Prevention of Postoperative Cardiac Complications

Myocardial ischemia occurring within the first postoperative week after non-cardiac surgery is a major risk factor for future morbidity and mortality in surgical patients. The incidence of a serious cardiovascular event occurring within 2 years for this patient population is up to 20-fold higher. Postoperative myocardial ischemia is a potentially reversible risk factor for future complications and mortality.

The role of perioperative beta-blockade in non-cardiac surgery has matured in recent years. The development and validation of the revised cardiac risk index (RCRI) ( Table 29.1 ) has allowed for more accurate use of beta-blockers with respect to stratified risk. Early meta-analysis demonstrated decreased cardiac complications (50% reduced mortality rates) using atenolol. However, this was not stratified by cardiac risk. High powered studies have revealed that beta-blocker use may be harmful to some patients, causing hypotension, bradycardia, or even stroke. For patients with low cardiac risk (RCRI = 0), potential complications of beta-blocker use outweigh their benefits. High cardiac risk patients with RCRI ≥3 show a clear benefit with perioperative use of a beta-blocker. Intermediate risk patients with 1–2 risk factors have uncertain benefits, except vascular surgery patients.

Perioperative cardiac management is challenging. We recommend a multidisciplinary care approach with anesthesia and medicine to help choose the best cardiac prophylaxis for each patient.

Deep Vein Thrombosis/Pulmonary Embolism Prophylaxis

Deep venous thrombosis (DVT) and pulmonary embolism (PE) pose a clinical challenge for the reconstructive surgeon. The risk for a DVT/PE and its sequelae must be weighed against the risk of hematoma formation. Although venous clots can form in any part of the venous system, they most commonly develop in the calves. Approximately 50% of patients with untreated proximal DVTs will develop a symptomatic pulmonary embolism within 3 months. Long-term morbidity from post-thrombotic syndrome may be substantial. Most fatal events of venous thromboembolism (VTE) occur within 3–7 days of surgery. As such, deep vein thrombosis and pulmonary embolism are among the best examples of preventable postoperative complications.

Plastic surgeries vary widely in terms of risk strata, and overall VTE incidence, and is reported to be on average 1.69%. Few studies have examined the VTE incidence in free tissue transfer, however, DVT rates of 3.4% (range of 2–6%) have been reported for free flap breast reconstruction. More complicated free flap procedures seemingly may have a higher rate of VTE due to increased operative time and more complicated patients.

Primary thromboprophylaxis is effective in reducing the incidence of asymptomatic and symptomatic VTE in sur­gical patients via mechanical measures or anticoagulant drugs. According to the American College of Chest Physicians’ Antithrombotic Therapy and Prevention of Thrombosis, 9th edition (AT9) practice guidelines, VTE falls into four general risk categories: very low, low, moderate, and high. Several studies have also demonstrated that certain factors place patients at higher risk, including age >60 years, malignancy, prior history of VTE, bed rest >4 days, and anesthesia >2 h. The Caprini score, which was developed in the early 2000s, assigns various points to patient characteristics that put them at increased risk of thrombosis and is incorporated into the AT9 guidelines for plastic surgery patients ( Table 29.2 ). The Caprini score was subsequently validated in plastic surgery patients.

Most hospitals use guidelines similar to those in Table 29.2 , and in the United States VTE prophylaxis is required within 24 h of surgery unless contraindicated. The risks of VTE must be weighed against those of hematoma, since free tissue transfer often entails wide undermining in natural tissue planes. Most plastic surgery patients fall into the moderate–high category with recommended chemoprophylaxis. Hematoma rates are 0.5–1.8% without prophylaxis, and combined use of mechanical prophylaxis and low-molecular-weight heparin (LMWH) does not create a significant difference in hematoma formation compared with mechanical means alone.

