Care of the Critically Ill Bariatric Patient-4 Nursing CEs

Author: Brooke Baldwin-Rodriguez, RN, MSN, WCC

Written: August 30th, 2007

Updated: September 11, 2009

Course Description

The epidemic of obesity in the United States creates the need for critical care nurses to understand the physiologic needs and the psychosocial needs of this patient population. This course will define and describe obesity so that students will have the background to identify and treat the consequences of obesity in the critically ill patient. The second part of this course will focus on how obesity affects the care and management of the critically ill patient by reviewing the effects of obesity on the body systems. The top reasons patients with obesity are admitted to the critical care area will be highlighted. The last part of this course will focus on the issues that affect the critical care nurses who care for the obese patient as well as safety for the obese patient while in the intensive care unit.

Course Objectives

• Define obesity
• Identify body mass index and the correspondence to obesity
• Define common terms associated with obesity
• State the prevalence of obesity in the United States
• Identify the most 3 common reasons patients who are obese are admitted to the Intensive Care Unit
• Identify the physiologic changes associated with obesity
• List the consequences of physiologic changes when caring for the critically ill obese patient
• Describe concerns for caregivers caring for obese patients
• Identify equipment that may help in caring for the critically ill obese patient
• Identify safety concerns for the obese patient in the intensive care unit

Definition and Description of Obesity

Obesity is a complex and multifaceted disease that involves interactions between social, behavioral, cultural, physiological, metabolic, and genetic factors. Obesity is defined as an excess in body fat stores. Generally, obesity is treated in the physician’s office. Obesity compromises health and leads to early death. Many patients who are obese are admitted to the critical care unit due to the comorbidities associated with obesity. When a patient is admitted to the critical care unit, obesity affects both patient outcomes and how nurses care for the patient.

Body mass index is the most common and accepted method of determining the degree of excess weight or obesity. Body Mass Index is calculated by multiplying the individual’s weight (in pounds) by 703, then, dividing by the height (in inches) squared. This calculation approximates BMI in kilograms per meter squared (kg/m²). There are also BMI charts to help determine a patient’s BMI.

Classifications for BMI, adopted by the Expert Panel on Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, are as follows:

Body mass index is strongly correlated with total body fat content and should be used to monitor changes in body weight. However, caution should be taken when calculating BMI in children, adults with edema, ascites, pregnancy, or individuals with a high ratio of muscle mass because the calculation may not accurately represent the true amount of excess fat tissue. Body circumference indices may also be used to assess for central pattern of obesity versus peripheral distribution of body fat. Central pattern obesity and a waist circumference to hip circumference ratio of > 0.9 in women and > 1.0 in men and is associated with higher risk of morbidity and mortality due to cardiovascular disease, diabetes, breast cancer, and stroke than peripheral pattern of fat distribution.

Some diseases or risk factors associated with obesity place patients at a higher risk for mortality in general. Diseases and conditions that reflect a high risk of mortality include established coronary artery disease, other atherosclerotic diseases, type 2 diabetes, and sleep apnea. Three or more of the following risk factors also reflect a high absolute risk of mortality: hypertension, cigarette smoking, high low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, impaired fasting glucose, family history of early cardiovascular disease, and age (male > 45 years, female > 55 years).

Definitions associated with care of the obese patient include: overweight, obesity, morbid obesity, and bariatrics.

Overweight

Excess body weight compared to established standards, such as BMI > 25-29.9 kg/m². Excess weight may come from muscle, bone, fat, and/or water.

Obesity

Abnormal proportion of body fat. It is possible to be overweight without being obese (i.e. body builder), but many people are both.

Morbid obesity

Lifelong, progressive, life-threatening, genetics-related, multifactorial disease of excess fat storage with multiple comorbidities

Bariatrics

From the Greek baros for “weight”. Bariatrics includes health care related to the treatment of obesity and associated conditions.

Prevalence of Obesity

With an estimated 97 million adults that are overweight or obese, obesity is an epidemic. Healthcare providers must understand the potential consequences and realities of caring for this population since 10% to 25% of people between the ages of 26 years and 75 years are obese and more than 3% to 10% in this age range are morbidly obese. In the last decade the percentage of adults, ages 20 yeas or older, who are in the categories of overweight and obese has increased to 54.9 percent.

Many obese patients may seek treatment late due to impaired mobility, limited transportation options, and embarrassment and, thus, end up being admitted to the critical care units.

