that is primarily
sustained by an
over consumption or
under utilization of
Obesity is a
“Across the globe Obesity
become the most common
Nutritional disorder and it is
second only to smoking as a
preventable cause of death.
In anesthetic practice it
present special challenges
for both regional and
INCIDENCE Worldwide adult
In Affluent cultures, the poor have
the highest prevalence (27% US and
17% UK population)
In Developing world, affluent are at
the highest risk.
Obese school children 60-85%
Lean Body Mass Formula
Lean Body Mass = Body Weight –
(Body Weight x Body Fat %) :
Lean body mass is comprised of
everything in your body besides body
Your lean body mass includes:
The Broca Index
Body mass Index
The Broca`s Index
Ideal body weight(IBW) (kg)
◦ For Female = Height (cm) – 105
◦ For Male = Height (cm) – 100
BMI=Body Weight (kg)/
BMI is defined as the patient's
weight, measured in kilograms, divided
by the square of the patient's height,
measured in meters, which yields a
measurement bearing the unit kg/m2.
Overweight is defined as a BMI of >25
Obesity as a BMI >30
Extreme obesity (old term "morbid
obesity") as a BMI of >40.
Super Super Obese
method for quantifying obesity includeSkin fold thickness,Densiometry(under water
Increased blood volume and cardiac output
leading to cardiomegaly, left ventricular
hypertrophy and a potential for left
Hypertension and ischaemic heart disease
Venous access can sometimes be difficult.
Thromboembolism risk is increased.
The risk of pulmonary embolus and DVT is
Venous return is reduced.
Reduced compliance (both chest wall and lung),
in the airway resistance and reduced FRC will
pre-dispose to atelectasis, increased shunt and
70% in work of breathing and a four fold in
the Oxygen cost of breathing occur in case of
Pulmonary vasoconstriction, pulmonary
hypertension and right ventricular hypertrophy.
These patients must be pre-oxygenated as they
desaturate much quicker than non-obese (3–5
times).decrease in FRC impairs the ability of
obese pts to tolerate periods of apnea ,such as
during direct laryngoscopy for tracheal
Inspiratory reserve volume(IRV),
expiratory reserve volume(ERV),
functional residual capacity(FRC),
total lung capacity(TLC) and
minute ventilation(MV)( )
tidal volume(TV) and residual volume(RV) (→).
FRC may be below the closing capacity resulting
in the small airway closure→ V/P mismatch→
right to left shunting and hypoxemia
General anesthesia will accentuate these changes such that a
50% decrease in FRC occurs in obese anaesthetised pts
compared with a 20% decrease in non obese individuals..
◦ Supine Position
◦ Trendelenberg position
Oxygen consumption and carbon dioxide production
There is a higher incidence of difficult laryngoscopy
The incidence of difficult intubation in morbid
obesity is around 13% Altered anatomy:
Increase in soft tissue
Reduced head and neck mobility
Restricted mouth opening
Obstructive sleep apnoea- 5%
Airflow cessation of >10 secs. and characterised by
frequent episodes of apnea or hypopnea during sleep.
◦ Large collar size (over 16.5 inches)
◦ Evening alcohol consumption
◦ Pharyngeal abnormalities
PATHOPHYSIOLOGY:Passive collapse of the
pharyngeal airway during deeper planes of sleep.
Snoring and intermittent airway obstruction
Resultant hypoxaemia and hypercapnia
Arousal and disruption of sleep
Pathophysiology of Sleep Apnea
Awake: Small airway + neuromuscular compensation
hypoxia & hypercapnia
Loss of neuromuscular
Arousal from sleep
Obstructive Sleep Apnea Hypopnea
5 or more apneic(complete cessation of air flow) events or 15 or
more hypopneic(50% reduction of air flow) events per hour of
sleep despite of maintaining adequate ventilatory capacity
associated with a decrease in SpO2 ≥ 4%.
hypercarbia → rptd stimulation of resp centre → gradual
hypoventilation,Hypercapnia ( OHS)
Pickwickian Syndrome is OHS with cor pulmonale.
