Transcript Bariatric SurgeryAnesthesia for Miller, ch:64 Ashish C. Sinha, David

Anesthesia for
Bariatric Surgery
Miller, ch:64
Ashish C. Sinha,
David M. Eckmann
1
Obesity

Common enemy of surgeon and anestethist.

A rarity until the middle of the 20th century.
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200 million Americans, or 65% of the U.S. adult
population, are overweight or obese.

It is second only to smoking as a preventable
cause of death.
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Obesity

Obesity can be defined as a “disease” because
it is a physiologic dysfunction of the human
organism.

Food calorie intake exceeds energy
expenditure over a long period.
3
Obesity

Obesity influenced by
genetic, behavioral,
cultural, and
socioeconomic factors.
Genetics

Behavior
Syndromes associated
with obesity:
 Leptin deficiency
 Prader-Willi syndrome
 Lawrence-Moon-Biedl
syndrome
Environment
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BMI: kg/m2
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Obesity
Waist Circumference and Risk
Waist
Circumference
Normal
Weight
Overweight
Obese Class 1
<102 cm(M)
<88 cm(F)
Least risk
Increased risk
High risk
≥102 cm(M)
≥88 cm(F)
Increased risk
High risk
Very high risk
•BMI has been shown to be a relatively insensitive indicator of the risk for
obesity-associated metabolic and cardiovascular disease.
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Table 64-3 -- Health Risks Associated with Increasing Body Mass Index
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Metabolic Syndrome
•A group of defined metabolic and physical abnormalities.
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Metabolic Syndrome
Clinical Criteria for Diagnosing Metabolic Syndrome *
Criteria
Defining Value
Abdominal obesity
Waist circumference >102 cm in men
and >88 cm in women
Triglycerides
≥150 mg/dL
High-density lipoprotein
cholesterol
<40 mg/dL in men and
<50 mg/dL in women
Blood pressure
≥130/85 mm Hg
Fasting glucose
≥110 mg/dL
* Three of five criteria must be met.
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Metabolic Syndrome
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In the United States, nearly 50 million
people have metabolic syndrome.

More than 83% meet the criterion of
abdominal obesity.
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The incidence of metabolic syndrome
increases with age.
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Metabolic Syndrome

Men are affected more commonly than
women.
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Hispanics and south Asians appear to be
susceptible.
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Its frequency is lower in African American
than in white men.
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Metabolic Syndrome

May result from the use of some drugs.
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Have a higher risk for cardiovascular disease and
type 2 diabetes.
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Metabolic syndrome is also associated with a variety
of other conditions, such as:
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polycystic ovary syndrome
nonalcoholic fatty liver disease
gallstones
sleep disturbances
sexual impotence
some forms of cancer
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Metabolic Syndrome

Inflammatory processes appear to play an
important role in the metabolic syndrome.

Visceral adipose tissue has been identified as
an important source of proinflammatory
cytokines:
 Cytokines (primarily IL-6 and TNF-a)
 Adipokines (leptin, adiponectin, adipose-derived resistin)
14
Obstructive Sleep Apnea/Hypopnea Syndrome
(OSA/OSAHS(

Recurrent episodes of upper airway
obstruction occurring during sleep.
 Complete cessation of airflow
 Lasting 10 seconds or longer despite maintenance of
neuromuscular ventilatory effort
 Occurring five or more times per hour of sleep
 Accompanied by a decrease of at least 4% in SaO2.

The results of polysomnography are reported
as the apnea/hypopnea index (AHI).
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Obstructive Sleep Apnea/Hypopnea Syndrome
(OSA/OSAHS(
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Mild disease:
◦ AHI of 5 to 15 events per hour
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Moderate disease:
◦ AHI of 15 to 30 events per hour
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Severe disease:
◦ AHI of greater than 30 events per hour
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Obstructive Sleep Apnea/Hypopnea Syndrome

Numerous studies have confirmed that obesity is the
greatest risk factor for OSAHS.
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It is important that obese patients scheduled for
bariatric surgery undergo preoperative
polysomnographic testing for OSAHS.
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Preoperative diagnosis and appropriate interventional
management can have the following benefits:
 less postoperative sleep deprivation, improved response to
analgesic and anesthetic drugs, and normalization of cardiovascular
disturbances
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Obstructive Sleep Apnea/Hypopnea Syndrome

Increased amounts of adipose tissue in their oral
and pharyngeal tissues.

