1. Morbid Obesity M Pearson 12/3/16

2. BMI 19-24: Normal BMI > 30: Obesity BMI > 40: Extreme obesity

3. Patophysiology

4. Respiratory system < chest wall compliance Splinting diaphragm- < lung compliance << FRC Tendency to atelectasis Tendency to hypoxia V/Q mismatch OSA Pulmonary hypertension

5. Anatomic differences Large tongue Redundant oropharyngeal tissue Narrowed upper airway Presternal fat deposits Atlanto-axial joint limitation

6. OSA 5-10% incidence Collar size > 41 cm Progressive desensitization to low PO2 Evening alcohol consumption Daytime somnolence Snoring and apnoea

7. OSA : associated with Difficult mask ventilation Hypoxemic events Coronary ischaemia Arrythmias POST EXTUBATION PERIOD MOST DANGEROUS TIME!!

8. Cardiovascular system ++ blood volume - +SV - + CO > wall stress LV - LVH Pulmonary HTS.- R Heart failure Atrial dysrythmias Hypertension Arterosclerosis - IHD < venous return

9. Gastrointestinal Fatty infiltration liver Hiatus hernia GE Increased aspiration risk

10. Hematology Increased risk of DVTs Increased risk of infections

11. Obesity is a multi organ disease

12. Pharmacology Total body weight TBW - Overdosing Ideal body weight IBW - underdosing Lean body mass LBM - IBW + (20-40% of fat mass) Start with LBM, then titrate to effect Focus more on clinical end points Slow emergence due to delayed release from fat stores

13. Formulas Ideal body weight IBW Male : length (cm) - 100 Female : length (cm) - 105

14. Anaesthesia premed Beware of Benzo's for sedation Aspiration prophylaxis Careful positioning on table Padding Ulnar nerve neuropathy Secure with supports Weight that table can carry?

15. Anaesthesia: Induction Elevate head of bed Proper pre-oxygenation PEEP already during pre-oxygenation Ramp head and neck 2 hand technique face mask Ensure mask ventilation possible before muscle relaxant

16. Intubation and ventilation RSI with CUFFED ETT NOT LMA Vt 6-8 ml/kg IBW PEEP titrated to sat FiO2 < 0,8 Elevate head of bed Awake extubation in seated position!

17. Pain Management Avoid opioids Tramadol safest (30/70) Liberal use of neuro axial or peripheral nerve blocks Multimodal techniques Remember LMWH for DVT prophylaxis

18. Spinal anesthesia Elevate head and tilt to left Smaller volume local Technically more difficult Where is the midline???? More prone to post spinal headache

19. Laparoscopy in obesity Pneumoperitoneum ~atelectasis ~decreased FRC ~decreased compliance Leads to increased airway pressures Absorption of CO2 - increase RR Decreased hepatic blood flow Decreased renal blood flow Decreased preload with drop BP

20. Obese pregnant patient Longer surgery, spinal insufficient duration Increased incidence HTS and PET Gastric volume 5x greater 3x higher risk of c/s 10x higher risk of gestational DM Failed intubation in 33%

21. Obese pregnant patient Ideal do epidural if in early labour Do spinal in seated position Line from C2 to gluteal cleft middle Tuffier's line higher than L2/3 Epidural space seldom > 8 cm

22. GA for c/section Get consultant Get difficult intubation trolley Put in ramped position even if spinal done ( may need to convert!) Alternative preoxygenation 8 vital capacities RSI with Scoline 1mg/kg TBW ( max 200mg)

23. Clinical scenario Female 38 yr old Weight 148 kg Lenght 155 cm Booked for a lap steri BP 150/92 mmHg on ACEI

24. 1. Calculate her BMI 2. Calculate her IBW and LBM 3. Premed prescription 4. Airway management? 5. Post-op pain plan?

25. Desaturation with increased airway pressures Possible reasons and management