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1994 SECTION 26: Special Situations TABLE 297-15 Complications After Cardiac Transplant Complication Comments Altered physiology See text in “Cardiac Transplantation” section. Dysrhythmias Dysrhythmias after transplantation are frequently due to rejection. Treat the unstable patient presenting in extremis with 1 gram of methylprednisolone IV; delay rejection therapy in the stable patient for consult with the transplant team and biopsy. Atropine and vagal maneuvers have no effect due to denervation. Adenosine should be provided at half the normal dose in supraventricular tachycardia. Sinus node dysfunction Pacemaker usually required. Pulmonary complications Diagnosis may require CT or more invasive diagnostic procedures.Pneumonia Thromboembolic disease Exercise-induced hypoxemia Pneumothorax Interstitial fibrosis Cardiac ischemia Patients do not experience pain due to denervation; symptoms typically occur with complications such as congestive heart failure. Rejection Presents a variety of ways: dyspnea, syncope, orthopnea, palpitations, edema. Cardiac biomarkers typically elevated. Often presents with dysrhythmias and findings of heart failure. Treat the patient presenting in extremis; withhold treatment for biopsy if possible. Infection See section “Posttransplant Infections.” Congestive heart failure Echocardiography can help to determine etiology and therefore ideal treatment. Ischemic stroke and intracranial hemorrhage Increased risk after heart transplant. Complications specific to ventricular assist devices Increased risk of infection and thromboembolism. Cardiac allographic vasculopathy Beyond 1 y after transplant, one of the major causes of graft failure due to rapid atherosclerosis. Pediatric heart transplant recipients are at risk for graft coronary artery disease and ischemia. May occur with no symptoms or fulminant heart failure. Diagnosis includes angiography. May require retransplantation. immunosuppression. Reasons for graft failure include corneal graft rejection (30.9%), corneal endothelial cell failure (21.0%), glaucoma (8.5%), and other causes (26.2%). 104,105 Ophthalmology consultation is required for any change in visual acuity or other ocular signs or symptoms in a patient with a corneal transplant. Corneal graft rejection is a specific process in which a graft that has been clear suddenly develops graft edema with anterior segment inflammatory signs. Rejection can occur at any time starting at 10 days after transplant. The inflammatory process starts at the graft margin nearest to the most proximal blood vessels and then moves toward the center to involve the entire graft. 104 Signs and symptoms include eye pain, photophobia, corneal or scleral injection, and decreased visual acu ity. Examination may reveal unilateral anterior chamber reaction with keratic precipitate or corneal edema in a previously clear graft. Late graft failure can present with gradual onset of graft edema with no associated inflammation or keratic precipitates. Treatment includes topical or sys temic steroids, cycloplegics, and immunosuppressive drugs such as local and systemic cyclosporine A and tacrolimus. Wound dehiscence can occur early or late after corneal transplanta tion as a result of infection or after eye trauma. Trauma may be unrec ognized or be a result of events such as motor vehicle airbag deployment or a fall with the patient’s glasses impacting the eye.

as local and systemic cyclosporine A and tacrolimus. Wound dehiscence can occur early or late after corneal transplanta tion as a result of infection or after eye trauma. Trauma may be unrec ognized or be a result of events such as motor vehicle airbag deployment or a fall with the patient’s glasses impacting the eye. There may be globe rupture, slight separation of part of the suture line, or just broken sutures. Viral,104 bacterial, 106 or fungal 107 infection can threaten the transplanted cornea. In patients with a history of herpetic keratitis, consider recurrence and examine with fluorescein for characteristic corneal staining and signs of anterior chamber inflammation. 104 Ophthalmology consultation is needed for diagnosis and treatment. Acknowledgment: The authors thank J. Hayes Calvert for his work on the previous edition of this chapter. REFERENCES The complete reference list is available online at www.TintinalliEM.com. CHAPTER The Patient With Morbid Obesity Joanne Williams INTRODUCTION AND EPIDEMIOLOGY Since 1980, worldwide obesity has more than doubled. In 2008, more than 1.4 billion adults, age 20 and older, were overweight. Of these, over 200 million men and nearly 300 million women were obese. Sixty-five percent of the world population resides in countries where overweight and obesity kill more people than underweight. In 2010, more than 40 million children under the age of 5 were overweight. In children, an age- and sex-specific percentile for body mass index (BMI) determines weight status rather than the BMI categories used for adults, because children’s body composition varies as they age and varies between boys and girls. The Centers for Disease Control and Prevention uses a BMI thresh old of above the 85th percentile to define overweight and above the 95th percentile to define obese, compared to children of the same age and sex. 2 The World Health Organization defines overweight as a BMI ≥25 kg/m 2, whereas obesity is defined as a BMI ≥30 kg/m 2.1 Care for bariatric surgery patients is discussed in Chapter 87, “Complications of General Surgical Procedures. ” PATHOPHYSIOLOGY Obesity is an independent risk factor for acute coronary syndrome, especially in those <40 years old. 3,4 Atypical symptoms may pose a problem with acute coronary syndrome diagnosis. 5,6 Approximately 11% of cases of congestive heart failure are attributable to obesity alone. 7 The physical deconditioning of obesity manifests with orthopnea, dyspnea, and lower extremity swelling mimicking acute congestive heart failure. Plain chest radiograph findings of congestive heart failure may be obscured by redundant overlying soft tissue and hypoventilation artifact. Brain natriuretic peptide levels are lower in the obese patient than in the nonobese. 8,9 Cardiomyopathy may affect up to 10% of patients with a BMI >40 kg/m2.10 Obesity is a risk factor for venous thromboembolism11 and its recurrence once anticoagulation therapy is withdrawn.12 The increased prevalence of type 2 diabetes is closely linked to the upsurge in obesity. Excess weight accounts for 90% of type 2 diabetes. 13 Obesity is strongly associated with insulin resistance in normoglycemic persons and in individuals with type 2 diabetes. The accumulation of fat impairs the function of ventilation in obese children and adults. 15-17 Reductions in forced expiratory volume in 1 second, forced vital capacity,15,16 total lung capacity, functional residual capacity, and expiratory reserve volume are associated with increasing BMI. Obesity is a well-recognized risk factor for obstructive sleep apnea. Forty percent of people who are obese have obstructive sleep apnea, and approximately 70% of people with obstructive sleep apnea are obese.

