Surface microdialysis measures local tissue metabolism after Ivor Lewis esophagectomy; an attempt to predict anastomotic defect.

Anastomotic defect (AD) after esophagectomy can lead to severe complications with need for surgical or endoscopic intervention. Early detection enables early treatment and can limit the consequences of the AD. As of today, there are limited methods to predict AD. In this study, we have used microdialysis (MD) to measure local metabolism at the intrathoracic anastomosis. Feasibility and possible diagnostic use were investigated. Sixty patients planned for Ivor Lewis esophagectomy were enrolled. After construction of the anastomosis, surface MD (S-MD) probes were attached to the outer surface of the esophageal remnant and the gastric conduit in close vicinity of the anastomosis and left in place for 7 postoperative days (PODs). Continuous sampling of local tissue concentrations of metabolic substances (glucose, lactate, and pyruvate) was performed postoperatively. Outcome, defined as AD or not according to Esophagectomy Complications Consensus Group definitions, was recorded at discharge or at first postoperative follow up. Difference in concentrations of metabolic substances was analyzed retrospectively between the two groups by means of artificial neural network technique. S-MD probes can be attached and removed from the gastric tube reconstruction without any adverse events. Deviating metabolite concentrations on POD 1 were associated with later development of AD. In subjects who developed AD, no difference in metabolic concentrations between the esophageal and the gastric probe was recorded. The technical failure rate of the MD probes/procedure was high. S-MD can be used in a clinical setting after Ivor Lewis esophagectomy. Deviation in local tissue metabolism on POD 1 seems to be associated with development of AD. Further development of MD probes and procedure is required to reduce technical failure.

Peri-anastomotic microdialysis lactate assessment after esophagectomy.

BACKGROUND: Esophagectomy is the cornerstone in curative treatment for esophageal and gastroesophageal junctional cancer. Esophageal resection is an advanced procedure with many complications, whereof anastomotic leak is the most dreaded. This study aimed to monitor the microcirculation with microdialysis analysis of local lactate levels in real-time on both sides of the esophagogastric anastomosis in totally minimally invasive Ivor-Lewis esophagectomy. MATERIALS AND METHODS: Twenty-five patients planned for esophageal resection with gastric conduit reconstruction and intrathoracic anastomosis were recruited. A sampling device, the OnZurf® Probe, along with the CliniSenz® Analyser (Senzime AB, Uppsala Sweden) was utilized for measurements. Lactate levels from both sides of the anastomosis were analysed in real time, on site, by a transportable analyser device. Measurements were made every 30 min during the first 24 h, and thereafter every 2 hours for up to 4 days. RESULTS: All probes could be positioned as planned and on the third postoperative day 19/25 and 15/25 of the esophageal and gastric probes, respectively, continued to deliver measurements. In total, 89.6% (1539/1718) and 72.4% (1098/1516) of the measurements were deemed successful. The average lactate level on the esophageal side of the anastomosis and the gastric conduit ranged between 1.1-11.5 and 0.8-7.0 mM, respectively. Two anastomotic leaks occurred, one of which had persisting high lactate levels on the gastric side of the anastomosis. CONCLUSION: Application and use of the novel CliniSenz® analyser system, in combination with the OnZurf® Probe was feasible and safe. Continuous monitoring of analytes from the perianastomotic area has the potential to improve care after esophageal resection.

Proteomic analysis and ATP assay reveal a positive effect of artificial cerebral spinal fluid perfusion following microdialysis sampling on repair of probe-induced brain damage.

