Influence of Elevated Intra-abdominal Pressure on Suture Tension Dynamics in a Porcine Model.

BACKGROUND: Inadequate suture tension is a risk factor for the failure of laparotomy closure. Suture tension dynamics in the abdominal wall are still obscure due to the lack of measuring devices. To answer the questions if intra-abdominal hypertension (IAH) influences suture tension in midline laparotomies and if IAH leads to a permanent loss of suture tension, microsensors were applied in a porcine model of IAH. MATERIAL AND METHODS: Microsensors measuring suture tension "on the thread" with a frequency of 1/s were developed and implanted in the suture lines of midline laparotomies in four pigs. During a 23-h experiment under general anesthesia, two intervals of IAH (30 mm Hg) were applied, interrupted by a 3-h interval without elevated intra-abdominal pressure. RESULTS: All sensors showed an immediate and reproducible response to changes of intra-abdominal pressure. The two 9-h periods of IAH resulted in a significant elevation of suture tension (P = 0.003 and P = 0.0009, respectively). Reducing the IAH lead to a significant loss of suture tension (P = 0.0005 and P = 0.0001, respectively). After the second interval with IAH, a complete loss of mean suture tension was observed. A statistically significant "recovery" of suture tension in the interval between the two phases with IAH was not observed. CONCLUSIONS: Intervals with elevated intra-abdominal pressure have a direct influence on suture tension in midline laparotomy wounds. Intervals with IAH lead to a significant loss of suture tension in the suture line and to a complete loss of mean suture tension at the end of this experiment. A subsequent gaping of the fascia might contribute to either acute or chronic failure of laparotomy closure.

The role of abdominal compliance, the neglected parameter in critically ill patients - a consensus review of 16. Part 1: definitions and pathophysiology.

Over the last few decades, increasing attention has been paid to understanding the pathophysiology, aetiology, prognosis, and treatment of elevated intra-abdominal pressure (IAP) in trauma, surgical, and medical patients. However, there is presently a relatively poor understanding of intra-abdominal volume (IAV) and the relationship between IAV and IAP (i.e. abdominal compliance). Consensus definitions on Cab were discussed during the 5th World Congress on Abdominal Compartment Syndrome and a writing committee was formed to develop this article. During the writing process, a systematic and structured Medline and PubMed search was conducted to identify relevant studies relating to the topic. According to the recently updated consensus definitions of the World Society on Abdominal Compartment Syndrome (WSACS), abdominal compliance (Cab) is defined as a measure of the ease of abdominal expansion, which is determined by the elasticity of the abdominal wall and diaphragm. It should be expressed as the change in IAV per change in IAP (mL [mm Hg]⁻¹). Importantly, Cab is measured differently than IAP and the abdominal wall (and its compliance) is only a part of the total abdominal pressure-volume (PV) relationship. During an increase in IAV, different phases are encountered: the reshaping, stretching, and pressurisation phases. The first part of this review article starts with a comprehensive list of the different definitions related to IAP (at baseline, during respiratory variations, at maximal IAV), IAV (at baseline, additional volume, abdominal workspace, maximal and unadapted volume), and abdominal compliance and elastance (i.e. the relationship between IAV and IAP). An historical background on the pathophysiology related to IAP, IAV and Cab follows this. Measurement of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The Cab is one of the most neglected parameters in critically ill patients, although it plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion. The definitions presented herein will help to understand the key mechanisms in relation to Cab and clinical conditions and should be used for future clinical and basic science research. Specific measurement methods, guidelines and recommendations for clinical management of patients with low Cab are published in a separate review.

The role of abdominal compliance, the neglected parameter in critically ill patients - a consensus review of 16. Part 2: measurement techniques and management recommendations.

