Laparoscopic surgery in the obese: Safe techniques
Increases in atelectasis, wound infection, and other risks after laparotomy point to laparoscopy as the safer route.
IN THIS ARTICLE
Gynecologic laparoscopy in the obese? What was once the purview of the very talented or the foolhardy may now be the preferred surgical approach.
Obese women who undergo laparoscopy recover faster, with less pain, fewer wound infections, and shorter hospital stays than with laparotomy. Though it is true that obesity increases operative time and the risk for conversion to laparotomy, little evidence supports the theory that a body mass index (BMI) of 30 kg/m2 or higher should exclude laparoscopy.
Unique elements of the physical
It is important to identify central obesity, which is more difficult to accommodate than distribution around the hips. Unfortunately, the roughly 40 million obese Americans tend to have central fat distribution.1,2
In central obesity, the subcutaneous tissue is thick, often requiring extra long ports to attain peritoneal access.
The relationship of the umbilicus to the underlying aortic bifurcation also shifts more caudally. This relationship should be noted and planned for before going to the operating room (FIGURE).
Abdominal obesity in particular confers additional risks during all types of surgery: higher rates of atelectasis, thromboembolism, cardiovascular dysfunction, and wound infection.
Closely inspect the skin and panniculus after a routine examination. Obesity predisposes patients to dark, moist, anoxic spaces beneath folds of skin that need to be identified and inspected for evidence of fungal or bacterial infection. To optimize postoperative wound healing, treat any preexisting infections before surgery.
Cigarette smoking further burdens pulmonary mechanics and oxygenation during surgery, so it is important to encourage smokers to kick the habit at least 8 weeks before elective surgery.3
In general, use the history and physical examination to focus on the recognized risk factors of obesity, with specific emphasis on hypertension, coronary artery disease, arrhythmia, pulmonary obstructive disease, peripheral vascular disease, diabetes, gastric reflux, and arthritis.4
Special tests and laboratory studies
EKG and chest x-ray. In morbidly obese patients (BMI >40), preoperative evaluation includes an electrocardiogram (EKG) and chest x-ray to identify any cardiomegaly, arrhythmias, and occult ischemia or conduction blockage.
Arterial blood gas sampling. Given the higher risk of postoperative thrombotic events in obese patients, it can be helpful to assess preoperative oxygenation and ventilation/perfusion status via arterial blood gas sampling. The obese may have elevated baseline Aa gradients, which, if not noted prior to surgery, can confuse later management of suspected pulmonary emboli.
During testing, assess venous access and counsel the patient if central venous line placement may be possible at surgery. Though central line placement is not routinely recommended, it may be warranted in patients with particularly difficult peripheral venous access.
Skip pulmonary function testing because the results rarely change surgical management. We consider its routine use to be wasteful.
Laboratory evaluation should include betahuman chorionic gonadotropin (in premenopausal patients), complete blood count, electrolytes, glucose, renal function, and type and screen.
Spell out risks at informed consent
The preoperative appointment is your chance to answer questions the patient may have and clearly delineate the risks and benefits of surgery. During this discussion, spell out the increased risks of conversion to laparotomy, prolonged anesthesia, postoperative thrombosis, wound infection, and pulmonary complications, and make sure all are listed on the written consent form.
Complete bowel preparation is recommended the evening prior to surgery, since intraabdominal visualization can be difficult and conversion to laparotomy may be necessary. Bowel prep decompresses the lumen, improving visualization and the outcome of any bowel injury.
Preoperative histamine receptor blockade is recommended for optimal results, since higher body mass can lead to increases in low pH gastric volume and difficulties with intubation. 5 A typical regimen is 50 mg intravenous (IV) ranitidine 20 minutes prior to surgery.
Beta blockade. All patients with hypertension or a history of coronary artery disease should receive preoperative beta blockade, assuming there are no contraindications such as reactive airway disease or cardiac conduction block. Atenolol 10 mg IV 20 minutes prior to surgery is a standard initial dose. All patients already taking beta blockers should simply continue their home regimen through the day of surgery with small sips of water.
INTEGRATING EVIDENCE AND EXPERIENCE
Zeroing in on pneumoperitoneum
What are the effects of pneumoperitoneum and posture in obese women undergoing gynecologic laparoscopy? A recent study13 compared 8 morbidly obese patients with 9 normal-weight controls and confirmed previous evidence that morbidly obese, supine, anesthetized patients have a 68% increase in inspiratory resistance and a 30% decrease in static pulmonary compliance, compared with controls. Pneumoperitoneum further increases this resistance and diminishes compliance.
Oxygenation is not affected
Somewhat surprisingly, this study did not detect significant changes in respiratory mechanics with head down or up positioning, and despite the exacerbation of pulmonary mechanics with pneumoperitoneum, there was no significant change in oxygenation.
The conclusion: While pneumoperitoneum impairs respiratory mechanics during anesthesia in the obese, body mass is the only variable that significantly affects oxygenation. If an obese patient can tolerate anesthesia and supine positioning—necessary for both laparoscopy and laparotomy—she is likely to tolerate changes in position and pneumoperitoneum as well.
These findings also hold true in patients undergoing bariatric surgery,14 with no significant differences in respiratory mechanics or arterial oxygenation during either laparoscopic or laparotomic surgery.
