Transcript Anaesthesia and the Obese Patient

Anaesthesia and the
Obese Patient
Lucy Smith
Consultant Anaesthetist, St George’s Hospital
15th January 2009
Outline
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Definitions/ Epidemiology
Physiology of Obesity
Comorbidities
Practical Aspects of Anaesthesia
Bariatric Surgery
Definitions based on BMI
BMI (kgm-2)
<18.5
18.5-24.9
25-29.9
30-39.9
40-49.9 or 35-49.9 with
Definition
Underweight
Ideal Weight
Overweight
Obese
Morbidly Obese
obesity-related comorbidity
50-59.9
60-69.9
>70
Super Obese
Super Super Obese
Hyper Obese
Limitations BMI
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Not a direct measure of adiposity
No account of fat distribution
No account of duration of obesity
Inaccurate at extremes of height
Inaccurate with extremes of lean body mass
(eg athletes, elderly)
Waist or collar circumference more
predictive of cardio-respiratory comorbidity
Fat Distribution
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Android
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Central distribution
High intra-peritoneal fat content
Increased neck circumference
Waist-hip ratio >0.8 women, >1.0 men
Increased morbidity (airway, CVS,
metabolic, surgical)
Gynaecoid
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Peripheral sites (arms, legs, buttocks)
Epidemiology of Obesity
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Epidemic in developed world
Increasing prevalence
Major healthcare challenge
DOH reports:
Overweight
Obese
M
F
M
F
2001 43%
29%
13%
16%
2006 43%
33%
22%
23%
Treatment Strategies
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Multidisciplinary approach
Diet
Physical activities
Behavioral interventions
Drugs
Surgery
Physiology of Obesity
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Multifactorial - genetic, environmental
Complex regulation of appetite and
satiety
Multiple humoral and neurological
mechanisms
Integrated and processed in hypothalamus
Hormones include leptin, insulin, ghrelin,
peptide YY3-36
Energy balance and appetite reflexes
mediated by ANS
Pathways of energy balance
LEPTIN
adipose tissue
content
INSULIN
acut e metabolic
status
AP P ET IT E REGULAT ION
 neuropeptde
i Y
 melanocyt e stimulat ing
hormone
CNS input s
HYPOTHALAMUS
vent romedial
GHRELIN
from st omach
signal hunger
P ept ide YY3-36
from smallint estine
signals sat iet y
HYPOTHALAMUS
paraventricular nucleus
lat eral hypothalamic area
FOOD SEEKING
BEHAVIOUR
AUT ONOMIC
NERVOUS SYST EM
SNS -  energy use
P NS Ğ insulin secretion
and energy st ora
ge
Models of obesity pathology
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Overeating and inactivity simplistic view
Various pathways suggested
Interactions not clearly established
Key features include
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Hyperinsulinaemia (fat deposition)
Insulin resistance (type 2 diabetes)
Defective leptin signalling (satiety)
food reward 20 to dopamine clearance in
brain (insulin-mediated)
Obesity-related Comorbidities
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Prevalence increases with BMI and
duration of obesity
May be reason to undergo surgery
Severity may be masked by sedentary
lifestyle
Major impact in perioperative period
Pathophysiology - Respiratory
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Higher energy turnover
 O2 consumption,  CO2 production
+/- chronic hybercarbia with renal
compensation and altered CO2 sensitivity
FRC, VC, (A-a) O2, shunt
Airway closure (CC greater than FRC)
chest wall compliance and lung
compliance  work of breathing
Respiratory Comorbidity
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Airway
Obstructive Sleep Apnoea
Obesity Hypoventilation Syndrome
Asthma
Pulmonary Hypertension
Airway
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Difficulty predicted by OSA, short thick
neck and BMI
Fatty infiltration pharyngeal wall
pharyngeal wall compliance
Difficult to ventilate by face mask
Rapid desaturation
Consider awake fibreoptic intubation
Obstructive Sleep Apnoea
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Apnoeic episodes 2˚ to pharyngeal collapse
occurring during sleep
Airfow ceases, ongoing effort, closed airway
>10s, >5/hour, >30/night
Snoring, daytime somnolence, am headaches
Hypoxaemia, 2˚polycythaemia, systemic
vasoconstriction, hypercarbia, pulmonary
vasoconstriction, RVF
Obesity Hypoventilation Syndrome
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Altered control of breathing
Diurnal variation
PaCO2 >5.9kPa with 1.3kPa asleep
sO2 not explained by obstruction
ventilatory response to CO2
Often coexists with OSA
(OSAHS- Obstructive Sleep Apnoea
Hypopnoea Syndrome)
Asthma
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Multiple factors
Acid reflux and micro aspiration
Sleep apnoea and partial obstruction
Peripheral airway closure sheer stresses
 proinflammatory response
Bariatric surgery  80-100% resolution
Pathophysiology - Cardiovascular
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blood volume + cardiac output
ventricular workload
myocardial fat content + contractility
Endothelial dysfunction +vascular resistance
50% moderate HT, 5-10% severe HT
+/- progressive PVR and PAP
Progresses to RVF. Oedema and hepatic
congestion
Cardiovascular Comorbidity
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Hypertension
Obesity cardiomyopathy
Ischaemic Heart Disease (multiple factors)
Arrhythmias (hypoxaemia, hypertrophy,
hypokalaemia, coronary art disease, raised
catecholamines, OSA, fatty infiltration
conducting and pacing systems)
Cor pulmonale
Gastrointestinal Comorbidity
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Type 2 diabetes
intra-abdominal pressure
 FRC, aortocaval compression,
tissue perfusion,
risk abdo compartment syndrome
Fatty liver, steatohepatitis, cirrhosis
Hiatus hernia, gastro-oesophageal reflux
Hyperlipidaemia
Musculo-skeletal and Other
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Osteoarthritis
Compression fractures
Increased risk of injury
Urinary incontinence
Skin infections, candidiasis, poor hygiene
Varicose veins
Lymphoedema
Preoperative Assessment
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Anaesthetic history
Details of Comorbidities
Drug history (appetite suppressants)
Airway (MP, neck extension, circumference)
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)
Practical Aspects of Anaesthesia
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Location: Operating theatre only
Staff: plenty of strong, trained people!
