This study shows that in craniotomy patients using a skull pin head holder, an ultrasound-guided scalp block reduces perioperative opioid consumption, improves hemodynamic stability, and decreases the inflammatory response.

Craniotomy is a surgical procedure performed to access brain tissue or vascular structures through temporary removal of a portion of the skull (1). The primary goal of neuroanesthesia is to preserve cerebral autoregulation, prevent increases in intracranial pressure, and maintain adequate cerebral perfusion pressure by controlling autonomic nervous system activation induced by surgical stress and nociceptive stimuli (2).

The pin head holder (Mayfield type), which is used to stabilize the surgical field during intracranial procedures, generates intense nociceptive stimulation due to the dense sensory innervation of the scalp. This stimulation may lead to sudden increases in blood pressure and heart rate, thereby raising intracranial pressure (3). Although deep levels of anesthesia and high-dose opioids are commonly used to control this hemodynamic response, such approaches may result in undesirable perioperative outcomes, including respiratory depression, postoperative nausea and vomiting, and prolonged recovery time associated with increased opioid consumption (4,5).

Scalp block is an effective regional anesthesia technique frequently used in intracranial surgery and is based on blocking the sensory nerves of the scalp using local anesthetic agents (3). This technique targets the supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, greater occipital, and lesser occipital nerves, thereby reducing the transmission of painful stimuli to the central nervous system (6). Scalp block was first described by Pinosky et al. in 1996, and it has been demonstrated that bupivacaine-based scalp block reduces increases in blood pressure and heart rate associated with pin head holder placement and decreases intraoperative anesthetic requirements (3,6).

The use of ultrasonography (USG) in scalp block enhances block accuracy through real-time visualization of superficial nerves and vascular structures, ensures appropriate distribution of local anesthetics within fascial planes, and reduces the risk of complications such as intravascular injection and local anesthetic systemic toxicity (7).

In addition to hemodynamic alterations, surgical trauma and pain also trigger a systemic inflammatory response. During this process, changes in neutrophil, lymphocyte, and platelet counts are reflected in peripheral blood parameters. The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic inflammatory response index (SIRI), and systemic immune-inflammation index (SII) are used as indicators of surgical stress and inflammation (8,9).

Preoperative scalp block suppresses surgery-related stress responses, reduces intraoperative opioid consumption, improves perioperative hemodynamic stability, and decreases postoperative analgesic requirements (4,10). Furthermore, scalp block may modulate the inflammatory response by reducing proinflammatory cytokines such as interleukin-6 (IL-6) and C-reactive protein (CRP) (9,11). However, studies comprehensively evaluating the effects of scalp block on inflammatory responses using different biomarkers remain limited in the literature.

Ultrasound-guided scalp block is one of the regional analgesia techniques frequently used in our clinic during craniotomy procedures. In this observational study, we aimed to evaluate the combined effects of preoperative ultrasound-guided scalp block on perioperative hemodynamic responses, intraoperative opioid requirements, and surgery-related systemic inflammatory responses in patients undergoing intracranial surgery with pin head holder placement.

Following approval from the institutional ethics committee, this study will be conducted at Fatih Sultan Mehmet Training and Research Hospital between February 2026 and February 2027. A total of 60 patients aged ≥18 years, classified as American Society of Anesthesiologists (ASA) physical status I-III, scheduled for elective intracranial surgery under general anesthesia with placement of a Mayfield-type pin head holder, and who provide written informed consent will be included.

Based on the power analysis, to test statistical significance with a power of 90% (0.90) and a significance level of 5% (α = 0.05), assuming an effect size (Cohen's d) of 0.91 for total opioid consumption between groups, the minimum required sample size was determined as n = 27 per group. Sample size calculations were performed using G*Power version 3.1.9.4 (Franz Faul, Kiel University, Kiel, Germany) (12). All eligible patients will be informed in detail about the study during the preoperative period, and written informed consent will be obtained. In this prospective observational study, patients will be divided into two groups of 30 participants each.

Group S: Patients in the scalp block group will receive a preoperative ultrasound-guided scalp block, routinely performed in our clinic, after induction of general anesthesia and endotracheal intubation and before pin head holder placement and surgical incision.

