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Morbid obesityanaesthetic challenges.
Dr. S. Parthasarathy
MD., DA., DNB, MD (Acu), Dip. Diab.
DCA, Dip. Software statistics
PhD (physio)
Mahatma Gandhi Medical college
and research institute , puducherry
India
1920 dandi march
2010 dandi march
Body mass index
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Weight (Kg) / height (m)2
Weight = 75
Height =1. 5 metres
75/1.52
= 33.3
BMI
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■ BMI of 18–25 = normal
■ BMI of 25.0–30 = overweight
■ BMI of 30.0–35 = class I obesity
■ BMI of 35.0–40 = class II obesity
■ BMI of 40 or greater = class III
obesity.
20% of adults are obese and 1%
morbidly obese
Large and obese ??
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It is important to recognise the
difference between large patients and
those who are obese.
Some considerations such as medical
equipment and manual handling will
be very similar
BUT ??
Large man
Morbid obesity and co
morbidities
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Respiratory system
Restrictive lung disease
Obstructive sleep apnea
Obesity hypoventilation syndrome
greater absolute oxygen consumption
and carbon dioxide production
OSAS
five or more episodes of apnea lasting
10 seconds or more, associated with
4% decrease in oxygen saturation
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Dilators
Hyoid muscles, genioglossus, tensor
palati
Tensor palati,genioglossus,hyoid
muscles
FRC and CV ??
ERV **
Expiratory reserve volume is the
most sensitive indicator of the effect
of obesity on pulmonary function
testing.
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Hypertension – lean or obese ??
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Lean - normal pre & after load
Lean HT = ↑ after load
Obese non ht = ↑ pre load
Obese HT = ↑ after load & ↑ pre load
Cardiovascular system
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Systemic and/or
Pulmonary hypertension
Ischemic heart disease, arrythmias
DVT & Pulmonary embolus
Congestive heart failure
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Fat cardiomyopathy
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There is a 3–4 mm Hg increase in
systolic arterial pressure and a 2 mm
Hg increase in diastolic arterial
pressure for every 10 kg of weight
gained.
LVF + RVF = CCF
Other systems
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Central nervous system Cerebrovascular
accidents
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Endocrine system - Diabetes mellitus
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Gastrointestinal system - Hiatus hernia
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Musculocutaneous system Osteoarthritis
Malignancies
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Breast
Prostate
Uterus
Colon and rectum
comorbidity increases with the duration
of obesity (‘fat years’).
Sedentary life style , smoking ??
Preop considerations
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psychological and personal needs as
well as the need for appropriate
counselling and information
multi-disciplinary clinic
Cardiology,
Pulmonology
Neurology
DVT prophylaxis
Preop considerations
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a supine SpO2 > 96% - ok
Diabetes, hypertension renal, hepatic
disease and autonomic neuropathy –
evaluated
Possible diet advice and preop weight
loss
Difficult IV access
USG guided lines ??
Drugs taken
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orlistat also interferes with the
absorption of fat-soluble vitamins,
patients taking this drug need to be
supplemented with the fat-soluble
vitamins A, D, E, and K.
Amphetamine analogues
PREOP
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Talk to patient
Routine inv.
Electrolytes
ECG, CxR, ECHO, PFT,
Diabetes, H T, drugs
LMWH
Equipment
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Special equipment may be required, as
standard equipment (beds, operating
tables, ambulance and transfer
trolleys) is often rated to a maximum
safe weight well below that of the
morbidly obese patient
115 kg tables – routine
Premed
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some form of aspiration prophylaxis
antibiotic prophylaxis
Oral benzodiazipines – acceptable
Pre oxygenation is achieved employing
an anaesthesia facemask with an
airtight seal
End tidal O2 of 90 % end point
Monitors
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Large blood pressure cuffs are useful
for many patients
Otherwise
Think of tying in forearm
Forced-air warming blankets
NMJ monitoring
Pulse, NIBP, (IBP), SPO2, ETCO2,
Induction & position
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rapid sequence induction, utilizing
cricoid pressure
But if other predictors of difficult
intubation – FOL awake
Brachial plexus and sciatic and ulnar
nerve palsies have been reported in
patients with increased BMI.
