Intracerebral microdialysis in neurosurgical intensive care patients utilising catheters with different molecular cut-off (20 and 100 kD)

Summary Objective. To compare the properties of a new intracerebral micro-dialysis catheter with a high cut-off membrane (molecular cut-off 100 kDalton) with a standard catheter (CMA70, molecular cut-off 20 kDalton). Methods. Paired intracerebral microdialysis catheters were inserted in fifteen comatose patients treated in a neurosurgical intensive care unit following subarachnoid haemorrhage or traumatic brain injury. The high-cut-off catheter (D₁₀₀) differed from the CMA 70 catheter by the length (20 mm) and cut-off properties of the catheter membranes (100 kDalton) and the perfusion fluids used (Ringer-Dextran 60). Samples were collected every 4–6 hours, analyzed bedside (for glucose, glutamate, glycerol, lactate, pyruvate and urea) and later in the laboratory (for total protein). Results. Fluid recovery was similar for the two types of catheters, but significantly more protein was recovered by the D₁₀₀ catheter. The recovery of glycerol and pyruvate did not differ, while minor differences in recovery of glutamate and glucose were observed. The recovery of lactate was considerably lower in the D₁₀₀ catheter (p < 0.01), influencing the lactate/pyruvate-ratio. The patterns of concentration changes over time were consistent for all metabolites, and independent of type of catheter. Conclusion. Microdialysis catheters with high cut-off membranes can be used in routine clinical practice in the NSICU, adding the possibility of macro-molecule sampling from the extracellular space during monitoring.     

Intracerebral microdialysis and bedside biochemical analysis in patients with fatal traumatic brain lesions

BACKGROUND: Microdialysis with bedside biochemical analysis was used to monitor cerebral biochemical alterations that precede and accompany increase in intracranial pressure (ICP), resulting in a complete cessation of cerebral blood flow. METHODS: Seven patients, who died due to an untreatable increase in ICP, were included. The patients originate from a large, consecutive series of severely head injured patients (n: 95) monitored with intracerebral microdialysis (perfusion rate 0.3 microl/min). One microdialysis catheter was inserted via a separate burr hole frontally to that used for the intraventricular catheter ("better" position) and one catheter was inserted into cerebral cortex surrounding an evacuated focal contusion or underlying an evacuated haematoma ("worse" position). Biochemical analyses of glucose, lactate, glycerol, urea, glutamate, and pyruvate were performed at the bedside. All samples were frozen for subsequent HPLC (high-performance liquid chromatography) analyses of amino acids and ions. RESULTS: Decreases in glucose and pyruvate and increases in lactate, glycerol, glutamate, and lactate/pyruvate (la/py) ratio characterized cerebral ischaemia. The measured markers give information regarding substrate availability (glucose), redox state of the tissue (la/py ratio), degradation of glycerophospholipids in cell membranes (glycerol), and extracellular concentration of excitatory amino acids (glutamate). In the "worse" position biochemical deterioration occurred before the increase in ICP. In the "better" position biochemical deterioration was usually observed after the increase in ICP. CONCLUSION: Changes of cerebral energy metabolism that accompany cerebral ischaemia follow a certain pattern and may be detected at the bedside by intracerebral microdialysis before the secondary damage causes an increase in ICP.     

Variations in the response of interleukins in neurosurgical intensive care patients monitored using intracerebral microdialysis

OBJECT: The aim of this study was to make a preliminary evaluation of whether microdialysis monitoring of cytokines and other proteins in severely diseased neurosurgical patients has the potential of adding significant information to optimize care, thus broadening the understanding of the function of these molecules in brain injury. METHODS: Paired intracerebral microdialysis catheters with high-cutoff membranes were inserted in 14 comatose patients who had been treated in a neurosurgical intensive care unit following subarachnoidal hemorrhage or traumatic brain injury. Samples were collected every 6 hours (for up to 7 days) and were analyzed at bedside for routine metabolites and later in the laboratory for interleukin (IL)-l and IL-6; in two patients, vascular endothelial growth factor and cathepsin-D were also checked. Aggregated microprobe data gave rough estimations of profound focal cytokine responses related to morphological tissue injury and to anaerobic metabolism that were not evident from the concomitantly collected cerebrospinal fluid data. Data regarding tissue with no macroscopic evidence of injury demonstrated that IL release not only is elicited in severely compromised tissue but also may be a general phenomenon in brains subjected to stress. Macroscopic tissue injury was strongly linked to IL-6 but not IL- lb activation. Furthermore, IL release seems to be stimulated by local ischemia. The basal tissue concentration level of IL-lb was estimated in the range of 10 to 150 pg/ml; for IL-6, the corresponding figure was 1000 to 20,000 pg/ml. CONCLUSIONS: Data in the present study indicate that catheters with high-cutoff membranes have the potential of expanding microdialysis to the study of protein chemistry as a routine bedside method in neurointensive care.     

