Despite the VTEP study’s title, the actual data do not support its conclusions. To find a significant treatment benefit, the authors used logistic regression. The authors determined that the mean Caprini score was higher for the treatment group than for the historical control group. Controlling for this difference seems reasonable. However, the authors also adjusted their data to account for a disparity in mean length of hospital stay (3.8 days for treated patients vs 3.1 days for historical controls), a much more questionable statistical maneuver for several reasons. First, the length of hospitalization is not a known factor increasing the risk of thromboembolism. In fact, Caprini15 believes that patients after discharge may be just as sedentary as they were in hospital, remarking, “these individuals spend most of the time in a recliner, which is not early ambulation but rather early angulation.” Second, from a statistical perspective, the sample sizes in the hospital stay subgroups are much too small to allow a reliable statistical analysis. Third, anticoagulation was continued for the duration of the hospitalization,3 so that patients with longer admissions would have also received longer periods of anticoagulation.
Even with the authors’ adjustments, the data are too evenly distributed to skew sufficiently to find a significant treatment advantage for patients with higher Caprini scores. Nevertheless, nonsignificant differences (P = 0.230 and P = 0.182) are used to support the authors’ conclusions. These investigators also report a significant (P = 0.042) overall treatment benefit. It is difficult to imagine how an identical 1.2% incidence of this complication for treatment and control patients (Figs. 3 and 4) could be adjusted to show a significant overall treatment benefit. Statistical modeling requires prudence so that it does not become a form of statistical photoshopping. This method should not be used to adapt the data to conform to the investigators’ favored outcome.1
Twelve authors were listed on the VTEP article3 including some well-known researchers. The study was funded by the Plastic Surgery Foundation.3 Pannucci3 has a grant from the National Institute of Health, and of course, the University of Michigan is a respected academic institution. Do these considerations impart authority to the conclusions? Sackett,19 one of the founders of evidence-based medicine, once commented: “The first sin committed by experts consists in adding their prestige and their position to their opinions, which give the latter far greater persuasive power than they deserve on scientific grounds alone.” No degree of personal or institutional authority can take precedence over the facts. Pannucci et al2–5 have written extensively in favor of anticoagulation, including 4 articles published in Plastic and Reconstructive Surgery in the last 2 years. None of us is immune to our own prejudices.
Some might argue that we had better accept chemoprophylaxis because it is the trend in medicine and surgery—“everyone else is doing it.”1 Interestingly, orthopedic surgeons may be having second thoughts; the 2012 recommendations of the American College of Chest Physicians allow for the use of aspirin instead of low-molecular-weight heparin in orthopedic surgery.20 Perhaps surprisingly, a large randomized study among hospitalized patients, reported recently in the New England Journal of Medicine,21 found no benefit in thromboembolism risk for patients who were given enoxaparin. This finding was made all the more remarkable by the fact that the study was funded by the manufacturer of enoxaparin. If plastic surgeons are not careful, they may be jumping on the anticoagulation bandwagon just as our colleagues are jumping off.
