Week 2 Obesity and Bariatric Surgery Flashcards
Define Overweight
increased body weight above a standard related to height
Define Obesity
excessive body weight for the patient’s age, gender and height
Body weight of 20% more or above ideal body weight
What is obesity a disorder of?
energy balance
Define Ideal Body Weight
weight associated with maximum life expectancy for a given height and gender
How do you calculate IBW for a man?
105lb + 6lb for each inch >5ft
How do you calculate IBW for a woman?
100lb + 5 lb for each inch >5ft
What is broca’s index?
Height (cm)- x
where x = 100 for males and x= 105 for females
highest allowable weight
What is the equation for adjusted body weight?
AdBW= 0.4 (ABW-IBW) + IBW
What is Lean Body Mass?
120% of IBW
It considers increased muscle developed to carry extra body weight
Really only used in obese patients
Define BMI
accepted measure of body habitus that normalized adiposty for height
What is the equation to calculate BMI?
weight in kg/ (height in meters) 2
What is the overweight BMI?
25-29.9kg/m2
What is obesity defined as?
BMI > 30kg/m2
Class 1 Obesity BMI statisfication
30-34.9kg/m2
Class 2 Obesity BMI statisfication
BMI 35-39.9kg/m2
Class 3 Obesity BMI statisfication
BMI 40-49.9kg/m2
Superobese
BMI > 50
What is obese (BMI >30) associated with? (5)
increased morbidity related to stroke, ischemic heart disease, HTN and diabetes
Where is android obesity?
android fat distribution
abdominal (central) obesity
Calculation of LBW (nagelhout)
IBW x 1.3
Android Obesity is more commonly found in
men
Android obesity has a higher incidence of
metabolic disturbance
Android obesity has an increased risk of (4)
ischemic heart disease, stroke, diabetes, and death
Android obesity is metabolically active causing
free fatty acid release, and increase in gluconeogenesis and inhibition of insulin uptake
Gynecoid Obesity is
fat around the hips and buttocks
Gynecoid obesity is more common in
females
Gynecoid obesity is
metabolically static
Risk of pathophysiology in obese patients with what waist circumference?
> 102cm (40inch) in men
>89cm or 35inches in women
What factors influence obesity?
socialization, age, sex, race, genetics and economic status
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
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
What are the direct lung volume changes in the obese patient?
decreased FRC, VC, inspiratory capacity, total lung capacity and expiratory reserve volume
Describe closing capacity in the obese patient
close to or with tidal breathing
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
How does progression of respiratory changes in the obese manifest?
lung disease and pulmonary HTN
PFTs are normal until this occurs
Risk Factors of OSA
middle age male obesity (BMI > 30) ETOH use drug induced sleep abdominal fat distribution neck girth (41cm)
What is the neck circumference for men that would be at an increased risk for OSA?
> 17 inches
What is the neck circumference for women that would be at an increased risk for OSA?
> 16inches
Define obstructive sleep apnea
changes in airway dynamics during sleep
can cause physiologic changes endure beyond sleep
What is OSA caused by
mechanical obstruction upper air
loss of respiratory drive
or both
What are the manifestations of OSA
repeated episodes of apnea/hypoventilation
oxygen desaturation
sympathetic arousal
awakening, leading to fragmented sleep
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
Types of OSA
Obstructive Sleep Apnea
Central Sleep Apnea
Obesity Hypoventilation Syndrome/Pickwickian Syndrome
what is obstructive sleep apnea
cessation of airflow but maintain respiratory effort
abnormal relaxation of genioglossus & pharyngeal muscles pull tongue forward
What is central sleep apnea
cessation of both airflow & respiratory effors
problem with ventilatory center of medulla
What is Obesity Hypoventilation Syndrome/ Pickwickian syndrome
most severe chronic OSA leading to cor pulmonale
related to extreme obesity
What is the gold standard for OSA diagnosis
polysommography
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
Apnea- Hypopnea Index Scale
> 30 severe
16-30 moderate
15 or less mild
Treatment of OSA
CPAP
level of pressure required to sustain airway patency determined in sleep study
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
Treatment of OSA in patients with severe arterial oxygen saturation
nocturnal oxygen with CPAP
What are the corrective procedures for OSA
uvulopalatopharyngoplasty (UPPP) and diathermy palatoplasty
What is an uvulopalatopharyngoplasty
enlarges airway through removal
what is diathermy palatoplasty
heat tissue producing scar which tightens in 6-8 weeks
Pathophysiology of OSA
hypoxemia-> hypercarbia-> pulmonary hypertension-> respiratory acidosis during sleep -> RHF-> pulmonary and systemic vasoconstriction-> polycythemia-> systemic hypertension
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
How do you diagnosis Pickwickian syndrome?
