In this video, we will highlight the goals and some of the challenges facing the team during the first phase of the awake brain surgery. Our team prefers to have the patient unconscious during this phase, because we believe that it enables the patient to remain more awake and more cooperative for longer during the crucial second phase. Having the patient unconscious during the surgery necessitates general anaesthesia, but this brings with it several dangers and challenges. The goal of anaesthesia during this phase is to keep the patient unconscious and comfortable, but using drugs and techniques that enable a rapid, predictable, and safe return of consciousness at the end of it.
During the surgery, it is important that the patient does not make any movements in response to painful stimuli. It may surprise you to hear this, but even when patients are unconscious, their bodies can respond in a reflex way to painful stimuli, by generating movements in the direction of the stimulus. During this phase of the operation, the patient will be subjected to several very unpleasant stimuli– insertion of a device into the airway, infiltration of local anaesthetic to numb the scalp and skull, and most unpleasant of all, the application of the Mayfield headholder, which involves pressing very sharp pins through the scalp into the middle layer of the skull to hold the head absolutely still.
To prevent responses to these unpleasant stimuli, we use infusions of a hypnotic drug to cause a loss of consciousness, and an infusion of an analgesic, a painkiller. Even among patients who seem to be similar, there’s very wide variability in the doses of these drugs that are needed to achieve the effects we want. One dose might be too high for one patient, and inadequate for another. However, we can’t solve this by simply administering very large doses to all patients, as most drugs have several dose-related adverse effects. At anaesthetic doses, both drugs cause loss of protective reflexes, and loss of respiratory drive. Especially in older or sicker patients, both can decrease the heart rates and blood pressure.
The anaesthetist must thus protect the airway with an airway device to keep it open. in this case, a laryngeal mask was used– and mechanically ventilate the lungs with oxygen and air. Strict control of the blood pressure and carbon dioxide and oxygen levels is required, as deviations from normal can cause the brain to swell, which is dangerous in patients with brain tumours. Likewise, any coughing or patient movement must be prevented at all costs. Coughing can also cause dangerous increases in the pressure inside the skull, whereas patient movements can obviously interfere with the surgery. And when the surgeon is busy with very fine work, the tiniest movement can have severe consequences.
After the patient has been made unconscious, airway controlled, and mechanical ventilation initiated, we infiltrate a local anaesthetic around the major nerves supplying the scalp and skull. This is a crucial step. If performed well, the patient should not have pain when he is awake in the later phases. After that the Mayfield headholder is applied, a procedure that would ordinarily be extremely painful. After that, then, the patient is placed into position on the operating table. This positioning is another crucial step, as a patient will lie in this position for several hours without being able to move. Careful placing of padding, and protection of nerves and pressure points is essential to prevent nerve injuries, and minimise later discomfort.
The patient on the operating table is then transferred to the operating theatre, the scalp is shaved, and marked, and disinfected, and finally the surgeon can begin the operation. He cuts through the scalp, controls bleeding, and then removes a section of the scalp, exposing the brain underneath. The team then turns their attention to the most dangerous part of this phase, which is to return the patient to consciousness. Tom. Tom. [DUTCH:] Are you awake?
The anesthesiologist stops the drug infusions, awaits return of consciousness, and must then very carefully choose the moment at which the mechanical ventilation will be stopped, and the airway device removed. [DUTCH:] Open your mouth. Yes. Yes. Open, open. Tongue out. Yes. Well done. That’s good
Tom, just leave your arm lying down.
Remember that the airway device is protecting the airway from soiling by content from the stomach, and secretions from the mouth. If the anesthesiologist removes the laryngeal mask or other airway device too late, the patient will be uncomfortable, and will be coughing and gagging on that device. And if things go really badly wrong, he will regurgitate, and will breathe in gastric content, meaning acids and bile salts, or maybe even bits of food. And this could later cause him to develop pneumonia.
If, however, the anesthesiologist removes the airway device too soon, the patient will not be breathing properly, may obstruct the airway, the tongue might fall into the airway, or the walls of other passages close, and this can cause life-threatening changes in oxygen and carbon dioxide levels. Once this awakening is safely accomplished, and the patient is fully awake, and breathing properly again, the next phase can start.