lung capacity, functional residual capacity, and expiratory reserve volume are associated with increasing BMI. Obesity is a well-recognized risk factor for obstructive sleep apnea. Forty percent of people who are obese have obstructive sleep apnea, and approximately 70% of people with obstructive sleep apnea are obese. Increased fat deposition in the pharyngeal area along with reduced operating lung volumes associated with obesity reduce upper airway Tintinalli_Sec26_p1979-2024.indd 1994 8/1/19 1:33 PM

lung capacity, functional residual capacity, and expiratory reserve volume are associated with increasing BMI. Obesity is a well-recognized risk factor for obstructive sleep apnea. Forty percent of people who are obese have obstructive sleep apnea, and approximately 70% of people with obstructive sleep apnea are obese. Increased fat deposition in the pharyngeal area along with reduced operating lung volumes associated with obesity reduce upper airway Tintinalli_Sec26_p1979-2024.indd 1994 8/1/19 1:33 PM CHAPTER 298: The Patient with Morbid Obesity 1995 caliber, modifying airway configuration, which in turn increases upper airway collapsibility. Thus, airways are predisposed to repetitive closure during sleep. 20 Daytime sleepiness increases and may be associated with accidental trauma.19 Cor pulmonale and hypercapnic respiratory failure are common. Obesity hypoventilation syndrome ( Table 298-1) was first described over 50 years ago. 21,22 The most common symptoms are (1) respiratory failure, (2) severe hypoxemia, (3) hypercapnia, and (4) pulmonary hypertension. 22-24 ESTIMATING PATIENT WEIGHT The Broselow tape inaccurately predicts actual weight in one third of children.25 The significance of this inaccuracy has not been studied in depth. A weight-estimation formula based on mid-arm circumference is reliable for use in school-age children and may be an alternative to the Broselow tape. 26 The formula is as follows: weight (kg) = (mid-arm circumference [cm] – 10) × 3. When compared to the Argal, Advanced Pediatric Life Support, and Best Guess formulas, Krieser et al 27 found that parental estimation of weight was more accurate.27 The concern for equipment weight capacity in the adult patient with obesity is an important determination for imaging. Scales in most EDs have a maximum weight capacity of 150 kg. Mechanized beds that weigh patients are not common in the ED but are a consideration for equip ment. Patients with obesity tend to significantly underestimate their own weight. A variety of formulas are available to estimate weight in adults who are obese using height and waist, hip, and arm circumfer ence. The formula developed by Crandall et al 28 seems to require the least amount of time and patient manipulation. Two distinct formulas for nonpregnant females and males have been developed as follows: Nonpregnant females: Weight (kg) = 64.6 + 2.15 (arm circumference in cm) + 0.54 (height in cm) Ma les: Weight (kg) = 93.2 + 3.29 (arm circumference in cm) + 0.43 (height in cm) SPHYGMOMANOMETRY Improper blood pressure cuff width and circumference will artificially elevate pressure readings. The standard adult blood pressure cuff is too short for patients with an arm circumference of 32 cm or larger. Patients who are overweight or obese will require cuffs larger in size. The American Heart Association recommends the following cuff widths when evaluating blood pressure in patients who are obese: (1) for arm circumferences ranging from 35 to 44 cm, a bladder measuring 16 cm in width is needed; (2) for circumferences from 45 to 52 cm, the bladder width should be 20 cm; and (3) in patients with short upper arm length, a 16-cm-wide cuff should be used. 29,30 MEDICATION DOSING Little evidence-based literature is available for appropriate dosing in obesity, and nearly none is available in the obese child. Fortunately, many drugs used in resuscitation are not lipophilic, and lean body mass is a reasonable dosing guide. Altered physiology is characterized by an increased clearance of hydrophilic drugs, a larger volume of distribution for lipophilic drugs, and a decrease in lean body mass and tissue water content, as compared to their lean counterparts. 31 Altered mechanics can predispose the morbidly obese to systemic toxicity due to either overdosing or lack of efficacy from underdosing.