This can contribute to the development:
 Airway obstruction
 Difficult mask ventilation
 Difficult laryngoscopy and endotracheal intubation
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Additionally, airway obstruction after extubation
is likely to be complicated by the use of opiate
and sedative drugs needed for postoperative pain
management.
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Obstructive Sleep Apnea/Hypopnea Syndrome
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OSA also plays an important role in inflammation and the metabolic syndrome.
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The sympathetic nervous system is activated as patients with untreated OSA
undergo cyclic episodes of hypoxia and reoxygenation; such activation leads to
elevated levels of proinflammatory cytokines and potentially oxidative stress of
vascular endothelium, which induces an even more heightened state of systemic
inflammation in obese patients with OSA
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Inflammatory mediators:
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IL-6
C-reactive protein
Leptin
TNF-a
IL-1
Reactive oxygen species
Adhesion molecules such as intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion
molecule-1 (VCAM-1)
Obesity, metabolic syndrome, and OSAHS are interrelated diseases that
significantly alter a patient's inflammatory disease profile.
19
Nonsurgical Management of Obesity

The primary goals of nonsurgical
management of obesity:
 Weight loss
 Treatment of the abnormalities associated with
metabolic syndrome

The goal of weight loss in therapeutic
lifestyle change is not to achieve normal
or ideal body weight (IBW).
20
Nonsurgical Management of Obesity

Statin therapy
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Ezetimibe
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Fibrates
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Omega-3 fatty acids
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Nicotinic acid
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Nonsurgical Management of Obesity

Antihypertensive drug therapy
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Oral hypoglycemic agents
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Antiplatelet therapy
22
framingham risk score
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Pharmacotherapy for Weight Loss

BMI of 30 or greater (=27 for patients with
obesity-related risk factors ).

Two categories of weight loss drugs:
◦ Appetite suppressants
 Phentermine
 Sibutramine
◦ Lipase inhibitors
 Orlistat
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Dietary and Herbal Medications
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Chitosan
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Chromium picolinate
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Conjugated linoleic acid
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Ephedra alkaloids (ma huang)

Garcinia cambogia
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Implanted Electrical Stimulators

Subcutaneously placed
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Stimulate regions along the lesser curvature
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One study documented:
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25% excess weight loss
Improved response to the oral glucose tolerance test
Decreases in blood pressure
Improvement in symptoms of gastroesophageal reflux disease,
along with increased parasympathetic drive.
Modification of Ghrelin levels may play a role in the
success of these devices.
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Implanted Electrical Stimulators
27
Surgical Management of Obesity

Gastric-restrictive procedures
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Combine gastric restriction with
induction of nutrient malabsorption
28
Restrictive Procedures

Creating a small pouch from the proximal
part of the stomach just distal to the
gastroesophageal junction.
 This increases mechanical resistance to gastric emptying of ingested
solids, whereas emptying of liquids proceeds normally.
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Vertical band gastroplasty (VBG)
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Laparoscopic gastric band (LGB)
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VERTICAL BANDED
GASTROPLASTY (VBG)

VBG is a purely
restrictive procedure
in which the upper
stomach is stapled and
divided, forming a small
pouch that reduces the
size of the stomach
and the amount of
food the stomach can
hold.
Laparoscopic gastric band (LGB)
31
Sleeve Gastrectomy
Removes 2/3 of
the stomach
Can be used as
a single stage
procedure
32
Malabsorptive Procedures

Two commonly performed malabsorptive operations:
◦ Gastric bypass (GBP)
◦ Biliary pancreatic diversion (BPD)

GBP surgery involves the creation of a small gastric
pouch by stapling or banding the stomach, which results
in an element of gastric restriction.
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GBP also involves the creation of a Roux-en-Y
anastomosis in which the small gastric pouch is directly
connected to the middle portion of the jejunum
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Gastric bypass (GBP)
34
Biliopancreatic Diversion (BPD)

Mixed restrictive and
malabsorptive
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Connect pouch to small
intestine
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The more proximal
biliopancreatic limb is
anastomosed to the
alimentary limb about 50
cm from the ileocecal
valve.
Health Benefits of Bariatric Surgery

