Morbid obesity- anaesthetic challenges.

1. Morbid obesity- anaesthetic challenges. Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics PhD (physio) Mahatma Gandhi Medical college and research institute , puducherryIndia

2. 1920 dandi march

3. 2010 dandi march

4. Body mass index • Weight (Kg) / height (m)2 • Weight = 75 • Height =1. 5 metres • 75/1.52 • = 33.3

5. 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

6. 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 ??

7. Large man

8. Morbid obesity and co morbidities • Respiratory system • Restrictive lung disease • Obstructive sleep apnea • Obesity hypoventilation syndrome • greater absolute oxygen consumption and carbon dioxide production

9. 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

10. Tensor palati,genioglossus,hyoid muscles

11. FRC and CV ??

12. ERV ** • Expiratory reserve volume is the most sensitive indicator of the effect of obesity on pulmonary function testing.

13. Hypertension – lean or obese ?? • Lean - normal pre & after load • Lean HT = ↑ after load • Obese non ht = ↑ pre load • Obese HT = ↑ after load & ↑ pre load

14. Cardiovascular system • Systemic and/or • Pulmonary hypertension • Ischemic heart disease, arrythmias • DVT & Pulmonary embolus • Congestive heart failure • Fat cardiomyopathy

15. 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

16. Other systems • Central nervous system Cerebrovascular accidents • Endocrine system - Diabetes mellitus • Gastrointestinal system - Hiatus hernia • Musculocutaneous system Osteoarthritis

17. Malignancies • Breast • Prostate • Uterus • Colon and rectum • comorbidity increases with the duration of obesity (‘fat years’). • Sedentary life style , smoking ??

18. Preop considerations • psychological and personal needs as well as the need for appropriate counselling and information • multi-disciplinary clinic • Cardiology, • Pulmonology • Neurology • DVT prophylaxis

19. 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 ??

20. 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

21. PREOP • Talk to patient • Routine inv. • Electrolytes • ECG, CxR, ECHO, PFT, • Diabetes, H T, drugs • LMWH

22. 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

23. 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

24. 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,

25. 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.

26. 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)

27. Keep it simple • 100 kg for men • 80 kg for women

28. 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

29. 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

30. 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.

31. 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

32. 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

33. Ramp position

35. 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 mouth- does not contact chest

36. Short acting drugs • Fentanyl, vecuronium, atracurium,desflurane ok • Tidal volume ?? • 500 ml for short , 700 ml for tall with PEEP

37. 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

38. Regional anaesthesia • Safety - as airway is safe • USG guided blocks • Spinal, epidural • Locating the space and technical difficulty • Needle length

39. EPIDURAL • Attractive for lung and other organs • Abdominal muscles play a role in forced expiration • Epidural in muscle strength ??

40. 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

41. we need a long spinal needle for IM injection!!

42. Postoperative considerations • hypoxia, respiratory obstruction positioning, humidification No shivering • fluid intake - output, • chest physiotherapy and incentive spirometry, • DVT, analgesia , wound infection, • early ambulation.

43. 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

44. For bariatric surgery • Obese patients undergoing bariatric surgery would benefit from an approach similar to that for non–weight loss surgery

45. 125 Kg male 42 years for FESS

46. Ht = 175 Wt = 125 • BMI = 40.8 • Ideal body wt. = 175- 100 = 75 • Lean body mass = 75 + 20% of 75 = • 90 kg

47. RAMP position

48. Difficult airway trolley

49. 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

50. N2O : O2 = 3 : 2 • Sevoflurane = 1 to 1.5 % • Head up extubation • Post op oxygen • NSAIDs