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Anaesthesia and the Obese Patient Lucy Smith Consultant Anaesthetist, St Georges Hospital 15th January 2009.

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Presentation on theme: "Anaesthesia and the Obese Patient Lucy Smith Consultant Anaesthetist, St Georges Hospital 15th January 2009."— Presentation transcript:

1 Anaesthesia and the Obese Patient Lucy Smith Consultant Anaesthetist, St Georges Hospital 15th January 2009

2 Outline Definitions/ Epidemiology Definitions/ Epidemiology Physiology of Obesity Physiology of Obesity Comorbidities Comorbidities Practical Aspects of Anaesthesia Practical Aspects of Anaesthesia Bariatric Surgery Bariatric Surgery

3 Definitions based on BMI BMI (kgm -2 ) Definition <18.5Underweight Ideal Weight Overweight Obese or with obesity-related comorbidity Morbidly Obese Super Obese Super Super Obese >70 Hyper Obese

4 Limitations BMI Not a direct measure of adiposity Not a direct measure of adiposity No account of fat distribution No account of fat distribution No account of duration of obesity No account of duration of obesity Inaccurate at extremes of height Inaccurate at extremes of height Inaccurate with extremes of lean body mass (eg athletes, elderly) Inaccurate with extremes of lean body mass (eg athletes, elderly) Waist or collar circumference more predictive of cardio-respiratory comorbidity Waist or collar circumference more predictive of cardio-respiratory comorbidity

5 Fat Distribution Android Android Central distribution Central distribution High intra-peritoneal fat content High intra-peritoneal fat content Increased neck circumference Increased neck circumference Waist-hip ratio >0.8 women, >1.0 men Waist-hip ratio >0.8 women, >1.0 men Increased morbidity (airway, CVS, metabolic, surgical) Increased morbidity (airway, CVS, metabolic, surgical) Gynaecoid Gynaecoid Peripheral sites (arms, legs, buttocks) Peripheral sites (arms, legs, buttocks)

6 Epidemiology of Obesity Epidemic in developed world Epidemic in developed world Increasing prevalence Increasing prevalence Major healthcare challenge Major healthcare challenge DOH reports: DOH reports: Overweight Obese Overweight Obese MFMF %29%13%16% %33%22%23%

7 Treatment Strategies Multidisciplinary approach Multidisciplinary approach Diet Diet Physical activities Physical activities Behavioral interventions Behavioral interventions Drugs Drugs Surgery Surgery

8 Physiology of Obesity Multifactorial - genetic, environmental Multifactorial - genetic, environmental Complex regulation of appetite and satiety Complex regulation of appetite and satiety Multiple humoral and neurological mechanisms Multiple humoral and neurological mechanisms Integrated and processed in hypothalamus Integrated and processed in hypothalamus Hormones include leptin, insulin, ghrelin, peptide YY 3-36 Hormones include leptin, insulin, ghrelin, peptide YY 3-36 Energy balance and appetite reflexes mediated by ANS Energy balance and appetite reflexes mediated by ANS

9 Pathways of energy balance

10 Models of obesity pathology Overeating and inactivity simplistic view Overeating and inactivity simplistic view Various pathways suggested Various pathways suggested Interactions not clearly established Interactions not clearly established Key features include Key features include Hyperinsulinaemia ( fat deposition) Hyperinsulinaemia ( fat deposition) Insulin resistance (type 2 diabetes) Insulin resistance (type 2 diabetes) Defective leptin signalling ( satiety) Defective leptin signalling ( satiety) food reward 2 0 to dopamine clearance in brain (insulin-mediated) food reward 2 0 to dopamine clearance in brain (insulin-mediated)

11 Obesity-related Comorbidities Prevalence increases with BMI and duration of obesity Prevalence increases with BMI and duration of obesity May be reason to undergo surgery May be reason to undergo surgery Severity may be masked by sedentary lifestyle Severity may be masked by sedentary lifestyle Major impact in perioperative period Major impact in perioperative period

12 Pathophysiology - Respiratory Higher energy turnover Higher energy turnover O 2 consumption, CO 2 production O 2 consumption, CO 2 production +/- chronic hybercarbia with renal compensation and altered CO 2 sensitivity +/- chronic hybercarbia with renal compensation and altered CO 2 sensitivity FRC, VC, (A-a) O 2, shunt FRC, VC, (A-a) O 2, shunt Airway closure (CC greater than FRC) Airway closure (CC greater than FRC) chest wall compliance and lung compliance work of breathing chest wall compliance and lung compliance work of breathing

