Anaesthetic considerations for major cancer resection and free flap reconstruction in oral cancer: a review

Introduction

Background

Major oral cancer resection and immediate free flap reconstruction operations are long in duration with various predictable intraoperative phases. Patients tend to be older, and often present with multisystem comorbidities. Depending upon the chosen flap site, these procedures can take 12–16 hours or more. From a surgical perspective, the main stages typically consist of: percutaneous endoscopic gastrostomy (PEG) insertion; surgical tracheostomy; dental extractions; neck dissection and access procedures; cancer resection; preparation of the recipient (resection) site to receive the free flap; dissection and raising of the free flap; microvascular anastomosis (free flap warm ischaemia); flap reperfusion; closure of the free flap donor site; reconstruction of the defect with the perfused free flap; and closure of neck dissection and access wounds.

Each operative stage presents various challenges to the anaesthetist, and a detailed knowledge and understanding of these enables appropriate preparation, pre-emptive treatment, anticipation of potential challenges, and prevention of complications. More than one surgical phase may proceed simultaneously with several members of the surgical team operating at different surgical sites at the same time. The anaesthetist must take this into account, tailoring their anaesthetic technique to the combined surgical stimulus, and to maximize surgical access to the patient. Preoperatively, patients should undergo a timely preassessment by an anaesthetist experienced in these procedures, with particular attention paid to comorbidities and their optimisation, where possible. Ongoing intraoperative management of patients’ chronic conditions is often required. A detailed airway management strategy should also be formulated at this juncture.

Rationale and knowledge gap

There is currently no agreed clear consensus on management of this particular group of patients throughout their whole perioperative period. This review is designed to address that gap, and provide achievable and deliverable recommendations to anaesthetists caring for this particular group of patients.

Objective

The objective of this conventional review article is to provide the anaesthetist with an overview of the main intraoperative considerations for the anaesthetic care of patients undergoing major oral cancer resection, with immediate free flap surgical reconstruction. All aspects of intraoperative care are discussed with particular emphasis on the mode of anaesthesia and airway management.

Intraoperative anaesthetic considerations for oral cancer surgery with free flap reconstruction

Pre-anaesthesia checks

Patients may have been administered anxiolytic premedication (depending upon patient and institutional preferences). Care must therefore be taken with pre-anaesthesia checks to ensure the correct patient is present, and that all required documentation including written informed consent is also present and correct. Operative sites should be clearly documented on the operating list and consent form, confirmed by the patient, with both resection site and proposed graft donor site(s) clearly identified (and marked accordingly by the surgeon in advance, during the consent process).

Monitoring

Standard anaesthesia monitoring

Once pre-anaesthesia checks are complete, essential physiological monitoring should be applied, as per the Association of Anaesthetists (1) guidance.

Non-invasive blood pressure (NIBP) with continuous pulse oximetry and electrocardiograph (ECG) monitoring should be established. Ear pulse oximetry sensors are impractical for this type of surgery, so finger probes should be used. Intraoperatively, the position of these probes should be changed at regular intervals to reduce the risk of pressure injuries to the finger, or adjacent fingers. The probe may be placed on patients’ toes, but accuracy may be affected by any concomitant peripheral vascular disease and/or mechanical venous thromboembolic prophylaxis. Three-electrode ECG monitoring is usually sufficient, but patients with co-existent cardiovascular disease may necessitate the use of additional electrodes, thus increasing sensitivity for detecting myocardial ischaemia.

Continuous invasive arterial blood pressure monitoring is recommended to reduce the risks of repeated non-invasive measurements over many hours, to allow rapid detection of cardiovascular instability and to enable repeated arterial blood gas analysis. The chosen site depends primarily on the donor graft site. The radial artery of the non-dominant hand is often preferred, provided an Allen’s test is normal. However, if a radial forearm free flap is planned, avoidance of both radial arteries is advisable (in case of requirement to change donor site intraoperatively). Dorsalis pedis or femoral arteries offer practical alternatives. Communication with the surgical team about all vascular access is key to ensuring the most appropriate sites are chosen. Unless there is a clinical indication to establish continuous invasive arterial blood pressure monitoring prior to induction of anaesthesia, it is common practice to induce anaesthesia with intermittent NIBP measurements, and site the arterial cannula once the patient is anaesthetised, stopping NIBP measurements thereafter.

