DOI: https://doi.org/10.21203/rs.3.rs-2271640/v1
Background: During spine surgeries in prone position, intraoperative neuromonitoring induced complications like oral lacerations or hematomas provoked by patient’s own bite during spinal nerve stimulations could pose management difficulties that could potentially complicate patient extubation.
Methods: This study reviews in two one-year periods the incidence of occurring complications first in Group I retrospectively with standard protocols used and secondly in Group II using a proposed new management protocol with the insertion of athletes’ dental guard with preoperative size selection, awake fit-control and meticulous placement after anesthesia induction.
Results: In Group I we encountered two cases with tongue lacerations, one requiring surgical intervention, while in Group II no complications were confronted.
Conclusion: Even though the sample sizes are limited to indicate a significance in this study, our proposed management protocol that focuses on good preoperative planning and accurate intraoperative placement of a bite guard helped us to avoid neuromonitoring-induced oral complications of prone-position spinal surgeries.
Spine surgeries that are performed in prone position have not only increased in numbers over the recent years, but also the extended diversity and incremental difficulty level posed by them have automatically increased the potential risk of iatrogenic neurological injury. In order to minimize these potential neurological complications, use of reliable methods like intraoperative monitoring became more and more crucial in clinical practice and nowadays is being routinely used whenever possible to guide surgeons during the vertebral procedures1. Nevertheless, the use of this intraoperative technique has also potentials to create its own conceivable hazards, one of which is tongue laceration provoked by patients’ own bite induced through the spinal nerve stimulus given by the monitoring system to check integrity of the nerves during surgery. The jaw muscle contractions during these stimulations are the main cause of this injury but with the offset of neuromuscular blocker’s effect, as well as being in prone position which applies further gravitational forces on the tongue, these patients are more disposed to extract their tongues outward their teeth occlusion lines between their upper and lower jaws. Additionally, the prone position could potentially hinder the venous and lymphatic drainage of the tongue, thus could easily alleviate swelling even with minimal trauma. Previous case reports on this specific group of patients have reported minor tongue lacerations and broken teeth with an incidence of 0.2% to 0.6%2. Apart from these known complications, as the arterial supply of the tongue is very rich, nearby tongue lacerations, we were also concerned if this type of injury could cause severe tongue hematoma or swelling as well as oral bleeding that may lead to further airway obstruction and complicate extubation of the patients. Thus, in this study, we have not only retrospectively reviewed the last year’s caseload to assess the incidence of occurrence of intraoperative monitoring related complications in prone position during spinal surgery, but we also prospectively assessed a management protocol that we have introduced to use thereafter, in which we have integrated an easily attainable athletes’ dental guard with the hope to prevent occurrence of tongue lacerations and other related events during these procedures.
This prospective project was reviewed and approved by Ankara Unıversıty Faculty of Medıcıne Clınıcal Research Ethıcs Commıttee with 2021000020-2 Registration Number at 05/04/2021.
Data of all patients who had intraoperative monitoring during vertebral surgeries in prone position at the neurosurgical unit of our tertiary institution between December 2019 and December 2020 as well as December 2020 and December 2021 in two groups were included in the study. Group I reflect the one-year period before introduction of our management protocol where in our institution, after intubation all patients received a rolled gauze placed to the oropharynx but the patients who will be operated in prone position with intraoperative monitoring, this was also placed in the oral cavity to prevent tube bites and kinking3. Group II reflect the one-year period after our
enhanced management protocol took effect, where on top of gas packing an athletes’ dental guard (with preoperative size selection and fit-control before and after anesthesia induction) and its meticulous placement were added to our practice with the hope to provide better controlling and possibly preventing the earlier encountered complications. All patients in both groups had same neurostimulation protocol, thus stimulation was bilateral, intensity was high, and the method used was voltage. All relevant demographic, preoperative as well as intraoperative data were collected and assessed in terms of complications of intraoperative monitoring use. A comparative evaluation between two groups have been made. Informed consent form was obtained from all participants (As an example shown in Supporting Documents.
In Group I, 100 patients and in Group II 60 patients had vertebral surgeries in prone position where intraoperative monitoring were used. Table 1, summarizes the important data and complications observed. In Group I, 2 patients had severe tongue lacerations, from which one required suturing by the otolaryngologists right away at the end of the procedure. Figure 1, shows lacerations.
