Emergency burr holes: "How to do it"

This paper describes a simple approach to emergency burr hole evacuation of extra-axial intracranial haematoma that can be used in the uncommon situation when life saving specialist neurosurgical intervention is not available.

created media interest [3]. Although there have been significant technical advances in the safety of the procedure since the time of "exploratory" burr holes, there has simultaneously been a reduction in the number of surgeons either having experience in or being willing to perform the procedure. A number of general surgeons working in remote areas of Australia are more confident in performing simple neurosurgical procedures even though they may have no greater training than general surgeons closer to neurosurgical centres [4]. This may paradoxically result in more optimal management in more remote regions. With adequate training and skill retention, burr hole drainage of acute extradural haematomas can be performed by non-neurosurgeons [5]. Despite this, We must stress that this procedure should only be performed if it is not possible to transfer a patient to a more appropriate centre in a timely manner and that this procedure must not delay transfer. A previous study has demonstrated that attempts by local, non-trained personnel can result in delay and worse outcome [6]. This must not occur.
The authors describe a simple approach to burr hole placement. The important considerations here are that the burr hole should be targeted (not exploratory), should be done using the correct tools (and in particular a perforator drill bit with a clutch mechanism, Figure 1) and should not unduly delay the transfer of the patient who will usually still require an urgent craniotomy.
Emergency "Burr Hole" Craniostomy Indication Patient with reduced GCS (< 8) with imaging evidence of an extra-dural haematoma causing midline shift and unequal pupils when timely neurosurgical intervention is not possible. Attempts should always be made to discuss the images and necessity for a procedure with a neurosurgeon.

Contraindications
• GCS > 8 • No Imaging* • Neurosurgical intervention available in a reasonable time frame. * Very high clinical suspicion (e.g. a palpable fracture with an ipsilateral fixed pupil), in an area remote from CT imaging may be an exception to this. In the future devices such as the Infrascanner™ (a handheld portable device designed to detect extra-axial haematoma using near infra-red light) may lessen the need for formal CT imaging in the emergency setting. Currently however, a CT scan should always be performed, especially if a non-neurosurgeon is contemplating performing the procedure.

Equipment
The surgical equipment is standard (knife, self retainer, swab, drill, sharp and blunt hock and second knife). If possible, bipolar diathermy should be set up. The hand held drill (which can be a Hudson-Brace or air powered drill) should have a specific perforator (e.g. a 14 mm perforator clutch drill bit (26-1221, Codman, Johnson and Johnson, Chicago, USA), Figure 1. All equipment should be stored together ready for use in an emergency department or operating theatre. Importantly, in preparation, check the drill bit fits the drill.

Procedure
Note: It may be useful to nominate a person to read out the components of this guide as the procedure is being performed 1) Ensure indications are appropriate 2) Ensure patient is supine and physiologically optimised (intubated, ETCO2 4.5kPa, normotensive, cspine protection, mannitol/hypertonic saline as directed by neurosurgeon).
3) Confirm position of haematoma on CT scan and be able to view images while performing procedure ( Figure 2). Mark the patients shoulder that corresponds to the side of the haematoma. Haematomas most commonly occur in the temporal region. Frontal, parietal, and rarely posterior fossa haematomas also occur. Figure 3 demonstrates the standard position of burr holes for each of these situations. These positions can be modified slightly in light of the scan. It is important that the burr hole is over the centre of the haematoma. Count down the number of slices from the top (and multiple by slice thickness) to the centre of the haematoma to calculate how many centimetres below the vertex the burr hole should be. 4) Shave a strip of approximately 5 cm of hair where the burr hole is to be made. 5) Mark a 3 cm line of incision. 6) Clean the area with betadine/chlorhexidine 7) Make an incision straight down to bone. Bleeding (e.g. from the superficial temporal artery) can be controlled with direct pressure while continuing the procedure. 8) Push the periosteum off the bone with knife/swab 9) Insert self-retaining retractor 10) Push down firmly with drill and start drilling keeping drill perpendicular to the skull. Ensure an assistant is holding the head still and ideally apply saline wash as you drill. 11) Keep going -do NOT stop (as this will disengage the clutch mechanism which can be difficult to re-engage manually) 12) Drill until the drill bit stops spinning. Remove drill. 13) Use blunt hook to remove remaining bone fragments. 14) Extradural blood should now escape. 15) If the blood is subdural, very carefully open the dura using a sharp hook to tent the dura up, and a new sharp knife to incise the dura in a cruciate manner. Subdural blood is likely to be more clotted and difficult to extrude than extradural. Manual removal of clot (e.g. with forceps or very careful suction) could be considered, but may damage brain and is unlikely to remove sufficient haematoma. If no blood is found either extra or sub-durally, stop, check side, and check location of hole. DO NOT DELAY TRANSFER. 16) If fresh blood is continuing to ooze from the wound, do NOT try to tamponade. Leaving the selfretainer in place may stop the bleeding. Try to diathermy skin edges; if not available, apply direct pressure to wound edges during transfer.

Discussion
The cranial procedure of burr hole placement has become the sole domain of neurosurgeons particularly as they can deal with surgical complications. As such, non-neurosurgeons are no longer familiar with the technique. This creates a therapeutic vacuum for patients remote from specialist care who meet the criteria for urgent burr hole drainage.
Central to the ability of non-neurosurgeons to successfully performing burr holes is the development of clutch drill-bits (Figure 1). These cause the drill to disengage on penetrating the inner table of the skull so that the risk of "plunging" is minimised making the procedure considerably safer. If a haematoma is not relieved, the patient should not have come to any additional harm providing transfer to a neurosurgical centre is not significantly delayed. In remote areas of Australia,  when such neurosurgical procedures are performed by non-neurosurgeons, outcomes are acceptable [7]. Even in less remote situations non-neurosurgeons in district general hospitals in the UK have historically carried out emergency craniotomy [8].
For many years it has been known that earlier surgical intervention is of benefit in the management of head trauma when an extra-axial collection can be removed [9]. In the future, near infra-red/ultrasound devices or mobile CT, may mean that extra-axial collections can be detected in remote locations. This will not be of benefit unless the time to surgical relief of increased Intracranial Pressure is also shortened.
While attempting to remove the mystique and anxiety surrounding emergency burr hole placement, we emphasise the importance of avoiding inappropriate intervention. However, when faced with a situation where mortality approaches 100%, a simple technique, using the correct equipment can be robust, safe and life-saving even in the hands of non-specialists.