Technical notes on the placement of cerebral microdialysis: A single center experience

Abstract

Background: Cerebral microdialysis enables monitoring of brain metabolism and can be an important part of multimodal monitoring strategies in a variety of brain injuries. Microdialysis catheters can be placed in brain parenchyma through a burr hole, a cranial bolt, or directly at the time of an open craniotomy or craniectomy. The location of catheters in relation to brain pathology is important to the interpretation of data and guidance of interventions.

Methods: Here we retrospectively review the use of cerebral microdialysis at a US Regional Medical Center between March 2018 and February 2022 and provide detailed descriptions and technical nuances of the different methods to place microdialysis catheters.

Results: Eighty two unique microdialysis catheters were utilized in 52 patients. 35 (42.68%) were placed via a quad-lumen bolt and 47 (57.32%) were placed through craniotomies. 27 catheters (32.93%) were placed in a perilesional location, 50 (60.98%) were located in healthy tissue, and 6 (7.32%) were mispositioned. No significant difference was seen between placement by bolt or craniotomy in regard to perilesional location, mispositioning, or complications.

Conclusion: With careful planning and thoughtful execution, cerebral microdialysis catheters can be successfully placed though a variety of strategies to optimize and individualize brain monitoring in different clinical settings. This paper provides a detailed guide for the various methods of catheter placement to help providers begin or expand their use of cerebral microdialysis.

Keywords: brain metabolism; cerebral microdialysis; multimodal brain monitoring; neurocritical care; traumatic brain injury.

Figure 1

Example of the gold probe tip on CT a patient who underwent hemicraniectomy. Note the hypodense linear catheter (arrow), and hyperdense gold filament tip (*).

Figure 2

Stepwise placement through craniotomy. (A) First, a 2 mm incision is made with a 15 blade at the intended exit site. (B) An instrument such as a Kelly clamp is used to tunnel beneath the galea and create a pathway for the microdialysis catheter. (C) The protection tube will be removed from the catheter after tunneling, however we have found it best to loosen the protection tube by partially unscrewing the base prior to tunneling to facilitate the process. (D) The catheter is then tunneled through the subgaleal tract toward the craniotomy site, after which the protection tube is removed. (E) The fixation cuff is positioned firmly within the skin opening to serve as a plug to occlude the exit site. (F) The fixation cuff is then secured with 4-0 nurolon suture (Ethicon, NJ, USA). (G) The site of corticectomy is chosen to avoid surface vessels and after cauterization of the pia with bipolar cautery, a 1mm corticectomy is made with an 11 blade. (H) The catheter is then inserted perpendicular to the cortical surface. (I) The catheter length from tip to fixation cuff is a set length, and the depth which the probe tip sits is dependent on the length tunneled beneath the galea and the distance of the corticectomy from the edge of the craniotomy and this must be taken into consideration.

Figure 3

Stepwise schematic of suturing method. (A) With the fixation cuff lodged within the skin opening, a 4-0 Nurolon suture (Ethicon, NJ, USA) is threaded in a purse-string fashion around the base of the cuff. (B) The positioning of the suture sites is chosen such that when secured, the suture tightens around the skin opening and creates a watertight seal around the cuff. (C) The ends of the suture are then wrapped around the fixation cuff and tied. Care should be taken at this point to ensure the suture is tight enough to prevent egress of CSF through the cuff, however not so tight as to preclude flow of dialysate though the catheters. (D) The ends of the suture are wrapped around the cuff once again, tied, and ends trimmed. (E) A second 4-0 Nurolon suture is then threaded under the cuff slightly distal to the skin exit site to provide a second point of fixation. (F) This is secured, again with consideration to tightness. (G) The ends of the suture are wrapped around the cuff once again, tied, and ends trimmed. (H) The end result is a watertight seal around the cuff to prevent leakage of CSF while also providing two points of fixation to guard against dislodgement.

Figure 4

Stepwise placement at bedside through a Quad Lumen Bolt (Hemedex, Cambridge, US). (A) A small incision is made at the location of desired probe placement to minimize skin trauma. (B) A standard twist drill is used to drill a burr hole. The size of the drill bit depends on which bolt is being used and is typically included in the Bolt kit. (C) A durotomy is made using an 11 blade or 18-gauge needle. (D) The bolt is screwed into the burr hole. It should be deep enough to be firmly attached to the bone. (E) The sensor introducer is advanced through the desired bolt lumen where it is secured to the luer fitting and (F) the stylet is removed. (G) The microdialysis catheter is then advanced and (H) secured to the introducer. (I) After placement of microdialysis catheters, other monitors may be placed though the additional lumen if desired.

Figure 5

Stepwise placement at bedside through a burr hole. (A) An incision ~3 cm is made at the location of desired probe placement. (B) A burr hole is created using a standard twist drill. A larger drill bit can be used if placement of multiple probes is desired, however a smaller bit will provide adequate access for a single microdialysis catheter. (C) A 2 mm incision is made with a 15 blade at the intended exit site and an instrument such as a Kelly clamp is used to tunnel beneath the galea toward the incision to create a pathway for the microdialysis catheter. (D) The protection tube will be removed from the catheter after tunneling, however we have found it prudent to loosen the protection tube by partially unscrewing the base prior to tunneling to facilitate the process. (E) An 18 guage needle or 11 blade is used to create a small corticectomy within the burr hole. (F) The catheter is then tunneled through the subgaleal tract toward the craniotomy site, positioning the fixation cuff as a plug in the skin opening, after which the protection tube is removed. (G) The catheter is then inserted perpendicular to the cortical surface. (H) The fixation cuff is then secured with 4-0 nurolon suture (Ethicon, NJ, USA). (I) The incision is then closed in the usual fashion with sutures or staples.