Human intraperitoneal microdialysis: increased lactate/pyruvate ratio suggests early visceral ischaemia. A pilot study

The Significance of Blood and Peritoneal Fluid Biochemical Markers in Identifying Early Anastomotic Leak following Colorectal Resection-Findings from a Single-Center Study

Background and Objectives: The aim of our study was to evaluate the value of leukocyte, C reactive protein (CRP), procalcitonin, lactate, and carcinoembryonic antigen (CEA) in blood and peritoneal fluid in early recognition of anastomotic leak (AL) after colorectal resections. Materials and Methods: Our pilot prospective cohort study was conducted at the abdominal surgery department at University Medical Center Ljubljana. A total of 43 patients who underwent open or laparoscopic colorectal resection because of benign or malignant etiology were enrolled. All of the patients had primary anastomosis without stoma formation. Results: Three patients in our patient group developed AL (7%). We found a statistically significant elevation of serum lactate levels in patients that developed AL compared to those who did not but noted no statistically relevant difference in the blood or peritoneal fluid levels of other biochemical markers. Conclusions: Elevated lactate levels may be considered a promising biomarker for the early diagnosis of AL, but more research on bigger patient groups is warranted.

Fully covered self‐expandable metal stent placed over a stapled colon anastomosis in an animal model: A pilot study of colon metabolism over the stent

Background and Aim

Anastomotic leakage (AL) in colorectal resection and primary anastomosis is a common and feared complication. Fully covered self‐expandable metal stents (FCSEMSs) have been used for the treatment of AL. It is still unknown whether FCSEMSs affect anastomosis healing negatively by causing ischemia. In an animal study, we investigated the metabolic effects over a FCSEMS covering a stapled colon anastomosis.

Methods

Seven pigs were investigated using microdialysis after laparotomy, colon resection, and anastomosis with stent placement. Measurements were done at the proximal and distal ends of the anastomosis and at a reference catheter placed at the small intestine. Measurements of glucose, pyruvate, lactate, glycerol, and the lactate/pyruvate ratio (L/P) were carried out.

Results

Lactate and L/P were significantly higher at the oral part of the anastomosis, while glucose showed a small declining tendency. At the distal part of the anastomosis, glucose decreased significantly after the resection but did not reach zero. Lactate increased significantly whereas L/P increased only slightly. Glycerol levels were stable.

Conclusion

Colon resection caused initially hypermetabolism in the intestinal ends next to the resection site. This hypermetabolism neither deteriorated nor turned into ischemia during the initial postoperative course, but the start of hypoxemia could not be excluded during the study and after the placement of an FCSEMS.

Systemic inflammatory response in robot-assisted and laparoscopic surgery for colon cancer (SIRIRALS): study protocol of a randomized controlled trial

Background

Robot-assisted surgery is being increasingly adopted in treating colorectal cancer, and the transition from laparoscopic surgery to robot-assisted surgery is a trend. The evidence of the benefits of robot-assisted surgery is sparse. However, findings are associated with improved patient-related outcomes and overall morbidity rates compared to laparoscopic surgery. This induction is unclear, considering both surgical modalities are characterized as minimally invasive. This study aims to evaluate the systemic and peritoneal inflammatory stress response induced by robot-assisted surgery compared with laparoscopic surgery for elective colon cancer resections in a prospective, randomized controlled clinical trial.

Methods

This study is a single-centre randomized controlled superiority trial with 50 colon cancer participants. The primary endpoint is the level of systemic inflammatory response expressed as serum C-reactive protein (CRP) and interleukin 6 (IL-6) levels between postoperative days one and three. Secondary endpoints include (i) levels of systemic inflammation in serum expressed by a panel of inflammatory and pro-inflammatory cytokines measured during the first three postoperative days, (ii) postoperative surgical and medical complications (30 days) according to Clavien-Dindo classification and Comprehensive Complication Index, (iii) intraoperative blood loss, (iv) conversion rate to open surgery, (v) length of surgery, (vi) operative time, (vii) the number of harvested lymph nodes, and (viii) length of hospital stay. The exploratory endpoints are (i) levels of peritoneal inflammatory response in peritoneal fluid expressed by inflammatory and pro-inflammatory cytokines between postoperative day one and three, (ii) patient-reported health-related quality of recovery-15 (QoR-15), (iii) 30 days mortality rate, (iv) heart rate variability and (v) gene transcript (mRNA) analysis.

Discussion

To our knowledge, this is the first clinical randomized controlled trial to clarify the inflammatory stress response induced by robot-assisted or laparoscopic surgery for colon cancer resections.

Trial registration This trial is registered at Clinicaltrials.gov (Identifier: NCT04687384) on December, 29, 2020, Regional committee on health research ethics, Region of Southern Denmark (N75709) and Data Protection Agency, Hospital Sønderjylland, University Hospital of Southern Denmark (N20/46179).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-021-01355-4.

Predictive and Diagnostic Biomarkers of Anastomotic Leakage: A Precision Medicine Approach for Colorectal Cancer Patients

Development of an anastomotic leak (AL) following intestinal surgery for the treatment of colorectal cancers is a life-threatening complication. Failure of the anastomosis to heal correctly can lead to contamination of the abdomen with intestinal contents and the development of peritonitis. The additional care that these patients require is associated with longer hospitalisation stays and increased economic costs. Patients also have higher morbidity and mortality rates and poorer oncological prognosis. Unfortunately, current practices for AL diagnosis are non-specific, which may delay diagnosis and have a negative impact on patient outcome. To overcome these issues, research is continuing to identify AL diagnostic or predictive biomarkers. In this review, we highlight promising candidate biomarkers including ischaemic metabolites, inflammatory markers and bacteria. Although research has focused on the use of blood or peritoneal fluid samples, we describe the use of implantable medical devices that have been designed to measure biomarkers in peri-anastomotic tissue. Biomarkers that can be used in conjunction with clinical status, routine haematological and biochemical analysis and imaging have the potential to help to deliver a precision medicine package that could significantly enhance a patient's post-operative care and improve outcomes. Although no AL biomarker has yet been validated in large-scale clinical trials, there is confidence that personalised medicine, through biomarker analysis, could be realised for colorectal cancer intestinal resection and anastomosis patients in the years to come.

Monitoring of patients with microdialysis following pancreaticoduodenectomy-the MINIMUM study: study protocol for a randomized controlled trial

BACKGROUND

Postoperative pancreatic fistula after pancreatoduodenectomy is a much-feared complication associated with substantial mortality and morbidity. The current standard for diagnosing postoperative pancreatic fistula, besides routine clinical examination, include radiological examinations, analysis of pancreatic drain amylase activity, and routine blood samples. Another promising method is by intraperitoneal microdialysis to monitor intraperitoneal metabolites measured at the pancreaticojejunostomy, thereby detecting what occurs locally, before chemical events can be reflected as measurable changes in systemic blood levels.

METHODS

The MINIMUM study is a prospective, randomized, controlled, single center enrolling 200 patients scheduled for open pancreatoduodenectomy comparing the microdialysis method to the "standard of care." Half of the included patients will be randomized to receive an intraperitoneal microdialysis catheter implanted at the end of surgery and will be monitored by microdialysis as an additional monitoring tool. The other half of the patients will not receive a microdialysis catheter and will be monitored according to the current standard of care. The primary objective is to evaluate if the microdialysis method can reduce the total length of stay at the hospital. Secondary endpoints are the frequency of complications, length of stay at the hospital at our institution, catheter malfunction, number of infections and bleeding episodes caused by the microdialysis catheter, patient-reported quality of life and pain, and cost per patient undergoing pancreatoduodenectomy. The patients will be randomized in a 1:1 ratio.

DISCUSSION

Intraabdominal microdialysis could potentially reduce morbidity and mortality after pancreatoduodenectomy. Furthermore, there is a great potential for shortening the in-hospital length of stay and reducing the financial aspect considerably. This study may potentially open the possibility for using microdialysis as standard monitoring in patients undergoing pancreatoduodenectomy. The hypothesis is that the microdialysis method compared to "standard care" will reduce the total length of hospital stay.

