OBESE BARIATRIC SURGERY

1. Anaesthetic consideration in
morbidly obese
Dr ZIKRULLAH

2. Introduction
• Prevalence: increasing worldwide
• Incidence:
Worldwide : 20 to 30% of adults
India : 10-15% of adults
• Precursor of morbidity & premature mortality
• BMI >35 kg/m2 at aged 50 years have double
the risk of premature death.
• challenge for the anaesthesiologist.

3. Aetiology

4. Definition
• IDEAL BODY WEIGHT (IBW)
For men: IBW (kg) = height (cm) – 100
For women: IBW (kg) = height (cm) – 105
• OVER WEIGHT: an excess of total body
weight
• OBESITY : Body weight > 20 % of IBW
• MORBID OBESITY(MO):
Body weight > twice IBW or IBW + 50kg

5. OBESITY AND ASSOCIATED RISKS ACC TO BMI

6. OTHER FACTORS & ASSOCIATED RISKS
• Central, Android (Upper body obesity)
• Peripheral, Gynecoid (lower body obesity)
• Obese with ↑ abdominal circumference
(> 102 cm.in men and >88 cm in women)
• With high waist – hip ratio (>1.0 in men, >0.85
in women) have greater risk

7. MEDICAL & SURGICAL CONDITIONS WITH OBESITY
Cardiovascular
• Hypertension
• Cardiomyopathy
• Ischaemic Heart
Disease
• Peripheral vascular
Disease
• Cerebrovascular
Disease
• Cor pulmonale
• Pulmonary Embolism
• Deep Vein Thrombosis
• Varicose veins
• Hyperlipidemia

8. Respiratory
• Restrictive lung disease
• Obstructive Sleep Apnoea
(OSA)
Gastrointestinal
• Hiatus hernia
• Inguinal hernia
Genitourinary
• Menstrual abnormalities
• Renal calculi
• Obesity Hypoventilation
syndrome
(Pickwickian Syndrome)
• Gall stones
• Gastro esophageal Reflux

9. Malignancy
• Breast
• Prostate
• Endometrial
Endocrine
• Diabetes mellitus
• Hypothyroidism
Musculoskeletal
• Osteoarthritis
• Colorectal
• Cervical
• Infertility
• Cushing’s disease
• Back pain

11. PATHOPHYSIOLOGY
• Resting blood flow to fat is 2 to 3 ml/100gm/min.
• With increasing obesity the percentage of perfusion
to fat decreases {i,e not in direct proportion}
• 1 kg increase in fat above IBW needs 20 to 30 ml
increase in C.O.
• For every 13.5 kg of fat added, app. 25 miles of neo-
vascularisation is added to the body

12. CARDIOVASCULAR SYSTEM

13. Cardiovascular Effects
• Cardiac output increases as much as 20 – 30 ml/kg of
excess body fat secondary to ventricular dilatation
and increasing stroke volume
• The increased left ventricular wall stress leads to:
• Hypertrophy
• Reduced compliance
• Impaired left ventricular filling
• Obesity cardiomyopathy

14. Cardiovascular disorders
• S. Hypertension
• P. Hypertension [h/o exertional dyspnea, fatigue,
syncope]
• IHD.
• VH [inc. in PVR & PAP, SV, BV, CO] &
Cardiomyopathy.
• CHF [Rapid weight gain indicates worsening CHF]

15. Cardiovascular Complications
• Sudden cardiac death.
• Cerebrovascular disease.
• Deep vein thrombosis.
• Pulmonary embolism

17. RESPIRATORY SYSTEM

18. • Respiratory Compliance: decreases with
BMI(upto 70%)
• Postinduction decline in FRC may be predicted
by: (post induction) FRC (as %Preanesthesia
value) = 137.7 164.4x (wt/ht).