The recent definitions on intra-abdominal pressure (IAP), intra-abdominal volume (IAV) and abdominal compliance (Cab) are a step forward in understanding these important concepts. They help our understanding of the pathophysiology, aetiology, prognosis, and treatment of patients with low Cab. However, there is still a relatively poor understanding of the different methods used to measure IAP, IAV and Cab and how certain conditions may affect the results. This review will give a concise overview of the different methods to assess and estimate Cab; it will list important conditions that may affect baseline values and suggest some therapeutic options. Abdominal compliance (Cab), defined as a measure of the ease of abdominal expansion, is measured differently than IAP. The compliance of the abdominal wall is only a part of the total abdominal pressure-volume (PV) relationship. Measurement or estimation of Cab is difficult at the bedside and can only be done in a case of change (removal or addition) in IAV. The different measurement techniques will be discussed in relation to decreases (ascites drainage, haematoma evacuation, gastric suctioning) or increases in IAV (gastric insufflation, laparoscopy with CO2 pneumoperitoneum, peritoneal dialysis). More specific techniques using the interactions between the thoracic and abdominal compartment during positive pressure ventilation will also be discussed (low flow PV loop, respiratory IAP variations, respiratory abdominal variation test, mean IAP and abdominal pressure variation), together with the concept of the polycompartment model. The relation between IAV and IAP is linear at low IAV and becomes curvilinear and exponential at higher volumes. Specific conditions in relation to increased (previous pregnancy or laparoscopy, gynoid fat distribution, ellipse-shaped internal abdominal perimeter) or decreased Cab (obesity, fluid overload, android fat distribution, sphere-shaped internal abdominal perimeter) will be discussed as well as their impact on baseline IAV, IAP, reshaping capacity and abdominal workspace volume. Finally, we suggest possible treatment options in situations of unadapted IAV according to existing Cab, which results in high IAP. A large overlap exists between the treatment of patients with abdominal hypertension and those with low Cab. The Cab plays a key role in understanding the deleterious effects of unadapted IAV on IAP and end-organ perfusion and function. If we can identify patients with low Cab, we can anticipate and select the most appropriate surgical treatment to avoid complications such as IAH or ACS.

Influence of two different levels of intra-abdominal hypertension on bacterial translocation in a porcine model.

BACKGROUND: The purpose of the present study was to quantify bacterial translocation to mesenteric lymph nodes due to different levels of intra-abdominal hypertension (IAH; 15 vs. 30 mmHg) lasting for 24 h in a porcine model. METHODS: We examined 18 anesthetized and intubated pigs (52.3 ± 4.7 kg) which were randomly allocated to three experimental groups (each n = 6) and studied over a period of 24 h. After preparation and establishing a steady state, the intra-abdominal pressure (IAP) was increased stepwise to 30 mmHg in six animals using a carbon dioxide (CO2) insufflator (IAP-30 group). In the second group, IAP was increased to 15 mmHg (IAP-15 group), while IAP remained unchanged in another six pigs (control group). Using a pulse contour cardiac output (PiCCO®) monitoring system, hemodynamic parameters as well as blood gases were recorded periodically. Moreover, peripheral and portal vein blood samples were taken for microbiological examinations. Lymph nodes from the ileocecal junction were sampled during an intra-vital laparotomy at the end of the observational period. After sacrificing the animals, bowel tissue samples and corresponding mesenteric lymph nodes (MLN) were extracted for histopathological and microbiological analyses. RESULTS: Cardiac output decreased in all groups. In IAP-30 animals, volumetric preload indices significantly decreased, while those of IAP-15 pigs did not differ from those of controls. Under IAH, the mean arterial pressure (MAP) in the IAP-30 group declined, while MAP in the IAP-15 group was significantly elevated (controls unchanged). PO2 and PCO2 remained unchanged. The grade of ischemic damage of the intestines (histopathologically quantified using the Park score) increased significantly with different IAH levels. Accordingly, the amount of translocated bacteria in intestinal wall specimens as well as in MLN significantly increased with the level of IAH. Lymph node cultures confirmed the relation between bacterial translocation (BT) and IAP. The most often cultivated species were Escherichia coli, Staphylococcus, Clostridium, Pasteurella, and Streptococcus. Bacteremia was detected only occasionally in all three groups (not significantly different) showing gut-derived bacteria such as Proteus, Klebsiella, and E. coli spp. CONCLUSION: In this porcine model, a higher level of ischemic damage and more BT were observed in animals subjected to an IAP of 30 mmHg when compared to animals subjected to an IAP of 15 mmHg or controls.

