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Obesity & anaesthesia
Obesity presents unique challenges for anaesthesia. Obese patients have decreased lung volumes which increases the risk of hypoxemia during induction and intubation. Preoxygenation in a slightly head-up position can help reduce this risk. Intubation may be difficult due to obesity related anatomical changes. Regional anaesthesia can also be challenging due to obscured landmarks and extensive adipose tissue. Postoperatively, obese patients are at higher risk of respiratory failure, DVT, and wound infections requiring close monitoring. Careful consideration of dosing, positioning, and postoperative monitoring is needed to safely manage anaesthesia for obese patients.
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Obesity & anaesthesia
- 1. OBESITY & ANAESTHESIA Co-ordinator– Dr. Chavi Sethi(MD) Speaker – Dr. Uday Pratap Singh
- 2. 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.
- 3. Over wt.: excessof 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.
- 4. 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 ≥ 40.0 class II obesity (Morbidly obese) class III obesity(Super morbidly obese)
- 5. OBESITY & HEALTHRISKS HEALTH RISKS DEGREE OF OBESITY ABDOMENAL FAT DISTRIBUTION MALE WAIST ≥ 102cm FEMALE WAIST ≥ 88cm
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- 9. PULMONARY MANIFESTATIONS DEC. CHEST WALL COMPLIANCE RESTRICTIVE LUNGDISEASE DEC. FRC ALVEOLAR ATELECTASIS • Lung compliance may normal • Abdominal fat--cephalad shift of diaphragm • Supine & Trendelenburg • anaesthesia • If FRC < CC • V/Q mismatch; R-L shunt; arterial hypoxemia and hypercarbia.
- 12. INC. ALVEOLAR VENTILATION • Inc.metabolic rate– inc. Body wt. • Inc. O 2 demand • Inc. CO 2 production HYPOXIA & HYPERCARBIA • Alert to impending complications OBESITY HYPOVENTILATION SYND. • Pickwickian synd. • Hypoxia & hypercapnia • Polycythemia– cyanosis • Rt. Sided heart failure • somnolence
- 13. OBSTRSUCTIVE SLEEP APNEA SYNDROME •Frequent episodes of apnea or hypopnea during sleep Total cessation of airflow for = 10 sec. Hypoapnea is 50% reduction in airflow 5 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
- 14. • Throat muscles becomeso relaxed and floppy during sleep that they cause a narrowing or complete blockage of the airway
- 15. Daytime sleepiness orfatigue Dry mouth or sore throat upon awakening Headaches in the morning Trouble concentrating, forgetfulness, depression, or irritability Night sweats
- 16. Restlessness during sleep Sexualdysfunction Snoring Sudden awakenings with a sensation of gasping or choking Difficulty getting up in the mornings
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- 18. GASTROINTESTINAL MANIFESTATIONS HITUS HERNIA GASTROESOPHAGEAL REFLUX POORGASTRIC EMPTYING HYPERACIDIC GASTRIC FLUID INC. RISK OF GASTRIC CANCER
- 19. HEPATOBILIARY MANIFESTATIONS HEPATIC • Fatty infiltrationof liver • Abnormal liver function • Volatile anaesthetics defluorinated to greater extent-halothane hepatitis GALL STONES • Abnormal cholesterol metabolism
- 20. CARDIOVASCULAR MANIFETATIONS INC. BLOOD VOL •To perfuse Additional body fat INC. STROKE VOL INC. CARDIAC OUT PUT • 0.1 ml / min / kG body fat ARTERIAL HTN INC. CARDIAC WORKLOAD
- 21. LT VENTRICULAR HYPERTROPHY PULMONARYHTN & COR PULMONALE • INC. Pulmonary blood flow • Pulmonary vasoconstriction • Persistent hypoxia
- 22. Cardiac manifestations ofobesity LVH RVH
- 23. THROMBO-EMBOLIC DISEASE: • Incrisk of DVT • • • • Inc. intra-abdominal pressure Polycythemia Inc. pressure in deep veins Immobilization-venous stasis
- 24. METABOLIC DYSFUNCTIONS TYPE-2 DM •Inc resistance to insulin in periphery HYPERTENTION CORONARY ARTERY DISEASE CHOLILITHIASIS • Abnormal cholesterol metabolism HYPERCHOLESTEROLEMIA HYPERINSULINEMIA • Inc. sympathetic activation
- 25. Body Water • Reductionin total body water to 40% of TBW. • Relative dehydration may be present. • Poor tolerance to fluid load.
