The document discusses anesthesia considerations for bariatric surgery. It notes that obesity is associated with various comorbidities affecting the respiratory, cardiovascular, gastrointestinal and other body systems. The anesthesia plan involves a thorough preoperative evaluation of the patient's airway, cardiac function, respiratory status, risk of venous thromboembolism, and metabolic/nutritional abnormalities. Careful dosing of anesthetic drugs based on lean or total body weight is also required. The goal of anesthesia is to safely induce and maintain anesthesia for bariatric surgery while addressing the unique health risks faced by obese patients.

1. Anesthesia for Bariatric
Surgery
Guided by: Dr Vrishali Ankalwar
By: Dr Sneha Khobragade

2.  WHO defines obesity as condition with excess
body fat to the extent that health and well being
are adversely affected.
 The precursors to obesity include
1.Genetic tendency
2.Environmental effect.
3.Education
4.Gender, ethnicity
5.Socioeconomic

3.  Medical co-morbidities associated with obesity
1. Type II DM
2. Hypertension
3. Cardiovascular diseases
4. OSA
5. Liver & Gallbladder diseases
6. Arthritis
7. Colon and postmenopausal breast cancer
8. Affects quality of life issues

4.  Bariatric is the field of medicine that specializes
in treating obesity.
 it is a surgical subspecialty that perform
operations to treat morbid obesity.
 Medical conditions associated with extreme
obesity are reversible with sustained weight
lose.
 Mortality rate for Bariatric surgery is 0.5% - 1%!

5. TYPES: classified on the basis of –
• Waist circumference
• Waist to hip ratio
• Waist to height ratio
• Truncal distribution of fat
• Increase risk of
cardiovascular diseases
Central-android
Obesity
• Fat is prominent in hips,
buttocks and thigh
• Less incidence of
cardiovascular diseases
Peripheral-
gynecoid Obesity.

6. FACTORS CLASSIFYING OBESITY:
 Body Mass Index = weight/height ^2 (Kg/m^2)
( Quetelet’s index)
 Cannot distinguish between overweight and over fat.
BMI (Kg/m^2) Classification Risk of systemic
diseases
<18.5 Underweight Increased
18.5-24.9 Normal Least
25-29.9 Overweight Increased
30-34.9 Obesity (class I) High
35-39.9 Obesity (class II) Very high
>= 40 Morbid Obesity (class III) Very high
>=50 Super obesity Extremely high

7.  Broca’s index : IBW(Kg) = height (cm) – x
( x is 100 for adult male & 105 for
adult female)
 Lean body weight (LBW) = TBW – adipose tissue
(approximate 80% & 75% of TBW in males &
females respectively)

8.  WAIST CICUMFERENCE:
Waist
circumference
BMI(Kg/m2)
Normal
weight
overweight Obese
Class I
< 102 cm in males
< 88 cm in females
Least risk Increased
risk
High risk
> 102 cm in males
> 88 cm in females
Increased
risk
High risk Very high
risk

9. BARIATRIC SURGERY:
INDICATIONS :
1. BMI > 40 Kg/m2
2. BMI > 30 Kg/m2 and obesity related
co-morbidities not controlled by
medical therapy

10. TYPES :
1. malabsorptive procedures :
- jejunoileal bypass
- biliopancreatic diversion
2. restrictive procedures:
- Vertical band gastroplasty
- Adjustable gastric banding
3. combined procedures: Roux-en-Y
gastric bypass

11. ROUX-EN-Y GASTRIC BYPASS
 Most effective
 Safe short- and long - term weight loss
( BMI decreases by 10 kg/m2 in first 1-2 year)
 Type II diabetes resolves

12. ADVANTAGES LAPROSCOPIC BARIATRIC
SURGERY:
 less postoperative pain
 lower morbidity
 faster recovery
 less “third – spacing” of fluid

13. PATHOPHYSIOLOGY:
RESPIRATORY SYSTEM:
fat
accumulation
decrease
chest wall
movement
decrease
lung
compliance

14. Increase elastic resistance &
decrease pulmonary compliance
FRC, vital capacity, total
lung capacity.
-shallow and rapid breathing
-increases work of breathing
-limited maximum ventilatory
capacity

15. Arterial hypoxemia
Small
airway
closure
Unchanged
closing
capacity
FRC

16.  Low arterial oxygen tension as compared to non
obese
 Chronic hypoxemia :
>> polycythemia
>> pulmonary hypertension
>> cor pulmonale

17. Increase
sympathetic
activity
Insulin
resistance
dyslipidemia
hypertension
Enhances pressor
activity of
norepinephrine
and angiotensin
II
SODIUM
retention
obesity
induced
hypertension

18.  HTN for every 10 kg weight gain
systolic arterial pressure by 3-4 mm hg
diastolic pressure by 2 mm hg
 Accelerates atherosclerosis  restricted mobility
 Cardiac dysrhythmias  precipitated by fatty
infiltration of conduction system, hypoxia,
electrolyte imbalance, OSA, increase circulating
cathecolamines.

