obesity & anaesthesia

OBESITY & ANAESTHESIA

Co-ordinator – Dr. Chavi Sethi(MD)Speaker – Dr. Uday Pratap Singh

OBESITY

LATIN WORD OBESUS, WHICH MEANS FATTENED BY EATING

OBESITY: Metabolic disease in which adipose tissue comprises a greater then normal proportion of body tissue and amount of fat tissue is increased beyond a point compatible with physical and mental health and normal life expectancy.

Over wt.: excess of total body wt. including all components(muscle, bone, water and fat)

Ideal body wt. ( in Kg): also k/w as Broca,s index Height in cm- 100 for males(105 for females)

Relative wt. : Ratio of actual and ideal wt.

Body mass index(BMI): also k/w as Quetelet index Body wt.(in Kg)/ Height(met2)

Ponderal index Ponderal index = height in cm divided by cube root of body weight in kg

Corpulence index: Actual wt/ desire wt. normaly less then 1.2

Harpedence index: normally less then 40 in female and less then 50 in male.

CLASSIFICATION OF OBESITY

BMI STATUS

< 18.5 underweight

18.5–24.9 normal weight

25.0–29.9 overweight

30.0–34.9 class I obesity(Obese)

35.0–39.9 class II obesity (Morbidly obese)

≥ 40.0 class III obesity(Super morbidly obese)

OBESITY & HEALTH RISKS

HEALTH RISKS

DEGREE OF OBESITY

ABDOMENAL FAT DISTRIBUTION

MALE WAIST ≥ 102cm

FEMALE WAIST ≥ 88cm

CLINICAL MANIFESTATION

1.Pulmonary2.C.V.S3.G.I.T4.Hepatic5.Metabolic

PULMONARY MANIFESTATIONS

•Lung compliance may normal

DEC. CHEST WALL COMPLIANCE

•Abdominal fat--cephalad shift of diaphragm

RESTRICTIVE LUNG DISEASE

•Supine & Trendelenburg

•anaesthesia

DEC. FRC

•If FRC < CC

•V/Q mismatch; R-L shunt; arterial hypoxemia and hypercarbia.

ALVEOLAR ATELECTASIS

OBESITY & ALVEOLAR COLLAPSE

•Inc. metabolic rate– inc. Body wt.

•Inc. O 2 demand

•Inc. CO 2 production

INC. ALVEOLAR VENTILATION

•Alert to impending complications

HYPOXIA & HYPERCARBIA

•Pickwickian synd.•Hypoxia &

hypercapnia•Polycythemi

a– cyanosis•Rt. Sided

heart failure•somnolence

OBESITY HYPOVENTILATION

SYND.

OBSTRSUCTIVE SLEEP APNEA SYNDROME

• Frequent episodes of apnea or hypopnea during sleepTotal cessation of airflow for = 10 sec.Hypoapnea is 50% reduction in airflow5 or more episode per hr. or 30 per night are counted as

clinically significant

• Day time somnolence associated with memory problem , impaired conc. and accident

• Throat muscles become so relaxed and floppy during sleep that they cause a narrowing or complete blockage of the airway

SYPMTOMS OF OSAS

Daytime sleepiness or fatigueDry mouth or sore throat upon awakeningHeadaches in the morningTrouble concentrating, forgetfulness,

depression, or irritabilityNight sweats

Restlessness during sleepSexual dysfunctionSnoringSudden awakenings with a sensation

of gasping or chokingDifficulty getting up in the mornings

Perioperative complications of OSAS

Hypertention Hypoxia

Myocardial infarction Arrhythmias

Pulmonary edema Stroke

Difficult intubation--induction

Upper airway obstruction--recovery

GASTROINTESTINAL MANIFESTATIONS

HITUS HERNIA

GASTROESOPHAGEAL REFLUX

POOR GASTRIC EMPTYING

HYPERACIDIC GASTRIC FLUID

INC. RISK OF GASTRIC CANCER

HEPATOBILIARY MANIFESTATIONS

HEPATIC• Fatty infiltration of liver• Abnormal liver function• Volatile anaesthetics defluorinated to

greater extent-halothane hepatitis

GALL STONES• Abnormal cholesterol metabolism

CARDIOVASCULAR MANIFETATIONS

• To perfuse Additional body fat

INC. BLOOD VOL

INC. STROKE VOL

• 0.1 ml / min / kG body fat

INC. CARDIAC OUT PUT

ARTERIAL HTN

INC. CARDIAC WORKLOAD

LT VENTRICULAR HYPERTROPHY

PULMONARY HTN & COR PULMONALE

• INC. Pulmonary blood flow• Pulmonary vasoconstriction• Persistent hypoxia

Cardiac manifestations of obesity

LVH

RVH

THROMBO-EMBOLIC DISEASE:

