A craniotomy involves opening the skull surgically to gain access to intracranial structures. This procedure is performed to remove a tumor, relieve elevated ICP, evacuate a blood clot, and control hemorrhage. The surgeon cuts the skull to create a bony flap, which can be repositioned after surgery and held in place by periosteal or wire sutures. One of two approaches through the skull is used: (1) above the tentorium (supratentorial craniotomy) into the supra-tentorial compartment, or (2) below the tentorium into the in-fratentorial (posterior fossa) compartment. A transsphenoidal approach through the mouth and nasal sinuses is used to gain access to the pituitary gland. Table 61-3 compares the three dif-ferent surgical approaches: supratentorial, infratentorial, and trans-sphenoidal.
Alternatively, intracranial structures may be approached through burr holes (Fig. 61-7), which are circular openings made in the skull by either a hand drill or an automatic craniotome (which has a self-controlled system to stop the drill when the bone is penetrated). Burr holes are made for exploration or diagnosis. They may be used to determine the presence of cerebral swelling and injury and the size and position of the ventricles. They are also a means of evacuating an intracranial hematoma or abscess and for making a bone flap in the skull and allowing access to the ventricles for decompression, ventriculography, or shunting pro-cedures. Other cranial procedures include craniectomy (excision of a portion of the skull) and cranioplasty (repair of a cranial de-fect using a plastic or metal plate).
Preoperative diagnostic procedures may include CT scanning to demonstrate the lesion and show the degree of surrounding brain edema, the ventricular size, and the displacement. MRI provides information similar to that of the CT scan and examines the le-sion in other planes (Tornqvist, 2001). Cerebral angiography may be used to study the tumor’s blood supply or give informa-tion about vascular lesions. Transcranial Doppler flow studies are used to evaluate the blood flow of intracranial blood vessels.
Most patients are placed on an antiseizure medication such as phenytoin (Dilantin) or a phenytoin metabolite (Cerebyx) before surgery to reduce the risk of postoperative seizures (paroxysmal transient disturbances of the brain resulting from a discharge of abnormal electrical activity) (Hickey, 2003; Karch, 2002).
Before surgery, corticosteroids such as dexamethasone (Decadron) may be administered to reduce cerebral edema. Fluids may be re-stricted. A hyperosmotic agent (mannitol) and a diuretic agent such as furosemide (Lasix) may be given intravenously immedi-ately before and sometimes during surgery if the patient tends to retain fluid, as do many who have intracranial dysfunction. The patient may be given antibiotics if there is a chance of cerebral contamination; diazepam may be prescribed before surgery to allay anxiety.
The preoperative assessment serves as a baseline against which postoperative status and recovery are compared. This assessment includes evaluating LOC and responsiveness to stimuli and iden-tifying any neurologic deficits, such as paralysis, visual dysfunc-tion, alterations in personality or speech, and bladder and bowel disorders. Distal and proximal motor strength in both upper and lower extremities is recorded using the 5-point scale.
The patient’s and family’s understanding of and reactions to the anticipated surgical procedure and its possible sequelae are as-sessed, as is the availability of support systems for the patient and family. Adequate preparation for surgery, with attention to the patient’s physical and emotional status, can reduce the risk for anxiety, fear, and postoperative complications. The patient is as-sessed for neurologic deficits and their potential impact after surgery. If there are motor deficits or weakness or paralysis of the arms or legs, trochanter rolls are applied to the extremities and the feet are positioned against a footboard. A patient who can am-bulate is encouraged to do so. If the patient is aphasic, writing materials or picture and word cards showing the bedpan, glass of water, blanket, and other frequently used items may help improve communication.
Preparation of the patient and family includes providing in-formation about what to expect during and after surgery. The surgical site is shaved immediately before surgery (usually in the operating room) so that any resultant superficial abrasions do not have time to become infected. An indwelling urinary catheter is inserted in the operating room to drain the bladder during the administration of diuretics and to permit urinary output to be monitored. The patient may have a central and arterial line placed for fluid administration and monitoring of pressures after surgery. The large head dressing applied after surgery may impair hearing temporarily. Vision may be limited if the eyes are swollen shut. If a tracheostomy or endotracheal tube is in place, the patient will be unable to speak until the tube is removed, so an alterna-tive method of communication should be established.
An altered cognitive state may make the patient unaware of the impending surgery. Even so, encouragement and attention to the patient’s needs are necessary. Whatever the state of awareness of the patient, the family needs reassurance and support because they recognize the seriousness of brain surgery.
Postoperatively, an arterial line and a central venous pressure line may be in place to monitor and manage blood pressure and cen-tral venous pressure. The patient may be intubated and may re-ceive supplemental oxygen therapy. Ongoing postoperative management is aimed at detecting and reducing cerebral edema, relieving pain and preventing seizures, and monitoring ICP.
Medications to reduce cerebral edema include mannitol, which increases serum osmolality and draws free water from areas of the brain (with an intact blood–brain barrier). The fluid is then ex-creted by osmotic diuresis. Dexamethasone (Decadron) may be administered intravenously every 6 hours for 24 to 72 hours; the route is switched to oral as soon as possible and dosage is tapered over 5 to 7 days (Karch, 2002).
Acetaminophen is usually prescribed for temperature exceeding 99.6°F (37.5°C) and for pain. Commonly, the patient has a headache after a craniotomy, usually as a result of the scalp nerves being stretched and irritated during surgery. Codeine, given par-enterally, is often sufficient to relieve headache. Morphine sulfate may also be used in the management of postoperative pain in the craniotomy patient (Leith, 1998).
Antiseizure medication (phenytoin, diazepam) is prescribed for patients who have undergone supratentorial craniotomy be-cause of the high risk of seizures after supratentorial neurosurgical procedures. Serum levels are monitored to keep the medications within the therapeutic range.
A ventricular catheter or other type of drain frequently is inserted in patients undergoing intracranial surgery. The catheter is con-nected to an external drainage system. The patency of the catheter is noted by the pulsations of the fluid in the tubing. The ICP can be assessed using a stopcock attached to the pressure tubing and transducer. The ICP is measured by turning the three-way stop-cock to the appropriate position (Hickey, 2003). Care is required to ensure that the system is tight at all connections and that the stopcock is in the proper position to avoid drainage of CSF; col-lapse of the ventricles and brain herniation may result if fluid is removed too rapidly (Hickey, 2003). The catheter is removed when the ventricular pressure is normal and stable. The neuro-surgeon must be notified if the catheter appears to be obstructed.