19. DIASTOLIC
DYSFUNCTION
SYSTOLIC
DYSFUNCTION
OBESITY
CARDIOMYOPATHY
OBESITY CARDIOMYOPATHY:

20. Increase in total
blood volume and
Cardiac Output
left ventricular wall
stress and
hypertrophy
impaired filling
(diastolic dysfunction)
with increase
LVED pressure
Left ventricular wall
thickening fails to
keep pace with
dilation
systolic dysfunction

21. BIVENTRICULAR FAILURE

22. HYPERCOAGUBALITY:
 releases bioactive mediators 
- abnormal lipids,
- insulin resistance,
- inflammation and
- coagulopathies.
 Increase fibrinogen, factor VII, factor VIII, &
hypofibrinolysis

23.  Additional factors includes:
- increase fasting triglycerides factor
VII, activated by postprandial lipemia
- insulin endothelial dysfunction  von
willebrand factor & factor VIII  predisposes
fibrin formation

24. GASTROINTESTINAL SYSTEM:
 Increase incidence of severe pneumonitis:
-Gastric volume in excess by 25 ml
- gastric pH <2.5
- delayed gastric emptying because of abdominal
mass antral distension, gastrin release, pH .
-increase in intragastric pressure, increases
frequency of esophageal sphincter relaxation 
reflux symptoms

25.  Liver abnormalities : -non alcoholic fatty liver
-nonalcoholic steatohepatitis
-focal infiltration
-cirrhosis
but clearance is not correlated.
 Cholelithiasis is common  abnormal cholesterol
metabolism
 Postoperatively high prevalence of hepatic
dysfunction and cholesterol metabolism

26. RENAL AND ENDOCRINE SYSTEMS:
 Diabetes risk increases by 25 % for every 1kg/m2
increase in BMI above 22kg/m2
 Impaired glucose tolerance – reflected by high
prevalence of type II DM resistance of peripheral
adipose tissue to insulin
 Increase risk of wound infection and myocardial
infarction

27.  subclinical hypothyroidism
 Increase renal blood flow
glomerular hyperfiltration
increases sympathetic & RAAS
increase in renal tubular reabsorption &
impairs natriuresis

28. METABOLIC SYNDROME / SYNDROME X :
AHA defines when 3 out of 5 is present-
1. central obesity: waist circumference >102 cm
(>40 in) in males and >88 cm (>35 in) in
females
2. dyslipidemia: triglycerides> 150 mg/dl
3. dyslipidemia :HDL < 40 mg/dl in males,
< 50 mg/dl in females

29. 4. Hypertension >130/85 mm Hg or on
antihypertensive
5. Elevated fasting glucose > 100 mg/dl or on
anti-diabetics
 also k/a insulin resistance syndrome

30. PREOPERATIVE EVALUATION:
1. Airways: Number of abnormalities may exist
a) Limitation of extension and flexion of the
Cervical spine.
b) Restricted mouth opening from sub-mental
fat.
d) Redundant intra-oral tissue.
e) Thyro-mental distance should be assessed.

31. f) Infantile type anterior laryngeal opening.
g) large breast in females.
h) neck circumference (>40 cm) – SINGLE POSITIVE
PREDICTOR OF DIFFICULT INTUBATION

32. 2. History of prior surgical procedure :
 Ease or difficulty in securing the airway,
intravenous access
 Need for intensive care unit
 Surgical outcomes
 Weight of the patient at that time
 help ease concern or better prepare for the
upcoming anesthetic care.

