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Anaesthesia and Morbid Obesity

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Presentation on theme: "Anaesthesia and Morbid Obesity"— Presentation transcript:

1 Anaesthesia and Morbid Obesity

2 Facts 20% adults Obese (1% Morbidly Obese)
BMI >35 with comorbidity / BMI >40 without comorbidity = morbidly obese BMI > 55 = super-morbidly obese BMI > 30 – rapid increase in morbidity and mortality Men – higher risk of CVS problems

3 Apples and Pears BMI poor predictor of difficulty Fat distribution
Android Gynaecoid

4 Causes of Obesity Multifactorial Genetic and Environmental
Regulation of appetite and satiety (Hypothalamus) Leptin, Adiponectin – long term (NB dieting) Insulin = short term (Hypothalamus) Ghrelin (Stomach Wall), Peptide YY 3-36 (Intestine) Leptin/Adiponectin – produced by fat cells. Leptin = reduction in food seeking behaviours. Obese people have more leptin but increased leptin insensitivity. Adiponectin doers same but not increased in obesity. Stretching of stomach wall suppresses Ghrelin – satiety. Peptide YY – food in intestine - satiety

5 Comorbidity

6 Facts Obesity associated with:
Htn DM OA Liver Disease Asthma OSA Obesity Hypoventilation Syndrome Risk of cardio-resp comorbidity increases with duration NB severe comorbidity may be masked by sedentary lifestyle!

7 Respiratory System - OSA
Apnoeic attacks due to collapse of pharynx whilst asleep Increases with obesity and age Fat in pharyngeal wall Features Snoring Frequent apnoeic spells whilst asleep (>10s) Daytime somnolescence Pathophysiological changes – hypercapnia, polycythaemia, pulmonary htn and cor-pulmonale

8 Obesity Hypoventilation Syndrome
Affects control of breathing CO2 sensitivity and ventilatory drive partly leptin controlled Leptin insensitivity = reduced ventilatory response to CO2. Depressant drugs accentuate Often combined with OSA

9 Respiratory Compromise
Features Hypoxaemia at rest (worse supine + depressants) Rapid desaturation in apnoea Reduced lung compliance (increased pulm blood volume) Reduced chest wall compliance Small airways collapse + diaphragmatic splinting (Decreased FRC) Increased alveolar-arterial oxygen tension (worse on induction) Closing volume close to FRC – airway closure and V/Q mismatch (shunting) Atelectasis NB Laparoscopy!! Postoperative period Decreased FRC with increasing BMI - <1L in BMI>40.

10 Cardiovascular System
Circulating Volume (renin-angiotensin. Polycythaemia). Ventricular Workload Redistributed to fat beds Cerebral/Renal flows unchanged Oxygen Consumption (Increased BMR) CO2 production Systemic Htn (LV stress and LVH) Pulm Htn possible (Cor-Pulmonale) Increased metabolic demands of adipose

11 Cardiovascular System
Arrythmias – Why? Myocardial hypertrophy and hypoxaemia Hyperkalaemia (Htn Rx) CAD Increased circulating catecholamines OSA Fatty infiltration conducting system IHD Htn DM Cholesterol Sedentary Lifestyle DVT/PE

12 Other Sytems Microvesicular Fatty Liver
Steatohepatitis +/- cirrhosis GORD and Hiatus Hernia (Aspiration) Insulin resistance and Type 2 DM

13 Preoperative Assessment

14 Planning Ahead Beware the Sedentary Patient Questioning
Symptoms and signs of OSA/Heart Failure Comorbid disease Ability to tolerate supine position Full airway assessment Mouth opening, Mallampati, Neck movement, Collar circumference Any airway obstruction whilst awake

15 Pre-Op Investigations
Individual basis FBC, U+Es, LFTs, Glucose ABG in suspected OSA/OHS ECG Echo – LV/RV function, Pulm Htn CXR – cardiac failure PFTs – poor exercise tolerance RV strain or cor-pulmonale may benefit from elective night NIV pre elective surgery

16 PreMed Antacids / PPI Prokinetics Sodium Citrate TEDs

17 Conduct of Anaesthesia

18 Pharmacokinetics Most drugs affected by adipose tissue – lipophilic drugs How do you calculate doses?! Volume of central compartment similar (periph increased) Increased Volume of Distribution (Vd) Increased redistribution Increased elimination t1/2

19 Total weight/ideal weight
Benzos/Barbiturates – ideal body weight Relaxants – Lean body mass (mass of organs, muscle, bone) Suxamethonium – total body weight Propofol – total body weight (esp TIVA) Local anaesthetics – ideal body weight Epidurals – Engorged veins and fat impinge on space Reduced volume of Epidural Space Reduce dose by 25%

20 Practical Aspects Theatre Table Enough staff to transfer
Correct sized bp cuff Consider Position Could they be head-up? Sniffing position Pre-oxygenation The Difficult Airway Ventilatory Issues Positioning PEEP Short-handle/Polio blade Desaturation Do they need awake fibreoptic? Temperature Control Volatile choice Calf Compression Beware Laparoscopy Epidural?

21 Postoperative Considerations
Extubation Risk of obstruction To CPAP? Location Post-Op Care Good analgesia Early mobilization, TEDS, Enoxaparin Close monitoring of BMs (Catabolism) Cardiovascular stability

22 Any Questions?


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