Virtually all procedures are safe
In gynecology alone, practically all of the procedures commonly performed in women of normal weight have been studied and found to be safe in obese patients. They include adnexal surgery, myomectomy, total laparoscopic hysterectomy,15-18 management of tubal ectopic pregnancy,19 endometrial cancer,20 and pelvic/periaortic lymph node dissection.20,21
Two ways of comparing outcomes
Well-designed studies tend to fall into 2 camps: those that compare laparoscopy in obese patients with laparoscopy in nonobese patients, and those that compare laparoscopy in obese patients with laparotomy in obese patients.
- A review of the gynecologic literature in the first camp15-18,22-24 reveals little to no difference between cohorts with respect to estimated blood loss, operative and postoperative complications, and hospital stay. The nongynecologic literature on laparoscopy in obese versus nonobese patients tends to corroborate these findings, with an overall trend toward increased operating times and conversion rates.25-30
- In comparing laparoscopy with laparotomy, researchers found that total operative time tends to rise with laparoscopy.20,21,31 Otherwise, laparoscopy confers benefit or no difference with respect to hospital stay, postoperative pain, estimated blood loss, lymph node counts, postoperative complications (fever, ileus, wound infection), convalescence, and total medical cost.32,33
Antibiotics. The high rate of postoperative wound infection in obese patients makes preoperative antibiotic treatment logical. Although we were unable to find any studies demonstrating the benefit of routine antibiotic prophylaxis in obese patients undergoing laparoscopy, data do show a benefit when laparotomy is performed.
If no allergies or contraindications exist, give 1 to 2 g of a first-or second-generation cephalosporin intravenously 20 to 30 minutes prior to anesthesia induction.
Sequential compression devices. Since both obesity and gynecologic surgery are risk factors for deep venous thrombosis, use large sequential compression devices on the lower extremities, beginning before induction of anesthesia.
Position the patient for optimal access
Only 1 recent publication explores this issue in obese laparoscopy patients. Lamvu et al5 advocate the armstucked (“military”), low lithotomy position, with liberal padding on the legs and arms and a gel pad under the lower back. They also recommend stationary shoulder blocks to help maintain positioning in the Trendelenburg (head down) position, and they use clamps, gauze, weights, and tape to maintain the panniculus in its caudad position.
Novel technique realigns umbilical axis. We, too, use padding liberally on all pressure points, but do not weight the panniculus. In fact, we prefer its cephalad migration in the Trendelenburg position. Pelosi and Pelosi6 describe a useful technique to realign the umbilical axis cephalad before placing the first trocar (FIGURE). Once the Trendelenburg position is attained (after initial trocar placement), this cephalad position eases ancillary port placement.
Tucking 1 arm facilitates surgery, anesthesia access. Tucking both arms is ideal but not always feasible. It is especially problematic when adipose tissue surrounding the biceps makes the military position impossible. Further, anesthesiologists may be unwilling to abandon access to the peripheral intravenous site, since placement and emergency replacement can be difficult.
Central venous access is always an option but is not without risk and should be avoided, if possible. A creative alternative: Tuck the nonaccessed arm at the patient’s side and place the other arm over the chest. Maintain this position by tucking a sheet over the chest. This gives the anesthesia team access to 1 arm while facilitating ideal surgeon positioning.
Do not use shoulder blocks when the patient’s arms are extended, as this increases the risk of brachial plexus injury should the patient slide.
Success hinges on port placement, pneumoperitoneum
The success or failure of most laparoscopic surgeries is determined in the initial minutes during placement of the operative ports. This is especially true in obese patients. No single variable is more important to successful laparoscopy in obese patients than the establishment of pneumoperitoneum.
Entry variables of 3 body types. Obesity increases the distance between skin and fascia, and can increase the distance between fascia and peritoneum. The difficulty of placing the Veress needle or trocar into the peritoneal cavity increases with this distance. Preperitoneal insufflation of gas exacerbates the problem. In addition, dissection to the level of the fascia for an open (Hasson) approach sometimes requires incision extension and increases the risk of postoperative wound infection.
Obesity also changes the relationship of the umbilicus to the aortic bifurcation. Utilizing computed tomography, Hurd et al7 demonstrated that the umbilicus migrates caudally in relation to the aortic bifurcation as the BMI increases. In nonobese patients (BMI <25), the umbilicus had a median location 0.4 cm caudal to the bifurcation, but in 33% of patients the umbilicus was actually cephalad to the aortic bifurcation. In overweight (BMI 25 to 30) and obese (BMI >30) patients, the umbilicus had a median location 2.4 and 2.9 cm caudal to the aortic bifurcation, respectively. However, in both groups, the umbilicus was directly over the aortic bifurcation in 30% of patients.
The same group of researchers, again using computed tomography, demonstrated that the distance between the umbilicus and peritoneum at a 45° angle from the umbilicus into the pelvis, in both nonobese and overweight patients, was only 2 cm. In obese patients, this distance increased to a median of 12 cm. Hurd et al8 also noted that the distance between the umbilicus and the underlying vessels was only 6 cm at a 90° angle in nonobese patients, but averaged 13 cm in obese patients.
To optimize intraperitoneal Veress needle and trocar placement while minimizing risk to the underlying vasculature, Hurd and colleagues recommend a 45° angle from the umbilicus toward the pelvis in nonobese patients and a 90° approach in obese patients. In overweight patients, the approach should range between 45° and 90° (TABLE 1).