This document discusses anesthesia considerations for bariatric surgery. It begins with definitions of obesity classifications based on BMI. It then discusses the increased risks that obese patients face from cardiovascular and pulmonary complications. Key points in the anesthetic management include careful preoperative evaluation and optimization of comorbidities, strategies for airway management and ventilation given the increased risk of difficulties, appropriate patient positioning and monitoring during surgery, and thromboprophylaxis given the risk of VTE. Overall anesthetic goals are to prevent hypoxemia and carefully manage any cardiovascular or pulmonary issues.

1. Anesthesia for bariatric surgery
Dr. POONAM KALRA
ASSOCIATE PROFESSOR
Department of Anaesthesiology
S.M.S Medical College, Jaipur

2. Introduction
 Approximately 7% of the world population is
obese.
 Obesity is a global health problem & prevalence
varies with socio economic status.
 In affluent countries like U.S the poor have the
highest prevalence
 In developing countries it is the affluent that are at
the highest risk
 Recently there is increase in incidence of
childhood & adolescent obesity & importantly
these children remain obese as adults.

3.  Body mass index(BMI) is normally used to define
obesity
 BMI=Weight in kilograms/Height in meter square
 Classification:
BMI in Kg/m2 Category
Less than 25 Normal
25-30 Overweight
30-35 Obese
More than 35with coexisting Morbidly Obese
disease or
More than 40
More than 50 Super Obese

4. Other indices:
 BMI = TBW in kg/height in m2
 IBW ( Ideal body weight)
IBW = height (cm) – 100 for men or 105 for women
or
IBW = 0.8 × TBW for men or 0.75 × TBW for women
 LBW ( Lean body weight)
LBW = IBW × 1.3
 Broca’s Index:
Height in Cm-100 for Men
Height in Cm-105 for Women.

5. Diseases linked to Obesity

6. Psychological complications of
Obesity
 Emotional distress
 Discrimination
 Social stigma
 Anxiety,fear,insecurity

7. Surgical treatment of obesity
 Surgeries performed for the treatment of morbid
obesity is known as bariatric surgery
 Surgery is a option for weight loss in patients with
1. BMI of > 40 kg/m2, or > 35 kg/m2 with
comorbidities
2. Failure to lose weight with dietary restrictions and
pharmacologic therapy for > 1 y
3. Obesity for > 5 y
4. Understanding of the surgical and anesthetic risks
and benefits
5. Willingness to adhere to lifelong dietary restrictions
6. Acceptable operative risk

8.  Surgical approaches can be
1) Malabsorptive
a) Jejuno-ileal bypass
b) Biliopancreatic bypass
2) Restrictive
a) Vertical banded gastroplasty
b) Adjustable gastric banding
c) Sleeve Gastrectomy

9. RestrictiveLaproscopic
Vertical banded Type Sleeve Gastrectomy
Decrease the size of the
gastroplasty adjustable gastric
Surgical creation of a gastric stomach to approximately
banding 20% of its original size
pouch that can In this a band is placed
accommodate 25 to 30 mL and Gastric fundus and body is
around the stomach just resected to form a tube like
restricts the amount of food that below the esophageal
can be consumed opening from the gastro
gastric junction & esophageal junction to the
tightened with a balloon pyloric valve.
filled with 15ml saline. The reconstructed stomach
Advantages: the tension will have a total volume of
on the band is adjustable between 100 and 200 mL.
& the system is
removable

10. Roux-en-Y gastric bypass Biliopancreatic Diversion With Duodenal
Switch
Involves anastomosing the proximal gastric Includes a hemigastrectomy or sleeve
pouch to a segment of the proximal jejunum, gastrectomy to create a 75- to 100-mL pouch.
bypassing most of the stomach and the entire The ileum is connected directly to the gastric
duodenum. pouch, completely bypassing the duodenum
Advantages : Reversible and jejunum (alimentary limb). The distal
Disadvantages: Leak from anastomosis portion of the biliopancreatic limb is then
Bowel obstruction reconnected 100 cm from the ileocecal valve.
Vitamin Deficiency Disadvantages: Gallstones & various
Intestinal Stenosis deficiencies.

