Week 2 Obesity and Bariatric Surgery Flashcards
1
Q
Define Overweight
A
increased body weight above a standard related to height
2
Q
Define Obesity
A
excessive body weight for the patient’s age, gender and height
Body weight of 20% more or above ideal body weight
3
Q
What is obesity a disorder of?
A
energy balance
4
Q
Define Ideal Body Weight
A
weight associated with maximum life expectancy for a given height and gender
5
Q
How do you calculate IBW for a man?
A
105lb + 6lb for each inch >5ft
6
Q
How do you calculate IBW for a woman?
A
100lb + 5 lb for each inch >5ft
7
Q
What is broca’s index?
A
Height (cm)- x
where x = 100 for males and x= 105 for females
highest allowable weight
8
Q
What is the equation for adjusted body weight?
A
AdBW= 0.4 (ABW-IBW) + IBW
9
Q
What is Lean Body Mass?
A
120% of IBW
It considers increased muscle developed to carry extra body weight
Really only used in obese patients
10
Q
Define BMI
A
accepted measure of body habitus that normalized adiposty for height
11
Q
What is the equation to calculate BMI?
A
weight in kg/ (height in meters) 2
12
Q
What is the overweight BMI?
A
25-29.9kg/m2
13
Q
What is obesity defined as?
A
BMI > 30kg/m2
14
Q
Class 1 Obesity BMI statisfication
A
30-34.9kg/m2
15
Q
Class 2 Obesity BMI statisfication
A
BMI 35-39.9kg/m2
16
Q
Class 3 Obesity BMI statisfication
A
BMI 40-49.9kg/m2
17
Q
Superobese
A
BMI > 50
18
Q
What is obese (BMI >30) associated with? (5)
A
increased morbidity related to stroke, ischemic heart disease, HTN and diabetes
19
Q
Where is android obesity?
A
android fat distribution
abdominal (central) obesity
20
Q
Calculation of LBW (nagelhout)
A
IBW x 1.3
21
Q
Android Obesity is more commonly found in
A
men
22
Q
Android obesity has a higher incidence of
A
metabolic disturbance
23
Q
Android obesity has an increased risk of (4)
A
ischemic heart disease, stroke, diabetes, and death
24
Q
Android obesity is metabolically active causing
A
free fatty acid release, and increase in gluconeogenesis and inhibition of insulin uptake
25
Gynecoid Obesity is
fat around the hips and buttocks
26
Gynecoid obesity is more common in
females
27
Gynecoid obesity is
metabolically static
28
Risk of pathophysiology in obese patients with what waist circumference?
>102cm (40inch) in men
| >89cm or 35inches in women
29
What factors influence obesity?
socialization, age, sex, race, genetics and economic status
30
Associated disturbances with Obesity (12)
```
OSA/Hypoventilation Syndrome
Restrictive lung disease
HTN
CAD
Hyperlipidemia
Delayed gastric emptying/ GERD
Type 2 DM
Gallbladder disease (cholethiasis)
cirrhosis/fatty liver disease (NALD)
venous statis/thromboembolic disease
degenerative joint/disc disease
increased breast, prostate, cervical, uterine, and colorectal cancer
```
31
Respiratory Changes in Obesity (6)
chest wall and lung compliance reduced d/t fat accumulation in thorax and abdomen causes breathing at low lung volumes
thoracic kyphosis/ lumbar lordosis
increased pulmonary blood volume
increased oxygen consumption and carbon dioxide production
high minute ventilation
increased WOB
32
What are the direct lung volume changes in the obese patient?
decreased FRC, VC, inspiratory capacity, total lung capacity and expiratory reserve volume
33
Describe closing capacity in the obese patient
close to or with tidal breathing
34
Smaller lung volumes in the obese patient require
increased metabolic demand, increased work of breathing, closure of small airways with V/Q mismatch and resulting hypoxemia
35
How does progression of respiratory changes in the obese manifest?
lung disease and pulmonary HTN
| PFTs are normal until this occurs
36
Risk Factors of OSA
```
middle age
male
obesity (BMI > 30)
ETOH use
drug induced sleep
abdominal fat distribution
neck girth (41cm)
```
37
What is the neck circumference for men that would be at an increased risk for OSA?