Depth of anaesthesia

The UK Fifth National Anaesthesia Project 5 (NAP5) recommends depth of anaesthesia monitoring where total intravenous anaesthesia (TIVA) is used, especially where neuromuscular blocking drugs (NMBD) are administered (2). Monitoring of processed electroencephalography (pEEG) can easily be achieved by placing sensors on the forehead prior to induction of anaesthesia, which should provide uninterrupted monitoring for the duration of TIVA, and does not interfere with surgical access. There is some evidence that depth of anaesthesia monitoring may reduce both the risk of accidental awareness under general anaesthesia (AAGA) (3), and by minimising the time spent in burst suppression, the risk of postoperative cognitive dysfunction (POCD) too, potentially enhancing patient recovery (4)—often a significant consideration in this cohort of patients.

Temperature

Hypothermia is associated with several complications, including myocardial ischaemia and other cardiovascular events, increased bleeding and transfusion requirements, surgical site infections, postoperative shivering, delayed recovery and increased hospital length of stay (5). Crucially, a free flap that is allowed to become hypothermic before being raised, or once anastomoses are complete, is at risk of impaired perfusion and increased risk of failure. Meticulous temperature management is therefore imperative. Following induction of anaesthesia, placement of a rectal thermistor-type temperature probe provides an ideal means of continuous intraoperative core temperature monitoring. Typically, patients’ temperature reduces by approximately 1–2 degrees centigrade per hour for the first 2 hours (without preventative action) due to core peripheral heat redistribution and hypothalamic thermoregulatory resetting—which both occur in the anaesthetised state. These effects are exacerbated if PEG and tracheostomy procedures are performed as both procedures require separate skin preparation and surgical draping, such that continued active patient warming with overlying forced air warmers can be difficult to achieve. If available, electric-heated or warm water blankets placed underneath the patient can provide uninterrupted active warming. Fluid warmers offer limited benefit given a restrictive fluid administration policy is generally adopted, however, they may offer some protection against hypothermia during these initial operative phases.

Urine output

A urethral catheter attached to a urometer should be inserted after the patient is anaesthetised, to allow perioperative measurement of urine output and to guide fluid therapy.

Venous access

Due to the complex nature and prolonged duration of these procedures, as well as the comorbid patient population, at least two peripheral venous cannulae (PVC) are generally recommended. A small gauge (e.g., 20-G) PVC is generally used for induction of anaesthesia; after which, a second larger gauge (e.g., 16-G) PVC should be sited. If TIVA is the chosen method of induction and maintenance of anaesthesia, reliability and patency of the PVC must be ensured, as any failure of TIVA delivery could result in AAGA. Where multiple non-compatible infusions are required, central venous access may be more appropriate (though this is rarely needed), especially if a requirement for inotropic or vasoactive drugs is anticipated. If so, the femoral vein is usually used, again being sited with the patient anaesthetised unless their clinical condition dictates otherwise.

Anaesthesia technique

Anaesthesia can be conducted via a volatile-based technique or by using TIVA. TIVA offers a number of practical advantages in these procedures, particularly when a surgical tracheostomy is planned—where there may be several interruptions in the reliable delivery of inhalational anaesthetic agent. Dedicated TIVA administration sets with anti-reflux and anti-siphon valves should be used to improve safety, with propofol and remifentanil ideally delivered via target-controlled infusion (TCI).

If there is no plan for surgical tracheostomy, or the patient has a pre-existing laryngectomy stoma, the choice of method of anaesthetic induction and maintenance is largely based upon anaesthetists’ preference. However, there is increasing evidence that anaesthetic drugs and techniques can influence cancer recurrence rates, although high quality clinical trials are limited. The majority of studies are experimental, laboratory-based, and performed in animal subjects. The few clinical studies in humans tend to be either retrospective observational or post-hoc analyses of secondary outcomes.

