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Surgical Technique


Risks and remedies when your surgical patient is obese

How to plan and safely manage surgery—and ensure that the patient’s expectations are realistic

October 2007 · Vol. 19, No. 10

IN THIS ARTICLE

The authors report no financial relationships relevant to this article.

The adverse consequences of obesity go far beyond aesthetic and psychosocial concerns. Patients who are markedly overweight face a real risk of developing severe health conditions—not just cardiac disease, diabetes mellitus, and hypertension, but also sleep apnea, venous thromboembolism, certain cancers (particularly breast and uterine), and biliary tract disease. Obesity also contributes to menstrual abnormalities and infertility and may complicate pregnancy.

Surgery in these patients poses a number of challenges. Not only does obesity frequently compromise the technical aspects of a procedure, it requires the surgeon to use certain measures in the preoperative and postoperative phases of management, such as counseling the patient extensively about the risks and potential complications she faces, initiating antibiotic prophylaxis, and ensuring early ambulation. These and other measures are especially important when uncontrolled, coexisting disease is present.

Not every obese patient is a significant surgical risk, so care should be individualized and use a team approach involving the gynecologist, anesthesiologist, primary care physician, and other appropriate subspecialists.

This article outlines the parameters of good surgical care in the obese patient, defined here as having a body mass index (BMI) of 30 kg/m2 or above, or 35 kg/m2 or above for morbid obesity. Whenever possible, we draw our recommendations from the published literature. In the absence of data, we base them on our surgical experience in the obese population.

Risks of surgery

It is imperative for the gynecologic surgeon to discuss the special risks of surgery with the obese patient well in advance of the operation and to formulate a systematic plan for evaluation, utilizing other members of the team when necessary. If the surgeon keeps the following risks in mind and is proactive, complications can be kept to a minimum.

Poor wound healing

Wound healing is a complex process involving several concurrent phases; an abnormality in any phase may impair healing. Those phases are:

  • inflammatory phase, in which fluid and cells are released to clean the wound and prepare for the next phase of healing
  • fibroplastic (proliferative) phase, in which fibroblasts accumulate and form collagen, the building block of connective tissue. This stage is marked by neovascularization and increased formation of granulation tissue
  • wound contraction
  • remodeling/maturation, in which new collagen is laid down as old collagen is broken down, resulting in scar formation.

Preparing for surgery in the obese patient: 10 preoperative steps

  1. Obtain a chemistry panel: complete blood count, prothrombin time, activated partial thromboplastin time, and arterial blood gas studies. Type and cross-match if significant blood loss is expected
  2. Order a chest radiograph and electrocardiogram
  3. Test pulmonary function only if the patient has a history or suspected history of obstructive lung disease
  4. Order echocardiography only if the electrocardiogram or history suggests compromised cardiac function
  5. Instruct the patient on the use of incentive spirometry
  6. Prescribe a mechanical bowel-cleansing regimen if inadvertent injury is likely
  7. Notify anesthesiology and operating room personnel before the patient’s arrival
  8. Give 1 g of cefoxitin or another cephalosporin 60 minutes before the start of the procedure3
  9. Give 5,000 U of subcutaneous unfractionated heparin at least 2 hours before the start of surgery, and administer it every 8 hours until discharge.6 Alternative regimens: 5,000 U of dalteparin, a low-molecular-weight heparin, 12 hours before beginning the procedure and every 12 hours until discharge, or 40 mg of enoxaparin 12 hours before beginning surgery and every 12 hours until discharge
  10. Apply a pneumatic calf-compression apparatus in the operating room

Obese patients possess a thick layer of adipose tissue, which by its nature and location is minimally vascularized. This tissue essentially becomes dead space, an ideal medium for bacterial growth. Many obese patients also have diabetes mellitus, malignancy, or other comorbidity that further impairs healing.

As a result, obese patients are at increased risk of wound complications, breakdown, and subsequent dehiscence and evisceration. This translates into increased febrile morbidity, prolonged hospitalization, and higher cost.

What the data show. A number of studies have documented a higher incidence of wound complications in obese patients. In one retrospective review, Gallup1 observed an increased risk of wound complications in obese patients, but the incidence diminished after implementation of a protocol of meticulous cleansing, subcutaneous heparin, and modified incision and closure techniques. In a similar retrospective study of 300 obese patients, Pitkin2 reported wound complications among approximately one third of patients and postoperative fever among more than three quarters. Surgical-site infections are thought to occur in as many as 5% of patients.

Prophylaxis may be effective in some patients, but can be challenging. It entails meticulous skin cleansing and careful consideration of where the incision is placed, type of closure, use of a drain, and antibiotic administration.

Antibiotic prophylaxis is based on the theory that its presence in host tissues will alter natural defense mechanisms and kill bacteria that inoculate the wound. Because the window of efficacy is narrow, antibiotics should be administered shortly before the time of inoculation (ie, shortly before the time of incision, vaginal entry, etc.). Current guidelines suggest the use of broad-spectrum agents, including a cephalosporin, approximately 60 minutes before the incision. Redosing is recommended for procedures that last longer than 3 hours, as well as for those that involve significant blood loss (>1,500 mL).

For surgical procedures other than hysterectomy and laparotomy, prophylaxis may not be warranted.3 However, when the patient is markedly obese, many surgeons, including me (Dr. Perkins), sometimes opt to give antibiotics anyway—except for laparoscopic procedures—primarily for wound healing.