13 Respiratory Comorbidity Airway Airway Obstructive Sleep Apnoea Obstructive Sleep Apnoea Obesity Hypoventilation Syndrome Obesity Hypoventilation Syndrome Asthma Asthma Pulmonary Hypertension Pulmonary Hypertension

14 Airway Difficulty predicted by OSA, short thick neck and BMI Difficulty predicted by OSA, short thick neck and BMI Fatty infiltration pharyngeal wall Fatty infiltration pharyngeal wall pharyngeal wall compliance pharyngeal wall compliance Difficult to ventilate by face mask Difficult to ventilate by face mask Rapid desaturation Rapid desaturation Consider awake fibreoptic intubation Consider awake fibreoptic intubation

15 Obstructive Sleep Apnoea Apnoeic episodes 2˚ to pharyngeal collapse occurring during sleep Apnoeic episodes 2˚ to pharyngeal collapse occurring during sleep Airfow ceases, ongoing effort, closed airway Airfow ceases, ongoing effort, closed airway >10s, >5/hour, >30/night >10s, >5/hour, >30/night Snoring, daytime somnolence, am headaches Snoring, daytime somnolence, am headaches Hypoxaemia, 2˚polycythaemia, systemic vasoconstriction, hypercarbia, pulmonary vasoconstriction, RVF Hypoxaemia, 2˚polycythaemia, systemic vasoconstriction, hypercarbia, pulmonary vasoconstriction, RVF

16 Obesity Hypoventilation Syndrome Altered control of breathing Altered control of breathing Diurnal variation Diurnal variation PaCO 2 >5.9kPa with 1.3kPa asleep PaCO 2 >5.9kPa with 1.3kPa asleep sO 2 not explained by obstruction sO 2 not explained by obstruction ventilatory response to CO 2 ventilatory response to CO 2 Often coexists with OSA Often coexists with OSA (OSAHS- Obstructive Sleep Apnoea Hypopnoea Syndrome) (OSAHS- Obstructive Sleep Apnoea Hypopnoea Syndrome)

17 Asthma Multiple factors Multiple factors Acid reflux and micro aspiration Acid reflux and micro aspiration Sleep apnoea and partial obstruction Sleep apnoea and partial obstruction Peripheral airway closure sheer stresses Peripheral airway closure sheer stresses proinflammatory response proinflammatory response Bariatric surgery % resolution Bariatric surgery % resolution

18 Pathophysiology - Cardiovascular blood volume + cardiac output blood volume + cardiac output ventricular workload ventricular workload myocardial fat content + contractility myocardial fat content + contractility Endothelial dysfunction + vascular resistance Endothelial dysfunction + vascular resistance 50% moderate HT, 5-10% severe HT 50% moderate HT, 5-10% severe HT +/- progressive PVR and PAP +/- progressive PVR and PAP Progresses to RVF. Oedema and hepatic congestion Progresses to RVF. Oedema and hepatic congestion

19 Cardiovascular Comorbidity Hypertension Hypertension Obesity cardiomyopathy Obesity cardiomyopathy Ischaemic Heart Disease (multiple factors) Ischaemic Heart Disease (multiple factors) Arrhythmias (hypoxaemia, hypertrophy, hypokalaemia, coronary art disease, raised catecholamines, OSA, fatty infiltration conducting and pacing systems) Arrhythmias (hypoxaemia, hypertrophy, hypokalaemia, coronary art disease, raised catecholamines, OSA, fatty infiltration conducting and pacing systems) Cor pulmonale Cor pulmonale

20 Gastrointestinal Comorbidity Type 2 diabetes Type 2 diabetes intra-abdominal pressure intra-abdominal pressure FRC, aortocaval compression, FRC, aortocaval compression, tissue perfusion, tissue perfusion, risk abdo compartment syndrome Fatty liver, steatohepatitis, cirrhosis Fatty liver, steatohepatitis, cirrhosis Hiatus hernia, gastro-oesophageal reflux Hiatus hernia, gastro-oesophageal reflux Hyperlipidaemia Hyperlipidaemia

21 Musculo-skeletal and Other Osteoarthritis Osteoarthritis Compression fractures Compression fractures Increased risk of injury Increased risk of injury Urinary incontinence Urinary incontinence Skin infections, candidiasis, poor hygiene Skin infections, candidiasis, poor hygiene Varicose veins Varicose veins Lymphoedema Lymphoedema