BACKGROUND: Microdialysis (MD) is conventionally used to measure the in vivo levels of various substances and metabolites in extracellular and cerebrospinal fluid of brain. However, insertion of the MD probe and subsequent perfusion to obtain samples cause damage in the vicinity of the insertion site, raising questions regarding the validity of the measurements. NEW METHOD: We used fluorogenic derivatization liquid chromatography-tandem mass spectrometry, that quantifies both high and low abundance proteins, to differentiate the effects of perfusion from the effects of probe insertion on the proteomic profiles of expressed proteins in rat brain. RESULTS: We found that the expression levels of five proteins were significantly lower in the perfusion group than in the non-perfusion group. Three of these proteins are directly involved in ATP synthesis. In contrast to decreased levels of the three proteins involved in ATP synthesis, ATP assays show that perfusion, following probe insertion, even for a short time (3 h) increased ATP level up to 148% that prior to perfusion, and returned it to normal state (before probe insertion). COMPARISON WITH EXISTING METHOD: There is essentially no information regarding which observed changes are due to probe insertion and which to perfusion. CONCLUSIONS: Our findings partially demonstrate that the influence of whole MD sampling process may not significantly compromise brain function and subsequent analytical results may have physiological equivalence to normal, although energy production is transiently damaged by probe insertion.

Intrabronchial Microdialysis: Effects of Probe Localization on Tissue Trauma and Drug Penetration into the Pulmonary Epithelial Lining Fluid.

Recent intrabronchial microdialysis data indicate that the respiratory epithelium is highly permeable to drugs. Of concern is whether intrabronchial microdialysis disrupts the integrity of the respiratory epithelium and thereby alters drug penetration into the pulmonary epithelial lining fluid (PELF). The objective of this study was to investigate the effect of intrabronchial microdialysis on the integrity of the bronchial epithelium. Microdialysis sampling in PELF in proximal (n = 4) and distal bronchi (n = 4) was performed after intravenous inulin and florfenicol administration in anaesthetized pigs. Inulin was used as a marker molecule of permeability of the epithelium, and florfenicol was used as test drug. Bronchial tissue was examined by histopathology (distal and proximal bronchi) and gene expression analysis (RT-qPCR, proximal bronchi) at the termination of the experiment (6.5 hr). The microdialysis probe caused overt tissue trauma in distal bronchi, whereas no histopathological lesions were observed in proximal bronchi. A moderate up-regulation of the pro-inflammatory cytokines IL1B, IL6 and acute-phase reactant serum amyloid A was seen in proximal bronchi surrounding the microdialysis probes suggesting initiation of an inflammatory response. The observed up-regulation is considered to have limited impact on drug penetration during short-term studies. Inulin penetrated the respiratory epithelium in both proximal and distal bronchi without any correlation to histopathological lesions. Likewise, florfenicol penetration into PELF was unaffected by bronchial histopathology. However, this independency of pathology on drug penetration may not be valid for other antibiotics. We conclude that short-term microdialysis drug quantification can be performed in proximal bronchi without disruption of tissue integrity.

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.

Sterile trauma to normal human dermis invariably induces IL1beta, IL6 and IL8 in an innate response to "danger".

Microdialysis allows the study of the local production and temporal resolution of cytokines in living skin. Samples were taken from the normal skin of 10 healthy subjects for 24-28 h after insertion of a concentric microdialysis catheter, and analysed with a Luminex bead-based assay. Interleukin-1 beta (IL1b), IL6 and IL8 were seen in all subjects at all time-points after the first hour. Levels peaked at 5-8 h, equilibrating to lower levels at 24 h. Immunohistological double staining for human leukocyte antigen (HLA)-DR and intracellular cytokines on biopsies taken after catheter removal showed many stained cells in the dermis, in contrast to the few cells stained in the epidermis. This study demonstrates the reactive capability of the dermis when provoked separately from the epidermis. The production of IL1b, IL6 and IL8 occurs invariably in what can be termed an innate, dermal response to "danger"; in this case in the form of sterile needle trauma.

Proinflammatory tissue response and recovery of adipokines during 4 days of subcutaneous large-pore microdialysis.

