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Is It Safe to Operate on Obese Patients Who Need Lumbar Spinal Fusion Surgery?

You may have heard of someone being turned down for surgery because they were overweight or too heavy. Maybe this has even happened to you. Is it really justified? Are patients really at increased risk for problems during and after surgery just because they are obese? Is there any evidence to support this kind of guideline?

In this study, surgeons focus on obese and morbidly obese patients with low back pain who are having a lumbar spinal fusion. They looked at complications, final outcomes, and effect on body weight of having spinal fusion surgery in 63 patients who were considered obese.

Obesity is determined by a measure called the body mass index (BMI). A person's BMI can be calculated using a mathematical equation of the ratio between height and weight. Anyone with a BMI of 30 kg/m2 or higher is classified as obese.

Morbidly obese is a separate category for those individuals who are 20 per cent or more above the optimal weight for their height and body type. Their BMIs can exceed 40 kg/m2. Patients with a lower BMI (35 to 40 kg/m2) can also be considered morbidly obese if they have one or more significant comorbidities. Comorbidity refers to other health problems such as diabetes, heart disease, high blood pressure, asthma, sleep disorders, and so on.

What are the surgical team's concerns about operating on someone who is medically obese? There can be difficulties getting a clear airway to allow the patient to breathe while being anesthetized. Folds of fat and flabby soft tissue collapse against the airway preventing intubation (placement of a breathing tube down the trachea).

It can be equally difficult to gain access to a blood vessel to start an intravenous (IV) line. Positioning the patient can be a tremendous challenge. And studies have confirmed the link between obesity and the increased incidence of complications (including death) during and after the surgery.

Back pain patients who are obese have a special dilemma. They can't lose weight because they can't exercise. They can't have bariatric surgery such as stomach banding or gastric bypass procedures because of the back pain. They are really caught in a catch-22 situation. There is an assumption that if they didn't have back pain, then they would exercise and lose weight. Is that really the case? That's one of the things the authors of this study put to the test.

All the patients in this study had a BMI of 30 or higher and one or more (up to six) levels of lumbar vertebrae fused. There were different reasons why these patients had chronic low back pain requiring lumbar spinal fusion. Lumbar canalstenosis (narrowing of the spinal canal), degenerative disc disease, scoliosis, and instability after a previous (laminectomy) surgery were the most common problems. Laminectomy refers to the removal of a section of vertebral bone called the lamina. Cutting away the bone helps take pressure off the spinal cord or spinal nerve roots.

Data collected on this group of patients included time in surgery, blood loss during surgery, and length of hospital stay. Information on the number and type of preoperative comorbidities and postop complications was also summarized. Pre- and post-study weights were recorded. Follow-up lasted at least 18 months for everyone. Some people were followed for as long as three years.

Weight loss was not a part of the pre- or post-operative plan. The study did not include any counseling or effort in this direction. It was noted that almost everyone in the study had attempted one (if not many more) efforts to lose weight (unsuccessfully).

The authors reported that surgery did not take longer in patients whose BMIs were higher. The surgical time was really linked with the number of segments fused. Blood loss was linked with several factors including body weight, number of levels fused, and preoperative hemoglobin levels. Positioning may have an impact on blood loss in the obese population because pressure on the belly can cause greater blood loss. Whenever possible, the patient should be placed in such a way that the abdomen hangs free.

No one had a net loss of weight as a result of their lumbar spinal fusion. This was true despite the fact that they did report reduced pain levels. Early on after surgery, about half the group gained weight while the other half lost weight. A few stayed the same. Over time, the BMI did not change significantly for anyone in the study.

Complications after surgery such as infection (wound, skin, urinary tract), nonunion, spinal fluid leaks, and low blood pressure were as high as 50 per cent. But the rates were not higher among the morbidly obese patients compared to the obese patients. The authors explained that they included minor and major complications, so the overall number of problems (referred to as the complication rate) was possibly inflated by the definition of complication.

The authors conclude that anyone with a BMI of 30 or higher requires careful consideration and monitoring when having surgery. The surgeon must go into the lumbar spinal fusion procedure with the knowledge that obese patients have a greater risk of postoperative complications. These problems may not be related to their body size as much as the number of segments being fused. Overall results may be better if the obese or morbidly obese patient has bariatric surgery first before spinal surgery.


Rahul Vaidya, MD, FRCSC, et al. Lumbar Spine Fusion in Obese and Morbidly Obese Patients. In Spine. March 1, 2009. Vol. 34. No. 5. Pp. 495-500.

03/18/2009

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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