Group C: Patients in the control group will receive standard general anesthesia management, and local infiltration anesthesia routinely performed by the surgical team will be administered before pin head holder placement and surgical incision.

Patients with known allergy to local anesthetic agents; coagulopathy; active anticoagulant therapy; local infection at the injection site; pregnancy or breastfeeding; chronic opioid use for more than three months or chronic pain syndrome; severe psychiatric disorders interfering with pain assessment; need for emergency surgery; active infection; rheumatologic disease; active or treated hematologic disease; active systemic malignancy or history of malignancy within the past five years; use of biological agents, chemotherapy, or systemic corticosteroids within the past 30 days; use of nonsteroidal anti-inflammatory drugs within 24 hours before surgery; advanced organ failure (New York Heart Association class III-IV heart failure, Child-Pugh class C liver failure, or estimated glomerular filtration rate <30 mL/min); communication difficulties preventing Numeric Rating Scale (NRS) assessment; and those who refuse to participate will be excluded from the study.

Upon arrival in the operating room, standard monitoring including electrocardiography, peripheral oxygen saturation (SpO₂), noninvasive blood pressure, and bispectral index (BIS) monitoring will be applied. Following preoxygenation with 100% oxygen via face mask for 3 minutes, anesthesia induction will be performed under BIS monitoring using propofol 2-2.5 mg/kg, fentanyl 1-2 μg/kg, and rocuronium 0.6 mg/kg for neuromuscular blockade. After endotracheal intubation, patients will be connected to mechanical ventilation in volume-controlled mode with a tidal volume of 6-8 mL/kg. End-tidal carbon dioxide (ETCO₂) will be maintained between 30 and 35 mmHg. Anesthesia maintenance will be achieved using total intravenous anesthesia with propofol (50-200 μg/kg/min) and remifentanil (0.05-0.2 μg/kg/min) in a mixture of 50% oxygen and air at 2 L/min, targeting BIS values between 40 and 60. After standard induction, a 20-gauge arterial catheter will be inserted into the radial artery for invasive arterial pressure monitoring.

In Group S, the preoperative scalp block will be performed after induction and intubation and before pin head holder placement, with the patient in the supine position, as routinely practiced by the anesthesia team in our clinic. Using a high-frequency linear ultrasound probe, the supraorbital, supratrochlear, auriculotemporal, zygomaticotemporal, lesser occipital, and greater occipital nerves will be identified under ultrasonographic guidance, and after negative aspiration, 2-3 mL of 0.25% bupivacaine will be injected for each nerve. The procedure will be performed bilaterally, and the total volume of local anesthetic will be limited to 20 mL (0.25% bupivacaine). The spread of the local anesthetic will be confirmed by ultrasonography. No additional local anesthetic will be administered by the surgical team.

In the preoperative period, demographic data including age, sex, height, weight, body mass index, and ASA classification will be recorded. Intraoperative hemodynamic parameters, including systolic, diastolic, and mean arterial pressure, heart rate, peripheral oxygen saturation, ETCO₂, and BIS values, will be recorded at the following time points: T0, preoperative baseline; T1, after induction and intubation; T2, after scalp block; T3, during pin head holder placement; T4, after pin placement; T5, during skin incision; T6, at 15, 30, 60, and 90 minutes intraoperatively; T7, during skin closure; T8, after extubation; and T9, at 0, 15, and 30 minutes and 2, 4, 6, 12, and 24 hours postoperatively.

Throughout surgery, hemodynamic stability will be closely monitored, and the presence of intraoperative hypertension episodes, pharmacological interventions applied in case of more than 20% deviation from baseline values, estimated blood loss, administered fluid volume, urine output, medications and total doses, additional analgesic requirements, surgical duration, anesthesia duration, extubation status, and transfer to the intensive care unit or ward will be recorded.

Hypertension will be defined as systolic arterial pressure and heart rate ≥20% above baseline. In such cases, fentanyl 2 μg/kg IV will be administered and the propofol infusion rate will be increased to 150 μg/kg/min. If values remain elevated, nitroglycerin 0.01 mg/kg IV bolus will be administered. Hypotension will be defined as systolic arterial pressure ≤20% below baseline and will be treated with ephedrine 5-10 mg IV. Bradycardia will be defined as heart rate ≤20% below baseline or <40 beats/min and will be treated with atropine 0.5 mg IV.