INTRODUCTION: Subcutaneous adipose tissue (SAT) is increasingly being recognized as a highly active tissue secreting adipokines involved in many physiological and pathophysiological processes. Microdialysis is a technique used for in vivo sampling of interstitial fluid from e.g. SAT. The technique was originally designed for sampling of small molecules but recently the availability of catheters with large-pore membranes has made it possible to recover larger molecules such as adipokines. The present study investigated tissue response towards large-pore microdialysis catheters inserted into human SAT for 4 days. METHODS: Large-pore microdialysis catheters were inserted into the abdominal SAT of ten healthy males (age 23.0+/-1.1 years, BMI 22.1+/-0.7 kg/m(2), mean+/-SEM) and dialysates were collected immediately after insertion (day 0) and on days 1, 2 and 4. Dialysates were analyzed for IL-1beta, IL-6, IL-8, MCP-1, TNF-alpha and adiponectin using Luminex Multiplex technology. RESULTS: Interstitial IL-1beta increased from a sub-detectable level to 69+/-22 pg/ml on day 1 (p<0.001). IL-6 increased 23-fold on day 0 (p<0.001) towards a plateau of app. 5000 pg/ml on days 1 and 2. IL-8 increased 54-fold on day 0 (p<0.001) with further increase on day 1 (4259+/-777 pg/ml, p<0.001). MCP-1 increased 13-fold to an apparent plateau on day 0 (p<0.001) with further increase on day 1 (7256+/-1953 pg/ml, p=0.002). TNF-alpha increased 7-fold to an apparent plateau on day 0 (p<0.001) with further increase on day 1 (121+/-28 pg/ml, p=<0.001). By day 4, IL-1beta, IL-6, IL-8, MCP-1 and TNF-alpha were all returning towards baseline level. Adiponectin was unchanged on day 0 (1,040,422+/-295,510 pg/ml, p=0.36), decreased to 346,300+/-48,002 pg/ml on day 1 (p=0.002) and remained unchanged hereafter. DISCUSSION: Insertion of a large-pore microdialysis catheter into human SAT results in tissue trauma leading to changes in the interstitial concentrations of IL-1beta, IL-6, IL-8, MCP-1, TNF-alpha and adiponectin.

Microdialysis of cytokines: methodological considerations, scanning electron microscopy, and determination of relative recovery.

Cerebral microdialysis is a monitoring technique with expanding clinical and research utility following traumatic brain injury. This study's aim was to determine the relative recovery for 12 cytokines using both crystalloid (CNS perfusion fluid) and colloid (CNS perfusion fluid supplemented with 3.5% human serum albumin) perfusate. Six CMA71 microdialysis catheters (nominal molecular weight cut-off 100 kDa) were perfused in vitro with either crystalloid or colloid and the relative recovery (%) determined for the cytokines as follows (crystalloid/colloid perfusate): IL-1alpha (50.6/48), IL-1beta (34.6/38.4), IL-1ra (21.9/38.4), IL-2 (17.1/52.8), IL-4 (26/56.7), IL-6 (9.8/25.5), IL-8 (47.7/73.4), IL-10 (2.9/8.7), IL-17 (14.4/43.7), TNF-alpha (4.4/31.2), MIP-1alpha (31.8/55.6), and MIP-1beta (31.9/50.1). The colloid perfusate significantly improved relative recovery for nine of these cytokines ( p < 0.05), but not for IL-1alpha, IL-1beta, and IL-8. Relative recovery was related to apparent molecular weight of cytokine and to isoelectric point (pI), a surrogate marker of hydrophilicity. The mean fluid recovery for crystalloid and colloid perfusate was 92% and 145%, respectively. Scanning electron microscopy was utilized to investigate the ultrastructure of microdialysis membranes: (1) 20-kDa membrane, (2) 100-kDa membrane, and (3) ex vivo 100-kDa membrane. The 100-kDa membranes possessed multiple large cavities and the catheter examined after use in human brain clearly demonstrated cellular debris within the pores of the membrane. While colloid perfusate improves relative recovery, it causes a net influx of fluid into the microdialysis catheter, potentially dehydrating the extracellular space. This study is the first to systematically determine relative recovery in vitro for a wide range of cytokines. The two forms of perfusion fluid require direct comparison in vivo.