Suspected DVT should be diagnosed promptly. In patients with low clinical suspicion, a D-dimer (fibrin degradation product) test can be completed and if negative, no further testing is needed. In patients with multiple risk factors and high clinical suspicion, compression ultrasound is the test of choice. Ultrasonography has a sensitivity of 97–100% and a specificity of 98–99% for detection of proximal DVT. Therefore, full compressibility of the femoral and popliteal veins essentially excludes proximal deep vein thrombosis. The rate of VTE in patients with a negative ultrasound was 0.7%, indicating that few thromboses were missed and that therapeutic anticoagulation may be safely withheld when ultrasonography is normal. On the other hand, if the ultrasound is positive, treatment should begin with LMWH, fondaparinux, or IV, or subcutaneous unfractionated heparin. If a pulmonary embolism is suspected, CT angiography is the diagnostic test of choice with clinical validity similar to that of conventional angiography. The total rate of subsequent venous thromboembolic events after a negative CT scan at 3 months is 1.4%.

The AT9 recommends initial treatment with LMWH or fondaparinux instead of unfractionated heparin. Unfractionated heparin is inconvenient for both patients and medical staff, due to frequent injection and monitoring. Low-molecular-weight heparin does not require laboratory monitoring due to a more predictable dose–response relationship of the medication. Its half-life is longer than unfractionated heparin, which allows for once or twice daily dosing, and it has a reduced risk for immune mediated thrombocytopenia or osteoporosis. In severely obese or renal insufficiency patients, monitoring anti-factor Xa activity 4 hours after injection may be useful. Thus, LMWH is the drug of choice. Daily doses of LMWH are preferred over twice daily.

If the patient has a contraindication to anticoagulation, a retrievable inferior vena cava filter may be placed to prevent fatal pulmonary embolism. This device may be removed at a later date when the danger has passed.

Pneumonia and Pulmonary Prophylaxis

Postoperative patients, especially the elderly and those with chronic obstructive pulmonary disease, are prone to developing acute pulmonary complications from either poor inspiratory effort while lying supine or respiratory splinting from incisional pain. Pulmonary complications after surgery, much as with cardiac complications, can result in longer hospitalization, increased cost, and increased morbidity/mortality.

Atelectasis and pulmonary infiltrates can rapidly develop and progress to pneumonia in the early postoperative period. An incentive spirometer measures the inspiratory capacity of the lungs and provides patients with visual cues on their progress. This encourages daily goals and deeper inspiratory effort. Meta-analysis demonstrates that incentive spirometry is the only strategy of proven benefit. Selective nasogastric tube use has probable benefit reducing pneumonia and atelectasis in patients with nausea, emesis, or distention when there has been an abdominal component to surgery.

If pneumonia is suspected, obtaining a chest X-ray and sputum culture followed by immediate initiation of antibiotic therapy is essential. Empiric antibiotic therapy should treat bacteria that are common for hospital-acquired pneumonias such as Pseudomonas , Enterobacteriaceae , Streptococci , and Haemophilus . Antibiotic-resistant pathogens such as Pseudomonas , Acinetobacter, and methicillin-resistant strains of Staphylococcus aureus are much more common after prior antibiotic treatment, prolonged hospitalization, or mechanical ventilation. After 48–72 h, antibiotics should be tailored appropriately to the organisms growing on culture. Correct empirical antibiotic treatment is vital, and local resistance patterns should be discussed with the infectious disease team as improper antibiotic use shows higher mortality. Postoperative nosocomial pneumonias should be treated for 1–2 weeks with appropriate antibiotic therapy.

Control of postoperative pain is a vital component for improving pulmonary function by reducing inspiratory splinting and allowing for early ambulation. There are many strategies available for pain control (oral, IV, patient-controlled anesthetic [PCA] and regional). These approaches are highly subjective and must be tailored to each patient. Paramount is frequent reassessment and adjustment of medications to allow pain control without oversedation. Intravenous or oral narcotics are the first choice. However, these medications have significant side effects, including somnolence, constipation, urinary retention, respiratory depression, nausea, and altered mental status, especially in the elderly. Recently, there has been increasing use of regional anesthesia (pain pumps, nerve blocks, epidurals) for tissue transfer patients. In fact, epidural use in free flap surgery significantly reduces the percentage of patients with postoperative atelectatic fevers. In addition, disposable pain pumps can infuse 0.25% bupivacaine at a rate of 2.08 cc/h directly into the surgical site for 48–72 continuous hours. Patients who use these devices report a two-fold decrease in their overall pain level and have a five-fold decrease in use of oral and intravenous pain medications with fewer episodes of nausea, emesis, and other side effects. Epidural anesthesia has also been shown to improve pulmonary function by giving excellent pain control, improved pulmonary compliance, and allowing normal diaphragm function. However, epidural anes­thesia has not been proven to decrease the incidence of pneumonia.