33. 3. Cardiovascular & respiratory systems :
a) Tolerance of exercise and ability to lie flat.
b) Evaluated for systemic HTN, pulmonary HTN,
signs of right and/or left heart failure, IHD
c) Symptoms of sleep apnea should be sought
d) Electrocardiogram
e) chest radiograph
f) Echocardiography
g) Arterial blood gas analysis

34. 4. History of use of diet tablets (some of them
interfere with anesthesia & cause complication during
surgery)
 Indications of use of diet tablets:
BMI >= 30kg/m2
BMI 27-29.9 kg/m2 associated with
obesity-related medical comorbidities
 lifestyle counseling still most effective
 lifestyle counseling + medication

35.  FDA approved anti-obesity medication:
PHENTARMINE
ORLISTAT

36. PHENTARMINE
sympathomimetic drug that decreases appetite
>> approved for three months use
>> S/E: tachycardia, palpitations, hypertension,
dependence, withdrawal symptoms
>> no longer combined with FENFLURAMINE
causes- pulmonary hypertension and
valvular heart disease

37. >> blocks absorption of dietary fat by inhibiting
lipases in GIT.
>> leads to weight loss, improvement in BP,
fasting glucose & lipid profile.

38. >> ADR-
1) fat malabsorption: oil spotting, liquid stools
fecal urgency, flatulence, abdominal
cramping.
2) chronic use: fat soluble vitamin deficiency
-prolong PT & normal PTT (Vitamin k def.)
(should be corrected 6-24 hrs before surg.)

39. 5.
 It is defined as episodic complete cessation of
airflow during breathing lasting 10 seconds or
longer despite maintenance of neuromuscular
ventilatory effort, occurring 5 or more times per
hour of sleep and accompanied by a decrease of
at least 4 % in arterial oxygen saturation.

40. OBSTRUCTIVE SLEEP HYPOPNEA
 It is defined as episodic partial reduction of
airflow of more than 50% lasting at least 10
seconds, occurring 15 or more times per hour of
sleep and accompanied by decrease of at least 4
% of arterial oxygen saturation.

41.  symptoms: snoring,
frequent arousal during sleep,
daytime sleepiness,
impaired concentration,
memory problems,
morning headaches.

42.  signs : witnessed episodes of apnea during sleep
BMI>=35
neck circumference >= 16 inch (40cm)
hyperinsulinemia
elevated glycosylated hemoglobin
 gold standard diagnostic test: overnight
polysomnography

43. POLYSOMNOGRAPHY (PSG) : diagnosis of sleep related
disorders.
- includes meaurement of
1. O2 saturation
2. Electrocardiography
3. Electroencephalography
4. Electromyography

44. 5. Electrooculography
6. Nasal and oral airflow measurement –
Thermocouple
7. Measurement of respiratory efforts

45.  Results are reported as –
APNEA /HYPOPNEA INDEX : total number of
apneas and hypopneas divided by the total sleep
time.
- mild disease- AHI of 5 – 15 events per hour
- moderate disease- AHI of 15 – 30 events per
hour
- severe disease- AHI of > 30 events per hour

46.  consider:
a) sleeping on one side
b) weight loss
c) avoidance of alcohol before bedtime
d) preoperative initiation of CPAP
e) high risk of presenting with difficult airway
f) postoperative pulmonary complications

47. 6. Obesity Hypoventilation Syndrome/ Pickwickian
syndrome (OHS):
 long-term OSA
 combination of obesity, hypersomnolence & chronic
hypoventilation  pulmonary hypertension and cor
Pulmonale.
 Diagnosis : presence of both obesity (BMI>30 kg/m2)
and awake arterial hypercapnia (paco2 >45mmhg) in
absence of known cause of hypoventilation.

48. 7. Metabolic issues:
 screen for long-term metabolic and nutritional
abnormalities
 consider glucose check
 electrolytes check
 liver function test (obese shows elevated alanine
aminotransferase)
 vitamin and nutritional deficiencies- postoperative
polyneuropathy (acute postgastric reduction surgery
neuropathy)

49. POSTOPERATIVE POLYNEUROPATHY
(ACUTE POSTGASTRIC REDUCTION
SURGERY NEUROPATHY - APGARS)
 Polynutritional multisystem disorder seen after
weight loss
 Vitamin B12 and thiamine deficiency
 Symptoms:- protracted postoperative vomiting
- hyporeflexia
- muscle weakness
- painful polyneuropathy

50. 8. Hematological issues:
 Increase risk of perioperative thrombo-embolic events
 Thromboembolism prophylaxis :
 Combination of intermittent pneumatic compression
devices with heparin (unfractionated/ LMWH)
prolonged postoperative thromboembolism
prophylaxis regimen (1-3 weeks)

51.  In our institution, preloaded syringe of LMWH
(enoxaparin; 0.6 mg subcutaneously)
administered once a day 2 days prior to surgery
and then twice a day till the patient is fully
mobile.

