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Anaesthesia for free flap breast reconstruction

2015; Elsevier BV; Volume: 16; Issue: 5 Linguagem: Inglês

10.1093/bjaed/mkv036

2058-5357

N Nimalan, Olivier A. Branford, Gary M. Stocks,

Anesthesia and Pain Management

Key points•Deep inferior epigastric perforator free flap is considered the gold standard in free flap breast reconstruction.•Appropriate patient selection is a predictor of good clinical outcome in microsurgery.•Provision of a full hyperdynamic circulation and maintenance of a normal body temperature helps to optimize flap perfusion.•Careful positioning of the patient is imperative for long procedures to prevent peripheral nerve damage and pressure sores.•Changes to clinical free flap perfusion need to be recognized quickly and managed appropriately—early detection remains the most important factor in the salvage of free flaps. •Deep inferior epigastric perforator free flap is considered the gold standard in free flap breast reconstruction.•Appropriate patient selection is a predictor of good clinical outcome in microsurgery.•Provision of a full hyperdynamic circulation and maintenance of a normal body temperature helps to optimize flap perfusion.•Careful positioning of the patient is imperative for long procedures to prevent peripheral nerve damage and pressure sores.•Changes to clinical free flap perfusion need to be recognized quickly and managed appropriately—early detection remains the most important factor in the salvage of free flaps. In the UK, all patients undergoing mastectomy should be offered breast reconstruction surgery either at the time of the mastectomy or as a delayed procedure.1National Collaborating Centre for CancerEarly and Locally Advanced Breast Cancer: Diagnosis and Treatment. NICE Clinical Guideline 80. National Institute for Health and Clinical Excellence, London, UK2009Google Scholar There are several options for breast reconstruction, which can be broadly divided into implant-based or autologous flap reconstruction using the patient's own tissue. Implant-based reconstruction often involves the use of saline tissue expanders initially which usually require replacement with a definitive silicone implant. Autologous flap surgery uses a combination of skin, fat, and sometimes part of the underlying muscle. The flap is moved from areas such as the abdomen, upper back, inner thigh, upper hip, or buttocks to the chest where it is shaped into a new breast. For implant-based reconstruction, 34% of patients suffer complications such as capsular contracture or a foreign body scarring reaction, that requires them to have further surgery within 5 yr.2Gabriel SE Woods JE O'Fallon WME et al.Complications leading to surgery after breast implantation.N Engl J Med. 1997; 336: 677-682Crossref PubMed Scopus (342) Google Scholar Although autologous flap reconstruction involves a longer duration of initial surgery, when compared with implant-based reconstruction, it may be associated with a reduced number of operations, lower complication rates, and it is often easier to achieve a more natural aesthetic appearance. Autologous flaps can be pedicled or free. The most common example of the former is the latissimus dorsi flap, where donor tissue remains connected to the original donor site via an intact vascular pedicle, and is moved into the breast defect through the axilla. In contrast, free flaps are completely detached from the body with division of the vascular pedicle, and then the blood supply is reestablished using microvascular surgery techniques. The two most common free flap procedures for breast reconstruction are the transverse rectus abdominis myocutaneous (TRAM) free flap and the deep inferior epigastric perforator (DIEP) free flap. These procedures harvest an ellipse of lower abdominal tissue and the flap is then transferred to the chest. Unlike the TRAM flap, the DIEP procedure spares the rectus abdominis muscle which helps to preserve abdominal strength, halving the likelihood of a bulge or hernia and shortens recovery time. Because of this, the DIEP flap is now considered the gold standard for free flap breast reconstruction and will be the main focus of this article. Owing to the requirement for microvascular surgery, DIEP reconstruction is carried out in specialist regional plastic surgery centres. DIEP flap breast reconstruction involves three main stages: Raising of the flap with dissection through the rectus abdominis muscle to meticulously separate out the small perforator vessels originating from the deep inferior epigastric artery (Fig. 1).Microvascular anastomosis to the internal mammary artery and vein in the chest.Insetting of the flap and shaping of the transferred tissue. These are two separate phases of surgery which can affect the