22 Preoperative Assessment Anaesthetic history Anaesthetic history Details of Comorbidities Details of Comorbidities Drug history (appetite suppressants) Drug history (appetite suppressants) Airway (MP, neck extension, circumference) Airway (MP, neck extension, circumference) Ability to tolerate supine position Ability to tolerate supine position Routine and specific investigations (may include baseline ABG, lung function tests, sleep studies, Echo, cardiac cath and PA pressure studies) Routine and specific investigations (may include baseline ABG, lung function tests, sleep studies, Echo, cardiac cath and PA pressure studies)

23 Practical Aspects of Anaesthesia Location: Operating theatre only Location: Operating theatre only Staff: plenty of strong, trained people! Staff: plenty of strong, trained people! Equipment: appropriate trolleys + table, electric beds, large BP cuffs, pillows, Equipment: appropriate trolleys + table, electric beds, large BP cuffs, pillows, patslide/ hover mattress, airway Premed: H 2 antagonist/ PPI Premed: H 2 antagonist/ PPI Positioning: Patient climb onto table, Positioning: Patient climb onto table, head up tilt 30˚, ramped- wedge under shoulders (sternum to thyroid cartilage - horizontal level)

24 Induction iv access (dorsum hand, flexor aspect forearm, central with US guidance) iv access (dorsum hand, flexor aspect forearm, central with US guidance) Consider arterial line Consider arterial line Preoxygenation at least 5 mins Preoxygenation at least 5 mins +/- RSI (dose sux 1mg/kg real body wt) +/- RSI (dose sux 1mg/kg real body wt) Intubation (short handle, long blade,) Intubation (short handle, long blade,) Awake fibreoptic intubation if indicated Awake fibreoptic intubation if indicated

25 Maintenance Short acting agents eg sevoflurane, desflurane, remifentanil Short acting agents eg sevoflurane, desflurane, remifentanil Temperature maintenance Temperature maintenance Neuromuscular monitoring Neuromuscular monitoring Ventilate with PEEP Ventilate with PEEP Pressure areas and skin Pressure areas and skin Calf compression Calf compression Fluids - insensible losses BSA Fluids - insensible losses BSA SV/ pulse pressure optimisation SV/ pulse pressure optimisation

26 Recovery Aim: rapid emergence with good airway control Aim: rapid emergence with good airway control Risks: loss of airway control, inadequate respiration, aspiration, postop chest complications, CVS stress and instability Risks: loss of airway control, inadequate respiration, aspiration, postop chest complications, CVS stress and instability Extubate wide-awake and sitting up +/- CPAP Extubate wide-awake and sitting up +/- CPAP recruitment procedure prior to extubation Appropriate postop environment Appropriate postop environment

27 Analgesia Multimodal - paracetamol, NSAIDs, opioids, LA, regional Multimodal - paracetamol, NSAIDs, opioids, LA, regional Paracetamol - central compartment so normal dose, clearance dose frequency Paracetamol - central compartment so normal dose, clearance dose frequency NSAIDs - risk renal dysfunction NSAIDs - risk renal dysfunction Opioids - risk respiratory depression Opioids - risk respiratory depression Regional - higher failure rate Regional - higher failure rate

28 Bariatric Surgery Weight loss surgery Weight loss surgery Procedures to treat obesity by modification of GI tract to reduce nutrient intake and/or reduce absorption Procedures to treat obesity by modification of GI tract to reduce nutrient intake and/or reduce absorption Tool enabling patient to alter lifestyle and eating habits to achieve effective and permanent management of obesity and eating behaviour Tool enabling patient to alter lifestyle and eating habits to achieve effective and permanent management of obesity and eating behaviour

29 Bariatric Surgery NICE Dec 2006 (CG43) Recommended as option if: Recommended as option if: BMI>40 (or 35 with significant comorbidity or severe DM) BMI>40 (or 35 with significant comorbidity or severe DM) All non-surgical measures tried and failed All non-surgical measures tried and failed Specialist obesity service involved Specialist obesity service involved Fit for anaesthesia and surgery Fit for anaesthesia and surgery Committed to long-term follow up Committed to long-term follow up First line option when BMI>50 First line option when BMI>50

30 Principles of Bariatric Surgery Reduction of stomach size (restrictive) Reduction of stomach size (restrictive) food enters small upper gastric pouch passes into lower stomach or intestine early filling, discomfort on eating more Restriction of size of gastric outlet Restriction of size of gastric outlet pouch or stomach remain full for longer Induction of malabsorption by intestinal bypass Induction of malabsorption by intestinal bypass

