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.

1. OBESITY & ANAESTHESIA
Co-ordinator – Dr. Chavi Sethi(MD)
Speaker – Dr. Uday Pratap Singh

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

6. CLINICAL MANIFESTATION
1.Pulmonary
2.C.V.S
3.G.I.T
4.Hepatic
5.Metabolic

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.

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

17. Hypertention
Hypoxia
Myocardial
infarction
Arrhythmias
Pulmonary edema
Stroke
Difficult intubation-induction
Upper airway
obstruction-recovery

18. GASTROINTESTINAL
MANIFESTATIONS
HITUS HERNIA
GASTROESOPHAGEAL REFLUX
POOR GASTRIC EMPTYING
HYPERACIDIC GASTRIC FLUID
INC. RISK OF GASTRIC CANCER

19. HEPATOBILIARY
MANIFESTATIONS
HEPATIC
• Fatty infiltration of liver
• Abnormal liver function
• Volatile anaesthetics defluorinated to
greater extent-halothane hepatitis
GALL STONES
• Abnormal cholesterol metabolism

20. CARDIOVASCULAR
MANIFETATIONS
INC. BLOOD VOL
• To perfuse Additional body fat
INC. STROKE VOL
INC. CARDIAC OUT PUT
• 0.1 ml / min / kG body fat
ARTERIAL HTN
INC. CARDIAC WORKLOAD

21. LT VENTRICULAR HYPERTROPHY
PULMONARY HTN & COR
PULMONALE
• INC. Pulmonary blood flow
• Pulmonary vasoconstriction
• Persistent hypoxia

22. Cardiac manifestations of obesity
LVH
RVH

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.

26. METABOLIC SYNDROME
OBESITY
METABOLIC
SYND
TYPE-2
DM
HTN

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

32. ANAESTHETIC
CONSIDERATIONS
PREOPERATIVE
INTRAOPERATIVE
POSTOPERATIVE

33. PREOPERATIVE
HISTORY
• Duration of obesity & associated
problems
• Previous operation & anaesthesia
• Medication

34. INVESTIGATIONS
• Blood
• Urine
• LFTs
• RFTs
• ECG
• X-Ray chest
• Echocardiography
• ABGs

35. RISK FOR ASPIRATION PNEUMONIA
• Premedication:
• Anticholinergic agent
• H2-antagonist
• Metoclopramide
• Sodium citrate(oral antacid 30 ml of 0.3M)
• LMWH subcutaneous(DVT prophylaxis)
AVOID RESPIRATORY DEPRESSANT
• Pre-ops hypoxia & hypercapnia
• OSA
IM- Injections…Unreliable

36. ASSESS CARDIOPULMONARY
RESERVE
•
•
•
•
•
History
Physical examination-(BP,Edema)
X-Ray chest
ECG
ABGs
IV & IA ACCESS
• Technical difficulties

37. REGIONAL ANAESTHESIA-DIFFICULTIES
• Obscured landmarks
• Difficult positioning
• Extensive layers of adipose tissue
AIRWAY ASSESSMENT IN OBESE
•
•
•
•
•
•
•
•
•
Difficulty in mask ventilation
Difficult intubation--Consider FOB
Temporomandibular joint-limited mobility
Atlanto-ooccipital—limited mobility
Narrow upper airway
Distance b/w mandible & sternal fat pads-limited
Large breasts
Excessive palatal & Pharyngeal soft tissue.
Short and thick neck(if circumference >14cm then difficult
intubation)

38. INTRAOPERATIVE
GA
• PRE-OXYGENATION
• POSITIONING
• INDUCTION & INTUBATION
• MAINTAINACE
REGIONAL ANAESTHESIA
• Technical difficulties
• Doses of LA
• Complications
• Advantages

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

40. OBESITY & V/Q
MISMATCH
• Chest obesity
• Inc intraabdominal
pressure
DEC. FRC
ATELACTASIS
FRC < CC
• Supine position
• Induction
• Muscle
relaxation
• Rt to Lt shunt
• Rapid hypoxia
V/Q
MISMATCH

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

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.

46. CONFIRMATION OF
INTUBATION
DIFFICULT TO CONFIRM
BY AUSCULTATIONCLINICALLY
CONFIRMED BY END
TIDAL CO2

47. MAINTAINACE OF
ANAESTHESIA
HIGH INSPIRED O2 CONCENTRATION
• LITHOTOMY,TRENDELENBURG & PRONE
CONTROLLED VENTILATION – HIGH TIDAL
VOLUMES
PEEP-WORSEN PULMONARY HTN IN
EXTREME OBESE

48. POSTOPERATIVE
COSIDERATIONS
EXTUBATION
• Delayed until effects of NMBAs completely
reversed
• Fully awake
• Adequate airway maintenance
• Adequate tidal volume
• Supplemental oxygenation
• Modified sitting position

49. POSTOPERATIVE COMPLICATIONS
RESPIRATORY FAILURE
• Major complication
• Inc risk• Pre-ops hypoxia
• Thoracic & upper abdominal Surgery
DEEP VENOUS THOROMBOSIS
PULMONARY EMBOLISM
WOUND INFECTION

50. THANK YOU

51. CPAP CIRCUIT

52. APPLICATION OF CPAP

53. DIFFICULT INTUBATION IN OBESE

54. ATELACTASIS IN OBESE

56. MONITORING
INVASSIVE
MONITORING—
HAEMODYNAMIC
INSTABILITY
• CVP
• INTRA-ARTERIL LINE
• PULMONARY ARTERY CATHETER