52.  Anticoagulation therapy may be precluded if
combination of
a)short duration of surgery
b)lower extremity pneumatic compression
c)routine early ambulation is used
- except in previous and family history of
DVT.

53. INTERMITTANT PNEUMATIC COMPRESSION DEVICE:
 Double walled, vinyl pneumatic sleeves, placed
around the calves and connected to a compressor
that inflate and deflate the sleeves.
 Compression – 12 sec/min
 inflation pressure – 40 mmHg

54.  leg Sleeves -12-16 inch long
 It extend distally from inferior border of patella
 Applied preoperatively, during surgery and
removed once the patients start walking.
 Stimulates fibrinolysis preventing thrombus
formation & promotes venous return

55.  Contraindications :
1. acute thrombophlebitis
2. congestive heart failure
3. pulmonary edema
4. severe PVD
5. suspected DVT

56.  preoperative prophylactic placement of IVC filter
considered if following risk factors for DVT are
present:
a) venous stasis disease
b) BMI>=60
c) central obesity
d) OHS and/or OSA

57. PHARMACOLOGICAL CONSIDERATIONS
 for drug dosing in obese, consider
volume of distribution for loading dose
clearance  for maintenance dose
 For loading dose, if Drug distribution
 lean tissues, dose LBW
 equal in adipose & lean tissues, dose  TBW

58.  For maintenance dose, if clearance
 equal in obese & non obese , dose LBW
 increases with obesity, dose TBW
Drug Recommended dosing
Thiopentone TBW
Propofol Induction: IBW; Maintenance: TBW
Fentanyl/Sufentanil TBW
Vecuronium/Rocuronium IBW
Atracurium/ cisatracurium IBW
succinylcholine TBW
Benzodiazepine IBW
neostigmine TBW
paracetamol IBW
glycopyrolate IBW

59. ANESTHETIC CONSIDERATIONS
PREMEDICATION
 Avoid heavy sedation.
 Continue medication for chronic HTN if present
 Antibiotics & DVT prophylaxis
 Aspiration prophylaxis
 Avoid IM injections due to unpredictable absorption

60. EQUIPMEMT & MONITORING:
 Specially designed table /two regular sized
operating table
 Strap the patient to the table with bean bags
prevent falling
 Proper padding during positioning to protect
pressure areas

63.  NIBP cuff encircling minimum 75% or entire
upper arm
 from the wrist or ankle.
 Invasive arterial pressure monitoring super obese
/ cuff does not fit
 Central venous access  inadequate peripheral
access
 ETCO2 monitoring – confirms adequate ventilation
 SPO2, ECG and Temperature monitoring

64. AIRWAY :
 Ramped positioning or elevating the upper body
and the head of the patient to align the ear and
the sternum horizontal, improves laryngoscopic
view.

65. PREOXYGENATION:
 Difficult bag and mask ventilation – overcome by
four handed technique
 Adequate preoxygenation with CPAP by using NIV
 Specially in case of OSA, OHS
INDUCTION:
 CPAP or PEEP during induction  combat peri-
induction hypoxemia

66.  Anticipated difficult intubation:
- awake intubation using topical anesthesia
and fiber-optic device approach (most
recommended method)
- intubation with the help of stylet (eschmann
stylet, tube exchanger)
- videolaryngoscopes
- intubating LMA

67. INDUCTION AND MAINTENANCE:
 Rapid sequence induction
 Larger than usual doses of induction agent required
 increased blood volume, CO and muscle mass
 Higher dose of succinylcholine increase
pseudocholinisterase
 Maintained on continuous infusion of short acting IV
agent /inhalational agent.

68.  Desflurane is inhalational agent of choice
consistent and rapid recovery
 Use of nitrous oxide is limited because high o2
demand
 Short acting opioids- provide adequate
analgesia, avoid postoperative respiratory
depression.(remifentanil, fentanyl)

69.  Dexmedetomedine (alpha2 agonist)- sedative
and analgesic properties with no effect on
respiration
 Vecuronium, rocuronium, atracurium are
preferred NDMR.