11.  A new procedure under investigation is
an implantable gastric stimulator.
 A pulse generator the size of a cardiac
pacemaker is implanted on the surface of
the stomach.
 The afferent impulses that are sensed by
the brain allow the person to feel satiated.

12. Contraindications for Surgery
 Unreasonable surgical risk
 Untreated hypothyroidism
 Gastrointestinal inflammatory disease (e.g.,
ulcers, Crohn disease, ulcerative colitis)
 Severe cardiopulmonary disease
 Pain intolerance to implantable devices
 Alcohol and/or drug addiction
 Severe cognitive disabilities
 Allergy to silicone

13. Complications Associated With Bariatric
Surgery
Adjustable gastric band Malabsorptive Potential complications
procedures of both types of
procedures
Gastric mucosal erosion Bowel obstruction Hemorrhage
around the band Wound dehiscence Dumping syndrome (more
Gastritis Leakage and/or ulcers at common in gastric bypass)
Erosion of gastric mucosa the sites of anastomosis Postoperative respiratory
under the band, causing Nutritional deficiency insufficiency
perforation Incisional hernia Deep vein
Filling port malfunction Gastrojejunostomy thromboembolism
Gastric prolapse stenosis Pulmonary embolism
Malposition of the band Sepsis
Barrett esophagus
Dysphagia
Gastroesophageal reflux

14. Medical Therapy for Obesity
 Indicated if BMI of ≥30 kg/m2 or a BMI
from 27 and 29.9 kg/m2 with obesity-related
co morbid disease.
 Phentermine - sympathomimetic agent
similar to amphetamine
 Causes anorexia
 Side effects: pulmonary hypertension with
valvular heart disease.
 Precaution: a) poor risk benefit ratio
b) use only for short term

15. Sibutramine
Inhibits the reuptake of norepinephrine,
serotonin, and dopamine
Anorexia & increase satiety
Side effects – a) dry mouth
b) insomnia
c) constipation
d) Increase in BP & HR

16. Orlistat
 Lipase inhibitor in the GI tract.
Inhibits fat absorption in intestine.
 Side effects:
a) fecal urgency,
b) diarrhea,
c) abdominal pain,
d)liver injury.
 Precaution: Interfere with absorption of fat
soluble vitamins, so requires
supplementation of the same.

17. Anaesthesia Management
Pre operative evaluation
Goal of the preoperative assessment is
treatment and optimization of co morbid
conditions such as hypertension, CAD,
diabetes, venous thromboembolism,
and/or obstructive sleep apnea.
 Thorough history and physical
examination, vital signs, baseline
laboratory studies, and informed consent
should be obtained during the initial
assessment.

18. Obesity Surgery–Mortality Risk Score
 The Obesity Surgery–Mortality Risk Score to predict the risk of mortality
in patients undergoing bariatric surgery.
One point is assigned to each of 5 preoperative variables:
1. BMI 50 kg/m2 or more
2. Male gender
3. Hypertension
4. Risk for pulmonary embolism (history of venous thromboembolism,
pulmonary hypertension, and/or obesity hypoventilation)
5. Older than 45 years
Score Category Mortality
0 or 1 A or Low Risk 0.2%
2 or 3 B or Intermediate risk 1.3%
4 or 5 C or High risk 2.4%

19. Interaction between Obesity, Systemic
hypertension and Ischemic heart disease

20. Cardiovascular system evaluation
 H/O dyspnea,orthopnea or PND, limitation
in exercise in
tolerance, palpitations.
 Look for prior MI,HTN,Angina, PVD
 Signs of cardiac failure
1. Raised JVP
2. S3, S4
3. Pulmonary crackles
4. Hepatomegaly
5. Peripheral edema

21. Cont..
 Functional capacity can be better assessed
according to the patient’s ability to
undertake activities of daily living.
 Those able to perform activities requiring
at least 4 metabolic equivalents (METs),
e.g. climbing a flight of stairs, walking
up-hill or walking on level ground at 4
miles per hour, are classified as having
moderate functional capacity.

