Dr.N.BalasubramaniDr.N.Balasubramaniyamyam

Consultant AnaesthetistConsultant Anaesthetist

S.K.S HospitalS.K.S Hospital

SalemSalem

OBESITY,CHALLENGES IN OBESITY,CHALLENGES IN DAILY LIFEDAILY LIFE

Discussion….Discussion….

"Overweight" is a "Overweight" is a sensitivesensitive topic. topic.

Body mass index (BMI) levels that Body mass index (BMI) levels that categorize fatness. categorize fatness.

BMI can potentially BMI can potentially misclassifymisclassify people as fatpeople as fat

‘‘Trust your own judgementTrust your own judgement about your body about your body ! !

because because

BMIBMI-based body descriptions can be wrong’.-based body descriptions can be wrong’.

_ _ by Steven B. by Steven B.

HallMD HallMD

For AdultsFor Adults ““Overweight“Overweight“ BMI of 25 & above BMI of 25 & above ““OBESE”OBESE” BMI of 30 & moreBMI of 30 & more

- CDC & WHO- CDC & WHO

CHILDREN CHILDREN

overweightoverweight

BMI >85th percentileBMI >85th percentile

ObeseObese

BMI>95BMI>95thth percentile percentile

BMI Classification

<25 Normal 25-30 Overweight >30 Obese >35 Morbidly obese >55 Super-morbidly obese

Body Weight Body Weight CalculationsCalculations

Types of Fat distirbutionTypes of Fat distirbution

Gynaecoid Type- fat distributed in peripheral

sites (arms, legs, and buttocks)

Android Type- central fat distribution (intraperitoneal fat)

Waist-to-hip ratio

>0.8 in women

or

1.0 in men is typical of the android distribution

Android distribution

“Risk of metabolic and cardiovascular

complications”

- intra abdominal surgery more difficult and is associated with increased fat deposition around the neck and airway

Waist or collar circumference

More predictive of cardiorespiratory comorbidity

than BMI !!!

Effects of Fat distribution

Comorbidity Hypertension Dyslipidaemia Ischaemic heart disease Diabetes mellitus Osteoarthritis Liver disease Asthma Obstructive sleep apnoea (OSA)

Respiratory SystemRespiratory System OSA Episodes of apnoea or hypopnoea during sleep

secondary to pharyngeal collapse Five or more per hour or >30 per night snoring; day-time somnolence, associated with

impaired concentration and morning headaches

OSA…OSA…

Pathophysiological changes:

Hypoxaemia (leading to secondary

polycythaemia) Hypercapnia Systemic vasoconstriction, & Pulmonary vasoconstriction (right ventricular failure)

OSA & & Airway Adipose tissue in the pharyngeal wall

increased

pharyngeal wall compliance increased (airway collapse during negative pressure) Airway geometry (Antero-posterior axis is more than lateral) Genioglossus tone increased (less effective in maintaining airway patency) Increased reliance on hypoxic drive -type 2 respiratory failure

Obesity Hypoventilation syndrome

Relative leptin insensitivity in obesity decreases ventilatory response to Co2

Depressant drugs, including many anaesthetic agents and analgesics, accentuate this

Cardiovascular SystemCardiovascular System Blood volume, cardiac output, ventricular workload,

oxygen consumption, and CO2 production are all increased

Absolute blood volume is increased-45 ml kg-1 'Obesity cardiomyopathy‘ arrhythmias because of: myocardial hypertrophy and

hypoxaemia; hypokalaemia from diuretic therapy; coronary artery disease; increased circulating catecholamines; OSA (sinus tachycardia and bradycardia); and fatty infiltration of the conducting and pacing systems.

Ischaemic heart disease is more prevalent

PharmacokineticsPharmacokinetics

Calculation of appropriate dosages Calculation of appropriate dosages may be difficultmay be difficult

Most of the general anaesthetic Most of the general anaesthetic drugs are affected by the mass of drugs are affected by the mass of Adipose tissueAdipose tissue

Pharmacokinetics of Pharmacokinetics of obesityobesity

The main factors that affect tissue The main factors that affect tissue drug distribution in any patient aredrug distribution in any patient are

plasma protein bindingplasma protein binding

body composition and body composition and

regional blood flow.regional blood flow.

Highly fat-soluble drugs - increased volume distribution

e.g. benzodiazepines and barbiturates – have prolonged effect

Less fat-soluble drugs-No change in volume distribution

e.g. neuromuscular blocking agents

Exception is succinylcholine & Propofol- Should be dosed toTotal body weight

Reduce 25% of spinal & epidural dose

Preoperative Assessment

Many morbidly obese patients have limited mobility and may therefore appear relatively asymptomatic!!!

despite having significant cardio-respiratory

dysfunction

Drug history, Look for Symptoms and signs of cardiac

failure OSA Unable to lie flat for Several years So an

assessment of the ability to tolerate the supine position may reveal unexpected profound oxygen desaturation, airway obstruction, or respiratory embarrassment

IV access by central venous cannulation

Ottestad E et al. Anesth Analg 2006;102:1293-1294

©2006 by Lippincott Williams & Wilkins

A chest radiograph obtained after placement of the 20-cm double-lumen subclavian catheter.

Ottestad E et al. Anesth Analg 2006;102:1293-1294

©2006 by Lippincott Williams & Wilkins

Preoperative Airway Preoperative Airway AssesmentAssesment

   

  Predictors of difficult Predictors of difficult airway  airway 

  BMI  BMI  Mallampati classification  Mallampati classification  Neck circumference  Neck circumference  Thyromental distance  Thyromental distance  Obstructive sleep Obstructive sleep

apnoea symptomsapnoea symptoms Gastro-oesophageal reflux diseaseGastro-oesophageal reflux disease Cervical fat pad or humpCervical fat pad or hump

PositioningPositioning

Ramped or semi sitting positionRamped or semi sitting position Head-Elevated Laryngoscopy Head-Elevated Laryngoscopy

Position (HELP) Position (HELP)

Positioning….Positioning….

Proper head-elevatedlaryngoscopy position (HELP

Positioning…..Positioning…..

Intra-OperativeIntra-Operative Pulmonary atelectasis occurs in 85%- Pulmonary atelectasis occurs in 85%-

90% of healthy adults within minutes 90% of healthy adults within minutes after the induction of general anesthesiaafter the induction of general anesthesia

Atelectasis is larger in obese patients or Atelectasis is larger in obese patients or when a high fraction of inspired oxygen when a high fraction of inspired oxygen (FiO2) is used(FiO2) is used

Degree of head-up tilt may slow the rapid desaturation

Awake fibreoptic intubation PEEP short-acting anaesthetic agents

Post-OperativePost-Operative Extubated wide-awake in the sitting position CPAP Post-operative ventilation-Awake& Less sedation

with PS mode NSAIDs- best omitted Acetaminophen, Patient-controlled opioid

analgesia, or regional anaesthesia Early mobilization -reduces postoperative atelectasis

& venous thromboembolism.

Catabolic response to surgery use Insulin to maintain normoglycemia

Keypoints..Keypoints..

Obesity-independent risk factorObesity-independent risk factor Plasminogen activator inhibitor-1 Gastric emptying is delayed Rhabdomyolysis Difficulty of laryngoscopy The 400 J of energy on regular

defibrillators

Take Home…Take Home…

Proper PositioningProper Positioning Early ExtubationEarly Extubation DVT prophylaxis – during peri DVT prophylaxis – during peri

operative periodoperative period

Effective postoprative analgesiaEffective postoprative analgesia