HEAD & NECK CANCER SURGERY

Surgery for cancer of the head and neck includes laryngectomy,

glossectomy, pharyngectomy, parotidectomy, hemimandibulectomy, and
radical neck dissection. An endoscopic examination following induction of
anesthesia often precedes these surgical procedures. Timing of a
tracheostomy, if planned, depends upon the patient’s preoperative airway
compromise. Some procedures may include extensive reconstructive
surgery, such as the transplantation of a free microvascular muscle flap,
with long surgical time duration.

Preoperative Considerations
The typical patient presenting for head and neck cancer surgery is
older and often has had many years of heavy tobacco and alcohol use.
Common coexisting medical conditions include chronic obstructive
pulmonary disease, coronary artery disease, hypertension, diabetes,
alcoholism, and malnutrition. These patients often greatly benefit from an
enhanced recovery after surgery program that includes preoperative
nutritional repletion over the course of days and hydration with a
carbohydrate–protein drink during the 24 h prior to surgery.
Airway management may be complicated by abnormal airway
anatomy, an obstructing lesion, or by preoperative radiation therapy that
has fibrosed, immobilized, and distorted the patient’s airway structures. If
there is concern regarding potential airway problems, intravenous
induction may be avoided in favor of awake direct or fiberoptic
laryngoscopy (cooperative patient) or direct or fiberoptic intubation
following an inhalational induction, maintaining spontaneous ventilation
(uncooperative patient). Elective tracheostomy under local anesthesia prior
to induction of general anesthesia is often a prudent option. In any case,
the appropriate equipment and qualified personnel required for emergent
tracheostomy must be immediately available.
Intraoperative Management
A.Monitoring
Because many of these procedures are lengthy and associated with
substantial blood loss, and because of the prevalence of coexisting
cardiopulmonary disease, arterial cannulation may be utilized for blood
pressure monitoring and frequent laboratory analyses. If central venous
access is deemed necessary, the surgeon should be consulted to ascertain
that planned internal jugular or subclavian venous access will not interfere
with the intended surgical procedures; antecubital or femoral veins are
reasonable alternatives. Arterial lines and intravenous cannulas should not
be placed in the operative arm if a radial forearm flap is planned. A
minimum of two large-bore intravenous lines and a urinary catheter
(preferably with temperature-monitoring capability) should be placed. A
forced-air warming blanket should be used to help maintain normal body
temperature. Intraoperative hypothermia and consequent vasoconstriction
can be detrimental to perfusion of a microvascular free flap.
Intraoperative nerve monitoring is increasingly utilized by surgeons
in anterior neck operations to help preserve the superior laryngeal,
recurrent
laryngeal, and vagus nerves (Figure 37–2), and the anesthesia provider
may be asked to place a specialized nerve integrity monitor endotracheal
tube
(Medtronic Xomed NIM endotracheal tube) to facilitate this process
(Figure 37–3).
FIGURE 37–2 The vagus nerve (cranial nerve X) originates in the
medulla
oblongata and then ramifies in the superior and inferior vagal ganglia in
the
neck. Its first major branch is the pharyngeal plexus of the vagus. The
superiorlaryngeal nerve divides into the external and internal laryngeal
nerves. The internal branch supplies sensory innervation of the laryngeal
mucosa above the vocal cords, and the external branch innervates the
inferior pharyngeal constrictor muscles and the cricothyroid muscle of the
larynx. Cricothyroid muscle contraction increases the voice pitch by
lengthening, tensing, and adducting the vocal folds. The superior laryngeal
nerve is at risk of damage during operations of the anterior neck,
especially thyroid surgery, and injury to this nerve may result in
hoarseness and loss of vocal volume. The next branch of the vagus is the
recurrent laryngeal nerve, which innervates all of the muscles of the
larynx except the cricothyroid, and is responsible for phonation and glottic
opening. The recurrent laryngeal nerve runs immediately behind the
thyroid
gland and thus is the nerve of greatest risk for injury during thyroid
surgery.
Unilateral recurrent laryngeal nerve damage may result in vocal changes
or hoarseness, and bilateral nerve damage may result in aphonia and
respiratory distress. Inferior to this nerve, the vagus nerve provides
autonomic motor and sensory nerve fibers to the thoracic and abdominal
viscera.

FIGURE 37–3 A: The Medtronic Xomed NIM electromyographic (EMG)

nerve integrity monitoring endotracheal tube. Succinylcholine (or no
relaxant at all) should be used for intubation, and the endotracheal tube
should be secured in the midline. If lubricant is used, it must not contain
local anesthetics. B: A slightly larger endotracheal tube size should be used
to facilitate mucosal contact with the electrodes, and the blue band of the
NIM tube must be positioned at the level of the vocal cords. C: Nerve
integrity is continuously monitored via EMG activity (Medtronic Xomed
NIM-Response 3.0 Nerve Integrity Monitor). Nondepolarizing muscle
relaxants are contraindicated because they prevent EMG monitoring.

