• Burr hole craniotomy is a minimally invasive form of an ancient surgical procedure known as "trephination."
• It is performed to drain epidural (EDH) or subdural (SDH) hematomas, which may be either acute or chronic in nature.
• The scalp is reflected over the area of the hematoma to expose the skull, followed by the use of a drill to create the hole.
• In the case of an epidural clot, coagulum is simply removed and the wound is closed; clot expansion tends to be restrained by the compartments formed by dura adherent to cranial sutures.
• for SDHs, the dura is incised, as clot can be diffuse due to the lack of septations in the subdural space. Irrigation may be used to remove the hematoma; a drain may be placed to allow for postoperative drainage.
• In extreme, life-threatening conditions, burr holes may be performed with a simple, hand-powered, manual twist drill.

• Supine with the operating table turned 90 or 180°, depending on surgical preference and physical layout of the OR
• The patient's face points to the ceiling if a frontal incision is used. Alternatively, the patient's face is turned to the anesthesia team if a right or left temporal incision is performed. Mayfield pins are often used, but the head may also be rested upon sterile towels.
• Rarely, prone position may be required for infratentorial exposure (cerebellar clot).

• Scalp incision in the frontal, temporal, or base of skull
• Small, dime-sized hole made with twist drill or power drill
• 80% of acute EDHs are located below an existing fracture line.
• Incision may or may not be irrigated or drained (1) [A].

60 minutes; longer if substantial bleeding is encountered

Minimal, unless the patient is coagulopathic

• 23-hour admission for serial neurologic examinations, perhaps longer depending on comorbidities
• Repeat, post-procedural CT scans are common in those patients with abnormal baseline neurologic status (e.g., a demented patient from a nursing home).

• Manual, hand-twist drill
• Power drill
• Occasionally, endoscopic visualization is employed in nonemergent situations.

Incidence

Acute post-traumatic SDH and EDH: 0.83/100,000 population

Prevalence

• Acute post-traumatic SDH and EDH: Median age 45 years, 80% male
• Chronic SDH: Median age 60 years; male:female ratio 5.63:1

• Acute post-traumatic SDH and EDH: 63% good outcome at 6 months
• Chronic SDH: 95.6% good outcome following surgery (most surgeries performed under local anesthesia with sedation)

Acute post-traumatic SDH and EDH: 23% mortality, greatest likelihood of death if age >60 and surgery for acute SDH (2) [A], (3) [A]

History

• Head trauma
• Anticoagulant therapy
• Acquired disorders of hemostasis NOT involving anticoagulant therapy (e.g., TTP)
• Concomitant drug or alcohol use
• Tobacco use (these patients may have significant carboxyhemoglobin levels and may also cough upon emergence)

Signs/Physical Exam

• Trauma (especially orofacial trauma with cervical collar present)
• Focal neurologic signs
• Obtundation
• In elderly patients, look for signs of a pacemaker or an AICD.

Labs/Studies

• Hematocrit, platelet count, INR
• Creatinine, blood glucose, LFTs
• A type and screen should be available if one anticipates the need for component therapy.
• EKG or CXR may be helpful in stable patients with multiple comorbidities.
• In deteriorating patients, the anaesthetist may need to progress without any laboratory studies at all and obtain them intraoperatively later.

• Doses of premedicants must NOT be so large as to obscure the neurologic exam or depress spontaneous ventilation; a minimalist approach is best.
• Acid aspiration prophylaxis is warranted in those patients who have not fasted.

• Urgency of surgery may preclude truly informed consent.
• Patients with chronic SDHs may have a long-standing abnormal neurologic examination which will preclude their giving informed consent themselves; a surrogate may be needed.

• Usually, coverage for common skin flora is sufficient.
• In trauma patients with dirty wounds, polymicrobial coverage is warranted.

• General endotracheal anesthesia for the multiple trauma patient or the uncooperative patient
• Cooperative patients with chronic SDH may be managed with a scalp block and judicious intravenous sedation.

• Standard ASA monitors
• Invasive arterial and central venous monitoring may be warranted in some high-acuity patients.

• Thiopental, propofol, or etomidate is chosen on the basis of the patient's hemodynamic status.
• Rapid-sequence induction with succinylcholine and cricoid pressure may be indicated.
• Esmolol may be used to attenuate the sympathetic response to laryngoscopy and intubation.
• Scalp block and intravenous sedation in selected patients who are cooperative and who have fasted; a remifentanil or dexmedetomidine infusion may be considered (4) [A].

• Inhalational or intravenous anesthesia, or both may be utilized.
• Sedation may be maintained with an infusion of remifentanil or dexmedetomidine.

• Awake extubation should be performed if the patient is considered a "full stomach"; intravenous lidocaine and esmolol may be useful in the suppression of coughing and emergence hypertension, respectively.
• Insertion of an LMA or a deep extubation may be considered in selected patients who have fasted, to avoid coughing and bucking.