Volatile agents

Animal models suggest potential pathways by which volatile agents may increase tumour metastasis (6). Various hypotheses are suggested, including their possible tumour cell survival effects, or possible immunosuppressive effects. One example is reduced natural killer cell gene expression, as was demonstrated in a human pilot study examining serum from women receiving sevoflurane compared to propofol to undergo breast cancer surgery (7). However, different volatile agents seem to offer inconsistent outcomes between different cancer types. Volatiles are proinflammatory and can bring about significant upregulation of hypoxia-inducible transcription factors, which may confer cytoprotective properties to tumour cells via several mechanisms (8). Conversely, some studies suggest volatile agents may actually promote oncoprotective effects, but again findings are inconsistent among different cancer types.

TIVA

Accumulating evidence suggests propofol may have both direct and indirect anti-tumour effects by regulating key molecular pathways in cancer cells (9). Furthermore, it is known to exert anti-inflammatory and antioxidative effects, and such immunomodulation may protect against postoperative immune suppression. Although the clinical effects of propofol on oral cancer recurrence and overall survival have not been directly assessed, several in-vitro studies on other malignant cell lines appear to demonstrate anti-tumour effects. The most closely clinically related study to oromaxillofacial malignancy involves oesophageal squamous cell carcinoma (10), where propofol down-regulated expression of the sex-determining region Y-box 4 (SOX4) gene, which may be a potential prognostic biomarker in some cancers.

Choice of maintenance agent

Cancer surgery outcomes vary when TIVA and volatile agents are compared clinically. Some studies appear to demonstrate benefit from the use of TIVA, whilst others demonstrate no difference. A number of studies have looked at patient survival, circulating tumour cells, immune function and cancer regulatory factors, but these focus mainly on breast, non-small cell lung cancer, oesophageal and colorectal cancers. Patients undergoing sevoflurane based anaesthesia for head and neck squamous cell carcinoma surgery in another pilot study had significantly more hypoxia inducible factor-2alpha gene expression compared to those receiving propofol (11). This may offer increased tumour survival at both local and regional sites by supporting angiogenesis and cell proliferation. Well-designed multicentre randomised controlled trials proving causation between the chosen mode of anaesthesia and patient outcomes remain elusive, and until such time as they are available the current evidence remains mostly circumstantial and extrapolated from laboratory, animal and pilot studies.

AAGA considerations

During TIVA, it is generally advocated that the site of administration is continuously monitored for any potential disconnections or other related issues that may affect reliable anaesthetic agent delivery. This can be difficult to achieve during reconstructive procedures due to the presence of surgical drapes obscuring the anaesthetist’s view. The proximity of the surgical team to PVCs may also make them vulnerable to potential problems. Reliable, visible venous access can usually be obtained via the dorsum of the patient’s foot.

Sustainability considerations

Lifecycle assessments demonstrate that the carbon footprint of a volatile anaesthetic outweighs that of TIVA, even accounting for the increased consumption of single-use plastic and packaging, especially if the latter is entered into appropriate recycling streams. Of all the commonly available volatile agents, sevoflurane carries the least equivalents of carbon dioxide as a greenhouse gas. If volatile agents are used for these prolonged surgical procedures, their carbon footprint may be mitigated somewhat by use of a ‘low flow’ technique. Further reductions in the volume of volatile used may be achieved by utilising anaesthetic machines which incorporate end-tidal target technology. This optimises volatile delivery and fresh gas flow within the boundaries set. There is also increasing access to volatile capture technology, but the efficiency of these devices and the ability to re-extract volatiles remains to be proven.

Airway management

The airway management strategy is dependent upon the preoperative assessment of the patient, any prior airway surgery or treatments (such as radiotherapy), any known previous airway management difficulties, patient comorbidities, and any predicted airway management difficulties related to their current pathology.

Tracheal intubation

If an awake tracheal intubation is planned, this should be carried out as per the Difficult Airway Society guidance (12). If the patient is suitable for airway management following induction of anaesthesia, tracheal intubation may be carried out using direct laryngoscopy, videolaryngoscopy, or asleep fibreoptic intubation (at the discretion of the attending anaesthetist). It is standard practice to utilise a nasotracheal tube for these procedures, to facilitate superior oropharyngeal access to the surgical team—permitting unobstructed views at initial examination under anaesthesia, affording easier access for endoscope insertion for the PEG procedure, and maximizing accessibility for the surgical tracheostomy. A preformed North-facing nasotracheal tube or reinforced tracheal tube are often used, inserted after nasal vasoconstrictor application (to reduce the risk of epistaxis). Care should be exercised to avoid mucosal damage during insertion. If tracheal intubation is achieved via direct or videolaryngoscopy, Magill’s forceps may be required to direct the tip of the tracheal tube through the vocal cords, being careful not to damage the cuff in doing so. Tracheal tube position must be confirmed with continuous waveform capnography.