Obesity hypoventilation syndrome
Loss of the sensitivity to hypercarbia
resulting in a combination of hypoxia, Cor
Pulmonale and Polycythaemia,respiratory
acidosis,pulmonary hypertension,and right
Diagnosis –Polysomnography (Apnea-Hypopnea
index (AHI)), A score of 5-15 is „mild OSA‟,
15-30 „moderate‟, and „severe OSA‟ is over 30
◦ Removal of precipitants
◦ Weight loss
◦ Nocturnal CPAP
OSA or OHS
Increased blood volume
Increased cardiac output
Adams jp murthy PG;obesity in anesthesia and intensive care.br j anaesth
This presents the
a patient who may
be difficult to
intubate and will
Anatomic changes affecting the
Deposit of adipose tissue in the lateral
Deposit of adipose tissue external to the upper
Presence of hypopharyngeal adipose tissue
Presence of pretracheal adipose tissue
Alteration in the shape of the pharynx(long axis
of ellipse transverse to ellipse ant- post)
↓efficiency of the anterior pharyngeal dilator
Increased acidity and volume of gastric
Hiatus hernia and gallstones(due to
hypercholestrolemia) are common
Increased intra-abdominal pressure.
There is a higher risk of regurgitation and
aspiration requiring rapid sequence
induction if a difficult airway is not
Fatty infiltration of liver (denoting the
duration of obesity)
Tracheal extubation should be undertaken
with the patient awake
There is an association with glucose
tumor involving Hypothalamus
Metabolic Syndrome and
“ Morbidly obese
and may therefore
appear to be
in the presence of
Monitoring (arterial line may be
needed if NIBP is problematic)
Surgical and Mechanical
Reduced surgical access
Difficult visualisation of underlying
Longer operating times
Higher risk of infection
Wound infection and wound
Osteoarthritis of weight bearing
Breast and endometrial malignancies
Suspect OSA ( h/o- Snoring).
Examination of calf muscles for tenderness
Examining signs of cardiac failure and
diabetes.(Waist-to-hip ratio >1 in women & >0.8 in
men increases the risk for IHD, Stroke, Diabetes &
Prior anesthetic records should be obtained.
◦ History of previous surgeries
◦ Anesthetic challenges (i.e. ease or difficulty in securing
the airway, intravenous access)
◦ Need for ICU admission, Surgical outcomes
◦ Weight of the patient at that time.
be paid to Circulatory,
Pulmonary, and Hepatic
Signs and symptoms of left or right
Classic physical signs of cardiac failure (e.g.
sacral edema) may be difficult to identify.
History of Hypertension and Diabetes
Blood pressures must be taken with the
appropriate size cuff.
Intravenous and intraarterial access sites
should be checked in anticipation of technical
History of hypoventilation and somnolence
Pulmonary function tests with spirometry
arterial blood gases
Patients with a history of heavy snoring
should have a formal sleep study or
Severity of obstructive sleep apnea and
hypopnea syndrome (OSAHS), apneahypopnea index (AHI)
Home Oxygen therapy with continuous
positive airway pressure (CPAP) ,response
and compliance should be noted.
Hepatic function tests
Serum albumin and globulin
Serum aspartate aminotransferase
Serum alanine aminotransferase
Direct and total bilirubin
Prothrombin time, and
ECG is mandatory
Baseline ABG(will help evaluate carbon dioxide retention
and provide guidelines for perioperative oxygen
administration and possible institution of and weaning from
Screening for diabetes
PFT (if needed)
Polysomnogram (if history of heavy snoring)
Airway management: Awake fibreoptic intubation
Choice of anesthetic technique and anesthetic
Consider asking for Assistance.
A typical operating table will support 150 kg, but the
tilting/tipping may not function.
The sphygmomanometer cuff width should be 20%
greater than the diameter of the arm
Invasive blood pressure monitoring may be required
Heparin, 5000 IU subcutaneously,
administered before surgery and
repeated every 12 h until the
patient will be fully mobile, or low
molecular weight heparins (LMWH)
injected subcutaneously 40 mg
every 12 h resulted in a decreased
incidence of postoperative DVT
Stockings, Early mobilization.
NPO status, and a large bore
intravenous access inserted.
An experienced Assistant
The full complement of alternate
airway, noninvasive and invasive (e.g.
cricothyriodotomy set and surgical
tracheotomy set) airway devices
should be available.
◦ Cuffs with bladders that encircle ideally of 75% or
minimum of 50% of the upper arm circumference should
Central Venous pressure monitoring
Hourly urine output is evaluated to assess fluid
Avoid CNS and respiratory depressants.(sedatives or
Antibiotic prophylaxis; increased risk of postoperative
Anticholinergics(Glyco) if awake intubation is planned.
proton pump inhibitors).