The two most significant outcome:
◦ Weight loss
◦ Resolution of comorbid conditions
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Absolute weight loss averaged: (meta-analyses)
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46.4 kg for BPD
43.5 kg for GBP
39.8 kg for VBG
28.6 kg for gastric banding
Far greater than that nonsurgical methods
Closer to patients’ desired and expected weight loss
Long-term maintenance of weight loss
36
Health Benefits of Bariatric Surgery
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Diabetes resolved in more than 75% overall:
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98.9% for BPD
87.3% for GBP
71.6% for VBG
47.9% for gastric banding
 nonsurgical weight loss is accompanied by relapsing disease in nearly 100% of patients within 5
years.
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Postsurgical effects on hypertension were:
◦ Greatest after BPD (83%)
◦ Intermediate after GBP (67.5%) and VBG (69%)
◦ Least after gastric banding (43%)
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Resolution of OSAHS occurring in 85.7% of patients overall.
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Improvement in:
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fatty infiltration of the liver
respiratory function and asthmatic symptoms
reversal of the cardiomyopathy of obesity
joint pain and mobility
37
Anesthetic Management of
Bariatric Surgical Patients
Preoperative Evaluation

Comorbidity

AHI score greater than 30, implying
severe sleep apnea.
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CPAP levels greater than 10 imply a
patient with the potential for difficult
mask ventilation.
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Preoperative Evaluation

History of previous surgeries
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Preoperative laboratory evaluations
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Fasting blood glucose
Lipid profile
Serum chemistries (to evaluate renal and hepatic Function)
Complete blood count
Ferritin
Vitamin B12
Thyrotropin
25-hydroxyvitamin D
LFT
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Preoperative Evaluation
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Contraindications to bariatric surgery:
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Unstable CAD
Uncontrolled severe OSA
Uncontrolled psychiatric disorder
Mental retardation (IQ < 60)
Inability to understand the surgery
Perceived inability to adhere to postoperative
restrictions
◦ Continued drug abuse
◦ Cirrhotic liver disease with portal hypertension
◦ Malignancy with a poor 5-year survival prognosis
40
Intraoperative Care
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Airway management
Positioning
Monitoring
Choice of anesthetic technique
Anesthetic agents
Pain control
Fluid management
Specific interventions, techniques, and approaches
used by the anesthesia care team providing
anesthesia for obese patients are important
determinants of outcome.
41
Airway Management

Difficulty with laryngoscopy and intubation.
 Short, thick neck, large tongue, and significant redundant pharyngeal soft
tissue
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The correlation between morbid obesity and difficult
laryngoscopy and intubation is not universally observed in
clinical practice.
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One study found an association between oropharyngeal
Mallampati classification and BMI as a predictor of difficult
laryngoscopy.
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Mallampati score had low specificity and low positive
predictive value (62% and 29%, respectively) for difficult
intubation.
42
Airway Management

Only an abundance of pretracheal soft tissue
measured ultrasonically and neck
circumferences were found to be positive
predictors of difficult intubation.
 The authors also assessed the airway by measurement
of the thyromental distance, mouth opening, degree of
neck mobility, Mallampati score, neck circumference,
and the presence of OSA.
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The incidence of difficult intubation in obese
patients was three times the incidence in the
nonobese population. (A meta-analysis of 35 studies:
suboptimal patient positioning)
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Ramped positioning
43
Airway Management
“stacking,” is to position the patient so that the tip of the chin is at a
higher level than the chest to facilitate laryngoscopy and intubation. The headelevated laryngoscopy position (HELP) is a step beyond stacking. It significantly
elevates the obese patient's head, upper body, and shoulders above the chest to
the extent that an imaginary horizontal line connects the sternal notch with the
external auditory meatus to better improve laryngoscopy and intubation
44
Airway Management
45
Airway Management
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Awake intubation
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Sedated fiberoptic intubation
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Laryngeal masks
46
Pulmonary physiology
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Decreased VC, IC, ERV, and FRC.
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Closing capacity in obese individuals is close to or may
fall within tidal breathing, particularly in the supine
position.
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Pulmonary physiology
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Obese patients reached the end point in less than 3 minutes,
whereas it took 6 minutes in patients with a normal BMI.
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Use of 10 cm H2O CPAP during preoxygenation
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PEEP
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Waist-to-hip ratio
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Patients in the supine position reached the end point in 2
minutes, but it took 30 seconds longer if the supine position with
the back elevated 30 degrees was used and 1 minute longer if
the 30-degree reverse Trendelenburg position was used.
 Reduce the alveolar-to-arterial oxygen difference, as well as to increase total
ventilatory compliance and reduce peak and plateau airway pressure when
compared with the supine position
48
Pulmonary physiology

