obesity & anaesthesia
DESCRIPTION
anaesthetic consideration in obese patientsTRANSCRIPT
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