The presentation will let you know about the Obese Patients and Bariatric Surgery

1. ANAESTHESIA FOR MORBIDLY OBESE
PATIENTS AND BARIATRIC SURGERY
DR.SANDEEP.G.B.
NARAYANA MEDICAL COLLEGE
NELLORE

2. OVERVIEW
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DEFINITION
EPIDEMIOLOGY
SCALES
PATHOPHYSIOLOGY
OBESITY – ANAESTHESIA CHALLENGES
BARIATRIC SURGERY & ITS COMPLICATIONS

3. DEFINITION
Body weight that exceeds the
expected or ideal weight by more than
10%, taking into account height, age,
body build and sex.

4. EPIDEMIOLOGY
• Incidence:
– Worldwide : 20 to 30% of adults
– India : 10-15% of adults

5. Aetiology

6. MEASURING SCALES
• BODY MASS INDEX (Quetelet's index) (Kg/m2)

7. • WAIST CIRCUMFERENCE

8. 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
neovascularisation is added to the body

9. CARDIOVASCULAR SYSTEM

10. CARDIOVASCULAR SYSTEM

11. OBESITY CARDIOMYOPATHY
• Various heart tissues are replaced by fat cells
and become dysfunctional.
• Conduction defects, pressure induced atrophy
of myocardial cells.
• Secrete adipokines which are deleterious to
adjacent cells.
• ↑C.O and Blood Volume LV dilatation and
hypertrophy  diastolic dysfunction

12. • If wall thickening fails to keep in pace with
chamber dilatation then systolic failure occurs.
• This leads to cardiomyopathy  CCF and
sudden cardiac arrest.

13. COAGULOPATHY
• Hypercoaguability :
– Obese individuals have higher levels of Fibrinogen,
Factor VII, Factor VIII, Von Willebrand Factor, And
Plasminogen Activator Inhibitor-1 (PAI-1).
– Hypofibrinolysis

14. RESPIRATORY SYSTEM
• Restrictive lung disease
• Obesity hypoventilation syndrome (OHS)
• Obstructive sleep apnea (OSA)
• Corpulmonale

15. RESTRICTIVE LUNG DISEASE
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
FRC below CC
Small airway closure
V/Q mismatch & left to right shunt
Arterial hypoxemia

16. • Reduction in FRC is primarily a result of REDUCED
ERV, but the relationship between FRC and closing
capacity, the volume at which small airways begin to
close, is adversely affected.
• Residual volume and closing capacity are unchanged
• Anesthesia worsens this situation such that up to a
50% reduction in FRC occurs in the obese
anesthetized patient compared with 20% in the
nonobese individual.

19. DEFINITIONS:
OBSTRUCTIVE SLEEP
APNEA
1. Complete cessation of
airflow.
2. Lasting 10 seconds or
longer
3. 5 0r more times per hour
of sleep
4. Decrease of atleast 4% in
SaO2
OBSTRUCTIVE SLEEP
HYPOPNEA
1. Partial reduction of airflow
of greater than 50%.
2. Lasting atleast 10 seconds
3. 15 or more times per hour
of sleep
4. Decrease of atleast 4% in
SaO2

20. • Diagnosis is made by Polysomnography and is
reported as the APNEA/HYPOPNEA INDEX
(AHI).
• AHI is the Total number of episodes of apnea
and hypopnea divided by the total sleep time.
Normal : 5 to 10 events per hour
Mild
: 10 to 15 events per hour
Moderate: 15 to30 events per hour
Severe : > 30 events per hour

21. • TOTAL AROUSAL INDEX is the total number of
arousals per hour.
• RESPIRATORY DISTURBANCE INDEX is the sum
of total arousal index and apnea hypopnea
index.
• Patients diagnosed to have maoderate/ severe
OSA have to undergo CPAP prior to elective
surgery

22. 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

23. OBESITY HYPOVENTILATION SYNDROME
(OHS)/PICKWIKIAN SYNDROME
• Presence of obesity (BMI >30) and awake
arterial hypercapnia (PaCO2 >45mm Hg) in the
absence of known causes of hypoventilation.
• Results from long term OSA