22. Cont..
 Measure non invasive BP with proper
sized cuff
 Cuff size should be greater than 20% of
upper diameter
 If cuff is small measured BP will be
spuriously high
 In morbidly obese invasive BP monitoring
is advised

23.  In CXR look for LVH/RVH/lung
disease/prominent pulmonary artery
 ECG – Look for rate, rhythm &
ischemic changes.
 Low voltage ECG may be recorded
because of fat.
 To rule out CAD an exercise or
dobutamine stress echo should be
done

24. Cont..
More prone to arrhythmia’s because of
 Hypoxemia
 Fatty infiltration of cardiac conduction
system.
 Sleep apnea
 Dyslipidemia
 Glucose intolerance

25. Pulmonary hypertension
Implications to Anaesthesia
 Hypoxemia should be avoided because it
causes pulmonary vasoconstriction further
aggravating the condition
 N2O should be avoided
 Inhalational agents are beneficial as they
cause bronco dilation & decrease hypoxic
pulmonary vasoconstriction
 In severe pulm HTN – Pulmonary Artery
catherization is useful for monitoring.

26. Thromboprophylaxis
 Deep vein thrombosis is the most common
postoperative complication of bariatric surgery
 So, adequate thromboprophylactic measures are
therefore imperative
 Patients at risk of post operative venous
thromboembolism should be considered for an
IVC filter before bariatric surgery
 Pneumatic compressive device can be used
 Heparin 5000 IU S C before surgery followed
every 12 hrly till patient is mobilized
 LMWH 40 mg every 12 hrly till patient is
mobilized
 Early ambulation

27. Pneumatic compression devices

28. Respiratory system changes
 Increased basal oxygen consumption and
carbon dioxide production.
Results in
i. lung & chest wall compliance atelectasis,
ii. airways resistance V/P mismatch
and impaired
iii. FRC oxygenation
 Supine position, induction of anaesthesia
and pneumoperitoneum aggravate these
effects.

29. Cont..
 There is restrictive lung disease because
1. Decreased chest wall compliance
2. Diaphragm pushed cephalad
3. Decreased lung volume
4. Supine and trendelenberg position
Lung volume changes
 TV - Normal or decreased
 IRV - decreased
 ERV - decreased greatly
 FRC - decreased greatly
 FEV1 - normal or decreased

30. Obstructive sleep apnea
 5% obese patients have OSA
 Take a history of snoring and subsequent
apnea(ask relative or sleeping partner)
 Ask for day time somnolence
 History of dry mouth and short arousal
during sleep
 Diagnosis confirmed with a
polysomnographic study

31. Respiratory system changes & OSA
Implications for anaesthesia
 As oxygen reserve is reduced, they desaturate rapidly
when apneic therefore should be well pre oxygenated
before intubation.
 Higher inflation pressure needed because of decreased
chest wall compliance
 Application of PEEP to improve oxygenation
 Patient should be trained with CPAP or BIPAP
machine preoperatively
 PFT should be done to anticipate need for post
operative ventilation
 Avoid sedative premedication
 Since these patients are hypoxemic and hypercapnic
ABG should be done preoperatively

32. GI changes & its implications
 Increased abdominal pressure
 Increased gastro esophageal reflux
 Hiatal hernia may be associated.
 After 8 hours of fast 85%-90% morbidly obese patients have
gastric volume greater than 25 ml and gastric ph less than 2.5
Hence Metaclopromide,Rantidine should be given.
 Increased risk of aspiration
 Diabetics are at risk for gastroparesis.
 Need a rapid sequence intubation technique after adequate
pre-oxygenation.
 There may be non alcoholic fatty liver disease, So many
bariatric surgeon prefer to take liver biopsy during surgery to
stage liver disease