19. Increased fat
Decreased respiratory muscle function
Decreased chest wall compliance
Increased elastic resistance
Increased pulmonary blood flow
Decreased lung compliance
Decreased total respiratory compliance in supine position
↓FRC, ↓VC, ↓TLC
Shallow & rapid breathing
Increased work of breathing
Limited maximum ventilatory capacity
RESTRICTIVE LUNG DISEASE
FRC below CC
Small airway closure
V/Q mismatch & left to right shunt
Arterial hypoxemia

20. • Reduction in ERV:
I. Encroachment of
abdominal contents on
the diaphragm.
II. Chest wall fat decrease
respiratory system
compliance.
III. Impairment of
respiratory muscle
IV. Mechanical disadvantage
V. Fatty infiltration of the
respiratory muscles in
extreme obesity.
Oxygenation:
• decrease with BMI due
to the reduction in FRC
• increase of shunt
fraction.
• Oxygen consumption is
increased with mild
exercise in the morbid
obese.

22. Obstructive Sleep Apnea:
• Prevalence:Up to 5% obese .
• Apnea= No airflow >10 s, desp
• ite continuous respiratory effort
against a closed glottis.
• Hypopnea/hypoventilation= TV
<50% for >10 s.
• Desaturation= SpO2 reduction by
>4%.

23. Obstructive Sleep Apnea/Hypopnea Syndrome
Severity of sleep apnea:
apnea/hypopnea index (AHI)=
total number of apneas and hypopneas
total sleep time
• Mild disease: AHI of 5 to 15 events /hour
• Moderate disease: AHI of 15 to 30 events/ hour
• Severe disease: AHI of ≥ 30 events /hour

24. What are the systemic pathophysiology of OSA?
Sleep Nocturnal Social Isolation
Snoring, breathlessness
Obstructed breathing O2, CO2 Arousal
Myocardial Ischemia Pulmonary Hypertension Systemic Hypertension
Arrhythmias R V H L V H

25. Diagnosis of OHA
• polysomnography,
• sleep study :
1. electroencephalogram,
2. electrocardiogram,
3. electrooculogram,
4. capnogram,
5. nasal or oral airflow,
6. esophageal pressure,
7. arterial blood pressure,
8. Pharyngeal and
extremity EMG,
9. Pulse oximetry,
10.room noise

26. TREATMENT OF OSA
Duration of
CPAP
EFFECT
2 weeks Corrects abnormal ventilatory drive
3 weeks Increases LVEF in CHF
4 weeks Reduces B.P, HR, 35% increase in E.F
4-6 weeks Reduced tongue volume & increased pharyngeal space
8 weeks Reduction in CVS risk
3-6 months Reduction in PAH

27. Effects on Blood Volume
• Total blood volume is increased in the obese, but on
a volume-to-weight basis, it is less than in nonobese
individuals(50ml/kg compared to 70ml/kg)
• Most of this extra blood volume is distributed to the
fat organ

28. GASTROINTESTINAL SYSTEM
• Prolonged Gastric Emptying time, Decreased
Gastric pH,
• Increased chances of Hiatal Hernia.
• Increased risk of Aspiration Pneumonitis.
• Inguinal hernia.

29. HEPATOBILIARY SYSTEM
1. Nonalcoholic Fatty Liver disease
2. Nonalcoholic Steatohepatitis.
3. Cholelithiasis,
4. Biliary tract disease,
5. Hepatitis,
6. Intra and Extra hepatic Cholestasis.

30. ENDOCRINE SYSTEM
• Type II DM is common in Obese patients.
• Secondary obesity may be associated with:-
Hypothyroidism
Cushing’s disease
Hypogonadism
Hypothalamic Disorders

31. Obesity and Diabetes
• adipose tissue proinflammatory mediators
• (TNF-α, IL-6)
• signalling off of insulin downregulation ofPPAR-γ
insulin resistance
Type II diabetes

32. METABOLIC SYNDROME

33. Waist circumference
>102cm in men
>88cm in women
Metabolic
Syndrome
Triglycerides
>150mg/dl
HDL cholesterol
<40mg/dl in men
<50 mg/dl in women
Blood pressure
>=130/85 mm of hg
Fasting Glucose
>=110mg/dl

34. Features Associated with Metabolic Syndrome
• Abdominal obesity
• Atherogenic dyslipidemia (TGs, ↓ HDL-C, Apo B, small
LDL particles)
• Insulin resistance with or without glucose intolerance
• Proinflammatory state (hs CRP)
• Prothrombotic state (PAI-1, ↓ FIB)
• Others (endothelial dysfunction, micro albuminuria,
polycystic ovary syndrome, hypoandrogenism, non
alcoholic fatty liver disease, hyperuricemia)

35. PHARMACOLOGY
• Drug dosing should take into consideration the
volume of distribution (VD) for administration of
the loading dose, and on the clearance for the
maintenance dose.
• Dosing should be calculated based on
LBW/TBW.