Why Care of the Obese Patient is Important for the Critical Care Nurse

Patients who are obese enter critical care units for various reasons. Three common reasons for admission are: acute complications associated with gastric restrictive surgery, factors of the consequences of obesity (i.e. cardiac, vascular, respiratory, endocrine, and immunologic sequelae), and as a result of trauma injury that requires admission to a critical care unit. Due the size and weight of the patient this becomes an important consideration for nurses because the patient may not be able to participate in care because of mobility and ambulation difficulties. Additionally, most hospital equipment is not designed for patients over 350 pounds. Prolonged lengths of stay may also lead to complications and co-morbidities. Co-morbidities associated with obesity include: pressure ulcers, wound infections, respiratory problems, and urinary incontinence. Nursing care must focus on the prevention of the potential complications. Physical assessments, turning, transferring, ambulating, physical care, and pharmacology are aspects of nursing care that are affected, and of special concern, for this patient population.

Review of physiological system effects of obesity

An increase in caloric intake and decrease in physical activity leads to obesity. Excess fat accumulation and the increased size of normal structures and fat deposits interfere with the mechanics of numerous body functions. Obesity is characterized by inflammation, hypercoagulability, and insulin resistance and is considered to be a chronic inflammatory state that diminishes immune and metabolic reserves.

Pulmonary Considerations

Both structural and physiological changes affect the pulmonary system of the obese patient. Structural changes lead to restrictive lung patterns and physiologic changes lead to increased work of breathing.  Functionally, there is a decrease in functional residual capacity, vital capacity, total lung capacity, inspiratory capacity, minute ventilation volumes, and expiratory reserve volumes due to the increase in intraabdominal pressure and the diaphragm pushing up on the lungs. Physiologically, increased pulmonary blood volume and increases in carbon dioxide production lead to an increased work of breathing. These structural and physiological changes lead to what is called “obesity hypoventilation.” Sleep apnea is very common in the obese patient due to airway narrowing from fat distribution in the upper airway and tongue.  Obstruction is commonly due to relaxation of throat structures; the base of the tongue falls against the posterior wall, occluding the pharynx and upper airway and leads to hypoxia.

The end result of sleep apnea for the obese patient may be the failure to breath. As breathing becomes more difficult in general for the patient, the respiratory rate will increase and there is a ventilation/perfusion mismatch. Hypoxemia and respiratory acidosis are the usual results of the ventilation/perfusion mismatch. A large body requires increased oxygen in order to maintain adequate tissue perfusion. Alveolar hypoventilation and sleep apnea may be the main reasons that the obese patient is hospitalized.

Continuous positive airway pressure (CPAP) may be used to treat the obstructive sleep apnea. With CPAP the air flows through a nasal mask against the airway resistance. The air enters the nasal pharynx and pushes the tongue forward, preventing the recurrent obstructive events. Body position will also influence respiratory status. Lying flat or in the Trendelenburg position will increase respiratory problems. Maintaining 30 to 45 degree semi-recumbent position is preferred. Atelectasis and pneumonia may result in shallow respirations. Adequate pain control will result in deeper respirations and more effective coughing, especially if the patient has had surgery.

Regular tracheostomy tubes may be too short to fit the obese patient. Using an extra long tracheostomy tube may be required. Tracheostomy ties may cause skin irritation and burrow into the skin. Tissue erosion can occur if ties are applied too tightly, so foam tracheostomy ties may provide better protection against tissue erosion.

When an obese patient has respiratory failure and requires a mechanical ventilator the delivered tidal volume should be calculated based on ideal body weight (IBW) rather than actual body weight (ABW) to avoid high airway pressures, alveolar over-distention, and barotraumas. The obese patient may have higher peak and static airway pressures than are usually recommended, but these may be necessary in order to oxygenate and have adequate alveolar ventilation. Positive End Expiratory Pressure (PEEP) may be needed to prevent closure of the alveoli and cause atelectasis.

Ventilatory discontinuance may become more difficult. Increased time on the ventilator leads to an increased risk of ventilator associated pneumonia and aspiration pneumonia. The reverse trendelenberg position at 45 degrees may facilitate discontinuing the ventilator in these patients.

Cardiovascular Considerations

Approximately 3 milliliters of blood volume are need per 100 grams of adipose tissue to maintain perfusion. Due to the increase in adipose tissue with obesity, circulating blood volume increases, preload increases, stroke volume increases, cardiac output increases, and myocardial workload increases in order to meet the perfusion demands. In order to increase circulating blood volume there is increased red blood cell production which causes increased blood viscosity. Increased blood viscosity leads to an increased risk for thrombophlebitis and thromboembolism.

Hyperinsulinemia in the obese patient can lead to sodium retention and, as a result, the obese patient develops hypertension. Other body processes that contribute to heart disease include increased triglyceride levels and reduced high-density-lipoprotein (HDL) cholesterol. Elevated circulating concentrations of catecholamines, mineralocorticoids, renin, and aldosterone usually lead to increased afterload, further contributing to heart disease. Cardiac disease associated with obesity eventually causes myocardial hypertrophy and decreased myocardial compliance. Diastolic dysfunction and ventricular failure can lead to sudden cardiac death.