Recognition and management of abdominal compartment syndrome among German anesthetists and surgeons: a national survey.

BACKGROUND: Abdominal compartment syndrome (ACS) is a life threatening condition that may affect any critically ill patient. Little is known about the recognition and management of ACS in Germany. METHODS: A questionnaire was mailed to departments of surgery and anesthesia from German hospitals with more than 450 beds. RESULTS: Replies (113) were received from 222 eligible hospitals (51%). Most respondents (95%) indicated that ACS plays a role in their clinical practice. Intra-abdominal pressure (IAP) is not measured at all by 26%, while it is routinely done by 30%. IAP is mostly (94%) assessed via the intra-vesical route. Of the respondents, 41% only measure IAP in patients expected to develop ACS; 64% states that a simpler, more standardized application of IAP measurement would lead to increased use in daily clinical practice. CONCLUSIONS: German anesthesiologists and surgeons are familiar with ACS. However, approximately one fourth never measures IAP, and there is considerable uncertainty regarding which patients are at risk as well as how often IAP should be measured in them.

Recognition and management of abdominal compartment syndrome among German pediatric intensivists: results of a national survey.

INTRODUCTION: Several decades ago, the beneficial effects of goal-directed therapy, which include decompressive laparotomy (DL) and open abdomen procedures in cases of intra-abdominal hypertension (IAH) in children, were proven in the context of closures of abdominal wall defects and large-for-size organ transplantations. Different neonatologic and pediatric disease patterns are also known to be capable of increasing intra-abdominal pressure (IAP). Nevertheless, a considerable knowledge transfer regarding such risk factors has hardly taken place. When left undetected and untreated, IAH threatens to evolve into abdominal compartment syndrome (ACS), which is accompanied by a mortality rate of up to 60% in children. Therefore, the present study looks at the recognition and knowledge of IAH/ACS among German pediatric intensivists. METHODS: In June 2010, a questionnaire was mailed to the heads of pediatric intensive care units of 205 German pediatric hospitals. RESULTS: The response rate was 62%. At least one case of IAH was reported by 36% of respondents; at least one case of ACS, by 25%. Compared with adolescents, younger critically ill children appeared to develop IAH/ACS more often. Routine measurements of IAP were said to be performed by 20% of respondents. Bladder pressure was used most frequently (96%) to assess IAP. Some respondents (17%) only measured IAP in cases of organ dysfunction and failure. In 2009, the year preceding this study, 21% of respondents claimed to have performed a DL. Surgical decompression was indicated if signs of organ dysfunction were present. This was also done in cases of at least grade III IAH (IAP > 15 mmHg) without organ impairment. CONCLUSIONS: Although awareness among pediatricians appears to have been increasing over the last decade, definitions and guidelines regarding the diagnosis and management of IAH/ACS are not applied uniformly. This variability could express an ever present lack of awareness and solid prospective data.

Abdominal compartment syndrome in childhood: diagnostics, therapy and survival rate.