36. • IBW (kg) = height (cm) – x
where x is 100 for adult males
105 for adult females.
• Lean body weight (LBW) is the total body
weight (TBW) minus the adipose tissue
• In morbidly obese patients, increasing the IBW
by 20 to 30% gives an estimate of LBW.

37. • The VD in obese patients
is affected by
• reduced total body water,
• increased total body fat,
• increased lean body mass,
• Altered tissue protein
binding,
• increased blood volume
& cardiac output,
• increased blood
concentrations of free
fatty acids, cholesterol,
and organomegaly.

38. • Plasma protein
binding
– Adsorption of lipophilic
drugs to lipoproteins
(increases free fraction
of drug)
– Plasma albumin
unchanged
– Increased alpha 1
glycoprotein
• Drug clearance
• Increased RBF
• Increased GFR
• Increased tubular
secretion
• Decreased Hepatic
blood flow in CCF

39. • Increased Vd prolongs drug elimination half-
life even when clearance is unchanged or
increased.
• Drugs that undergo phase I metabolism
(oxidation, reduction, hydrolysis) are generally
unaffected by changes induced by obesity,
while phase II reactions (glucuronidation,
sulfation) are enhanced

40. • Renal clearance of drugs is increased .
• Highly lipophilic substances such as barbiturates
and benzodiazepines show significant increases in
VD for obese individuals
• Exceptions to this rule include the highly
lipophilic drugs Digoxin, Procainamide, And
Remifentanil

41. • IBW- Propofol, Vec, Rocuronium, Remifentanyl
• TBW- Thio, Midaz, Sch, Atra, Cis-atra,
Fentanyl, Sufentanil
• Maintainence- Propofol- TBW
Sufentanil- IBW

42. Pre-anesthetic Assessment
• Detailed history to rule out or find co morbid conditions,
history of previous surgeries, their anesthetic challenges
(i.e., ease or difficulty in securing the airway, intravenous
access), need for ICU admission, surgical outcomes
• What history will diagnose OSA in an obese patient?
Snoring & / or apnea during sleep & apparent arousal.
Extremity movement, frequent turning in sleep
Daytime sleepiness.
Fatigue?

43. • What special drug history
needs to be taken?
• Fenfluramine [heart &
lung effect-stop 2 wks],
• Sibutramine [arrhythmias
& hypertension],
• Orlistat [ needs
supplementation of
vitamins A,D,E,K].

44. • Respiratory system:-
• smoking history,
• exercise tolerance,
• history of hypoventilation and somnolence,
• Pulmonary function tests with spirometry
•
TV, IRV is reduced in morbidly obese people.
• RV remains normal.
• ERV, FRC, VC and TLC are markedly decreased.

45. • Lung compliance is usually normal
but chest wall compliance is
reduced.(total compliance >30%
less)
• Work of Breathing is increased.
• Max. voluntary ventilation may
also be reduced.

46. AIRWAY CHALLENGES:
I. Airway obstruction with light to moderate sedation .
II. Difficult to mask ventilate,.
III. Higher incidence of difficult intubation and failed intubation
in MO.
IV. Presence of hypopharyngeal adipose tissue , interfers with
the line of sight (LOS) at direct laryngoscopy.
V. Presence of pretracheal adipose tissue, worsens the
laryngoscopic view.

47. PHYSICAL EXAMINATION
• Respiratory.
• Cardiovascular.
• Endocrine.
• Gastrointestinal.
• Renal and Genitourinary.
• Musculoskeletal.

48. Airway Evaluation:
SPECIFIC ASSESSMENTS
Body mass index [BMI]:
incidence of difficult intubation ranges between 13-24% in
obese patients.
Neck circumference:
obese patients with neck circumference > 50 cm had a greater
chance of problematic intubations than those < 50 cm.
Length of neck
short neck [actual length not defined] is associated with a 5-
fold increase in difficult airway.