• Inc risk of DVT• Inc. intra-abdominal pressure• Polycythemia• Inc. pressure in deep veins• Immobilization-venous stasis

METABOLIC DYSFUNCTIONS

TYPE-2 DM• Inc resistance to insulin in periphery

HYPERTENTION

CORONARY ARTERY DISEASE

CHOLILITHIASIS• Abnormal cholesterol metabolism

HYPERCHOLESTEROLEMIA

HYPERINSULINEMIA• Inc. sympathetic activation

Body Water

• Reduction in total body water to 40% of TBW.• Relative dehydration may be present.• Poor tolerance to fluid load.

METABOLIC SYNDROME

METABOLIC SYND

OBESITY

HTNTYPE-2 DM

Clinical Criteria for Diagnosing Metabolic Syndrome *

Criteria Defining Value

Abdominal obesity Waist circumference >102 cm in men and >88 cm in women

Triglycerides ≥150 mg/dL

High-density lipoprotein cholesterol <40 mg/dL in men and <50 mg/dL in women

Blood pressure ≥130/85 mm Hg

Fasting glucose≥110 mg/dL

*Three of five criteria must be met.

OBESITY & DRUGS DOSES

LIPID SOLUBLE

1. Inc. vol of distribution2. Larger loading doses to

produce same plasma concentration but maintenance doses less frequent-slow clearance

3. Doses based on actual body wt.

WATER SOLUBLE

1. Limited vol of distribution

2. Doses not influenced by fat stores

3. Doses based on ideal body wt. – to avoid overdosing.

• Commonly used anesthetic drugs can be dosed according to total-body weight (TBW) or IBW based on lipid solubility.

• Lean body mass is a good weight approximation to use when dosing hydrophilic medications. As expected, the volume of distribution is changed in obese patients with regard to lipophilic drugs.

• Three exceptions to this rule are digoxin, procainamide, and remifentanil, highly lipophilic, have no relationship between properties of the drug and their volume of distribution.

• Consequently, dosing of commonly used anesthetic drugs such as propofol, vecuronium, rocuronium, and remifentanil is based on IBW.

• In contrast, thiopental, midazolam, succinylcholine, atracurium, cisatracurium, fentanyl, and sufentanil should be dosed on the basis of TBW.

• maintenance doses of propofol should be based on TBW. Conversely, based on real body weight, smaller amounts of propofol are needed to anesthetize the patient.

Halogenated anaesthetics:

• Morbidly obese pt. Metabolize halothane and enflurane more resulting in high serum and urine level or fluoride.

• Isoflurane and desflurane are volatile agent of choice bc it produces lower fluoride conc.

• Liver and body fat store inhalational anaesthatics long after completion of surgery bt drug conc. In brain and lungs decrease rapidly.

Pharmakinetics

• Alternation in drug binding, distribution, and elimination of many anesthetic drugs.

• Dose calculation based on IBW rather than TBW.

• IBW calculated as : Men = 49.9 Kg + 0.89 kg/cm above 152.4 cm WoMen = 45.4 Kg + 0.89 kg/cm above 152.4 cm

ANAESTHETIC CONSIDERATIONS

PREOPERATIVE

INTRAOPERATIVE

POSTOPERATIVE

PREOPERATIVE

HISTORY

• Duration of obesity & associated problems

• Previous operation & anaesthesia• Medication

INVESTIGATIONS• Blood • Urine • LFTs• RFTs• ECG• X-Ray chest• Echocardiography• ABGs