TRIAL REGISTRATION

Clinicaltrials.gov ( NCT03631173 ). Registered on 7 September 2018 under the name: "Monitoring of patients With Microdialysis Following Pancreaticoduodenectomy". Based on protocol version 19-1, dated 15th January 2019.

Results of intraperitoneal microdialysis depend on the location of the catheter

BACKGROUND AND OBJECTIVE

Intraperitoneal microdialysis was recently described as a method for early detection of visceral ischemia. The method seems safe and accurate. The intra-abdominal catheter used may imply variations in results depending on the location of the catheter. The aim of the study was to investigate possible differences in metabolic parameters obtained depending on various locations of the intra-abdominal catheter, compared with using the subcutaneous reference catheter.

METHOD

After right-sided hemicolectomy in 12 patients, three catheters were placed and fixed intraperitoneally: one at the anastomosis, one in the omentum and one embedded between the small intestinal loops. A subcutaneous catheter placed in the pectoral region was used as reference. Analyses of lactate/pyruvate ratio and glucose and glycerol levels were done during a period of 45 hours postoperatively.

RESULTS

Lactate/pyruvate ratio decreased numerically at all three intraperitoneal locations during the study while the subcutaneous lactate/pyruvate ratio increased slightly. Significant differences between intraperitoneal and subcutaneous locations were found as well as differences between the three intraperitoneal locations. Highest values of the lactate/pyruvate ratio were found at the anastomosis, while the widest range was found at the small intestine. Subcutaneous glucose levels were lower while glycerol levels were higher compared with intraperitoneal values.

CONCLUSIONS

In evaluating postoperative metabolism, intraperitoneal microdialysis is influenced by the location of the microdialysis catheter. The same pattern is, however, recorded over time. The juxta-anastomotic region and the small intestinal loop area seem to be the most reasonable locations for measurements.

Early Metabolic and Inflammatory Intraperitoneal Changes After Rectum Perforation

Purpose

Anastomotic leakage (AL) is the most dreaded complication in rectal surgery. It has a great impact on postoperative morbidity and mortality. This animal model, in which we have studied postoperative metabolic and inflammatory changes, is designed to imitate an AL.

Methods

Twelve pigs were randomized into 2 groups. In the experimental group, an iatrogenic rectal perforation was performed, with the control group having a sham operation. The 2 groups were followed for 10 hours after operation with regard to vital parameters, arterial lactate, and cytokines interleukin (IL) 1, IL6, and IL10 in the blood and intraperitoneally. Intraperitoneal microdialysis analyses of glucose, lactate, glycerol, and pyruvate were performed and the lactate/pyruvate ratio was calculated.

Results

Glucose levels were lower in the experimental group after 4 hours. After 7 hours, lactate and lactate/pyruvate ratio was higher in the experimental group. At the same time intraperitoneal cytokines IL6 and IL10 were higher in the experimental group. Blood samples showed higher IL6 after 7 hours in the experimental group.

Conclusion

In this study, several significant differences between the groups in metabolic and inflammatory values were detected. Further clinical studies are recommended to evaluate the importance of intraperitoneal metabolic and inflammatory analyses as a diagnostic tool for early identification of an AL.

Detection of early anastomotic leakage by intraperitoneal microdialysis after low anterior resection for rectal cancer: a prospective cohort study

AIM

Anastomotic leakage (AL) is a common and serious complication following sphincter-preserving surgery for rectal cancer. Early detection and intervention can improve clinical outcomes. The aim of this prospective cohort study was to compare intraperitoneal microdialysis with a clinical scoring system for early detection of AL.

METHOD

A microdialysis catheter was anchored near the anastomosis at low anterior resection (LAR) for rectal cancer. Peritoneal fluid samples were analysed (lactate, pyruvate, glucose and glycerol concentration) 4-hourly and compared with a daily clinical leak score (DULK = Dutch leakage). At day 7 a pelvic CT with rectal contrast enema was performed to establish if there had been a radiological leak.

RESULTS

In this two-centre study, 129 patients [median age 65 (26-82) years; 60.5% male] underwent LAR. The leak rate was 27% (grade A, n = 11; grade B, n = 12; grade C, n = 12). Receiver operator characteristic analysis demonstrated a lactate cut-off value of 9.8 mm and had 77% sensitivity, 82% specificity, 78% accuracy, a positive predictive value (PPV) of 58, a negative predictive value (NPV) of 88 (CI 79-94) and an area under the curve (AUC) of 0.9 for AL. This compared with a clinical score ≥ 4, which had 57% sensitivity, 79% specificity, 71% accuracy, a PPV of 46, a NPV of 82 and an AUC of 0.7 for AL. The mean day for a positive test when using delta lactate ≥ 6.3 mm was 1.6 days and for leak score ≥ 4 it was 3.3 days (NS).

CONCLUSION

When AL occurs, intraperitoneal lactate concentration increases over time, and at a certain cut-off has a higher sensitivity, specificity, accuracy, PPV and NPV than a clinical scoring system.

Peritoneal microdialysis as a tool for detecting anastomotic leakage in patients after left-side colon and rectal resection. A systematic review

OBJECTIVE

The objective was to evaluate peritoneal microdialysis in the detection of clinical anastomotic leakage after left-sided colon and rectal resection through a systematic review.

METHODS

A systematic review (PRISMA guidelines) based on a systematic search through PubMed, Cochrane Library, and EMBASE (1 February 2017) was performed. Methodological index of non-randomised studies score was selected to assess the methodological quality. Patient demographics and raw data for intraperitoneal microdialysis concentrations of glucose, lactate, glycerol and pyruvate for 5 d postoperative were obtained from the respective study groups.

RESULTS

Ten studies with a total of 128 patients were included. Thirty (23%) patients developed clinical anastomotic leakage. The area under the curve for intraperitoneal lactate concentration was significant higher in patients with anastomotic leakage (58.2; 95% CI 39.2, 77.2) compared with the no leakage group (41.0; 95% CI 35.2, 46.1; p = .007). Receiver operating characteristic curve analysis of the maximum measured lactate concentration demonstrated 25% sensitivity, 88% specificity and 74% accuracy for AL at a cut-off value of 9.8 mmol/L. The odds ratio for a 5 mmol/L increase in lactate in relation to the risk of AL was 2.9 (CI 1.1, 8.0).

CONCLUSIONS

Increased intraperitoneal lactate concentration within the first 5 d postoperative was significantly associated with clinical anastomotic leakage, but with low predictive values. The microdialysis method is not yet ready for clinical implication before large prospective studies have defined cut off values for a biologic marker in the setting of a clear definitions of leakage.

Microdialysis in Postoperative Monitoring of Gastrointestinal Organ Viability: A Systematic Review

BACKGROUND

Microdialysis is a technique for continuous measurement of extracellular substances. It may be used to monitor tissue viability. The clinical implications of using microdialysis as a tool in gastrointestinal surgery have yet to be defined. The aim of the present study was to evaluate the clinical significance of microdialysis with special attention to different markers measured to predict the clinical outcome of surgical patients.

METHODS

Embase, MEDLINE, and the Cochrane Library were searched systematically for human studies written in English. Study selection, data extraction, and quality assessment were performed independently by two authors. We included studies in which the microdialysis technique was used for postoperative monitoring of patients undergoing gastrointestinal surgery. To be eligible, studies had to compare patients with and without postoperative complications.

RESULTS

Twenty-six studies were included in this review. MINORS score ranged from 3 to 12 (median 10.5). Most studies showed that levels of biomarkers obtained by microdialysis correlated with the postoperative clinical course. Lactate, pyruvate, glucose, and glycerol were the most frequently measured biomarkers. Several studies found that changes in biomarkers in complicated patients preceded symptoms of complications and/or changes in conventional paraclinical methods of postoperative monitoring.

CONCLUSIONS

Studies show that microdialysis may have the potential to become a tool in postoperative surveillance of surgical patients. Larger randomized studies are needed to define the clinical implications of microdialysis.