Neuromuscular blocking drugs

If the patient’s airway is chosen to be secured after induction of anaesthesia, an adequate dose of a NMBD should be administered to facilitate tracheal intubation. Commonly, the NMBD of choice is rocuronium, as this confers rapid and profound neuromuscular blockade (with the potential for immediate reversal with sugammadex) in a patient cohort where airway management difficulties may occur. Its relatively prolonged duration of action also facilitates the subsequent PEG insertion, though a further bolus dose may be required prior to surgical tracheostomy formation to ensure optimum muscle paralysis. Quantitative neuromuscular monitoring is recommended throughout the procedure, but in particular, to ensure full reversal of NMBD prior to patients’ emergence from anaesthesia, and if there is a requirement by the surgical team for intraoperative nerve monitoring (e.g., facial or recurrent laryngeal nerve).

Pre-surgery checks

The patient should be orientated on the operating table with their head positioned away from the anaesthetic machine and ventilator, to maximize accessibility to the patient for the surgical teams. This necessitates the use of breathing circuit and capnography sampling line extensions.

Prior to commencing surgery, a pre-surgical pause should be completed as per the World Health Organization Surgical Safety checklist (13). Prior to skin incision, the patient should be administered a single dose of antimicrobials, as per local surgical prophylaxis guidance. Intravenous dexamethasone is also often given at this time, with the intent of reducing subsequent airway swelling postoperatively (14).

Active warming devices and thromboembolic prophylaxis measures should be applied and checked that they are operational. If a fibular free flap is planned to be harvested, the surgical site should be made accessible, with positioning of the above devices adapted accordingly.

Surgical phases and anaesthetic considerations

PEG or nasogastric (NG) tube insertion

This group of patients are often malnourished at presentation, due to dysphagia or odynophagia associated with the underlying disease process or radiotherapy treatments. Each patient should have a clear nutritional plan devised by the multidisciplinary team during preoperative planning. Postoperative supplemental nutrition may be given via a PEG or NG tube, and the chosen modality varies between institutions—as there is no nationally agreed consensus (15). PEG feeding may be preferred if prolonged nutritional supplementation (for greater than 4 weeks) is anticipated.

PEG insertion is usually undertaken as the first surgical procedure, and requires endoscopic guidance. The patient’s oesophagus is intubated with an endoscope by the surgical team, during which time the anaesthetist must be especially vigilant for accidental tracheal extubation. The operating theatre lighting is often temporarily dimmed to illicit transilluminescence (to confirm correct PEG position), relying upon effective communication between the anaesthetist and surgical team to mitigate complications.

Alternatively, NG tube insertion may be preferred. This is often the case if early resumption of oral intake is anticipated, or if patients have comorbidities that make PEG placement challenging, such as a hiatus hernia. The NG tube can be placed either at the beginning or end of surgery, and can be secured in place using a nasal bridle, with correct tip position confirmed prior to use, as per local guidance.

Tracheostomy insertion

Patients that undergo this type of cancer resection and reconstructive surgery are prone to postoperative upper airway swelling, and the risk of airway obstruction. In particular, patients that have undergone bilateral neck dissection or resection of mandible, tongue, and/or floor of mouth (16) are especially at risk, which can be potentiated by the presence of a bulky reconstructive flap. The risks of postoperative airway obstruction may be reduced by delaying tracheal extubation and continuing mechanical ventilation for a short period (to allow the swelling to subside), or by undertaking an elective tracheostomy as part of their primary procedure. The risks versus benefits of each approach must be taken into careful consideration.

