ADVANCES IN CLINICAL ANESTHESIA
| ANESTHESIA FOR THE MORBIDLY OBESE PATIENT —Martin W. Allard, MB, ChB, Professor of Anesthesiology,
Loma Linda University School of Medicine, Loma Linda, CA
|
| Scope of problem: morbid obesity most common nutritional disorder; 50% increase in incidence since 1990s; accounted
for ≈18% of population in 1998 (now >20% of population); largest increases seen in southern part of
United States
|
| Definitions of morbid obesity: include 100 lb over ideal body weight, twice ideal body weight, and obesity complicated
by other medical conditions (most useful for anestesia provider)
|
| Calculating body mass index (BMI): calculated as weight (kg)/[height (m)]2 ; super morbidly obese have BMI
>40; overweight, BMI 25 to 30; class I obesity, BMI 30 to 35; class II obesity, BMI 35 to 40; ≈400,000 Americans
who weigh >400 lb
|
| Cost of morbid obesity: majority have ≥2 associated diseases; patient may be taking 5 to 20 pills daily; patient often
socially isolated; difficulties entering workforce
|
| Comorbidities with morbid obesity: hypertension; diabetes; coronary artery disease (CAD); joint and bone
problems; sleep apnea; decreased self-esteem; decreased mobility and daily function; decreased longevity; study of
comorbidities commonly associated with obesity and sleep apnea in patients undergoing major joint replacement
found chronic obstructive pulmonary disease (COPD) in 14%, CAD in 27%, hypertension in ≈60%, and arrhythmias
|
| Procedural complications that increase with weight gain: increased incidence of respiratory complications
in postoperative setting (particularly hypoxemia and hypercapnia, atelectasis, decreased functional residual capacity
[FRC], and increased airway resistance; use small amounts of respiratory depressants); aspiration; preoxygenation
should be standard for all patients
|
| Prevalence of sleep-disordered breathing: obesity greatest predictor; older age increases risk; occurs more often
in men than women; increased incidence in minority patients
|
| Obstructive sleep apnea: defined as repeated interruptions in breathing during sleep; causes include obesity (60%
to 90% of cases), alcohol or drug-induced sleep, and orofacial or craniofacial abnormalities; possible effects include
hypoxemia, hypercapnia, sleep deprivation, and cardiac failure; often associated with difficult intubation; closed-
claim reviews for unexplained postoperative cardiopulmonary arrest in hospitalized patients found link between narcotic
administration and postoperative respiratory depression; all cases could have been prevented with audible pulse
oximetry monitoring (currently not standard of care postoperatively); consider keeping patient in location with
higher acuity nursing; consider other mechanisms for postoperative analgesia; simply monitoring pulse oximetry
may not be sufficient
|
| Treatment options for morbid obesity: diets; medications; exercise programs; behavior modification; surgery
|
| Morbid obesity surgery in United States: ≈50,000 bariatric surgeries in 2000;103,000 procedures in 2003;
more bariatric surgery centers opening
|
| Benefits of surgery: surgery not performed as cure but to slow down progression (and reverse course) of disease;
offers improved longevity; most harmful health consequences reversible with weight loss; improves or cures diabetes,
high blood pressure (BP), sleep apnea, and hypercholesterolemia; improves overall patient functioning; may
improve longevity
|
| Surgical procedures: vertical-banded gastroplasty; gastric bypass; laparoscopic adjustable gastric banding (Lap-
Band)
|
 | Gastroplasty: stomach stapling; achieves loss of 43% to 48% of excess weight; less invasive than gastric bypass
|
| Gastric bypass: stomach stapling plus intestinal bypass; Roux-en-Y gastric bypass; achieves loss of 66% to 80% of
excess weight; higher incidence of complications
|
| Lap-Band: silicone band around gastric fundus; adjustable; does not achieve as much weight loss; less invasive
procedure; simpler surgery and anesthetic; shorter postoperative recovery period; less expensive
|
| Preoperative evaluation: “all about the airway”; pulmonary evaluation; cardiac evaluation; medication management;
respiratory complications include hypoxemia, hypercapnia, atelectasis, decline in FRC, increased airway resistance,
and increased risk for aspiration
|
| Immediately preoperatively: good intravenous (IV) access in each arm; maintain usual cardiac medications;
consider early antiemetic prophylaxis (eg, scopolamine); appropriate monitoring; questionable whether benzodiazepines