Alveolar recruitment by repeated sustained
lung inflation to 50 cm H2O
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15 cm H2O PEEP
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In summary, the most favorable patient position
or optimal amount of PEEP during
preoxygenation, induction of anesthesia, or
intraoperatively has not been clearly
established for obese patients.
49
Pulmonary physiology
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There are no published guidelines to address the
issues of maintenance of oxygenation and
ventilatory mechanics in obese patients undergoing
general anesthesia.
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Anesthesia care providers should position patients
to achieve the combined goals of providing a
superior laryngoscopic view for ease of
endotracheal intubation while establishing optimal
conditions for oxygenation and preservation of
pulmonary mechanical function.
50
In our institution
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Ramped position (25- to 30-degree)
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Reverse Trendelenburg position, if needed
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Preoxygenated for 3 to 5 minutes with 100% oxygen
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CPAP or pressure-support (identical to the patient's home CPAP setting)
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Vntilation by facemask
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After induction, it is reasonable to maintain 10 to 12 cm H2O PEEP
intraoperatively
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Return the patient to the head-up position before emergence and extubation
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Pressure support or CPAP can be delivered immediately by mask applied to the
face
(sustained tetanus with the nerve stimulator and performance of a 5-second head lift)
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Patient Positioning

Morbidly obese patients do require extra
care in positioning.
 lack of evidence-based studies demonstrating that obese patients
have more frequent complications from positioning
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Supine position
Prone position
Pressure points
Protect the dependent hip
Excess axillary tissue
Lithotomy position
 compartment syndrome, the duration during which the legs are held
in stirrups.
52
53
Anesthetic Drugs and Dosing

Opioids, propofol, and benzodiazepines have
exaggerated responses in patients with OSA
 Decrease pharyngeal musculature tone.
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Volatile agents diminish the ventilatory response to
carbon dioxide in the setting of OSA.
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It therefore becomes attractive to use short-acting
drugs and nondepressors of ventilation such as the
α2-agonist dexmedetomidine.
54
Anesthetic Drugs and Dosing

Lean body mass is a good weight approximation to use when dosing
hydrophilic medications.
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Dosing of commonly used anesthetic drugs such as propofol,
vecuronium, rocuronium, and remifentanil is based on IBW.
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In contrast, thiopental, midazolam, succinylcholine, atracurium,
cisatracurium, fentanyl, and sufentanil should be dosed on the basis of
TBW.
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Maintenance doses of propofol should be based on TBW and,
conversely, on IBW for sufentanil.
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Some evidence suggests that desflurane may be the anesthetic of
choice. (stability and recovery)
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N2O: (analgesic effect and is eliminated rapidly, we prefer to avoid it)
55
IBW
J. D. Robinson Formula (1983)
52 kg + 1.9 kg per inch over 5 feet
(man)
49 kg + 1.7 kg per inch over 5 feet
(woman)
D. R. Miller Formula (1983)
56.2 kg + 1.41 kg per inch over 5 feet
(man)
53.1 kg + 1.36 kg per inch over 5 feet
(woman)
G. J. Hamwi Formula (1964)
48.0 kg + 2.7 kg per inch over 5 feet
(man)
45.5 kg + 2.2 kg per inch over 5 feet
(woman)
B. J. Devine Formula (1974)
50.0 + 2.3 kg per inch over 5 feet
(man)
45.5 + 2.3 kg per inch over 5 feet
(woman)
56
57
58
Aspiration

Obesity itself does not increase the risk for
aspiration.
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However, acid aspiration prophylaxis, including
H2 receptor antagonists or proton pump
inhibitors, must be considered in patients with
identifiable risk for spiration.