Continue antihypertensive medications.
If required O2 supplementation and monitoring.
Premedication should not be given IM as it may be
inadvertently administered into adipose tissue leading
to unpredictable absorption.
Strapping to the operating table in combination with a
malleable bean bag
Padding of pressure areas
Special tables for extra load (two tables)
The head up reverse trendelenburg position provides
the longest safe apnea period during induction
Lateral tilt to avoid compression of vena cava
“Stacking” using towels or folded blankets under
the shoulders and the head to compensate for the
exaggerated flexed position of posterior cervical
The object is to position the patient so that the tip
of the chin is at the higher level than the chest to
facilitate laryngoscopy and intubation.
Anticipate for difficult airway and prepare in
Awake intubation in morbid obese patient
LA DL Glottis visualized GA intubate
Not visualized Awake intubation
We should be ready for emergency tracheostomy
Drug handling in obesity
Unpredictable Volumes of
Elimination of drugs
Reduction in total body water
Higher fat mass
Higher lean mass
Increased renal clearance
PHARMACOKINETICS OF DRUGS
Drugs are dosed in the morbidly obese on the basis of
distribution so drug doses are calculated on the basis of
the patients Total Body Weight (TBW). Examples are:
Weakly lipophilic or lipophobic drugs have unchanged volume of
distribution so drug doses are calculated on the basis of the
patients lean body weight (LBW). Examples are:
Certain Lipophilic drugs are adminstered according to LBW are
Digoxin,Procainamide,Remifentanyl((Vd) remain same).
Calculating initial doses based on LBW with subsequent doses
determined by pharmacologic response to the initial dose is a
Insoluble anesthetic gases resistant to
metabolic degradation and without lipid
depot compartmentalization, combined
with rapid return of reflexes are
For intubation muscle relaxants with
rapid sequence induction should be
used. Succinylcholine and Rocuronium
are the available choices.
For maintenance of anesthesiaDesflurane/sevoflurane+ Cisatracurium
+intravenous infusion of Remifentanyl is
prefered.N2O should be avoided
particularly in Pt with Pulm HTN.
Desflurane and Remifentanil
infusion are used for maintenance
anesthetic because of rapid onset,
consistent profile, and rapid offset
Intact neurologic status, fully awake and
alert, with head lift greater than 5
Normothermia. The core temperature
Train-of-four (TOF) reversal documented
by peripheral nerve stimulator (T4/T1
Full reversal of neuromuscular blocking
Respiratory rate (>10 and < 30
Baseline Peripheral Oxygenation, as judged by pulse
Oximeter (SPO2 >95% on FIO2 of 0.4).
If an arterial line is present, an arterial blood gas
may be checked.
Acceptable blood-gas results (FIO2 of 0.4: pH, 7.35
to 7.45; PaO2, >80 mm Hg; PaCO2, < 50 mm Hg).
Acceptable Respiratory Mechanics: negative
inspiratory force (NIF) (>25 to 30 cm H2O; vital
capacity (VC) >10 mL/kg IBW; tidal volume (VT) >5
mL/kg ideal body weight [IBW]).
Acceptable Pain Control
No demonstrated or suspected Laboratory
Extubate awake, sitting up.
ICU care, may need CPAP.
Oxygen and oximetry.
Obstructive sleep apnoea is most
common some days after surgery.
Adequate analgesia to allow deep
There is no clear data proving the superiorty of
one technique over other for post op
analgesia.It depends on type ,site , duration,
severity of surgery.
Multi Modal Perioperative Analgesia(MMPA) I,e
preemptive infiltration local anesthetic at the
incision site +NSAIDS+ PCEA(patient controlled
epidural analgesia)/PCIA(patient controlled
intrathecal analgesia) is a new and advanced
method to deal with post op pain.
In certain situation where sedation is to be
m sulphate are better alternative of Opoids.
Early ventilatory failure with need for
Positional ventilatory collapse
Postoperative nausea and vomiting
May be impossible
techniques due to;
◦ Obscured landmarks
◦ Difficult positioning
◦ Extensive layers of
veins and extra fat
potential space, less
local anaesthetic 7580% of the normal
dose is needed for
Leave extra catheter
in the space as it may
be subject to drag as
the flexed patient