Intracerebral microdialysis in clinical practice: baseline values for chemical markers during wakefulness, anesthesia, and neurosurgery

OBJECTIVE: The study was undertaken to measure baseline values for chemical markers in human subjects during wakefulness, anesthesia, and neurosurgery, using intracerebral microdialysis. METHODS: Microdialysis catheters were inserted into normal posterior frontal cerebral cortex in nine patients who were undergoing surgery to treat benign lesions of the posterior fossa. The perfusion rate was 1.0 microl/min during anesthesia/neurosurgery and the early postoperative course and 0.3 microl/min during the later course. Bedside biochemical analyses of glucose, pyruvate, lactate, glycerol, glutamate, and urea were performed before, during, and after neurosurgery. After the bedside analyses, all samples were frozen for subsequent high-performance liquid chromatographic analyses of amino acids. RESULTS: The following baseline values were obtained during wakefulness (perfusion rate, 0.3 microl/min): glucose, 1.7+/-0.9 mmol/L; lactate, 2.9+/-0.9 mmol/L; pyruvate, 166+/-47 micromol/L; lactate/pyruvate ratio, 23+/-4; glycerol, 82+/-44 micromol/L; glutamate, 16+/-16 mmol/L; urea, 4.4+/-1.7 mmol/L. Marked increases in the levels of all chemical markers were observed at the beginning and end of anesthesia/surgery. CONCLUSION: The study provides human baseline levels for biochemical markers that can presently be measured at the bedside during neurointensive care. In addition, some changes that occurred under varying physiological conditions are described.     

In vitro evaluation of percutaneous drainage catheters: Flow related to connections and liquid characteristics

Purpose

To evaluate the effect of catheter connections on drainage catheters’ flow rate.

Continuous Assessment of Local Metabolism by Microdialysis inCritical Limb Ischaemia

OBJECTIVE: to investigate the feasibility of using microdialysate glucose, lactate and pyruvate concentrations for grading the severity of blood flow reduction in patients with critical limb ischaemia. PATIENTS AND METHODS: microdialysis catheters were inserted (two subcutaneously and one intramuscularly) in the symptomatic limb of ten patients. To further reduce limb perfusion, the lower leg was elevated during part of the experiment. RESULTS: elevation reduced ankle and toe blood pressure and transcutaneous oxygen tension. Microdialysate glucose concentration decreased at all three catheter sites, while lactate increased in the intramuscular catheter. Two patients interrupted the elevated position prematurely due to severe pain in the foot. They had among the highest lactate levels in the horizontal position and the most marked increases following provocation. Neither initial metabolite concentrations nor concentration changes during elevation were shown to correlate to conventional methods used to assess limb perfusion. CONCLUSIONS: in patients with critical limb ischaemia microdialysis can be used without complications. A significant decrease in glucose concentration may reflect lowered blood flow in the elevated position. Metabolic response, i.e. increase in lactate concentration during profoundly reduced limb perfusion was heterogeneous, indicating an overestimation of the presence of ischaemia in some patients using current diagnostic methods.     

Formalin-induced spinal glutamate release in freely moving rats: comparison of two spinal microdialysis approaches

Two different spinal microdialysis approaches using either a linear tissue probe (LM-3) or a loop probe were explored on freely-moving rats to investigate the basal and formalin-evoked release of glutamate (Glu) in the spinal dorsal horn or in the cerebrospinal fluid (CSF). Adult male Wistar rats were implanted either with a LM-3 probe transversely through the spinal dorsal horn or with a loop probe in the CSF. After 24 hours recovery, microdialysis was initiated with perfusion of modified Ringer's solution at a flow rate of 5 microliters/min and the basal Glu concentrations were sampled for 1 hour. The effects of altering the microdialysis flow rate and perfusion solution on basal Glu release were next investigated. Following the injection of 50 microliters of formalin 5% into the hind paw, 10-min samples were collected for 90 min. The baseline levels of Glu were 0.82 +/- 0.09 microM with LM-3 probes and 5.96 +/- 0.22 microM with the loop probes. Decreasing the flow rate from 5 to 2 microliters/min increased extracellular Glu concentrations by 222.7 +/- 7.3%, whereas perfusion with artificial CSF reduced baseline Glu by 61.5 +/- 9.5% with LM-3 probes. Injection of formalin induced a short-lasting but significant increase of Glu with a similar profile and time course when using either of the microdialysis approaches. In conclusion, microdialysis in the dorsal horn or in the CSF are both effective techniques to assess the alterations in Glu release following peripheral nociceptive input. The loop probe technique in CSF is more reproducible for routine investigation of drug effects, whereas the microdialysis of the dorsal horn provides a useful tool to precisely locate where the release of the neurotransmitters occurs.     

