Anesthesia for Posterior Fossa Surgery
For posterior fossa surgery, a balanced anesthetic approach using short-acting agents with multimodal analgesia is recommended to allow for rapid emergence and neurological assessment while maintaining hemodynamic stability.
Preoperative Considerations
- Thorough assessment for comorbidities including hypertension, diabetes, and anemia should be performed to optimize the patient's condition before surgery 1
- Avoid routine premedication, especially long-acting benzodiazepines, as they can impair postoperative mobilization and neurological assessment 1
- Short-acting benzodiazepines may be used in younger patients before potentially painful interventions like epidural placement 1
- Consider clonidine (5 μg/kg) as an alternative to midazolam for premedication, as it has been shown to reduce remifentanil requirements and provide better hemodynamic stability 2
- Clear fluids may be consumed up to 2 hours and light meals up to 6 hours before anesthesia induction 1
Intraoperative Management
Anesthetic Technique
- Either general anesthesia or spinal anesthesia can be used, but simultaneous administration should be avoided due to risk of precipitous blood pressure drops 1
- For general anesthesia, use a standard protocol with short-acting agents to allow rapid awakening 1:
- Induction: Propofol with reduced doses in elderly patients
- Maintenance: Inhalational agent (avoiding nitrous oxide) or total intravenous anesthesia (TIVA)
- Opioid: Short-acting agents like remifentanil (0.05-2 μg/kg/min) for stress response attenuation 3
- Muscle relaxation: Ensure complete reversal of neuromuscular blockade at the end of surgery 1
Monitoring
- Standard ASA monitoring plus:
Positioning
- The prone or lateral decubitus positions are more commonly used than sitting position for posterior fossa surgery 4
- When sitting position is used, careful monitoring for venous air embolism is essential 4
Ventilation
- Implement lung-protective ventilation with low tidal volumes to limit peak airway pressure 1
- Maintain normocapnia to avoid cerebral vasodilation or vasoconstriction 1
Pain Management
Multimodal opioid-sparing analgesia is recommended 1:
- Consider thoracic epidural analgesia with local anesthetics and low-dose opioids for open procedures 1
- Intravenous lidocaine can be administered (1.5 mg/kg at induction followed by 2 mg/kg/h during surgery) if epidural is contraindicated 1
- Peripheral nerve blocks should be considered as adjuncts to extend the period of postoperative non-opioid analgesia 1
- Postoperatively, use a combination of paracetamol and NSAIDs given orally with opioids as rescue medication 1
Patient-controlled analgesia (PCA) has been shown to provide better pain control after posterior fossa surgery compared to nurse-administered PRN analgesia, with no difference in side effects 5
Special Considerations
- Maintain normothermia (≥36°C) using active warming devices 1
- Implement PONV prophylaxis as posterior fossa surgery carries a high risk of postoperative vomiting (47% in some centers) 4
- Avoid fluid overload as it can contribute to cerebral edema 1
- For pregnant patients requiring posterior fossa surgery, a combined approach may be necessary with modifications to the anesthetic plan 6, 7
Postoperative Care
Early mobilization (within 24 hours) is recommended to reduce complications 1
Monitor for potential complications:
Consider early removal of urinary catheter (within 24 hours) unless there is high risk of retention 1
Common Pitfalls
- Avoid nitrous oxide as it is used in less than 10% of centers for posterior fossa surgery due to risk of venous air embolism 4
- When neurophysiological monitoring is used during surgery, 15% of centers avoid neuromuscular blockade to prevent interference 4
- Opioid administration should be carefully titrated to avoid respiratory depression while still providing adequate analgesia 5