Obesity

OBESITY AND ANESTHESIA
Presenter:
Dr.Tirtha Raj Bhandari
2nd year resident
Department of
Anesthesiology And Intensive
Care
NAMS
2/23/2019 Department of Anesthesiology and Intensive Care 1

CASE
34 years male, with history snoring and night time awakening. weight 125 kg
and 150cm height ,planned for whipple’s operation for peri-ampullary
carcinoma.Airway= Neck circumference 48cm.BP-159/90mmhg,
HR=90bpm.RS=NAD, CVS=S1S2Mo, InvFBS=113mg/dl, TG=300mg/dl. ECG=
feature of left ventricular hypertrophy. ECHO:LVH with Grade I diastolic
dusfunction.Remaining investigation within normal limit.
What are the anesthetic challenges???
Metabolic syndrome??
OSA??
Mortality risk??

Objectives
• To define and classify obesity
• To discuss pathophysiological changes in Obesity
• To discuss common problem in Obesity
• To discuss pharmacological changes in obesity
• To discuss anesthetic concerns in Obesity

OBESITY IS A DISEASE2/23/2019 Department of Anesthesiology and Intensive Care 4

Definition
A chronic metabolic disorder that is primarily induced and sustained
by over-consumption or under-utilization of caloric
substrate.(Medical)
AHA defines obesity as body weight 30% greater than ideal body
weight.
Triceps Thickness= >23mm male, >30mm female

IBW= Ideal body weight (Broca’s index) in kg
Men= Height in centimeters-100
Female= Height in centimeter-105
LBW= Lean Body weight= mass of body –storage lipid/fat(1.3*IBW)
TBW= Total body weight = actual weight of body
Corrected body weight/adjusted body weight= ideal body weight +
0.4*excess body weight

WHO Classification
Category BMI(kg/m2)
Normal 18.5-25
Pre-Obese/Overweight 25-30
Obese-I 30-35
Obese-II 35-40
Obese-III(Morbid) >40

BMI=Body mass index= Wt(kg)/Ht(m2)
Male Female
Underweight 17.6-20.6 17.6-19
Normal(ideal) 20.7-26.4 19.1 -25.8
Marginally overwt 26.5-27.8 25.9-27.2
Overweight 27.9-31.1 27.3-32.3
Obesity 31.2-34.9 32.4-34.9
Severe Obesity 35-39.9 Same
Morbid Obesity
Super Obesity
>40, >35(DM/HTN)
>50
Same

Epidemiology
• Around 1/3rd of US population both children and adult are either over
weight ot obese.

CONTD
• Reduction in life expectancy by 4-7 years.
• Increase risk of perioperative morbidity and mortality
• More incidence of coronary vascular disease and cerebrovascular
accidents

Classification
Peripheral Obesity:
• Gynoid/Gluteal pattern
• Pear shape
• Adipose tissue deposition mainly in the lower body
part
Central Obesity:
Android/Cushinoid
Apple shape
Adipose tissue predominantly in the upper body part
Has greater association with OSA(Obstructive sleep
apnea)

Causes
• Genetic
• Individual factors
• Environmental Factor
• Eating disorder
• Psychology
• Cultural factor
• Endocrine disease
• Drug induced

Metabolic Syndrome
• Mediated through a adipo-cytokines, such as acute phase reactants
(increase in CRP and SAA), adipokines (decrease in adiponectin or
increase in leptin or resistin), macrophage derived factors and pro-
thrombotic factor (increase in PAI-1, fibrinogen, and factor-VII)

Pathophysiological Changes In Obesity

Airway
Deposition of adipose tissue into the pharyngeal structure
 So likelihood of relaxation is high
Collapse of the soft walled retroglossal space or oropharynx between
uvula and epiglottis.
Ellipse with long axis transverse  epilse with long axis antero-
posterior.
The muscle that open pharynx during expiration will not function well
in remodel pharynx

Respiratory System
PFT and lung volumes are uniformly altered in obesity.
Vt is normal or increase or decrease in pickwickian type of obesity
IRV and ERV-decreases
RV=normal
FRC= decreases
VC=Decreases
TLC=Decreases
Central> Peripheral decrease in forced vital capacity and FEV and TLC.
Maximal voluntary ventilation also decreases
DLCO(Diffusion lung for CO) is usually normal.