Delayed tracheal extubation may require an exchange of tracheal tube (from nasal to oral) at the end of the surgical procedure. Oral tracheal tubes are less likely to kink and allow greater ease of airway toilet, so are generally preferred to nasal tubes on the intensive care unit (ICU). However, tube exchange is not without risk, particularly given the presence of airway oedema, and any attempts at airway instrumentation must not compromise the newly-anastomosed free flap and anatomical reconstruction. Delayed tracheal extubation also necessitates ongoing sedation and mechanical ventilation, with their associated risks and disadvantages, including ventilator-associated pneumonia and barotrauma, delayed establishment of communication and delayed participation with physiotherapy. Although, verbal communication is likely to be more rapidly established following this strategy than if a tracheostomy is performed. In the absence of a tracheostomy, any issues encountered following delayed tracheal extubation, may necessitate tracheal re-intubation—which may be particularly challenging, and poses further risk of instrumentation to the integrity of the flap anastomosis and reconstruction.

Tracheostomy formation avoids the potential complications of re-intubation, and the need for ongoing sedation and mechanical ventilation. However, the potential benefits must be balanced against the risks associated with tracheostomy, including haemorrhage, tracheostomy tube blockage/displacement, infection and laryngeal stenosis. There is no clear consensus on the optimal strategy for postoperative airway management in this patient group, although some tracheostomy prediction models have been designed in an effort to guide decision making (17,18). Each patient should have clear discussion between the multidisciplinary team to guide their individualised postoperative airway management pathway.

For intraoperative tracheostomy formation, the patient should be preoxygenated with a fractional inspired oxygen concentration of 1.0. A further bolus dose of NMBD may be indicated prior to skin incision, with anaesthesia ideally maintained with a TIVA technique. High fresh gas flows and pressure-controlled ventilation can be helpful whilst the nasotracheal tube cuff is deflated and the tube is partially withdrawn, as the tracheostomy tube is inserted. Correct tube position must be confirmed with continuous waveform capnography, after which lower gas flows and a lower fractional inspired oxygen concentration can be resumed. Clear communication between all multidisciplinary team members is crucial to safe and successful completion of this high-risk surgical procedure.

After tracheostomy insertion, it is rarely necessary to administer further bolus doses of NMBD. Anaesthesia can be maintained with TIVA, or switched to a volatile technique (as no further interruptions to continuous delivery of inhalational agent are generally required).

Any necessary dental extractions are also performed at this juncture, usually following administration of local anaesthetic containing adrenaline (to reduce intraoral bleeding). Nonetheless, the dental extractions may be associated with significant surgical stimulus/sympathetic response, that can be attenuated by appropriate remifentanil titration.

Following PEG and tracheostomy insertion, and dental extractions, the patient usually undergoes further surgical antiseptic skin preparation and re-draping prior to commencing the cancer resection. This next operative stage is prolonged; therefore, it is essential that the patient is positioned carefully on the operating table, with all vulnerable pressure areas and peripheral nerves padded and protected. A pillow should be placed under the patient’s knees to relieve hip hyperextension, and gel pads should be applied under the elbows and heels. Breathing circuit and monitoring cables (and their connections) should be checked and meticulously positioned to avoid patient compression injuries.

Cancer resection, neck dissection, and raising the free flap

Where feasible, it is advantageous to have two surgical teams operating simultaneously to minimise surgical and anaesthetic time (and the associated sequelae), with one raising the free flap from the donor site while the other proceeds with the surgical resection and neck dissection.

There are several free flap options available, depending upon the requirement for soft tissue graft only, or additional bone graft. The types of graft most commonly encountered in these patients are radial forearm, anterolateral thigh, deep circumflex iliac artery (DCIA), fibula, and scapula. The defect to be repaired dictates the type of flap required. Closure of the wound at the donor site may sometimes necessitate an additional skin graft taken from another site, such as the abdomen.

Maximizing surgical access to the donor site is an important consideration in the positioning of the patient, while also being mindful of minimising the risk to any pressure areas. If the scapula is used as the donor site, the patient must be turned into a lateral position, then returned to the supine position during the surgical procedure. This requires additional personnel in the operating theatre to facilitate this positional change safely, during which the entire multidisciplinary team must be careful to ensure that the surgical site and any patient monitoring is not compromised.

