Anaesthetic considering in morbid obesity

1. Anesthetic
Challenges in
Morbid Obesity
DR MAMTA HARJAI

2. 52 yrs female
Weight- 136 kg
BMI-52

3. Global Epidemic
 > 650 million obese adults worldwide. India ranking third.
Second only cause to smoking as a preventive cause of
death
Multisystem disease affecting all organs

5. Classification (WHO)

6. Waist circumference >102 cm male
>88 cm women,
Or
Waist /hip ratio >1 in men, 0.8> women
strong predictor of stroke, DM, IHD, death.
Independent of total body fat.
Waist to height ratio >.55 metabolic syndrome

7. BMI> 40 belongs to ASA Class ??

8. Fat distribution

9. Which is Detrimental?
Apple/central/android
abdominal/visceral
Common in men
Central fat is more predictive
for NIDDM, dyslipidaemia .
Significant co relation with
metabolic syndrome
•Pear/gynecoid
•Excess fat on thigh/buttocks
•Females
•Non significant co relation
with metabolic syndrome

10. Pathophysiology
Positive caloric balance stored as fat in adipocytes as TG
Adipocytes increased in size.(up to BMI< 40)
 Absolute increase in total no of fat cells
Neurohormonal disturbance leads to inflammation
(adipokines and cytokines )
Central adipose tissue is more frequently associated with
inflammation

11. Respiratory system
• Lung compliance may be normal
Decreased chest
wall compliance
• Abdominal fat- cephalad shift of
diaphragm
Restrictive lung
disease
Alveolar atlelectasis If FRC<< CC V/Q
Mismatch; R-L Shunt, Arterial Hypoxemia,
Hypercarbia
Decreased FRC Supine ,Trendelenberg, Anaesthesia

12. Obesity and alveolar collapse

13. Inc. Work of Breathing
Inc. metabolic rate– inc. Body wt.
Inc. O 2 demand
Inc. CO 2 production
Hypoxia & Hypercarbia
TV- may be normal, but reduced in MO
ERV, FRC, TLC- dec
RV- unchanged

14. Airway
Fat face and cheeks
Large breasts in females
Large tongue, Excess palatal and pharyngeal tissue (MMG-
3,4)
Redundant oro-pharyngeal tissue
Atlantoaxial joint limitation d/t cervical and thoracic fat
pads, and presternal fat deposits
Inc neck circumference
Short neck

15. Obstructive Sleep Apnea
Adipose deposits in lateral pharyngeal wall- mobile –
protrude into airway
 Throat muscles become so relaxed and floppy during sleep
- cause a narrowing/ complete blockage of the airway.
 Frequent episodes of apnea or hypopnea during sleep
Total cessation of airflow for 10 sec. Hypopnea - 50%
reduction in airflow

16. Symptoms
Day time sleepiness/fatigue
Dry mouth upon awakening
Headache in morning
Trouble concentrating/forgetfullness
Night sweats
Sudden awakening with choking sensation

17. Perioperative complications of
OSA
-MI
• Arrthymias
• Hypertension
• Ischemic stroke
• Insulin resistance
Hypoxia
Upper airway
obstruction
Difficult intubation

18. Stop Bang Questionnaire

19. Gold standard to make diagnosis??
Apnea/Hypopnea Index (AHI)- Total number of
episodes of apnea and hypopnea per hr of total
sleep time.
Mild: >5 events/hr Moderate: >15 events/hr
Severe : > 30 events/hr
Usually managed with CPAP at home

20. Obesity Hypoventilation Syndrome
Pickwickian synd.
Sleep disordered breathing
Obesity (BMI ≥30 kg/m−2
)
Daytime hypercapnia PCO2 ≥45 mmHg during wakefulness
90% OHS- OSA( AHI>5)
Hypoxia & hypercapnia
Polycythemia– cyanosis
 Rt. Sided heart failure

21. Cardiovascular system
oInc circulating BV
oInc CO (0.1/min for each kg of excess adipose tissue)
oInc O2 consumption
oAtherosclerosis ( coronary ,cerebral vessels)
oHypertension
oProne to arrhythmias (hypoxemia,hypercarbia, MI)

22. Cardiovascular system

23. Gastro Intestinal System
Increased abdominal pressure -Hiatal
hernias, GERD
Larger gastric volume even after NPO
Increased risk for aspiration of gastric
contents

24. Thromboembolic disease
Increased risk of DVT, PE
Inc abdominal
pressure-
venous stasis
Immbolisation-
venous stasis
Polycythemia Dec fibrinolysis

25. Endocrine/hepatic
NIDDM (Insulin resistance/ inadequate insulin production)
Hypercholesterolaemia,
Hypothyroidism
Osteoarthritis
Fatty liver/ Inc Hepatic enzymes
Gallstones

27. Metabolic Syndrome

28. Drug metabolism
Drug doses often warrant adjustment in obese
patients.
Volume of distribution -determines the loading dose
Clearance - determines the maintenance dose.