PURPOSE: The abdominal compartment syndrome (ACS) in childhood is a rare but dire disease if diagnosed delayed and treated improperly. The mortality amounts up to 60% (Beck et al. in Pediatr Crit Care Med 2:51-56, 2001). ACS is defined by a sustained rise of the intraabdominal pressure (IAP) together with newly developed organ dysfunction. The present study reports on 28 children with ACS to evaluate its potential role in the diagnosis, treatment and outcome of ACS. METHODS: Retrospectively, medical reports and outcome of 28 children were evaluated who underwent surgical treatment for ACS. The diagnosis of ACS was established by clinical signs, intravesical pressure-measurements and concurrent organ dysfunction. RESULTS: Primary ACS was found in 25 children (89.3%) predominantly resulting from polytrauma and peritonitis. Three children presented secondary ACS with sepsis (2 cases) and combustion (1 case) being the underlying causative diseases. Therapy of choice was the decompression of the abdominal cavity with implantation of an absorbable Vicryl(®) mesh. In 18 cases the abdominal cavity could be closed later, while in the other ten cases granulation of the mesh was allowed. The overall survival rate was 78.6% (22 of 28 children). The cause of death in the remaining six cases (21.4%) was sepsis with multiorgan failure. CONCLUSION: Our results suggest that early establishment of the specific diagnosis of ACS followed by swift therapy with reduction of intraabdominal hypertension is essential in order to further reduce the high mortality rate associated with this condition.

Intraoperative laser fluorescence angiography in colorectal surgery: a noninvasive analysis to reduce the rate of anastomotic leakage.

PURPOSE: Up to 19% of all colorectal resections develop clinically apparent insufficiencies. Insufficient perfusion of the anastomosis is recognized as an important risk factor. As tissue perfusion can be objectified intraoperatively using laser fluorescence angiography (LFA), its effect on the rate of anastomotic complications was evaluated in a retrospective matched-pairs analysis. METHODS: Between 2003 and 2008, all anastomosis or resection margins in colorectal cancer resections were investigated intraoperatively using LFA (LFA group). Patients with colorectal cancer resections between 1998 and 2003 without LFA served as the control group. Four hundred two patients were matched for age, T-stage, type of resection and anastomosis, defunctioning stoma, administration of blood, emergency conditions, and body mass index. Statistical analysis was performed using the Fisher and the Wilcoxon tests. RESULTS: Twenty-two surgical revisions were necessary due to anastomotic leakage, seven (3.5%) in the LFA group and 15 (7.5%) in the control group. Subgroup analysis revealed that in elective resections the rate of revision was 3.1% (LFA group) and 7.7% (control group) (p = 0.04, risk of revision (ROR) reduced by 60%). In patients older than 70 years, the rate of revision was 4.3% (LFA group) compared to 11.9% (control group) (p = 0.04, ROR reduced by 64%). After hand-sewn anastomosis, the rate of revision was 1.2% (LFA group) and 8.5% (control group) (p = 0.03, ROR reduced by 84%). Hospital stay was significantly reduced in the LFA group (Wilcoxon test; p = 0.01). CONCLUSION: There was an overall reduction in the absolute revision rate of 4% in the LFA group and a significantly reduced rate of revision in the subgroup analysis of patients undergoing elective colorectal resections, in patients older than 70 years and in patients with hand-sewn anastomosis. This demonstrates that LFA is a method that may significantly reduce not only the rate of severe complications in colorectal surgery but also the hospital length of stay.

Effects of preserved spontaneous breathing activity during mechanical ventilation in experimental intra-abdominal hypertension.

