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

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.

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.

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.

Results of postoperative microdialysis intraperitoneal and at the anastomosis in patients developing anastomotic leakage after rectal cancer surgery

Introduction: Anastomotic leakage postoperatively in patients operated with rectum resection and primary anastomosis is a common and feared complication. We have studied seven patients with an anastomotic leakage after surgery and compared them with 13 patients without complications.Methods: Metabolic measurements with microdialysis were done during the first seven postoperative days, with measurements of glucose, pyruvate, lactate and glycerol. The lactate/pyruvate ratio was calculated. Measurements were performed subcutaneously, intraperitoneally and at the anastomosis. The inflammatory cytokines, IL 6 and IL 10, were measured intravenously and intraperitoneally 48 hours postoperatively.Results: Intravenous and intraperitoneal IL 6 were higher in the leakage group. Around the small intestine (intraperitoneally), we found that patients developing anastomotic leakage had higher lactate and lactate/pyruvate ratio immediately after surgery. They also showed lower glycerol levels. At the anastomosis, we found higher lactate and lactate/pyruvate ratio in anastomotic leak patients after the fourth postoperative day.Conclusions: The results indicate that a possible mechanism behind an anastomotic leakage is an impaired circulation and thus insufficient saturation to the small intestine peroperatively. This develops into an inflammation both intraperitoneally and intravenously, which, if not reversed, spread within the gastrointestinal tract .The colorectal anastomosis is the most vulnerable part of the gastrointestinal tract postoperatively and hypoxia and inflammation may occur there, and an anastomosis leakage will be the consequence.

Perioperative intraperitoneal metabolic markers in patients undergoing cardiac surgery with cardiopulmonary bypass: an exploratory pilot study

Background:

Cardiopulmonary bypass and postoperative cardiac dysfunction cause splanchnic hypoperfusion resulting in intra-abdominal anaerobic metabolism and risk for gastrointestinal complications. The intra-abdominal metabolism can be monitored by intraperitoneal measurement of relevant metabolites using microdialysis. The aim of this study was to investigate the intraperitoneal metabolism using microdialysis during and after cardiopulmonary bypass at 34°C.

Methods:

In six patients undergoing elective coronary artery bypass grafting or aortic valve replacement under cardiopulmonary bypass, microdialysis was used to measure intraperitoneal and subcutaneous glucose, lactate, pyruvate, glycerol and glutamate concentrations, intraoperatively and up to 36 hours postoperatively. Arterial and central venous blood gases were analysed as were haemodynamics and the development of complications.

Results:

All patients had an ordinary perioperative course and did not develop gastrointestinal complications. The arterial, intraperitoneal and subcutaneous lactate concentrations changed during the perioperative course with differences between compartments. The highest median (interquartile range) concentration was recorded in the intraperitoneal compartment at 1 hour after the end of cardiopulmonary bypass (2.1 (1.9–2.5) mM compared to 1.3 (1.2–1.7) mM and 1.5 (1.0–2.2) mM in the arterial and subcutaneous compartments, respectively). In parallel with the peak increase in lactate concentration, the intraperitoneal lactate/pyruvate ratio was elevated to 33.4 (12.9–54.1).

Conclusion:

In cardiac surgery, intraperitoneal microdialysis detected changes in the abdominal metabolic state, which were more pronounced than could be shown by arterial blood gas analysis. Despite an uneventful perioperative course, patients undergoing low-risk surgery under cardiopulmonary bypass might be subjected to a limited and subclinical intra-abdominal anaerobic state.

Metabolic Response to Claudication in Peripheral Arterial Disease: A Microdialysis Pilot Study

OBJECTIVES

This is a pilot study, and the objective of the study was to investigate the possible uses of microdialysis in the calf muscle to assess the metabolic response to intermittent claudication (IC) and in addition evaluate the simultaneous systemic inflammatory reaction.

METHODS

Dialysate and venous blood sampling was performed before, during and after walking on a treadmill to maximal tolerable claudication (controls 10 min) using 1 microdialysis catheter inserted in the gastrocnemius muscle, 1 subcutaneously in the pectoral region (as a reference), and a peripheral venous catheter.

RESULTS

A total of 9 participants were recruited, 6 patients with IC and 3 healthy control subjects. At baseline, patients with IC and control subjects did not differ in metabolic findings (glucose, lactate, pyruvate, and glycerol) in the gastrocnemius muscle. Subcutaneous glucose concentration was higher in control subjects. After physical exertion, gastrocnemius and subcutaneous glycerol, lactate, and pyruvate concentrations increased in patients with IC. Plasma concentrations of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), interleukin-1ß (IL-1ß), hepatocyte growth factor, and vascular endothelial growth factor were higher in IC subjects at baseline, and TNF-α, IL-6, and IL-18 increased after walking as did IL-6 and IL-1ß in control subjects. The muscle catheters did not show any signs of harm.