Splanchnic Circulation and Intraabdominal Metabolism in Two Porcine Models of Low Cardiac Output

The impact of acute cardiac dysfunction on the gastrointestinal tract was investigated in anesthetized and instrumented pigs by sequential reductions of cardiac output (CO). Using a cardiac tamponade (n = 6) or partial inferior caval vein balloon inflation (n = 6), CO was controllably reduced for 1 h each to 75% (CO_75%), 50% (CO_50%), and 35% (CO_35%) of the baseline value. Cardiac output in controls (n = 6) was not manipulated and maintained. Mean arterial pressure, superior mesenteric arterial blood flow, and intestinal mucosal perfusion started to decrease at CO_50% in the intervention groups. The decrease in superior mesenteric arterial blood flow was non-linear and exaggerated at CO_35%. Systemic, venous mesenteric, and intraperitoneal lactate concentrations increased in the intervention groups from CO_50%. Global and mesenteric oxygen uptake decreased at CO_35%. In conclusion, gastrointestinal metabolism became increasingly anaerobic when CO was reduced by 50%. Anaerobic gastrointestinal metabolism in low CO can be detected using intraperitoneal microdialysis.

Critical evaluation of colon submucosal microdialysis in awake, mobile rats

Sensors able to record large bowel physiology and biochemistry in situ in awake rodents are lacking. Microdialysis is a mini-invasive technique that may be utilized to continuously deliver or recover low-molecular substances from various tissues. In this experiment we evaluated the feasibility of in vivo microdialysis to monitor extracellular fluid chemistry in the descending colon submucosa of conscious, freely moving rodents. Following surgical implantation of a microdialysis probe, male Wistar rats were housed in metabolic cages where they were analgized and clinically followed for four days with free access to standard diet and water. To assess local microcirculation and probe function, glucose, lactate, glucose-to-lactate ratio and urea clearance were determined in the dialysates from the three postoperative days with focus on the final 24-h period. In an attempt to mitigate the expected tissue inflammatory response, one group of animals had the catheters perfused with 5-aminosalicylic acid-enriched medium with final concentration 1 μmol/L. For verification of probe position and the assessment of the surrounding foreign body reaction, standard histological and immunohistochemical methods were employed. Microdialysis of rat gut is associated with considerable technical challenges that may lead to the loss of probe function and high drop-out rate. In this setting, limited data did not allow to draw any firm conclusion regarding local anti-inflammatory effectiveness of 5-aminosalicylic acid perfusion. Although intestinal microdialysis may be suitable for larger anesthetized animals, low reproducibility of the presented method compromises its routine experimental use in awake and freely moving small-sized rodents.

Intraperitoneal lactate/pyruvate ratio and the level of glucose and glycerol concentration differ between patients surgically treated for upper and lower perforations of the gastrointestinal tract: a pilot study

BACKGROUND

Secondary peritonitis is a condition associated with high morbidity and mortality. Continuous postoperative monitoring of patients to ensure timely intervention to treat complications without delay is important for survival and outcome. We aimed to (1) investigate potential differences in postoperative intraperitoneal biomarker levels between patients with upper and lower gastrointestinal tract lesion, and (2) compare postoperative biomarker levels between complicated and uncomplicated patients.

METHODS

We included a total of 15 consecutive patients operated for upper (n = 7) and lower (n = 8) gastrointestinal tract perforation. We registered postoperative complications during a 30 days follow up-period. Complications were defined as intraabdominal complications, septic shock, and mortality. 5 patients were complicated. A microdialysis catheter was placed intraperitoneally in each patient. Samples were collected every 4th hour for up to 7 postoperative days. Samples were analysed for concentrations of glucose, lactate, pyruvate and glycerol.

RESULTS

Microdialysis results showed that patients with upper gastrointestinal tract lesions had significantly higher levels of postoperative intraperitoneal glucose and glycerol concentrations, as well as lower lactate/pyruvate ratios and lactate/glucose ratios. In the group with perforation of the lower gastrointestinal tract, those patients with a complicated course showed lower levels of postoperative intraperitoneal glucose concentration and glycerol concentration and higher lactate/pyruvate ratios and lactate/glucose ratios than those patients with an uncomplicated course.

CONCLUSION

Patients with upper and lower gastrointestinal tract lesions showed differences in postoperative biomarker levels. A difference was also seen between patients with complicated and uncomplicated postoperative courses.

Integrated approach to colorectal anastomotic leakage: Communication, infection and healing disturbances

Colorectal anastomotic leakage (CAL) remains a major complication after colorectal surgery. Despite all efforts during the last decades, the incidence of CAL has not decreased. In this review, we summarize the available strategies regarding prevention, prediction and intervention of CAL and categorize them into three categories: communication, infection and healing disturbances. These three major factors actively interact during the onset of CAL. We aim to provide an integrated approach to CAL based on its etiology. The intraoperative air leak test, intraoperative endoscopy, radiological examinations and stoma construction mainly aim to detect and to prevent communication between the intra- and extra-luminal content. Other strategies including postoperative drainage, antibiotics, and infectious-parameter evaluation are intended to detect and prevent anastomotic or peritoneal infection. Most currently available interventions for CAL focus on the control of communication and infection, while strategies targeting the healing disturbances such as lifestyle changes, oxygen therapy and evaluation of metabolic biomarkers still lack wide clinical application. This simplified categorization may contribute to an integrated understanding of CAL. We strongly believe that this integrated approach should be taken into consideration during clinical practice. An integrated approach to CAL could contribute to a better understanding of the etiology of CAL and eventually better patient outcome.

Intraperitoneal microdialysis in the postoperative surveillance of infants undergoing surgery for congenital abdominal wall defect: A pilot study

PURPOSE

This study aims to investigate the safety and clinical implication of intraperitoneal microdialysis (MD) in newborns operated on for congenital abdominal wall defect.

PATIENTS AND METHODS

13 infants underwent intraperitoneal microdialysis (9 with gastroschisis and 4 with omphalocele). MD samples were collected every four hours and the concentrations of lactate, glycerol, glucose and pyruvate were measured. The results of MD were compared between the group of infants with gastroschisis and the group with omphalocele. The duration of parenteral nutrition and tube feeding were compared for high and low levels of intraperitoneal lactate, glycerol, and glucose and lactate/pyruvate ratio respectively. High and low levels were defined as above or below the median value on day one.

RESULTS

Results from intraperitoneal MD showed a significantly higher mean lactate concentration in the group of infants with gastroschisis compared with the group of infants with omphalocele. The median values were 6.19 mmol/l and 2.19 mmol/l, respectively (P=0.006). The results from MD in the six infants in the gastroschisis group who underwent secondary closure after Silo treatment were similar to those who underwent primary closure. None of the infants with omphalocele received parenteral nutrition whereas all of the infants with gastroschisis did. There was no significant difference in duration of parenteral nutrition or tube feeding, respectively, when comparing the gastroschisis children with high versus low intraperitoneal lactate values. Placement of the MD catheter in the intraperitoneal cavity was feasible and without any major complications.

CONCLUSION

Intraperitoneal MD is a safe procedure and an applicable method in surveillance of inflammatory changes in the peritoneal cavity in infants after operation for congenital abdominal wall defect. The true clinical value in infants with congenital wall defect remains unknown.

Does tissue ischemia actually contribute to leak after sleeve gastrectomy? An experimental study

BACKGROUND

Staple line leak, although rare, is among the most common postoperative complications after sleeve gastrectomy (SG) and usually occurs in the gastroesophageal (GE) junction. Increased intragastric pressure, regional ischemia, and technical failure of stapling devices have been reported as the main risk factors of postoperative leak. The aim of this study was to evaluate the impact of ischemia and intraluminal pressure in leak appearance.

METHODS

Landrace swine (n = 12) were subjected to SG and total gastrectomy subsequently. Lactic acid, glycerol, and pyruvate were measured by microdialysis in GE junction and pylorus before and nine times after operation, and lactate/pyruvate (L/P) ratio was calculated as well. Moreover, ex vivo air was insufflated inside the tubularized stomach till a rupture of the staple line occurs. Maximum air pressure reached and location of rupture were recorded.