worthwhile; transport to operating room with O2 ; BP monitoring can be difficult (insertion of arterial line
depends on procedure and positioning; “central pressures can be valuable”); ischemia monitor (eg, Swan-Ganz catheter,
transesophageal echocardiography); cerebral function monitor
|
| Intraoperative management: preoxygenation; positioning (particularly for intubation; “battle before the induction”);
key to get horizontal line between sternal notch and external auditory meatus (easier to intubate in this position);
most are difficult airways; few difficult intubations; difficult intubation more common in obese than lean
patients (Juvin study found obese 15.5% vs lean 2.2%; none were impossible); routine awake intubation not mandatory
in obese patient; Mallampati score of III or IV risk factor and predictor of difficult intubation; BMI not predictive
for difficult intubation
|
| Airway management: laryngeal mask airway; awake endotracheal tube; flexible fiberoptic laryngoscope (and
short-handled laryngoscope); positioning; agents of choice
|
| Anesthetic complications increase with increasing weight: in Rose and Brodsky studies, 5% of direct laryngoscopies
reported as awkward, 5% reported as difficult; risk factors during tracheal intubation include collar size
>17 in and Mallampati score >III; ventilation problems, particularly with prone positioning; longer surgical times
lead to longer anesthetic exposure
|
| Benefits of early recovery: reduces risk for airway complications, aspiration, hypoxemia, and cardiovascular
complications; rapid emergence, extubation, and restoration of spontaneous breathing
|
| Pharmacokinetics in obesity: alters volume of distribution, clearance, and protein binding; difference primarily
anecdotal and empiric; using ideal body weight results in underdosing of many drugs, more difficult intubation and
airway establishment, and higher incidence (in certain situations) of redistribution of small amounts of drugs (and
potential for awareness); ideal body weight used in mild or moderately lipophilic drugs; total body weight used in
highly lipophilic drugs
|
| IV induction agents: propofol preferable to other induction agents; volume of distribution similar for obese and
nonobese patients; thiopental highly lipid-soluble with large volume of distribution; etomidate high volume of distribution
(possible consideration in cardiac patient)
|
| Anesthetic agents: opiates—fentanyl (same volume of distribution); inhalational agents—desflurane and sevoflurane;
lowest biotransformation rate and quickest recovery; muscle relaxants—atracurium and cisatracurium;
dosed using total body weight; yields similar duration of action; spinals—75% to 80% of normal dose due to increased
cephalad spread
|
| Alternative analgesia: peripheral nerve blocks; local infiltration (before, during, and after surgery); spinals; epidurals;
nonsteroidal anti-inflammatory drugs (NSAIDs); cyclooxygenase-2 (COX-2) inhibitors (eg, ketorolac); α2
agonists (eg, dexmedetomidine)
|
| Inhalational agents: desflurane and sevoflurane have lower blood solubility than halothane and isoflurane; more effective
for obese patient; longer-acting anesthetics lead to prolonged recovery; faster terminal decrement with desflurane
and sevoflurane; another study showed that patient receiving desflurane can be rapidly awakened and rapidly
extubated; also less breakdown of desflurane than other agents; also less recovered as urinary metabolites (less potential
for toxicity; possible risks include halothane hepatitis); blood/gas partition coefficients of desflurane and sevoflurane
significantly lower than halothane, enflurane, and isoflurane; however, fat/blood partition coefficient for
sevoflurane between halothane and enflurane (concern in long procedures); Torri study comparing isoflurane and
sevoflurane for laparoscopic gastric banding in morbidly obese patients showed advantage for sevoflurane (response,
emergence, and extubation); De Baerdemaeker study compared desflurane and sevoflurane in morbidly obese patients
and found those receiving desflurane oriented quicker, extubated quicker, and responded more rapidly; suggests recovery
faster and hemodynamic controllability better in desflurane group; Juvin looked at propofol, isoflurane, and
desflurane in morbidly obese; found desflurane and isoflurane superior to propofol for eye opening, extubation, and
orientation; Strum compared sevoflurane and desflurane in morbidly obese patients undergoing longer procedures and
found similar results related to orientation, extubation, hand grip, and eye opening; study looking at return of airway