>17 inches
38
What is the neck circumference for women that would be at an increased risk for OSA?
>16inches
39
Define obstructive sleep apnea
changes in airway dynamics during sleep
| can cause physiologic changes endure beyond sleep
40
What is OSA caused by
mechanical obstruction upper air
loss of respiratory drive
or both
41
What are the manifestations of OSA
repeated episodes of apnea/hypoventilation
oxygen desaturation
sympathetic arousal
awakening, leading to fragmented sleep
42
Frequent episodes of apnea during sleep in OSA leads to (7)
chronic hypoxia, hypercapnia, pulmonary systemic vasoconstriction (HTN)
snoring, sleep fragmentation/daytime somnolence, impaired concentration/memory problems, morning headache
43
Types of OSA
Obstructive Sleep Apnea
Central Sleep Apnea
Obesity Hypoventilation Syndrome/Pickwickian Syndrome
44
what is obstructive sleep apnea
cessation of airflow but maintain respiratory effort
| abnormal relaxation of genioglossus & pharyngeal muscles pull tongue forward
45
What is central sleep apnea
cessation of both airflow & respiratory effors
| problem with ventilatory center of medulla
46
What is Obesity Hypoventilation Syndrome/ Pickwickian syndrome
most severe chronic OSA leading to cor pulmonale
| related to extreme obesity
47
What is the gold standard for OSA diagnosis
polysommography
48
How is OSA characterized
apnea >10seconds total cessation of airflow despite respiratory effort against a closed glottis
Hypopnea is 50% reduction in size or number of breaths that lasts at least 10 seconds compared to normal; or a reduction sufficient enough to cause a 4% or more decrease in arterial SaO2
49
Apnea- Hypopnea Index Scale
>30 severe
16-30 moderate
15 or less mild
50
Treatment of OSA
CPAP
| level of pressure required to sustain airway patency determined in sleep study
51
What are the benefits of CPAP for OSA
attenuates hemodynamic responses induced by apnea including BP surges and increased SNS activity
improved neuropsychiatric functioning
less daytime somnolence
52
Treatment of OSA in patients with severe arterial oxygen saturation
nocturnal oxygen with CPAP
53
What are the corrective procedures for OSA
uvulopalatopharyngoplasty (UPPP) and diathermy palatoplasty
54
What is an uvulopalatopharyngoplasty
enlarges airway through removal
55
what is diathermy palatoplasty
heat tissue producing scar which tightens in 6-8 weeks
56
Pathophysiology of OSA
hypoxemia-> hypercarbia-> pulmonary hypertension-> respiratory acidosis during sleep -> RHF-> pulmonary and systemic vasoconstriction-> polycythemia-> systemic hypertension
57
Pickwickian Syndrome is
a complication of extreme obesity/ long term OSA
extreme obesity with hypercapnia, hypoxia, cyanosis induced polycythemia, somnolence and eventual right sided HF and pHTN
58
How do you diagnosis Pickwickian syndrome?
PCO2>45mmHg in an obese patient without COPD
59
How is Pickwickian syndrome different then OSA?
OSA is a nocturnal sleep distribution while OHS is a nocturnal central apnea events (apnea without respiratory effort)
60
Characteristics of Pickwickian syndrome (8)
```
obesity BMI > 30
hypercapnia (PaCO2 >45mmHg in an obese patient without significant COPD)
chronic daytime hypoxemia is better predictor of pHTN and cor pulmonale then presence and severity of OSA
daytime hypersomnolence
pulmonary hypertension
respiratory acidosis
right sided heart failure
airway difficulty
```
61
Airway Changes in Obesity (8)
TMJ and atlanto-axial joint and cervical spine movement limited by upper thoracic and low cervical fat pads
redundant tissue folds in mouth and pharynx = narrowed airway
Short, thick neck circumferences
fat in suprasternal, presternal, posterior cervical and submental regions
shortened distance between mandible & sternal fat pads
OSA= increase risk of excess pharyngeal tissue on lateral walls
62
What do the airway changes in obese patients create?