RESULTS

Increase of lactic acid and L/P ratio were demonstrated in GE junction measurements; however, when the measurements between GE junction and pylorus were compared, no statistically significant differences were found, with the exception of a slightly increased lactate concentration in pylorus in the midst of measurements. The maximum air pressure recorded varied from 3 to 75 mmHg (mean 24.5 mmHg) and the majority of ruptures (n = 8) occurred in GE junction. In one of them, clip displacement was noticed.

CONCLUSIONS

No evidence of increased ischemia in GE junction compared to pylorus was recorded. Increased intraluminal pressure and stapling malfunction may play the most important role in leak appearance.

Ischemic injury of the liver in a porcine model of cardiac death assessed by in vivo microdialysis

This study aims to evaluate the ischemic injury of the liver in a porcine model of cardiac death assessed by in vivo microdialysis. A porcine model of cardiac death was established by the suffocation method. Metabolic indicators were monitored using the microdialysis technique during warm ischemia time (WIT) and cold ischemia time (CIT). Pathological changes in ischemic-injured livers were observed by haematoxylin-eosin staining. The predictive values of biochemical parameters regarding the liver donor were evaluated by receiver operating characteristic curve analysis. All statistical analyses were conducted using the SPSS 18.0 software (SPSS Inc, Chicago, Illinois, USA). The degree of warm ischemic injury of the livers increased with prolonged WIT. Serum glucose, glycerol, pyruvate, lactic acid levels and lactate-to-pyruvate (L/P) ratio increased gradually during WIT. Results from Pearson correlation analyses indicated that serum lactate level and L/P ratio were positively associated with the degree of warm ischemic injury of the livers. The degree of cold ischemic injury of the livers gradually increased after 12 h CIT. Serum glucose, lactic acid and L/P ratio achieved a peak after 6-8 h of CIT, but gradually decreased with prolonged CIT. The peak of glycerol occurred after 8 h of CIT, while no changes were found with prolonged CIT. Serum pyruvate level exhibited an increasing trend after 12 h CIT. Our results confirmed that serum glucose and lactate levels were negatively correlated with cold ischemic injury of the liver. However, serum glycerol and pyruvate levels showed positive correlations with cold ischemic injury of the liver. The liver donor was unavailable after 30 min WIT and 24 h CIT. The cut-off value of serum lactate level for warm ischemic injury of the livers was 2.374 with a sensitivity (Sen) of 90 % and specificity (Spe) of 95 %; while the L/P radio was 0.026 (Sen = 80 %, Spe = 83 %). In addition, the cut-off values of serum glucose, lactate, glycerol and pyruvate levels for cold ischemic injury of the livers were 0.339 (Sen = 100 %, Spe = 77 %), 1.172 (Sen = 100 %, Spe = 61 %), 56.359 (Sen = 100 %, Spe = 65 %) and 0.020 (Sen = 100 %, Spe = 67 %), respectively. Our findings provide empirical evidences that serum glucose, lactate levels and L/P ratio may be good indicators for the degree of warm ischemic injury of the livers after cardiac death; while serum glucose, lactate, glycerol and pyruvate levels may be important in predicting cold ischemic injury.

Pitfalls in microdialysis methodology: an in vitro analysis of temperature, pressure and catheter use

Microdialysis of macromolecules within the brain provides a unique insight into physiological and pathological processes occurring within an otherwise inaccessible cranial cavity. The physically restricted nature of the intracranial compartment may present wider variations of pressure and temperature than those experienced in the rest of the body. In this study we attempted to determine the effect of variation of temperature and pressure on a cytokine recovery in vitro. Our results demonstrate that the wide variation of recovery attributable to different catheter use outweighed any effects caused by temperature or pressure. Investigators performing cytokine microdialysis using the CMA 71 system should be aware of the wide inter-catheter variability and potential effects of temperature on recovery.

Mediastinal microdialysis in the diagnosis of early anastomotic leakage after resection for cancer of the esophagus and gastroesophageal junction

BACKGROUND

Anastomotic leakage (AL) after gastroesophageal resection for cancer is a serious complication. The aim was to evaluate mediastinal microdialysis in the detection of AL before clinical symptoms.

METHODS

Sixty patients were included. Samples were collected every 4 hours in the 1st 8 postoperative days and analyzed for several metabolites.

RESULTS

Forty-four patients had an uncomplicated postoperative recovery, 7 developed anastomotic-related complications, and 5 developed major nonanastomotic-related complications. Six patients were excluded (early catheter malfunction and reoperation). Logistic regression model on several metabolites demonstrated a 100% sensitivity, specificity, and positive and negative predictive values regarding the diagnosis of anastomotic complications within postoperative day 7. However, as independent markers, none of the measured metabolites were able to predict AL.

CONCLUSION

The diagnosis of anastomotic-related complications before clinical symptoms seemed possible by mediastinal microdialysis, but the diagnosis should be based on an interpretation of several metabolic events.

Mode of action of cupping--local metabolism and pain thresholds in neck pain patients and healthy subjects

OBJECTIVES

Cupping worldwide has been part of traditional medicine systems and is in the western world used as CAM therapy mainly for treating pain syndromes. The mode of action is up to now unclear. In order to investigate its mechanism we measured in parallel metabolic changes in the tissue under the cupping glass and pressure pain thresholds.

DESIGN AND INTERVENTIONS

In 12 volunteers (6 healthy subjects and 6 patients with chronic neck pain) a microdialysis system was implanted subcutaneously on both sides (left and right) above the trapezius muscle. After baseline measures cupping was performed at one randomly selected side (left or right), the other side served as control. Every 20 min during baseline measures and for 280 min after cupping, microdialysis probes for detection of lactate, pyruvate, glucose and glycerin were taken. In addition, pain thresholds were measured before and after cupping with algometry.

RESULTS

Cupping resulted in a strong increase of lactate (beginning 160 min after cupping until the end of the measurements) and the lactate/pyruvate ratio, indicating an anaerobe metabolism in the surrounding tissue. Baseline pain thresholds were non-significantly lower in neck pain patients compared to healthy controls and slightly increased immediately after cupping (p<0.05 compared to baseline close to the area of cupping in healthy subjects and on the foot in neck pain patients). After 280 min no more significant changes of pain thresholds were detected.

CONCLUSIONS

Cupping induces >280 min lasting anaerobe metabolism in the subcutaneous tissue and increases immediate pressure pain thresholds in some areas.

Validation of intraluminal and intraperitoneal microdialysis in ischemic small intestine

BACKGROUND

We sought to define the sensitivity and specificity of intraperitoneal (IP) and intraluminal (IL) microdialysate metabolites in depicting ex vivo small intestinal total ischemia during GI-tract surgery. We hypothesized that IL as opposed to IP microdialysis detects small intestinal ischemia with higher sensitivity and specificity.

METHODS

IL and IP microdialysate lactate, pyruvate, glucose and glycerol were analysed from small intestine of pancreaticoduodenectomy patients before and after occluding the mesenteric vasculature and routine resection of a segment of small intestine. Ex vivo time sequences of microdialysate metabolites were described and ROC analyses after 0-30, 31-60, 61-90 and 91-120 minutes after the onset ischemia were calculated.

RESULTS

IL lactate to pyruvate ratio (L/P ratio) indicated ischemia after 31-60 minutes with 0.954 ROC AUC (threshold: 109) in contrast to IP L/P (ROC AUC of 0.938 after 61-90 minutes, threshold: 18). At 31-60 minutes IL glycerol concentration indicated ischemia with 0.903 ROC AUCs (thresholds: 69 μmol/l). IP glycerol was only moderately indicative for ischemia after 91-120 minutes with 0,791 ROC AUCs (threshold 122 μmol/l). After 31-60 minutes IL and IP lactate to glucose ratios (L/G ratio) indicated ischemia with 0.956 and 0,942 ROC AUCs (thresholds: 48,9 and 0.95), respectively.

