Trauma in patients who are morbidly obese

AORN Journal,  Oct, 2002  by Susan Bushard

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Obesity is a health problem in wealthy nations such as the United States. The problem affects society in monetary terms. It costs $68 billion per year to treat the chronic medical conditions associated with morbid obesity. (1) Obesity increases the risk of significant alterations in cardiac and pulmonary systems and adds to the difficulty of recovering from physical trauma.

Morbid obesity, defined as a body mass index (BMI) greater than 40, is confined to about 10% of the US population; (2) however, this portion of the population challenges the health care industry because patients who are morbidly obese are more difficult to treat than patients who are not. When a trauma victim is morbidly obese, more than the skill level of the trauma team is tested.

BACKGROUND

Trauma is the fifth leading cause of death after cancer and lower respiratory diseases in the United States. (3) Other statistical analysis reveals that blunt abdominal trauma is the third leading cause of trauma death after head and chest injuries. (4) The mortality rates of trauma victims who are morbidly obese are eight times higher than the rates of victims of normal weight (ie, less than 25 body mass index). (5)

Those involved in trauma care are seeing decreased mortality rates among patients of normal weight; however, trauma centers are struggling to adjust to the growing number of patients who are morbidly obese. They must purchase or adapt equipment and supplies, and personnel must change personal attitudes toward patients who are obese.

PATIENT ASSESSMENT

Patients who are morbidly obese present a challenge to every aspect of trauma care. Initial and ongoing assessment of trauma victims who are not obese can be difficult; in very large patients, some assessment protocols must be changed or cannot be followed at all.

Trauma care involves the use of basic assessments and procedures. These basics involve airway, breathing, circulation, disability, and environment. (6) When caring for patients who are morbidly obese, these aspects of care are not routine because size and lack of landmarks make assessment difficult, and chronic conditions add to the assessment puzzle. Airway and breathing mechanisms are compromised in patients who are morbidly obese for the following reasons.

* Excess adipose tissue creates an increase in workload for supportive muscles, which results in a cascade of other problems.

* Oxygen consumption and carbon dioxide production increases.

* Myocardial compliance decreases (ie, 35% of normal).

* Breathing effort increases, and efficiency of air exchange decreases.

* Resting functional residual lung capacity decreases.

* The incidence of gastroesophageal reflux, hiatal hernia, and abdominal pressure increases, which adds to the risk of aspiration. (7)

Any injury that compromises a patient's ability to maintain an airway puts that patient at risk for complete airway loss. For example, masking a patient who is morbidly obese is difficult because of the need for high pressure to overcome the weight of the chest and abdomen when the patient is supine. If masking is inadequate and intubation is required, endotracheal intubation and cricothyrotomy may be extremely difficult due to lack of landmarks and redundant tissue.

The cardiovascular system in patients who are morbidly obese is compromised, which further reduces their ability to withstand the shock of trauma. Excess body weight compromises the cardiovascular system by

* increasing metabolic demand and cardiac output;

* increasing blood volume, although as a percentage of body weight, blood volume may be as low as 45 mL per kg;

* increasing stroke volume index and stroke work index in proportion to body weight, which can lead to lea ventricular dilation and hypertrophy; and

* causing hypoxia and hypercapnia, which can lead to pulmonary vasoconstriction and, in turn, to chronic pulmonary hypertension and right-sided heart failure. (8)

Identification of circulatory problems is difficult because of the lack of oversized equipment. Taking blood pressure may not be possible because cuffs sized for patients who are morbidly obese may not be available. Blood pressure may be assessed at the forearm using a leg-sized blood pressure cuff; however, the readings may be unreliable.

Normal procedures for identifying internal bleeding cannot be used on patients who are morbidly obese. For example, ultrasound does not penetrate adipose tissue reliably. Diagnostic peritoneal lavage (DPL) is contraindicated because catheters and trocars are too short and other landmarks are not available. If the patient appears to need a DPL, exploratory laparotomy would be the choice of most surgeons to determine whether the patient is bleeding intraabdominally. Computed tomography (CT) scans often cannot be performed due to the weight limitations of the table. Most CT scanners accommodate no more than 250 lbs to 300 lbs. Facilities that specialize in bariatric surgery may have purchased or modified scanners to accommodate greater patient weight.