reflexes after desflurane vs propofol found more rapid emergence, faster recovery, and similar incidence of airway irritability
with desflurane
|
| Summary: two thirds of surgical patients overweight; one third of all Americans obese; overweight and obesity associated
with comorbid conditions, particularly cardiac and respiratory; important to plan anesthetic, avoid complications,
and choose small aliquots of many different anesthetic agents to reduce overall load on patient; volatile
inhaled anesthetics allow adjustment of depth of anesthesia; use least soluble agents
|
| LATEX ALLERGY IN THE PERIOPERATIVE SETTING —Suzanne Escudier, Assistant Professor of Anesthesiology,
Texas Tech University Health Sciences Center, Lubbock, TX
|
| Objectives: identification of patient at high risk for latex sensitization; prevention of latex sensitization in anesthesia
personnel
|
| History of latex allergy: Mayans first produced rubber balls in 1600 BC ; surgical gloves became common in 1900
AD ; allergic reactions to natural rubber reported in 1933; irritant and delayed contact reactions reported in 1979;
first anaphylactic reactions reported in 1984; first fatality occurred in 1991
|
| Latex: usually associated with weeping wood tree, North American desert shrub, and ornamental rubber plant; International
Union of Immunological Societies has identified 11 sensitizing proteins; ≤240 possible allergens
|
| Exposure: includes contact, inhalation, ingestion, parenteral injection, and wound inoculation; (patient can be exposed
by all methods; anesthesia provider usually exposed by contact or inhalation); powdered latex gloves most
common culprit for allergic reaction
|
| Risk factors: multiple surgical procedures; occupational exposure (eg, hairdresser, health care); history of allergic-
type reactions (eg, hay fever, rhinitis, asthma, eczema); food allergy; severe hand dermatitis
|
| Foods associated with latex allergy: include banana, kiwi, avocado, chestnut, passion fruit, celery, potato, and
peach
|
| Diagnosis: positive history or positive physical examination and one confirmatory test
|
| Tests: no standardized serologic test for latex allergy; skin prick gold standard (uses extract from surgical glove);
patch test uses 1 cm square area of glove placed under adhesive bandage (include in differential diagnosis)
|
| Prevention of allergic reactions: avoid moisture, heat, and friction; avoid latex-containing products; establish latex-free
health care environment; beginning in 1998, all products containing latex must be labeled (packages, not
individual items)
|
| Management of latex-sensitive patient: avoid latex in patient with known allergy and patient at risk for latex allergy;
coordinate with all support teams; schedule patient as first case of day; latex-free cart should accompany patient;
specific latex allergy identification tag; pretreatment unnecessary (not shown effective)
|
| Treatment of allergic reaction to latex: avoid skin irritation; use topical corticosteroids; identify source of allergen
and limit exposure; treat specific reaction
|
| When reaction to latex occurs: some laboratory findings required within 4 hr; flag chart; consult allergist
|
| Anesthesia providers and latex allergy: incidence of irritant or contact dermatitis 24%; incidence of latex-specific
IgE positivity 12.5%; 10% of sensitized anesthesiologists have asymptomatic latex allergy
|
| Management of health care worker with latex allergy: avoid using latex gloves; coworkers should use powderless,
low-latex allergen gloves
|
| Management of health care facility: evaluate process for glove selection using multidisciplinary task force; protocol
for reaction identification and investigation; protocol for allergic patients and health care workers; education
|
| Future: genetic basis for predisposition to latex allergy; desensitization process; new protein-free latex
|
Educational Objectives
| The goal of this program is to educate the listener about anesthesia for the morbidly obese patient and latex allergy in the
perioperative setting. After hearing and assimilating this program, the participant will be better able to:
|
| 1. Discuss the comorbidities commonly associated with morbid obesity and review the procedural complications that
increase with weight gain.
|
| 2. Summarize the benefits of surgery and the common surgical procedures for morbid obesity.
|
| 3. Review preoperative evaluation and intraoperative anesthetic management for the morbidly obese patient.
|
| 4. Identify the patient at high risk for latex sensitization.
|
| 5. Examine the prevention and treatment of latex-induced anaphylaxis in the operating room.