Respiratory System
1/CRS =1/CL +1/CCW =Compliance
Compliance of the respiratory system mainly depend on compliance of
lung and chest wall
Compliance of lung usually unaltered in obesity, may decrease if
pulmonary or circulatory abnormalities present like Pulmonary
hypertension.
Compliance of chest wall is less is obesity
So overall there is decrease in compliance in respiratory system.

Respiratory System
Resistance of the airway increases.
At lower lung volume reduction in caliber of small airways
Increase in resistance up to 30% in simple obesity may reach up to 100% in
Obesity Hypoventilation syndrome).
Resistance increases further in supine position ,
FRC is reduced in morbidly obese individuals, may be below the closing
capacity(CC)
FRC decrease worsen in supine position, Trendelenburg position and
anesthetized(muscle relaxant) individuals,
Closing capacity also decreases in obesity

Respiratory System
So small airway start to collapse , V/Q mismatch occurs, RL shunt
occurs.
Increase in A-a gradient
This can be improve by recruitment maneuver and reverse
Trendelenburg position.
Alveolar ventilation decreases
This is mainly due to upper airway obstruction/collapse and decrease
in ERV and FRC
Risk of hypoxemia and atelectasis
Increase in blood flow to lung due to increase in CO can develop
pulmonary hypertension

Ventilatory Patterns
• Alveolar HyperventilationIn response to hypoxic drive, Occurs in
young and active subject, PaCo2 approximately 35mmhg
• Periodic Nocturnal Alveolar Hypoventilation with normal day time
values, hallmarks of OSAHs
• Daytime/Constant Alveolar Hypoventilation Hallmarks of
Obstructive Hypoventilation Syndrome and Pickwickian syndrome.

Respiratory System
Work of Breathing(WOB) increases in MO and
Fourfold increase in Oxygen cost of breathing
Due to following reason
1)Decrease in lung and chest wall compliance ,
2) increase in airway resistance,
3)Increase inspiratory load due to adipose tissue mass and
4) elevated pharyngeal and nasopharyngeal resistance.

Respiratory system

OSA/OSH
OSA(Obstructive sleep apnea):
Cessation of airflow for more than 10 sec despite the continuing
ventilatory efforts,
5 or more times/hour
associated with a decrease in arterial oxygen saturations(SpO2) of
greater than 4%.
OSH(Obstructive sleep hypopnea):
decrease in airflow more than 50% for more than 10 sec,
15 or more times/ hour
associated with decrease in SpO2 more than 4%.

OSA/OSH
Common Cardiovascular problems are-
Systemic and pulmonary HTN, various cardiac arrhythmias, MI, Rt and
Lt ventricular hypertrophy and eventually failure.
Hypoxia and hyper-carbia are common
Associated with snoring, sleep disturbance from increase ventilatory
effort, hyper-somnolence, and altered cardiovascular function.

Proposed Mechanism:
1)Altered elipse of pharynx with transverse axis to antero-posterior.
2) Decreased/ reduced patency of upper airway due to compression by
extrinsic adipose tissue.
3)The reduction if lung volume is also responsible for the reduced
patency/collapse of upper airways

Piwickian syndrome /Obesity Hypoventilation Syndrome
• PS is most severe form of OSA when BMI>50.
• There will be hypoxia and hypercarbia, with heavy night time snoring
and periodic respiration ,hypersomnolence, secondary polycythemia,
Rt and Lt ventricular hypertrophyfailure
• Loss of REM sleep  lead to hypersomnolence, behavioural and
cognitive changes
• Due to loss of breathing/ventilatory control mechanism  there will
of apneic episodes or apnea without ventilatory efforts OHS
• Can lead to bradycardia during apneic episode.
• Risk of Pulmonary Hypertension/Corpulmonale.

OSA vs OHS

Polysomnography
• EEG: 2-6 channel to measure electrical activity of brain and to
document sleep cycle.
• EOG: electro-oculogram channel to distinguish rapid movement of
eye from Non-REM.
• Chin EMG: To measure/monitor arousal and activity of upper
airway(Genioglossus and digastric muscle)
• An Airway microphone: to monitor airflow from the nose and mouth.
• Elastic bell placed at chest to monitor respiratory effort
• Infrared video camera- To monitor body position
• ECG, Pulse Oximetry and two leg EMG-to monitor leg movements.