Hyperglycemic Control

Hyperglycemia in response to physiologic stress occurs in patients who undergo major surgery, trauma, or sepsis, as well as exogenous causes of hyperglycemia, including steroid administration and other therapeutic interventions. This “stress hyperglycemia” applies to non-diabetic patients; however, patients with preexisting diabetes are also at risk for hyperglycemic events in the perioperative period.

Hyperglycemia is associated with poorer outcomes, in­­creased risk for wound infection, and increased morbidity and mortality in both diabetic and non-diabetic patients. While intensive insulin therapy (blood glucose, BG 80–110 mg/dL) was initially believed to reduce mortality, blood­­stream infections, renal failure, and prolonged mechanical ventilation, it is now apparent that intensive control results in a six-fold increase in severe glycemic events (BG <40 mg/dL). This is an independent risk factor for mortality, especially in critically ill patients compared with conventional control. It is recommended that surgeons aim for blood glucose levels that are slightly higher than 80–110 mg/dL and <180 mg/dL, though no threshold value is currently defined in the literature.

Wound Infection Prophylaxis

To achieve optimal prophylaxis against surgical site infections, adequate concentrations of an appropriate antibiotic must be present in the serum, tissue, and wound for the entire time that the incision is open and at risk for bacterial contamination. Antibiotics should be active against the type of bacteria that are likely to be encountered during a particular type of operation. The choice and duration of antibiotic prophylaxis should have the least effect on the patient’s normal bacterial flora and be based upon expected bacterial contamination, as well as fit within the microbiologic ecology of the hospital.

A beta-lactam antibiotic (e.g., cefazolin) is usually the first choice for perioperative prophylaxis and is recommended to begin 60 min prior to the incision, However, research has demonstrated that infusion at the time of anesthesia induction is safe and results in adequate serum and tissue antibiotic levels prior to the incision. If the patient has a beta-lactam allergy, vancomycin or clindamycin is recommended.

The majority of published research demonstrates that antimicrobial prophylaxis after wound closure is not necessary, and most studies, including those in the plastic surgery literature, that have compared single- to multiple-dose prophylaxis, have not revealed additional benefits. However, prolonged use of prophylactic antibiotics is associated with the emergence of resistant bacterial strains. Antibiotic prophylaxis should end within 24 hours after the operation.

Prophylaxis should be used for cases with prosthetics, microsurgical cases, clean contaminated cases in the oral cavity or genitourinary system, ventral hernias, or contaminated cases. While these data are promising for evidence-based practice in plastic surgery, there is still no consensus. Preventing intraoperative hypothermia, perioperative supplemental oxygen, and aggressive fluid resuscitation, and prepping the operative field with chlorhexidine may decrease surgical site infection rates.

Smoking Cessation

Smoking in the perioperative time period is related to higher complications, especially in relation to wound healing. There is a high correlation between smoking and rates of reoperation and tissue necrosis. Urine cotinine tests clearly demonstrate a high preponderance of deception regarding this habit as well. Of patients who stated that they quit smoking, 4% will have positive urine tests.

It is well documented that smoking increases the overall complication rate for tissue transfer surgery. For example, smoking patients undergoing reconstruction with pedicle TRAM flaps have increased flap, abdominal skin, and umbilical necrosis. Heavy smoking is generally considered to be a contraindication for pedicled TRAM flap breast reconstruction. However, free TRAM flap reconstruction in smokers is not associated with increased pedicle thrombosis, flap loss, or fat necrosis, but does have increased risk for mastectomy skin flap necrosis, abdominal flap necrosis, and hernia formation. These perioperative complications are significantly reduced when the reconstruction is delayed at least 4–6 weeks after smoking cessation, and some studies even suggest 8 weeks as a more appropriate timeframe.

