS with success. Length of stay in the NICU was 6.5 ± 4.6 days in group I and 24.1 ± 25.7 (p = 0.02) days in group II. Five out of nine (55.6%) patients with ACS died. None of these patients received EA. All patients with EA had favorable outcomes.ConclusionThe development of IAH is common after SRT surgery. If conservative treatment is ineffective, EA can be considered in patients with secondary ACS. Further studies are warranted.

Early continuous veno-venous haemofiltration in the management of severe acute pancreatitis complicated with intra-abdominal hypertension: retrospective review of 10 years' experience

BackgroundConservative treatment of patients with severe acute pancreatitis (SAP) may be associated with development of intra-abdominal hypertension (IAH), deterioration of visceral perfusion and increased risk of multiple organ dysfunction. Fluid balance is essential for maintenance of adequate organ perfusion and control of the third space. Timely application of continuous veno-venous haemofiltration (CVVH) may help in balancing fluid replacement and removal of cytokines from the blood and tissue compartments. The aim of the present study was to determine whether CVVH can be recommended as a constituent of conservative treatment in patients with SAP who suffer IAH.MethodsA retrospective analysis of 10 years' experience with low-flow CVVH application in patients with SAP who develop IAH was. In all patients, measurement of the intra-abdominal pressure (IAP) was done indirectly through the urinary bladder. Sequential organ failure assessment (SOFA) score was calculated for severity assessment, and necrotizing forms were verified by contrast-enhanced computed tomography. Dynamics of IAP were analysed in parallel with signs of systemic inflammation, dynamics of C-reactive protein and cumulative fluid balance. All variables, complication rate and outcomes were analysed in the whole group and in patients with IAH (CVVH and no-CVVH groups).ResultsFrom the total of 130 patients, 75 were treated with application of CVVH and 55 without CVVH. Late hospitalization was associated with application of CVVH. Infection was observed in 28.5% of cases regardless of the type of treatment received, with a similar necessity for surgical intervention. IAH was observed in 68.5% of patients, and they had significantly higher SOFA scores compared to patients with normal IAP. CVVH treatment resulted in negative cumulative fluid balance starting from day 5 in patients with IAH, whereas without this treatment, fluid balance remained increasingly positive after a week. Finally, application of CVVH resulted in a lower infection rate and shorter hospital stay, 26.7% vs. 37.9%, and a median of 32 (interquartile range (IQR) = 60 to 12) days vs. 24 (IQR = 34 to 4) days, p = 0.05, comparing CVVH vs. no-CVVH group. Mortality rate reached 11.7% in the CVVH group and 13.8% in the no-CVVH group.ConclusionsEarly application of CVVH facilitates negative fluid balance and reduction of IAH in patients with SAP; it is not associated with increased infection or mortality rate and may reduce hospital stay.

Assessment of fluid responsiveness during increased intra-abdominal pressure: keep the indices, but change the thresholds

Dynamic variables of fluid responsiveness are useful guides for fluid management in patients under controlled positive pressure ventilation. In the previous issue of Critical Care, Jacques and colleagues show that these variables remain reliable predictors of fluid responsiveness in a porcine model of intra-abdominal hypertension, but threshold values are higher than during normal intra-abdominal pressure. Their threshold values, however, cannot be applied to clinical practice. This study suggests that intra-abdominal pressure must be measured in critically ill patients, and 'supranormal' values of dynamic variables should be analyzed with caution. The 'fluid responsive part' of an increased dynamic variable in such patients may be estimated by measuring its change during a fluid challenge.

Pulse pressure variation and stroke volume variation during increased intra-abdominal pressure: an experimental study