24. Impaired ventilatory response to hypoxia + hypercapnia
↓
Mechanical load of obesity + upper airway obstruction
↓
Prolonged hypoxia + Hypercapnia at night
↓
Alteration in control of breathing
↓
Progressive desensitization of respiratory centres to hypercapnia
↓
Type II Resp. Failure
Main ventilatory impairment is :
•Alveolar hypoventilation irrespective of intrinsic lung disease
•Day time hypersomnalence
•Hypercapnia, hypoxemia and polycythemia
•Pulmonary hypertension and right heart failure

25. PARAMETER
OHS
OSA
Gender
Males = females
Males > females
Obesity (BMI ≥30 kg/m2)
Yes
May be
Ventilation pattern
Hypoventilation
Normal
PaCO2 (mm Hg)
Increased (>45 mm Hg)
Normal (increased during
apnea)
Pao2 (mm Hg)
Decreased; most severe
during REM sleep
Normal (decreased during
apnea)
Sao2 (%)
Decreased
Normal (decreased during
apnea)
Nocturnal upper airway
obstruction
No
Yes
Pulmonary hypertension
More common and severe
Less common
Nocturnal monitoring
Increased PaCO2 during sleep ≥5 obstructive breathing
to >10 mm Hg from awake
events per hour of sleep
supine values. O2 desaturation
during sleep not explained by
apnea or hypopnea

26. GASTROINTESTINAL SYSTEM
• Gastric volume and acidity are increased.
• Delayed gastric emptying
– because of increased abdominal mass that causes
antral distention
– gastrin release
– a decrease in pH with parietal cell secretion.
– increased intragastric pressure,
– Increased frequency of transient LES relaxation

27. • An increased incidence of hiatal hernia and
gastroesophageal reflux also increase aspiration
risk.
• Gastric emptying is faster with high energy content
intake such as fat emulsions, but because of larger
gastric volume, the residual volume is increased.
• Fatty liver & Non alcoholic fatty liver disease

28. RENAL AND ENDOCRINE SYSTEMS
• Impaired glucose tolerance  Type II D.M
• Subclinical hypothyroidism with electrolyte
imbalance
• Glomerular hyperfiltration
• Excessive weight gain causes:– increases renal tubular resorption
– impairs natriuresis through activation of the
sympathetic and renin-angiotensin system as well as
physical compression of the kidney.
– Loss of nephron function if prolonged obesity

29. METABOLIC SYNDROME
• FEATURES:– Abdominal obesity
– Atherogenic dyslipidemia
– Hypertension
– Insulin resistance ± glucose tolerance
– Proinflammatory state
– Prothrombotic state
– Others: endocrine dysfn.,microalbuminuria, PCOS,
hypoandrogenism, NAFLD, hyperuricemia

30. • DIAGNOSIS:- 3 of the following

31. 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.

32. • 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.

33. • 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.

34. • 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

35. • Increased Vd prolongs drug elimination halflife 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

36. • 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

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

39. INVESTIGATIONS
• CBC, FBS,RFT,SCREENING,LFT
• ECG
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Low voltage complexes
LVH/Strain
Prolonged QT/QTc
Inferolateral T wave abnormalities
RAD/RBBB
P- Pulmonale
CXR, X –ray neck
ECHO
Polysomnography
Lipid profile

41. TREATMENT
• Medical treatment
– Behavioural modifications
– Dietary & herbal medications
– Phamacological: Sibutramine/ Orlistat
– Implantable electrical stimulators
• Surgical treatment- BARIATRIC SURGERY

42. BARIATRIC SURGERY
• Malabsoptive- jejenoileal
bypass / RYGB/
biliopancreatic diversion
• Restrictive- Gastroplasty /
adjustable gastric banding