This controversy would be less important if anticoagulation did not add to the complication rate of surgery. Pannucci et al4 conclude that the hematoma rate is not increased by enoxaparin. At the same time, these investigators ask plastic surgeons to choose between a thromboembolism and a hematoma.1,10–12 Enoxaparin is known to cause wound hematomas in approximately 11% of patients and drug-induced thrombocytopenia in 1.5% of patients.22Figure 6 compares hematoma rates in recent publications.8,23–25 Two of these studies23,24 report hematoma rates of 7.3% and 12.5% in anticoagulated patients, in the expected range. These figures contrast with rates of < 1% among untreated and control patients.8,23,25
As any plastic surgeon will attest, hematomas are not just an inconvenience. A seroma is an inconvenience; hematomas have serious consequences. They frequently cause skin necrosis and wound dehiscences.8 Hematomas are likely to cause anemia, adding to patient morbidity, especially after combined liposuction and abdominoplasty procedures that involve substantial blood loss.26 Bleeding may lead to unplanned blood transfusions and hospitalizations.23 Hematomas are not conducive to a successful elective cosmetic surgery practice. With widespread implementation of chemoprophylaxis, some patient deaths will inevitably result from exsanguination, iatrogenic deaths in patients who were unlikely to develop a thrombosis in the first place. Even one such death is unacceptable if the benefit of anticoagulation is unproven.18
A compensatory benefit is unclear; thromboembolisms still occur despite anticoagulation (Fig. 7).13,23,24 “Chemoprophylaxis” may not live up to its billing; it does not prevent venous stasis, hypercoagulability, or vessel injury—the Virchow triad of factors implicated in the formation of a thrombosis.27
Risk stratification aims to determine the risk of an individual suffering a particular condition. The VTEP study reveals that affected patients are spread across all Caprini groups (Fig. 2). The finding that there were almost equal numbers of patients affected by thromboembolism in patients with Caprini scores < 7 (20 patients) as in patients with scores ≥ 7 (22 patients) casts doubt on the value of risk stratification. Approximately half (52.4%) of the affected patients will be identified and receive treatment. Patients selected for treatment by risk stratification have a 3.0% thromboembolism risk (22 of 735) instead of a 1.2% thromboembolism risk, a difference of < 2%. If used as a screening test, risk stratification (Caprini score ≥ 7) would have a sensitivity of 52.4% and a specificity of 3.0%, or a false-positive rate of 97.0% and a false-negative rate of 47.6%, dismal numbers indeed.
Alternatively, one could treat patients with Caprini scores < 7 and capture almost as many cases of thromboembolism (20 patients). Admittedly, the number of treated patients would be greater. However, those patients selected would be more robust (ie, younger and healthier) and better able to tolerate bleeding. In fact, one might argue that risk stratification in effect assigns a greater bleeding risk (11% instead of < 1%)8,22–25 to patients who are least able to tolerate the hemodynamic effects of blood loss, an example of the law of unintended consequences and a challenge to the principle of primum non nocere. It makes more sense to adopt a treatment strategy that benefits all patients, making risk stratification unnecessary.
SAFE (Spontaneous breathing, Avoid gas, Face up, Extremities mobile) anesthesia is offered as an alternative method to reduce thromboembolism risk and improve safety. As in traditional general anesthesia, it requires the assistance of an anesthesiologist or certified nurse anesthetist.25,26
The Caprini model does not include the type of anesthesia as a risk factor.15,16 However, there have been multiple reports of reduced thromboembolism risk in patients who are administered intravenous anesthesia without muscle relaxation (Fig. 8).25,28–33 The theory is that avoiding muscle paralysis prevents blood pooling in the lower extremities,7,30,31 reducing the opportunity for venous stasis—a known factor implicated in thromboembolism.27
Figure 7 depicts the incidence of this complication in series of plastic surgery patients treated with general endotracheal anesthesia.3,23,32,34 A German study published in Plastic and Reconstructive Surgery in 200835 assessing serious complications after liposuction found that all 8 liposuction fatalities occurred in patients administered general anesthesia and none occurred in patients treated with intravenous sedation and local anesthesia. A survey conducted by Reinisch et al32 found a significant reduction in risk of thromboembolism among face-lift patients treated with intravenous sedation and local anesthetic compared with patients who received traditional general endotracheal anesthesia. Although there is no prospective controlled study, this empirical evidence is compelling and should not be dismissed (Geerts WH, personal communication, April 16, 2013). My own experience includes only one case of deep venous thrombosis during the last 10 years, occurring in 2005 in an abdominoplasty patient with a score of 3 using the 2010 Caprini model. This case was encountered during a prospective 5-year clinical study of 551 consecutive patients treated with liposuction and abdominoplasty.25 Fortunately, she made a full recovery (Fig. 9). No cases of thromboembolism occurred in a 10-year prospective clinical study of cosmetic breast surgery patients.36 Details of the anesthetic sequence including medications and dosing are beyond the scope of this article but are published separately.26 My experience is by no means unique.28–31
There is little prospect of a prospective controlled study. Such a study would not be feasible considering the low incidence of this complication.18 Moreover, ethical considerations may not permit such a study because of the profound empirical treatment difference (Figs. 7 and 8 use the same horizontal scale). In view of the many other advantages of SAFE anesthesia (eg, eliminating the risk of malignant hyperthermia),1,18,26 it may be difficult to justify a traditional general endotracheal anesthetic if a safer alternative is available.