Microvascular anastomosis

Regardless of the chosen donor site, the principles of management to maximize flap perfusion and anastomosis viability remain the same: maintenance of normothermia; optimisation of blood pressure (flow to the flap); optimisation of haematocrit to promote perfusion (19); adequate oxygenation; and careful titration of fluid (to avoid tissue oedema and flap congestion).

The flap should be normothermic before it is raised (prior to commencement of “warm ischaemia” time). Once the free flap is raised and its blood supply interrupted, the time-critical microanastomosis procedure must be undertaken. The type of flap has some influence on its relative resistance to “warm ischaemia”—flaps containing more muscle (with higher metabolism), respond less well to prolonged ischaemia. This phase of microsurgery is usually associated with reduced surgical stimulus (unless another site is being operating on simultaneously), providing the anaesthetist with the opportunity to optimise physiological conditions in preparation for graft reperfusion.

Optimising free flap reperfusion

The ideal physiological conditions to optimize perfusion of the newly anastomosed flap include normothermia, a relatively hyperdynamic circulation with a wide pulse pressure, and a haematocrit in the range of 30–35%—reducing blood viscosity to optimise flow, without compromising oxygen carrying capacity, taking into account patients’ comorbidities.

Hypothermia causes vasoconstriction, which is undesirable prior to raising of the flap and also following anastomosis, as this causes reduced blood flow within it. Free flaps are denervated and lack the normal autonomic regulatory mechanisms that influence blood flow (via changes in blood vessel calibre), such that they are reliant upon adequate systemic blood pressure for perfusion. Consequently, at the point of flap reperfusion, the patients’ blood pressure should be maintained at their baseline level. Indeed, depending upon the number, size and anatomy of the anastomosed arteries, it may be necessary to maintain a supra-normal perfusion pressure. The potential disadvantages of an artificially high blood pressure are increased bleeding within the resection bed and at the anastomosis, which may lead to haematoma formation, wound break down, and crucially, flap compromise. Blood pressure should be optimised by a combination of careful intravenous fluid administration (optimise preload) and judicious use of vasopressors (optimise afterload). However, it should be noted that the direct action of vasopressors on arteries and arterioles supplying (and within) the flap can potentially have the opposite effect. Similarly, venous constriction of anastomosed veins or venules within the flap can cause venous congestion and reduce flap perfusion. This resistance to flap outflow can increase interstitial oedema, compounding any venous congestion, which in turn may be exacerbated by overzealous intravenous fluid administration (particularly in the absence of lymphatic drainage from free flaps). Consequently, a careful goal-directed fluid strategy is essential. Continuous oesophageal doppler monitoring is generally precluded due to the site of surgery, and central venous catheters are rarely required routinely, such that arterial pulsed contour analysis is often the most suitable mode of monitoring trends (pulse pressure variation, stroke volume variation etc.)—because these are not calibrated, they are less accurate for absolute measurements. As ever, clear communication between anaesthetic and surgical teams is vital in optimising flap perfusion.

Flap monitoring

One method commonly employed to improve flap survival is to directly assess blood flow within the flap arterial supply. This allows immediate recognition of compromised blood flow, so early restorative actions can be taken—which might entail urgent return to theatre. An implantable doppler device can be placed after anastomosis to allow assessment of both quality and character of arterial and venous blood flow. These have been shown to be superior to using clinical assessment alone in monitoring the health of flap perfusion in the early postoperative period (20). Clinical assessment involves assessing the flap for colour, temperature, capillary refill and bleeding.

Flap blood flow may also be imaged intraoperatively once the flap has been raised, using indocyanine green near-infrared video angiography (ICG-NIR-VA). This technique is used to assess the quality of flap perfusion and “run off” before the flap removal. Intravenous ICG is administered by the anaesthetist (after appropriate reconstitution, as per manufacturer’s instructions), though care should be taken to avoid administration in patients with a previous history of adverse reactions to ICG or iodine, and it should be noted that patients’ urine may appear green in colour afterwards.