33. Airway Management
 Airway examination should be done to predict
difficult intubation
 Predictors of difficult intubation
1. Mallampatti score of 3 or more
2. Neck circumference > 40 cm at thyroid cartilage.
3. Thyromental distance <6 cm
4. High BMI
5. Decreased incisor gap
6. Sternal pad of fat
7. Limited mobility of TM joint or AO joint
8. Short thick neck
9. Large breasts

34. Cont..
 Use oropharyngeal airway during mask
ventilation as airway collapses as soon as
consciousness is lost.
 If airway management and intubation prove
difficult, emergency airway adjuncts, including a
gum elastic bougie, laryngeal mask airway, video
laryngoscope, or fiber optic endoscope, may be
used
 Tracheasotomy kit should be available & surgeon
should stand by
 Breath sounds are distant therefore EtCo2 should
be used to confirm tracheal placement of ET tube

35. Cont..
 Intravenous & intraarterial access should
be checked.
 Central venous catheter should be used
 The conical shape of the upper arm may
present difficulties in obtaining an
accurate noninvasive blood pressure
reading, and invasive monitoring may be
deemed necessary.

36. Concurrent and Preoperative
Medications
 Usual medications, except insulin and oral
hypoglycemics, be continued until the time
of surgery.
 Medications for IHD & HTN should be
continued.
 Antibiotic prophylaxis is important because
of increased risk of postoperative wound
infection.
 Anxiolysis, analgesia, and prophylaxis
against both aspiration pneumonitis and
DVT should be addressed during
premedication

37. Baseline investigations
 Full blood count,
 Electrolyte profile
 RFT & LFT
 Thyroid function tests.
 HbA1c, FBS,PPBS
 PT/PTT
 Lipid profile
 Cortisol levels
 Blood Urea, Sr.Creatinine

38. Intraoperative Anesthetic
Management.
 Major areas of concern include
1. Airway management,
2. Maintenance of oxygenation,
3. Patient positioning
4. Monitoring.
5. Pneumoperitonium
6. Maintenance of Anaesthesia

39. Prevent hypoxemia during
induction
 HOB elevated
(back-up Fowler
May
or reverse Trendelenburg) 30° increase
 Use of CPAP during induction the safe
apnea period
 Preoxygenate with 100% O2 during
induction

40. Position for intubation
• Supine sniffing
position with 30°
back-up position
provides optimal
conditions for
successful
intubation.
• Aligning the
external auditory
meatus with the
sternum horizontally
has been shown to
improve the
laryngoscopic view

42. Positioning
 2 OT tables can be kept side by side if body
weight is more than 150kgs
 All pressure points should be padded
properly.
 Patients are prone to slipping off the
operating table during table position
changes; therefore, they should be well
strapped to the operating table
 Bean bags are soft pads available in various
sizes and shapes that are filled with
thousands of tiny plastic beads

43. Cont..
 When compared with the supine position, the
use of a 30° reverse Trendelenburg position
during bariatric surgery
 Advantages from RTP
1)Reduces the alveolar to-arterial oxygen
difference,
2)Increases total ventilatory compliance,
3)Reduces peak airway pressures,
4)Increases oxygenation.
 RTP is a better solution than large tidal
volume and high PEEP.

44. Intra Operative Ventilatory
Management
 Prevent/reverse atelectasis
Restrict the use of Fio2 to < 0.8 during
 Maintain lung recruitment
Use PEEP (10-12 cm/H2O)
 Avoid lung overdistension
Use tidal volume of 6-10 mL/kg of ideal
body weight
Keep peak-inspiratory pressure < 30
cm/H2O
Consider mild permissive hypercapnia if
necessary

45. Fluid Management
 Patients ,may have hypovolemia due to bowel preparation
and preoperative fasting. In addition, obese patients are
frequently receiving antihypertensive medications that
increase the potential for hypotension during induction.
 This potential, coupled with the propensity for postoperative
acute renal failure, highlights the importance of fluid
replacement.
 Intra-operative ventricular dysfunction may be precipitated
by rapid fluid administration in patients with IHD.
 Early detection of ischemia and aggressive management of
hypotension with intravenous fluids and vasopressors is
important as these patients frequently have minimal reserve.
 Central venous pressure monitoring is more reliable and
should be used to guide fluid management in
patients with ischemic heart disease or cardiac failure