Table 1
Comparison of patients’ data Group I before (2019-2020) and Group II after (2020- 2021) enhanced management protocol for tongue laceration in patients operated in prone position with neuromonitoring
|
|
Group I: Patients operated between 2019-2020 (n:100) |
Group II: Patients operated between 2020-2021 (n:60) |
p value |
|
Age (year) |
57.3 ±14 |
55.7 ±15.6 |
0.5 |
|
Gender (male/female) |
54/46 |
20/40 |
0.01 |
|
ASA physical status (1/2/3) |
35/40/25 |
18/26/16 |
0.8 |
|
BMI |
27.2 ±5.2 |
28.1±5.6 |
0.3 |
|
Surgical procedure |
|
|
0.5 |
|
Tumor |
26 |
13 |
|
|
Stabilisation |
74 |
47 |
|
|
Surgical level |
|
|
0.07 |
|
Thoracal |
45 |
16 |
|
|
Lomber |
51 |
41 |
|
|
Sacral |
4 |
3 |
|
|
Length of surgery (min) |
195.2±63.4 |
209±79.4 |
0.2 |
|
Tongue laceration Hematoma Suturation |
2 1 1 |
0 0 0 |
0.5 |
Data are expressed as means ± SD and numbers.
In both patients, the lacerations were detected during extubation, which also made airway management and extubation more difficult than normal. During the extubation and early postoperative period even after the bleeding was controlled and the laceration was sutured, tongue swelling and pain were considerable problems that challenged the anesthesia team in the operating room and surgical team at the wards with the need of extra oral wound care, pain management, solving oral feeding problems which altogether resulted in longer hospitalization. The incidence of this neuromonitoring-induced injury was higher than the described ones in the literature and early postoperative morbidity was considerable.
On the other hand, in Group II when the new management protocol was utilized that integrated the athletes’ dental guard with preoperative size selection, awake fit-control and meticulous placement after anesthesia induction -as shown in Figure 2- in no patients we had encountered a tongue laceration or other bite related injuries throughout the whole procedures.
Comparison of the two groups regarding the complications showed no statistical difference. The neurostimulation characteristics regarding the number of stimulations per cases were similar between patients with lacerations and without lacerations in both groups.
Prone positioning which is commonly used for posterior approaches in spine surgery, is associated with several severe complications like hemodynamic disturbance, ophthalmic conditions, nerve compressions and pressure ulcers4. Likewise, the use of neuromonitoring leads to strong contractions of the biting muscles, that could proceed to tongue bite injury 5. These biting induced oral injuries during neuromonitoring stimulations are rare but concerning complications of the prone positioning 6. Furthermore, prone position is also a risk factor for massive macroglossia due to neck flexion and lingual vein congestion 7. If this condition additionally occurs, it could correspondingly ease and aggravate tongue laceration during neuromonitoring.
Mentioned complications, all together may lead to a need of an emergency ENT intervention as well as delayed extubation with a swollen tongue. Tooth damage, mandibular fracture and even bite-rupture of endotracheal tubes requiring emergency reintubation are described in the literature5. The incidence of these complications seems to be low, however several minor bruising or minimal bleeding also might have been overlooked earlier reflecting an unpredictable incidence. Due to all these factors and risk of serious events, several approaches (use of bite blocks, positioning of the head) have been described in the literature aiming to prevent intraoral injuries during the use of neuromonitoring in prone position8. However, none of them were defined as gold standard for the prevention of neuromonitoring-induced oral wounds at prone position. Therefore, during prone position possible minor or major complications related to the use of neuromonitoring should be anticipated and careful positioning as well as proper protective measures should be planed.
In order to minimize complications, in our institution we have started to use a management protocol by utilizing a silicone athletes’ dental guard, of which the appropriate size is selected while the patient is awake. As our data is also supporting us, nearby preoperative selection of individual fit, it is also important to be vigilant for the proper placement of the selected bite-block. As by doing so demonstrated in Table 1 we have not encountered any single complication. Even though there were no statistical difference between Group I and II, this is due to the small number of patients in both groups and as we did not have any tongue lacerations after the introduction of our management protocol, it would be unethical to try to raise the number of patients in Group I as it would risk unnecessary lacerations.
We believe that preoperative verification of the proper fitting of the bite-blocker to the individual patient’s anatomy while they are already being awake and thereafter its correct placement subsequent to anesthesia induction and before prone positioning seems to be more important factors in our hands than the method being used to block the bite. Nevertheless, in all patients operated in prone position with neuromonitoring, still a proper and detailed postoperative inspection should be performed at the end of surgery, preferably before the extubation. However, as avoidance should be the main goal, an algorithmic approach as proposed in our study could be defined and applied to minimize the adverse effects of neuromonitoring induced bite injuries.
It is important to be aware of rare complications of prone position and the use of neuromonitoring. Prevention of extreme neck flexion, meticulous placing of a well-fitted bite-block oral cavity of all patients before extubation are crucial parts of our management protocol to prevent complications as delineated in our study and treat them timely, if still occurred.