OBESITY & ANAESTHESIA
Co-ordinator – Dr. Chavi Sethi(MD)
Speaker – Dr. Uday Pratap Singh
LATIN WORD OBESUS, WHICH
MEANS FATTENED BY EATING
OBESITY: Metabolic disease in which adipose
tissue comprises a greater then normal
proportion of body tissue and amount of fat
tissue is increased beyond a point compatible
with physical and mental health and normal
Over wt.: excess of total body wt. including all components(muscle, bone, water and fat)
Ideal body wt. ( in Kg): also k/w as Broca,s index
Height in cm- 100 for males(105 for females)
Relative wt. : Ratio of actual and ideal wt.
Body mass index(BMI): also k/w as Quetelet index
Body wt.(in Kg)/ Height(met2)
Ponderal index = height in cm divided by cube root of body weight in kg
Corpulence index: Actual wt/ desire wt.
normaly less then 1.2
Harpedence index: normally less then 40 in female and less then 50 in male.
CLASSIFICATION OF OBESITY
class I obesity(Obese)
class II obesity (Morbidly obese)
class III obesity(Super morbidly
OBESITY & HEALTH RISKS
DEGREE OF OBESITY
ABDOMENAL FAT DISTRIBUTION
MALE WAIST ≥ 102cm
FEMALE WAIST ≥ 88cm
DEC. CHEST WALL
• Lung compliance may normal
• Abdominal fat--cephalad shift of diaphragm
• Supine & Trendelenburg
• If FRC < CC
• V/Q mismatch; R-L shunt; arterial hypoxemia and
• Inc. metabolic rate– inc. Body wt.
• Inc. O 2 demand
• Inc. CO 2 production
• Alert to impending complications
• Pickwickian synd.
• Hypoxia & hypercapnia
• Polycythemia– cyanosis
• Rt. Sided heart failure
OBSTRSUCTIVE SLEEP APNEA
• Frequent episodes of apnea or hypopnea during sleep
Total cessation of airflow for = 10 sec.
Hypoapnea is 50% reduction in airflow
5 or more episode per hr. or 30 per night are counted as
• Day time somnolence associated with memory problem ,
impaired conc. and accident
• Throat muscles
become so relaxed
and floppy during
sleep that they
cause a narrowing
blockage of the
Daytime sleepiness or fatigue
Dry mouth or sore throat upon awakening
Headaches in the morning
Trouble concentrating, forgetfulness,
depression, or irritability
Restlessness during sleep
Sudden awakenings with a sensation
of gasping or choking
Difficulty getting up in the mornings
Clinical Criteria for Diagnosing
Metabolic Syndrome *
Waist circumference >102 cm in men and
>88 cm in women
High-density lipoprotein cholesterol
<40 mg/dL in men and <50 mg/dL in
≥130/85 mm Hg
*Three of five criteria must be met.
OBESITY & DRUGS DOSES
1. Inc. vol of distribution
2. Larger loading doses to
produce same plasma
maintenance doses less
3. Doses based on actual
1. Limited vol of
2. Doses not influenced by
3. Doses based on ideal
body wt. – to avoid
Commonly used anesthetic drugs can be dosed according to total-body weight (TBW) or
IBW based on lipid solubility.
Lean body mass is a good weight approximation to use when dosing hydrophilic
medications. As expected, the volume of distribution is changed in obese patients with
regard to lipophilic drugs.
Three exceptions to this rule are digoxin, procainamide, and remifentanil, highly lipophilic,
have no relationship between properties of the drug and their volume of distribution.
Consequently, dosing of commonly used anesthetic drugs such as propofol, vecuronium,
rocuronium, and remifentanil is based on IBW.
In contrast, thiopental, midazolam, succinylcholine, atracurium, cisatracurium, fentanyl,
and sufentanil should be dosed on the basis of TBW.
maintenance doses of propofol should be based on TBW. Conversely, based on real body
weight, smaller amounts of propofol are needed to anesthetize the patient.
• Morbidly obese pt. Metabolize halothane and enflurane more resulting in high
serum and urine level or fluoride.
• Isoflurane and desflurane are volatile agent of choice bc it produces lower
• Liver and body fat store inhalational anaesthatics long after completion of
surgery bt drug conc. In brain and lungs decrease rapidly.
• Alternation in drug binding, distribution, and elimination of
many anesthetic drugs.
• Dose calculation based on IBW rather than TBW.
• IBW calculated as :
Men = 49.9 Kg + 0.89 kg/cm above
WoMen = 45.4 Kg + 0.89 kg/cm above
POSITION IN INDUCTION &
PRE-OXYGENAT & INTUBATE IN
SLIGHTLY HEAD UP POSITION
FOLDED BLANKETS PLACED UNDER
UPPER BODY,NECK & HEAD
• Sternal notch & external auditory meatus
are in line
DIFFICULT TO VENTILATE WITH MASK
RAPID SEQUENCE INTUBATION
• Risk for aspiration
VAREITY OF SCOPES
• Long blade & short handle
AWAKE INTUBATION-IF DIFFICULT
Application of positive endexpiratory pressure during the
induction of general anesthesia:
• prevents atelectasis formation.
• improves oxygenation and probably
increases the margin of safety before
DIFFICULT TO CONFIRM
CONFIRMED BY END
HIGH INSPIRED O2 CONCENTRATION
• LITHOTOMY,TRENDELENBURG & PRONE
CONTROLLED VENTILATION – HIGH TIDAL
PEEP-WORSEN PULMONARY HTN IN
• Delayed until effects of NMBAs completely
• Fully awake
• Adequate airway maintenance
• Adequate tidal volume
• Supplemental oxygenation
• Modified sitting position
• Major complication
• Inc risk• Pre-ops hypoxia
• Thoracic & upper abdominal Surgery
DEEP VENOUS THOROMBOSIS