Equipment: appropriate trolleys + table,
electric beds, large BP cuffs, pillows,
patslide/ hover mattress, airway
Premed: H2 antagonist/ PPI
Positioning: Patient climb onto table,
head up tilt 30˚, ‘ramped’- wedge under
shoulders (sternum to thyroid cartilage horizontal level)
Induction
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iv access (dorsum hand, flexor aspect
forearm, central with US guidance)
Consider arterial line
Preoxygenation at least 5 mins
+/- RSI (dose sux 1mg/kg real body wt)
Intubation (short handle, long blade,)
Awake fibreoptic intubation if indicated
Maintenance
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Short acting agents eg sevoflurane,
desflurane, remifentanil
Temperature maintenance
Neuromuscular monitoring
Ventilate with PEEP
Pressure areas and skin
Calf compression
Fluids - insensible losses  BSA
SV/ pulse pressure optimisation
Recovery
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Aim: rapid emergence with good airway
control
Risks: loss of airway control, inadequate
respiration, aspiration, postop chest
complications, CVS stress and instability
Extubate wide-awake and sitting up +/- CPAP
recruitment procedure prior to extubation
Appropriate postop environment
Analgesia
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Multimodal - paracetamol, NSAIDs,
opioids, LA, regional
Paracetamol - central compartment so normal
dose, clearance dose frequency
NSAIDs - risk renal dysfunction
Opioids - risk respiratory depression
Regional - higher failure rate
Bariatric Surgery
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Weight loss surgery
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
Bariatric Surgery
NICE Dec 2006 (CG43)
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Recommended as option if:
BMI>40 (or 35 with significant
comorbidity or severe DM)
All non-surgical measures tried and failed
Specialist obesity service involved
Fit for anaesthesia and surgery
Committed to long-term follow up
First line option when BMI>50
Principles of Bariatric Surgery
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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
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pouch or stomach remain full for longer
Induction of malabsorption by intestinal bypass
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Vertical Banded Gastroplasty
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Restrictive
‘Stomach stapling’
Smaller pre-stomach
pouch
Small communication
Rapid satiety
Upper part may
distend over time
Adjustable Gastric Band
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Restrictive
Silicone band
Small upper pouch
approx 25ml
Inject saline via s/c
port to adjust band to
early satiety
Upper pouch can
distend
Band can become
displaced
Sleeve Gastrectomy
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Restrictive
Reduces stomach to 15% original size
Remove large portion following greater
curve
Open edges joined to form sleeve or tube
Early fullness, no outflow obstruction
May be converted in 2nd stage procedure
to gastric bypass or duodenal switch
Roux-en-Y Gastric Bypass
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Mixed restrictive and
malabsorptive
Small stomach pouch
Connect pouch to
small intestine
Upper small intestine
re-attached in y-shape
approx 45cm below
stomach outlet
Sleeve Gastrectomy with Duodenal
Switch
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Mixed restrictive and
malabsorptive
Stomach
disconnected from
duodenum
Connected to distal
small intestine
Duodenum and upper
small intestine
attached 75-100cm
from colon
Jejunoileal Bypass
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Malabsorptive procedure no longer
performed
Proximal jejunum anastomosed to distal
ileum, 10cm before caecum
Short length functional bowel
Long blind loop
Problems with severe malabsorption,
dumping, liver failure, cardiac failure,
renal stones
Laparoscopic Bariatric Surgery
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Head-up position (up to 45˚)
venous pooling in lower limbs
venous return, cardiac output
Pneumoperitoneum
venous return, cardiac output
intra-abdominal pressure
migration gas into tissues
progressive pCO2
activation SNS - arrythmias, SVR, BP
PAP, ICP
High inpiratory pressure + PEEP
Complications of Bariatric Surgery
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General
infection, haemorrhage, incisional
hernia, bowel obstruction, VTE
Specific
anastomotic leak, anastomotic
stricture, dumping syndrome,
nutritional deficiencies (iron, vit B12,
thiamine, protein malnutrition, vit A)
Risk Factors for Complications
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M>F
Age >65
Open Surgery
Long operation time
Cardiac and Respiratory comorbidities
Diabetes
Low case load
Health Benefits
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Sustained loss of 65-80% excess body weight
Diabetes resolves very rapidly
Asthma resolves early on
OSA - most asymptomatic in 1 year
Hyperlipidaemia resolved in >70%
Essential hypertension resolved in >70%
GOR relieved in most
Low back pain and joint pain relieved in most
self esteem, participation in social activities
Summary
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Obesity is a major healthcare challenge
Daily challenge for anaesthetists
Obese patients are at risk from
comorbidities and pathophysiological
changes of obesity
Bariatric surgery is a beneficial and costeffective healthcare intervention