49. • Anterior neck soft tissue: superior predictor of
difficult intubation in obese patients than obesity per
se or a thick neck.
• obtained by ultrasound quantification of soft tissue at
the level of the vocal cords, thyroid isthmus and
suprasternal notch.
• Averaged value >28 mm predicts difficult
laryngoscopy

50. AIRWAY EXAMINATION
• Atlanto-occipital joint extension,
• Mallampati classification,
• Temporomandibular joint (TMJ) assessment with
inter-incisor distance, mentohyoid distance, and
• Dentition, large protuberant teeth,
• Limited neck mobility
• Retrognathia
• Neck circumference,
• Hypertrophic tonsils and adenoids.

51. Investigations
Routine Tests
1. Hematological work-up
2. ECG
3. Chest X-ray
4. Blood Glucose
5. Lipid Profile
6. Liver Function Tests
7. S. Creatinine

52. Special Investigations
• Sleep Studies
• Cardiac Stress Test
• Echocardiography
• Radionucleotide ventriculography
• PFT, Spirometry
• ABG
• Thyroid Function Tests

53. PREMEDICATION
• No sedatives or narcotics should be given to a
morbidly obese patient as premedication.
• Can be given in operating room along with
supplementary oxygen to prevent hypoxia from
respiratory depression.
• glycopyrollate (0.4 mg), an anticholinergic used to
dry the upper airway,

54. • Continue antihypertensive medication [ACE Inhibitors?].
• Start prophylactic Antibiotic for wound infection
• Heparin prophylaxis against DVT
• H2 receptor antagonist [proton pump inhibitor].
• Metoclopramide to increase gastric emptying, (peak effects occur in
approximately 45 minutes) and non particulate antacids

55. • Highly lipophilic drugs have increased volume of distribution
(VD)
• doses acc. to patient's total body weight (TBW).
• Examples are thiopental, propofol, BZD, fentanyl,
dexmedetomidine, succinylcholine, atracurium

56. • Weakly lipophilic or lipophobic drugs have
unchanged VD.
• Doses acc. to patient's lean body weight (LBW),
LBW = IBW + 20% to 40% IBW.
• Examples of this group are ketamine,
vecuronium, rocuronium , remifentyl ( lipophilic)

57. Pre-emptive analgesia:
with medications that do not cause respiratory
Depression.
• NMDA (N-methyl-D-aspartate) antagonists
• alpha-2-receptor agonists
• NSAIDs (non-steroidal anti-inflammatory drugs)
• GABA – like compounds

58. Monitoring
• Pulse oximetry,
• Electrocardiogram,
• Noninvasive blood pressure,
• End-tidal carbon dioxide,
• Temperature,
• Hourly urine output
• Peripheral nerve stimulator
• Bispectral index(BIS )

59. • Invasive arterial monitoring is used in severe
cardiopulmonary disease or poor fit of the non invasive
blood pressure cuff
• Central venous access is typically used when there are
difficulties obtaining peripheral access
• A pulmonary artery catheter in pulmonary hypertension, cor
pulmonale, or LVF

60. Patient Positioning
• Awake patient can self-position on the OR
table.
• Arrange HELP [Stacked or Ramped] position
from scapula to the head.
• Pad all pressure point.
• Maintain & pre-oxygenate in head-up
position.
• Apply pneumatic leggings or compression
stockings.

61. • RAMPING ADVANTAGES:
– Improves laryngoscopic view
– The gradient for passive regurgitation is reduced
– The safe apnea period is increased.
• 25-30 degrees reverse trendelenburg position
with manual PEEP/NIPPV improves oxygenation
• For HELP placement, the preformed Troop
Elevation Pillow may be used in place of folded
towels or blankets .

62. Effect of various positions:
• Supine
• Causes ventilatory impairment and inferior vena cava and aortic
compression
• Trendelenburg
• Further worsens FRC and should be avoided
• Reverse tredelenburg
• Increased compliance results in lower airway pressures
• Prone
• Detrimental effects on lung compliance, ventilation and arterial
oxygenation
• Increased intra-abdominal pressure worsens IVC and aortic
compression and further decreases FRC

64. Positioning for Laparoscopic Surgery:
• The head-down tilt of 10–20 degrees :
• increase in central blood volume and a decrease in vital
capacity and diaphragmatic excursion.
• reverse Trendelenburg (rT) position :
improved pulmonary dynamics but reduced venous return.
These changes associated with positioning may be influenced by
the extent of the tilt, the patient’s age,

65. PREOXYGENATION
• Obese patients initially be placed in a ramped position and then
in the reverse trendelenburg position before preoxygenation.
• Patients are then preoxygenated for 3 to 5 minutes with 100%
oxygen under positive pressure 8 to 10 cm H2o
• After induction, maintain 10 to 12 cm H2O PEEP , but care
must be taken to treat any hypotension that may occur.