PURPOSE: Ventilation problems are common in critically ill patients with intra-abdominal hypertension. The aim of this study was to investigate the effects of preserved spontaneous breathing during mechanical ventilation on hemodynamics, gas exchange, respiratory function and lung injury in experimental intra-abdominal hypertension. METHODS: Twenty anesthetized pigs were intubated and ventilated for 24 h with biphasic positive airway pressure without (BIPAP(PC)) or with additional, unsynchronized spontaneous breathing (BIPAP(SB)). In 12 animals, intra-abdominal pressure was increased to 30 mmHg for two 9 h periods followed by a 3 h pressure relief each. Eight animals served as controls and were ventilated for 24 h. Hemodynamics, gas exchange and respiratory mechanics were measured and lung injury was determined histologically. RESULTS: Intra-abdominal hypertension caused significant impairment of hemodynamics and respiratory mechanics in both modes. In the presence of intra-abdominal hypertension, BIPAP(SB) did not demonstrate superior respiratory mechanics and cardiovascular stability as compared to BIPAP(PC). Although the decrease of dynamic compliance and the increase of airway pressures were mitigated, BIPAP(SB) failed to lower pulmonary vascular resistance and caused increased dead space ventilation (p = 0.007). Blood pressures and cardiac output increased in BIPAP(SB), caused by an increase in heart rate (p < 0.001), but not in stroke volume (p = 0.06). BIPAP(SB) was associated with an increased breathing effort, decreased transpulmonary pressure during inspiration and lower lobe diffuse alveolar damage (p = 0.002). CONCLUSIONS: In the presence of severe intra-abdominal hypertension, the addition of unsupported spontaneous breaths to BIPAP did not improve hemodynamic and respiratory function and caused greater histopathologic damage to the lungs.

Histomorphologic and ultrastructural lesions of the pancreas in a porcine model of intra-abdominal hypertension.

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome are increasingly observed in patients with severe acute pancreatitis (SAP). The aim of this study was to investigate the effects of IAH on pancreatic histology and ultrastructure in a porcine model. We examined 16 intubated and anesthetized domestic pigs with a mean body weight of 50.6 (SD, 3.8) kg. Using a CO2 pneumoperitoneum, the intra-abdominal pressure was increased to 30 mmHg for an investigation period of 6 or 12 h (each study group n = 6). In the control group, the intra-abdominal pressure remained 3.9 (SD, 5.4) mmHg for 12 h. Additional Ringer's solution was infused to maintain cardiac output at the level of controls. After the observation period, specimens were taken for histological and ultrastructural analysis, and animals were killed. Cardiac output did not change when compared with control. Histologically, mild- to moderate-grade necrosis was observed after 12 h of IAH. In the ultrastructural analysis, leukocyte infiltration and swelling of endothelial cells were found. In the acinar cells of the exocrine pancreas, endoplasmic reticulum was dilated, and necrosis was noticed. Mitochondrial damage manifested as cisternal destruction with formation of large vacuoles. In this porcine model, 6 and 12 h of IAH resulted in light-microscopical and ultrastructural changes comparable to pancreatitis in humans. As SAP is often accompanied by IAH, the finding of the underlying study suggests a vicious cycle in which IAH may worsen pancreatitis. Ultimately, these findings are in favor of a decompression in patients with SAP and IAH.

Direct intra-abdominal pressure monitoring via piezoresistive pressure measurement: a technical note.

BACKGROUND: Piezoresistive pressure measurement technique (PRM) has previously been applied for direct IAP measurement in a porcine model using two different devices. Aim of this clinical study was to assess both devices regarding complications, reliability and agreement with IVP in patients undergoing elective abdominal surgery. METHODS: A prospective cohort study was performed in 20 patients randomly scheduled to receive PRM either by a Coach-probe or an Accurate(++)-probe (both MIPM, Mammendorf, Germany). Probes were placed on the greater omentum and passed through the abdominal wall paralleling routine drainages. PRM was compared with IVP measurement by t-testing and by calculating mean difference as well as limits of agreement (LA). RESULTS: There were no probe related complications. Due to technical limitations, data could be collected in 3/10 patients with Coach and in 7/10 patients with Accurate++. Analysis was carried out only for Accurate++. Mean values did not differ to mean IVP values. Mean difference to IVP was 0.1 +/- 2.8 mmHg (LA: -5.5 to 5.6 mmHg). CONCLUSION: Direct IAP measurement was clinically uneventful. Although results of Accurate++ were comparable to IVP, the device might be too fragile for IAP measurements in the clinical setting. Local ethical committee trial registration: EK2024.

Hernia recurrence after laparotomy: how to close an incised light-weight mesh?

