Obesity presents unique challenges for anaesthesia. Obese patients have decreased lung volumes which increases the risk of hypoxemia during induction and intubation. Preoxygenation in a slightly head-up position can help reduce this risk. Intubation may be difficult due to obesity related anatomical changes. Regional anaesthesia can also be challenging due to obscured landmarks and extensive adipose tissue. Postoperatively, obese patients are at higher risk of respiratory failure, DVT, and wound infections requiring close monitoring. Careful consideration of dosing, positioning, and postoperative monitoring is needed to safely manage anaesthesia for obese patients.
2. OBESITY
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
life expectancy.
3. 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
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.
4. CLASSIFICATION OF OBESITY
BMI
STATUS
< 18.5
underweight
18.5–24.9
normal weight
25.0–29.9
overweight
30.0–34.9
class I obesity(Obese)
35.0–39.9
≥ 40.0
class II obesity (Morbidly obese)
class III obesity(Super morbidly
obese)
5. OBESITY & HEALTH RISKS
HEALTH RISKS
DEGREE OF OBESITY
ABDOMENAL FAT DISTRIBUTION
MALE WAIST ≥ 102cm
FEMALE WAIST ≥ 88cm
9. PULMONARY
MANIFESTATIONS
DEC. CHEST WALL
COMPLIANCE
RESTRICTIVE
LUNG DISEASE
DEC. FRC
ALVEOLAR
ATELECTASIS
• Lung compliance may normal
• Abdominal fat--cephalad shift of diaphragm
• Supine & Trendelenburg
• anaesthesia
• If FRC < CC
• V/Q mismatch; R-L shunt; arterial hypoxemia and
hypercarbia.
10.
11.
12. INC. ALVEOLAR
VENTILATION
• Inc. metabolic rate– inc. Body wt.
• Inc. O 2 demand
• Inc. CO 2 production
HYPOXIA &
HYPERCARBIA
• Alert to impending complications
OBESITY
HYPOVENTILATION
SYND.
• Pickwickian synd.
• Hypoxia & hypercapnia
• Polycythemia– cyanosis
• Rt. Sided heart failure
• somnolence
13. OBSTRSUCTIVE SLEEP APNEA
SYNDROME
• 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
clinically significant
• Day time somnolence associated with memory problem ,
impaired conc. and accident
14. • Throat muscles
become so relaxed
and floppy during
sleep that they
cause a narrowing
or complete
blockage of the
airway
15. Daytime sleepiness or fatigue
Dry mouth or sore throat upon awakening
Headaches in the morning
Trouble concentrating, forgetfulness,
depression, or irritability
Night sweats
16. Restlessness during sleep
Sexual dysfunction
Snoring
Sudden awakenings with a sensation
of gasping or choking
Difficulty getting up in the mornings
23. THROMBO-EMBOLIC DISEASE:
• Inc risk of DVT
•
•
•
•
Inc. intra-abdominal pressure
Polycythemia
Inc. pressure in deep veins
Immobilization-venous stasis
24. METABOLIC DYSFUNCTIONS
TYPE-2 DM
• Inc resistance to insulin in periphery
HYPERTENTION
CORONARY ARTERY DISEASE
CHOLILITHIASIS
• Abnormal cholesterol metabolism
HYPERCHOLESTEROLEMIA
HYPERINSULINEMIA
• Inc. sympathetic activation
25. Body Water
• Reduction in total body water to 40% of TBW.
• Relative dehydration may be present.
• Poor tolerance to fluid load.
27. Clinical Criteria for Diagnosing
Metabolic Syndrome *
Criteria
Defining Value
Abdominal obesity
Waist circumference >102 cm in men and
>88 cm in women
Triglycerides
≥150 mg/dL
High-density lipoprotein cholesterol
<40 mg/dL in men and <50 mg/dL in
women
Blood pressure
≥130/85 mm Hg
≥110 mg/dL
Fasting glucose
*Three of five criteria must be met.
28. OBESITY & DRUGS DOSES
LIPID SOLUBLE
1. Inc. vol of distribution
2. Larger loading doses to
produce same plasma
concentration but
maintenance doses less
frequent-slow clearance
3. Doses based on actual
body wt.
WATER SOLUBLE
1. Limited vol of
distribution
2. Doses not influenced by
fat stores
3. Doses based on ideal
body wt. – to avoid
overdosing.
29. •
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.
30. Halogenated anaesthetics:
• 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
fluoride conc.
• Liver and body fat store inhalational anaesthatics long after completion of
surgery bt drug conc. In brain and lungs decrease rapidly.
31. Pharmakinetics
• 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
152.4 cm
WoMen = 45.4 Kg + 0.89 kg/cm above
152.4 cm
39. PREOXYGENATION
SLIGHTLY HEAD UP POSITION
NECESSARY BECAUSE
• Dec FRC
• FRC Dec more on lying
• Supine
• After induction
• Obese rapidly desaturate
• Intubation may be difficult
41. POSITION IN INDUCTION &
INTUBATION
PRE-OXYGENAT & INTUBATE IN
SLIGHTLY HEAD UP POSITION
FOLDED BLANKETS PLACED UNDER
UPPER BODY,NECK & HEAD
• Sternal notch & external auditory meatus
are in line
42.
43.
44. INDUCTION &
INTUBATION
DIFFICULT TO VENTILATE WITH MASK
RAPID SEQUENCE INTUBATION
• Risk for aspiration
VAREITY OF SCOPES
• Long blade & short handle
AWAKE INTUBATION-IF DIFFICULT
• FOB
45. PEEP DURING
INDUCTION
Application of positive endexpiratory pressure during the
induction of general anesthesia:
• prevents atelectasis formation.
• improves oxygenation and probably
increases the margin of safety before
intubation.