70.  Pneumoperitoneum:
- <15mmhg
- >20mmhg  vena caval
compression CO
- cephalad displacement of
diaphragm endobroncheal intubation

71.  ensure tight seal of ET tube cuff- while placing
intragastric balloon to help size the pouch or
performing leak test with methylene blue /saline
through NGT.
 completely remove endogastric tubes before
gastric division to avoid stapling / transection

72. FLUID MANAGEMENT:
 Blood loss is more  larger incision to access surgical
site
 Goal  to maintain normovolemia
 Avoid rapid infusion of intravenous fluids.

73.  According to studies,
LIBERAL APPROACH RESTRICTIVE
APPROACH
IV FLUID – 40 ML /KG TBW 15 ML /KG TBW
Advantage:
Less incidence of PONV &
rhabdomylosis
-Faster recovery of GI function
-better wound healing
-improvement in pulmonary
function and tissue
oxygenation
Disadvantage:
Weight gain, CCF Acute tubular necrosis,
rhabdomylosis

74. VENTILATION
 Tidal volume <13ml/kg of IBW
 Moderate PEEP =10cm H2O prevent postoperative
atelectasis

75.  Recruitment maneuver that is sustained lung
inflation to 40 - 55 cm H2O of inspiratory pressure
followed by PEEP  prevent atelectasis
 FiO2 titrated to minimum levels assuring
acceptable oxygenation and to avoid absorption
atelectasis.

76. EMERGENCE:
- Prompt but safe tracheal extubation
- Extubate when patient is awake, in semi-recumbent
/30 degree reverse trendlenburg position
- Give supplemental oxygen
- Observe for 5 min
- Lifting devices- HoverMatt
- patient transfer device
- gantry-style mechanical lifting devices

78. POSTOPERATIVE CONSIDERATION:
Ventilation evaluation and management : increase
incidences of atelectasis after GA,
adjuncts to avoid postoperative atelectesis -
- postoperative CPAP
- adequate analgesia
- properly fitted elastic binder for abdominal
support

79. - early ambulation
- deep breathing exercises
- incentive spirometry
- pulse oximetry and ABG monitoring
whenever required

80. Analgesia:- includes
1. multimodal analgesics
-avoids opioids
-NSAIDS
-local anesthetics
2. epidural analgesic techniques
3. early mobilization
4. supplemental oxygenation
5. elevation of head end of the bed

81. - ensures - adequate analgesia,
- early mobilization,
- adequate respiratory function
-helps to avoid complications like
 pressure ulcerations
 pulmonary emboli
 deep venous thrombosis
 pneumonia

82. EPIDURAL ANALGESIA:
Incidence of block failure is more in obese because
 Anatomical land marks are obscured
 Limited back flexion
 False losses of resistance  fat deposition
 Difficult to predict depth of space
 Catheter dislodgement

83. Following measures to be taken :
1. Proper positioning:
- sitting position is preferable – helps with
identification of midline
- patients back should be parallel to the edge
of the table - prevent lateral deviation away
from the midline

84. - if spinal process is not palpable – draw a line
from cervical vertebral spinal process to the
upper portion of gluteal cleft.
- iliac crest is difficult to appreciate – patients
skin fold used to draw a line perpendicular to
the vertical line  intersection point serve as
epidural needle insertion guide.

86. 2. Prepuncture Ultrasound imaging :
Advantage :
- helps to identify spinal processes
- predict depth of epidural space
Disadvantage:
- image quality compromised due to fat
overlying the space
- distance to the epidural space may be
inaccurate if subcutaneous tissue is compressed

87. 3. USG guided needle technique :
- long 25 G needle used for infiltration and
identification of spinal process
- can take help of the patient to confirm the
needle in the midline
(Does it feel like I am in the middle of your
back ?)
- standard 9 – 10 cm needle is sufficient
else long needle (16 cm) can be used.

88. 4. Catheter dislodgement
 Distance from epidural space to skin changes
with position–
0.6 cm if BMI < 25
1.04 cm if BMI > 30
 Ligamentum flavum has mild grip on the epidural
catheter, repositioning allows the epidural catheter
to be pulled into the subcutaneous space

89.  To prevent catheter dislodgement:
- patient should move from upright sitting
position to lateral position before securing
epidural catheter
- epidural catheter should be taped in place on
the skin after the patient has been
repositioned and without adjusting the catheter

90. ACOUSTIC PUNCTURE ASSIST DEVICE
 Guaranteed finding of the epidural space
 Penetration of the epidural space is indicated by
a clear variation of the acoustic signal
 Acoustic monitoring is superior to the sense of
touch
 Monitoring of the different layers guarantees a
safe procedure