Smoking can have significant detrimental effects on wound healing and success in digital replantation, but it does not appear to lead to an increase in free flap loss.1,2 Free tissue transfer has been performed on young and old patients with good outcomes, and age, per se, is not a major concern. Rather, it is the overall general health of a patient that is important. A patient must be able to tolerate the potentially long general anesthetic and insult of major surgery and be compliant with postoperative therapy. A natural concern with regard to free tissue transfer in children is vessel size, but often the vessels are of good caliber and will also be free of atherosclerotic disease, making the procedure more straightforward. In elderly patients, vessels may be more friable or stiff and have atherosclerosis, which makes free tissue transfer more challenging. Preoperative radiation can also make vessel dissection and anastomosis more difficult, but it does not represent a contraindication to surgery. Many breast reconstructions are performed after radiation therapy, as are salvage cases in head and neck cancer. Additional care must, however, be taken with vessel handling as the vessels tend to be more fragile and are more prone to intimal damage.3 If patients have a history of multiple venous thromboembolism (VTE) then a hypercoagulable disorder should be excluded; however, VTE, per se, is not a contraindication to free tissue transfer. Adequate prophylaxis with calf compression garments/hose/stocking and low-molecular-weight heparin will of course be required. Additional intraoperative heparin may be given. The risk of VTE can be assessed using the Caprini score.4
It is important to use the correct microvascular equipment in order to avoid damage to vessels and anastomoses. Microvascular clamps are specifically designed to prevent trauma to the endothelium and should have a closing pressure of less than 30 g/mm2. Heparinized saline is used in concentrations of 100 U/mL (not 10,000 U/mL). Topical papaverine works by blocking calcium (not sodium) channels and is useful to reduce vasospasm. Alternatively, 1–2% lidocaine or verapamil can be used. Ideally a microscope with at least 10× magnification should be used for vascular anastomoses; however, it is acceptable to use higher magnification loupes such as 3 to 4.5× for larger vessels.1,2 The coupler device is ideally suited to venous anastomoses, and can be used in both end-to-end and end-to-side connections.3 Although originally intended for venous anastomoses, it has been adopted by many surgeons for arterial anastomoses too. Spector et al4 used them routinely in the artery for breast reconstruction in transverse rectus abdominis myocutaneous (TRAM) and deep inferior epigastric perforator (DIEP) flaps with good results when the thoracodorsal pedicle was the arterial source vessel.
During microvascular surgery, it is vital that vessel trauma, desiccation, and tension across the anastomosis are minimized. Carefully grasping the adventitia is preferred to stabilize the vessel during dissection. The strip test is sometimes called an Acland test and is performed after the anastomosis has been completed. It involves carefully grasping the vessel distal to the anastomosis with two forceps and then gently milking blood distally so the vessel is empty between the two forceps. On release of the proximal forceps, the vessel should fill if the anastomosis is working correctly. The spurt test is used to check inflow before anastomosis is performed. This involves releasing all clamps from the input vessel, flushing with heparinized saline solution, and testing blood flow. Most surgeons advocate trimming of the adventitia to preserve 2–5 mm of exposed vessel end. The most difficult anastomosis should be done first as should the most difficult sutures within a given anastomosis. Although the size of vessel generally determines the number of stitches, there is no “set number” per vessel diameter. Essentially the aim should be to use “just enough” sutures to approximate and seal the vessel accurately. Insufficient sutures will leave potential openings for leakage and development of thrombus, while excessive sutures risk backwalling and causing vessel damage.1,2
4. Pannucci CJ, Bailey SH, Dreszer G, et al. Validation of the Caprini risk assessment model in plastic and reconstructive surgery patients. J Am Coll Surg 2011;212(1):105–112
A number of techniques are available to overcome size discrepancies between vessels. These include methods to increase the smaller vessel (spatulation) or to reduce the larger vessel (triangular wedge). Cutting the smaller vessel obliquely can also be helpful. In this case, an end-to-side anastomosis would be advisable, given the ratio of vessel mismatch is likely to be greater than 1.5:1 or even 2:1. Significant vessel mismatch results in alteration or disruption of flow mechanics and can promote vessel thrombosis so needs to be managed carefully. A further reason for using an end-to-side approach in this scenario is that distal limb blood flow through the anterior or posterior tibial vessels can be maintained. The use of an end-to-side anastomosis is often undertaken in head and neck cases where the flap vein is anastomosed into the internal jugular vein. Further options to address vessel mismatch include incorporation of a vein graft, but this introduces additional risk by doubling the number of anastomoses required and also adds a potential donor site harvest to the procedure.1–4 Alternatively, a modified geometric Kunlin’s technique can be used.5 This adds an axial incision to further lengthen the aperture in spatulated vessels. The coupler device can be very useful for managing size discrepancy between donor and recipient veins and may also be useful in some arterial anastomoses. However, in the lower limb the vessels are likely to be too thick or stiff walled to work well with a coupler and it is not routinely used in this setting (Figs. 8.1, 8.2, 8.3, and 8.4). Fig. 8.1 Ideal characteristics of an end-to-side anastomosis. 