Anesthetic management and nursing considerations for obese patients

Nursing Obesity

An Overview of Obesity

More and more studies show that increasing numbers of children and adults alike are diagnosed as obese (Levi, Goodman, Poral & Savransky, 2003; Pool, 2001; Bostwick & Melcher, 1998). Obesity may be defined by some as an epidemic, particularly aggressive in Western cultures where upwards of 20% of certain populations are characterized as obese or overweight. There are many side effects of obesity, non -- the least of which include cardiovascular problems, vascular problems and increased mortality rate.

More often patients are turning to surgical interventions including bariatric surgery to reduce body fat and regain a normal weight. There are however a number of risks and complications associated with surgery, particularly with regard to administering anesthesia to obese patients. Anesthetists face many unique challenges when working with obese patients. Obesity and anesthetic related concerns are discussed in greater depth below.

Definition

One may define obesity as a condition where an individual presents with an "abnormally high percentage of body fat" that contributes to the total body mass (Levi, Goodman, Poral & Savransky, 2003). The percentage of body fat qualifying as abnormally high will vary from patient to patient. Fortunately health care officials have defined obesity using a standard set of guidelines and measures.

Obesity is often measured by calculating ones BMI or Body Mass Index. Obesity is often defined as having a BMI equal to or greater than 30, with individuals having a BMI of 40 or more characterized as morbidly obese (Levi, et. al, 2003). Thos with a BMI of 50 or higher are categorized as super obese though most obese patients will fall into the previous two categories (Levi, et. al, 2003).

Patients initially diagnosed as overweight with a BMI close to that of an obese patient often are classified as obese at a later date if no interventions are initiated to control weight gain; others are at risk for obesity in some cases later in life, particularly if overweight throughout adolescence and childhood (Pool, 2001).

Incidence

The number of individuals diagnosed as obese continues to grow at an alarming rate. According to the Centers for Disease Control (CDC) in the United States alone between 1991 and 1998 the number of obese people rose more than 6%, toping more than 11 million (Pool, 2001). Current studies including those conducted by the National Health and Nutrition Examination Survey suggest that more than 22.5 and up to 30% of adults in the United States alone may be obese (Pool, 2001).

Studies suggest that obesity is on the rise in other areas of the world, but is by far the most common problem seen in Western countries (Pool, 2001). The National Institute of Medicine estimated that health care organizations spend more than %70 billion annually to treat obesity and obesity related disorders, and more than 300,000 people die of obesity and co morbid conditions every year (Pool, 2001).

Other recent studies conducted in 2004 and 2005 suggest that obesity has risen to 20%, representing increasing challenges particularly for anesthetists working in drug dosing and management (Casati & Putzu, 2005).

Pathophysiology and Epidemiology Obesity

When energy expenditure falls below caloric intake overweight and obesity often result. While the mechanisms that result in obesity are not entirely understood by physicians most believe that genetic and environmental factors are to blame (Levi, et. al, 2003). Obesity can result in multiple co morbid conditions including increased blood pressure and volume, degenerative joint disease, intra-abdominal pressure disturbances and psychosocial incapacity (Levi, et. al, 2003). Metabolic obesity is linked with energy imbalances resulting primarily from caloric intake excesses (Levi, et. al, 2003). Most metabolic abnormalities associated with obesity related to the pathophysiology of the disease can be traced to caloric disturbances (Levi, et. al, 2003).

Other studies suggest that chronic inflammation often exists in obese patients, particularly those classified as morbidly obese, which may result in increasing complications commonly associated with morbid obesity (Cabay, Deyer & Pellegrinelli, 2001). Other inflammatory syndromes associated with obesity include thrombogenesis, resulting from increased viscosity, fibrinogen and decreased fibrinolysis among other factors (Levi, et. al, 2003).

Chronic elevations of inflammatory hormones in the body can also result in increasing stress to the body's major systems resulting in immunologic and metabolic disturbances (Cabay, Deyer & Pellegrinelli, 2001). These disturbance may in turn elevate the obese patients risk for multiple diseases that ultimately increase patient mortality rates.

Anesthesia Management

In most cases surgical intervention for obese patients should be considered only as a last result after other methods including dieting, drug therapy, psychotherapy and exercise have failed (Levi, et. al, 2003). Multiple complications are associated with surgical intervention and anesthesia use in obese patients. Complications may include an increased risk for adverse cardiovascular problems, increase pulmonary risks, increased risk of thromboembolic events, postoperative infections and higher morbidity rates (Levi, et. al, 2003).

Other complications that may arise specifically from surgery include bleeding related to spleen injury, injury to GI tract including esophageal tears or lacerations (Levi, et, al 2003). Obesity is often an exclusion criterion for most anesthetics, due to prolonged anesthetic needs and extended weaning periods (Levi, et. al, 2003). More commonly used drugs for sedation include benzodiazeprines and propofol (Levi, et. al, 2003). Significantly prolonged or cumulative effects are possible in obese patients.

Physiological changes and pharmacokinetic implications exist for obese patients and the anesthesiologist working with them (Casati & Putzu, 2005). Obesity increases fat and lean body mass, with fat tissue increasing at a rate higher than lean body mass, which can affect the distribution of anesthesia based on the lipid solubility of the drug (Casati & Putzu, 2005). Loading doses are often necessary and must be adjusted based on a patient's weight (Casati & Putzu, 2005). Dosages of pharmacokinetic agents are often based on ideal rather than actual total body weight (Casati & Putzu, 2005). Drug dosing is often based overall on the "volume of distribution for the loading dose and on the clearance for maintenance, with volume of distribution being increased if drug is distributed among lean and fat tissues (Casati & Putzu, 2005).

Coe, Saleh, Samuel & Edwards (2004) report that multiple problems related to anesthesia and obesity exist. The level of obesity defined by MBI has a significant impact on the type of anesthesia most patients choose (Coe, et. al, 2004). Recent studies have focused on encouraging patients to lose a certain amount of weight prior to surgical intervention to make anesthesia delivery a more viable and safe option (Coe, et. al, 2004). Unfortunately most patients undergoing bariatric surgery have utilized all other resources thus must risk any potential contraindications associated with anesthetic delivery in order to lose weight.

Conclusions

Obesity is a complicated and rapidly advancing disease affecting millions of people every year. There are multiple environmental and genetic factors that may contribute to obesity. Obese patients are more at risk for co morbid conditions and complications with surgery particularly when anesthesia must be delivered. In most cases patients would benefit from losing weight prior to surgery.