29. Drug Dosing

30. LBW = TBW - mass of fat
LBW = IBW + 20 to 40% excess body weight
ABW = IBW + 0.4 (TBW kg)
IBW (kg) = height (cm) - 100 ( adult males)
IBW (kg) = height (cm) -105 ( adult females )

31. Drug dosing according to IBW —-.> UNDERDOSING
Drug dosing according to TBW—---> OVERDOSING
Drug dosing according to LBM—----> ADEQUATE
Increased sensitivity to respiratory depressant effects of BZD and other
sedatives
Due to comorbidity, functions of organs of elimination can be affected
making pharmacokinetics more difficult and complex

33. Inhalational agents
Soluble inhalational agents accumulate in adipose
tissue and take longer to clear, resulting in more
prolonged emergence as compared with less-soluble
agents
The risk of halothane hepatitis may be higher in
obese patients, although overall is still very low.
 Desflurane (inhalation of choice) display rapid
onset and offset.

34. Regional Anesthesia
Technically harder
Loss of landmarks
Difficult positioning
Extensive layers of adipose tissue
Need for long needles.
Less local anaesthetic is needed for
epidurals.
Engorged extradural veins
Extra fat constricting the potential
space
(75-80% of the normal dose)

35. Positioning challenges
• Ventilatory impairment
• Compression of ivc/aorta
• Pressure sores
supine
• Cushioning pads excessive
pressure
• Skin breakdown,tissue necrosis
Prone
• Regular stirrups may not bear weight
• Nerve injuries/compartement
syndrome
Lithotomy

36. Perioperative Challenges
Difficult mask ventilation and tracheal intubation
Rapid desaturation during induction and intubation
Difficult surgical access
Aspiration of gastric contents
Exacerbation of cardiopulmonary comorbidities
Altered drug metabolism
Risk of DVT

37. Difficult Vascular Access (Vein locator/ultrasound)
Difficult transport
OT table too small
Difficult patient positioning
Inapproprite monitoring
 Difficult RA

38. Anesthetic considerations
Preoperative
Intraoperative
Postoperative

39. Preoperative
History
 Duration of obesity & associated problems
 Previous operation & anaesthesia,
 Medication
OSA, Use of CPAP
 Ask Patient can tolerate supine position
 Assess cardiopulmonary reserve -difficult to assess METS
Hx, Physical examination-(BP, Edema) X-Ray chest ECG ABGs
ECHO

40. Focused Airway assesment
History of OSA: decrease in oropharyngeal space makes mask ventilation
and laryngoscopy difficult.
BMI >40
Neck circumference: >40cm is associated with 5% problematic intubation,
>60cm is associated with 35%
NC/TM ratio: >=5 predicts difficult intubation.
Anterior neck soft tissue> 28 mm
Limited mandibular protrusion
Short neck
CPAP>10 ( BMV)

41. Risk for aspiration pneumonia
Premedication:
Aspiration prophylaxis
Avoid sedation & respiratory depressant
-Pre-ops hypoxia & hypercapnia • OSA
Continue antihypertensive medication
LMWH subcutaneous(DVT prophylaxis)
IM- Injections…Unreliable

42. Intraoperative
Head elevated laryngoscopy position( HELP ):
stacked or ramped position so that external auditory canal is in
horizontal line with the sternum as well as reverse trendelenburg
position

43. HELP

44. Preoxygenation
Preoxygenate in 20 degrees head up position (increase
FRC, Safe apnea time)
Add 10 cm H2O of PEEP/ 5 - 10 cm H2O CPAP
Apneic oxygenation
- nasal cannula with high flow of O2 at 10 - 15 lit/min
after induction

45. Variety of scopes
-Long Blade & Short Handle
-VL
-OPA,NPA
-SADs/ FONA
Difficult BMV- Awake Intubation-• FOB
Rapid sequence intubation
Plan for failure

46. Pad pressure points
Apply pneumatic leggings or compression
stockings

47. Postoperative challenges
Delayed extubation
Obstruction and /or desaturation after extubation
Need for tracheal reintubation
Exacerbation of cardiopulmonary comorbidities
Inadequate pain mangement
Prolonged hospital stay
Delayed discharge

48. Extubation Strategies
The patient should be placed in the ramped or 25° reverse
Trendelenburg position for extubation.
 Fully awake with adequate reversal of neuromuscular
blockade.
 May require possible reintubation during extubation of
difficult airway cases.
 Airway exchange catheter-assisted extubation can
provide continuous airway access

49. Supplemental oxygenation in semi recumbent
position
Use of CPAP (reduce the risk of pulmonary
complications, atelectasis)
Opioid free Analgesia/NSAIDS
Epidural LA plus opioids
Pulmonary care( deep breathing/incentive
spirometry)

51. LIPID SOLUBLE
Inc VD
Larger loading doses to produce
same plasma concentration but
maintenance doses- less frequent-
slow clearance
WATER SOLUBLE
Limited VD
Doses not influenced by fat stores
Doses based in IBW- to avoid
overdosing