ANESTHESIA STRATEGIES FOR SUPRATENTORIAL TUMORS

Overview

Introduction

Impact of Supratentorial Tumors on Intracranial Physiology

Clinical Signs and Symptoms of Supratentorial Tumors

• Presentation variability based on location, size, and effects.
• Low-Grade Tumors: Focal signs (hemiparesis, aphasia, etc.).
• Generalized Signs: Headache, nausea, vomiting, cognitive decline.
• Raised ICP: Headache, nausea, vomiting, cognitive changes.
• Herniation Symptoms: Subfalcine, Uncal, Tonsillar herniation.
• Insidious Onset vs. Acute Presentation: Slow-growing vs. bleeding tumors.

Impact of Supratentorial Tumors on Cerebral Blood Flow (CBF) Determinants

Preoperative Assessment for Patients with Supratentorial Tumors

Preoperative Preparation of the Patient with Supratentorial Tumor

Please note that these tables and diagrams are simplified representations, and in actual medical practice, detailed medical records and images would be used for comprehensive patient care.

Preoperative Assessment for Supratentorial Brain Tumors

Imaging Studies: CT and MRI scans are essential for surgical planning.

Preoperative Preparation for Supratentorial Brain Tumors

Preoperative Preparation of the Patient with Supratentorial Tumor:

• Multidisciplinary Discussion:
  • Collaborate with the surgical team, intensivist, nursing, and recovery staff for preoperative planning and postoperative recovery.
  • Clarify essential details with the surgeon, such as tumor size, location, diagnosis, surgical approach, need for ICP reduction, neuromonitoring, expected complications, and surgical goals.
  • Different surgical approaches may have specific considerations, such as the risk of bleeding and venous air embolism.
• Premedication:
  • Evaluate the need for anxiolytics cautiously, considering the potential risk of CO2 retention in patients with compromised intracranial compliance.
  • Anxiolytics may be avoided or used sparingly based on individual patient assessment.
  • For patients with tumors and evidence of midline shift, premedication with anxiolytics may be best avoided.
  • Consider a professional, reassuring visit by the anesthesiologist as a form of preoperative anxiolysis.
• Antiepileptics:
  • Continue antiepileptic drugs throughout the perioperative period unless seizure focus mapping is planned.
  • Monitor for potential drug interactions and increased metabolism of other medications.
• Steroids:
  • Initiate preoperative steroids for patients with significant tumor-related mass effect or tumor-related edema.
  • A common regimen is an initial bolus dose of 10 mg of dexamethasone, followed by 4 mg every 6 hours, which is continued perioperatively.
• Other Medications:
  • Review and continue all home medications unless contraindicated.
  • Consider the sedative effects of anticonvulsants during preoperative evaluation and premedication.
  • Evaluate the potential for changes in serum osmolality and electrolytes due to medications or tumor-related conditions.
  • Histamine (H2) blockers and gastric prokinetic agents may be necessary to counteract gastric issues associated with increased ICP and steroid therapy.
  • Discontinue blood thinners appropriately.
• Routine Preoperative Investigations:
  • Include standard monitoring of oxygenation, ventilation, circulation, and temperature.
  • Frequent blood gas and electrolyte measurements.
  • Regular monitoring of blood glucose levels.
  • Central venous pressure monitoring may be considered in select cases with specific risk factors.
  • Placement of a urinary catheter for urine output monitoring.
• Intracranial Pressure Monitoring:
  • Extraventricular drain (EVD) placement for CSF drainage and ICP monitoring, if indicated.
• Processed EEG Monitoring:
  • Use processed EEG monitors (e.g., BIS or SedLine) to guide anesthetic depth and facilitate rapid emergence from anesthesia.
• Central Jugular Venous Bulb Oxygen Saturation and Transcranial Doppler Ultrasonography (TCD):
  • Consider central jugular venous bulb oxygen and TCD for select high-risk patient populations to assess cerebral perfusion and autoregulation.
• Point-of-Care (POC) Viscoelastic Assays:
  • Employ POC viscoelastic assays (e.g., ROTEM® or TEG®) as needed to assess coagulation status, especially in patients with brain tumors who may have hemostatic abnormalities.
• Vascular Access:
  • Ensure two large-bore peripheral IV lines for vascular access.
  • Central venous access should be considered in specific situations such as significant VAE risk, substantial bleeding risk, or significant cardiorespiratory disease.

