Introduction
Anterior cervical spine surgery (ACSS) is performed widely for the treatment of cervical spine disorders and has produced favorable clinical outcomes [1]. However, these procedures carry a risk of complications. Acute airway obstruction (AAO) is one of the most serious complications and is potentially life-threatening; the reported incidence ranges from 0.57% to 6.1% [2,3]. Postoperative conditions, such as airway edema and hematoma, may increase the risk of AAO [3–9].
Some authors have advocated for prolonged intubation and intensive care unit (ICU) management to prevent AAO [4,5,10–12]. However, these protocols often involve significant resource demands, increased sedation-related risks, and patient discomfort.
At our institution, patients were traditionally extubated immediately after ACSS and were monitored in private rooms in the general ward. A fatal case of AAO, however, prompted our reassessment of this approach. After a comprehensive review of both the institutional practices and the existing literature, 10 preventive measures were developed to address both intraoperative and early postoperative risks while preserving the feasibility of immediate extubation.
The key objectives of this study were (1) to analyze the clinical characteristics of AAO cases after immediate extubation and (2) to evaluate the effectiveness of the preventive measures in reducing AAO incidence. Through a detailed analysis of both clinical cases and preventive strategies, we assessed whether immediate extubation should remain a viable practice, particularly in view of the growing trend favoring prolonged intubation after ACSS.
Materials and Methods
This study was approved by the Institutional Review Board (IRB) of Gakkentoshi Hospital (IRB approval number: 2024005), a single private orthopedic hospital with 50 acute care beds. Informed consent was obtained from all individual participants included in the study. The study included consecutive patients who underwent ACSS between April 2006 and July 2024 for cervical pathologic conditions, such as cervical spondylotic myelopathy, radiculopathy, or ossification of the posterior longitudinal ligament (OPLL). Suitability for ACSS was based on clinical and radiographic evaluations. Patients with OPLL extending from the cranium to the dens, significant comorbidities, or osteoporosis and those unable to adhere to postoperative rest requirements were excluded from the study; those patients underwent alternative procedures, such as laminoplasty. In addition, patients with tumorous conditions, traumatic injury, or infection were excluded from this study.
ACSS procedures
While under general anesthesia, the patients were positioned supine with the head and neck tilted backward. Somatosensory evoked potentials were monitored intraoperatively in all patients. The procedure involved left-sided access. A Caspar cervical retractor was used to maintain the surgical field. Under surgical microscopy, corpectomy, discectomy, or hybrid decompression was performed, according to the pathologic condition and clinical symptoms [13].
To perform reconstruction, the surgeons used intervertebral cages packed with autologous iliac bone for the discectomy segments and autologous fibular strut grafts/iliac bone grafts for the corpectomy segments. Plate fixation was standard for decompressed segments, and for cases involving multilevel corpectomy of more than three vertebrae, a halo vest was applied. Patients were extubated immediately after surgery and were monitored overnight in private rooms in the general ward; drains were removed the next morning or the following day.
Retrospective analysis of patients
We reviewed patient characteristics (age, gender, and diagnosis) and surgical parameters (number of fixed disc segments, number of upper vertebra instrumented, simultaneous posterior fixation, and application of a halo vest) from medical records. Postoperative airway compromise that necessitated reintubation or hematoma evacuation was defined as AAO. Patients who underwent ACSS through January 2019 were divided into AAO and non-AAO groups, and the patient characteristics and surgical parameters of the two groups were compared to identify risk factors. Furthermore, detailed treatment courses for AAO were analyzed.
AAO preventive measures
In February 2019, we implemented the following 10 preventive measures in accordance with our experience with AAO cases and a review of the literature:
For airway edema prevention
(2) To avoid simultaneous posterior fixation or halo vest application, prioritize the more stable multilevel discectomy over multilevel corpectomy [4].
(3) Elevate the patient’s head slightly forward with stacked towels to reduce tracheal tension and alleviate pressure from the retractor during surgery [15].
(4) Instill 3.3 mg of dexamethasone directly into the surgical site before wound closure to prevent prevertebral soft tissue swelling [16–20].