43. PREOPERATIVE CONSIDERATIONS
• PAC:– Look for HTN/DM/CCF/OHS
• OHS -AHI >30- rapid and severe desaturation on
induction
-CPAP>10 – difficult face mask ventilation
– Previous h/o surgeries/ anesthetic administration/
airway problems/ICU admissions
• STOP BANG:
– Snoring, Tiredness, Observed apnea, blood
Pressure, BMI, Age, Neck circumference, Gender

44. • For repeat bariatric surgery
– Screen for metabolic and nutritional abnormalities.
– Acute postgastric reduction surgery neuropathy.
– Electrolyte and coagulation indices
• Evidence of OSA and OHS should be sought
– associated with difficult laryngoscopy
– a neck circumference >40 cm correlates with an
increased probability of OSA.
– patients on CPAP at home should be instructed to bring
it with them as it may be needed postoperatively

45. • Lab investigations- lipid profile / FBS/ LFT/ CBC/ ECG/2D
ECHO/RFT/ VIT-B12/ THYROTROPIN/PFT
• Arterial blood gas measurements
• NBM for 12 hrs
• Avoid pre operative sedatives & hypnotics
• Multimodal antiemetic therapy
• Continue routine medications

46. CONCURRENT, PREOPERATIVE, AND
PROPHYLACTIC MEDICATIONS
• Usual medications should be continued except
insulin and OHA.
• Antibiotic prophylaxis
• Prophylaxis against Aspiration Pneumonitis and
DVT.
• Dexmedetomidine, because of its minimal
respiratory depressant effects, may be
considered for anxiolysis

47. • DVT prophylaxis:
– Risk factors: venous stasis, BMI ≥60, truncal
obesity, and OHS/OSA
– Subcutaneous heparin 5,000 IU administered
before surgery and repeated every 8 to 12 hours
until the patient is fully mobile
Or
Enoxaparin, 40 mg, injected subcutaneously every
12 hours

48. AIRWAY
• Limitation of movement
of the atlantoaxial joint &
cervical spine by upper
thoracic and low cervical fat
pads; excessive tissue folds in
the mouth and pharynx;
• Short, thick neck
• Suprasternal, presternal, and posterior cervical fat;
• A very thick submental fat pad.

49. • OSA
• Excess pharyngeal tissue deposited in the
lateral pharyngeal walls may not be noticed
during routine airway examination
• Neck circumference has been identified as the
single biggest predictor -5% with a 40-cm &
35% probability at 60-cm

50. INTRAOPERATIVE CONSIDERATIONS
• POSITIONING
– Specially designed tables or two regular operating
tables
– operating tables capable of holding up to 455 kg, with a
little extra width to accommodate the extra girth
– Strapping obese patients to the operating table in
combination with a malleable bean bag helps keep
them from falling off the operating table.
– protecting pressure areas - pressure sores, neural
injuries, and rhabdomyolysis (carpal tunnel syndrome).

51. • SUPINE POSITIONING
– Ventilatory impairment
– Inferior vena cava and aortic compression
– FRC and oxygenation are decreased
– Head-down positioning further worsens FRC
– Significant increase in oxygen consumption and
cardiac output.

52. • Head-up position & Intraoperative PEEP can
– decrease alveolar-arterial oxygen tension
difference
– increase total respiratory compliance
– Decreases peak and plateau airway pressures
• Lateral decubitus position allows for better
diaphragmatic excursion and should be
favoured over prone positioning

53. MONITORING
• Std monitoring
• Invasive arterial pressure monitoring may be
indicated for the super morbidly obese.
• BIS and entropy monitoring to titrate depth of
anaesthesia
• Monitoring of neuromuscular junction
• Central venous catheterization may also be
required for intravenous access

54. INDUCTION, INTUBATION, AND
MAINTENANCE
• Adequate preoxygenation is vital & performed with 10
L/min of oxygen to avoid rapid desaturation.
• Application of PPV during preoxygenation decreases
atelectasis formation and improves oxygenation.
• 4 vital capacity breaths with 100% O2 within 30 seconds
have been suggested as superior to the usually
recommended 3 minutes of 100% preoxygenation in
obese patients.