Clinical Assessment

To construct a skin paddle, a portion of the free flap’s skin is exteriorized and may be used to evaluate perfusion by monitoring skin temperature, capillary refill, turgor, color, and bleeding. This skin paddle technique is one of the most accurate and reliable ways to evaluate flap perfusion. It allows the surgeon to monitor for both arterial insufficiency as well as venous obstruction. Two techniques are commonly used for examining bleeding from the flap, either pinprick with a 25-gauge needle or a partial dermal incision with a 15 blade. Arterial insufficiency is present when the skin is pale and cool and fails to bleed after a needle stick or partial dermal cut. Venous congestion usually results in edema and darkening of the skin color. During early venous obstruction, a needle stick or partial dermal cut will cause rapid bleeding of dark blood. A skin paddle should be large enough to make correlation with the vascular pedicle more reliable. Early signs of vascular compromise may be subtle while monitoring a skin paddle and require an experienced examiner to recognize problems.

Clinical observation is indispensable in monitoring flaps. However, most surgeons rely on adjunctive methods to optimize flap salvage because continuous observation by the surgeon is currently not possible. Adjunctive monitoring methods allow the nursing staff to observe the flap and alert the surgeon at the first sign of vascular insufficiency.

External Doppler

Currently, there is no single adjunctive monitoring technique widely accepted as the method of choice, but the handheld Doppler is the most common device in use. We prefer the ES-100x Mini-Doppler with the 8 MHz probe by Koven Technology Inc (St Louis, MO). Its most important limitation is that a clinician may detect the recipient vessels’ Doppler signal instead of the flap’s vascular pedicle due to proximity, which may mislead the observer to believe that the flap’s pedicle is patent when in reality, a thrombosis has occurred. Therefore, it is recommended to place a marking suture in the exact location of the vascular pedicle’s location relative to the skin. Handheld Dopplers are also useful for evaluating buried flaps. However, this is not as easy or as accurate, and sometimes not even possible.

The arterial and venous signals can both be monitored using this Doppler device. External Doppler monitoring of the vein will demonstrate flow that increases when the flap is compressed (venous augment) Additionally, the type of arterial signal can be distinguished by an experienced listener. A triphasic signal that becomes monophasic may indicate a change in the status of the flap and venous occlusion.

Internal Doppler

The implantable Doppler can measure blood flow across a microvascular anastomosis and is an effective tool to monitor flap perfusion and improve salvage rates, especially in buried flaps. Initial experience with this device was not positive with a 3% false-positive rate, leading to unnecessary re-explorations, and a 5% false-negative rate when the probe was placed on the artery. Later studies showed a false-positive rate of 6.8% and a false-negative rate of 0%. Further, up to a 5-h delay was found between a venous obstruction and the loss of the arterial signal in large muscle flaps. This is also a disadvantage for the handheld Doppler.

However, some studies suggest that placing an implantable probe on the vein instead of the artery is a more rapid and accurate method of detecting a pedicle thrombosis. This technique detected any vascular compromise without delay. These probes may be useful in patients with darkly pigmented skin in whom clinical detection of venous congestion is difficult.

With buried flaps, the implantable Doppler has been shown to have similar flap success rates (98.2%), and has allowed for salvage of buried flaps that are difficult to monitor. Inexperienced nursing and house staff can quickly detect a perfusion problem in the flap with the internal Doppler probe. However, the probe is costly, with reports of malfunction or it becoming displaced during the early postoperative course. These problems require further monitoring techniques, such as clinical observation or handheld Doppler examination to be performed. For buried flaps, clinical examination includes monitoring for increase in edema. This can indicate congestion of the flap due to venous thrombosis or inadequate drainage. It could also indicate hematoma formation, which could be the result of a venous obstruction leading to bleeding from the buried flap.