66. INDUCTION
• In current anesthetic practice propofol is the IV induction agent of
choice for obese patients
• Sevoflurane may be considered because of a more consistent and
rapid recovery profile. Halothane may be used
• Maintainence with desflurane or sevoflurane
• Nitrous oxide not recommended for maintenance use as it causes
intestinal inflation and is emetogenic.

67. • N2O use is contraindicated with pre existing severe
pulmonary hypertension.
• Remifentanil is the intraoperative narcotic of choice because
of its rapid onset, consistent profile, and rapid offset
• Dose of succinylcholine is increased [1.2-1.5 mg/kg]. Non-
depolarizing relaxants show variability in response hence
titrate dose with PNS.

68. Factors responsible for difficult laryngoscopy &
intubation in obese patient?
• Fat face & cheeks.
• Large breasts in females.
• Limited range of motion of head, neck, & jaw.
• Small mouth & a large tongue.
• Excessive palatal & pharyngeal tissue.
• Short thick [large circumference] neck.
• High Mallampati scores [III or IV].
• O2 desaturation is more rapid.

69. Intubation strategy
• Awake FOI shall be an ideal technique but is not easy
to achieve.
• obscured landmark may hinder nerve block.
• Sedation & analgesic used during preparation may
result in hypercapnia, hypoxia & airway obstruction.
• During difficult intubation, nerve blocks may
“unprotect” the airway.

70. • RSI could be contemplated using short acting inducing
agents as propofol with succinylcholine ,with the patient
positioned on a ramp.

71. If the intubating conditions are suboptimal, a noninvasive
alternative airway management device is utilized.
LMA fastrach, LMA CTrach

72. • Bullard Laryngoscope , Polio blade or McCoy laryngoscope ±
gum elastic bougie]
• Failed intubation or CVCI management includes Proseal LMA,
combitube.

73. • PLMA
• Combitube
• LMA Classic
• Emergency cricothyrotomy.

74. Maintenance of anesthesia
• Combined epidural/general (GA) may be beneficial to
decrease GA requirements.
• Consider a "balanced" GA >decreases required dose of each
agent, so less will be around postop.
• Consider using short acting agents (e.g. alfentanyl, propofol,
versed, atracurium), and
• avoid using long acting agents (e.g. morphine, valium,
pancuronium)
• Ventilator:
• Use large tidal volumes 15-20ml/kg ideal body wt.
• Titrate PEEP to maintain oxygen saturation.

75. FLUID MANAGEMENT:
• Although the total circulating blood volume is
increased, it is less than normal on a weight
basis, since fat contains little water.
• Adequate preoperative hydration and higher
intraoperative fluid administration (20-40
ml/kg) reduce postoperative complications

76. • Blood loss is usually greater.
• Excess adipose tissue may mask peripheral
perfusion, making fluid balance difficult to
assess.
• Early infusion of colloids and blood products
may be necessary because they are less able
to compensate for small volumes lost,
– but rapid infusion of excessive amounts should
be avoided because pre-existing CCF is common

77. Pre-requisites for extubation
• Intact neurologic status, fully awake and alert, with head lift
greater than 5 s
• Hemodynamic stability
• Normothermia.
• Train-of-four (TOF) reversal by PNS (T4/T1 >0.9). Full reversal of
NM blocking agents.

78. • Respiratory rate (10 - 30/min)
• SPO2 >95% onFIO2 0.4
• Acceptable ABG (FIO2 of 0.4: pH, 7.35 to 7.45; PaO2, >80 mm
Hg; PaCO2, < 50 mm Hg).
• Tidal volume (VT) >5 mL/kg ideal body weight

79. EXTUBATION
• if no C/I , Reverse Trendelenburg or semi-sitting position,
• Use OPA/ NPA. 2-person mask ventilation on standby.
• If initial difficult airway– extubate over an airway exchange
catheter.
• If the pt was on CPAP preoperatively, then arrange for CPAP
post-extubation.