55. • Larger doses of induction agents may be
required
• Increased dose of Sch is necessary because of
an increase in activity of pseudocholinesterase.

56. INTUBATION
• If a difficult intubation is anticipated, awake intubation is a
prudent approach.
• Sedative-hypnotic in minimal doses.
• Sedation with Dexmedetomidine provides adequate
anxiolysis and analgesia without respiratory depression.
• Hypoxia and aspiration of gastric contents should be
prevented at all costs.

57. STACKING

59. • 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 .

61. MAINTAINENCE
• Continuous infusion of a short-acting intravenous
agent, such as Propofol, or any of the inhalation
agents, or a combination, may be used.
• Inhalatinal agents that are minimally metabolized
are useful agents, with Desflurane possibly providing
better hemodynamic stability and faster washout.

62. • Rapid elimination and analgesic properties make
N2O an attractive choice, but high oxygen
demand limits its use.
• Short-acting opioids, combined with a lowsolubility inhalation agents, facilitate a more
rapid emergence without increasing opioidrelated side effects.
• Cis-atracurium possesses an organ-independent
elimination profile and is a favorable NDMR for
use during maintenance.

63. INTRAOPERATIVE OXYGENATION
• No effect on increasing TV (Pressure controlled
ventilation with low tidal volumes 6-8ml/kg )
• VC and recruitment maneuvers
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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.

64. 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

65. • 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

66. INTRAGASTRIC CALIBRATION TUBE
• Intragastric calibration tube is used instead of
a Ryle’s tube.
• It is a bilumen tube with one port for suction
and another port in which 15-20ml of saline is
injected to inflate the intragastric balloon.
• This balloon enables the surgeon to place the
gastric band just below the esophagogastric
junction which is then tightened and helps in
deciding the size of the gastric pouch.

67. EMERGENCE
• Prompt extubation reduces the likelihood of
ventilator-dependence.
• Patient should be fully awake, follow oral
commands, have adequate muscle strength,
Adequate tidal volume and brisk airway reflexes.
• Reverse residual neuromuscular blockade.
• Extubated in the same position as for intubation
• Supplemental oxygen should be administrated
after extubation.

68. LIFTING AND TRANSFERING

69. • There is an increased incidence of atelectasis.
• Initiation of CPAP or BiPAP may improve
oxygenation but does not facilitate CO2 elimination.
• Adequate analgesia, use of a properly fitted elastic
binder for abdominal support, early ambulation,
deep breathing exercises, and incentive spirometry
are all useful adjuncts.
• Pulseoximetry and ABG should be monitored
appropriately.

70. REGIONAL ANESTHESIA
• Help avoid potential intubation difficulties
• Difficult because of inability to identify usual
bony landmarks
• Central neuraxial block is easier in the lumbar
region because the midline in this area has a
thinner layer of fat than other areas of the spinal
column.
• Longer needles and the sitting position are other
useful tools that facilitate central neuraxial
anesthesia.

72. • Epidural vascular engorgement and fatty
infiltration reduce the volume of the space,
making dose requirements of L.A 20 to 25% less
in obese patients
• The height of a SAB can be unpredictable
because of considerable upward spread within a
short time, causing cardiorespiratory
compromise.

73. • A continuous catheter SAB therefore seems an
attractive choice that allows careful titration
of the L.A to desired effect and level.
• Spirometric parameters such as PEFR and
maximum mid expiratory flow are reduced in
obese patients receiving subarachnoid block
• Combined epidural and general anesthesia

74. CONCLUSION
 Comorbidities
 Positive pressure ventilation
 Drug dosing
 Airway & intubation problems
 Rapid desaturation
 Positioning
 Post operative hypoxia
 Technical difficulties in regional techniques.
 Higher level of blockade

75. REFERENCES
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Miller’s Anesthesia
Barasch clinical anesthesia
Stoeltings coexisting diseases
Internet

76. Thank you