Compromised operative exposure

One of the main challenges of surgery in the obese is achieving adequate exposure; when it is inadequate, inadvertent injury may occur.

In addition to a thick abdominal wall composed largely of adipose tissue, these patients frequently have significant accumulations of fat in the mesenteries of the bowel, omentum, and pelvic peritoneum. These accumulations make it difficult to navigate around what becomes a narrow operative field.

Exposure can also be limited in vaginal surgery, because many obese women have very large thighs, buttocks, and accumulations of perineal fat.

Because exposure is a key element of successful surgery, modification of the procedure often becomes necessary—eg, focusing on a single area of the operative field at a time.

Use of a special retractor may help. A self-retaining retractor can be extremely useful. The Bookwalter retractor, first described in 1980, is a commonly used, table-fixed system that attaches to the side rail and can be assembled in minutes (FIGURE 1).4 The variety of rings and blades allows for excellent exposure. Although several complications have been associated with use of the Bookwalter retractor (primarily colon perforation and neuropathy5), they are infrequent and can be minimized by selecting the appropriate blade size and periodically repositioning the blades.

When this or other table-fixed retractors are unavailable, two Balfour retractors, placed at opposite poles of the field to obtain satisfactory exposure, may suffice. With a morbidly obese patient, multiple assistants may still be required to facilitate optimal exposure.

FIGURE 1 A tool to increase exposure

This self-retaining Bookwalter retractor is fixed to the surgical table and features a variety of rings and blades to facilitate exposure.

Thromboembolism

Venous thromboembolism is a major cause of mortality and morbidity in hospitalized patients, causing approximately 60,000 deaths every year.6 Obesity increases the risk of deep venous thrombosis in patients undergoing pelvic surgery. Because of their weight—and, often, coexisting conditions such as cardiorespiratory disease—many obese women are inactive or minimally active postoperatively, increasing the risk of thromboembolism, which remains heightened as long as 3 weeks after discharge. Older women are also at high risk, as are those with a malignancy.

Current guidelines call for the application of a pneumatic calf-compression device in the operating room, with removal after the patient is fully ambulatory. I (Dr. Perkins) also advocate simultaneous use of low-dose heparin, which should be given before surgery and continued until discharge.

Although the use of unfractionated heparin in conjunction with spinal or epidural anesthesia is not a major concern, the use of low-molecular-weight heparin warrants consultation with the anesthesiologist. Unfractionated heparin is preferred because it is metabolized much more rapidly than low-molecular weight heparin.7 The main concern with use of heparin in this setting (regardless of the patient’s weight) is spinal hematoma formation.

Inadvertent injury

Because exposure tends to be limited in obese patients, there is an ever-present risk of injury to bowel, bladder, ureter, and vascular structures. In obese women with a history of abdominal surgery, adhesions are likely, and the risk of bowel injury is increased. Similarly, in obese patients undergoing a laparoscopic procedure, many surface landmarks and vessels may be hard to discern.

Consider preoperative bowel preparation when there is a high risk of intestinal injury.8

Panniculectomy: Old technique with a new surgical purpose



Use a scalpel to incise the skin and delineate the area to be excised. That area typically consists of a large wedge of abdominal skin and subcutaneous fat.

Although the addition of panniculectomy to gynecologic surgery in the morbidly obese patient is a fairly recent strategy to increase exposure, the procedure itself has roots in the 19th century. In 1910, Howard Kelly of The Johns Hopkins Hospital reported a lipectomy that involved excision of a large wedge of abdominal skin and fat,21 although indications for that lipectomy appear to have been grounded in cosmesis and personal comfort for the patient.

Technique

Panniculectomy involves excision of a large portion of abdominal skin and subcutaneous fat down to, but not including, the rectus fascia, to gain much greater exposure to the lower abdominal cavity and pelvis.

Once the segment to be excised is delineated, it is mobilized using electrocautery to achieve meticulous hemostasis. After all surgical procedures are completed, the abdominal wall is closed in multiple layers, and drains are placed in the subcutaneous layer. Surgeons who have performed this procedure report significantly increased exposure and access to pelvic structures.



Once the skin is incised, the wedge is mobilized using electrocautery, down to, but not including, the rectus fascia.

Risks

The most important risk is impaired healing of the abdominal wound. One study of this procedure in patients on a gynecologic oncology service noted wound complications in 35% of patients, as well as significant blood loss (up to 1,800 mL in one case).22 Another study by Hopkins and associates,23 however, reported minimal blood loss and wound complications.

Caveats

The procedure requires an experienced surgeon, particularly if no plastic surgeon is readily available. Also, when counseling the patient about this procedure, it is important to emphasize that its primary indication is to maximize exposure; cosmetic benefits are secondary.

Impaired cardiorespiratory function

Pulmonary function typically is compromised in the markedly obese, with restrictive lung disease and reduced functional residual capacity. If the patient smokes or has chronic obstructive lung disease, her pulmonary function is compromised even further, and her condition should be relayed to the anesthesiologist.

In addition, many obese patients have preexisting heart disease or conditions such as hyperlipidemia that put them at risk for heart disease. When evaluating an obese surgical patient, also ask about less apparent disorders, such as sleep apnea, which, if not addressed, may have grave postoperative consequences.

Continued...
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