Intraoperative management principles

Management of comorbidities

The advanced age and comorbidities typical of this patient cohort requires special attention both preoperatively (assessment of severity and optimisation) and intraoperatively (ongoing management). Perioperative hypotension is common and is associated with organ injury and POCD (21). Patients with a history of cognitive impairment, cardio- and cerebrovascular disease are particularly vulnerable to episodes of hypotension and as such, the usual thresholds for intervention (e.g., vasopressor administration) should be adjusted to the individual patient, with optimisation of cardiovascular parameters throughout the procedure and not just at the time of flap anastomosis.

Coexistent diabetes requires a proactive approach and regular monitoring of intraoperative blood glucose. Those with a preoperative insulin requirement invariably require exogenous insulin administration intraoperatively to maintain blood glucose within an acceptable range, as per local policy. Meticulous attention should be paid to avoiding both hypo- and hyperglycaemia perioperatively.

Fluid therapy

Fluid balance should aim to take account of preoperative fasting deficits, as well as intraoperative blood loss and insensible losses. After an initial conservative loading dose of isotonic crystalloid fluid, a judicious fluid administration policy is recommended (as discussed earlier, liberal fluid administration is associated with oedema formation and flap congestion)—guided by cardiovascular parameters, blood gas analysis and urine output (though the latter can often be unreliable).

Analgesia

Analgesia is often a concern for this group of patients preoperatively and the planned postoperative regimen should be discussed with them at the preoperative assessment. Remifentanil infusion is the mainstay of intraoperative analgesia and titrated to surgical stimulus and the phase of surgery (regardless of whether a volatile or TIVA technique is utilised). Loading with a longer acting opioid should be undertaken at the end of surgery, due to remifentanil’s relatively context insensitive half-life. Multimodal analgesia is advocated, with the use of intraoperative paracetamol, augmented by local anaesthesia, where possible. Opioid patient-controlled analgesia provides the mainstay of postoperative analgesia for patients undergoing major oral cancer resection and free flap reconstructive procedures, with the main source of pain often the flap donor site.

Regional anaesthesia

Major oral cancer surgery is less amenable to targeted nerve blocks (aside from the inferior alveolar nerve block for dental extractions) due to the anatomical route and variable distribution of the cranial nerves supplying the head and neck tissues. A nerve block performed at the start of these prolonged procedures is unlikely to provide much postoperative benefit. Nevertheless, the head and neck region is well suited to local anaesthetic field blocks (subcutaneous or submucosal infiltration) which can have beneficial intraoperative effects in reducing general anaesthetic agent (reducing POCD) and opioid requirements. A superficial or deep cervical plexus block may be performed for patients undergoing neck dissection, though surgeons often prefer to infiltrate large volumes of low concentration local anaesthetic mixed with adrenaline instead (for its beneficial vasoconstrictive effects in reducing surgical site bleeding). There is no high-quality evidence confirming a beneficial effect of regional anaesthesia on cancer recurrence.

Regional anaesthesia may confer potential analgesic benefit for managing postoperative pain arising from the free flap donor site, with nerve blocks performed at completion of surgery. Alternatively, continuous infusions of local anaesthetic can be employed in the early postoperative period, delivered via catheters placed within the graft donor site under direct vision, prior to wound closure. An initial loading dose of local anaesthetic agent should be administered at the end of surgery, followed by a continuous infusion postoperatively, using a pre-programmed infusion.

Temperature monitoring

As discussed earlier, continuous temperature monitoring is essential, and patients should be kept normothermic throughout (to optimise the function of all organ systems and processes), but crucially, to also promote flap survival. This also includes prevention of hyperthermia (necessitating cessation of active warming measures).

Positioning and pressure areas

As discussed earlier, meticulous care must be taken with patient positioning on the operating table, and protection of pressure areas with padding to prevent peripheral nerve injuries and pressure sores during prolonged surgical procedures. Coexistent diabetes and poor preoperative nutritional status may increase these risks.

Ancillary medications

During major oral cancer surgery, it is common practice to administer dexamethasone (to reduce postoperative oedema) and antimicrobials (surgical prophylaxis) at regular intervals. These continue postoperatively, with the duration of prescription varying between institutions.