IntroductionThe aim of this study was to evaluate dynamic indices of fluid responsiveness in a model of intra-abdominal hypertension.MethodsNine mechanically-ventilated pigs underwent increased intra-abdominal pressure (IAP) by abdominal banding up to 30 mmHg and then fluid loading (FL) at this IAP. The same protocol was carried out in the same animals made hypovolemic by blood withdrawal. In both volemic conditions, dynamic indices of preload dependence were measured at baseline IAP, at 30 mmHg of IAP, and after FL. Dynamic indices involved respiratory variations in stroke volume (SVV), pulse pressure (PPV), and systolic pressure (SPV, %SPV and Δdown). Stroke volume (SV) was measured using an ultrasound transit-time flow probe placed around the aortic root. Pigs were considered to be fluid responders if their SV increased by 15% or more with FL. Indices of fluid responsiveness were compared with a Mann-Whitney U test. Then, receiver operating characteristic (ROC) curves were generated for these parameters, allowing determination of the cut-off values by using Youden's method.ResultsFive animals before blood withdrawal and all animals after blood withdrawal were fluid responders. Before FL, SVV (78 ± 19 vs 42 ± 17%), PPV (64 ± 18 vs 37 ± 15%), SPV (24 ± 5 vs 18 ± 3 mmHg), %SPV (24 ± 4 vs 17 ± 3%) and Δdown (13 ± 5 vs 6 ± 4 mmHg) were higher in responders than in non-responders (P < 0.05). Areas under ROC curves were 0.93 (95% confidence interval: 0.80 to 1.06), 0.89 (0.70 to 1.07), 0.90 (0.74 to 1.05), 0.92 (0.78 to 1.06), and 0.86 (0.67 to 1.06), respectively. Threshold values discriminating responders and non-responders were 67% for SVV and 41% for PPV.ConclusionsIn intra-abdominal hypertension, respiratory variations in stroke volume and arterial pressure remain indicative of fluid responsiveness, even if threshold values identifying responders and non-responders might be higher than during normal intra-abdominal pressure. Further studies are required in humans to determine these thresholds in intra-abdominal hypertension.

A novel solution to reduce the complications of distal shunt catheter displacement associated with obesity

Despite the varied sources of hydrocephalus, all shunt-treated conditions involve redirection of CSF to the body, commonly the peritoneum. Migration of the distal catheter tip out of the peritoneal space can occur, leading to the need for reoperation. Although uncommon, the authors have recently had 3 such cases in obese patients involving distal tubing retropulsion in otherwise uncomplicated surgeries. In addressing this issue, the authors performed anchoring of the distal catheter tubing through a small abdominal mesh, which is commonly used for hernia repair to increase catheter tube friction without compromising CSF flow. The results suggest this method may mitigate the chance of peritoneal catheter displacement in patients with higher than normal intraabdominal pressure.

Ramirez's Abdominoplasty Technique Combined With Intraperitoneal Chemohyperthermia After Surgical Cytoreductive Procedures for the Treatment of Advanced Intraperitoneal Cancer in Patients With Ventral Hernia

Patients affected by peritoneal carcinomatosis are frequently submitted to repeated laparotomies to reduce intra-abdominal bulky lesions and to enhance the systemic chemotherapeutic action. Aim of our study is to evaluate feasibility and results of cytoreductive surgery and intraperitoneal chemohypertermic (IPCH) perfusion combined with Ramirez's abdominoplastic technique in selected patients with voluminous ventral hernias.At the same time, we support the hypothesis that Ramirez' technique would allow a normal intra-abdominal pressure leading to an optimal capability of penetration of chemotherapeutic agents in IPCH.From January 1998 to December 2003, 30 patients were submitted to a surgical debulking and IPCH through a laparotomic approach involving a ventral hernia. After extensive cytoreductive surgery, we closed the large abdominal wall damage with Ramirez's abdominoplasty technique, followed by IPCH. The technique described by Ramirez uses bilateral muscle flap complexes transposed medially to reconstruct the central abdominal wall without using meshes to supply or reinforce the abdominal reconstruction.A total of 23 patients (76.7%) were completely cytoreducted and subjected to IPCH. Postoperative mortality was 1/30 (3.3%). Major morbidity was 5/30 (16.7%). After a mean follow-up of 3 years, no sign of recurrent ventral hernia was noted in the survivors.This study suggests that surgical debulking combined with IPCH is feasible in patients with a previously large abdominal wall defect using the functional Ramirez's abdominoplasty technique. The reconstructive technique allows a regular IPCH procedure without recurrence of the ventral hernia confirmed by clinical examination and abdominal computed tomography.

Prosthetic Mesh in Parastomal Hernia Prevention. Laparoscopic Approach

The use of a sublay mesh in open surgery has been probed to be an efficient strategy for the prevention of parastomal hernia. Based on these previous reports, placing a composite mesh (polypropylene/cellulose) in an intraperitoneal fashion seems to be a good technique when a laparoscopic approach is performed. This technique is easy to perform. Mesh is kept in place with the help of tackers, normal intra-abdominal pressure, and the colon itself. We report the description of a laparoscopic technique for placing an intraperitoneal mesh for the prevention of a parastomal hernia.