A rising number of patients require relaparotomy after implantation of mesh materials for incisional hernia (IH) repair. No published recommendation concerning how to close the incision in a surgical mesh exists. We describe a central IH recurrence through a partly absorbable mesh positioned in the retromuscular plane 16 months after laparotomy due to a small bowel ileus. This recurrence was repaired using a heavy-weight, monofilament polypropylene mesh, again in the retromuscular position. Reducing the amount of nonabsorbable material in large pore hernia meshes leads to markedly reduced scar formation rather than the formation of a thick scar plate. Once cut and resutured, this scar may be too weak to withstand the mechanical strain, giving rise to a 'blow-out' IH recurrence, as demonstrated in our case. In these cases, re-enforcement with a nonabsorbable, small, porous polypropylene mesh in the retromuscular space is feasible and leads to the development of a mechanically stable scar.

Clinical evaluation of an air-capsule technique for the direct measurement of intra-abdominal pressure after elective abdominal surgery.

BACKGROUND: The gold standard for assessment of intraabdominal pressure (IAP) is via intravesicular pressure measurement (IVP). This accepted technique has some inherent problems, e.g. indirectness. Aim of this clinical study was to assess direct IAP measurement using an air-capsule method (ACM) regarding complications risks and agreement with IVP in patients undergoing abdominal surgery. METHODS: A prospective cohort study was performed in 30 patients undergoing elective colonic, hepatic, pancreatic and esophageal resection. For ACM a Probe 3 (Spiegelberg, Germany) was placed on the greater omentum. It was passed through the abdominal wall paralleling routine drainages. To compare ACM with IVP t-testing was performed and mean difference as well as limits of agreement were calculated. RESULTS: ACM did not lead to complications particularly with regard to organ lesion or surgical site infection. Mean insertion time of ACM was 4.4 days (min-max: 1-5 days). 168 pairwise measurements were made. Mean ACM value was 7.9 +/- 2.7 mmHg while mean IVP was 8.4 +/- 3.0 mmHg (n.s). Mean difference was 0.4 mmHg +/- 2.2 mmHg. Limits of agreement were -4.1 mmHg to 5.1 mmHg. CONCLUSION: Using ACM, direct IAP measurement is feasible and uncomplicated. Associated with relatively low pressure ranges (<17 mmHg), results are comparable to bladder pressure measurement.

Evaluation of a modified piezoresistive technique and a water-capsule technique for direct and continuous measurement of intra-abdominal pressure in a porcine model.

OBJECTIVE: Intravesical pressure measurement is considered to be the gold standard for the assessment of intra-abdominal pressure. However, this method is indirect and depends on a physiologic bladder function. We evaluated a modified piezoresistive technique and a water-capsule technique for direct and continuous intra-abdominal pressure measurement. DESIGN: Experimental study. SETTING: Animal research laboratory. SUBJECTS: Eleven male domestic pigs. INTERVENTIONS: In anesthetized and mechanically ventilated animals, CO2 was insufflated to stepwise increase the intra-abdominal pressure to 30 mm Hg. Pressure was then held constant for 9 hrs followed by decompression. Piezoresistive measurement and water-capsule measurement probes were placed intra-abdominally. MEASUREMENTS AND MAIN RESULTS: Readings of intravesical pressure measurement, piezoresistive measurement, and water-capsule measurement were taken hourly. Mean difference to insufflator readings, confidence intervals, and limits of agreement were calculated. Differences between applied pressure and intra-abdominal pressure readings were assessed using a two-factor analysis of variance. No significant differences between methods could be observed. During stepwise pressure increase, limits of agreements were -3.6 to 3.6 mm Hg. Confidence intervals were -3.4 to 3.5 (intravesical pressure measurement), -1.6 to 1.5 (piezoresistive measurement), and 0.5 to 2.9 mm Hg (water-capsule measurement). In the presence of constantly elevated intra-abdominal pressure, limits of agreement ranged from -8.2 to +8.2 mm Hg. Confidence intervals were -0.4 to 6.2 (intravesical pressure measurement), -0.2 to 2.7 (piezoresistive measurement), and 1.1 to 5.1 mm Hg (water-capsule measurement). CONCLUSIONS: Both piezoresistive measurement and water-capsule measurement had smaller confidence intervals than intravesical pressure measurement, indicating higher precision, whereas water-capsule measurement had a significant offset. Piezoresistive measurement could be the most suitable device for continuous direct intra-abdominal pressure monitoring in specific patients.