Cardiovascular System
Total and circulating blood volume increase
Although absolute blood volume is expanded the relative blood
volume is decreased
The increase in blood volume and decrease in SVR results in
augmentation of CO.
CO increase by Stroke volume not by HR (unchanged) can lead to
systemic HTN
Increase in arterial resistance
Left ventricular stress increases  eccentric LV hypertrophy and
eventually lead to LV dysfunction

Cardiovascular System
Pulmonary hypertension due to hypoxia induced vasoconstrcition
and increase CO(Blood volume).
Due to hypertrophy of LV on longstanding chronic volume overload
compliance of LV decreases can lead to diastolic dysfunction.
Finally patient can develop CCF.
Due to fatty deposition/infiltration in cardiac system, predisposes the
obesity individuals to sudden cardiac death.
Increase risk of CAD, especially with metabolic syndrome.

Gastrointestinal System
• Linear increase in intra-abdominal pressure with increasing body weight
• Gastro-paresis and decrease intestinal motility
• Increase incidence of GERD, decreased gastric PH
• Increase incidence of hiatal hernia, and impaired gastro-esophageal anti-
reflux
• Normal gastric emptying rate with larger pouch, so that after controlled
fasting we perform surgery/bariatric surgery
• 90% of fasting obesity exceeds Mendelson’s criteria, gastric volume
>0.35/kg and PH<2.5.
• Higher Incidence of colorectal malignancies

Hepato-biliary System
• Increase incidence of hepato-biliary disease such as , cholelithiasis,
hepatitis, intra and extra-hepatic cholestasis, hepatic steatosis and
cirrhosis.
• Acute and chronic pancreatitis risk is more
Renal System/Fluid and Electrolytes
• Normal adult water percentage is 70% and blood volume is 70ml/kg
• But in obese individuals- total body water may be down to 40% and
blood volume 50ml/kg.
• Avoid rapid hydration cardiopulmonary compromise

Nervous System
Brain atrophy and reduced gray matter
Altered cognitive dysfunction
Altered hippocampal formation and structure
Association with Alzheimer's disease and dementia
Association with polyneuropathy
Altered autonomic response/ catabolic and anabolic response
Increased risk of cerebrovascular accidents(stroke)
Decreased subarachnoid space and epidural space

Lancet Neurol. 2017 Jun; 16(6): 465–477.

Musculoskeletal System
• Increase incidence of osteoarthritis
• Hyper-uricemia  Gout
• Pressure sore/necrosis
Hematological System
• Secondary polycythemia- Increase in Hb / Hematocrite
• Mainly due to longstanding hypoxia

Endocrine/Metabolic Changes
• Increase risk of DM type-II
• 80-90% of non-ketotic diabetes are obese
• Increase in insulin secretion and resistance
• Increase in O2 consumption and CO2 production
Associated endocrine diseases are:
Hypothyroidism
Cushing’s disease
Insulinoma
Hypogonadism and
Hypothalamic disorders

Peripheral Vascular System
• Increase risk of thrombi formation in both arterial and venous system
• Risk of DVT is high. DVT possibly due to
Polycythemias
Increase venous pressure
Immobilization
Increase intra-abdominal pressure
• Risk of pulmonary embolism
• DVT prophylaxis should be considered in obese

Reproductive system
• Hypogonadism
• Abnormal menses
• Polycystic ovarian syndrome
• Infertility

Psychological Changes
• Depression
• Anxiety
• Emotional distress
• Discrimination
• Social stigmatization
• Fear, Hostility and insecurity

Pharmacological Consideration
• Overdosing of premedication and anesthesia drug is very common in
obese.
• Doses should be calculated as per lean body weight(mostly)
• Avoid IM injection due to unpredictable absorption
• If possible avoid narcotics and sedation
• Increase level of alfa1 glycoprotein level
• Ideal Anesthetic gas:
Should be insoluble
Resistant to metabolic degradation
Without lipid depot compartmentalization
And rapid return of airway reflexes

Lipid Soluble Water Soluble
Increase volume of distribution Limited volume of distribution
Larger loading dose to produce same plasma
concentration but maintenance doses less frequent
Slow clearance
Doses not influenced by fat stores
Doses based on actual body weight(Total body weight) Doses based on ideal body weight to avoid
overdosing