Correlations between intra-abdominal pressure and obesity-related co-morbidities

Background Obesity is associated with chronic increases in intra-abdominal pressure (IAP). The aim of the present study was to examine the correlation between the IAP and the number of obesity-related co-morbidities. Methods A total of 63 morbidly obese patients who were undergoing bariatric surgery had their IAP measured intraoperatively while in a supine position and under general anesthesia. The IAP readings were obtained through an indwelling urinary bladder catheter. The correlation of obesity-related co-morbidities, including systemic hypertension, type 2 diabetes mellitus, gastroesophageal reflux disease, urinary stress incontinence, lower extremity edema, obstructive sleep apnea, and abdominal wall hernia, and the level of IAP were examined using a stepwise regression analysis model. Results Of the 62 patients, 57 were women. The mean age was 44 ± 11 years, and the body mass index was 49 ± 10 kg/m 2. Of the 62 patients, 48 (77%) had an elevated IAP (≥9 cm H 2O). A significant and positive correlation was found between the IAP level and the number of obesity-related co-morbidities (Pearson's r = .8; P <.05). Stepwise logistic regression analysis revealed that systemic hypertension, American Society of Anesthesiologists score, and body mass index were predictors of elevated IAP. A normal IAP appeared to offer a protective effect against systemic hypertension. Conclusion In this cohort of mainly obese women, the baseline IAP of morbidly obese patients was abnormally elevated. A greater IAP correlated with the presence of a greater number of obesity-related co-morbid conditions. Systemic hypertension was significantly associated with an elevated IAP. Chronic increases in IAP might, in part, be responsible for the pathogenesis of systemic hypertension in the morbidly obese.

What is normal intra-abdominal pressure and how is it affected by positioning, body mass and positive end-expiratory pressure?

To describe what is defined as normal intra-abdominal pressure (IAP) and how body positioning, body mass index (BMI) and positive end-expiratory pressure (PEEP) affect IAP monitoring. A review of different databases was made (Pubmed, MEDLINE (January 1966-June 2007) and EMBASE.com (January 1966-June 2007)) using the search terms of "IAP", "intra-abdominal hypertension" (IAH), "abdominal compartment syndrome" (ACS), "body positioning", "prone positioning", "PEEP" and "acute respiratory distress syndrome" (ARDS). Prior to 1966, we selected older articles by looking at the reference lists displayed in the more recent papers. This review focuses on the concept that the abdomen truly behaves as a hydraulic system. The definitions of a normal IAP in the general patient population and morbidly obese patients are reviewed. Subsequently, factors that affect the accuracy of IAP monitoring, i.e., body position (head of bed elevation, lateral decubitus and prone position) and PEEP, are explored. The abdomen behaves as a hydraulic system with a normal IAP of about 5-7 mmHg, and with higher baseline levels in morbidly obese patients of about 9-14 mmHg. Measuring IAP via the bladder in the supine position is still the accepted standard method, but in patients in the semi-recumbent position (head of the bed elevated to 30 degrees and 45 degrees ), the IAP on average is 4 and 9 mmHg, respectively, higher. Future research should be focused on developing and validating predictive equations to correct for supine IAP towards the semi-recumbent position. Small increases in IAP in stable patients without IAH, turned prone, have no detrimental effects. The role of prone positioning in the unstable patient with or without IAH still needs to be established.

Effects of positive end-expiratory pressure on respiratory function and hemodynamics in patients with acute respiratory failure with and without intra-abdominal hypertension: a pilot study

IntroductionTo investigate the effects of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) with normal intra-abdominal pressure (IAP < 12 mmHg) and with intra-abdominal hypertension (IAH, defined as IAP ≥ 12 mmHg) during lung protective ventilation and a decremental PEEP, a prospective, observational clinical pilot study was performed.MethodsTwenty patients with ALI/ARDS with normal IAP or IAH treated in the surgical intensive care unit in a university hospital were studied. The mean IAP in patients with IAH and normal IAP was 16 ± 3 mmHg and 8 ± 3 mmHg, respectively (P < 0.001). At different PEEP levels (5, 10, 15, 20 cmH2O) we measured respiratory mechanics, partitioned into its lung and chest wall components, alveolar recruitment, gas-exchange, hemodynamics, extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI).ResultsWe found that ALI/ARDS patients with IAH, as compared to those with normal IAP, were characterized by: a) no differences in gas-exchange, respiratory mechanics, partitioned into its lung and chest wall components, as well as hemodynamics and EVLWI/ITBVI; b) decreased elastance of the respiratory system and the lung, but no differences in alveolar recruitment and oxygenation or hemodynamics, when PEEP was increased at 10 and 15cmH2O; c) at higher levels of PEEP, EVLWI was lower in ALI/ARDS patients with IAH as compared with those with normal IAP.ConclusionsIAH, within the limits of IAP measured in the present study, does not affect interpretation of respiratory mechanics, alveolar recruitment and hemodynamics.