46. Monitoring
 ECG, Pulse oximetry,Temperature, Capnography,
 Urine Output, BIS, Neuro Muscular monitoring
 Transesophageal echo &Invasive arterial monitoring
should be used for the super morbidly obese
 Blood pressure measurements can be falsely increased
if a cuff too small for the arm
 PA catheters are reserved for serious cardiopulmonary
disease.
 Central venous pressure monitoring is
more reliable and should be used to guide fluid
management in patients with ischemic heart disease or
cardiac failure.

47. Extubation
 Extubation in morbid obesity carries serious risk of
loss of airway control, rapid onset of hypoxaemia,
haemodynamic instability and pulmonary aspiration
 Should be done in semi-upright or sitting position,
 When fully awake,
 After complete resolution of neuromuscular blockade.
(evidenced by neuro-muscular stimulation, return of
airway reflexes, sustained head lift for >5 s and
generation of adequate peak inspiratory pressure and
vital capacity).
 Emergency airway equipment should be immediately
available in case re-intubation is required

48. Pharmacology
 Highly lipophilic drugs, show significant
increases in volume of distribution (VD)
for obese individuals relative to normal-
weight individuals
 Less-lipophilic compounds have little or
no change in VD with obesity
 Weak or moderate lipophilicity drugs can
be dosed on the basis of ideal body weight
(IBW) or, more accurately, lean body
mass (LBM)

49. Drug Dose recommendation
Propofol Induction dose based on LBW;
maintenance Increased fat mass does not
affect initial
dose based on TBW
Thiopental Induction dose based on TBW
Succinylcholine Intubating dose based on TBW
ND muscle relaxants All doses based on IBW
Fentanyl Loading dose based on TBW;
maintenance Increased distribution
volume and elimination
dose based on LBW and response
Dexmedetomidine Infusion rates of 0.2 μg/kg/min

50.  Desflurane has been suggested as the inhaled anesthetic of
choice in this patient population because of its more rapid and
consistent recovery profile
 Rapid elimination and analgesic properties make nitrous
oxide a good inhaled choice during bariatric surgery, but high
oxygen demand in the obese limits its use.
 But TIVA is preferred over inhalational agents because can
diffuse into the fatty tissue & delayed recovery can happen.
 Studies show TIVA has advatages like
1. Better intraoperative hemodynamic stability
2. Early recovery from GA
3. Better postoperative analgesia.
 Short acting agents like Remifentanyl,Propofol & dexmed
can be used.

51. In Our Institution?
 Two Bariatric Surgeries are conducted. They are
1. Sleeve gasrectomy
2. RYGB
 In Sleeve gasrectomy we insert gastric calibration tube, so
that surgeon cuts the stomach along that tube& gastric pouch
can be sized properly.
 We must remove all NG tubes before gastric division to avoid
unplanned stapling & transection of these devices.
 Later leak test is performed with 50ml methelene blue with
saline to ensure anastomotic integrity. At this time the cuff
should be tight seal otherwise aspiration of dye can occur
leading to chemical pneumonitits.
 After anastomosis, if NG tube is inserted it should be done by
watching on monitor otherwise disruption of anastomosis can
occur.

52. RYGB
 In bypass procedure metallic anastomotic device
Orovil is introduced. It has metallic part which is
attached to a plastic tubing.
 During insertion metallic portion should be
guided into esophagus with the help of index
finger & followed in the pharynx as deep as
possible.
 Problems that may be encountered is that metallic
part may get detached from the plastic tubing. In
that case direct laryngoscopy is done, if its visible
in pharynx it should be removed. If its deep then it
should be removed endoscopically.