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- 27. Clinical Criteria forDiagnosing 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 ≥110 mg/dL Fasting glucose *Three of five criteria must be met.
- 28. OBESITY & DRUGSDOSES LIPID SOLUBLE 1. Inc. vol of distribution 2. 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.
- 29. • Commonly used anestheticdrugs 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.
- 30. Halogenated anaesthetics: • Morbidlyobese 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.
- 31. Pharmakinetics • Alternation indrug 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
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- 33. PREOPERATIVE HISTORY • Duration ofobesity & associated problems • Previous operation & anaesthesia • Medication
- 34. INVESTIGATIONS • Blood • Urine •LFTs • RFTs • ECG • X-Ray chest • Echocardiography • ABGs
- 35. RISK FOR ASPIRATIONPNEUMONIA • 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
- 36. ASSESS CARDIOPULMONARY RESERVE • • • • • History Physical examination-(BP,Edema) X-Raychest ECG ABGs IV & IA ACCESS • Technical difficulties
- 37. REGIONAL ANAESTHESIA-DIFFICULTIES • Obscuredlandmarks • 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)
- 38. INTRAOPERATIVE GA • PRE-OXYGENATION • POSITIONING •INDUCTION & INTUBATION • MAINTAINACE REGIONAL ANAESTHESIA • Technical difficulties • Doses of LA • Complications • Advantages
- 39. PREOXYGENATION SLIGHTLY HEAD UPPOSITION NECESSARY BECAUSE • Dec FRC • FRC Dec more on lying • Supine • After induction • Obese rapidly desaturate • Intubation may be difficult
- 40. OBESITY & V/Q MISMATCH •Chest obesity • Inc intraabdominal pressure DEC. FRC ATELACTASIS FRC < CC • Supine position • Induction • Muscle relaxation • Rt to Lt shunt • Rapid hypoxia V/Q MISMATCH
- 41. 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
- 44. INDUCTION & INTUBATION DIFFICULT TOVENTILATE WITH MASK RAPID SEQUENCE INTUBATION • Risk for aspiration VAREITY OF SCOPES • Long blade & short handle AWAKE INTUBATION-IF DIFFICULT • FOB
- 45. PEEP DURING INDUCTION Application ofpositive endexpiratory pressure during the induction of general anesthesia: • prevents atelectasis formation. • improves oxygenation and probably increases the margin of safety before intubation.
- 46. CONFIRMATION OF INTUBATION DIFFICULT TOCONFIRM BY AUSCULTATIONCLINICALLY CONFIRMED BY END TIDAL CO2
- 47. MAINTAINACE OF ANAESTHESIA HIGH INSPIREDO2 CONCENTRATION • LITHOTOMY,TRENDELENBURG & PRONE CONTROLLED VENTILATION – HIGH TIDAL VOLUMES PEEP-WORSEN PULMONARY HTN IN EXTREME OBESE
- 48. POSTOPERATIVE COSIDERATIONS EXTUBATION • Delayed untileffects of NMBAs completely reversed • Fully awake • Adequate airway maintenance • Adequate tidal volume • Supplemental oxygenation • Modified sitting position
- 49. POSTOPERATIVE COMPLICATIONS RESPIRATORY FAILURE •Major complication • Inc risk• Pre-ops hypoxia • Thoracic & upper abdominal Surgery DEEP VENOUS THOROMBOSIS PULMONARY EMBOLISM WOUND INFECTION
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- 56. MONITORING INVASSIVE MONITORING— HAEMODYNAMIC INSTABILITY • CVP • INTRA-ARTERILLINE • PULMONARY ARTERY CATHETER