When admitted to critical care units, pulmonary artery catheters may be need in the obese patient due to poor fluid tolerance that occurs with diastolic dysfunction to closely monitor hemodynamic status.

Beta-blockers should be used cautiously in obese patients due to the impaired ventricular contractility as a result of decreased beta adrenergic receptors.

Renal Considerations

Urinary and fecal incontinence are more common in the obese patient due to increased intra-abdominal pressure from excess abdominal weight. Limited mobility may contribute to incontinence because the patient is unable to ambulate or urinate independently.

Metabolic/Endocrine Considerations

Weight gain is associated with an increased demand for insulin and may result in pancreatic failure. Increased food intake may also be associated with an increase in T3 (triiodothyronine) produced from T4 (thyroxin), and lead to an increase in metabolic rate, causing an increase in cardiac output.

Metabolic X syndrome is common in the obese population. This syndrome is a culmination of insulin resistance, hyperinsulinemia, hyperglycemia, coronary artery disease, hypertension, and hyperlipidemia. Increased metabolic rate, accelerated net protein breakdown, and alterations in lipid and carbohydrate metabolism of critical illness exacerbate the preexisting metabolic problems for the obese.

Hemotalogic/Immune Considerations

One source of tumor necrosis factor and interleukin-6 is adipose tissue. As a patient becomes obese, the adipose tissue produces more of these inflammatory mediators. Another immune consideration is that neutrophils have impaired chemotaxis and activation, causing alteration is response to infection.

Gastrointestinal/Nutritional Considerations

Obese patients have an increase resting energy expenditure secondary to increased BMI.

Altered gastric pH and fluid volume have been found in obese surgical patients.

Aspiration risk is increased in the obese patient due to the higher volume of gastric fluid, a lower than normal pH of gastric fluid in fasting obese patients, increased intra-abdominal pressure, a higher incidence of gastroesophageal reflux, and a higher incidence of hiatal hernia.

Obese patients in intensive care units are likely to develop protein energy malnutrition due to metabolic stress. Traumatized obese patients mobilize more protein and less fat, compared with nonobese patients. In part, this is due to the fact that central adipose tissue is more metabolically active than peripheral adipose tissue, lipolysis and fat oxidation may be blocked. The preferred use of carbohydrates for energy may accelerate the body protein breakdown. The increased carbohydrate use for fuel increases the respiratory complication and increase in CO2 production. Increased incidence of diabetes mellitus in the obese population will often result in hyperglycemia and should, therefore, be monitored carefully. Insulin infusions may be necessary due to the difficulty in controlling blood sugars with a sliding scale.

Calories for nutrition in the intensive care unit should be given primarily as carbohydrates with fats to prevent essential fatty acid deficiency. Nutrition should not be withheld due to the belief that losing weight during critical illness will be beneficial to the patient. Enteral nutrition is the preferred route of feeding and is only contraindicated in patients with bowel obstruction.

Musculoskeletal/Integumentary Considerations

Obese patients have increased concentrations of fibrinogen and plasminogen activator inhibitor-1 and decreased concentrations of antithrombin-III and decreased fibrinolysis. The result is an increased risk of developing deep vein thromboses due to increased blood viscosity. Prevention of deep vein thrombosis should be a priority. Low-molecular weight heparin (LMWH), oral anticoagulation or the combination of pneumatic compression and LMWH should be considered for prophylaxis.

Obese patients often have chronic dermatitis in skin folds. Perineal skin breakdown can occur as a result of immobility, the inability to get to the bathroom, and the inability of the patient to adequately clean the perineal area. For men, it may be difficult to use the urinal due to problems of either sitting on the side of the bed or standing at the side of the bed. Catheterization of the obese patient may be difficult for the nurse and assistance if often needed for correct insertion technique. When an obese patient develops a wound the healing of the wound may occur more slowly due to the increase in adipose tissue which is less well vascularized. Wounds that develop in skin fold areas may be more prone to infection due to the moisture build up and the accumulation of bacteria.

Pharmacology

Obese patients react differently to medications due to a high percentage of adipose tissue and lower percentage of water and lean body mass. Medications are absorbed differently due to body composition. Drug levels may become sub-therapeutic or toxic.

Drugs that are highly soluble in fat and distribute mostly in adipose tissue include:

o       Carbaniazepine

o       Diazepam

o       Propofol

o       Opiate analgesics

Drugs that are highly soluble in adipose tissue should be calculated using the patient’s actual body weight. Drugs that are lipophilic need an increase in dose, but the half-life and the elimination rate is prolonged.

            Drugs that are mainly distributed in lean tissue include:

o       Acetaminophen

o       Dioxin

Drugs that are mainly distributed in lean tissue should be dosed according to ideal body weight to avoid toxicity.

Longer needles may need to be used in the ob

Page 2 |