Assessment of the lower limit for cerebral perfusion pressure in severe head injuries by bedside monitoring of regional energy metabolism

BACKGROUND: In patients with severe traumatic brain lesions, the lower limit for cerebral perfusion pressure (CPP) is controversial. The aim of this prospective study was to assess this limit from bedside measurements of cerebral energy metabolism and to clarify whether the penumbra zone surrounding a focal lesion is more sensitive to a decrease in CPP than less-injured areas. METHODS: Fifty patients with severe head injury were included after evacuation of an intracranial hematoma and/or focal brain contusion. They were treated according to intensive care routine (Lund concept), including continuous monitoring of intracranial pressure. One microdialysis catheter was inserted in less-injured brain tissue ("better" position), and one or two catheters were inserted into the boundary of injured cerebral cortex ("worse" position). Concentrations of glucose, pyruvate, and lactate were analyzed and displayed bedside and were related to CPP (n = 29,495). RESULTS: Mean interstitial glucose concentration was unaffected by the level of the CPP within the studied ranges. Increases in lactate concentration (P = 0.0008) and lactate-pyruvate ratio (P = 0.01) were obtained in the "worse" but not in the "better" position at CPP less than 50 mmHg compared with the same positions at CPP greater than 50 mmHg. CONCLUSIONS: The study results support the view that CPP may be reduced to 50 mmHg in patients with severe traumatic brain lesions, provided that the physiologic and pharmacologic principles of the Lund concept are recognized. In the individual patient, preservation of normal concentrations of energy metabolites within cerebral areas at risk can be guaranteed by intracerebral microdialysis and bedside biochemical analyses.     

Rapid volume replacement for hypovolemic shock: a comparison of techniques and equipment

The achievement of a very rapid fluid infusion rate may be critical in the resuscitation of the patient in hypovolemic shock. We studied flow rates of crystalloid and whole blood through various intravenous catheters and tubing systems. The 10-gauge Angiocath and the 8 Fr pulmonary artery introducer catheter provide flow rates equivalent to intravenous tubing (3.2 mm I.D.) inserted directly into the vein. Substantially higher flow rates can be achieved with the use of large-bore intravenous tubing (5.0 mm I.D.) connected to these catheters in place of standard intravenous tubing, allowing the infusion of 1,200-1,400 cc/minute of crystalloid and whole blood into the patient in hypovolemic shock through one intravenous catheter. Clinical trials with larger bore intravenous tubing are probably indicated.     

A Central Venous (W-B-W) Catheter for Multipurpose Vascular Access in Children

A central venous (W-B-W) catheter has been developed for vascular access in children of all ages and sizes. The catheter design and implantation technique permit nonsurgical bedside adjustment of catheter position and ease of removal. Multiple possible uses include intravenous fluid administration, blood sampling, central venous pressure monitoring, and plasma exchange therapy in addition to hemodialysis. Twenty-seven W-B-W catheters were placed in 24 patients in a 12-month period. The catheter provided adequate blood flow for hemodialysis. Seven catheters were removed nonelectively in five patients. One episode of catheter-associated sepsis occurred after renal transplantation in a patient on immunosuppressive therapy. It is concluded that the W-B-W catheter is a relatively safe, multipurpose, pain-free acute vascular access for children, which may also suffice for chronic hemodialysis.     

Assessment of the Lower Limit for Cerebral Perfusion Pressure in Severe Head Injuries by Bedside Monitoring of Regional Energy Metabolism

Background: In patients with severe traumatic brain lesions, the lower limit for cerebral perfusion pressure (CPP) is controversial. The aim of this prospective study was to assess this limit from bedside measurements of cerebral energy metabolism and to clarify whether the penumbra zone surrounding a focal lesion is more sensitive to a decrease in CPP than less-injured areas.