Laser Doppler

A laser Doppler flowmeter provides an objective measurement for flap perfusion, but the observer cannot rely on absolute values. It requires experience to interpret, as relative perfusion values are different for every tissue and patient, and may fluctuate because of physiologic microcirculation variation or artifacts. Therefore, the observer must monitor the trend rather than the absolute values. This fact is of particular importance during venous occlusion, when a drop in value is not as abrupt and steep compared with arterial obstruction.

Yuen and Feng had a series of nursing staff record values every 15 min for 1 h, every 30 min for 2 h, and then every 4 h for 4–5 days. When a vascular occlusion occurred, the perfusion values decreased by 50% or more for longer than 20 min. Using these criteria, they reported no false-positive values with no unnecessary re-explorations and one false-negative when the observation protocol was violated. In another series, the flap salvage rate with laser Doppler was 88%, and in two cases, the laser Doppler was the only clinical measure of flap decline. This system can be helpful in darkly pigmented skin or a pure muscle flap, where clinical evaluation is not straightforward. However, the laser Doppler flowmeter equipment is expensive, and some studies have found it to be inaccurate as a result of probe dislocation artifacts. The laser Doppler flowmeter, as other monitoring systems, may provide the reconstructive surgeon with an early indication of impending flap failure, thus providing enhanced opportunity for flap salvage.

Near Infrared Angiography

Near infrared angiography is a semi-quantitative measure of microvascular perfusion within a soft tissue flap. This technique is relatively new and is based on the detection of a systemically administered dye (indocyanine green) by exposing the tissue to near infrared light and detecting emitted signals through an optic filter. Not only can this technique determine the quality of perfusion throughout the flap, but it also may detect the area of tissue nourished by a particular vascular pedicle on which a flap is raised, thus assisting in the flap design. This method has been shown to be useful in evaluating zonal perfusion of free TRAM flaps intraoperatively as a way to avoid partial flap necrosis. Another advantage of near infrared angiography is that it provides discrete visualization of perforator blood vessels. This method, however, is a static evaluation of the perfusion at one particular point in time and cannot be used as a continuous form of monitoring. A flap with a skin paddle or meshed split-thickness graft over muscle is necessary for monitoring, which prevents evaluation of a buried flap. Near infrared angiography may appear too sensitive, with a 66% false-positive rate found in a small series attempting to detect postoperative venous congestion.

Pulse Oximetry

This method relies on two diodes that emit light at a wavelength of 660 nm (visible) and 940 nm (infrared) and a photodiode receiver. It measures oxygen saturation by detecting a difference in light absorption between oxyhemoglobin and reduced hemoglobin. It provides continuous monitoring and is particularly useful in monitoring digit replants and toe-to-hand transfers.

Photography

A useful tool used by some surgeons is photography. They take a picture of the flap when the flap appears well perfused and without congestion and post the picture near the bedside. Nurses are instructed to call the surgeon if there is a change in appearance of the flap when compared with the picture.

Surface Temperature

For intraoral flaps and thin flaps placed on the trunk, surface temperature monitoring may be less accurate. A surface temperature probe (a liquid crystal temperature probe) may be placed on the flap and another on a normal adjacent skin. Temperature differences of 3°C are associated with arterial insufficiency and 1–2°C may be more associated with venous insufficiency.

Cellular and Wireless Devices

The wide dissemination of cell phones and wireless technology is also having implications on free tissue transfer monitoring. Recently, cell phone imaging was used to clinically evaluate flap perfusion in the early perioperative time period, allowing for senior staff surgeons to more rapidly assess a flap with questionable vascular status. Flap survival rose to 100%, flap salvage rose from 50–100%, and time from flap compromise to reoperation was also drastically decreased. When compared with traditional monitoring, remote smart phone photography shows similar accuracy in assessing flaps. These are promising findings, and further integration with wireless devices will surely lead to streamlined care for tissue transfer patients. It is also likely that advances in telemedicine will allow senior surgeons to remotely view a flap in high definition to allow accurate and experienced assessment in real-time. As these technologies continue to evolve, data encryption and HIPAA compliance will be essential for long-term viability of these unique and powerful monitoring.