PCO2>45mmHg in an obese patient without COPD
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)
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
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
What do the airway changes in obese patients create?
Difficult mask
difficult intubation and direct laryngoscopy
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
EKG changes in Obese
left or right ventricular hypertrophy, ischemia and conduction events
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
Obesity Cardiomyopathy
eventual left wall thickening and fails to keep pace with ventricular dilation and systolic dysfunction
Hematologic Alternation in Obesity (4)
polycythemia & Hyper-coagulation
Thromboembolic risk
increased intra-abdominal pressure
immobility leads to venostasis
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
Obese patients have an increased incidence for
hiatal hernias
gerd and gallbladder disease
Risk of aspiration pneumonitis in obese patients are
the same as non-obese individual when following NPO guidelines
Hepatic Alternations in Obesity include
fatty infiltration of liver and abnormal LFTs
What defines fatty infiltration of the liver in obesity (3)
prevalence of nonalcoholic fatty liver disease
inflammation
cirrhosis and focal necrosis
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
Endocrine Alternations in Obesity
obese patients secrete more insulin, but resistance to the effects of insulin
Metabolic syndrome
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
Musculoskeletal changes in Obesity
osteoarthritis and degenerative joint disease
CNS in Obesity
ANS dysfunction
peripherial neuropathies
stroke
idopathetic intracranial hypertension
Hyperlipidemia is
increased LDL and decreased HDL cholesterol linked to atherosclerosis
premature coronary artery disease
premature vascular disease
pancreatitis
Pharmacokinetics of Obesity
increase blood volume and CO decreased total body water adipose and lean tissue increaes varaible alternation in protein binding organomegaly
Clearance in Obesity
hepatic clearance unchanged despite histological and LFT alternations
renal clearance of drugs increased (increased GFR, RBF and tubular secretion)
Liphophilic drugs have an
increased elimination half-life because of increased Vd, but normal clearance
Dosing in Obesity
weak or moderate liphophilicity dose on IBW or LBM
Propofol dose and obesity
induction dose should be based on LBW
Maintenance dose of propofol
TBW
Benzodiazepine Dose in Obesity
highly lipophilic drugs with larger Vd
Initial Benzodiazepine Dose
LBW can titrate to TBW
Benzodiazepine infusions Dose
LBW
Pseudocholinesterase activity increases
as weight increases and ECF increases
linear relationship
Succ Dose in obesity based on
TBW
Vec and Roc dose
IBW
Cis Dose
TBW
General trend of NMB
exhibit prolonged DOA and recovery
Fentanyl and Sufentanil
are highly lipophilic
increased Vd and elimination 1/2 life
dose on TBW but then decrease to IBW and response
Remifentanil
dosing on IBW
similar pharmacokinetics with non-obese
Precedex
0.2-0.5mcg/kg/min to reduce analgesic and anesthetic requirements
based on TBW
Sugammedex in Miller
IBW
Sugammadex in Nagelhout
TBW
Volatile Anesthetics
avoid N20
desflurane
Appetite Suppressants
adrenergic reuptake inhibitors- phentermine
decreases appetite and increases metabolic rate
S/E of Appetite suppressants
hypertension
tachycardia
Lorcaserin
appetite suppressant
5-HT2C receptor agonist
selective serotonin agonist
reduces food intake through the activation of pro-opiomelanocortin
Lipase inhibitors- Orlistat
acts by blocking absorption and digestion of dietary fat and binding lipases in GI tract
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
Morbid obesity is an independent risk factor for
sudden death from acute PE
Thromboprophylaxis includes
heparin
pneumatic compression stockings
LMWH
Pulmonary HTN signs
dyspnea, fatigue, syncope, tricuspid reg on echo, ECG (RVH, tall precordial R waves, right axis deviation) prominent pulmonary artery on CXR
Obesity have a high incidence of (4)
HTN pulmonary HTN R/L ventricular failure CAD
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
WHat is the best predictor of problematic intubation?