viability of the free flap. Primary ischaemia of the flap occurs as blood flow ceases during flap transfer which induces anaerobic cellular metabolism. This leads to an increasing lactate, a decrease in intracellular pH with increasing calcium and pro-inflammatory mediator levels. The severity of the damage caused by primary ischaemia is proportional to the duration of ischaemia. The oxygen consumption of skin is five times lower than that of muscle at rest (0.2 and 1 ml min−1 per 100 g of tissue, respectively). Consequently TRAM flaps, which include skeletal muscle, are more sensitive to ischaemia than DIEP flaps. Reperfusion is the second important phase in free flap surgery and begins with vessel declamping after completion of microvascular anastomosis. Typically, blood flow restoration reverses the physiological transient changes triggered by primary ischaemia. However, an ischaemia/reperfusion injury may occur if some factors are not favourable, such as prolonged ischaemia or inadequate perfusion pressure. In this case, reperfusion injury occurs when blood flow allows the influx of inflammatory substances that may ultimately cause flap compromise.3Quinlan J Lodi O Anaesthesia for reconstructive free flap surgery.Anaesth Intensive Care Med. 2006; 7: 31-35Abstract Full Text PDF Scopus (16) Google Scholar Blood flow through the microcirculation is crucial to the viability of a free flap. The microcirculation is a series of successive branches of arterioles, capillaries, and venules from the central vessels. Regulation of blood flow and oxygen delivery is accomplished by these three functionally distinct portions of the microcirculation. Dissected vascular tissue is denervated and therefore loses intrinsic sympathetic tone. However, the feeding artery and draining vein at the recipient site still respond to physical, humoral, and chemical stimuli such as cold, circulating catecholamines, and pharmacological agents. The absence of intact lymphatic drainage increases the risk of interstitial oedema. The importance of appropriate patient selection is a well-known predictor of good outcome in microsurgery. As a result, most of the women presenting for DIEP reconstruction are fit and well apart from their breast cancer. Advanced age alone is not a contraindication to surgery as long as co-morbidities and general health allow the patient to undergo long and extensive surgery. Although smoking is not a contraindication, smokers are advised to stop smoking for at least 4 weeks before surgery. Nicotine-induced vasoconstriction, carbon monoxide-related tissue hypoxia, and blood hypercoagulability caused by increased platelet aggregation can cause problems with breast skin flap vascularity and donor site morbidity.4Chang DW Reece GP Wang B et al.Effect of smoking on complications in patients undergoing free TRAM flap breast reconstruction.Plast Reconstr Surg. 2000; 105: 2374-2380Crossref PubMed Scopus (309) Google Scholar Similarly, obese patients may be advised on weight reduction methods before surgery to improve surgical outcome. Absolute contra-indications to surgery are hypercoagulable states, such as sickle cell anaemia and polycythaemia, which greatly increase the risk of anastomotic thrombosis. A thorough assessment is essential before anaesthesia, and should follow general principles, including adequate planning of anaesthesia and postoperative care. There are surprisingly few good randomized controlled trials regarding the best anaesthetic management for patients undergoing free flap surgery. However, a good understanding of the physiology of blood flow both in the systemic circulation and through the free flap will help to make sensible management decisions. Survival of the free flap depends on an adequate blood flow and although blood is not a Newtonian fluid and the vessels are not rigid, the Hagen–Pouiselle equation includes a number of parameters which are amenable to manipulation to improve flap survival. Bloodflow = π8ΔPμr4l Although the length (l) is fixed, manipulating pressure gradient (ΔP) across transplanted tissue (systemic arterial pressure minus venous pressure), vessel radius (r), and blood viscosity (µ) can all dramatically improve flow through the flap. The pressure gradient is primarily a function of the systolic arterial pressure which should be adequate to maintain perfusion. Equally important however is the calibre of the blood vessel. Ensuring that the patient is warm and normovolaemic will result in vasodilatation, a low systemic vascular resistance and good peripheral perfusion both to the free flap and the rest of the patient. Traditional teaching recommends that good flap perfusion will be assured if systolic arterial pressure remains within or above the patients' physiological range. However, for breast free flap