Methods: Fifty patients with severe head injury were included after evacuation of an intracranial hematoma and/or focal brain contusion. They were treated according to intensive care routine (Lund concept), including continuous monitoring of intracranial pressure. One microdialysis catheter was inserted in less-injured brain tissue ("better" position), and one or two catheters were inserted into the boundary of injured cerebral cortex ("worse" position). Concentrations of glucose, pyruvate, and lactate were analyzed and displayed bedside and were related to CPP (n = 29,495).

Results: Mean interstitial glucose concentration was unaffected by the level of the CPP within the studied ranges. Increases in lactate concentration (P = 0.0008) and lactate-pyruvate ratio (P = 0.01) were obtained in the "worse" but not in the "better" position at CPP less than 50 mmHg compared with the same positions at CPP greater than 50 mmHg.     

Intracerebral microdialysis in severe brain trauma: the importance of catheter location

OBJECT: Intracerebral microdialysis has attracted increasing interest as a monitoring technique during neurological/neurosurgical intensive care. The purpose of this study was to compare cerebral energy metabolism, an indicator of secondary excitotoxic injury and cell membrane degradation close to focal traumatic lesions ("penumbra zones") and in remote and apparently intact brain regions of the ipsilateral and contralateral hemispheres. METHODS: The study included 22 consecutive patients with a mean age 44 +/- 17 years and an estimated postresuscitation Glasgow Coma Scale motor score less than 5. Altogether 40 microdialysis catheters with radiopaque tips were inserted. Two catheters could not be localized on postoperative computerized tomography (CT) scans and were excluded from the analysis. The perfusates were analyzed at the patient's bedside for levels of glucose, pyruvate, lactate, glutamate, and glycerol with the aid of a CMA 600 Analyzer. The positions of eight (22%) of the 36 catheters were reclassified after a review of findings on CT scans. Except for pyruvate the values of all biochemical variables and the lactate/pyruvate (L/P) ratio were significantly different in the penumbra zone when compared with mean values found in "normal" tissue ipsilateral to the parenchymal damage and in contralateral normal tissue (p < 0.001). In the penumbra zone a slow normalization of the L/P ratio and levels of glutamate and glycerol were observed. In normal tissue these parameters remained within normal limits. CONCLUSIONS: Data obtained from intracerebral microdialysis can be correctly interpreted only if the locations of the catheters as they relate to focal brain lesions are visualized. A "biochemical penumbra zone" surrounds focal traumatic brain lesions. It remains to be proven whether therapeutic interventions can protect the penumbra zone from permanent damage.     

Cation dysfunction associated with cerebral ischemia followed by reperfusion: a comparison of microdialysis and ion-selective electrode methods

OBJECT: Disruption of ionic homeostasis during ischemia is a well-characterized event and is identified by a rise in the concentration of extracellular potassium [K+]e, with a concomitant reduction in the concentration of extracellular sodium [Na+]e. Results of clinical studies in which microdialysis has been used, however, have shown only modest changes in the levels of extracellular ions. The object of this study was to measure [K+]e and [Na+]e by using ion-selective electrodes (ISEs) and to compare these measurements with those obtained using the well-established method of microdialysis. METHODS: Fifteen Sprague-Dawley rats were separated into three groups. Five animals were subjected to a 15-minute period of ischemia, and another five animals to a 60-minute period of ischemia; animals in both of these groups received K+-free microdialysis perfusate. The third group of five rats underwent a 60-minute period of ischemia and received a reduced-Na+ microdialysis perfusate. Transient forebrain ischemia was produced by bilateral carotid artery occlusion combined with hypotension. A custom-fabricated glass Na+ electrode and a flexible plastic K+ and reference electrodes were used to monitor extracellular ion transients. Microdialysis samples were obtained with the aid of a 2-mm microdialysis probe that was perfused with K+-free mock cerebrospinal fluid at a rate of 2 microl/minute. Baseline measurements of [K+]e and [Na+]e, obtained using ISEs, were 3.41 +/- 0.09 mM and 145 +/- 7.75 mM. respectively. Ischemia resulted in a rapid accumulation of [K+]e (in animals subjected to 15 minutes of ischemia, the concentration was 41.9 +/- 13.7 mM; and in animals subjected to 60 minutes of ischemia, the concentration was 66.9 +/- 11.5 mM), with a concomitant decrease in [Na+]e (in animals subjected to 15 minutes of ischemia, the concentration was 71.7 +/- 2.9 mM; and in animals subjected to 60 minutes of ischemia, the concentration was 74.7 +/- 1.9 mM). A comparison of microdialysis and ISE methods revealed that microdialysis underestimated the [K+]e changes and was insensitive to concomitant [Na+]e alterations that occur during ischemia. CONCLUSIONS: Our results indicate that the flexible ISE is a reliable and accurate tool for monitoring ionic dysfunction that accompanies brain injury.     