Physical fitness after apical resection for the treatment of primary spontaneous pneumothorax.

The objective of the present study was to assess the physical fitness of patients after apical resection and partial apical pleurectomy for the treatment of primary spontaneous pneumothorax (PSP). Between 1982 and 1999, 58 patients received surgical treatment for PSP in our department. Twelve patients needed bilateral surgical intervention. At an average of 121 months after surgery (range, 16-231 months), the patients underwent follow-up assessments. Information was obtained on the basis of a questionnaire and from clinical examinations, including spirometry/body plethysmography and exercise testing with a bicycle ergometer. High-resolution computed tomography was used to identify postoperative changes of the lung apex. Forty-eight of 58 patients took part in the study, and all were found to be fully fit. High-resolution computed tomography gave evidence of new postoperative fibrocystic processes in 26 of the 31 affected apexes. One recurrence was observed (3.2%). Because apical resection cannot counteract pathogenetic mechanisms underlying parenchymal destruction and the formation of postoperative bullae among patients with a history of PSP, additional treatment of the apical pleura is necessary to prevent recurrences. Our results suggest that the physical fitness of patients with PSP can be completely restored postoperatively.

Fluid resuscitation preserves cardiac output but cannot prevent organ damage in a porcine model during 24 h of intraabdominal hypertension.

According to a previous study, a pathologically increased intraabdominal pressure (IAP) reduces cardiac output (CO) and results in medium- to high-grade organ damage in a porcine model of the abdominal compartment syndrome (ACS). The purpose of this study was to evaluate whether fluid resuscitation can preserve organ integrity together with CO. We examined 12 domestic pigs with a mean body weight of 48 kg. We used a CO2 pneumoperitoneum to increase the IAP to 30 mmHg in 6 animals, and the others served as control group. The investigation period was 24 h. In addition to a standard infusion regimen, Ringer's solution was infused to maintain CO at the level of control animals. Hemodynamic parameters (ITBV, EVLW, MAP, CVP), urine output, inspiratory pressure, as well as serum parameters (e.g., ALT, lipase, AP, lactate, creatinine) were recorded. In the end histological examination of liver, bowel, kidney, and lung was performed. CO, ITBV, EVLW, and urine output did not change when compared with control. Fluid intake was increased (P < 0.01) when compared with control (10,570 +/- 1,928 vs. 3,918 +/- 1,042 mL). CVP, MAP, and inspiratory pressure were increased. Serum parameters did not change. Acidosis occurred in the study group. Liver, bowel, kidney, and lung displayed mean- to high-grade damage (P < 0.01). Although extensive fluid resuscitation preserved CO, diuresis, and serum parameters in this previously described model of the ACS, organ damage occurred. In the clinical regard, these results support decompressive treatment in the presence of pathologically high IAP despite "normalized" parameters.

Factors influencing the estimation of extravascular lung water by transpulmonary thermodilution in critically ill patients.