53. Regional Anaesthesia
 Mainly for post operative pain management
 Combined Epidural & general anaesthesia can be
given to decrease the doses of GA drugs.
 Epidural anaesthesia may decrease the post
operative pulmonary complications
 Technically more difficult
 Fatty infiltration of the epidural space, as well
as increased blood volume caused by the increased
intra-abdominal pressure, may reduce the volume
of the epidural space, resulting in an unpredictable
spread of the anesthetic solution and block height.

54. Post operative management
 Initial post-operative considerations
include airway and respiratory support, pain
control and prevention of thromboembolism.
 Risk of post operative respiratory failure is
increased by
1. Preoperative hypoxemia
2. Vertical incision
 Postoperatively, supplemental humidified oxygen
should be administered at an appropriate inspiratory
fraction.

55. Cont..
 Postoperative incentive spirometry and/or
continuous positive airway pressure
(CPAP) may facilitate am earlier return to
preoperative pulmonary function and
decrease respiratory complications.
 Patients receiving continuous positive
airway pressure or bilevel positive
airway pressure preoperatively should
receive it immediately postoperatively

56. Management of postoperative pain
 Is very challenging.
 Morbidly obese patients have exaggerated respiratory
depression from opioids.
 In patients with obstructive sleep apnea – opioid sparing
techniques help avoid respiratory complications.
 A multimodal approach is best. It include
1)Intravenous opioid administration ,
2)Local anesthetics injected into the wound or port site,
3)Neuraxial anesthesia,
4)NSAIDs
 Infusion of dexmedetomidine decreases postoperative opioid
requirements.
 Recent technique is the continuous intraperitoneal infusion of
bupivacaine.

57. Laproscopy & anaesthesia
 Carbon dioxide is used to create pneumoperitonium.
 Systemic vascular resistance is increased with increased intraabdominal
pressure (IAP)
 The degree of IAP determines its effects on venous return and myocardial
performance
 There is a biphasic cardiovascular response to increases in IAP.
 At an IAP <10 mm Hg, there is an increase in venous return, with a
subsequent increase in cardiac output and arterial pressure.
 At an IAP >20 mm Hg, Compression of the inferior vena cava occurs with
decreased venous return from the lower body and consequent decreased
cardiac output . Decrease renal blood flow and GFR also occurs
 Cephalad displacement of the diaphragm and carina from
pneumoperitoneum may displace endotracheal tube into a bronchial
mainstem causing Endobronchial intubation reflected by hypercarbia and
hypoxemia
 Catastrophic complications that should be kept in mind include massive
gas embolism, pneumothorax, and mediastinal emphysema

58. Postoperative Complications
 Anastomotic Leak
 Respiratory (i.e. atelectasis,pneumonia)
 Vascular (thrombophlebitis, deep venous
thrombosis)
 Wound(infection, dehiscence)
 Rhabdomyolysis may occur in morbidly
obese patients after prolonged surgeries.
Suspected if unexplained increases of serum
creatinine and creatine phosphokinase and
patients complain of buttock, hip or shoulder
pain.

59. Patients scheduled for repeat bariatric surgery or
any surgery with previous history of bariatric
surgery.
 These patients have long-term nutritional
abnormalities like vitamin B12, iron, calcium, and
folate deficiencies and hypoproteinemia.
 Electrolyte and coagulation indices should be checked
before surgery, particularly if patient compliance has
been poor or if the patient is acutely ill.
 prothrombin time with partial thromboplastin time
will be abnormal because of deficiency of clotting
factors II, VII, IX, and X.
 So administration of a vitamin K analog, such as
phytonadione, can be used to correct the coagulopathy
within 6–24 h.
 Fresh frozen plasma will be required for emergency
surgery or active bleeding

60. Conclusion
 The number of patients resorting to bariatric
surgery for sustained weight loss is
increasing exponentially.
 These patients are at increased risk of peri-
operative complications by the presence of
obesity related co-morbidities.
 Preoperative identification and optimization
of associated disease in conjunction with
perioperative management by a
multidisciplinary team is essential to
optimize patient outcome.