TBW, IBW, LBM
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Ideal body weight = Height - 100
lean body mass (or the ideal body
weight plus 20%)
Lean body mass = James formula =
Lean Body Weight (men) = (1.10 x
Weight(kg)) - 128 x ( Weight2/(100 x
Height(m))2)
Keep it simple
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100 kg for men
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80 kg for women
Drug dosage
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Thio – 140 * 5 mg = 700 mg??
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benzodiazepines
and
barbiturates
are
highly fat soluble , ideal body weight
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less fat-soluble drugs NDPs – Lean Body
Mass
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succinylcholine, which should be dosed to
total body weight
Drug dosage
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Propofol is highly lipid-soluble, but also has a
very high clearance.
Its volume of distribution at steady state and
clearance are proportional to total body
weight.
Using total i.v. anaesthesia, the infusion rate
should be calculated on total body weight,
not ideal body weight
Dexmedetomidine Ideal
Local anaesthetics
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Maximum dose -- ideal body weight
i.e. 3 mg/kg
reduced by 25% for subarachnoid and
epidural blocks as engorged epidural
veins and fat impinge on the volume
of the epidural space.
Position for intubation
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‘sniffing the morning air’ position may
be difficult to achieve due to the large
soft tissue mass of the neck and chest
wall, and a wedge or blanket beneath
the shoulders is of benefit (‘ramped’
technique).
Difficult intubation trolley ready
Neck circumference
Neck circumference has been
identified as the single biggest predictor
of problematic intubation in morbidly
obese
Difficult intubation is approximately 5%
with a 40-cm neck circumference
compared with a 35% probability with
a 60-cm neck circumference
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Ramp position
Idea of ramp position
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bring the patient’s chin to a higher
point than the chest.
So ….
the mouth opening is better
cricoid pressure takes up no space
Laryngoscope placed in the mouthdoes not contact chest
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Short acting drugs
Fentanyl, vecuronium,
atracurium,desflurane ok
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Tidal volume ??
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500 ml for short , 700 ml for tall with
PEEP
Inh. Agents
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The MO patients metabolise halothane
and enflurane to a greater extent than
non obese leading to higher fluoride
levels.
High serum bromide levels and
halothane hepatitis are more common
in obese patients
Regional anaesthesia
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Safety - as airway is safe
USG guided blocks
Spinal, epidural
Locating the space and technical
difficulty
Needle length
EPIDURAL
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Attractive for lung and other organs
Abdominal muscles play a role in
forced expiration
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Epidural in muscle strength ??
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Recovery
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extubated wide-awake in the sitting
position
NSAIDs, paracetamol
I.M. injections should be avoided
because of unpredictable absorption
Use a spinal needle !!
Oxygen , CPAP
we need a long spinal
needle for IM injection!!
Postoperative considerations
hypoxia, respiratory obstruction
positioning, humidification
No shivering
 fluid intake - output,
 chest physiotherapy and incentive
spirometry,
 DVT, analgesia , wound infection,
 early ambulation.
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Post op period
complaints of buttock, hip, or
shoulder pain in the postoperative
period should raise the suspicion of
Rhabdomyolysis
Infiltration analgesia is the best.
IV paracetamol
For bariatric surgery
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Obese patients undergoing bariatric
surgery
would
benefit
from
an
approach similar to that for non–
weight loss surgery
125 Kg male 42 years for
FESS
Ht = 175 Wt = 125
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BMI = 40.8
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Ideal body wt. = 175- 100 = 75
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Lean body mass = 75 + 20% of 75 =
 90
kg
RAMP position
Difficult airway trolley
Premed = Inj. Pantocid
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Fentanyl = 75 Mic.
Glyco
= 0.2
Preoxy = 5 min.
Thio = 300 mg approx ( 90 * 3.5)
Suxa = 125 * 1.5 = 190 mg
Atracurium = 75 * 0.4 = 30 mg
followed by NMJ monitoring
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N2O : O2 = 3 : 2
Sevoflurane = 1 to 1.5 %
Head up extubation
Post op oxygen
NSAIDs
3 chip camera – 18 lakhs
Stryker HDTV monitor
Postoperative shift
O2
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Ooosch appa
Case over
Ooosch appa !!
Lecture is also over – thank you