CONCLUSIONS

The results support the hypothesis that intraluminal application of microdialysis and metabolic parameters from the small intestinal lumen indicate onset of ischemia earlier than intraperioneal microdialysis with higher sensitivity and specificity.

Identification of anastomotic leakage after colorectal surgery using microdialysis of the peritoneal cavity

BACKGROUND

Early detection of colorectal anastomotic leakage (AL) may lead to better outcome. AL may be preceded by change in local metabolism and local ischaemia. Microdialysis of the peritoneal cavity is able to measure these changes in real-time and is minimally invasive. The aim of this prospective cohort study was to compare values of intraperitoneal microdialysis in patients with AL to patients without AL after open and laparoscopic colorectal surgery.

METHODS

Twenty-four patients underwent surgery for left-sided, sigmoid and rectal carcinoma with creation of an anastomosis. Intraoperatively a juxta-anastomotical intraperitoneal and subcutaneous microdialysis catheter was placed. The levels of lactate, pyruvate, glucose and glycerol in the dialysate were measured every 4 h during the first 5 post-operative days, and mean values and area under the curve (AUC) were calculated.

RESULTS

Mortality was 0 % and morbidity 38 %. In 3 patients (17 %), AL occurred. In patients with AL, post-operative peritoneal lactate level was 3.2 mmol/l (standard deviation (SD) 0.9) for patients without AL, compared to 4.4 mmol/l (SD 1.5) in case of AL (p = 0.03 for AUC). Intraperitoneal glucose levels were 8.1 mmol/l (SD 1.3), compared to 7.8 mmol/l (SD 2.2) in the complicated course (ns for AUC). Mean intraperitoneal lactate/pyruvate-ratio was 19.2 (SD 3) after colorectal surgery without AL compared to 25 (SD 4.7) in case of AL (non-significant (ns) for AUC). No significant differences were observed between patients who underwent laparoscopic resection and those who underwent open resection.

CONCLUSIONS

Anastomotic leakage was preceded by a significantly higher AUC and mean value of lactate levels during the first 5 post-operative days. To identify cut-off values for clinical use, pooling of data is necessary.

Intra-peritoneal microdialysis and intra-abdominal pressure after endovascular repair of ruptured aortic aneurysms

OBJECTIVES

This study aims to evaluate intra-peritoneal (ip) microdialysis after endovascular aortic repair (EVAR) of ruptured abdominal aortic aneurysm (rAAA) in patients developing intra-abdominal hypertension (IAH), requiring abdominal decompression.

DESIGN

Prospective study.

MATERIAL AND METHODS

A total of 16 patients with rAAA treated with an emergency EVAR were followed up hourly for intra-abdominal pressure (IAP), urine production and ip lactate, pyruvate, glycerol and glucose by microdialysis, analysed only at the end of the study. Abdominal decompression was performed on clinical criteria, and decompressed (D) and non-decompressed (ND) patients were compared.

RESULTS

The ip lactate/pyruvate (l/p) ratio was higher in the D group than in the ND group during the first five postoperative hours (mean 20 vs. 12), p = 0.005 and at 1 h prior to decompression compared to the fifth hour in the ND group (24 vs. 13), p = 0.016. Glycerol levels were higher in the D group during the first postoperative hours (mean 274.6 vs. 121.7 μM), p = 0.022. The IAP was higher only at 1 h prior to decompression in the D group compared to the ND group at the fifth hour (mean 19 vs. 14 mmHg).

CONCLUSIONS

Ip l/p ratio and glycerol levels are elevated immediately postoperatively in patients developing IAH leading to organ failure and subsequent abdominal decompression.

Intraluminal intestinal microdialysis detects markers of hypoxia and cell damage in experimental necrotizing enterocolitis

BACKGROUND/PURPOSE

Necrotizing enterocolitis (NEC) represents one of the gravest complications in premature infants and carries significant morbidity and mortality. There is a great need for improved diagnostic methods to reduce the severity and incidence of NEC. The aim of the study was to investigate if intraluminal microdialysis can detect intestinal ischemia in newborn rats with induced experimental NEC.

METHODS

The studies were performed on 1-day-old Sprague-Dawley rat pups. Experimental NEC was induced using hypoxia/reoxygenation treatment. Microdialysis catheters were rectally inserted and placed in the rectosigmoid part of the colon. Microdialysate levels of glucose, lactate, pyruvate, and glycerol were measured. Intestinal specimens were collected at the end of the experiments for microscopic evaluation.

RESULTS

Intraluminal microdialysis revealed signs of intestinal hypoxia and cellular damage, with a marked increase of lactate and glycerol. Microscopic evaluation confirmed intestinal damage in the NEC group.

CONCLUSION

Intraluminal microdialysis can detect intestinal hypoxic stress and mucosal cell membrane decay in a rat model of NEC. Intestinal intraluminal microdialysis is easily accessible through the rectum and may be a useful noninvasive complement to other methods in the assessment of NEC.

Porcine model of hemorrhagic shock with microdialysis monitoring

BACKGROUND

A number of experimental protocols have been used to try to reproduce the clinical scenarios of hemorrhagic shock. The present study reports on an experimental swine model of controlled hemorrhagic shock that incorporates microdialysis monitoring for the evaluation of tissue perfusion and oxygenation. The aim of our study was to provide a reproducible, accurate, and reliable model for the testing and evaluation of therapeutic interventions in the area of hemorrhagic shock.

METHODS

Landrace swine (n = 8) were subjected to controlled hemorrhagic shock, with a mean arterial pressure of 35 ± 5 as the endpoint. Six more pigs were used as the control group. Microdialysis monitoring of the tissue lactate/pyruvate ratio was used. The mean arterial pressure, heart rate, hematocrit, hemoglobin, and lactate/pyruvate ratio measurements were obtained just before (phase A) and 30 min after (phase B) hemorrhage in the study group; the control group underwent the same measurements at the corresponding points.

RESULTS

The mean arterial pressure, hematocrit, and hemoglobin were lower (P < 0.05) in the study group than in the control group at phase B and compared with the values for the study group at phase A. Also, the lactate/pyruvate ratio and heart rate were greater (P < 0.05) in the study group than in control group at phase B and compared with the values for the study group at phase A.

CONCLUSIONS

This model of hemorrhagic shock is effective and correlates with the clinical parameters of tissue oxygenation, as documented by microdialysis.

Intestinal ischemia measured by intraluminal microdialysis

OBJECTIVE

To evaluate the possibility of detecting intestinal ischemia by intraluminal microdialysis and comparing the ileum and colon.

METHODS

The studies were performed on male Sprague-Dawley rats. In the first part of the study, microdialysis catheters were placed in the sigmoid part of the colon and in the subcutaneous adipose tissue. In the second part of the study, microdialysis catheters were placed in the lumen of the ileum and the colon. The infrarenal aorta was clamped proximal to the cranial mesenteric artery. Microdialysate levels of glucose, lactate, pyruvate and glycerol were measured. Intestinal specimens were removed at the end of the ischemic period for microscopic evaluation.

RESULTS

Intraluminal microdialysis could detect early signs of ischemic injury in the ileum, as well as in the colon, with a marked increase of lactate, lactate/pyruvate ratio and glycerol. The increased levels of intraluminal glycerol showed a positive correlation to prolonged ischemia and to higher degrees of intestinal damage.

CONCLUSION

Intraluminal measurement of glycerol is a good marker for intestinal ischemia. Intraluminal microdialysis in the colon is easily accessible through the rectum, and may prove to be a valuable clinical tool for diagnosing intestinal ischemia.

Early intraperitoneal metabolic changes and protease activation as indicators of pancreatic fistula after pancreaticoduodenectomy

BACKGROUND

Ischaemia and local protease activation close to the pancreaticojejunal anastomosis (PJA) are potential mechanisms of postoperative pancreatic fistula (POPF) formation. To provide information on the pathophysiology of POPF, intraperitoneal microdialysis was used to monitor metabolic changes and protease activation close to the PJA after pancreaticoduodenectomy (PD).

