Key-words:
Anterior cervical discectomy and fusion - endotracheal tube - reinforced endotracheal
tube
Introduction
Anterior cervical discectomy and fusion (ACDF) is a basic procedure commonly performed
in anterior cervical surgery.[[1]] Single-level ACDF can be completed quickly and is not highly invasive. However,
collaborative patient management between spine surgeons and anesthesiologists is crucial
for the procedure considering the possibility of intraoperative airway difficulties
and postoperative complications.[[2]],[[3]],[[4]] We recently observed ventilatory impairment during an ACDF operation caused by
bending of the endotracheal tube in the oral cavity. Therefore, we explored the potential
causes of intubation tube obstruction in cervical anterior surgery and present our
findings here.
Case Report
The patient was a 66-year-old woman who had undergone anterior decompression and fusion
at C5–C7 for cervical ossification of the posterior longitudinal ligament 20 years
before admission at a different hospital. At our hospital, ACDF was performed to treat
the adjacent segment disease at the C4/C5 level. The patient was placed under anesthesia
and intubated using a 7.0-mm tracheal tube (TaperGuard®, Covidien, Tokyo, Japan),
assisted by McGrath® video laryngoscopy (Aircraft Medical, Edinburgh, UK). The patient's
head was immobilized using a collar, with the head facing straight up and the neck
tilted slightly back. ACDF was performed using the right cervical approach following
the Smith–Robinson method.[[5]] The operative level was ascertained by lateral X-ray fluoroscopy [[Figure 1]]a. The C4/C5 space was opened using a Casper-type spreader, and the disc was removed.
The posterior bone spurs and joints of Luschka were partially removed. Next, the posterior
longitudinal ligament was cut, the dural sac and nerve root was decompressed, and
a fusion cage was inserted. Subsequently, the patient's lower jaw was elevated slightly
toward the head [[Figure 1]]b. Shortly thereafter, the patient's airway pressure, which was monitored by the
anesthetic machine, rose to 34.8 cm H2O [[Table 1]]. Inspection of the operative field revealed no hematomas or other sources of airway
compression. The tracheal retraction was discontinued, yet the airway pressure remained
elevated. Since the patient's vital signs were still stable, the surgeons decided
to quickly close the surgical wound. Fluoroscopy images from the cage insertion were
checked again and showed a bent tracheal tube in the oral cavity. After surgery, the
surgical drape was removed and the tube was reset by hand under direct visual observation
by laryngoscope. The patient's ventilation returned to satisfactory levels, she was
taken off anesthesia, and the endotracheal tube was removed. The total surgery time
was 97 min, and the over 25 cm H2O high airway pressure duration was approximately
9 min.
Figure 1: (a) Fluoroscopic X-ray image during the operation to confirm the disc level (side
view). A Cathelin needle is inserted at the C4/C5 level, and the tracheal tube is
gently curved. (b) Fluoroscopic X-ray image taken after fusion cage insertion (side
view). Compared with Figure 1a, the lower jaw is slightly elevated toward the head.
The tracheal tube is visibly bent at the root of the tongue (red arrows)
Table 1: Maximum airway pressure profile
Her postoperative course was not remarkable, and she was discharged following rehabilitation.
Discussion
This case presents an important procedural issue: the endotracheal tube can bend inside
the oral cavity at a location far from the operative field during anterior cervical
surgery. It also presents the importance of selecting a reinforced (spiral) tube during
such a procedure.
When we first observed impaired ventilation in the patient, our first conjecture was
that the tube had been obstructed when retracting the trachea to expand the surgical
field. However, the airway pressure did not subside even after the retraction was
stopped. We next suspected that the elevation of the lower jaw was the cause; specifically,
the bending of the tube was thought to be the result of compression by the root of
the tongue [[Figure 2]]. To confirm, we performed postoperative tests using the same model of endotracheal
tube as that used in the operation. When the tube was set in a straight line [[Figure 3]]a, it only deformed slightly in response to applied anterior pressure [[Figure 3]]b. By contrast, when it was pulled to the side to simulate the contralateral trachea
retraction to the incision site in the anterior cervical approach [[Figure 3]]c, it easily bent under the same anterior pressure [[Figure 3]]d. These simulations led us to conclude that, in this case, anterior pressure from
the tongue root caused the tracheal tube to bend and become obstructed due to the
patient's elevated lower jaw while the trachea was retracted (i.e., when her tube
was shifted to the side). When a patient's breathing becomes impaired during an operation,
the first suspected cause is usually airway difficulties at the operative level. The
present case illustrates the importance of checking other sources of the problem,
foremost among them, the inside of the oral cavity.
Figure 2: Schematic of orotracheal intubation during the surgery (sagittal cross-section).
Slight elevation of the lower jaw toward the head (red arrows) results in anterior
pressure on the tube by the tongue root (blue arrows)
Figure 3: A 7.0-mm endotracheal tube (TaperGuard®, Covidien, Dublin, Ireland) is tested after
the procedure. The trachea is modeled by the syringe and the tongue root by the finger.
(a) Front view. (b) Lateral view. The tube deforms only slightly when anterior pressure
is applied. (c) Front view. The trachea is retracted laterally, simulating the present
case. (d) Side view. The tube is deformed in response to anterior pressure
The selection of a reinforced tracheal tube, with a spiral-wound wire in the inner
wall, is often recommended for anterior cervical surgery. However, in clinical practice,
surgeons might not choose to use one due to the relative ease of airway management
when the patient lays supine (anterior approach) rather than prone or when the operation
length is short, especially for single-level procedures, as was the case here. We
performed similar tests on a reinforced endotracheal tube for comparison (TaperGuard®
Reinforced, Covidien). When the simulated airway was retracted [[Figure 4]]a, the tube did not bend even when considerable anterior pressure was applied [[Figure 4]]b. Therefore, we believe that the ventilation difficulties we observed in this case
would not have occurred if we had used a reinforced tube. We, therefore, recommend
proactively selecting a reinforced tracheal tube for cervical spine operations for
posterior approaches in prone positions, as well as for anterior approaches in supine
positions.
Figure 4: Similar testing is performed on a 7.0-mm reinforced endotracheal tube (TaperGuard®
Reinforced, Covidien, Dublin, Ireland). (a) Front view. The trachea is retracted laterally,
simulating the present case. (b) Side view. The reinforced tube does not bend, even
in response to strong anterior pressure
There is one limitation to this report to consider. We surmised that the endotracheal
tube bending during retraction was most likely induced by three-dimensional stresses
on the tube; however, our tests did not constitute a scientific validation of this
proposed mechanism.
Conclusion
This report documents the case of a patient whose breathing was impaired during ACDF
when her endotracheal tube bent in her oral cavity. Based on our experience, we recommend
the use of reinforced tracheal tubes with a spiral-wound wire in the inner wall for
cervical surgery, even when an anterior approach is used. Importantly, in the event
of impaired breathing during such an operation, the oral cavity should be inspected
for confirmation of an open airway.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patient has provided her consent for her images and other clinical
information to be reported in the journal. The patient understands that her name and
initials will not be published, and due efforts will be made to conceal identity,
but anonymity cannot be guaranteed.