|
Discussed on This Program
Atracurium besylate [Tracrium]
Cisatracurium besylate [Nimbex]
Desflurane [Suprane]
Dexmedetomidine HCl [Precedex]
Etomidate [Amidate]
Fentanyl citrate [Sublimaze]
Halothane [Fluothane]
Ketorolac tromethamine [Acular, Acular LS, Acular PF, Toradol]
Propofol [Diprivan]
Scopolamine, transdermal [Transderm-Scop]
Sevoflurane [Ultane]
Thiopental sodium [Pentothal]
Suggested Reading
Bailey JM: Context-sensitive half-times and other decrement times of inhaled anesthetics. Anesth Analg 85:681, 1997;
Barbara J et al: Retention of airborne latex particles by a bacterial and viral filter used in anaesthesia apparatus. Anaesthesia
56:231, 2001; Benumof JL et al: Critical hemoglobin desaturation will occur before return to an unparalyzed state
following 1 mg/kg intravenous succinylcholine. Anesthesiology 87:979, 1997; Brock-Utne JG: Clinical manifestations of
latex anaphylaxis during anesthesia differ from those not anesthesia/surgery-related. Anesth Analg 97:1204; author reply
1204, 2003; Brodsky JB et al: Morbid obesity and tracheal intubation. Anesth Analg 94:732, 2002; Brown RH et al:
Prevalence of latex allergy among anesthesiologists: identification of sensitized but asymptomatic individuals. Anesthesiology
89:292, 1998; De Baerdemaeker LE et al: Optimization of desflurane administration in morbidly obese patients: a
comparison with sevoflurane using an 'inhalation bolus' technique. Br J Anaesth 91:638, 2003; De Baerdemaeker LE et
al: Postoperative results after desflurane or sevoflurane combined with remifentanil in morbidly obese patients. Obes Surg
16:728, 2006; Dreyfus DH et al: Anaphylaxis to latex in patients without identified risk factors for latex allergy. Conn
Med 68:217, 2004; Eckinger P et al: Latex allergy: oh, what a surprise! Another reason why all anesthesia equipment
should be latex-free. Anesth Analg 99:629, 2004; Eger EI 2nd et al: The effect of anesthetic duration on kinetic and recovery
characteristics of desflurane versus sevoflurane, and on the kinetic characteristics of compound A, in volunteers.
Anesth Analg 86:414, 1998; Elliott BA: Latex allergy: the perspective from the surgical suite. J Allergy Clin Immunol
110:S117, 2002; Ghouri AF et al: Recovery profile after desflurane-nitrous oxide versus isoflurane-nitrous oxide in outpatients.
Anesthesiology 74:419, 1991; Haeberle HA et al: Role of cross-allergies to latex in clinical routine of anesthesia.
J Clin Anesth 15:495, 2003; Hebl JR et al: Prolonged cardiovascular collapse due to unrecognized latex anaphylaxis.
Anesth Analg 98:1124, 2004; Joint Task Force on Practice Parameters; American Academy of Allergy et al: The diagnosis
and management of anaphylaxis: an updated practice parameter. J Allergy Clin Immunol 115:S483, 2005; Juvin P et al:
Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 97:595, 2003; Juvin P et al:
Postoperative recovery after desflurane, propofol, or isoflurane anesthesia among morbidly obese patients: a prospective, randomized
study. Anesth Analg 91:714, 2000; Kripke DF et al: Prevalence of sleep-disordered breathing in ages 40-64
years: a population-based survey. Sleep 20:65, 1997; McKay RE et al: Airway reflexes return more rapidly after desflurane
anesthesia than after sevoflurane anesthesia. Anesth Analg 100:697, 2005; Mokdad AH et al: The spread of the obesity
epidemic in the United States, 1991-1998. JAMA 282:1519, 1999; Ownby DR: A history of latex allergy. J Allergy
Clin Immunol 110:S27, 2002; Patriarca G et al: Latex allergy desensitization by exposure protocol: five case reports.
Anesth Analg 94:754, 2002; Puglisi F et al: Tachyarrhythmia due to atrial fibrillation in an intragastric balloon carrier: coincidence
or consequence? Obes Surg 15:716, 2005; Rose DK et al: The airway: problems and predictions in 18,500 patients.
Can J Anaesth 41:372, 1994; Strum EM et al: Emergence and recovery characteristics of desflurane versus
sevoflurane in morbidly obese adult surgical patients: a prospective, randomized study. Anesth Analg 99:1848, 2004; Task
Force on Latex Sensitivity of the American Society of Anesthesiologists Committee on Occupational Health of Operating
Room Personnel: Natural rubber latex allergy: considerations for anesthesiologists. 2005; Torri G et al: Randomized comparison
of isoflurane and sevoflurane for laparoscopic gastric banding in morbidly obese patients. J Clin Anesth 13:565, 2001;
Zaglaniczny K: Latex allergy: are you at risk? AANA J 69:413, 2001.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial relationship
with the manufacturer or provider of any commercial product or service discussed. For this issue, the faculty reported
nothing to disclose.
Dr. Allard was recorded at the 34th Annual Symposium Advances in Clinical Anesthetic Practice, held February 18-22,
2006, in Rancho Mirage, CA, and sponsored by Loma Linda University School of Medicine; Dr. Escudier, at the Annual
Meeting of the Texas Society of Anesthesiologists, held September 8-11, 2005, in San Antonio, TX. The Audio-Digest
Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.
|