Difficult mask
| difficult intubation and direct laryngoscopy
63
Cardiovascular changes in obesity (6)
```
increased total blood volume
increased CO
increased RAAS and SNS
HTN
increased risk of CAD
increased Left sided heart pressures and left ventricular hypertrophy
```
64
EKG changes in Obese
left or right ventricular hypertrophy, ischemia and conduction events
65
Increased Left ventricular wall stress causes
hypertrophy, reduced compliance, impaired left ventricular filing (diastolic dysfunction) elevated left ventricular and diastolic pressure progresses to pulmonary edema
66
Obesity Cardiomyopathy
eventual left wall thickening and fails to keep pace with ventricular dilation and systolic dysfunction
67
Hematologic Alternation in Obesity (4)
polycythemia & Hyper-coagulation
Thromboembolic risk
increased intra-abdominal pressure
immobility leads to venostasis
68
Explain how obese patients have an increase risk for DVT
polycythemia leads to increased blood viscosity
| increased fibrinogen factor VII, Factor VIII Von Willebrand factor plasminogen activator inhibitor-1
69
Obese patients have an increased incidence for
hiatal hernias
| gerd and gallbladder disease
70
Risk of aspiration pneumonitis in obese patients are
the same as non-obese individual when following NPO guidelines
71
Hepatic Alternations in Obesity include
fatty infiltration of liver and abnormal LFTs
72
What defines fatty infiltration of the liver in obesity (3)
prevalence of nonalcoholic fatty liver disease
inflammation
cirrhosis and focal necrosis
73
Renal Alternations in Obesity
increased renal plasma flow and increased GFR
Increase renal tubular reabsorption and impaired naturesis secondary to SNS and renin-angiotensin system activation
eventually nephron function can be lost
74
Endocrine Alternations in Obesity
obese patients secrete more insulin, but resistance to the effects of insulin
Metabolic syndrome
75
Name the possible signs of metabolic syndrome?
large waist circumference, high triglyceride levels, low levels of high density lipoproteins (HDL) cholesterol, glucose intolerance and hypertension
76
Musculoskeletal changes in Obesity
osteoarthritis and degenerative joint disease
77
CNS in Obesity
ANS dysfunction
peripherial neuropathies
stroke
idopathetic intracranial hypertension
78
Hyperlipidemia is
increased LDL and decreased HDL cholesterol linked to atherosclerosis
premature coronary artery disease
premature vascular disease
pancreatitis
79
Pharmacokinetics of Obesity
```
increase blood volume and CO
decreased total body water
adipose and lean tissue increaes
varaible alternation in protein binding
organomegaly
```
80
Clearance in Obesity
hepatic clearance unchanged despite histological and LFT alternations
renal clearance of drugs increased (increased GFR, RBF and tubular secretion)
81
Liphophilic drugs have an
increased elimination half-life because of increased Vd, but normal clearance
82
Dosing in Obesity
weak or moderate liphophilicity dose on IBW or LBM
83
Propofol dose and obesity
induction dose should be based on LBW
84
Maintenance dose of propofol
TBW
85
Benzodiazepine Dose in Obesity
highly lipophilic drugs with larger Vd
86
Initial Benzodiazepine Dose
LBW can titrate to TBW
87
Benzodiazepine infusions Dose
LBW
88
Pseudocholinesterase activity increases