OBJECTIVE: To investigate factors that may influence the estimation of extravascular lung water (EVLW) with a single (cold) indicator compared with assessment using two indicators (thermo-dye dilution). DESIGN: Post hoc analysis of an electronic hemodynamic database. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: Forty-eight critically ill patients monitored by the thermo-dye dilution technique in the postoperative period. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The EVLW was simultaneously assessed by the thermo-dye dilution technique (EVLWref) and estimated by transpulmonary thermodilution (EVLWest). EVLWref index ranged between 1 and 40 mL/kg (mean 10 +/- 7 mL/kg) and EVLWest between 2 and 39 mL/kg (mean 9 +/- 6 mL/kg). EVLWref was closely correlated (r = .96) with EVLWest. The mean difference (bias) between EVLWref and EVLWest was -0.5 +/- 1.9 mL/kg. The bias was not influenced by the weight, height, body surface area, body mass index, Pao2, intrathoracic blood volume, cardiac output, or dosage of vasoactive agents. In contrast, the bias was slightly but significantly influenced by EVLWref, Pao2/Fio2 ratio, tidal volume, and level of positive end-expiratory pressure. CONCLUSIONS: In our surgical intensive care unit population, the estimation of EVLW by transpulmonary thermodilution was influenced by the amount of EVLW, the Pao2/Fio2 ratio, the tidal volume, and the level of positive end-expiratory pressure. However, compared with the double indicator method, transpulmonary thermodilution estimation remained clinically acceptable even in patients with severe lung disease.

Intravascular volume depletion in a 24-hour porcine model of intra-abdominal hypertension.

BACKGROUND: The purpose of the study was to examine hemodynamic parameters and intravascular volume in a porcine model in the presence of intra-abdominal hypertension (IAH) lasting for 24 hours. METHODS: Twelve pigs (52.5 +/- 4.9 kg) were studied over a period of 24 hours. In six animals, the intra-abdominal pressure was increased to 30 mm Hg via carbon dioxide-pneumoperitoneum. The others served as controls. Using the double-indicator dilution technique, intrathoracic blood volume (ITBV), total circulating blood volume, and cardiac output (CO) were measured. Standard parameters (e.g., central venous pressure [CVP]), were also recorded. RESULTS: In the presence of IAH, ITBV and total circulating blood volume were significantly reduced to 55% and 67% of control values. CO decreased to 27% and CVP increased fourfold. CONCLUSION: IAH leads to significant intravascular volume depletion that is not reflected by the CVP. Assessment of CO and ITBV in the presence of a critically increased intra-abdominal pressure is therefore recommended.

Evaluation of two novel methods for the direct and continuous measurement of the intra-abdominal pressure in a porcine model.

OBJECTIVE: Intravesical bladder pressure (IVP) measurement is considered to be the gold standard for the assessment of intra-abdominal pressure (IAP). However, this method is indirect, discontinuous, and potentially infectious and relies on a physiological bladder function. This study evaluated two novel methods for direct, continuous IAP measurement. DESIGN AND SETTING: Experimental study in an animal research laboratory. SUBJECTS: 18 male domestic pigs. INTERVENTIONS: CO(2) was insufflated to increase the IAP to 30 mmHg for 18 and 24 h in six animals each. Another six animals served as controls. A piezoresistive (PRM) and an air-capsule (ACM) pressure measurement probe were placed intra-abdominally and of IAP was measured every 1 h (PRM/ACM) or every 2 h (IVP). The mean difference between insufflator readings and IAP values and limits of agreement (mean difference +/-2 SD) were calculated. MEASUREMENTS AND RESULTS: In the presence of applied pressure IVP and PRM remained significantly below insufflator readings while ACM values showed no difference. Mean difference (and limits of agreement) were 4.5 (-2.1 to 11.1 mmHg), 1.6 (-8.0 to 11.2 mmHg), and 0.5 (-4.5 to 5.4 mmHg) for IVP, PRM, and ACM. The mean measurement-to-measurement drift of the ACM values was 9.0+/-10.2 mmHg. CONCLUSIONS: In this model agreement of PRM and ACM with insufflator readings was comparable to IVP. As both methods may be advantageous regarding continuous straightforward measurement of IAP, the employment in further experimental and clinical investigations is suggested.