surgery, it is noteworthy that the flap is anastomosed to the internal mammary artery, which due to its proximity to the heart will have an excellent perfusion pressure. If a low systemic vascular resistance is achieved then flow can occur through the free flap even if the systolic arterial pressure is below normal. Furthermore, over-zealous fluid administration in an attempt to achieve a supra-normal arterial pressure target is not recommended as this will only result in interstitial oedema, compromising blood flow and gas exchange at the level of the microcirculation. Avoiding hypovolaemia, vasoconstriction, and hypothermia are vital to prevent flap compromise or failure. Owing to the long duration of surgery, patients are intubated and ventilated. Venous access should be gained with a large gauge peripheral line on the opposite side to surgery as many women will have undergone axillary lymph node sampling or clearance. In women who have undergone chemotherapy, this can be challenging and central venous access may be required. In addition, an arterial line, urinary catheter, and core temperature probe are recommended. Monitoring of fluid requirements can also be achieved using a central venous catheter, but increasingly this can be avoided by the use of some form of cardiac output monitoring and goal-directed fluid therapy, such as an oesophageal Doppler monitor (ODM). The duration of surgery may be >8 h. Anaesthesia can be maintained using a volatile anaesthetic in oxygen-enriched air or a propofol infusion. In our centre, desflurane is used because of its quick offset; however, isoflurane and sevoflurane offer their own advantages. Isoflurane maintains microcirculatory flow and sevoflurane may attenuate ischaemic–reperfusion injury. More research is required to assess the effects of desflurane on the microcirculation. Although a total i.v. anaesthetic technique offers the advantages of reduced postoperative nausea and vomiting and a smoother recovery profile, emergence can be prolonged after a long infusion. When using a propofol infusion, an appropriate depth of anaesthesia monitor is recommended. Both techniques can be combined with either a remifentanil infusion or intermittent fentanyl boluses. Remifentanil offers excellent intraoperative analgesia, rapid control of arterial pressure, marked vasodilation, and negates the use of a neuromuscular blocking agent. Adequate ventilation to ensure normal arterial Po2 and Pco2 is essential. Hypoxia will produce catecholamine release and vasoconstriction. Hypocapnia will also lead to vasoconstriction, and hypercapnia can cause sympathetic nervous system stimulation. Careful positioning of the patient is imperative to avoid the well-recognized problems of peripheral nerve damage and pressure sores. Patients lie supine with arms abducted (crucifix position) and care should be taken to ensure abduction is <90° to prevent brachial plexus injury. Forearms should be in a neutral position to prevent ulnar nerve injury and the arms fixed into position with ties to allow the patient to be sat up intraoperatively to assess for symmetry. Heel pads are used to prevent pressure sores and pillows placed under the knees to stop painful hyperextension. Surgery can last between 6 and 10 h and patients are at risk of stiff, painful joints after operation. It is advisable, if possible, to passively move joints throughout the procedure and at the end of surgery, to help reduce joint pain and stiffness. Preventing hypothermia is a key component to ensuring adequate conditions for flap perfusion. Large tissue areas are exposed for prolonged periods of time. In addition, induction of anaesthesia leads to redistribution of blood and equilibration of core and peripheral temperature. This is because inhalation agents and opioids reduce the threshold for vasoconstriction by 2–3°C and promote heat loss by vasodilation. If no effort is made to maintain temperature, patients undergo a significant temperature decline over the course of a long procedure. Forced air-warming devices should be used to maintain normothermia. A surgical access type blanket can be used, but sometimes the opening of the blanket is not large enough to allow access to both the surgical sites of the lower abdomen and the upper chest. We recommend using an underbody warming blanket which overcomes this problem and also allows active warming to begin in the anaesthetic room before induction, while monitoring is established. In addition, the operating theatre should have an adequate ambient temperature, and warm i.v. fluids and humidified gases used to prevent hypothermia. The appropriate haematocrit is an optimum balance between viscosity, blood flow, and adequate oxygen-carrying capacity and is thought to be in the region of 30–35%. Maintaining