80. Post op complications
• Postanesthetic hypoxemia
• Respiratory depression
• Early ventilatory failure with need for reintubation
• Positional ventilatory collapse
• Hemodynamic instability,
• PONV
• Venous thromboembolism

81. Postoperative pain
• Epidural opioids + local anesthetics
• PCA is also a desirable option.
• Parenteral NSAID’s can reduce the dose of narcotics.
• IM injections tend to become SC and demonstrate
unpredictable blood levels & effects. IV analgesics are
preferred.

82. • Risk of hypoxemia shall persist for 4-7 days. Supplemental O2 is
mandatory in the sitting or semi-recumbent position as & when
required. Monitor SpO2.
• Aggressive pulmonary care with incentive spirometry, cough,
deep breathing & early ambulation.
• Increased incidence of wound infection
• Continue LMWH & leg compression stockings.

83. Measures to avoid pulmonary complications:
1. Keep pt. in semirecumbent position (30 degrees- 45degrees).
2. Use humidified gases; Start chest physical therapy (P.T.)early.
3. Nocturnal use of nasal continuous positive airway pressure (CPAP)
at 10-15cmH2O, if there is presence of Obstructive Sleep Apnea.

84. INTRAOPERATIVE OXYGENATION
• No effect on increasing TV (Pressure controlled
ventilation with low tidal volumes 6-8ml/kg )
• VC and recruitment maneuvers
– Increased oxygenation
– Decrease atelectasis
– Shortens PACU stay
– Less respiratory complications.
• The recruitment maneuver consists of providing
escalating levels of PEEP in 5 cm increments upto a
maximum airway pressure of 40-42cm H2O, continue
for 10 breaths and reduce PEEP back to basal levels.

85. REGIONAL ANAESTHESIA
• underutilized (PCA is >90%) in this patient population
• technical difficulties,
• increased incidence of epidural failure and catheter
dislodgment,
• decreased epidural space form intraabdominal pressure
causing unpredictable spread of local anesthetics, variable
block level

86. • For epidural catheter insertion ,patients should be
positioned in a sitting position, and
ultrasonography guidance is recommended.
• For peripheral surgical procedures, peripheral
nerve blocks used, provided that adequate
landmarks exist.

87. Considerations in Obstetrics:
• chronic htn, pregnancy induced htn (preeclampsia) and diabetes
(2 to 8fold increase in incidence).
• difficulty in labor, or abnormal labor, induced labor, cesarean
section (c/s).
• fetal macrosomia, with attendant risks and difficulty in delivery.
• greater blood loss during c/s, longer surgery postoperative
complications
• Increased risk of anesthesia related maternal morbidity/mortality
during c/s, when compared with nonobese pts.
• Increased risk of fetal morbidity/mortality , fetal distress.

88. • Cephalad retraction of panniculus in morbidly obese during c/s
may lead to hypotension & fetal compromise, as well as
maternal difficulty in breathing (secondary to extra weight on
the chest).
• Loss of intercostal muscle function during spinal anesthesia
may create greater breathing problems in the obese
parturient, when compared with the nonobese pt.

89. • Supine and trendelenburg positions may further
decrease FRC, increasing the likelihood of
hypoxemia.
• Use of PEEP to increase oxygenation may decrease
cardiac output, and possibly compromise uterine
blood flow.
• The anesthesiologist’s main concern -to avoid an
emergency situation requiring urgent endotracheal
intubation.

90. Epidural anesthesia offers several advantages:
• easily titratable local anesthetic dose and level of
anaesthesia,
• ability to extend the block for surgical delivery and
prolonged surgery,
• slower and more easily controllable hemodynamic
changes,
• decreased potential for excess motor blockade
• postoperative analgesia

91. SUMMARY
• Detailed history
• Examination
• Investigation
• Aspiration prophylaxis
• Minimal sedation
• Positioning
• Preoxygenation
• Prepare for difficult airway
• Follow extubation criteria
• Arrange fop CPAP and mechanical ventilation
• Adequate pain relief. Pulmonary care and DVT prophylaxis
DIAGNOSIS OF COMORBIDITY &
OPTIMIZATION

92. THANK YOU