Anesthesia for Bariatric Surgery

Guided by: Dr Vrishali Ankalwar

By: Dr Sneha Khobragade

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

Medical co-morbidities associated with obesity

1. Type II DM2. Hypertension3. Cardiovascular diseases4. OSA5. Liver & Gallbladder diseases6. Arthritis7. Colon and postmenopausal breast

cancer8. Affects quality of life issues

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%!

TYPES: classified on the basis of –• Waist circumference• Waist to hip ratio • Waist to height ratio Central-android

Obesity • Truncal distribution of fat• Increase risk of

cardiovascular diseases

Peripheral-gynecoid Obesity.

• Fat is prominent in hips, buttocks and thigh

• Less incidence of cardiovascular diseases

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 Increased18.5-24.9 Normal Least25-29.9 Overweight Increased30-34.9 Obesity (class I) High35-39.9 Obesity (class II) Very high>= 40 Morbid Obesity (class

III)Very high

>=50 Super obesity Extremely high

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)

WAIST CICUMFERENCE:

Waist circumference

BMI(Kg/m2)Normal weight

overweight

ObeseClass I

< 102 cm in males< 88 cm in females

Least risk

Increased risk

High risk

> 102 cm in males> 88 cm in females

Increasedrisk

High risk Very high risk

BARIATRIC SURGERY:

INDICATIONS : 1. BMI > 40 Kg/m2

2. BMI > 30 Kg/m2 and obesity related

co-morbidities not controlled by medical therapy

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

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

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

PATHOPHYSIOLOGY:

RESPIRATORY SYSTEM:

fat accumulation decrease chest wallmovement

decrease lung compliance

Increase elastic resistance & decrease pulmonary compliance

FRC, vital capacity, total lung capacity.

-shallow and rapid breathing-increases work of breathing-limited maximum ventilatory capacity

Arterial hypoxemia

Small airway closure

Unchanged

closing capacity

FRC

Low arterial oxygen tension as compared to

non obese

Chronic hypoxemia : >> polycythemia >> pulmonary hypertension >> cor pulmonale

Increase sympathetic

activity

OBESITY INDUCED HYPERTENSIONCARDIOVASCULAR SYSTEM

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.

DIASTOLIC DYSFUNCTION

SYSTOLIC DYSFUNCTION

OBESITY CARDIOMY

OPATHY

OBESITY CARDIOMYOPATHY:

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

BIVENTRICULAR FAILURE

HYPERCOAGUBALITY: releases bioactive mediators - abnormal lipids, - insulin resistance, - inflammation and - coagulopathies.

Increase fibrinogen, factor VII, factor VIII, & hypofibrinolysis

Additional factors includes: - increase fasting triglycerides factor VII, activated by postprandial lipemia

- insulin endothelial dysfunction von

willebrand factor & factor VIII predisposes

fibrin formation

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

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

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

subclinical hypothyroidism Increase renal blood flow

glomerular hyperfiltration

increases sympathetic & RAAS

increase in renal tubular reabsorption & impairs natriuresis

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

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

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.

f) Infantile type anterior laryngeal opening.

g) large breast in females.

h) neck circumference (>40 cm) – SINGLE POSITIVE PREDICTOR OF DIFFICULT INTUBATION

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.

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

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

FDA approved anti-obesity medication: PHENTARMINE

ORLISTAT

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

>> blocks absorption of dietary fat by inhibiting

lipases in GIT.

>> leads to weight loss, improvement in BP,

fasting glucose & lipid profile.

ORLISTAT (TETRAHYDROLIPSTATIN):

>> 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.)

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.

OBSTRUCTIVE SLEEP APNEA

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.

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

signs : witnessed episodes of apnea during sleep

BMI>=35 neck circumference >= 16 inch (40cm) hyperinsulinemia elevated glycosylated hemoglobin gold standard diagnostic test: overnight polysomnography

POLYSOMNOGRAPHY (PSG) : diagnosis of sleep

related disorders. - includes meaurement of 1. O2 saturation 2. Electrocardiography 3. Electroencephalography 4. Electromyography

5. Electrooculography

6. Nasal and oral airflow measurement – Thermocouple

7. Measurement of respiratory efforts

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

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

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.

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)

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

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)

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.

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.

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

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

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

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

IVC FILTERS

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

For maintenance dose, if clearance equal in obese & non obese , dose LBW increases with obesity, dose TBW

Drug Recommended dosingThiopentone TBWPropofol Induction: IBW; Maintenance: TBW

Fentanyl/Sufentanil TBWVecuronium/Rocuronium IBWAtracurium/ cisatracurium IBW

succinylcholine TBWBenzodiazepine IBWneostigmine TBWparacetamol IBWglycopyrolate IBW

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

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

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

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.

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

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

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.

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)

Dexmedetomedine (alpha2 agonist)-

sedative and analgesic properties with no effect on respiration

Vecuronium, rocuronium, atracurium are preferred NDMR.

Pneumoperitoneum: - <15mmhg - >20mmhg vena caval compression CO - cephalad displacement of diaphragm endobroncheal

intubation

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

FLUID MANAGEMENT: Blood loss is more larger incision to access

surgical site

Goal to maintain normovolemia Avoid rapid infusion of intravenous fluids.

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

VENTILATION Tidal volume <13ml/kg of IBW

Moderate PEEP =10cm H2O prevent postoperative atelectasis

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.

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

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

- early ambulation - deep breathing exercises

- incentive spirometry

- pulse oximetry and ABG monitoring

whenever required

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

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

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

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

- 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.

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

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.

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

maximum

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

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

Thank you