The effects of carbon dioxide pneumoperitoneum on ovarian blood flow, oxidative stress markers, and morphology during laparoscopy: a rabbit model

To determine the effect of CO(2) pneumoperitoneum on the ovaries in an experimental pneumoperitoneum model. Experimental controlled study. University hospital. Sixteen adult female conventional rabbits. Group I (8 rabbits) was not subjected to intra-abdominal pressure (IAP). In group II (8 rabbits), IAP insufflation was performed at 12 mm Hg. In total, 60 minutes of pneumoperitoneum and 10 minutes of reperfusion were maintained. Ovarian blood flow (OBF) was studied using laser Doppler flowmetry. The time points of OBF measurements were as follows: OBFbaseline, 10 minutes before insufflation; OBF30min, 30 minutes after pneumoperitoneum; OBF60min, 60 minutes after pneumoperitoneum; and OBFreperfusion, 10 minutes after pneumoperitoneum desufflation. Mean OBF changes during CO(2) pneumoperitoneum (OBFmean) were also assessed. Blood perfusion units, tissue malondialdehyde values, and histopathologic damage scores. In group II, mean OBF values were significantly lower than in group I, especially for OBF30min, OBF60min, OBFreperfusion, and OBFmean. The mean tissue malondialdehyde value for group II was significantly higher than in the control group (104.48 +/- 20.07 nmol/g vs. 64.12 +/- 8.77 nmol/g, respectively). Compared with group I, in group II histologic specimens of the ovaries had higher scores for follicular cell degeneration, vascular congestion, hemorrhage, and inflammatory cell infiltration. Pneumoperitoneum, even at normal IAP levels, leads to significant oxidative stress-induced biochemical and histologic damage to the ovaries.

A study of intragastric and intravesicular pressure changes during rest, coughing, weight lifting, retching, and vomiting

In patients undergoing a variety of procedures, surgical success is in part dependent on maintaining normal intra-abdominal pressure in the immediate postoperative period. Our objective was to quantify intragastric and intravesicular pressures during activities, through the use of manometry catheters. Ten healthy volunteers had a manometry catheter placed transnasally, and a urinary Foley catheter placed. Baseline intragastric and intravesicular pressures were recorded and the catheters were then transduced continuously. Pressures were recorded with activity: coughing, lifting weights, retching (dry heaving), and vomiting. All pressure changes were significant from baseline except for weight lifting. The highest intragastric pressure was 290 mmHg, seen during vomiting. Comparison of intragastric and intravesicular pressures showed no significant difference. There was significantly higher intragastric pressure with vomiting and retching as compared with coughing, whereas coughing applied more pressure than weight lifting. This is the first report of intragastric pressures during vomiting and retching (dry heaving). We conclude that vomiting and retching (dry heaving) can render significant forces on any tissue apposition within the stomach or the peritoneal cavity.

The effect of CO2 insufflation-desufflation attacks on tissue oxidative stress markers during laparoscopy: a rat model

To determine the effects of sudden intra-abdominal pressure (IAP) changes on the terminal ileum in a pneumoperitoneum model. An experimental controlled study. University hospital in Turkey. Thirty-two adult female Sprague-Dawley rats. The rats were divided into four groups. Group 1 was not subjected to IAP. In group 2, IAP insufflation was performed continuously to keep the IAP at 10 mmHg. Groups 3 and 4 underwent an insufflation-desufflation procedure: group 3 was fluctuated 5 times, and group 4 was fluctuated 10 times within the pneumoperitoneum period of 60 minutes. Thirty minutes after the desufflation, the terminal ileum was removed for the measurement of tissue malondialdehyde (MDA) values and histopathological examination. The tissue MDA values and histopathological damage scores. The tissue MDA values in the IAP groups (groups 2, 3, and 4) were significantly increased when compared with those of the control group. The mean MDA value in group 4 was higher than that in groups 2 and 3. Histopathologic oxidative damage scores in the mucosa and submucosal layers were significantly higher in groups 2 and 3, compared with those of the control group. However, the highest histopathologic damage scores were observed in group 4. Unexpected desufflation-insufflation even at normal IAP levels during laparoscopy leads to significant oxidative stress-induced damage in the terminal ileum.