Bedside Tunneled Dialysis Catheter Removal—A Lesson Learned From Nephrology Trainees

Semi‐permanent dual‐lumen tunneled (or tunneled‐cuffed) hemodialysis catheters (TDC) are increasingly utilized during renal replacement therapy, while awaiting permanent access maturation or renal recovery. Although there is a wealth of literature focused on placement, infection prevention, and maintenance of catheter patency, circumstances and indications for TDC removal are less well understood. Timely removal of these catheters is an important management decision, with the length of TDC duration representing the largest cumulative risk factor for catheter‐associated blood stream infections. Waiting for assistance from surgical or radiological services—which may not be available in all hospitals—may result in delays in services and potential harm to the patients. Imparting and maintaining procedural skills to remove infected TDC may be very valuable for training programs in clinical nephrology. In this article the current literature on bedside TDC removal, including potential anticipated complications during removal, are reviewed. To date, the authors have documented successful implementation of bedside TDC removal in training programs from two different settings, including both in‐ and outpatients and with trainee involvement. In summary, training general nephrologists for bedside TDC removal will afford immediate removal of infected hardware in ill patients and avoid potential delays in outpatient setting.     

Computational and experimental study of proximal flow in ventricular catheters. Technical note

The treatment of hydrocephalus with shunt insertion is fraught with high failure rates. Evidence indicates that the proximal holes in a catheter are the primary sites of blockage. The authors have studied ventricular catheter designs by using computational fluid dynamics (CFD), two-dimensional water table experiments, and a three-dimensional (3D) automated testing apparatus together with an actual catheter. With the CFD model, the authors calculated that 58% of the total fluid mass flows into the catheter's most proximal holes and that greater than 80% flows into the two most proximal sets of holes within an eight-hole catheter. In fact, most of the holes in the catheters were ineffective. These findings were experimentally verified using two completely different methodologies: a water table model of a shunt catheter and a 3D automated testing apparatus with an actual catheter to visualize flow patterns with the aid of ink. Because the majority of flow enters the catheter's most proximal holes, blockages typically occur at this position, and unlike blockages at distal holes, occlusion of proximal holes results in complete catheter failure. Given this finding, new designs that incorporated varying hole pattern distributions and size dimensions of the ventricular catheter were conceived and tested using two models. These changes in the geometrical features significantly changed the entering mass flow rate distribution. In conclusion, new designs in proximal ventricular catheters with variable hole diameters along the catheter tip allowed fluid to enter the catheter more uniformly along its length, thereby reducing the probability of its becoming occluded.     

Minimally invasive retrieval of knotted nonstimulating peripheral nerve catheters

OBJECTIVE: Continuous peripheral nerve blockade is rapidly becoming the technique of choice for the management of postoperative orthopedic pain. However, the insertion of perineural catheters may be associated with complications, including catheter kinking and knotting. A knotted catheter may be difficult or impossible to remove at the patient bedside, requiring surgical excision under general anesthesia. We describe a previously unreported minimally invasive technique of retrieving knotted peripheral nerve catheters and avoiding the need for surgical intervention. Although the described technique has been used by interventional radiologists for the removal of knotted intravascular devices, it has not been previously described for the retrieval of knotted perineural catheters. BRIEF REPORT: The Mayo Clinic Acute Pain Service database was queried and patients identified with knotted peripheral nerve catheters during the 3-year period from January 2003 to January 2006. The medical records of all identified patients were retrospectively reviewed and details of catheter placement including catheter type and location, size (gauge), ease of placement, distance threaded, and duration of use recorded. During the study period, 5,964 nonstimulating peripheral nerve catheters were placed. Of these, 8 (0.13%) patients experienced catheter knotting resulting in difficult or impossible catheter removal at the bedside. Seven (88%) of the 8 catheters were successfully removed by using a minimally invasive technique of catheter retrieval using guided fluoroscopy. The remaining catheter was removed at the bedside with patient repositioning. CONCLUSIONS: The knotting of peripheral nerve catheters is a relatively uncommon phenomenon, occurring in only 0.13% of patients. However, because the use of perineural catheters has increased within anesthesia practice, clinicians may begin to encounter these complications with greater frequency. Practitioners should be aware of surgical alternatives, including guided-fluoroscopic techniques, when simple catheter traction or tension proves unsuccessful at the patient bedside.     

