anaesthetic managent of bariatric surgery
TRANSCRIPT
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