Pharmacological Consideration

Anesthetic Concerns
• Pre-operative
• Intra-operative
• Post-operative

Pre-anesthetic Check Up
Detail History
Review of Systems
Physical Examination
Laboratory tests

Review of system
• GI: Gastroesophageal Reflux, Hiatus hernia
• Hepatobiliary: Cholelithiasis, Hetatic steatosis and hepatitis, cirrhosis
• CVS: HTN, CAD, Dyslipidaemia, features of right and left heart failure
• CNS: Cognitive dysfunction, neuropathy
• Endocrine: Dm-II, Hypothyroidism, Hypogonadismetc
• Respiratory: COPD, Bronchial Asthma, Restrictive pattern of lung
disease, smoking history, exercise tolerance, hx of hypoventilation
and somnolence
• Psychology: Depression, Anxiety

Physical Examination
A)Airway Assessment:
1)Routine
Atlanto-occipital joint extention
Mallampati Grading
TMJ movement
Inter-incisor distance
Mento-hyoid distance
Dentation status
2)Extra
1)Pretracheal adipose thickness
2)Neck circumference
3) Hypertrophic tonsils and
adenoids
B) CVS examination
C) Respiratory Examination etc..

Investigation
• CBC
• RFT
• LFT
• PFT
• ECHO
• ECG
• Chest X-ray
• ABG
• Cardiorespiratory tolerance test- Dobutamine stress test
• Bleeding profile

ECG-Look for • Increase HR
• Increase PR interval
• Increase QRS interval
• Increase or Decrease QRS
voltage
• Increase QTc interval
• Increase QT dispersion
• Feature of angina/ MI like, St-T
wave changes
• Left axis deviation etc

Premedication
Better to avoid sedatives and hypnotics till OR
In OR we can start Dexmedetedomidine or other opioids and
Benzodiazepam with proper monitoring
Aspiration prophylaxis: prokinetic (metoclopramide), H2 blocker
PONV prophylaxis Dexamethasone/Ondansetron
To decrease secretion Glycopyrrolate
Multimodal analgesia  to reduce pre-induction anxiety, decreases
immediate post op respiratory depression cause by pain

Perioperative challenges
Needs 2 days of liquid diet and >8 hours fasting
Difficult I/V access
Difficult bag and mask ventilation
Difficult to insert invasive lines – CVP and arterial line
Difficult to do regional anesthesia
Monitoring difficulty- due to unavailability of appropriate size instruments
Difficult intubation
Awake intubation??
Difficulty in positioning
Post-extubation respiratory failure more due to collapse of upper airway
Difficulty for transportations

Intraoperative
• Positioning
• Monitoring
• Pre-oxygenation
• Apneic Oxygenation
• Induction
• Maintenance
• Ventilator settings
• Extubation

Positioning
Cardiorespiratory compromise is common in obese individual.
Trendelenburg Position> Supine>Reverse Trendelenburg Position/Semi-
sitting position
Ulnar neuropathy
Pressure sore
Positioning with ramp for intubation for anticipated difficult airway

Monitoring
• NIBP
• ECG
• SpO2
• eTCO2
• Arterial line
• Temp
• esophageal stethoscope
• EEG/BIS
• CVP
• Pulmonary artery catheter

Pre-oxygenation
• Pre-oxygenation is more important in obese
• Less FRC than non-obese
• CPAP for 3-5min technique improves pre-oxygenation with sedation
with fentanyl, midazolam and propofol
• More oxygen utilization
• Less safe apnea time
• So apneic ventilation is important during intubation to prevent
desaturation
• Reverse Trendelenburg/semi-sitting to improve FRC

Apneic Oxygenation
Every minute around 250ml oxygen utilized by our body
And around 200ml of CO2 produced in our body
 10% of CO2 accumulated in alveoli and 90% remain in blood as
bicarbonates
 230ml /min vacuum will be created, which will produce sucking
effect for O2
Usually there is fall in PaO2 with rise in PaCO2
PaO2 can keep above 100mmhg up to 100 minute, but till this time
patient may die because of acidosis(PH<6.8)

Induction
After proper preo-xygenation rise in SpO2, FEO2>88-90
Induce with thipentone/propofol
Muscle relaxant- Succinyl choline(1mg/kgTBW)/
VEC/ROC/Cisatracurium (best but expensive)
Intubation and confirmation of proper tube placement with various
methods

