33rd Annual Scientific Meeting proceedings

Surgery in the maxillofacial region has several complications that are unique to the anatomy and several that are potential issues in any surgery. Most of the complications that arise are predictable and many of these are either avoidable or manageable with appropriate preparation. Generally, the complications that arise can be divided by the timeline of when to expect them. That is in the peri-operative, immediate post operative or delayed post operative phase. Avoiding these complications almost universally involves preoperative planning and has much more to do with what was done prior to entering the OR than what is done in the OR.

Blood Loss
The most significant perioperative complication is hemorrhage. The maxillofacial region has an excellent blood supply, which is generally helpful as it results in rapid healing and makes this area relatively resistant to infection. However, it can also result in significant hemorrhage. For most surgeries in this region, it is important to have preoperative bloodwork to identify patients that have preoperative anemia, as well as a blood type and blood available for transfusion intraoperatively. This can be through a commercial blood bank, hospital run blood bank or through autologous transfusion. A study evaluating autologous transfusion was recently published by myself and colleagues and resulted from the realities of private practice where maintaining a blood bank can be challenging. Because most maxillofacial procedures are scheduled, it is possible to prepare an autologous transfusion for patients. In general, this required mild sedation and can be coordinated with other diagnostic procedures such as staging. Blood should be collected between 7 and 28 days prior to scheduled surgery. The blood can be administered as whole blood or plasma and packed RBCs. My preferred method of administration was to start the plasma at the beginning of surgery and then start the packed RBCs when necessary. There are many benefits to this approach, as it spares the blood bank supply, is more economical, and may create a state where the patient has a mild regenerative anemia leading up to surgery, which will result in faster RBC production around the time of surgery.¹

Another important method of mitigating blood loss, especially for cases of maxillary surgery is temporary ligation of the carotid arteries with Rummel tourniquets. It is important to remember that this technique should only be used in dogs, as cats do not have the collateral circulation to accommodate temporary carotid ligation.² A recent study evaluated direct ligation of the maxillary artery via either enucleation or removal of a segment of the zygomatic arch prior to maxillectomy to decrease intraoperative blood loss.³ If this approach is taken, it is important to remain outside of the tumour capsule and intended margins when approaching the maxillary artery. If this is not possible, temporary carotid ligation is recommended.

Performing the surgery efficiently is also an important element of decreasing rapid blood loss, especially for maxillectomy and mandibulectomy. As well, the procedure should be planned with the portion of the resection that is expected to bleed the most performed last to allow quick access to bleeding vessels. Speed is facilitated with experience in the procedure and practicing on cadavers prior to performing advanced procedures to ensure technical proficiency. Another important aspect is having a trained assistant who can anticipate what is needed in a critical situation. One technical aspect that is often not considered is the sharpness of the blades and osteotomes uses. For maxillectomies and mandibulectomies, I recommend using a new saw blade, or at least monitoring the number of times the blade is used. If the blade is dull, it will burn through the bone and slow your progress, which can make a considerable difference to the amount of blood loss. Similarly, for parts of the procedure where an osteotome is used, it is extremely important that the osteotome is sharp.

Checklists
Checklists are routinely used in the aviation industry to ensure safety and to remove human error. Failure to use a checklist by a pilot is considered a violation of flight protocol and a flight error. In the developed world, nearly half of all harmful events that affect human patients are related to surgical care, suggesting that improving safety with tools such as checklists, has the potential to have a major impact on patient safety. Surgical checklists are now routine in human surgery with the aim of reducing surgical complication rate. The most notable recent publication to this end was published in the New England Journal of Medicine in 2009.  Using a standard surgical checklist that involved anesthesia, OR personelle, ICU personelle and the surgical team, a system evolved that significantly reduced the global surgical complication rate in eight hospitals worldwide. The mortality rate declined from 1.5% to 0.8% with the use of the checklist and the inpatient complication rate decreased from 11.0% to 7.0%. They are also becoming mainstream in veterinary surgery. The use of a surgical safety checklist is one of the most important tools for preventing complications in any surgery. For maxillofacial surgery, it will ensure that blood products are available and that potential complications have been discussed by the team.