CONCLUSIONS

Microdialysis can be used to study the ongoing metabolic response during walking and claudication. Our results suggest both an acute local and a systemic inflammatory reaction during development of claudication.

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.

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.

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.

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.

Microdialysis: characterisation of haematomas in myocutaneous flaps by use of biochemical agents

Metabolic markers are measured by microdialysis to detect postoperative ischaemia after reconstructive surgery with myocutaneous flaps. If a haematoma develops around the microdialysis catheter, it can result in misinterpretation of the measurements. The aim of the present study was to investigate whether a haematoma in a flap can be identified and dissociated from ischaemia, or a well-perfused flap, by a characteristic chemical profile. In 7 pigs, the pedicled rectus abdominal muscle flap was mobilised on both sides. A haematoma was made in each flap and two microdialysis catheters were placed, one in the haematoma, and the other in normal tissue. One flap was made ischaemic by ligation of the pedicle. For 6 hours, the metabolism was monitored by measurement every half-an-hour of the concentrations of glucose, lactate, pyruvate, and glycerol from all 4 catheters. After 3 hours of monitoring, intravenous glucose was given as a challenge test to identify ischaemia. The non-ischaemic flap could be differentiated from the ischaemic flap by low glucose, and high lactate, concentrations. It was possible to identify a catheter surrounded by a haematoma in ischaemic as well as non-ischaemic muscle from a low or decreasing concentration of glucose together with a low concentration of lactate. All four sites could be completely dissociated when the concentrations of glucose and lactate were evaluated and combined with the lactate:glucose ratio and a flow chart. The challenge test was useful for differentiating between haematomas in ischaemic and non-ischaemic tissue.

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.

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.

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.

Peritoneal microdialysis. Early diagnosis of anastomotic leakage after low anterior resection for rectosigmoid cancer

BACKGROUND

The aim of the present study was to evaluate the efficacy and safety of intraperitoneal microdialysis in early detection of anastomotic leakage after low anterior resection for rectosigmoid cancer.

METHODS

In a series of 116 consecutive patients scheduled for low anterior resection for rectosigmoid cancer, a total of 50 patients consented to participate. Peritoneal microdialysis was performed by a 1 mm thin catheter anchored in close proximity to the anastomosis. Five patients were excluded due to catheter malfunction. Average microdialysis time in the remaining 45 patients was 177.6 (80-252) hours. Samples were collected every 4-hours, and the concentration of glucose, lactate, pyruvate and glycerol was measured.

RESULTS

Four patients developed symptomatic anastomotic leakage. Two patients developed non-abdominal sepsis. In 38 patients the postoperative course was uncomplicated, considering major complications, and they served as controls. In three patients with late (>or=10 days) anastomotic leakage a significant increase in concentration of lactate and lactate/pyruvate ratio (L/P-ratio) was seen several days prior to development of clinical symptoms. In one patient with early anastomotic leakage it coincided with the development of clinical symptoms. In the two patients with non-abdominal sepsis the values were within normal range.

CONCLUSION

Peritoneal microdialysis is a safe and promising tool in early diagnosis of anastomotic leakage after low anterior resection for rectosigmoid cancer.

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.

Microdialysis versus other techniques for the clinical assessment of in vivo tissue drug distribution

Quantification of target site pharmacokinetics (PK) is crucial for drug discovery and development. Clinical microdialysis (MD) has increasingly been employed for the description of drug distribution and receptor phase PK of the unbound fraction of various analytes. Costs for MD experiments are comparably low and given suitable analytics, target tissue PK of virtually any drug molecule can be quantified. The major limitation of MD stems from the fact that organs such as brain, lung or liver are not readily accessible without surgery. Recently, non-invasive imaging techniques, i.e. positron emission tomography (PET) or magnetic resonance spectroscopy (MRS), have become available for in vivo drug distribution assessment and allow for drug concentration measurements in practically every human organ. Spatial resolution of MRS imaging, however, is low and although PET enables monitoring of regional drug concentration differences with a spatial resolution of a few millimetres, discrimination between bound and unbound drug or parent compound and metabolite is difficult. Radiotracer development is furthermore time and labour intensive and requires special expertise and radiation exposure and costs originating from running a PET facility cannot be neglected. The recent complementary use of MD and imaging has permitted to exploit individual strengths of these diverse techniques. In conclusion, MD and imaging techniques have provided drug distribution data that have so far not been available. Used alone or in combination, these methods may potentially play an important role in future drug research and development with the potential to serve as translational tools for clinical decision making.