METHODS

In patients who underwent PD, intraperitoneal metabolites (glycerol, lactate, pyruvate and glucose) were measured by microdialysis, and lactate and glucose in blood were monitored, every 4 h for 5 days, starting at 12.00 hours on the day after surgery. Trypsinogen activation peptide (TAP) was measured in microdialysates as a marker of protease activation.

RESULTS

Intraperitoneal glycerol levels and the ratio of lactate to pyruvate were higher after PD and glucose levels were lower in seven patients who later developed symptomatic POPF than in eight patients with other surgical complications (OSC) and 33 with no surgical complications (NSC) (all P < 0·050). TAP was detected at a concentration greater than 0·1 µg/l in six of seven patients with POPF, two of eight with OSC and two of 33 with NSC. Intraperitoneal lactate concentrations were higher than systemic levels in all patients on days 1 to 5 after surgery (P < 0·001). In patients with POPF, high intraperitoneal lactate concentrations were observed without systemic hyperlactataemia.

CONCLUSION

Early in the postoperative phase, patients who later developed clinically significant POPF had higher intraperitoneal glycerol concentrations and lactate/pyruvate ratios, and lower glucose concentrations in combination with a TAP level exceeding 0·1 µg/l close to the PJA, than patients who did not develop POPF.

Intraperitoneal glycerol levels and lactate/pyruvate ratio: early markers of postoperative complications

OBJECTIVE

We have previously presented microdialysis findings of early intraperitoneal (i.p.) metabolic disturbances, mainly an increased lactate/pyruvate (l/p) ratio, in surgical patients developing postoperative complications. The aim of the present study was to investigate i.p. glycerol and l/p ratio after major surgery with and without complications.

MATERIAL AND METHODS

Sixty patients were followed with microdialysis for 48 h after major abdominal surgery, 44 patients without postoperative complications and 16 patients with major surgical complications. Intraperitoneal and subcutaneous (s.c.) measurements of glycerol, lactate, pyruvate and glucose were performed, and the l/p ratio was calculated.

RESULTS

Intraperitoneal glycerol was significantly lower in the complication group compared with the control group (64 vs. 94.6 μM; p = 0.0015), while the i.p. l/p ratio was significantly higher in the complication group compared with the control group (13.7 vs. 11.1; p = 0.0073).

CONCLUSIONS

In this study, i.p. glycerol levels were lower and i.p. l/p ratio was higher in the immediate postoperative period in a group of patients with complications. These results might indicate early i.p. disturbances in fat and carbohydrate metabolism in patients who later developed symptoms of postoperative major complications.

Intraperitoneal microdialysis in the postoperative surveillance after surgery for necrotizing enterocolitis: a preliminary report

BACKGROUND/PURPOSE

The aim of the present pilot study was to evaluate the safety and clinical application of intraperitoneal microdialysis (MD) in preterm infants operated on for necrotizing enterocolitis (NEC).

METHODS

Fourteen infants underwent MD. Two were excluded from analysis: 1 because of catheter malfunction and 1 because of fatal outcome immediately after surgery. The median MD time was 122 hours. Samples were collected every 4 hours, and the concentration of glucose, lactate, pyruvate, and glycerol was measured.

RESULTS

Three infants were reoperated on: 2 because of recurrent NEC and 1 because of ileal stenosis. In the 2 cases with recurrent NEC, changes in MD variables were found. Another had a prolonged postoperative period owing to diffuse fecal peritonitis. The values of MD normalized along with the return of bowel function. In 8 infants, the postoperative course was uncomplicated. The results of peritoneal MD in patients with complications were significantly different from those with an uncomplicated course (lactate/pyruvate ratio and glucose concentration).

CONCLUSION

Peritoneal MD is a safe procedure and an applicable method in surveillance of the metabolic and inflammatory changes in the peritoneal cavity after surgery for NEC. Larger series are needed to evaluate the clinical significance and use of this method.

Electrocautery causes more ischemic peritoneal tissue damage than ultrasonic dissection

BACKGROUND

Minimizing peritoneal tissue injury during abdominal surgery has the benefit of reducing postoperative inflammatory response, pain, and adhesion formation. Ultrasonic dissection seems to reduce tissue damage. This study aimed to compare electrocautery and ultrasonic dissection in terms of peritoneal tissue ischemia measured by microdialysis.

METHODS

In this study, 18 Wistar rats underwent a median laparotomy and had a peritoneal microdialysis catheter implanted in the left lateral sidewall. The animals were randomly assigned to receive two standard peritoneal incisions parallel to the catheter by either ultrasonic dissection or electrocautery. After the operation, samples of microdialysis dialysate were taken every 2 h until 72 h postoperatively for measurements of pyruvate, lactate, glucose, and glycerol, and ratios were calculated.

RESULTS

The mean lactate-pyruvate ratio (LPR), lactate-glucose ratio (LGR), and glycerol concentration were significantly higher in the electrocautery group than in the ultrasonic dissection group until respectively 34, 48, and 48 h after surgery. The mean areas under the curve (AUC) of LPR, LGR, and glycerol concentration also were higher in the electrocautery group than in the ultrasonic dissection group (4,387 vs. 1,639, P=0.011; 59 vs. 21, P=0.008; 7,438 vs. 4,169, P=0.008, respectively).

CONCLUSION

Electrosurgery causes more ischemic peritoneal tissue damage than ultrasonic dissection.

Gastric submucosal microdialysis in the detection of rat stomach ischemia--a comparison of the 3H2O efflux technique with metabolic monitoring

Microdialysis has been utilized for nutritive blood flow measurements, but both the advantages and disadvantages of various approaches have not been evaluated in parallel in the stomach yet. Our aim was to compare the (3)H(2)O efflux technique with biochemical monitoring during temporary celiac artery occlusion in anesthetized rats. Microdialysis probes were implanted in the gastric submucosa and perfused with (3)H(2)O; samples were analyzed for β-activity, glucose, lactate, pyruvate and glycerol. Gastric mucosa and plasma were subjected to morphometry and analysis of myeloperoxidase, total thiols and lactatdehydrogenase. The most dramatic responses to ischemia were observed in lactate/pyruvate and lactate/glucose (%) ratios (6.1-9.3×, p < 0.0001); the changes in (3)H(2)O efflux and glycerol were less pronounced (1.1-1.7×, p < 0.0001 and < 0.01, respectively). (3)H(2)O efflux correlated best with the lactate/glucose ratio and glucose alone (r = 0.693 and -0.681, respectively, p < 0.0001). A correlation was also found between plasma lactatdehydrogenase and relative glycerol release (r = 0.600, p < 0.05). Myeloperoxidase, lactatdehydrogenase and histology score were increased by ischemia/reperfusion (0.06-0.12 nkat g(-1), p < 0.05, 0.26-0.44 nkat g(-1), p < 0.05 and 1.79-2.33, p < 0.05, respectively), macroscopy and plasma thiols remained unchanged. Microdialysis is useful in monitoring gastric ischemia, metabolic monitoring being superior to the (3)H(2)O efflux technique. The results question the efficacy of the utilized model to produce standardized major gastric damage.

Complications but not obesity or diabetes mellitus have impact on the intraperitoneal lactate/pyruvate ratio measured by microdialysis

OBJECTIVE

Studies have shown a higher risk of postoperative complications in diabetic and obese patients. An increased intraperitoneal lactate/pyruvate ratio as measured by microdialysis has been reported before postoperative complications have been discovered. It is not known whether diabetes or obesity have any influence on the intraperitoneal metabolism (lactate/pyruvate ratio, glucose, glycerol) in relation to major abdominal surgery. The aim of this study was to investigate the postoperative intraperitoneal and subcutaneous carbohydrate and fat metabolism as measured by microdialysis in obese and diabetic patients after major abdominal surgery without postoperative complications.

