Cerebral microdialysis methodology—evaluation of 20 kDa and 100 kDa catheters

Abstract

Microdialysis monitoring of cerebral metabolism is now performed in several neuro-intensive care units. Conventional microdialysis utilizes CMA70 catheters with 20 kDa molecular weight cut-off membranes enabling the measurement of small molecules such as glucose, lactate, pyruvate and glutamate. The CMA71 100 kDa molecular weight cut-off microdialysis catheter has recently been introduced to allow detection of larger molecules such as cytokines. The objective of this study was to perform in vitro and in vivo testing of the CMA71 microdialysis catheter, comparing its performance with the CMA70. In vitro comparison studies of three of each catheter using reference analyte solutions, demonstrated equivalent recovery for glucose, lactate, pyruvate and glutamate (range 94-97% for CMA70 and 88-103% for CMA71). In vivo comparison involved intracranial placement of paired CMA70 and CMA71 catheters (through the same cranial access device) in six patients with severe traumatic brain injury. Both catheters were perfused with CNS Perfusion Fluid without dextran at 0.3 microl min-1 with hourly sampling and bedside analysis on a CMA600 microdialysis analyser. The two catheters yielded equivalent results for glucose, lactate, pyruvate, glutamate and lactate/pyruvate ratio. CMA71 microdialysis catheters can, therefore, be used for routine clinical monitoring of extracellular substances, as well as for their intended research role of larger molecular weight protein sampling.

Microdialysis as an Important Technique in Systems Pharmacology—a Historical and Methodological Review

“…The development of microdialysis has during later years focused on increasing the cut-off of the probe membranes, in order to increase the utility of the technique for studying larger molecules (90). With increasing cut-off up to 1 or even 3 MDa, there is an increased sensitivity of the method to pressure differences between inlet and outlet tubings and one has to check that flow rate into and out from the site of measurement are the same.…”

Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage: Relation to Cerebral Perfusion Pressure and Metabolism

“…Both the 20 and 100 kD catheters show equal results for substrate concentrations of molecules below 20 kD [20]. Insertion depth was approximately 10-15 mm from dura level.…”

Inpatient Hyperglycemia Following Aneurysmal Subarachnoid Hemorrhage: Relation to Cerebral Metabolism and Outcome

“…The correct positioning of the catheter tip was verified postoperatively by CT. Catheters were perfused with sterile Ringer's solution at a flow rate of 0.3 ll/ min. Molecules from the cerebral extracellular fluid enter into the catheter, with an estimated recovery of 0.65-0.72 (recovery in 20-and 100-kD catheters is comparable for molecules up to 20 kD, including all the measured substances in this study) [18,19]. On the outlet tube, perfusates were collected in microvials and analyzed hourly at bedside in a mobile photometric, enzyme-kinetic analyzer (CMA 600).…”