Awake fiberoptic intubation may also be
considered in such patients.
59
Induction of Anesthesia

Regional anesthesia:
◦ Safe&difficult (Position, landmarkers, catheters, needles, special ultrasound
probes)
◦ Increased cephalad spread (larger magnitude respiratory
compromise)

Obesity per se does not require invasive
monitoring, so GPB surgery can be performed
safely with routine monitoring.

The rationale for central venous access may stem
from difficulties in peripheral access rather than
any other indication.
60
Induction of Anesthesia

Postoperative pain management:
◦ Intravenous analgesia via PCA
◦ Thoracic epidural analgesia
◦ Opioid-based PCA with local anesthetic
infiltration of the wound
◦ Non-narcotic medication
61
Induction of Anesthesia

Using the appropriate table for the patient's
weight.

It may be useful to keep the patient
strapped throughout the period of sedation.

Apply a bean bag under the patient to keep
the patient from sliding off the operating
room table.
62
Induction of Anesthesia

Armboards may need extra padding to keep the patient
from having the arm and shoulder out of an anatomic
position.
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Fluid requirements may be greater than predicted, and in
even a relatively short, 2- to 3-hour case, 4 to 5 L of
crystalloid fluid may be needed to prevent acute tubular
necrosis in the kidneys.
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Predisposing factors:
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Hypovolemia
BMI greater than 50 kg/m2
Prolonged surgical time
Previous history of renal disease
Intraoperative hypotension
63
Management of Complications

Very safe, but not without potential complications
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In-hospital mortality rates:
 LGB: 0.27%
 Open GBP: 0.81%
 Statistically significant difference

In-hospital immediate postoperative morbidity:
 Wound
 Gastrointestinal
 Intestinal leakage
 Pulmonary
 Cardiovascular complications
64
Management of Complications

Range from 1.35% (wound complications) to 4.52%
(gastrointestinal complications) after LGB
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From 1.98% (wound complications) to 5.33%
(gastrointestinal complications) after open GBP.
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The most common complications requiring
reoperation include:
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Postoperative intra-abdominal bleeding
Anastomotic leakage
Suture line dehiscence
Small bowel obstruction
Deep wound infection
65
Management of Complications

Reoperation:
◦ Hypovolemia&dehydration:
 Bleeding, vasodilatation, and insensitive fluid losses
associated with fever and Infection.
◦ Aspiration:
 Postoperative ileus
 Small bowel obstruction,
 Surgical creation of a Roux-en-Y gastric bypass limb
that excludes the pylorus as an element of protection
from reflux.
 NGT, ICU
66
Management of Complications

Delayed complications:
◦ Surgical intervention:
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Anastomotic strictures or ulcers
Ventral hernias
Gastrogastric fistulas
Severe reflux
Small bowel obstruction
Cosmetic operations to remove excess skin
Adjustment of a gastric band
◦ Neurologic: (VitB12, Copper)
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Polyneuropathy
Polyradiculoneuropathy
Myelopathy
Encephalopathy
Optic neuropathy
◦ Nutritional and metabolic: (Enteral, Parenteral, Revision)
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Malnutrition.
Excessive weight loss
Steatorrhea or severe diarrhea
Hypoalbuminemia,
Marasmus
Edema
Hyperphagia
67
Management of Complications
68
Considerations for Management of Obese Patients
Undergoing Nonbariatric Surgery

Dindo and coworkers evaluated 6336 patients:
◦ Did not find any difference in the incidence or
severity of complications after elective general
surgery, except for surgical site infections.

Multiple studies had demonstrated that obese
patients are at higher risk after gynecologic,
orthopedic, cardiovascular, urologic, and
transplantation surgery, whereas other studies
have not.
69
Considerations for Management of Obese Patients
Undergoing Nonbariatric Surgery

Dindo: Independent risk factors for postoperative
complications:
◦ Operative severity
◦ Open laparoscopic surgery

Surgeries may last longer, about 25% more time for
laparoscopic than for open cholecystectomy in the
morbidly obese.

Significantly, the wound infection rate was much better after
laparoscopic than after open surgery, which supports the
practice of performing laparoscopic surgery in obese patients
rather than the alternative.
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Anesthesia: same as bariatrics.
70
Fed up with how her diet is going Charlene
takes a more serious aim at her target weight