MATERIAL AND METHODS

Seven obese patients (body mass index > 30 kg/m(2)) and six diabetic but non-obese patients were studied up to 48 h after major abdominal surgery and were compared with 31 non-diabetic, non-obese patients, all without complications. Microdialysis was performed to measure glucose, lactate, pyruvate and glycerol intraperitoneally and subcutaneously. The lactate/pyruvate ratio was calculated.

RESULTS

The lactate/pyruvate ratio did not differ between the groups. In the diabetic patients, glucose levels were higher intraperitoneally at both Days 1 and 2 compared to controls. Higher glycerol levels were found subcutaneously in obese patients at Day 2.

CONCLUSIONS

The lactate/pyruvate ratio does not increase intraperitoneally after non-complicated major abdominal surgery in diabetic and obese patients. Obese patients have increased release of free fatty acids and glycerol subcutaneously, while diabetic patients show higher glucose levels intraperitoneally than controls.

Regional changes in renal cortical glucose, lactate and urea during acute unilateral ureteral obstruction

OBJECTIVE

Acute unilateral ureteral obstruction (UUO) leads to changes in kidney function and metabolism. Microdialysis offers the possibility of topical analysis of changes in kidney metabolism. We applied microdialysis to the porcine kidney and evaluated its impact on gross kidney function. Furthermore, we investigated regional variations in renal interstitial fluid (RIF) glucose, lactate and urea during acute UUO.

MATERIAL AND METHODS

Eight anesthetized pigs were used. Microdialysis probes were inserted in the upper, middle and lower thirds of the left renal cortex and perfused with Ringer's chloride at a rate of 0.3 microl/min. Dialysates were fractionated for 30-min periods. Bilateral intrapelvic pressure, urinary output, urinary osmolality, the excretion fractions of sodium and potassium, renal blood flow and the glomerular filtration rate were measured. Subsequently, left-sided graded ureteral obstruction was initiated, using the kidney's own urine production as a counter-pressure.

RESULTS

The application of three microdialysis probes did not have any impact on kidney function. Ureteral obstruction decreased RIF glucose in the upper and lower thirds of the kidney, but not in the middle third. RIF lactate did not change. Interstitial urea increased in all regions of the kidney, but most markedly in the upper and lower poles.

CONCLUSIONS

Microdialysis is of potential value for assessing the renal interstitial milieu under different pathophysiological conditions. Ureteral obstruction resulted in regional differences in cortical metabolites, predominantly affecting the upper and lower poles.

Normal values and differences between intraperitoneal and subcutaneous microdialysis in patients after non‐complicated gastrointestinal surgery

OBJECTIVE

Visceral ischemia is an early event in the development of shock and organ failure. Microdialysis has been presented as a promising method for detection of visceral hypoxia and ischemia. The aim of this study was to investigate differences in the metabolic response measured by microdialysis between intraperitoneal and subcutaneous locations and to estimate normal values of lactate/pyruvate ratio, glucose and glycerol.

MATERIAL AND METHODS

Intraperitoneal and subcutaneous metabolic responses were compared regarding lacate/pyruvate ratio, glucose and glycerol, during 45 postoperative hours in 33 patients undergoing various non-complicated elective major gastrointestinal surgery.

RESULTS

Intraperitoneal lactate/pyruvate ratio started around 15 and decreased over time, while subcutaneous levels were stable around 9. Glucose levels were higher intraperitoneally and increased rapidly during the first 9 h to 8.6 mM, while the subcutaneous levels increased during 21 h to 7.5 mM. Intraperitoneal glycerol levels were stable around 100 microM, while subcutaneous values started around 230 microM and then increased.

CONCLUSIONS

In a non-complicated postoperative course the lactate/pyruvate ratio and glucose levels are higher intraperitoneally, suggesting a higher postoperative intraperitoneal metabolism. Glycerol levels are higher and increase subcutaneously, suggesting increased postoperative energy demand, particularly in the visceral organs, as being responsible for the lipolysis seen in the subcutaneous tissue.

Metabolism during anaesthesia and recovery in colic and healthy horses: a microdialysis study

BACKGROUND

Muscle metabolism in horses has been studied mainly by analysis of substances in blood or plasma and muscle biopsy specimens. By using microdialysis, real-time monitoring of the metabolic events in local tissue with a minimum of trauma is possible. There is limited information about muscle metabolism in the early recovery period after anaesthesia in horses and especially in the colic horse. The aims were to evaluate the microdialysis technique as a complement to plasma analysis and to study the concentration changes in lactate, pyruvate, glucose, glycerol, and urea during anaesthesia and in the recovery period in colic horses undergoing abdominal surgery and in healthy horses not subjected to surgery.

METHODS

Ten healthy university-owned horses given anaesthesia alone and ten client-owned colic horses subjected to emergency abdominal surgery were anaesthetised for a mean (range) of 230 min (193-273) and 208 min (145-300) respectively. Venous blood samples were taken before anaesthesia. Venous blood sampling and microdialysis in the gluteal muscle were performed during anaesthesia and until 24 h after anaesthesia. Temporal changes and differences between groups were analysed with an ANOVA for repeated measures followed by Tukey Post Hoc test or Planned Comparisons.

RESULTS

Lactate, glucose and urea, in both dialysate and plasma, were higher in the colic horses than in the healthy horses for several hours after recovery to standing. In the colic horses, lactate, glucose, and urea in dialysate, and lactate in plasma increased during the attempts to stand. The lactate-to-pyruvate ratio was initially high in sampled colic horses but decreased over time. In the colic horses, dialysate glycerol concentrations varied considerably whereas in the healthy horses, dialysate glycerol was elevated during anaesthesia but decreased after standing. In both groups, lactate concentration was higher in dialysate than in plasma. The correspondence between dialysate and plasma concentrations of glucose, urea and glycerol varied.

CONCLUSION

Microdialysis proved to be suitable in the clinical setting for monitoring of the metabolic events during anaesthesia and recovery. It was possible with this technique to show greater muscle metabolic alterations in the colic horses compared to the healthy horses in response to regaining the standing position.

Use of rapid sampling microdialysis for intraoperative monitoring of bowel ischemia

PURPOSE

Intestinal ischemia is a major cause of anastomotic leak and death and remains a clinical challenge as the physician relies on several nonspecific signs, biologic markers, and radiologic studies to make the diagnosis. This study used rapid sampling online microdialysis to evaluate the biochemical changes occurring in a segment of human bowel during and after resection, and assessed for the feasibility and reproducibility of this technique in monitoring intestinal ischemia.

METHODS

A custom made, rapid sampling online microdialysis analyzer was used to monitor the changes in the bowel wall of specimens being resected intraoperatively. Two patients were recruited for the pilot study to optimize the analyzer and seven patients undergoing colonic resections were recruited for the data collection and analysis.

RESULTS

The concentration of glucose in the extracellular bowel wall fluid decreased transiently after division of individual feeding arteries followed by a rebound increase in the concentration back to baseline concentrations. After completion of resection, glucose concentrations continued to decrease while lactate concentrations increased constantly.

CONCLUSION

Rapid sampling microdialysis was feasible in the clinical environment. These results suggest that tissue responds to ischemic insult by mobilizing glucose stores which later decrease again, whereas lactate concentrations constantly increased.

The effects of vasopressors on perfusion of gastric graft after esophagectomy. An experimental study

AIMS

To evaluate the impact of the perioperative administration of norepinephrine on the perfusion of the esophageal graft.

METHODS

This is an experimental study. Six swine underwent transhiatal esophagectomy; the stomach was used to replace the resected esophagus. We provoked hemorrhagic shock to the animals and then we administered noradrenaline to restore the blood pressure. We monitored the graft perfusion perioperatively using the technique of microdialysis.

RESULTS

In all animals, the graft experienced severe hypoperfusion after the administration of noradrenaline that was statistically significant.

CONCLUSIONS

Our data support the hypothesis that norepinephrine should be used with extreme caution in the perioperative setting after esophagectomy. Further studies, however, will be required to evaluate the clinical significance of this finding.