What is the normal intra-abdominal pressure in critically ill children and how should we measure it?*

The intravesical method has been validated and is considered the gold standard for indirect intra-abdominal pressure (IAP) measurements. In adults, a standard volume (25 mL) is instilled into the bladder to measure IAP. However, the optimal volume for accurate IAP measurements in children has not been well studied and using inappropriate volumes could give erroneous IAP readings. To determine the normal IAP in critically ill children and the optimal volume for IAP measurement by the intravesical method in this population. Prospective observational study. Tertiary pediatric intensive care unit. Ninety-six mechanically ventilated children younger than 18 yrs of age with no clinical evidence of intra-abdominal hypertension. Graduated volumes of normal saline in increments of 3-50 mL were instilled in the bladder via a urethral catheter. IAP was recorded by using the AbViser device (WolfeTory Medical, Inc., Salt Lake City, UT) with each instillation. A pressure-volume curve was generated for every patient, and the minimum and mean optimal volumes were determined from this curve. Data were analyzed by stratification of patients according to weights 0-10 kg, >10-20 kg, and >20-50 kg. Descriptive statistics was used for statistical analysis. Normal IAP for critically ill children was 7 +/- 3 and was similar in the different weight groups (p = .745). Although the mean optimal volume to measure accurate IAP was variable in the different weight groups, the minimum optimal volume was 3 mL irrespective of weight. Mean IAP in critically ill children is 7 +/- 3 mm Hg. The minimum optimal volume needed to accurately measure IAP by the intravesical method in children is 3 mL. We recommend that 3 mL be the standard instillation volume for IAP measurement by the intravesical method in children. IAP >10 mm Hg should be considered elevated in children.

Abdominal compartment syndrome in patients with severe acute pancreatitis in early stage

To study retrospectively the influence of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) in patients with early acute pancreatitis (AP) (during the first week after admission) on physiological functions, and the association of the presence of IAH/ACS and outcome. Patients (n = 74) with AP recruited in this study were divided into two groups according to intra-abdominal pressure (IAP) determined by indirect measurement using the transvesical route via Foley bladder catheter during the first week after admission. Patients (n = 44) with IAP >or= 12 mmHg were assigned in IAH group, and the remaining patients (n = 30) with IAP < 12 mmHg in normal IAP group. For analysis of the influence of IAH/ACS on organ function and outcome, the physiological parameters and the occurrence of organ dysfunction during intensive care unit (ICU) stay were recorded, as were the incidences of pancreatic infection and in-hospital mortality. IAH within the first week after admission was found in 44 patients (59.46%). Although the APACHE II scores on admission and the Ranson scores within 48 h after hospitalization were elevated in IAH patients in early stage, they did not show the statistically significant differences from patients with normal IAP within a week after admission (16.18 +/- 3.90 vs 15.70 +/- 4.25, P = 0.616; 3.70 +/- 0.93 vs 3.47 +/- 0.94, P = 0.285, respectively). ACS in early AP was recorded in 20 patients (27.03%). During any 24-h period of the first week after admission, the recorded mean IAP correlated significantly with the Marshall score calculated at the same time interval in IAH group (r = 0.635, P < 0.001). Although ACS patients had obvious amelioration in physiological variables within 24 h after decompression, the incidences of pancreatitic infection, septic shock, multiple organ dysfunction syndrome (MODS) and death in the patients with ACS were significantly higher than that in other patients without ACS (pancreatitic infection: 60.0% vs 7.4%, P < 0.001; septic shock: 70.0% vs 11.1%, P < 0.001; MODS: 90.0% vs 31.5%, P < 0.001; mortality: 75.0% vs 3.7%, P < 0.001). IAH/ACS is a frequent finding in patients admitted to the ICU because of AP. Patients with IAP at approximately 10-12 mmHg and early signs of changes in physiologic variables should be seriously considered for urgent decompression to improve survival.

