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Morbid obesityanaesthetic challenges. Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics PhD (physio) Mahatma Gandhi Medical college and research institute , puducherry India 1920 dandi march 2010 dandi march Body mass index Weight (Kg) / height (m)2 Weight = 75 Height =1. 5 metres 75/1.52 = 33.3 BMI ■ BMI of 18–25 = normal ■ BMI of 25.0–30 = overweight ■ BMI of 30.0–35 = class I obesity ■ BMI of 35.0–40 = class II obesity ■ BMI of 40 or greater = class III obesity. 20% of adults are obese and 1% morbidly obese Large and obese ?? It is important to recognise the difference between large patients and those who are obese. Some considerations such as medical equipment and manual handling will be very similar BUT ?? Large man Morbid obesity and co morbidities Respiratory system Restrictive lung disease Obstructive sleep apnea Obesity hypoventilation syndrome greater absolute oxygen consumption and carbon dioxide production OSAS five or more episodes of apnea lasting 10 seconds or more, associated with 4% decrease in oxygen saturation Dilators Hyoid muscles, genioglossus, tensor palati Tensor palati,genioglossus,hyoid muscles FRC and CV ?? ERV ** Expiratory reserve volume is the most sensitive indicator of the effect of obesity on pulmonary function testing. Hypertension – lean or obese ?? Lean - normal pre & after load Lean HT = ↑ after load Obese non ht = ↑ pre load Obese HT = ↑ after load & ↑ pre load Cardiovascular system Systemic and/or Pulmonary hypertension Ischemic heart disease, arrythmias DVT & Pulmonary embolus Congestive heart failure Fat cardiomyopathy There is a 3–4 mm Hg increase in systolic arterial pressure and a 2 mm Hg increase in diastolic arterial pressure for every 10 kg of weight gained. LVF + RVF = CCF Other systems Central nervous system Cerebrovascular accidents Endocrine system - Diabetes mellitus Gastrointestinal system - Hiatus hernia Musculocutaneous system Osteoarthritis Malignancies Breast Prostate Uterus Colon and rectum comorbidity increases with the duration of obesity (‘fat years’). Sedentary life style , smoking ?? Preop considerations psychological and personal needs as well as the need for appropriate counselling and information multi-disciplinary clinic Cardiology, Pulmonology Neurology DVT prophylaxis Preop considerations a supine SpO2 > 96% - ok Diabetes, hypertension renal, hepatic disease and autonomic neuropathy – evaluated Possible diet advice and preop weight loss Difficult IV access USG guided lines ?? Drugs taken orlistat also interferes with the absorption of fat-soluble vitamins, patients taking this drug need to be supplemented with the fat-soluble vitamins A, D, E, and K. Amphetamine analogues PREOP Talk to patient Routine inv. Electrolytes ECG, CxR, ECHO, PFT, Diabetes, H T, drugs LMWH Equipment Special equipment may be required, as standard equipment (beds, operating tables, ambulance and transfer trolleys) is often rated to a maximum safe weight well below that of the morbidly obese patient 115 kg tables – routine Premed some form of aspiration prophylaxis antibiotic prophylaxis Oral benzodiazipines – acceptable Pre oxygenation is achieved employing an anaesthesia facemask with an airtight seal End tidal O2 of 90 % end point Monitors Large blood pressure cuffs are useful for many patients Otherwise Think of tying in forearm Forced-air warming blankets NMJ monitoring Pulse, NIBP, (IBP), SPO2, ETCO2, Induction & position rapid sequence induction, utilizing cricoid pressure But if other predictors of difficult intubation – FOL awake Brachial plexus and sciatic and ulnar nerve palsies have been reported in patients with increased BMI. TBW, IBW, LBM Ideal body weight = Height - 100 lean body mass (or the ideal body weight plus 20%) Lean body mass = James formula = Lean Body Weight (men) = (1.10 x Weight(kg)) - 128 x ( Weight2/(100 x Height(m))2) Keep it simple 100 kg for men 80 kg for women Drug dosage Thio – 140 * 5 mg = 700 mg?? benzodiazepines and barbiturates are highly fat soluble , ideal body weight less fat-soluble drugs NDPs – Lean Body Mass succinylcholine, which should be dosed to total body weight Drug dosage Propofol is highly lipid-soluble, but also has a very high clearance. Its volume of distribution at steady state and clearance are proportional to total body weight. Using total i.v. anaesthesia, the infusion rate should be calculated on total body weight, not ideal body weight Dexmedetomidine Ideal Local anaesthetics Maximum dose -- ideal body weight i.e. 3 mg/kg reduced by 25% for subarachnoid and epidural blocks as engorged epidural veins and fat impinge on the volume of the epidural space. Position for intubation ‘sniffing the morning air’ position may be difficult to achieve due to the large soft tissue mass of the neck and chest wall, and a wedge or blanket beneath the shoulders is of benefit (‘ramped’ technique). Difficult intubation trolley ready Neck circumference Neck circumference has been identified as the single biggest predictor of problematic intubation in morbidly obese Difficult intubation is approximately 5% with a 40-cm neck circumference compared with a 35% probability with a 60-cm neck circumference Ramp position Idea of ramp position bring the patient’s chin to a higher point than the chest. So …. the mouth opening is better cricoid pressure takes up no space Laryngoscope placed in the mouthdoes not contact chest Short acting drugs Fentanyl, vecuronium, atracurium,desflurane ok Tidal volume ?? 500 ml for short , 700 ml for tall with PEEP Inh. Agents The MO patients metabolise halothane and enflurane to a greater extent than non obese leading to higher fluoride levels. High serum bromide levels and halothane hepatitis are more common in obese patients Regional anaesthesia Safety - as airway is safe USG guided blocks Spinal, epidural Locating the space and technical difficulty Needle length EPIDURAL Attractive for lung and other organs Abdominal muscles play a role in forced expiration Epidural in muscle strength ?? Recovery extubated wide-awake in the sitting position NSAIDs, paracetamol I.M. injections should be avoided because of unpredictable absorption Use a spinal needle !! Oxygen , CPAP we need a long spinal needle for IM injection!! Postoperative considerations hypoxia, respiratory obstruction positioning, humidification No shivering fluid intake - output, chest physiotherapy and incentive spirometry, DVT, analgesia , wound infection, early ambulation. Post op period complaints of buttock, hip, or shoulder pain in the postoperative period should raise the suspicion of Rhabdomyolysis Infiltration analgesia is the best. IV paracetamol For bariatric surgery Obese patients undergoing bariatric surgery would benefit from an approach similar to that for non– weight loss surgery 125 Kg male 42 years for FESS Ht = 175 Wt = 125 BMI = 40.8 Ideal body wt. = 175- 100 = 75 Lean body mass = 75 + 20% of 75 = 90 kg RAMP position Difficult airway trolley Premed = Inj. Pantocid Fentanyl = 75 Mic. Glyco = 0.2 Preoxy = 5 min. Thio = 300 mg approx ( 90 * 3.5) Suxa = 125 * 1.5 = 190 mg Atracurium = 75 * 0.4 = 30 mg followed by NMJ monitoring N2O : O2 = 3 : 2 Sevoflurane = 1 to 1.5 % Head up extubation Post op oxygen NSAIDs 3 chip camera – 18 lakhs Stryker HDTV monitor Postoperative shift O2 Ooosch appa Case over Ooosch appa !! Lecture is also over – thank you