Maintenance
Proper ventilatory settings
Desflurane is best anesthetic gas
Desflurane>Sevoflurane>Isoflurane for fast recovery
Ramifentanyl + Dexmedetomidine for TIVA(infusion) do not have
much lipid compartmentalization effect
Dense muscle relaxation for proper ventilation with TOF T4/T1>0.9.
Cis atracuronium is best as it is eliminated by hoffmann’s reaction,
but it is expensive
Rocuronium/Vecuronium

Ventilator Settings
CPAP during
FIO2 <0.8
Recruitment maneuver after induction then periodically
Pressure control volume guarantee
Vt =6-10ml/kg for IBW
PEEP: 10-12 cmH2O
I:E=1:1
Inspiratory Pressure<30cmH2O

Extubation criteria
Intact neurological status, fully awake and alert with head lift >5sec
Hemodynamic stability
Normothermic >36C
Full reversal of neuromuscular blocking agents confirmed with TOF(T4/ T1
=0.9)
RR >10, <30/min
Baseline peripheral oxygenation as judged by pulse oxymetry(SpO2>95%,
on FIO2<0.4)
Acceptable blood gas(FIo2<0.4)= PH;7.35-7.45, PaO2>80mmhg,
PaCo2<50mmhg
Acceptable respiratory mechanics MIP >30cmH2o, VC>10ml/kg IBW,
Vt>5ml/kg/IBW
Acceptable Pain Control
No demontrated/suspected lab abnormalities2/23/2019 Department of Anesthesiology and Intensive Care 74

Regional Vs GA
• Decrease incidence of PONV and respiratory depression
• Less post-operative pulmonary complications
• Improved Cardiac function(decrease LV stroke work index)
• Decrease O2 consumption
• Earlier return of pulmonary function
• Earlier return of GI function
• Less incidence of DVT

Challenges for Regional
Technical difficulties, positioning difficulties
Dose Adjustment
Logistics
USG guided
Increase incidence of epidural failure
High change of catheter dislodgement
Decrease in epidural space so unpredictable spread
Risk of respiratory depression if we use opioids intra-
thecally/epidural

Post-operative
• Adequate pain management with multimodal analgesia
• Opioids better to avoid if possible
• Oxygen supplementation
• Proper positioning of bed
• Adequate Monitoring
• Management of common post op problems like
1)PONV
2)Venous thromboembolism
3)Hemodynamic instability
4)Hypoxemia

Post-operative Hypoxemia
Common problem in post-op phage. Cause might be
1) Atelectasis
2) Reversion to restrictive pattern of breath
3) Increase use of accessory muscle
4) Decrease FRC from pain, positioning
5) Residual effect of anesthetic agents and muscle relaxant
respiratory depression
6) Parietal peritonium iiritation by carbonic acid(lap surgery)
7) Early ventilatory failure may need re-intubation
8) Positional ventilatory collapse

How to prevent pulmonary complication???
• Early ambulation
• Chest physical ambulation and spirometry
• Encourage elective coughing
• Avoid prolong recumbency
• Can give ventilatory with CPAP/BIPAP in immediate post-op phase

Thromboprophylaxis
Criteria for Thromboprophylaxis
1) Prolonged immobilization
2) Total theatre time >90min
3) Age >60 years
4) BMI >30kg/m2
5) Cancer
6) Dehydration
7) Family history of VTE

Thromboprophylaxis

ANY QUESTIONS????

Summary
• Proper assessment is necessary
• Better to avoid sedative/hypnotics during premedication
• Pathophysiological changes are significant in obesity
• Positioning is important for respiratory management and intubation
• Dose adjustment is important as risk of overdose
• Fluid management should be done cautiously
• PACU and Post op care and monitoring significantly improves
outcome

References
• Miller’s anesthesia 8th edition
• Barash anesthesia 8th edition
• Yao and Artesio’s Anesthesiology 8th edition
• British Journal of Anesthesiology
• Lancet Neurol. 2017 Jun; 16(6): 465–477.
• UpToDate

THANK YOU

Obesity

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Obesity

Similar to Obesity (20)

More from Tirtha Raj Bhandari,MD

More from Tirtha Raj Bhandari,MD (8)

Recently uploaded

Recently uploaded (20)

Obesity

Editor's Notes