2x 30° x 75° Fig. 8.2 Methods of performing an arteriotomy. No. 11 blade Tenting technique Vascular punch Fig. 8.3 End-to-side anastomosis. A–D, Running suture technique. E, Interrupted sutures. A B C E D Running sutures Interrupted sutures
The main benefit of using an end-to-side anastomosis in this situation is the preservation of distal flow through the posterior tibial artery. This is particularly relevant given the history of trauma. An alternative is to use a flow-through flap (e.g., anterolateral thigh [ALT]) with two in-line anastomoses.1,2 End-to-side and end-to-end anastomoses both have equivalent patency and generally require a similar amount of sutures and operating time. Surgeons often find end-to-end anastomoses easier to perform than end-to-side, but it will depend on personal preference. When performing an end-to-side anastomosis, an arteriotomy is required in the source vessel. This is performed with either a beaver blade, scissors, or vascular punch. The angle of entry should be set between 30 and 70 degrees. The anastomosis is then performed with either interrupted or continuous sutures one side then the other (see Figs. 8.1 and 8.3).3
Transcutaneous tissue oximetry is a noninvasive method of continuously measuring perfusion quality of a free flap postoperatively. An oximetry probe measures tissue oxygen saturation (SpO2). The probe is placed on the skin flap intraoperatively to determine the baseline SpO2. Other than being a noninvasive technique, the main benefit of this monitoring approach is that it will detect vascular compromise of the flap earlier than clinical examination alone, thereby facilitating earlier re-exploration in operating theater if a problem arises. A study by Lin et al1 has shown improved flap salvage using this monitoring technique. However, its use in routine practice has not been uniformly adopted. The usual appearance of arterial insufficiency is a pale, cool flap with no capillary return and no bleeding to pinprick. A purple, swollen appearance with egress of dark blood (not bright red) to pinprick is characteristic of a congested flap secondary to venous outflow obstruction. Doppler imaging is a useful adjunct to flap monitoring, but it can be unreliable because of transmission of signals from adjacent vessels. Another modality for postoperative flap monitoring is thermography. This measures skin surface. Thermography measures skin surface temperature using a thermocouple device. Both venous and arterial occlusion can cause flap surface temperature to drop. Khouri and Shaw2 reported that a relative difference in flap surface temperature versus reference surface temperature of more than 1.8° C had a 98% sensitivity for vascular compromise and a 75% predictive value; however, accuracy was considered to be poor in intraoral flaps. Absolute flap temperature changes are less reliable without a reference nonflap temperature, because they are affected by changes in ambient or body temperature.
In the situation of a buried free flap, the most reliable monitoring method is to use an implantable Doppler device. This can be placed directly on either the anastomosed artery or vein and secured with a small ligaclip. Rates of salvage are reported to be very high using this device but sometimes the signal can be lost when in fact the vessel is still running. Clinical examination is difficult with buried flaps other than systemic parameters such as blood pressure and urine output. A handheld Doppler can be useful for some buried flaps but transmission from other vessels can compromise reliability. Laser Doppler and tissue oximetry each require the presence of a skin paddle for monitoring. Some surgeons will incorporate a small monitoring skin paddle where possible in otherwise buried flaps and this can be helpful. The downside is that this may require further surgery to remove it for aesthetic reasons and it tends to be quite small, thereby making assessment of it more difficult.1–4
Early recognition and surgical re-exploration of a failing flap are critical to optimization of outcomes in free flap surgery. Most flaps can be salvaged if surgery is performed within the first 2 hours following recognition of the problem. Accurate postoperative free flap monitoring is therefore key to free flap success. It is tailored to specific flaps but in general a combined approach of clinical examination to assess color, capillary refill, turgor, and temperature, along with Doppler assessment, is advised for free flap monitoring. The most common cause of flap failure is an anastomotic problem, leading to venous or arterial insufficiency. The no-reflow phenomenon is believed to be caused by endothelial swelling, platelet aggregation, and leaky capillaries in the presence of a patent anastomosis. It is less commonly seen as a cause of flap failure and although it may be reversible at approximately 4–8 hours, this is unlikely after 12 hours.1,2 One retrospective study reviewed late salvage cases (i.e., beyond 1 week) and highlighted the futile nature of attempts at such late flap salvage. Surgeons need to be realistic about the chances of saving a failing flap at any stage and remain objective about when a second reconstruction would be a preferable option.3