RISK FOR ASPIRATION PNEUMONIA• Premedication:• Anticholinergic agent

• H2-antagonist• Metoclopramide• Sodium citrate(oral antacid 30 ml of 0.3M)• LMWH subcutaneous(DVT prophylaxis)

AVOID RESPIRATORY DEPRESSANT• Pre-ops hypoxia & hypercapnia• OSA

IM- Injections…Unreliable

ASSESS CARDIOPULMONARY RESERVE

• History• Physical examination-(BP,Edema)• X-Ray chest• ECG• ABGs

IV & IA ACCESS

• Technical difficulties

REGIONAL ANAESTHESIA-DIFFICULTIES• Obscured landmarks• Difficult positioning• Extensive layers of adipose tissue

AIRWAY ASSESSMENT IN OBESE• Difficulty in mask ventilation• Difficult intubation--Consider FOB• Temporomandibular joint-limited mobility• Atlanto-ooccipital—limited mobility• Narrow upper airway• Distance b/w mandible & sternal fat pads-limited• Large breasts• Excessive palatal & Pharyngeal soft tissue.• Short and thick neck(if circumference >14cm then difficult

intubation)

INTRAOPERATIVE

GA• PRE-OXYGENATION• POSITIONING• INDUCTION & INTUBATION• MAINTAINACE

REGIONAL ANAESTHESIA• Technical difficulties• Doses of LA• Complications • Advantages

PREOXYGENATION

SLIGHTLY HEAD UP POSITION

NECESSARY BECAUSE• Dec FRC• FRC Dec more on lying • Supine• After induction

• Obese rapidly desaturate• Intubation may be difficult

OBESITY & V/Q MISMATCH

• Chest obesity• Inc intra-

abdominal pressure

DEC. FRC

• Supine position• Induction• Muscle

relaxation

ATELACTASIS FRC < CC • Rt to Lt shunt

• Rapid hypoxia

V/Q MISMATCH

POSITION IN INDUCTION & INTUBATION

PRE-OXYGENAT & INTUBATE IN SLIGHTLY HEAD UP POSITION

FOLDED BLANKETS PLACED UNDER UPPER BODY,NECK & HEAD• Sternal notch & external auditory meatus

are in line

POSITION FOR OXYGENATION & INTUBATION IN OBESE

INDUCTION & INTUBATION

DIFFICULT TO VENTILATE WITH MASK

RAPID SEQUENCE INTUBATION• Risk for aspiration

VAREITY OF SCOPES• Long blade & short handle

AWAKE INTUBATION-IF DIFFICULT• FOB

PEEP DURING INDUCTION

Application of positive end-expiratory pressure during the induction of general anesthesia:• prevents atelectasis formation.• improves oxygenation and probably

increases the margin of safety before intubation.

CONFIRMATION OF INTUBATION

DIFFICULT TO CONFIRM BY AUSCULTATION-CLINICALLY

CONFIRMED BY END TIDAL CO2

MAINTAINACE OF ANAESTHESIA

HIGH INSPIRED O2 CONCENTRATION

• LITHOTOMY,TRENDELENBURG & PRONE

CONTROLLED VENTILATION – HIGH TIDAL VOLUMES

PEEP-WORSEN PULMONARY HTN IN EXTREME OBESE

POSTOPERATIVE COSIDERATIONS

EXTUBATION• Delayed until effects of NMBAs completely

reversed• Fully awake• Adequate airway maintenance• Adequate tidal volume• Supplemental oxygenation• Modified sitting position

POSTOPERATIVE COMPLICATIONS

RESPIRATORY FAILURE• Major complication• Inc risk-

• Pre-ops hypoxia• Thoracic & upper abdominal Surgery

DEEP VENOUS THOROMBOSIS

PULMONARY EMBOLISM

WOUND INFECTION

THANK YOU

CPAP CIRCUIT

APPLICATION OF CPAP

DIFFICULT INTUBATION IN OBESE

ATELACTASIS IN OBESE

ATELECTASIS AFTER APPLYING PEEP BEFORE INTUBATION

MONITORING

INVASSIVE MONITORING—HAEMODYNAMIC INSTABILITY• CVP• INTRA-ARTERIL LINE• PULMONARY ARTERY CATHETER