neck size
identifiy signs of severe respiratory disease
orthopnea
sleep apnea
obesity hypoventilation syndrome
previous history of upper airway obstruction especially regarding a past anesthetic
STOP BANG
snoring tired observed high blood pressure BMI age neck size gender
Respiratory Pre-Op
chest xray room air on Sao2 ABGs optimize pulmonary status pre-op PFTs --stop smoking
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
Endocrine/Metabolic/GI Pre-op
glucose
diabetes non or insulin dependent
reflux history
Pre-Op Labs may include
liver function tests
albumin level
glucose
consider clotting studies
Aspiration Prophylaxis
H2 receptor antagonist
bicitra
metoclopramide
omeprazole
Mechanical Ventilation
PEEP can improve FRC and arterial oxygenation
watch BP
reciruitment manuevers to improve oxygenation
pressure-controlled ventilators help
changing I:E ratio
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
What is the #1 problem of emergence in obesity?
respiratory failure
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
Ventilatory support post op
CPAP BiPAP
mechanical ventilation
respiratory monitoring
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
Bariatric Surgery is reserved for patients
with BMI >40
or BMI > 35 with related comorbidities not controlled by medical therapy
Bariatric surgery is
surgical alteration of small intestine or stomach to promote weight loss
Malabsorptive procedures
jejuno-ileal bypass and biliopancreatic diversion
Restrictive procedures
vertical banded gatroplasty (VGB) and the adjustable gastric banding (AGB)
combined restrictive and minimal malabsorptive is
roux en Y gastric bypass
What is the greatest cause of bariatric perioperative 30 day mortality
Pulmonary emboli
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
Prior to gastric diversion need to ensure
all endogastric devices are removed (avoid stapling in place or transection)
Avoid in bariatric surgery
blind NG insertion
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
How does the implantable gastric stimulator work?
simulates gastric smooth muscle, decreases peristalsis
in theory patients feels less hungry
Anesthetic Considerations for the implantable gastric stimulator
avoid N &V
valsalva may dislodge electrodes
EKG interference
Pre-medication Pre-Operative Considerations of the Obese Patient
anixolysis and aspiration pneumonitis precautions
What is the most important airway assessment pre-operatively?
neck circumference
Other Pre-operative considerations for Obese patient
IM injections unreliable
DVT prophylaxis
OSA/OHA increased risk difficulty- pre-op ABG
What can hide signs of cardiac failure in Obese?
excess adipose tissue
What are pulmonary HTN signs?
dyspnea, fatigue, syncope, tricuspid reg, EKG (RVH, tall precordial R waves, R axis deviation)
prominent pulmonary artery on CXR
Positioning Considerations of the Obese Patient
watch OR table weight
high incidence of pressure sores and nerve injuries
What is stacking?
ramped position for intubation to align ear with sternum
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
Prevention of Thromboembolism
LMW heparin
pre-op aspirin adn warfin to INR 2.3
How to decrease risk of thromboembolism
pre-operative excerise, anti-thrombic drugs, stock prophylaxis, nonpolycycthemic HCT, increased CO an early ambulation
What causes the most mortality in the 30 day perioperative period after bariatric surgery?
PE
x3 more frequent than anastomotic leak with subsequent sepsis
What is the most important step of induction for Obese patients?
pre-oxygenation
What does pre-oxygenation help with?
decreased FRC, increased O2 consumption, higher incidence of difficult airway
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
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
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
What changes in the LA dose for obese patients?
20-25% reduction
epidural vascular engorgement and decreased epidural space