Some surgeons give a dose of intravenous heparin just before disconnecting or just after reconnecting the flap with the intention of reducing thrombosis at the anastomotic site. Others will reserve this for when the first anastomosis has clotted and the anastomosis must be redone. Aspirin inhibits platelet aggregation via cyclooxygenase. Heparin binds antithrombin III and results in inhibition of both antithrombin and factor Xa. No evidence suggests that systemic heparin will improve anastomotic patency, except perhaps in cases in which intraoperative clotting has occurred or the anastomosis requires revision. The use of systemic heparin increases the risk of postoperative bleeding, but its action is short-lived compared with low molecular heparin.1–3
Different techniques exist to repair transected nerves. They include epineural, perineural, or grouped fascicular. Outcomes are similar with all techniques, but perineural techniques may be technically more difficult. Grouped fascicular techniques can be helpful for larger nerves such as the ulnar nerve at the wrist, where specific branches can be identified. It is vital that neither excessive tension nor buckling of fascicles occurs at the repair site. For this reason, accurate trimming and use of interpositional grafts are advocated where necessary. The choice of graft in short defects in sensory nerves may be less important because vein grafts and polyglycolic acid tubes can have comparable outcomes to donor nerves such as the sural and antebrachial cutaneous nerves. Processed allograft conduits provide a further option, with results superior to those obtained with polyglycolic acid tubes. However, in larger defects autologous sural nerve grafts are the benchmark.1–5
When considering a business case for new operating room (OR) equipment, management will be interested in cost effectiveness of a product or device. As surgeons we are aware of many clinical benefits of the coupler device and these include its rigid ring configuration which stents the anastomosis open, a low rate of venous thrombosis (<1%), a minimal operator learning curve, ease of use, and the ability to manage intraoperative vessel size mismatches effectively. From the perspective of the managers, factors which reduce OR time and increase OR efficiency will have highest importance on their radar. OR time is expensive and hence any factors which can safely and consistently reduce OR time requirement will be valuable. The use of the coupler device has been shown to be significantly quicker to perform than a hand-sewn anastomosis. It has been associated with a 16-minute decrease in time compared with a hand-sewn anastomosis in one recently published study.1 With OR time expenses, the time saving would be likely to cover the costs of the device. A further potential cost benefit is the low thrombosis rate and hence need to return to OR. However, although this is lower than with hand-sewn anastomoses, couplers can still fail and need a return to the OR or indeed to be redone in the OR at the first sitting. Reasons for the coupler to fail include tearing of the vessel leaving a hole in the vessel wall, failure of the device to properly load or be detached from the applicator device, failure to remain closed (particularly if the vessel wall is thick and stiff), or residual thrombus or inadvertent injury to the intimal surface. Couplers do still need a microscope for their application and they don’t necessarily obviate the need for a surgical assistant in the OR, in spite of it being possible to use one independently. As standard, they do not incorporate an implantable Doppler device for postoperative monitoring although there is one device available on the market which does so. Couplers are mainly used for venous anastomoses; however, they have been used successfully in some settings within the arterial anastomosis.2–4
There is growing interest in surgical ergonomics and occupational health of surgeons. A recent study by Khansa et al1 explored work-related musculoskeletal injuries in plastic surgeons. This study showed that microsurgery is more likely than any other subset of procedures to exacerbate symptoms of musculoskeletal problems and that microsurgeons are more likely to have upper back and shoulder problems than other surgeons (odds ratios were 1.64 and 1.47, respectively). Surgeons’ posture and position are therefore essential to prevent fatigue, tremor, and avoid chronic musculoskeletal problems for surgeons. Recommendations for surgeons undertaking microsurgery, therefore, are to ensure a satisfactory position is maintained for both ease of microsurgery and hence effectiveness as well as surgeons’ occupational health benefits. The surgeon should sit with their feet flat on the floor, hips, knees and elbows at right angles, and with their back and neck straight. The hands and forearms should be supported with stacks or towels to minimize tremor and ensure comfort. Avoiding standing or stooping over the microscope is important as is avoiding having the cervical spine flexed for extended periods.