Clinical trials of the T-fluted (Ash Advantage) peritoneal dialysis catheter

The Ash Advantage is a T-shaped peritoneal catheter with a single transabdominal tube joining to a tube lying against the parietal peritoneum. Segments with long flutes (grooves) serve as fluid ports rather than 1-mm diameter holes. The folded catheter is placed through the expandable Y-TEC Quill positioned peritoneoscopically, similar to the procedure for a conventional Tenckhoff catheter. In a clinical study, we placed 18 Ash Advantage ("Advantage") catheters, 8 in patients with prior hydraulic or infectious complications of Tenckhoff catheters and 10 in patients initiating peritoneal dialysis. Mean follow-up has been 8.4 months. Outflow rate for the Advantage catheters is uniformly higher than for Tenckhoff catheters at 220 +/- 100 mL/min for the first 5 minutes and 145 +/- 72 mL/min for the next 5 minutes, with outflow completed in 6 to 15 minutes. Variation of outflow volumes for similar exchanges in the same patient is +/- 3% to 5%, much less than with Tenckhoff catheters. Four catheters failed after placement, each for a different reason including outflow failure because of preexisting intraperitoneal adhesions, preexisting peritonitis failing to clear, tubing kink during placement, and catheter break after a freak accident. Life-table analysis of the production version of the catheter in study patients and 12 additional unselected patients indicates a 90% survival at 12 months. In long-term use, the fixed position of the cuffs of this catheter may avoid catheter extrusion, pericatheter hernias, and pericatheter leaks. Multiple fluted ports appear to diminish omental attachment. The catheter may be a useful alternative to conventional Tenckhoff catheters in patients at high risk of catheter failure or in standard peritoneal dialysis patients.     

Percutaneous implantation of cerebral microdialysis catheters by twist-drill craniostomy in neurocritical patients: description of the technique and results of a feasibility study in 97 patients

Cerebral microdialysis is increasingly used to monitor several types of neurocritical patients. This study presents the technique used in our unit for percutaneous implantation of cerebral microdialysis catheters using a small twist-drill craniostomy that can be performed in the intensive care unit (ICU). We also present the results of this technique in 89 head-injured patients and in eight patients with a malignant middle cerebral artery (MCA) infarction. One hundred and twenty-two cerebral microdialysis catheters were implanted in the 97 patients included in this study. One cerebral microdialysis catheter was implanted in the less damaged hemisphere of 67 head-injured patients with a diffuse brain injury. An additional microdialysis catheter was inserted in the pericontusional parenchyma of 22 patients with brain contusions. In five of the eight patients with a malignant MCA infarction, only one microdialysis probe was inserted in the penumbral zone. In the remaining three patients, two cerebral microdialysis catheters were implanted in the same hemisphere (one in the ischemic core and the other in the penumbra). Technical problems were detected in 18 (15%) of the 122 microdialysis catheters implanted and were more frequent during the initial period of using microdialysis in our unit. In four patients (3% of implanted catheters), follow-up computed tomography (CT) scans showed a small intracerebral blood collection (always 相似文献   

Potential use of quantitative bedside CBF monitoring (Xe-CT) for decision making in neurosurgical intensive care

During a 3-year period, mobile xenon-computerized tomography (Xe-CT) for bedside quantitative assessment of cerebral blood flow was used as an integrated tool for decision making during the care of complicated patients in our neurosurgical intensive care units (NSICU), in an attempt to make a preliminary evaluation regarding the usefulness of this method in routine work in the neurosurgical intensive care. With approximately 200 studies involving 75 patients, we identified six different categories where the use of bedside Xe-CT significantly influenced (or, with more experience, could have influenced) the decision making, or facilitated the handling of patients. These categories included identification of problems not apparent from other types of monitoring, avoidance of adverse effects from treatment, titration of standard treatments, evaluation of the vascular resistance reserve, assessment of adequate perfusion pressure and better utilization of resources from access to the bedside cerebral blood flow (CBF) technology. We conclude that quantitative bedside measurements of CBF could be an important addition to the diagnostic and monitoring arsenal of NSICU-tools.     

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.