Determination of markers for collagen type I turnover in peritendinous human tissue by microdialysis: effect of catheter types and insertion trauma.

OBJECTIVES: Previous results from our group have shown that loading of human tendon elevates tendinous type I collagen production measured by microdialysis. However, exclusion of the observed elevation as a response to trauma from inserting the microdialysis catheters or a possible influence from the collagen production in skin was not determined. METHODS: Using the microdialysis method we measured the tissue levels of type I collagen metabolism markers [procollagen I COOH-terminal propeptide (PICP) and COOH-terminal telopeptide of type I collagen (ICTP)] in peritendinous tissue of the Achilles tendon in volunteers at two time points, 0 and 72 h. Using two different catheter types, an investigation of the contribution from the skin in the collagen results obtained was also examined. RESULTS: The data showed no significant changes in the dialysate levels for PICP or ICTP (p>0.05) in either of the catheters. CONCLUSION: Inserting microdialysis fibres around the Achilles tendon twice does not increase the collagen type I metabolism determined 3 days after the initial trauma, and when using microdialysis for measuring peritendinous collagen turnover the skin contribution can be regarded as negligible. These findings support microdialysis as a valid method for the determination of collagen metabolism in peritendinous tissue.

Cerebral oxygen and microdialysis monitoring during aneurysm surgery: effects of blood pressure, cerebrospinal fluid drainage, and temporary clipping on infarction.

OBJECT: The aim of this study was to investigate potential episodes of cerebral ischemia during surgery for large and complicated aneurysms, by examining the effects of arterial temporary clipping and the impact of confounding variables such as blood pressure and cerebrospinal fluid (CSF) drainage. METHODS: Brain tissue PO2, PCO2, and pH, as well as temperature and extracellular glucose, lactate, pyruvate, and glutamate were monitored in 46 patients by using multiparameter sensors and microdialysis. Baseline data showed that brain tissue PO2 decreased significantly, below a mean arterial pressure (MAP) threshold of 70 mm Hg. Further evidence of its relationship with cerebral perfusion pressure was shown by an increase in mean brain tissue PO2 after drainage of CSF from the basal cisterns (Wilcoxon test, p < 0.01). Temporary clipping was required in 31 patients, with a mean total duration of 14 minutes (range 3-52 minutes), causing brain tissue PO2 to decrease and brain tissue PCO2 to increase (Wilcoxon test, p < 0.01). In patients in whom no subsequent infarction developed in the monitored region, brain tissue PO2 fell to 11 mm Hg (95% confidence interval 8-14 mm Hg). A brain tissue PO2 level below 8 mm Hg for 30 minutes was associated with infarction in any region (p < 0.05 according to the Fisher exact test); other parameters were not predictive of infarction. Intermittent occlusions of less than 30 minutes in total had little effect on extracellular chemistry. Large glutamate increases were only seen in two patients, in both of whom brain tissue PO2 during occlusion was continuously lower than 8 mm Hg for longer than 38 minutes. CONCLUSIONS: The brain tissue PO2 decreases with hypotension, and, when it is below 8 mm Hg for longer than 30 minutes during temporary clipping, it is associated with increasing extracellular glutamate levels and cerebral infarction.

Adverse cerebral events detected after subarachnoid hemorrhage using brain oxygen and microdialysis probes.