arance of hydrophilic drugs, a larger volume of distribution for lipophilic drugs, and a decrease in lean body mass and tissue water content, as compared to their lean counterparts. 31 Altered mechanics can predispose the morbidly obese to systemic toxicity due to either overdosing or lack of efficacy from underdosing. 32,33 A weight-based medication schedule uses ideal body weight, total body weight, or dosing weight to avoid systemic side effects and lack of clinical efficacy by underdosing. Ideal body weight according to the Devine formula 34 is as follows: Ideal body weight (male) = 50.0 kg + 2.3 kg (each inch >5 feet) Ideal body weight (female) = 45.5 kg + 2.3 kg (each inch >5 feet) Dosing weight is an adjusted body weight of overweight or obese patients and is used only for drugs for which there are recommendations specifying that the actual body weight should be adjusted to use in the dose calculation. Dosing weight = Ideal body weight + [0.4 × (Actual – Ideal body weight)] Exception: If actual < ideal body weight, then the dosing weight = actual Table 298-2 divides select drugs into ideal body weight, total body weight, and dosing weight dosing. 35 Fentanyl and the benzodiazepines are lipophilic and have a prolonged half-life in obese patients. With these drugs, the initial dose based on total body weight may be needed, but subsequent doses should be based on ideal body weight. 36 It is best to check with a pharmacist for specific dosage regimens. VASCULAR ACCESS Vascular access is problematic. Patients who are critically ill and mor bidly obese patients require fluid administration often guided by central venous pressure and urine output. 37 Central venous pressure placement is extremely challenging even for the most skilled physician. In the obese patient, the distance from skin to vessel is much farther than normal, anatomic landmarks are obscured (Figure 298-1A and B), and the angle of approach may be too steep to allow cannulation even after reaching the vessel. There is no clear consensus as to the preferable site and approach to central venous catheterization. In general, there is an increased inci dence of infection and deep venous thrombosis when using the femoral approach. 38 If this proves to be the only option, then use this site. The internal jugular vein can be accessed with equal success to the subclavian approach in patients who are obese. The success rate might be increased with the head maintained in the neutral position, thereby reducing the risk of overlap of the internal jugular vein over the carotid artery. A US-guided 15-cm catheter can be used to cannulate the brachial or basilic vein.40 Another approach is the use of a pediatric central venous catheter placed into the basilic vein. The pediatric central venous catheter is 8 cm (3.15 in.) in length, is a double-lumen catheter, and has 18- and 20-gauge lumens. 41 Longer catheters can also be considered to guard against inadvertent dislodgement. IMAGING Attenuation severely limits the image quality of plain radiographs (Figure 298-2). Increasing exposure time can improve the image but at the expense of increased radiation. Motion artifact increases with increased exposure time. Multiple cassettes may be required if the patient is too large for a single 14 × 17–inch film. Patients may be able to stand for plain radiography if too large for the tables. CT and MRI scanners have both patient weight and girth limits, consider patient shoulder and pelvis girth.

creases with increased exposure time. Multiple cassettes may be required if the patient is too large for a single 14 × 17–inch film. Patients may be able to stand for plain radiography if too large for the tables. CT and MRI scanners have both patient weight and girth limits, consider patient shoulder and pelvis girth. Newer CT scanners can TABLE 298-1 Diagnostic Criteria for Obesity Hypoventilation Syndrome •   Body mass index 30 kg/m2 •   Daytime Paco2 >45 mm Hg •   Associated  sleep-related  breathing  disorder  (obstructive  sleep apnea–hypopnea syndrome or sleep hypoventilation or both) •   Absence of other known causes of hypoventilation Abbreviation: Paco2 = partial pressure of arterial carbon dioxide. TABLE 298-2 Dosing of Select Drugs Dosing Drugs Ideal body weight Penicillins, cephalosporins, linezolid, corticosteroids, H2-blockers, digoxin, β-blockers, atracurium, vecuronium, fentanyl*, midazolam*, lorazepam*, phenytoin, propofol Total body weight Succinylcholine, rocuronium, unfractionated heparin, enoxaparin, vancomycin Dosing weight Aminoglycosides, fluoroquinolones *Initial dose based on total body weight. Tintinalli_Sec26_p1979-2024.indd 1995 8/1/19 1:33 PM

