Microvascular Free Tissue Transfer in Head and Neck Cancer – Can Anaesthesia Management Improve Outcome?

INTRODUCTION Microvascular free tissue transfer is the cornerstone of head and neck cancer (HNC) surgery. The traditional view has been that flap outcome is squarely the domain of the surgeon. This editorial argues that meticulous attention to Airway, Analgesia, Arterial and venous flow, Anaesthesia technique, Advances and Artificial intelligence can minimise morbidity, enhance flap survival and shorten length of stay. Key anaesthetic considerations, current evidence and best practices are summarised here to support this point of view. Comorbidities invariably impact the course of anaesthesia and hospital stay. In the specific context of microvascular procedures in head and neck, coronary artery disease, peripheral vascular disease, anaemia (haemoglobin 70 mmHg), pulse rate and low normal blood viscosity. Noxious stimulus is low as the flap is insensate. Furthermore, by this stage, the anaesthetic agents have been administered for some hours. As a result, blood pressure may be low despite minimal levels of general anaesthetic. The dose of anaesthetic agent needs to be balanced with intravenous fluids to maintain a high normal blood pressure to increase flow. Vasoconstriction (due to hypothermia, catecholamines and drugs) will decrease vessel radius and compromise flow (Hagen-Poiseuille’s law). Fluid management has evolved from maintaining a high urine output (1.0–2 mL/kg/hour) to goal-directed fluid therapy (stroke volume variation or pulse pressure variation or non-invasive cardiac output and oesophageal Doppler),[13,14] normal serum lactate and urine output 0.5 mL/h. Restrictive strategy can lead to hypotension and compromise flow in the flap. Excessive fluids can compromise the circulation in the anastomosed vessels because of interstitial oedema. Goal-directed Fluid therapy (GDFT) can achieve the balance between liberal fluid versus restricted fluids and decrease perioperative risk and intensive care unit stay.[15] Expert consensus recommends the standard American Society of Anesthesiologists monitoring and invasive arterial monitoring in selected cases.[4] The use of vasopressors has historically been a contentious issue. However, multiple studies have established that vasopressors are in fact associated with less total flap failure and pedicle thrombosis.[12] Hypothermia is likely due to prolonged surgery, multiple incisions and fluids. This can impair flow by impacting blood viscosity, haematocrit, coagulation profiles and may lead to infection. On recovery, shivering increases oxygen consumption and can result in hypoxia, myocardial events and arrhythmias. Secondary ischaemia can be limited by preventing interstitial oedema, venous congestion (due to haematoma) or thrombosis. Acute flap-related complications usually present in the first 24–48 h after surgery.[18] Overall complications, airway complications and length of stay were significantly lower in the Nasotracheal intubation (NTI) group[17] compared to tracheostomy [Table 3]. Table 5 compiles practical considerations based on experience in a high-volume centre. We conducted 678 such surgeries in 2024 (unpublished data).Table 5: Practical considerations from a high-volume centreThere are several unanswered questions. The field is ripe for studies on donor site pain, regional anaesthesia techniques, safety of dexmedetomidine, ideal vasopressor protocol, enhanced recovery after surgery in the Indian context, post-operative sedation regimes, acute withdrawal of ‘gutkha’ and the use of AI for prediction, risk stratification and goal-directed therapy. CONCLUSION Tumour excision and microsurgical procedures mandate finely tuned protocols to minimise primary, secondary ischaemia and reperfusion injury, thereby optimising flap viability. The outcome of microvascular free tissue transfer in HNC surgery primarily depends on surgical technique. Anaesthetic management plays a crucial role in monitoring, preventing and addressing hypovolemia, hypotension (drug-induced), hypothermia, vasoconstriction (respiratory alkalosis, pain and hypothermia) and mechanical compression of the anastomosis (positioning and fluid overload). Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Presentation at conferences/CMEs and abstract publication Nil. Study data availability Nil. Disclosure of use of artificial intelligence (AI)-assistive or generative tools The authors confirm that no AI tools or language models (LLMs) were used in the writing or editing of the manuscript, and no images were manipulated using AI. Declaration of use of permitted tools No copyrighted scales, scores or figures have been used to be mentioned by the authors, if not from the above options. Authors contributions ASKJ: Concept, Definition of intellectual content, literature search, manuscript preparation, editing, review. AD: Concept, Definition of intellectual content, literature search, manuscript preparation.