Multidisciplinary team

Due to the lengthy and demanding nature of these procedures, ensuring adequate comfort breaks for surgical, anaesthetic and nursing staff is essential in optimising team performance. Good communication is essential between the multidisciplinary team during all phases of surgery and anaesthesia due to the complex nature of these shared airway cases, but especially if there is change of personnel during the procedure.

Postoperative transfer and handover

There is significant institutional variation as to the nature of the postoperative care facility to which these patients are transferred, dependent upon staff numbers, training and availability of the appropriate level of monitoring of physiological parameters. Patients may be transferred initially to a post-anaesthesia care unit (PACU) or directly to ICU, a high dependency unit or dedicated head and neck surgical ward (including those patients with tracheostomies), with no demonstrable difference in patient outcomes.

For patient transfers between clinical areas, standard monitoring should include capnography and emergency equipment should be immediately available. Specifically, this should include a dedicated “tracheostomy box” for tracheostomised patients, which should accompany these patients at all times (until successful decannulation), as per guidance from the UK National Tracheostomy Safety Project (22). This box contains essential equipment required to manage any tracheostomy emergency including appropriately sized spare tubes, suction catheters etc. Additionally, a bed-head sign should also be placed at the patient’s bedside, that includes information regarding the tracheostomy type, date of insertion, model, size and the presence of any inner cannula or stay sutures.

Communication to the postoperative care team should be both verbal and written, with minimum information including the patient’s pathology, surgical procedure, comorbidities, relevant intraoperative care, and instructions for ongoing care (for more details, please see the dedicated article on “Postoperative considerations in oral cancer patients after major surgery” in the series on anaesthesia for oral cancer).

Strengths and limitations

This is a conventional (traditional) review, and is not a narrative or systematic review. There is no nationally or internationally agreed consensus on best care for this group of patients, and we have attempted to address that gap with this article, and provide realistic recommendations to those caring for this patient population. This has been based on the most up to date literature and best available evidence relating to major cancer resection and free flap reconstruction for oral surgery. We acknowledge that while there are some small studies relating to care of head and neck patients undergoing free flap reconstruction, there are limited studies specifically related to either the patient population with oral cancer, or the recommended anaesthetic technique. There are limited numbers of large randomised controlled trials in head and neck surgery on the whole.

Conclusions

Summary of key recommendations

These patients should have a detailed preoperative assessment and airway management strategy decided. Intraoperative monitoring should be undertaken with routine Association of Anaesthetists monitoring, an arterial line, urinary catheter, and temperature probe. pEEG monitoring may be considered, particularly where TIVA is being used. Standard VTE prophylaxis should be applied.

Airway management will be guided by preoperative assessment. Either TIVA or volatile anaesthetic techniques may be utilised. However, it may be preferable to start with a TIVA technique if the patient is to undergo a tracheostomy. Elective surgical tracheostomy may be undertaken in patients more likely to suffer from postoperative swelling. PEG insertion may be considered where patients are likely to need a prolonged postoperative period of supplemental nutrition.

The type of free flap chosen for reconstruction will be dictated by the site of the cancer and the defect to be repaired. The principles of management to maximize flap perfusion and anastomosis viability remain the same: maintenance of normothermia, optimisation of blood pressure (flow to the flap), optimisation of haematocrit to promote perfusion, adequate oxygenation, and careful titration of fluid (to avoid tissue oedema and flap congestion). Intraoperative flap monitoring may include ICG-NIR-VA. Postoperative monitoring may include an implantable doppler probe in addition to clinical assessment.

General principles of intraoperative care are management of comorbidities, judicious fluid administration, temperature maintenance, and careful patient positioning. Administration of analgesia and ancillary medications such as antibiotics and dexamethasone should be undertaken. The type of ward where the patient is cared for postoperatively should be dictated by local institutional policy. Good communication between all members of the multidisciplicary team is essential at all stages of patient care.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editors (Patrick Ward and Michael Irwin) for the series “Anaesthesia for Oral Cancer” published in Journal of Oral and Maxillofacial Anesthesia. The article has undergone external peer review.

Peer Review File: Available at https://joma.amegroups.org/article/view/10.21037/joma-22-35/prf

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://joma.amegroups.org/article/view/10.21037/joma-22-35/coif). The series “Anaesthesia for Oral Cancer” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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