as weight increases and ECF increases
| linear relationship
89
Succ Dose in obesity based on
TBW
90
Vec and Roc dose
IBW
91
Cis Dose
TBW
92
General trend of NMB
exhibit prolonged DOA and recovery
93
Fentanyl and Sufentanil
are highly lipophilic
increased Vd and elimination 1/2 life
dose on TBW but then decrease to IBW and response
94
Remifentanil
dosing on IBW
| similar pharmacokinetics with non-obese
95
Precedex
0.2-0.5mcg/kg/min to reduce analgesic and anesthetic requirements
based on TBW
96
Sugammedex in Miller
IBW
97
Sugammadex in Nagelhout
TBW
98
Volatile Anesthetics
avoid N20
| desflurane
99
Appetite Suppressants
| adrenergic reuptake inhibitors- phentermine
decreases appetite and increases metabolic rate
100
S/E of Appetite suppressants
hypertension
| tachycardia
101
Lorcaserin
appetite suppressant
5-HT2C receptor agonist
selective serotonin agonist
reduces food intake through the activation of pro-opiomelanocortin
102
Lipase inhibitors- Orlistat
acts by blocking absorption and digestion of dietary fat and binding lipases in GI tract
103
Pre-Op Evaluation in Obesity
assess patient in non-judgemental way
emphasis should be on difficulties obesity presents to anesthesia provider
discuss the likely post-operative course
airway/respiratory system/cardiovascular/ endo/gi/metabolic/ musculoskeletal
104
Morbid obesity is an independent risk factor for
sudden death from acute PE
105
Thromboprophylaxis includes
heparin
pneumatic compression stockings
LMWH
106
Pulmonary HTN signs
dyspnea, fatigue, syncope, tricuspid reg on echo, ECG (RVH, tall precordial R waves, right axis deviation) prominent pulmonary artery on CXR
107
Obesity have a high incidence of (4)
HTN pulmonary HTN R/L ventricular failure CAD
108
Airway Pre-Op
```
does patient have a history of previous difficult airway
OSA
mouth opening
thyromental distance
interior of the mouth
mallampati classification
neck size
```
109
WHat is the best predictor of problematic intubation?
neck size
110
identifiy signs of severe respiratory disease
orthopnea
sleep apnea
obesity hypoventilation syndrome
previous history of upper airway obstruction especially regarding a past anesthetic
111
STOP BANG
```
snoring
tired
observed
high blood pressure
BMI
age neck size
gender
```
112
Respiratory Pre-Op
```
chest xray
room air on Sao2
ABGs
optimize pulmonary status pre-op
PFTs
--stop smoking
```
113
Cardiovascular Pre-OP
```
signs of HTN, RV and/or LV hypertrophy and pHTN should be assessed
EKG
Chest xray
ECHO
LV ejection fraction
cardiac clearance if needed
previous diet aids
```
114
Endocrine/Metabolic/GI Pre-op
glucose
diabetes non or insulin dependent
reflux history
115
Pre-Op Labs may include
liver function tests
albumin level
glucose
consider clotting studies
116
Aspiration Prophylaxis
H2 receptor antagonist
bicitra
metoclopramide
omeprazole
117
Mechanical Ventilation
PEEP can improve FRC and arterial oxygenation
watch BP
reciruitment manuevers to improve oxygenation
pressure-controlled ventilators help
changing I:E ratio
118
Fluid management
calculation of fluid requirement in obese patient based on lean body weight or IBW
greater blood loss compared to non-obese r/t technical difficulties/extensive surgical dissection
119
What is the #1 problem of emergence in obesity?