Elective outpatient plastic surgery may be performed using intravenous infusions of propofol (provided it remains available) in combination with a laryngeal mask airway.26 Muscle paralysis is unnecessary, even when performing abdominoplasties with rectus plication. Infusion of the abdomen with an anesthetic solution provides adequate anesthesia of the abdominal wall.25,26 Spontaneous breathing allows the anesthetist to use the patient’s respiratory rate to guide intraoperative dosing of analgesics, expediting recovery. Respiratory alkalosis and secondary hypokalemia from mechanical ventilation are avoided.26
Inhalational agents have side effects.26 These include cardiovascular and respiratory depression, bronchial irritation, malignant hyperthermia, increased nausea, and possible exposure to operating room personnel.
The patient may be turned from side to side to access all areas for liposuction.25,26 Supine and lateral positioning avoid the need for a hip bolster and pelvic pressure that might impair venous return from the lower extremities.23 Avoiding prone positioning makes intubation and mechanical ventilation unnecessary, avoids facial pressure, allows simultaneous breast surgery (best performed first to optimize sterility), and eliminates an unnecessary delay in surgery for patient repositioning.
By turning the patient from the supine position to each side to infuse the areas with anesthetic solution and then repeating the process for liposuction, the lower extremities are kept moving, reducing the opportunity for venous stasis.26
CHOOSING AN ANESTHESIA METHOD
Figure 10 demonstrates the 4 commonly used anesthetic methods. Local anesthesia is impractical for large cases or combination surgery. Conscious sedation provides a reduced risk of deep venous thrombosis.31 However, these patients typically receive higher doses of benzodiazepines and fentanyl, prolonging recovery times.37 General endotracheal anesthesia provides adequate anesthesia but carries additional risks, as discussed.26 Total intravenous anesthesia offers an ideal “goldilocks” anesthetic,26 combining patient comfort and safety. Surgical decisions typically rest on an assessment of the anticipated benefit versus risk. The same analysis applies to administration of a medication or anesthetic (Figs. 11 and 12).
As discussed earlier, the data reveal that risk stratification using Caprini scores is ineffective. In reality, it is impossible to reliably predict which patients will be affected. Thromboembolisms cannot be considered “never events,”34 in that it is unreasonable to expect a surgeon to never encounter one. After all, pulmonary emboli can occur even without surgery. The best we can do is endeavor to lower the probability to a baseline risk. Blaming the surgeon for such an unpredictable event compounds the tragedy of a patient death caused by a pulmonary embolus. Unless we recognize the limitations of risk stratification and chemoprophylaxis, our colleagues may soon be held liable for: (1) not prescribing anticoagulation to a patient who develops a thromboembolism or (2) prescribing anticoagulation to a patient who suffers bleeding consequences that may include death. Do we really wish to needlessly expand our medicolegal liability?
Chemoprophylaxis has no proven benefit in plastic surgery. Risk stratification is ineffective. A SAFE alternative to chemoprophylaxis is available that not only avoids additional risk but also adds to patient safety. The choice for plastic surgeons is not between a venous thromboembolism and a hematoma. The choice is between a thromboembolism and adjusting our anesthesia and surgery habits to reduce the risk to a baseline level.
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3. Pannucci CJ, Dreszer G, Wachtman CF, et al. Postoperative enoxaparin prevents symptomatic venous thromboembolism in high-risk plastic surgery patients. Plast Reconstr Surg. 2011;128:1093–1103
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12. Wilkins E.. Preventing VTE: reviewing the evidence and implications for practice.Presented at: Plastic Surgery 2013: 82nd Annual Scientific Meeting of the American Society of Plastic SurgeonsOctober 11–15, 2013San Diego, Calif
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© 2014 American Society of Plastic Surgeons
37. Byun MY, Fine NA, Lee JY, et al. The clinical outcome of abdominoplasty performed under conscious sedation: increased use of fentanyl correlated with longer stay in outpatient unit. Plast Reconstr Surg. 1999;103:1260–1266