normovolaemia during haemodilution allows a decrease in viscosity, associated decrease in peripheral vascular resistance, increase in cardiac output, and improved tissue blood flow. Transfusion is rarely required for a single delayed reconstruction but may be needed in individuals undergoing mastectomy with immediate reconstruction, particularly those undergoing bilateral reconstruction. A hyperdynamic circulation with a high cardiac output, peripheral vasodilation, and a large pulse pressure is the ideal to maintain adequate microcirculatory perfusion. In microvascular surgery, a decrease in cardiac output is mainly due to a reduction in preload, either from loss of circulating volume or from pharmacological vasodilation. Any reduction in cardiac output induces vasoconstriction mediated by the sympathetic nervous system, renin–angiotensin aldosterone, and baroreceptor reflex. Therefore, maintenance of an appropriate cardiac output is important for free flap surgery. While the traditional approach was for aggressive fluid therapy, our experience in free flap breast surgery suggests this is not necessary, as fluid losses are not great and due to the proximity of the internal mammary artery to the heart, there is excellent perfusion. Our recommendation is to use goal-directed fluid therapy and our practice is to use an ODM to guide administration of crystalloid and colloid fluids, by monitoring the effect of fluid boluses on stroke volume. A recent trial compared ODM with central venous catheters in free flap perforator surgery. A total of 104 patients were randomized to one of the two groups to receive 250 ml of balanced starch solution titrated against stoke volume increase (ODM group) or sustained right atrial pressure 12–15 cm H2O (CVP group). Additionally, they received 1–2 litres of crystalloid solution to replace fluid losses. The Doppler group showed reduced anaesthetic time, although operative time was not significantly different between the groups. There were no probe-related complications in the oesophageal Doppler group; however, in the CVP group, six patients suffered complications related to insertion of the central venous catheter. One patient suffered an iatrogenic Horners syndrome and five patients suffered symptomatic haematomas at the site of insertion. Overall fluid input was not different, but patients in the CVP group had a smaller fluid output (blood loss, urine, etc.) and were in greater positive fluid balance compared with the oesophageal Doppler group. In addition, the patients in the Doppler group spent a mean of 1.9 days less in hospital compared with the other group. There was no difference in core temperature or flap complications between the groups.5Figus A Wade RG Oakley S et al.Intraoperative esophageal Doppler haemodynamic monitoring in free flap perforator surgery.Ann Plast Surg. 2013; 70: 301-307PubMed Google Scholar During the dissection stages of surgery, controlled hypotension may be requested. This is usually achieved by altering vapour±propofol/remifentanil concentrations. Vasodilators are generally avoided as they may be harmful due to the risk of blood flow steal away from the flap. During anastomosis of the flap, normotension is usually sufficient to ensure an adequate perfusion pressure through the tissue. The use of vasoconstrictors is a contentious issue in free flap anaesthesia, largely over fears that systemic vasoconstriction leads to reduced flap perfusion. However, there are very few good quality studies that support this and only a few vasoconstrictors have been studied in this context. A recent retrospective study of over 250 microsurgical breast reconstructions examined intraoperative phenylephrine±ephedrine use and concluded that vasopressor use did not adversely affect outcome.6Chen C Nguyen MD Bar Meir E et al.Effects of vasopressor administration on outcomes of microsurgical breast reconstruction.Ann Plast Surg. 2010; 65: 28-31Crossref PubMed Scopus (63) Google Scholar Further studies are needed to fully evaluate and compare the effect of different vasopressors on the free flap microcirculation. However, the use of phenylephrine and ephedrine to maintain normotension in adequately filled patiently appears safe. Deep venous thrombosis is a risk in prolonged surgery. Anti-embolism stockings and cyclically inflating anti-embolism leggings are used, as is prophylactic subcutaneous heparin which also improves flap survival. Coughing and retching increase venous pressure and reduce flap flow; therefore, smooth emergence and extubation is desirable. Techniques to smooth extubation include the use of a low-dose remifentanil infusion to aid tube tolerance, deep extubation, or exchanging the tracheal tube for a supra-glottic airway device. Patients undergoing DIEP reconstruction have two operative