Anastomotic leakage, the search for a reliable biomarker. A review of the literature

BACKGROUND

Colorectal anastomotic leakage (AL) is a severe complication leading to severe infection, sepsis and sometimes death. At present the diagnosis is made clinically, usually at 6-8 days after surgery. An objective biomarker reflecting the intra-abdominal milieu surrounding the anastomosis would be a useful additional diagnostic tool to make the diagnosis of AL before its clinical presentation. This review aims to assess the current status of the search for such a biomarker in peritoneal fluid.

METHOD

A literature search was carried out, using MEDLINE, PubMed and the Cochrane library, for all publications concerning human peritoneal fluid in relation to postoperative complications in general, and, more specific, anastomotic leakage after colorectal surgery.

RESULTS

Analysis of several immune parameters, tissue repair parameters, parameters for ischaemia and microbiological composition of peritoneal fluid show that these can be determined reliably in the fluid, albeit with a large variance. Furthermore the data show that changes in concentration of these parameters precede AL and other postoperative complications by several days.

CONCLUSION

The results of the review demonstrate that it is possible to distinguish between patients with and without AL by measuring biomarkers in fluid from the peritoneal drain. Prospective studies with larger numbers of patients should, however, be performed and additional biomarkers should be studied to explore the full diagnostic potential of this approach.

Is early detection of anastomotic leakage possible by intraperitoneal microdialysis and intraperitoneal cytokines after anterior resection of the rectum for cancer?

PURPOSE

This prospective study assessed methods of detecting intraperitoneal ischemia and inflammatory response in patients with and without postoperative complications after anterior resection of the rectum.

METHODS

In 23 patients operated on with anterior resection of the rectum for rectal carcinoma, intraperitoneal lactate, pyruvate, and glucose levels were monitored postoperatively for six days by using microdialysis with catheters applied in two locations: intraperitoneally near the anastomosis, and in the central abdominal cavity. A reference catheter was placed subcutaneously in the pectoral region. Cytokines, interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-alpha, were measured in intraperitoneal fluid by means of a pelvic drain for two postoperative days.

RESULTS

The intraperitoneal lactate/pyruvate ratio near the anastomosis was higher on postoperative Day 5 (P = 0.029) and Day 6 (P = 0.009) in patients with clinical anastomotic leakage (n = 7) compared with patients without leakage (n = 16). The intraperitoneal levels of IL-6 (P = 0.002; P = 0.012, respectively) and IL-10 (P = 0.002; P = 0.041, respectively) were higher on postoperative Days 1 and 2 in the leakage group, and TNF-alpha was higher in the leakage group on Day 1 (P = 0.011). In-hospital clinical anastomotic leakage was diagnosed on median Day 6, and leakage after hospital discharge on median Day 20.

CONCLUSIONS

The intraperitoneal lactate/pyruvate ratio and cytokines, IL-6, IL-10, and TNF-alpha, were increased in patients who developed symptomatic anastomotic leakage before clinical symptoms were evident.

Rectal lactate levels in endoluminal microdialysate during routine coronary surgery

The aim of this prospective study was to determine the feasibility of intestinal endoluminal microdialysis as a new method for clinical monitoring of the adequacy of splanchnic perfusion in the large bowel. A microdialysis catheter for continuous lactate, glycerol, glucose and pyruvate measurements attached to a tonometric catheter was placed into the lumen of the recto-sigmoid junction prior to surgery in 13 patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB). Lactate was also measured in blood and muscle. CPB was associated with a 10-fold increase in luminal lactate from 0.16 (0.01) to 1.67 (0.38) mmol x l(-1) (p < 0.001). Muscular lactate increased from baseline levels 1.20 (0.21) to 1.77 (0.36) mmol x l(-1) during CPB (p = 0.01), but the muscular lactate-pyruvate ratio remained unchanged. Arterial lactate increased only slightly from 0.9 (0.05) to 1.1 (0.06) mmol x l(-1) (p = 0.027) during CPB. Increased lactate concentrations in the large bowel during CPB are suggestive of local lactate production consistent with impaired oxygen delivery. Intestinal endoluminal microdialysis is a potential clinically applicable method for monitoring intestinal metabolism. Combined with tonometry, microdialysis provides the opportunity to monitor both circulation and metabolism in the rectal mucosa.

Prediction of postoperative complications after urgent laparotomy by intraperitoneal microdialysis: A pilot study

OBJECTIVE

The aim of the present study was to investigate the role of intraperitoneal microdialysis (IPM) techniques in monitoring the evolution of postoperative critically ill patients requiring urgent laparotomy.

SUMMARY BACKGROUND DATA

Postoperative intraabdominal sepsis is associated with an important degree of morbidity and mortality in acutely ill patients. Early diagnosis is critical to improve outcomes.

METHODS

: The study included 25 consecutive patients admitted to the intensive care unit (ICU) after urgent laparotomy. Measurements of microdialysate fluid were performed through a microdialysis catheter, positioned intraperitoneally, during the first 5 postoperative days and lactate/pyruvate (L/P) ratios calculated. Patients were followed until hospital discharge.

RESULTS

Ten patients had a complicated postoperative course, including 4 deaths (3 refractory shock, 1 mesenteric ischemia), 3 reinterventions (1 necrotic collection, 1 mesenteric ischemia, 1 biliary leak), 2 secondary peritonitis, and 1 intraabdominal collection. The IPM L/P ratio in these patients was already significantly higher during the first 24 postoperative hours compared with patients who had no complications (35 +/- 21 vs. 18 +/- 6, P < 0.01). An IPM L/P ratio above 22 on postoperative day 1 had a sensitivity of 0.64 and a specificity of 0.79 for complications. There were no significant differences between the two groups in pH, lactate, white blood cell count, or subcutaneous L/P ratio. No complication was associated with the technique.

CONCLUSIONS

IPM is safe and reliable and provides valuable information after urgent laparotomy. Persistently high L/P values should raise the possibility of serious postoperative complications.

Membrane microdialysis: Evaluation of a new method to assess splanchnic tissue metabolism

OBJECTIVE

Measuring peritoneal lactate concentrations could be useful for detecting splanchnic hypoperfusion. The aims of this study were to evaluate the properties of a new membrane-based microdialyzer in vitro and to assess the ability of the dialyzer to detect a clinically relevant decrease in splanchnic blood flow in vivo.

DESIGN

A membrane-based microdialyzer was first validated in vitro. The same device was tested afterward in a randomized, controlled animal experiment.

SETTING

University experimental research laboratory.

SUBJECTS

Twenty-four Landrace pigs of both genders.

INTERVENTIONS

In vitro: Membrane microdialyzers were kept in warmed sodium lactate baths with lactate concentrations between 2 and 8 mmol/L for 10-120 mins, and microdialysis lactate concentrations were measured repeatedly (210 measurements). In vivo: An extracorporeal shunt with blood reservoir and roller pump was inserted between the proximal and distal abdominal aorta, and a microdialyzer was inserted intraperitoneally. In 12 animals, total splanchnic blood flow (measured by transit time ultrasound) was reduced by a median 43% (range, 13% to 72%) by activating the shunt; 12 animals served as controls.

MEASUREMENTS AND MAIN RESULTS

In vitro: The fractional lactate recovery was 0.59 (0.32-0.83) after 60 mins and 0.82 (0.71-0.87) after 90 mins, with no further increase thereafter. At 60 and 90 mins, the fractional recovery was independent of the lactate concentration. In vivo: Abdominal blood flow reduction resulted in an increase in peritoneal microdialysis lactate concentration from 1.7 (0.3-3.8) mmol/L to 2.8 (1.3-6.2) mmol/L (p = .006). At the same time, mesenteric venous-arterial lactate gradient increased from 0.1 (-0.2-0.8) mmol/L to 0.3 (-0.3 -1.8) mmol/L (p = .032), and mesenteric venous-arterial Pco2 gradients increased from 12 (8-19) torr to 21 (11-54) torr (p = .005).

CONCLUSIONS

Peritoneal membrane microdialysis provides a method for the assessment of splanchnic ischemia, with potential for clinical application.