The objective of this study is to demonstrate that scalp nerve blocks ("scalp freezing"), performed at the end of supratentorial brain surgery, will reduce post-operative pain, opioids side effects, and the time required for post-anaesthesia care unit (PACU)/Intensive Care Unit (ICU) and hospital discharge.

The proposed study is a randomized, placebo-controlled, triple-blinded, parallel-group clinical trial. Patients will be recruited from the neurosurgical population at St. Michael's Hospital.

The inclusion criteria are:

• Adults aged 18 years and over;

• scheduled for one of the following supratentorial craniotomy:

  1. resection of a brain tumour
  2. clipping of an un-ruptured cerebral aneurysm
  3. excision of an artero-venous malformation (AVM), or
  4. removal of an epileptic focus

• ASA physical status < IV

Intervention group: scalp nerve blocks with 20 ml of bupivacaine 0.5% + epinephrine 1:200,000 (divided among the different injection sites) at the end of surgery and before removal of the endo-tracheal tube. Control group: equal injections with 20 ml of saline + epinephrine 1:200,000 (at same time). In both study arms, post-operative rescue analgesia will be provided with hydromorphone patient-controlled analgesia (PCA).

The primary outcome of this study will be the 24h post-operative pain score as assessed by the visual analogue scale (VAS).

Important secondary outcomes will be:

• the total PCA hydromorphone consumption in the first 24 and 48 post-operative hours;
• the incidence of nausea and vomiting in the first 24 and 48 post-operative hours;
• time to reach discharge eligibility from the PACU/ICU and hospital length of stay.

Patients will be asked to rate their pain using the VAS at 30 min, 1, 2, 4, 8, 12, 18, 24, and 48 h, postoperatively by the research coordinator/bedside nurse. Pain will be also assessed at 5, 30 and 60 days postoperatively with the use of a Numeric Rating Scale (0-10).

Inclusion Criteria:

• adults aged 18 years and over;

• patients scheduled for elective craniotomy under general anaesthesia for one of the following surgeries:

  • resection of a supratentorial brain tumour,
  • clipping of an un-ruptured supratentorial cerebral aneurysm,
  • excision of a supratentorial arterio-venous malformation (AVM),
  • removal of an epileptic focus under general anaesthetic.

• ASA physical status < IV.

Exclusion Criteria:

• history of significant coronary artery disease (NYHA class III or IV) which would contraindicate the use of epinephrine;
• presence of pain related to the intracranial pathology (e.g. tumour pain) since it could make difficult the discrimination between the tumour pain itself and the surgery related pain;
• current history of alcohol abuse or recreational drug abuse;
• active psychotic disorder;
• history of chronic pain requiring chronic opioids use (patients on opioids for > 2 weeks);
• known or suspected addiction to narcotic substances;
• presence of any acute distracting pain;
• history of migraines;
• inability to understand or incapacity to use the VAS;
• proven or suspected allergy to local anaesthetics;
• craniotomy incision extending beyond the field of the block;
• predicted need for postoperative ventilation;
• history of scalp paresthesia or scalp scarring that may preclude normal nerve anatomy;
• previous craniotomy or cranial irradiation;
• history of malignant hyperthermia, which would contraindicate the anaesthesia maintenance protocol of this study;
• pregnancy.