(5) After the operation, elevate the head of the bed by 30° to improve ventilation and venous drainage [7].
For hematoma prevention
(6) Maintain blood pressure within the normal range during surgery to ensure effective hemostasis [21].
(7) Position drains along the surgical approach without penetrating the muscle layers to prevent bleeding upon removal.
(8) Use minimal wound dressing to easily detect postoperative bleeding or neck swelling.
(9) Maintain general anesthesia with remifentanil, and continue remifentanil infusion until extubation to prevent emergence coughing [22].
(10) For agitated patients, administer dexmedetomidine overnight for moderate sedation after surgery [23].
Comparison of patients before and after implementation of preventive measures
We compared outcomes of patients who underwent ACSS between April 2006 and January 2019 (before implementation of prevention measures) with those of patients who underwent ACSS between February 2019 and July 2024 (after implementation) to evaluate the effects of the preventive measures on AAO occurrence.
Statistical analyses
To perform statistical analyses, we used R ver. 3.4.3 (R Foundation for Statistical Computing, Vienna, Austria). Student t-test was used to compare data for continuous variables, and Fisher’s exact test, for categorical variables. We used the Cochran-Armitage trend test to assess associations between categorical variable. A p-value of <0.05 denoted statistical significance.
Results
Retrospective analysis of data obtained before implementation of preventive measures
We analyzed the outcomes of 1,036 patients who underwent ACSS before the implementation of AAO preventive measures. In one patient, surgery was prolonged because of severe OPLL and restricted jaw opening; all the other patients were extubated immediately after surgery and monitored overnight in private rooms in the general ward.
AAO occurred in seven patients (0.68%; six men). The clinical characteristics of these seven patients are summarized in Table 1. The median age was 59 years (range, 46–70 years), and the number of fixed disc levels ranged from 2 to 5 (median, 4). One case (patient 3) involved simultaneous anterior and posterior fixation. Halo vests were applied in three cases (patients 2, 3, and 4). Surgical time ranged from 89 to 286 minutes (median, 157 minutes), and intraoperative blood loss ranged from minimal to 110 mL. The time interval from surgery to intervention for AAO ranged from 2 to 72 hours (median, 32 hours); in five patients (71%), drains were still in place when AAO occurred. The primary causes of AAO included hematoma (in patients 1, 6, and 7), airway edema (in patients 2 and 3), postoperative C4 segmental cord disorder (in patient 4), and mucus obstruction (patient 5).
Of these seven patients, 3 (50%; patients 4, 5, and 6) were reintubated successfully on the first attempt. Fiberoptic intubation by an anesthesiologist was performed successfully in two more (patients 2 and 3) after the initial oral intubation attempts failed. Hematoma evacuation before reintubation resulted in favorable outcomes in two of three cases (patients 1 and 6), but in one case (patient 7), intubation failed and the patient died. Another patient (patient 5) sustained hypoxic brain damage despite reintubation; thus, poor outcomes occurred in 0.19% of all patients.
According to the clinical symptoms (Table 2) [5,6,9], five patients (1, 2, 3, 4, and 6) were in early to middle-stage AAO, and two were in the late stage (patients 5 and 7) when intervention was initiated. Four patients (1, 2, 3, and 6) recovered fully, and a patent airway tracheostomy was achieved in one case (patient 4).
The comparison between the AAO group (n=7) and the non-AAO group (n=1,029) revealed that the incidence of AAO was significantly associated with the number of fixed disc segments (p=0.031) and the number of the more cephalad vertebra that were instrumented (p=0.007) (Table 3). Patients in the AAO group had significantly more fixed disc segments (3.6±1.3) than did those in the non-AAO group (2.8±0.9; p=0.031), and the proportion of patients who received a halo vest was significantly higher in the AAO group (42.9%) than in the non-AAO group (2.0%; p<0.001). These findings are illustrated in Fig. 1.