DETERMINING NORMAL VALUES FOR INTRA‐ABDOMINAL PRESSURE

Intra-abdominal pressure (IAP) measurements can be used for the early detection and management of the abdominal compartment syndrome. IAP values are widely thought to be atmospheric or subatmospheric. However, there are no reports that describe normal IAP values using urinary bladder pressure measurements in patients not suspected of having a raised IAP level. This study sought to determine these normal values to aid our interpretation of IAP measurements in post-surgical patients or patients with suspected increased IAP. Urinary bladder pressure measurements were carried out in 40 men and 18 women awake medical or non-abdominal surgery inpatients with existing indwelling catheters. Measurements were made in the supine, 30 degrees and 45 degrees sitting positions. Comparisons were carried out to determine the effects on urinary bladder pressure of body position, sex and a suspected diagnosis of benign prostatic hypertrophy. Median values for IAP were higher if measured in a more upright position (P < 0.0001). Median values were supine, 9.5 cmH2O (range, 1-18 cmH2O); 30 degrees upright, 11.5 cmH2O (range, 3-19 cmH2O); and at 45 degrees upright, 14.0 cmH2O (range, 4-22 cmH2O). Measurements recorded were neither atmospheric nor subatmospheric. IAP was higher in men compared with women in the supine and 30 degrees positions (P < 0.05) but not in the 45 degrees position (P = 0.083). There was no significant difference between patients with and without suspected benign prostatic hypertrophy. Normal IAP using urinary bladder pressure in awake patients are above atmospheric pressure. As a patient is moved from the supine into the upright position, IAP measurements increase.

Creep Behavior of Commonly Used Suture Materials in Abdominal Wall Surgery

The incidence of incisional hernia after abdominal wall closure is high. Furthermore, recurrence is a significant complication after correction of all abdominal wall hernias. Besides surgeon- and patient-related factors, in this experimental study a third factor, i.e., creep behavior of suture materials, is introduced and evaluated. Creep measurements were performed on 0 and 2-0 Prolene (Ethicon, Johnson & Johnson Intl., Somerville, NJ) and 1 and 2-0 PDSII (Ethicon, Johnson & Johnson Intl.) sutures. Two different loads were used representing normal intra-abdominal pressure (IAP) and pathological IAP. A mean percentage of elongation was calculated for each type of suture material. Statistical analysis was performed using analysis of variance. All suture materials showed significant (3-51%) creep behavior. Prolene sutures showed more creep than PDSII sutures in both loading conditions. As significant creep was demonstrated for commonly used suture materials, creep might be a significant influential factor with regard to the etiology of incisional hernias and recurrence after abdominal wall hernia repair.

Estudio experimental comparativo entre una prótesis compuesta (PL-PU99) y una prótesis biológica (Surgisis ®) en el cierre temporal abdominal

In some diseases of peritoneal origin, temporary closure of the abdominal cavity is required to avoid compartmental syndrome. This allows normal intra-abdominal pressure to be maintained and the fascial edges to be preserved for subsequent definitive closure. Defects (7 x 4 cm) were created in the anterior abdominal wall of New Zealand white rabbits and were repaired using an oval-shaped patch of a prosthesis designed by our team (PL-PU99) or a prosthesis of biological origin (Surgisis) of similar dimensions to the defects. The biomaterials were fixed to the cut edges of the wall by 2 polypropylene running sutures interrupted only at the corners, leaving the patch in contact with the atmosphere. Fourteen days after implantation, prosthesis/anchorage tissue specimens were taken for light and scanning electron microscopy, morphometric measurements and immunohistochemical macrophage identification (using the RAM-11 antibody). There were no cases of mortality or implant rejection. Small areas of loose adhesions were observed on some implants (covering 0.31 +/- 0.03% of the PL-PU99 implants and 31.60 +/- 7.35% of Surgisis). The neoperitoneum induced by both implant types was homogenous and well organized, with thicknesses of 427.60 +/- 8.38 microm (PL-PU99) and 171.99 +/- 18.70 microm (Surgisis). No significant differences were observed in terms of the macrophage reaction induced (PL-PU99 19.76 +/- 1.59%; Surgisis 21.07 +/- 8.93% macrophages). a) The PL-PU99 prosthesis provoked fewer adhesions and generated a thicker neoperitoneum. b) Both prostheses would probably be suitable for temporary closure of the abdominal cavity.