ers, atracurium, vecuronium, fentanyl*, midazolam*, lorazepam*, phenytoin, propofol Total body weight Succinylcholine, rocuronium, unfractionated heparin, enoxaparin, vancomycin Dosing weight Aminoglycosides, fluoroquinolones *Initial dose based on total body weight. Tintinalli_Sec26_p1979-2024.indd 1995 8/1/19 1:33 PM 1996 SECTION 26: Special Situations accommodate up to 660 lb. If the patient outweighs equipment capacity, consider transferring the patient to an institution with a larger-capacity scanner, or veterinary schools may be an option. Most standard MRIs have a maximum shoulder-to-shoulder width of 52 inches (137 cm) and weight limits of 300 to 350 lb (136 to 159 kg), although open MRI scanners can sometimes be an option for large body diameters. Diagnostic peritoneal lavage has been suggested as an option in the patient with obesity and blunt abdominal trauma who is too large for imaging equipment 43; however, many surgeons are no longer accus tomed to making decisions based on results, and in the morbidly obese patient, diagnostic peritoneal lavage is difficult to perform. PROCEDURAL SEDATION Give procedural sedation drugs and pain medications cautiously. Select doses at the lower end of the range, and titrate to effect. Local and regional anesthesia might be considered for complicated or prolonged procedures. FIGURE 298-1. A and B. Difficulties in landmark identification. FIGURE 298-2. Attenuation can blur findings on plain radiographic films. AIRWAY MANAGEMENT Difficulty with mask ventilation, rapid oxygen desaturation, and altered pharmacokinetics can make airway management challenging. 45 Impedance to airway management is caused by excess fatty tissue externally on the breast, neck, thoracic wall, and abdomen and internally in the mouth, pharynx, and abdomen. First-attempt success is significantly less in obese patients. Patients who are obese have increased intra-abdominal pressure and increased incidence of hiatal hernia and gastroesophageal reflux disease. These characteristics render patients more prone to aspiration during airway management. 45,46 Patients who are obese will desaturate more rapidly after preoxygen ation than their lean counterparts. When no cervical spine injury is suspected, desaturation may be partially prevented by keeping the patient in a 25-degree head-up position during preoxygenation. Two-person bag-valve mask with a two-handed bilateral jaw thrust is recommended in patients who are morbidly obese. If tolerated, an oral airway may be used to prevent the tongue from occluding the airway. The early use of noninvasive positive-pressure ventilation may abate the need for endotracheal intubation. High expiratory positive pressures may be needed. Obesity is not a contraindication for rapid-sequence intubation. Advance preparation is critical, and assessment for a potential difficult airway is of utmost importance. The “sniffing” position results in suboptimal positioning for laryngoscopy in patients who are obese, and this may also confound results and falsely worsen graded views. 49 The “ramping” position (Figure 298-3A) offers improved intubation conditions in patients who are morbidly obese compared to the “sniffing” position (Figure 298-3B). This position is achieved by placing multiple folded blankets under the upper body, head, and neck until the external auditory meatus and the sternal notch are horizontally aligned. 50 Another option is elevating the patient’s head and thorax with the intubation physician standing on a stool behind the patient and essentially intubating with the patient semi-upright (see Chapter 29A, “Tracheal Intubation” , Figure 29A-3).

the external auditory meatus and the sternal notch are horizontally aligned. 50 Another option is elevating the patient’s head and thorax with the intubation physician standing on a stool behind the patient and essentially intubating with the patient semi-upright (see Chapter 29A, “Tracheal Intubation” , Figure 29A-3). First give consideration to awake intubation, given that patients who are obese may be difficult to mask ventilate and rapid oxygen desatura tion may occur after the ablation of spontaneous ventilation, especially in patients with a BMI greater than 40 kg/m 2.51-53 The awake intubation may be performed either by the nasotracheal or orotracheal routes. The relative benefits and risks of the awake intubation approach must be weighed against the merits of rapid-sequence intubation, which reduces risk of aspiration, improves intubating conditions, and results in easier insertion of advanced and rescue airway devices. During rapidsequence intubation, the chance for first-pass success can be optimized Tintinalli_Sec26_p1979-2024.indd 1996 8/1/19 1:34 PM