Obesity and anaesthesia

Anaesthetic consideration in morbidly obese in
non-bariatric surgery
DR. FIROZ KHAN
DR. MEERA
DEPARTMENT OF ANAESTHESIOLOGY

DEFINITION
IDEAL BODY WEIGHT
• Formen: IBW(kg)=height (cm)–100 Forwomen: IBW(kg)=
height (cm)–105
• OVER WEIGHT : Anexcess of total body weight
• OBESITY :Body weight >20% of IBW
• MORBID OBESITY : Body weight > twice IBW or IBW + 50

OBESITY AND ASSOCIATED RISKS ACCORDING TO BMI

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

RESPIRATORY SYSTEM
• Theoverallrespiratoryproblemisoneof restrictivelung
disease.
• Chestwall andlungcompliance↓ d/t accumulationoffat onthe
thoraxandabdomen.
• Decreasedpulmonarycomplianceleadsto ↓ ↓ ↓ FRC
(primarily a resultof↓ ERV,↓ VC& ↓ TLC).
• Underanesthesia,FRCofthe obesepatient decreasesabout
50%ascomparedto 20% reductionforthe non-obesepatient.

RESTRICTIVE LUNG DISEASE
INCREASED INCREASED PULMONARY
DECRESED RESPIRATORY MUSCLE BLOOD FLOW
FUNCTION
DECREASED CHEST WALL DECREASED LUNG
COMPLAINCE, INCREASED COMPLIANCE
ELASTIC RESISTANCE
DECREASED TOTAL RESPIRATORY COMPLAINCE
IN SUPINE POSITION ↓FRC, ↓VC, ↓TLC
Shallow& rapidbreathing FRC BELOWCC, Small airwayclosure
Increasedworkof breathing V/Qmismatchandlefttorightshunt
Limitedmaximumventilatory capacity arterialhypoxemia

GASTROINTESTINAL SYSTEM
• Prolonged Gastric Emptying time, Decreased Gastric pH,
• Increased chancesof HiatalHernia.
• Increased risk of AspirationPneumonitis.
• Inguinal hernia.

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

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

.
.
TheVD in obesepatients
is affected by
• reduced total bodywater,
• increased total bodyfat,
• increased lean body mass,
• Altered tissueprotein
binding,
• increased blood volume
& cardiacoutput,
• increased blood
concentrations of free
fatty acids, cholesterol,
and organomegaly.

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

PRE ANAESTHETIC 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 OSAin anobesepatient? Snoring or
apnea during sleep& apparent arousal. Extremity movement,
frequent turning in sleep Daytime sleepiness.
• Fatigue?

• Respiratorysystem:-
• smoking history,
• exercisetolerance,
• history ofhypoventilation
andsomnolence,
• Pulmonaryfunctiontestswith spirometry
• Polysomnography
• Sleepstudy
• Workofbreathing↑
• Max VoluntaryVenti↓

AIRWAY CHALLENGES
I. Airway obstruction with light tomoderate sedation
II. Difficult to maskventilate
III. Higherincidence of difficult intubation andfailed intubation in
MO.
IV. Presenceof hypopharyngealadipose tissue , interferes with
the line of sight (LOS)atdirect laryngoscopy.
V. Presenceof pre-tracheal adiposetissue, worsens the
laryngoscopic view.

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

Anteriornecksoft tissue:
Superior predictorof difficultintubation inobese patients than
obesity per seor athickneck.
• Obtained by ultrasound quantification of softtissue at the level of
the vocalcords,thyroid isthmusandsupra-sternalnotch.
• Averagedvalue>28mmpredictsdifficult laryngoscopy

AIRWAY EXAMINATION
• Mallampati classification
• Atlanto-occipital joint extension,
• Temporomandibular joint (TMJ)assessmentwith inter-incisor
distance,mentohyoid distance,and
• Dentition, largeprotuberant teeth,
• Limited neckmobility
• Retrognathia
• Neckcircumference,
• Hypertrophic tonsils andadenoids.