Preoperative preparation for patients with supratentorial tumors requires careful consideration of the patient’s individual factors and the surgical approach. Collaboration with the surgical team and comprehensive monitoring are essential to ensure safe and successful surgery.

Intraoperative Management of Supratentorial Tumor Resection:

• Neuromonitoring:
  • Adapt anesthetic agents based on the type of neuromonitoring in use.
  • Volatile anesthetic agents can impact evoked potentials, while IV agents like propofol, dexmedetomidine, or remifentanil interfere less with electrophysiological monitoring.
• Management of Tense Brain:
  • Ensure adequate brain relaxation to minimize the need for brain retraction.
  • Provide a slack surgical brain to facilitate surgical exposure.
  • Avoid excessive retraction, which can lead to perilesional neuronal injury.
• Patient Positioning:
  • Position the patient carefully with proper padding of pressure points.
  • Maintain slight head-up positioning to optimize cerebral venous drainage.
  • Avoid excessive neck flexion, extension, or rotation.
  • Ensure secure fixation of endotracheal tube and lines to prevent accidental dislodgement.
• Pre-incision Preparation:
  • Administer antibiotics before dural opening.
  • Monitor blood pressure to support cerebral perfusion pressure (CPP).
• Maintenance of Anesthesia:
  • Maintain an adequate depth of anesthesia to reduce pain responses and prevent hemodynamic changes during surgery.
  • Use short-acting, titratable agents for better control.
  • Consider the patient’s specific condition when selecting anesthetic agents (e.g., dexmedetomidine, remifentanil, or volatile anesthetics).
• Ventilation Strategy:
  • Aim for normocapnia or mild hypocapnia (PaCO2 of 30-35 mmHg).
  • Be cautious with hyperventilation to balance brain relaxation against the risk of cerebral hypoperfusion.
  • Consider baseline PaCO2 levels and end-tidal CO2 to PaCO2 gradient in patients with COPD.
  • Avoid high levels of positive end-expiratory pressure (PEEP) if possible.
• Fluid and Hemodynamic Management:
  • Maintain normovolemia and normotension.
  • Continuously monitor serum sodium levels, plasma osmolarity, urine output, and vascular volume status.
  • Use isotonic crystalloids and/or colloids for maintenance, avoiding glucose-containing or hypo-osmolar solutions.
  • Be cautious with large volumes of normal saline (NS) to prevent hyperchloremic metabolic acidosis.
  • Individualize blood transfusion based on expected blood loss, patient status, and clinical endpoints.
  • Optimize blood pressure with intravascular volume expansion and vasopressors as needed.
  • Choose vasopressors based on patient’s cardiac function and comorbidities, considering agents like phenylephrine, norepinephrine, dopamine, dobutamine, or vasopressin as appropriate.
• Osmotic Agents:
  • Use hyperosmolar solutions like mannitol or hypertonic saline (HS) to reduce brain volume and facilitate surgical exposure.
  • Administer these agents before opening the dura for optimal brain relaxation.
  • Monitor osmolality and electrolyte levels to prevent adverse effects.

Intraoperative management of supratentorial tumor resection requires careful attention to neuromonitoring, brain relaxation, patient positioning, ventilation, fluid balance, and hemodynamics to ensure optimal surgical conditions and patient safety. Adaptation of anesthetic agents and close monitoring are essential throughout the procedure.

Postoperative Period Management for Craniotomy Patients:

1. Pain Management:
   • Utilize multimodal analgesia to control pain effectively.
   • Combine drugs like opioids, non-opioid analgesics, local anesthetics, and adjuvants for synergistic pain relief.
   • Consider scalp blocks or wound infiltration with local anesthetics.
   • Patient-controlled analgesia (PCA) with opioids may be used with vigilant monitoring for respiratory depression.
   • Avoid nonsteroidal anti-inflammatory drugs (NSAIDs) due to potential bleeding risks.
2. Post-Craniotomy Nausea and Vomiting (PONV) Management:
   • Intracranial procedures carry a high risk of PONV.
   • Prophylactic antiemetics such as 5-HT3 antagonists (e.g., ondansetron, granisetron) are recommended.
   • Combining antiemetics with dexamethasone enhances their efficacy.
   • Risk stratification using a PONV scoring system helps determine the need for additional antiemetic strategies.
3. Neurological Assessment:
   • Regularly assess the patient’s neurological status.
   • Ensure that the patient awakens promptly and can follow simple commands.
   • Early awakening facilitates neurological examination, allowing timely detection of postoperative complications.
4. Hypertension Management:
   • Hypertension during emergence from anesthesia is common and must be promptly treated.
   • Administer short-acting antihypertensive agents as needed to control blood pressure.
   • Avoid rapid normalization of PaCO2 levels, especially after hyperventilation, to prevent an increase in cerebral blood flow and intracranial pressure.
5. Delayed Emergence Evaluation:
   • If the patient does not awaken within 20-30 minutes after anesthesia cessation, consider non-anesthetic causes.
   • Maintain airway, breathing, and circulation support.
   • Perform neurological examinations and monitor vital signs.
   • Conduct blood gas analysis, assess electrolytes, glucose levels, and consider imaging studies to rule out common causes of delayed emergence.
6. Recovery Location:
   • Due to the risk of cerebral hemorrhage, patients are initially recovered in an intensive care unit (ICU).
   • In cases of limited ICU resources, consider direct admission to the ward with adequate staffing, monitoring, and the presence of a rapid response team after consulting with the surgeon.
7. Intracranial Pressure (ICP) Management:
   • Regularly monitor ICP and maintain it within acceptable limits.
   • Optimize cerebral perfusion pressure (CPP) by managing blood pressure and ICP.
   • Hypertonic solutions like mannitol or hypertonic saline may be used to reduce brain swelling.
   • Monitor electrolyte balance when administering hypertonic solutions.
8. Fluid and Hemodynamic Management:
   • Maintain normovolemia and normotension.
   • Monitor serum sodium levels, plasma osmolarity, urine output, and vascular volume status.
   • Tailor fluid management to the patient’s specific needs, considering factors such as blood loss, surgical duration, and clinical endpoints.
9. Ventilation and Carbon Dioxide Levels:
   • Aim for normocapnia or mild hypocapnia (PaCO2 30-35 mmHg) while ventilating the patient.
   • Use caution with high positive-end expiratory pressure (PEEP) levels.
   • Gradually restore normal PaCO2 levels to avoid sudden increases in cerebral blood flow and intracranial pressure.
10. Postoperative Monitoring:
    • Continuously monitor the patient’s vital signs, neurological status, and responses to treatment.
    • Ensure close observation for any signs of complications such as hemorrhage, infection, or neurological deterioration.
11. Nutrition and Hydration:
    • Initiate enteral or parenteral nutrition as appropriate to meet the patient’s nutritional needs.
    • Maintain proper hydration status to support recovery.
12. Wound Care and Infection Prevention:
    • Maintain strict aseptic techniques to prevent surgical site infections.
    • Monitor the surgical incision site for signs of infection or wound complications.
13. Seizure Prophylaxis:
    • Consider prophylactic antiepileptic medications in patients at high risk of postoperative seizures.
    • Monitor for any seizure activity and adjust medication accordingly.
14. Neurological Assessment and Imaging:
    • Perform regular neurological assessments to detect any changes in the patient’s condition.
    • Consider follow-up imaging studies (CT or MRI) as needed to evaluate postoperative changes or complications.
15. Psychological Support:
    • Provide psychological support and education to the patient and their family regarding the surgical procedure and recovery process.
    • Address any concerns or anxiety related to the surgery and postoperative care.
16. Discharge Planning:
    • Develop a discharge plan based on the patient’s progress and specific needs.
    • Ensure proper communication and coordination with the patient’s healthcare team for a smooth transition to outpatient care if necessary.
17. Pain and Symptom Management at Home:
    • Provide instructions and medications for pain management and symptom control during the post-discharge period.
    • Educate the patient and caregivers on recognizing and reporting any signs of complications.
18. Follow-up Care:
    • Schedule follow-up appointments to monitor the patient’s progress and address any ongoing issues or concerns.
    • Continue neurological assessments and imaging studies as needed to assess long-term outcomes.

Remember that postoperative management for craniotomy patients requires close monitoring, individualized care, and a multidisciplinary approach involving neurosurgeons, anesthesiologists, nurses, and other healthcare professionals to ensure the best possible recovery and outcomes.