Reconstructive surgery
Anaesthesia for plastic and reconstructive surgery

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Abstract

Plastic and reconstructive surgery aims to restore normal and functional anatomy following tissue destruction or impaired wound healing. The techniques required depend on the complexity of the wound, from simple closure to flap reconstruction. More complicated wounds with large skin defects may need free flap transfer for optimal functional and cosmetic results. Flap failure is a major potential complication and perioperative anaesthetic management plays an important role in successful surgery. Factors which may lead to vasoconstriction must be avoided, including pain, hypothermia and hypovolaemia. Blood flow is also improved by maintaining an adequate blood pressure, moderate haemodilution and normocarbia. Free flap failure occurs mainly during the first three postoperative days. Venous thrombosis secondary to congestion is more common than arterial obstruction. Prompt surgical re-exploration is the key to flap salvage.

Introduction

Plastic and reconstructive surgery aims to restore normal and functional anatomy following tissue destruction or impaired wound healing. The abnormality could be congenital, traumatic or as a result of a disease process such as cancer or infection.

In considering how to close a surgical wound, the plastic surgeon can ascend the ‘reconstructive ladder’ (Box 1), starting from the simplest option and ascending to a more advanced one depending on the complexity of the surgical wound and the clinical conditions.

The lower rungs of the ladder have limited implications for anaesthesia, and many simple elective plastic surgery procedures can be done in an office setting under local anaesthesia with little or no sedation. Strategies higher up the ladder require more intervention, in particular split skin grafts require good pain management for the donor site, preferably using regional anaesthesia, for example a lateral cutaneous nerve block in for the lateral thigh, from where split skin grafts are frequently harvested.

If there are no options for local wound cover, tissue can be harvested from elsewhere in the body, a technique known as a free flap transfer. Any tissue that can be isolated with a suitable vascular pedicle can be used, and this may include skin, fascia, fat, muscle, nerve, and bone. It offers the best functional and cosmetic results, but it also bears a higher risk of flap failure. Complications can arise due to primary ischaemia at the time of surgery, reperfusion injury or impaired postoperative blood flow causing secondary ischaemia.

Intraoperative and postoperative airway management can also be a concern in reconstructive ear–nose–throat and maxillofacial surgery. In the presence of an upper airway lesion, the anatomy could be distorted and increase the risk of a difficult airway. An airway management plan should be formulated with back-up plans in place. Often the plan may include awake fibreoptic intubation or even elective tracheostomy. Likewise the same attention to detail should be directed to extubation and the possibility of elective postoperative ventilation, particularly in the presence of oedema or intermaxillary fixation.1 This should be well communicated with the patient and other members in the operating team.

Section snippets

Preoperative assessment

Perioperative medical complications increase the economic costs of microsurgery more than surgical complications. This highlights the importance of careful preoperative assessment, especially for free flap transfer, where the operating time can be prolonged (e.g. >6 hours).

Both high American Society of Anesthesiologists (ASA) grading and advanced Charlson grade have been reported as predictors of postoperative medical complications. Age alone is not an independent risk factor for postoperative

Physiology of blood flow to free flap

If the flow in a blood vessel is laminar, the flow can be predicted by the Hagen–Poiseuille equation, which states that flow is directly proportional to the pressure difference (ΔP), and the fourth power of the radius (r), and is inversely proportional to the length of the vessel (L) and the dynamic viscosity (μ).Blood flow=Δr48μL

The systemic blood pressure is the main driving force for blood flow through the flap, therefore the adapted mean arterial pressure for the patient should be

Perioperative management for free flap surgery (Table 1)

The perioperative care goal should be to improve free flap survival and prevent of complications. The exposed skin area can be large as multiple surgical sites may be involved. This, compounded with the loss of thermoregulation after induction, and an increase in evaporative water loss from the surgical field, can lead to the rapid development of hypothermia. The importance of normothermia in promoting free flap blood flow mandates the use of body temperature monitoring. Active warming device

Fluid therapy and free flap surgery

A free flap initially is devoid of lymphatic drainage, and thus is highly susceptible to tissue oedema, which could predispose to venous thrombosis and flap failure. In addition the free flap capillary endothelium is likely damaged leading to increased vascular permeability. High-volume crystalloid fluid administration has been shown to be an independent risk factor for increased flap oedema and thrombosis due to a pro-coagulant effect.7 When crystalloids are administered rapidly, the mechanism

Postoperative care

The general principle of good postoperative care applies. These include maintaining normothermia, normal blood pressure, a haematocrit of 25–30%, satisfactory urine output, and good pain control.

In particular, shivering should be avoided, as it can increase myocardial oxygen consumption and can cause peripheral vasoconstriction. External warming, pethidine, alpha-2 agonists or sedation may be required to stop shivering.

Excellent analgesia is required to prevent the release of catecholamines and

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