31 Vertical Banded Gastroplasty Restrictive Restrictive Stomach stapling Stomach stapling Smaller pre-stomach pouch Smaller pre-stomach pouch Small communication Small communication Rapid satiety Rapid satiety Upper part may distend over time Upper part may distend over time

32 Adjustable Gastric Band Restrictive Restrictive Silicone band Silicone band Small upper pouch approx 25ml Small upper pouch approx 25ml Inject saline via s/c port to adjust band to early satiety Inject saline via s/c port to adjust band to early satiety Upper pouch can distend Upper pouch can distend Band can become displaced Band can become displaced

33 Sleeve Gastrectomy Restrictive Restrictive Reduces stomach to 15% original size Reduces stomach to 15% original size Remove large portion following greater curve Remove large portion following greater curve Open edges joined to form sleeve or tube Open edges joined to form sleeve or tube Early fullness, no outflow obstruction Early fullness, no outflow obstruction May be converted in 2nd stage procedure to gastric bypass or duodenal switch May be converted in 2nd stage procedure to gastric bypass or duodenal switch

34 Roux-en-Y Gastric Bypass Mixed restrictive and malabsorptive Mixed restrictive and malabsorptive Small stomach pouch Small stomach pouch Connect pouch to small intestine Connect pouch to small intestine Upper small intestine re-attached in y-shape approx 45cm below stomach outlet Upper small intestine re-attached in y-shape approx 45cm below stomach outlet

35 Sleeve Gastrectomy with Duodenal Switch Mixed restrictive and malabsorptive Mixed restrictive and malabsorptive Stomach disconnected from duodenum Stomach disconnected from duodenum Connected to distal small intestine Connected to distal small intestine Duodenum and upper small intestine attached cm from colon Duodenum and upper small intestine attached cm from colon

36 Jejunoileal Bypass Malabsorptive procedure no longer performed Malabsorptive procedure no longer performed Proximal jejunum anastomosed to distal ileum, 10cm before caecum Proximal jejunum anastomosed to distal ileum, 10cm before caecum Short length functional bowel Short length functional bowel Long blind loop Long blind loop Problems with severe malabsorption, dumping, liver failure, cardiac failure, renal stones Problems with severe malabsorption, dumping, liver failure, cardiac failure, renal stones

37 Laparoscopic Bariatric Surgery Head-up position (up to 45˚) Head-up position (up to 45˚) venous pooling in lower limbs venous return, cardiac output venous return, cardiac output Pneumoperitoneum Pneumoperitoneum venous return, cardiac output venous return, cardiac output intra-abdominal pressure intra-abdominal pressure migration gas into tissues progressive pCO 2 activation SNS - arrythmias, SVR, BP PAP, ICP PAP, ICP High inpiratory pressure + PEEP

38 Complications of Bariatric Surgery General General infection, haemorrhage, incisional hernia, bowel obstruction, VTE Specific Specific anastomotic leak, anastomotic stricture, dumping syndrome, nutritional deficiencies (iron, vit B 12, thiamine, protein malnutrition, vit A)

39 Risk Factors for Complications M>F M>F Age >65 Age >65 Open Surgery Open Surgery Long operation time Long operation time Cardiac and Respiratory comorbidities Cardiac and Respiratory comorbidities Diabetes Diabetes Low case load Low case load

40 Health Benefits Sustained loss of 65-80% excess body weight Sustained loss of 65-80% excess body weight Diabetes resolves very rapidly Diabetes resolves very rapidly Asthma resolves early on Asthma resolves early on OSA - most asymptomatic in 1 year OSA - most asymptomatic in 1 year Hyperlipidaemia resolved in >70% Hyperlipidaemia resolved in >70% Essential hypertension resolved in >70% Essential hypertension resolved in >70% GOR relieved in most GOR relieved in most Low back pain and joint pain relieved in most Low back pain and joint pain relieved in most self esteem, participation in social activities self esteem, participation in social activities

41 Summary Obesity is a major healthcare challenge Obesity is a major healthcare challenge Daily challenge for anaesthetists Daily challenge for anaesthetists Obese patients are at risk from comorbidities and pathophysiological changes of obesity Obese patients are at risk from comorbidities and pathophysiological changes of obesity Bariatric surgery is a beneficial and cost- effective healthcare intervention Bariatric surgery is a beneficial and cost- effective healthcare intervention


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