B.Tracheostomy
Head and neck cancer surgery often includes tracheostomy. Immediately
prior to surgical entry into the trachea, the endotracheal tube and
hypopharynx should be thoroughly suctioned to limit the risk of aspiration
of blood and secretions. If electrocautery is used during the surgical
dissection, the FiO2 should be lowered to 30% or less, if possible, in order
to minimize the risk of fire as the trachea is surgically entered. In any case,
the easiest way to minimize airway fire risk in this circumstance is for the
surgeon not to use the cautery to enter the trachea. After dissection down
to the trachea, the tracheal tube cuff is deflated to avoid perforation by the
scalpel. When the tracheal wall is transected, the endotracheal tube is
withdrawn so that its tip is immediately cephalad to the incision.
Ventilation during this period is difficult because of the large leak through
the
tracheal incision. A sterile, cuffed tracheostomy tube is placed in the
trachea, the cuff is inflated, and the tube is connected to a sterile breathing
circuit. As soon as correct position is confirmed by capnography and
bilateral chest auscultation, the original endotracheal tube is removed. An
increase in peak inspiratory pressure immediately after tracheostomy
usually indicates a malpositioned endotracheal tube, bronchospasm, debris
or secretions in the trachea, or, rarely, pneumothorax.

C.Maintenance of Anesthesia
The surgeon may request the omission of NMBs during neck
dissection, thyroidectomy, or parotidectomy to allow nerve identification
(eg, spinal accessory, facial nerves) by direct nerve stimulation and
thereby facilitate their preservation. If a nerve integrity monitor
endotracheal tube is utilized, succinylcholine (or propofol with no
relaxant) may be used to facilitate intubation. Moderate controlled
hypotension may be helpful in limiting blood loss; however, cerebral
perfusion may be compromised with moderate hypotension when a tumor
invades the carotid artery or jugular vein (the latter may increase cerebral
venous pressure). If head-up tilt is utilized, it is important that the arterial
blood pressure transducer be zeroed at the level of the brain (external
auditory meatus) in order to most accurately determine cerebral perfusion
pressure. In addition, head-up tilt increases the risk of venous air
embolism.
Following reanastomosis of a microvascular free flap, blood pressure
should be maintained at the patient’s baseline level. The use of
vasoconstrictive agents (eg, phenylephrine) should be minimized because
of potential decrease in flap perfusion due to vasoconstriction. Similarly,
the use of vasodilators (eg, sodium nitroprusside or hydralazine) should be
avoided in order to minimize any decrease in graft perfusion pressure.
Transfusion
Transfusion decisions must balance the patient’s immediate surgical
risks with the possibility of an increased cancer recurrence rate resulting
from transfusioninduced immune suppression. Rheological factors make a
relatively low hematocrit (eg, 27–30%) desirable when microvascular free
flaps are performed. Excessive diuresis should be avoided during
microvascular free-flap surgery in order to optimize graft perfusion in the
postoperative period.

Cardiovascular Instability
Manipulation of the carotid sinus and stellate ganglion during radical
neck dissection has been associated with wide swings in blood pressure,
bradycardia, arrhythmias, sinus arrest, and prolonged QT intervals.
Infiltration of the carotid sheath with local anesthetic will usually
moderate these problems. Bilateral neck dissection may result in
postoperative hypertension and loss of hypoxic drive due to denervation of
the carotid sinuses and carotid bodies.

Postoperative Management
The principal postoperative complications associated with head and
neck cancer surgery include hypocalcemia secondary to acute
hypoparathyroidism, and threats to airway integrity secondary to
hemorrhage, hematoma formation, and bilateral vocal cord palsy with
stridor resulting from bilateral recurrent laryngeal nerve injury.
Postoperative hypoparathyroidism is a common condition, resulting from
injury to the parathyroid glands or their blood supply during
thyroidectomy or neck dissection, or from unintentional or intentional
removal of all four parathyroid glands. It may be either symptomatic or
asymptomatic, and occurs transiently in up to 49% of thyroidectomy
patients, and is permanent in up to 33% of thyroidectomy patients.
Symptoms and signs depend upon the rate of onset and severity of
hypocalcemia. Clinical signs of
acute, severe hypocalcemia include laryngospasm, bronchospasm, QT
prolongation-related arrhythmias, and congestive heart failure.
Neurological symptoms and signs range from circumoral paresthesias,
distal extremity numbness, and carpopedal spasm to confusion, delirium,
and seizure activity. Symptomatic hypocalcemia is a medical emergency
and should be treated with intravenous calcium salts, whereas
asymptomatic hypocalcemia may be treated with oral calcium
preparations.