The checklist creates three stop points that allow for communication between the surgical team members: prior to anesthesia, prior to the skin incision and prior to recovery. The first step is called sign in. Before induction of anesthesia, members of the team confirm the patient identity, surgical site, and risk of blood loss. The second step of the process is a time out just prior to making the incision. At this step, the entire team (including visitors and observers in the OR) are introduced, including their role, the patient identity, site and procedure are confirmed, the surgeon reviews critical and unexpected steps, the anesthesiologist review concerns and the nursing staff review equipment concerns. Confirmation of antibiotic administration and that the relevant imaging is displayed is also performed at this step. At the completion of the procedure, a third step, called time out, is performed. The procedure is recorded, needle, sponge and instrument count is complete, specimens are labeled, equipment issues are addressed and other concerns or necessary procedures prior to recovery as well as the plan for post operative care are reviewed.

Preoperative staging and imaging
Preoperative staging and imaging in the context of maxillofacial oncologic surgery often involves CT scan. Staging is critical to ensure that the surgery performed is appropriate and advanced imaging can greatly assist in surgical planning to achieve complete margins, which in turn will decrease the risk of local recurrence, because it shows the extent of the tumour.

Sentinel lymph node mapping can also be performed during CT for staging and will help direct lymph node removal. This can be beneficial because elective neck dissection of all four lymph nodes can result in significant post operative swelling and seroma.⁶ Although not detrimental on it’s own, if the sentinel lymph node can be identified, this will decrease surgical time and the risk of seroma formation. Anecdotally, if an axial pattern flap is used as part of reconstruction, elective removal of both mandibular and retropharyngeal lymph nodes should be avoided as it may contribute to flap failure.

Incisional complications
Despite the fact that maxillofacial surgery is often not a sterile field, the rate of infection is relatively low and when it occurs, it can generally be managed with antibiotic therapy. Perioperative antibiotics are recommended to prevent this complication. The decision to use post operative antibiotics is more controversial. In my hands, I tend to use 5-7 days of antibiotic therapy.

Simple incisional dehiscence can often be managed conservatively or with a minor corrective procedure. Axial pattern flaps used in this region for reconstruction. Anecdotally, the caudal auricular axial pattern flap is not as robust in my hands at the superficial temporal or facial axial pattern flap. The use of these flaps for reconstruction requires careful planning prior to surgery.

The incisional complication that can be most difficult ot manage is oronasal fistula. This is most likely to occur secondary to maxillectomy. It is best avoided with a tension-free reconstruction of the palate using the mucosa of the upper lip. However, even with meticulous surgical technique, this complication may occur and will need to be addressed surgically.

Summary
Many of the complications that arise during and after maxillofacial surgery can be avoided or mitigated with careful surgical planning. This involves preoperative advanced imaging, planning for and avoiding blood loss, solid knowledge of the surgical technique and reconstruction plan.

References

1. Sharma S, Boston SE, Kotlowski J, Boylan M. Preoperative autologous blood donation and transfusion in dogs undergoing elective surgical oncology procedures with high risk of hemorrhage. Vet Surg. 2021 Apr;50(3):607-614. doi: 10.1111/vsu.13598. Epub 2021 Feb 26. PMID: 33634898.
2. Holmberg DL. Sequelae of ventral rhinotomy in dogs and cats with inflammatory and neoplastic nasal pathology: a retrospective study. Can Vet J. 1996 Aug;37(8):483-5. PMID: 8853882; PMCID: PMC1576437.
3. Carroll KA, Mathews KG. Ligation of the Maxillary Artery Prior to Caudal Maxillectomy in the Dog-A Description of the Technique, Retrospective Evaluation of Blood Loss, and Cadaveric Evaluation of Maxillary Artery Anatomy. Front Vet Sci. 2020 Nov 5;7:588945. doi: 10.3389/fvets.2020.588945. PMID: 33251269; PMCID: PMC7674398.
4. Haynes AB, Weiser TG, Berry WR et al. A Surgical Safety Checklist to Reduce Morbidity and Mortality in a Global Population. N Engl J Med 2009; 360:491-499.
5. Randall EK, Jones MD, Kraft SL, Worley DR. The development of an indirect computed tomography lymphography protocol for sentinel lymph node detection in head and neck cancer and comparison to other sentinel lymph node mapping techniques. Vet Comp Oncol. 2020 Dec;18(4):634-644. doi: 10.1111/vco.12585. Epub 2020 Mar 25. PMID: 32134562.
6. Green K, Boston SE. Bilateral removal of the mandibular and medial retropharyngeal lymph nodes through a single ventral midline incision for staging of head and neck cancers in dogs: a description of surgical technique. Vet Comp Oncol. 2017 Mar;15(1):208-214. doi: 10.1111/vco.12154. Epub 2015 Jun 3. PMID: 26040551.