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

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

PREMEDICATION
• Nosedativesor narcoticsshould begivento amorbidly obese
patient aspremedication.
• Canbegivenin operating room alongwith supplementary oxygen
to prevent hypoxiafrom respiratory depression.
• glycopyrollate(0.4 mg),ananticholinergicused to dry the upper
airway,

1. Continue antihypertensive medication[ACE Inhibitors?].
2. Start prophylactic Antibiotic for woundinfection
3. Heparin prophylaxis againstDVT
4. H2receptor antagonist [proton pumpinhibitor].
5. Anti-aspiration prophylaxis
• Metoclopramide to increasegastricemptying, andnon
particulateantacids

MONITORING
• Pulseoximetry,
• Electrocardiogram,
• Noninvasivebloodpressure,
• End-tidal carbondioxide,
• Temperature,
• Hourly urineoutput
• Peripheralnervestimulator
• Bispectralindex(BIS)

POSITIONING
• Awakept. canself-position on ORtable.
• HELP[Stackedor Ramped]position from scapula to the head tobe
arranged.
• Paddingof all pressurepoint.
• Maintain & pre-oxygenateinhead-up position.
• pneumatic leggings orcompression stockingsto beapplied.

PREOXYGENATION
• Obesepatients initially be placed in aramped position andthen in
the reverse trendelenburg position beforepreoxygenation.
• Patientsare then preoxygenated for 3 to 5minutes with 100%
• oxygenunder positive pressure 8 to 10 cmH2o
• After induction, maintain 10to 12cmH2OPEEP, butcare must be
taken to treat anyhypotension thatmayoccur.

FACTORS RESPONSIBLE FOR DIFFICULT LARYNGOSCOPY
AND INTUBATION
• Fatface& cheeks.
• Largebreasts in females.
• Limited rangeof motion of head, neck,& jaw.
• Smallmouth & alargetongue.
• Excessivepalatal & pharyngealtissue.
• Short thick [large circumference]neck.
• High Mallampati scores[III orIV].
• O2 desaturation ismorerapid.

INTUBATION STRATEGY
• AwakeFOIshall beanideal technique but isnot easy to achieve.
• obscuredlandmark mayhinder nerveblock.
• Sedation& analgesicusedduring preparation may result in
hypercapnia,hypoxia& airwayobstruction.
• During difficult intubation, nerve blocksmay “unprotect”
theairway.

RSI
• RSIcould be contemplated using short acting inducing agentsas
propofol with succinylcholine,with thepatient positioned on a
ramp.

MAINTENANCE OF ANAESTHESIA
• Combinedepidural/general(GA)maybebeneficial to decreaseGA
requirements.
• Considera"balanced"GA>decreasesrequired doseof eachagent, so
lesswill be aroundpostop.
• Considerusingshortactingagents(e.g. alfentanyl, propofol,
versed,atracurium)
• avoidusinglongactingagents(e.g. morphine, valium, pancuronium)
• Ventilation:
• Uselarge tidal volumes15-20ml/kg ideal bodywt. Titrate PEEP
to maintain oxygensaturation.

PRE-REQUISITES FOR EXTUBATION
• Intact neurologic status, fully awakeand alert, with headlift
greater than 5s
• Hemodynamic stability
• Normothermia.
• Train-of-four (TOF)reversalby PNS(T4/T1 >0.9). Full reversalof NM
blocking agents.

• Respiratory rate (10 -30/min)
• SPO2>95%onFIO2 0.4
• AcceptableABG(FIO2of 0.4: pH- 7.35 to 7.45;
• PaO2,>80mm Hg;PaCO2,<50 mm Hg).
• Generating Tidal volume (TV)>5mL/kg ideal bodyweight

POST OP COMPLICATIONS
• Post-anesthetic hypoxemia
• Respiratorydepression
• Early ventilatory failure with needforreintubation
• Positional ventilatory collapse
• Hemodynamic instability,
• PONV
• Venousthromboembolism

REGIONAL ANAESTHESIA
• Under-utilized (PCAis>90%)in this patient population
• technical difficulties
• increasedincidence of epidural failure andcatheter dislodgment,
• decreasedepidural spaceform intra-abdominal pressurecausing
unpredictable spreadof local anaesthetics,variable blocklevel

• Forepidural catheter insertion ,patients shouldbe
positioned in asitting position, and ultrasonography
guidanceisrecommended.
• Forperipheral surgicalprocedures, peripheral
nerve blocksused,provided that adequate
landmarksexist.

AnOunceOf Prevention IsWorth APoundOf Cure
THANKYOU

Obesity and anaesthesia

More Related Content

What's hot (20)

Similar to Obesity and anaesthesia (20)

Recently uploaded (20)

Obesity and anaesthesia