Analysis of data obtained after implementation of preventive measures
After the implementation of preventive measures, 156 patients (the countermeasure group) underwent ACSS. The number of fixed disc segments was significantly lower in the countermeasure group (2.2±0.9) than among the 1,036 earlier patients (2.8±0.9; p<0.001). The frequency of halo vest application was also lower in the countermeasure group (0.6%) than in the earlier cohort (2.3%), but the difference did not reach statistical significance (p=0.237). Of note is that in the countermeasure group, no cases of AAO were reported; however, because of the limited number of cases, statistical significance regarding the effectiveness of the preventive measures could not be determined (Table 4).
Discussion
In this study, we examined seven cases of AAO that occurred in patients who were extubated immediately after ACSS. The incidence of AAO was 0.68%, and hypoxic brain damage or mortality occurred in 0.19%; these findings are consistent with those previously reported [2,4,8,24–26]. After the implementation of our 10 targeted preventive measures in February 2019, no cases of AAO were reported after 156 subsequent ACSS procedures; this finding suggests the potential effectiveness of these measures.
Surgery-related risk factors
In accordance with previous studies [2,5,14,24], our results showed that a greater number of fixed disc segments (p=0.031), a more cephalad surgical range (p=0.007), and the application of a halo vest (p<0.001) were significantly associated with AAO. Halo vests restrict head and neck movement, thereby hindering deep breaths and secretion clearance, which increases the risk of airway obstruction. In addition, frequent suctioning may irritate the laryngeal mucosa and lead to bleeding and edema.
These findings highlight the importance of minimizing multilevel exploration and avoiding cephalad surgical extensions when feasible. During the surgical planning stage, as part of our preventive measures, we selected the posterior approach for cases involving C2 or multilevel fixation of more than three segments. Furthermore, by selecting the more stable multilevel discectomy over the multilevel corpectomy, we reduced the application of halo vests. When the aforementioned surgical approaches are not feasible, we consider delaying extubation.
Postoperative hematoma
AAO caused by hematoma typically develops 6–12 hours postoperatively, whereas airway edema tends to appear 12–72 hours after surgery [5,27]. Hematoma is a significant cause of AAO and can result from insufficient intraoperative hemostasis, excessive coughing during extubation, or postoperative hypertension [5,7,9]. In our series, patients 1 and 6 exhibited persistent postoperative agitation and hypertension, which probably contributed to the postoperative formation of hematomas.
Patients with hematomas often exhibit anterior neck swelling and possible tracheal deviation [9]. Severe swelling can hamper oral intubation and emergency cricothyrotomy [7]; therefore, the hematoma should be evacuated immediately through the surgical incision. According to one review, seven of 13 patients underwent hematoma evacuation before reintubation [6].
In comparison with emergency oral intubation, hematoma evacuation can be performed more immediately, regardless of location or equipment, and its decompression effect may relieve respiratory distress. In our series, patients 1 and 6 showed improvement after hematoma evacuation. The procedure typically involves the removal of sutures from the surgical wound, often without requiring local anesthesia. If the patient’s respiratory status remains compromised, intubation should be attempted promptly.
As a part of preventive measures, blood pressure is maintained within the normal range to ensure intraoperative hemostasis, which reduces the risk of bleeding after surgery [21]. To minimize risk of bleeding after removal, surgical drains are positioned along the approach without penetrating muscle layers. Postoperatively, wound dressings are minimal so as to facilitate the early detection of bleeding or swelling. Remifentanil infusion is maintained until extubation to prevent emergence coughing without causing respiratory depression [22,28,29]. After extubation, low-dose dexmedetomidine is administered overnight to agitated patients for moderate sedation with minimal respiratory effects [23,30].
Airway edema
Laryngopharyngeal edema resulting from surgical manipulation and retraction is a significant contributor to postoperative respiratory distress. Airway edema often does not manifest with visible neck swelling, but it can make reintubation difficult; thus, alternative airway management methods should be considered during surgical planning [7]. In our study, airway edema occurred in patients 2 and 3, manifesting in both more than 60 hours postoperatively. Both patients 2 and 3 received halo vests; patient 3 had undergone simultaneous anterior and posterior fixation. In both patients, oral intubation failed, but fiberoptic intubation by an anesthesiologist was successful. Simultaneous anterior and posterior fixation increases the risk of airway edema because of the manipulation of ventral soft tissue and prolonged prone positioning [4].