sites—the chest and the lower abdomen. Compared with mastectomy alone, free flap breast reconstruction is thought to be less painful as the flap is insensate and its use for wound closure avoids excess skin stretching. Therefore, the chest wound is usually less painful than the abdomen incision. While systemic analgesics are usually sufficient to treat pain, transverse abdominal plane blocks have been shown to reduce postoperative opioid requirement up to 48 h. They can be placed by the anaesthetist at induction under ultrasound guidance or by the surgeons under direct vision.7Zhong T Wong KW Cheng H et al.Transverse abdominis plane (TAP) catheters inserted under direct vision in the donor site following free DIEP and MS-TRAM breast reconstruction: a prospective cohort study of 45 patients.J Plast Reconstr Aesthet Surg. 2013; 66: 329-336Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar The latter offers the advantage of accurate placement and reduction in risk. In addition, a catheter can be placed to allow local anaesthetic to be infiltrated after operation. This is mostly placed under direct vision by the surgeon at the end of the procedure. Systemic postoperative analgesia usually consists of paracetamol, non-steroidal anti-inflammatory drugs if appropriate, and opioids which can be given using patient-controlled analgesia or orally. It is important that optimum analgesia is continued into the postoperative period to not only ensure patient comfort but also prevent surges in sympathetic activity which could compromise free flap survival. Secondary ischaemia occurs after flap transfer and reperfusion. This period is more harmful to the flap than primary ischaemia. Free flaps affected by secondary ischaemia present with massive intravascular thrombosis and significant interstitial oedema. Although the skin and fat of a DIEP free flap can tolerate up to 10–12 h of ischaemia, after only a few hours, irreversible pathological changes arise in the muscle used in a TRAM free flap. It is essential that all measures taken to ensure adequate tissue perfusion during surgery are continued after operation. The overall failure of DIEP free flaps is 0.9%.8Lie KH Barker AS Ashton M A classification system of partial and complete DIEP flap necrosis based on a review of 17, 096 DIEP flaps.Plast Reconstr Surg. 2013; 132: 1401-1408Crossref PubMed Scopus (51) Google Scholar These are most commonly due to surgical complications and therefore poor flap perfusion should be rapidly identified with expeditious return to theatre before compromise becomes irreversible (Table 1).Table 1Causes of free flap failureSurgical causesNon-surgical causesArterial—technical problems with anastomotic site, spasm, thrombosis due to vessel traumaOedema due to excess fluid administrationVenous—kinking of pedicle at the anastomotic site, spasm, thrombus, compression due to haematoma or dressingsHypercoaguable statesReperfusion injury due to prolonged ischaemic time Open table in a new tab Clinical flap observations remain the most common method of monitoring. Early detection remains the most important factor in the salvage of free flaps. Therefore, it is essential that staff caring for these patients are able to recognize an ischaemic flap. An auditory assessment of blood flow using an 8 MHz transcutaneous Doppler is often used by placing the probe on the skin overlying the perforator blood vessel on the flap. This spot is usually marked by the surgeons. The Doppler signal is checked at regular intervals after operation in recovery and on the ward. Evaluation of flap colourCapillary refill timeSkin turgorSkin temperatureBleeding on pinprick If the cause of flap ischaemia is arterial, the flap is cool, pale, with slow capillary refill time, no bleeding on pinprick, and has loss of arterial (triphasic) Doppler signal. If the cause is venous, the flap is warm, congested, bluish in colour, has brisk capillary refill time, rapid bleeding of dark blood on pinprick, and has loss of venous Doppler signal (normally a continuous sound). When recognized early and managed promptly (within 6 h), compromised flaps have a 75% salvage rate. The definitive management of a struggling or failing flap is usually surgical and patients require urgent re-exploration to inspect the vascular pedicle for kinks and compression, assess patency of the anastomosis, identify thrombus formation, perform embolectomy if appropriate, or administer intra-arterial thrombolysis. The same anaesthetic principles used intraoperatively should be continued in the event of compromised flap perfusion, to provide a physiological environment that promotes optimum flap flow. None declared. The associated MCQs (to support CME/CPD activity) can be accessed at https://access.oxfordjournals.org by subscribers to BJA Education.