Intraoperative analgesia will be provided by remifentanil infusion. Total perioperative opioid consumption (intraoperative and first 24 postoperative hours), expressed as fentanyl equivalents (μg) (1 μg remifentanil ≈ 100 μg fentanyl), will be recorded.

To evaluate the inflammatory response, complete blood count and biochemical analyses will be performed on routine blood samples obtained preoperatively and at postoperative 24 hours. Neutrophil, lymphocyte, monocyte, and platelet counts will be recorded, and neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII) (platelet × neutrophil / lymphocyte), and systemic inflammatory response index (SIRI) (neutrophil × monocyte / lymphocyte) will be calculated. C-reactive protein (CRP) levels will also be measured and analyzed to compare intergroup and temporal changes.

Approximately 30 minutes before the end of surgery, all patients will receive intravenous paracetamol 1 g and tramadol 1 mg/kg for postoperative pain management, and ondansetron 4 mg IV for nausea and vomiting prophylaxis. At the end of surgery, anesthetic agents will be discontinued, and patients demonstrating spontaneous respiratory effort will receive sugammadex 2 mg/kg IV for reversal of neuromuscular blockade. Patients with adequate spontaneous respiration, full consciousness, recovered muscle strength, hemodynamic stability, and BIS ≥85 will be extubated and transferred to the post-anesthesia care unit.

In the postoperative period, patients' hemodynamic data, SpO₂ levels, resting pain scores, presence of nausea, vomiting, shivering, and possible complications will be recorded at 0, 15, and 30 minutes in the recovery unit and at 2, 4, 6, 12, and 24 hours on the ward. Pain intensity will be assessed using the 10-point NRS (0 = no pain, 10 = worst pain imaginable), and nausea severity will be evaluated using a 5-point scale. Patients with an Aldrete score ≥9 will be transferred to the ward.

All postoperative analgesic doses, rescue analgesia requirements, and additional analgesics will be recorded. A standard multimodal analgesia protocol will be applied. Postoperative analgesic requirements will be evaluated based on patient-controlled analgesia (PCA) device use and rescue analgesic need. PCA with tramadol will be initiated in the recovery unit, with settings of a 10 mg bolus dose and a 20-minute lockout interval.

Patients with NRS ≥4 within the first 30 minutes postoperatively will receive intravenous dexketoprofen 50 mg as rescue analgesia, which will be repeated every 12 hours if clinically indicated. All patients will continue to receive intravenous paracetamol 1 g every 6 hours during ward follow-up. In patients with resting NRS ≥4, the PCA lockout interval will be reduced to 15 minutes.

If the postoperative nausea-vomiting score is ≥2, ondansetron 4 mg IV will be administered initially, followed by dexamethasone 4 mg IV if symptoms persist.

Data obtained from the patients will be analyzed statistically after classification into predefined subgroups.

Inclusion Criteria:

• Aged 18 years and older
• Scheduled for elective intracranial surgery with skull pin head holder fixation
• Classified as American Society of Anesthesiologists (ASA) physical status I-III
• Provided written informed consent in the preoperative period

Exclusion Criteria:

• Allergy to local anesthetics
• Coagulopathy or anticoagulant use
• Local infection at injection site
• Pregnancy or breastfeeding
• Chronic opioid use (>3 months) or chronic pain syndrome
• Severe psychiatric disorders affecting pain assessment
• Emergency surgery
• Active infection or rheumatic disease
• Hematological disease or malignancy (active or within 5 years)
• Recent use of biological agents, chemotherapy, or corticosteroids (within 30 days)
• NSAID use within 24 hours before surgery
• Advanced organ failure (NYHA III-IV, Child-Pugh C, eGFR <30 mL/min)
• Refusal to participate
• Communication difficulties preventing pain assessment

Patients aged 18 years and older who are scheduled for elective intracranial surgery under general anesthesia with planned skull pin head holder (Mayfield-type) fixation, classified as American Society of Anesthesiologists (ASA) physical status I-III, and who have provided informed consent will be included.