To reduce the risk of airway edema, we implemented several strategies. In the surgical planning stage, simultaneous anterior and posterior fixation was avoided when feasible. The head was elevated slightly forward with stacked towels to reduce tracheal tension, thereby alleviating the retractor-induced pressure during surgery [15]. Dexamethasone was applied locally before wound closure to reduce prevertebral soft tissue swelling because studies have shown that corticosteroids safely inhibit inflammatory prostaglandins and cytokines [16–20]. Postoperatively, the head of the bed was elevated by 30° to improve venous drainage and ventilation [7,15].
Timing and management of extubation
Some authors have advocated prolonged intubation and ICU management to mitigate the risk of AAO [4,5,11,12]; however, the timing of extubation after ACSS remains controversial. In our series, interventions for AAO occurred at a median of 32 hours postoperatively; 71% of cases were identified after 24 hours. These results suggest that overnight intubation alone does not effectively prevent AAO. At the same time, prolonged intubation has risks, including ventilator-associated pneumonia, tracheal injury, and hemodynamic instability [31,32]. We generally perform immediate extubation but consider prolonged intubation for patients with previously reported high-risk comorbidities or surgery-related risk factors [3–5].
Airway management after extubation
AAO can progress rapidly from asymptomatic to complete obstruction within minutes [8,9]; thus, early recognition and timely intervention are critical. For the systematic evaluation, Song et al. [9] classified AAO according to respiratory status, surgical site condition, and patient behavior. Similarly, Yamada et al. [6] categorized AAO symptoms into three stages, in reference to prior reports. Early- or middle-stage interventions are often effective, whereas late-stage progression is associated with poor outcomes, including death or hypoxic brain injury. In accordance with these classifications, the stages of AAO symptoms are summarized in Table 2.
In our series, five of seven cases of AAO were treated successfully in the early or middle stages; the two that progressed to the late stage resulted in poor outcomes. To improve the monitoring of airway obstruction after extubation, medical staff should regularly measure the patient’s neck circumference for early detection of swelling and assess the respiratory rate in distressed patients. According to Yamada et al. [6], a neck circumference increase of >2 cm and a respiratory rate of >25 breaths/min are the criteria for emergency intervention. Fig. 2 depicts our perioperative airway management algorithm for AAO prevention in patients who undergo ACSS.
Limitations
This study had several limitations. First, it was conducted at a single institution, and the number of cases of AAO was relatively small; thus, the generalizability of our findings is limited. Moreover, the low incidence of AAO reduced the statistical power of our analyses, which precluded definitive conclusions about the effectiveness of our preventive measures. Second, previously reported risk factors are important for comprehensive risk stratification but were not systematically assessed because of data limitations. In future research, investigators should include these factors to better tailor perioperative protocols. Third, the application of local corticosteroids to the retropharyngeal space after ACSS remains controversial. Further studies are necessary to validate the dose and efficacy of this approach.
Conclusions
We systematically examined AAO prevention strategies, and our results highlight the potential effectiveness of 10 targeted preventive measures. Although the trend toward prolonged intubation and ICU management is increasing, our findings suggest that immediate extubation is suitable for most patients who undergo ACSS. Despite these preventive measures, however, the risk of AAO cannot be eliminated entirely; therefore, rigorous monitoring after extubation is essential.
Key Points
We analyzed the clinical characteristics of acute airway obstruction (AAO) after anterior cervical spine surgery and assessed the effectiveness of 10 newly implemented measures designed to mitigate AAO risk.
AAO occurred in 7 (0.68%) of 1,036 patients. Significant risk factors included the number of fixed disc segments (p=0.031), instrumentation of a more cephalad upper vertebra (p=0.007), and the use of a halo vest (p<0.001).
No AAO was observed in 156 patients who underwent surgery after the preventive measures were introduced; this outcome demonstrates the potential effectiveness of these measures.
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