Head pinning is used in the majority of craniotomies. It is the first major event following induction, and it’s often more stimulating than laryngoscopy and intubation. Be prepared! Typically, a bolus of propofol and fentanyl will do the trick. If avoiding hypertension is especially critical, such as in a patient with a cerebral aneurysm, esmolol may also be necessary. Pinning can sneak up on you, so discuss the plan with your attending in advance and watch the surgical team closely.

Once the skull is opened, surgical stimulation drops significantly. This is your chance to find a stable anesthetic equilibrium or the “sweet spot.” This is often a mix of propofol, remifentanil (or any other opiate), and phenylephrine. Propofol, remifentanil, and phenylephrine are a fantastic three-drug combination that can be suited to nearly every single neuroanesthetic.

Neuroanesthesia is a field where you will begin to further appreciate the nuances between IV agents and volatile anesthetics (Table 36.1) in terms of their ability to maintain surgical conditions. IV agents don’t have a “MAC” equivalent. For paralyzed patients, use BIS monitoring and common sense. Propofol infusion titration is complex due to context-sensitive half-time. Context-sensitive half-time is an important pharmacologic concept in anesthesia, especially with highly lipid-soluble agents such as propofol, fentanyl, and dexmedetomidine. As an infusion continues, these drugs distribute into peripheral compartments like muscle and fat, altering how quickly plasma concentrations fall once the infusion stops. For propofol specifically, the context-sensitive half-time remains relatively short compared with many other agents, but it still lengthens modestly with longer infusions because more drug accumulates in peripheral tissues.

Modality	Volatile limit	Paralysis allowed?	Notes
Somatosensory evoked potential only	≤0.5 MAC	Yes	Volatile agents reduce amplitude; paralysis is okay
electromyography only	No limit	No	Very flexible otherwise
SSEP + EMG	≤0.5 MAC	No	Requires both conditions
MEP (± SSEP)	≤0.3 MAC	No	Most restrictive; common in complex spine cases

To understand context-sensitive half-time, explore simulation tools like SimTiva^© or read about target-controlled infusion (TCI) pump technology. This will help you understand plasma vs. effect-site kinetics. Anyone can give propofol, but to elevate your role as an anesthetic specialist, a deeper level of understanding is necessary.

Neuroanesthesia requires meticulous setups. As with ENT, your access to the patient’s head and arms will be strictly limited. Your IV setup must be flawless; keep infusions close to the IV site to minimize dead space, ensure all tubing is secure and appropriately extended, make drips clearly visible and accessible, and extend the ventilator circuit to facilitate safe airway management.

Target “neuroprotective” physiology by maintaining robust MAP along with normal CO₂, oxygenation, sodium, glucose, temperature, and volume status. Avoid significant hypocarbia (unless the patient is acutely herniating), because low CO₂ can cause cerebral vasoconstriction and ischemia. If the surgeon requests tighter CO₂ control, follow the request but monitor ABGs closely to prevent overcorrection. Remember that there is usually a 2–5 mmHG gradient between PaCO₂ and ETCO₂.

Many neurosurgical patients and patients in the neurologic ICU are given sodium “goals.” These goals are mainly to avoid extremes of hyponatremia, which can exacerbate cerebral edema. While hyponatremia should be avoided, sodium-altering agents should be used with extreme caution. Correcting sodium levels quickly, since this can lead to central pontine myelinolysis. The majority of hospitalized patients with hyponatremia have SIADH, and administering fluids, hypertonic or otherwise, will not be highly effective (if you give a liter of normal saline to a patient with SIADH, they will simply retain the water and excrete the salt).

In neurosurgical cases, it is especially critical to maintain normothermia and normoglycemia.

Neurosurgical wakeups are challenging. The cases are long, airway access may remain limited until the very end of the case, and neurologic status may be altered by surgery or underlying intracranial pathology. TIVA techniques are associated with somewhat “smoother” wakeups, but are sometimes prolonged by the effects of context-sensitive halftime.

One technique to facilitate a more rapid wear-off of IV agents is to transition to inhalational agents (once neuromonitoring is complete), although the wakeup time saved is probably negligible. This almost always will result in a drop in MAP, since the vasodilatory effects of dual anesthetic agents (gas plus residual TIVA) will potentiate.

Wakeup time is largely influenced by non-modifiable factors: length of surgery, patient comorbidities, age, and presence or absence of critical illness. I recommend to focus on safe emergence and not to aim for speed.

Remifentanil will enable rapid wake-up but cause rebound pain if used as a sole opiate. Small fentanyl doses (e.g., 25 mcg at a time) can ease the transition. Use opioids in small titrations at the end of neurosurgical cases, as excessive dosing can obscure the neurologic examination.

Sudden movement or coughing while still pinned can result in soft tissue injury, skull fracture, or cervical spine damage. An easy safeguard against movement in skull pins is to keep the patient fully asleep until the pins are removed. If you are in a position where the patient begins to move in pins, immediately bolus propofol and fentanyl bolus, and switch to manual ventilation. This will temporarily relieve the patient from bucking against a ventilator-administered breath. Once the patient has stopped moving, you can resume ventilation.

Patients with elevated ICP will increase their MAP with compensatory mechanisms to protect CPP. Once the dura is opened and pressure is relieved, expect a sudden MAP drop. Be ready to treat with fluids or vasopressors.

Think of aneurysm surgery as vascular surgery for the brain. These are cases with critical considerations for BP control, heparinization, and are at high risk for bleeding. Rupture risk is highest during dural opening and vessel exposure. For high-risk aneurysms, consider having blood in the room. Large-bore access is essential. Discuss each phase of the case with your attending and understand what’s at stake during exposure, clipping, and closure. These cases require paying close attention to the surgical field.

Awake craniotomy is indicated for the resection of tumors near language, motor, or sensory areas. This requires phases of moderate sedation with local anesthesia (for exposure and skull pinning) and phases of wakefulness to participate in neurologic exams. These require continuous communication with the surgeon and patient, and respect for maintaining spontaneous ventilation. Epilepsy surgery with seizure mapping may additionally require a tailored approach that involves awake and asleep portions. You’ll find extensive literature on epilepsy surgery protocols and awake craniotomy management in various open anesthesia sources. I personally recommend a helpful collection of articles on UCSF’s neuroanesthesia page: https://anesthesia.ucsf.edu/divisions/neuroanesthesia#techniques