respiratory failure
120
Emergence
```
extubation after fully awake and NMB fully reversed, adequate MV confirmed
semi-upright position
wean pressure support w/ peep
oxygenation 100%
placement of nasopharygneal airway
```
121
Ventilatory support post op
CPAP BiPAP
mechanical ventilation
respiratory monitoring
122
Postoperative Anesthesia Pain Management
peripheral nerve blocks with continuous infusions of LA with or without small doses of opioids
local infiltration of wound
judicious use of opioid
123
Bariatric Surgery is reserved for patients
with BMI >40
| or BMI > 35 with related comorbidities not controlled by medical therapy
124
Bariatric surgery is
surgical alteration of small intestine or stomach to promote weight loss
125
Malabsorptive procedures
jejuno-ileal bypass and biliopancreatic diversion
126
Restrictive procedures
vertical banded gatroplasty (VGB) and the adjustable gastric banding (AGB)
127
combined restrictive and minimal malabsorptive is
roux en Y gastric bypass
128
What is the greatest cause of bariatric perioperative 30 day mortality
Pulmonary emboli
129
Laparoscopic Bariatric Surgery
less post-op pain, lower morbidity, faster recovery, less third spacing of fluid, decreased wound infection, smaller incisions
complete NMB important
high risk for mainstem intubation
incidence of rhabdo higher compared with open procedure
130
Prior to gastric diversion need to ensure
all endogastric devices are removed (avoid stapling in place or transection)
131
Avoid in bariatric surgery
blind NG insertion
132
How is the implantable gastric stimulatior implanted via laparoscopy?
2 lead EKG placement on greater curvature of stomach
| SQ electric pulse generator implanted on abdominal wall
133
How does the implantable gastric stimulator work?
simulates gastric smooth muscle, decreases peristalsis
| in theory patients feels less hungry
134
Anesthetic Considerations for the implantable gastric stimulator
avoid N &V
valsalva may dislodge electrodes
EKG interference
135
Pre-medication Pre-Operative Considerations of the Obese Patient
anixolysis and aspiration pneumonitis precautions
136
What is the most important airway assessment pre-operatively?
neck circumference
137
Other Pre-operative considerations for Obese patient
IM injections unreliable
DVT prophylaxis
OSA/OHA increased risk difficulty- pre-op ABG
138
What can hide signs of cardiac failure in Obese?
excess adipose tissue
139
What are pulmonary HTN signs?
dyspnea, fatigue, syncope, tricuspid reg, EKG (RVH, tall precordial R waves, R axis deviation)
prominent pulmonary artery on CXR
140
Positioning Considerations of the Obese Patient
watch OR table weight
| high incidence of pressure sores and nerve injuries
141
What is stacking?
ramped position for intubation to align ear with sternum
142
Monitoring considerations of Obese patient
```
monitors
appropriate sized BP cuff
IV/arterial line access
Consider CCVP or PAP catheter
significant CV or pulmonary disease or when large fluid shifts expected
```
143
Prevention of Thromboembolism
LMW heparin
| pre-op aspirin adn warfin to INR 2.3
144
How to decrease risk of thromboembolism
pre-operative excerise, anti-thrombic drugs, stock prophylaxis, nonpolycycthemic HCT, increased CO an early ambulation
145
What causes the most mortality in the 30 day perioperative period after bariatric surgery?
PE
| x3 more frequent than anastomotic leak with subsequent sepsis
146
What is the most important step of induction for Obese patients?
pre-oxygenation
147
What does pre-oxygenation help with?
decreased FRC, increased O2 consumption, higher incidence of difficult airway
148
Considerations of induction in Obese
```
induction doses altered
consider awake intubation with minimal sedative
RSI- aspiration concerns
May need 2 handed mask
breath sounds difficult to ausculate
PEEP 10cm H2O can be helpful
Routine use of reverse trendelenburg
```
149
Fluid Balance in Obese patient
greater blood loss
less able to compensate for blood loss (low threshold for replacement)
risk of acute tubular necrosis with inadequate fluid replacement
150
Regional Anesthesia in Obese
avoidance of intubation challenges VS technically challenging landmark identification
central neuraxial blockade easier in the lumbar region
Longer needle may be required
US and fluoroscopy have been used to place catheter in epidural space
151
What changes in the LA dose for obese patients?
20-25% reduction
| epidural vascular engorgement and decreased epidural space