OBJECTIVE: A prospective observational study was conducted to investigate whether episodes of ischemia are detected by continuous cerebral monitoring and whether such episodes are related to clinical outcome. METHODS: Forty patients (35 after subarachnoid hemorrhage and 5 after complex aneurysm surgery) were monitored for a total of 174 days (mean, 4 d; range, 1-12 d). Brain tissue partial pressures of oxygen and carbon dioxide, pH, and temperature were measured continuously using Neurotrend sensors (Codman, Bracknell, England). Bedside analysis of extracellular chemistry was performed hourly using microdialysis. Glasgow Outcome Scale score was assessed at 3 to 6 months. RESULTS: Patients with poor World Federation of Neurosurgical Societies grades (4 and 5) or an unfavorable outcome (severe disability or death) had, on average, higher lactate and lactate/pyruvate ratio but lower glucose/lactate ratio (P < or = 0.05). Brain tissue partial pressure of oxygen decreased to below 1.1 kPa in 78% of the patients for 18% (95% confidence interval, 12-24%) of time monitored. There were 197 episodes in which brain tissue partial pressures of oxygen decreased to below 1.1 kPa for at least 30 minutes. Unfavorable outcome was associated with more of these episodes (8.8 episodes; 95% confidence interval, 4.4-13.2 episodes) than favorable outcome (2.2 episodes; 95% confidence interval, 1.1-3.3 episodes), as well as an episode of glutamate levels of more than 10 micromol/L or lactate/pyruvate ratio more than 40 (P < 0.05, chi(2) test). CONCLUSION: Intraparenchymal oximetry and microdialysis can detect but fail to predict the development of delayed cerebral ischemia. There were associations between episodes of low brain oxygen, abnormal microdialysis, and unfavorable outcome, but these associations were weak.

Disappearance of central pain following iatrogenic stroke.

An exceptional case of long-standing central pain temporarily relieved by a focal stroke in the primary somatosensory area is reported. This case highlights the focal nature of central pain mechanisms and the possible value of selective subparietal leukotomies in the management of central pain.

Sampling extracellular aspartate, glutamate and gamma-aminobutyric acid in striate cortex of awake cat by in vivo microdialysis: surgical and methodological aspects.

A method which permits repeated microdialysis in the cortical layers of area 17 of the awake cat is described. Under visual control through a surgical microscope and using a stereotactic instrument, four probe guides are permanently implanted in area 17 of one hemisphere of the anesthetized animal and two fixation bars are mounted on the skull to allow fixation of the cat in a stereotactic frame. The implantation of four probe guides in the same hemisphere allows simultaneous sampling from different cortical regions serving different parts of the visual field. A removable transparent cover protects the probe guides. After recovery from surgery the awake cats are trained to adapt to a fixation of 5 h in a stereotaxic apparatus. Once adapted to that situation, the cats are ready for microdialysis experiments without anesthesia. The day of the experiment, the awake animal was fixed in the stereotactic frame and the probes inserted into the guides. To test the validity of the method, the basal efflux and the depolarization efflux, triggered by the addition of 65 mM K(+) to the artificial cerebrospinal fluid, of the amino acids aspartate, glutamate and gamma-aminobutyric acid are measured by two HPLC-electrochemical detection methods. The exact localization of the probes and the reaction of the surrounding tissue is studied using immunocytochemistry for glutamate and glial fibrilary acidic protein. Our neurochemical and morphological results suggest the feasibility of multiple and repeated probe insertions for microdialysis experiments in the cerebral cortex of awake and behaving cat. This method provides a new tool to investigate the cortical plasticity.

A new method of in-vivo microdialysis of the human brain.

In-vivo microdialysis has been used extensively to study the neurochemical mechanisms of ischemia, epilepsy and hypoglycemia. It is also being increasingly used to document the response of neurons to various medications. Most of the work to date has been done in small animals. In the last 2 years, the technique has been adapted for use in patients with subarachnoid hemorrhage, head trauma, Parkinson's disease, brain tumors and epilepsy. Two of the major limiting factors are the invasiveness of the technique and the resultant potential for CNS infection. We describe a simple, safe and reliable method to measure neurochemical changes in the human brain with in-vivo microdialysis. We were able to easily monitor for 4-6 h daily for up to 4 days in awake or comatose patients with subarachnoid hemorrhage or head trauma. Cerebral concentrations of glutamate, GABA, other amino acids and catecholamines were measured. This technique thus has a potential for on-line measurements of neurotoxins in patients with unstable neurological conditions.