Discussion
Intraoperative pneumothorax is a rare, albeit known, complication of
posterior spinal surgery possibly that can result from a difficult
dissection, aberrant probe or screw placement, or barotrauma. Initial
management typically consists of evacuating the pneumothorax by needle
aspiration, percutaneous placement of a drainage catheter, or tube
thoracostomy. Prone positioning during scoliosis surgical procedures may
affect access to those intervention sites.
Although certainly on the differential for any intraoperative
respiratory problem, the development of a pneumothorax is primarily a
clinical diagnosis that relies on a high index of suspicion. Some
clinical findings suggestive of a pneumothorax include sudden increased
airway pressures, unexplained hypoxia, rising end tidal carbon dioxide,
and unilateral absence of breath sounds to auscultation. Under positive
pressure mechanical ventilation, intrapleural pressures can rapidly
increase from an unrecognized pleural defect to become a tension
pneumothorax. This can be life threatening, resulting in quick
deterioration including tachycardia, tachypnea, hypotension, and
tracheal and cardiac deviation leading to severe hemodynamic compromise
and cardiopulmonary collapse.4
Interestingly, we observed none of these clinical signs throughout the
procedure until the end of the case when turning from prone back to
supine position. There were no airway or pulmonary issues that occurred
prior to that incident that would suggest a pneumothorax. One possible
explanation is that a pleural tear occurred during hardware placement
and the increased intrathoracic pressure was relieved during the
open/prone portion of the case. Thus air trapping only manifested once
the wound was closed and the patient returned to supine position.
Additionally, the development of the pneumothorax may have progressed
slowly due to the patient spontaneously breathing during wound closure
with pressure support ventilation. Outside of known pleural tears, there
have also been reports of spontaneous pneumothorax (without evidence of
intraoperative pleural injury) in the perioperative period following
posterior spinal fusion surgery, with a reported incidence 0.2 to
1.6%.5-7 Potential risk factors for the development
of an intraoperative pneumothorax include blebs or bullae, or longer
amounts of time in the chest with multiple passes and probing. In the
absence of a known pleural injury or these risk factors, potential
causes of a pneumothorax in the perioperative period are few.
Re-expansion of an occult pneumothorax or damage from elevated peak
inspiratory pressures are possibilities. Of note, underlying pulmonary
dysfunction has not been associated with an increase in the overall risk
of pulmonary complications during spinal deformity
surgery.8
Our differential diagnosis for the hypoxia consisted of atelectasis,
inadequate minute ventilation, pain, endotracheal tube migration, fluid
overload, mucous plug, neuromuscular weakness, and pneumothorax.
Although pneumothorax is not usually high on the differential for
hypoxia in most circumstances in the operating room, the hypoxia that
occurred in our patient was acute and severe. Fortunately, the timing of
our patient’s respiratory distress opened several diagnostic and
therapeutic options that would have been difficult in the prone
position. We ruled out other potential causes and then quickly obtained
a portable chest radiograph confirming a pneumothorax. Transthoracic
ultrasound is another valuable tool used to pare down the list of
diagnoses in a hypoxic patient, potentially leading to a timelier
intervention.9 Unfortunately, we are unable to discern
the etiology of the pneumothorax in our patient but it most likely
resulted from a difficult dissection. Our surgical team never had any
indication that a pleural injury occurred.
The delayed hypoxia in this patient is an unusual event related to an
intraoperative pneumothorax. Having had no indication of any respiratory
problems throughout the case and then to have severe and acute hypoxia
on emergence is a rare complication. It is therefore imperative to
recognize the clinical signs that may warrant an intervention to
maintain the patient’s safety.