Anesthesia for Bariatric
Surgery
By: Vladimir Melnikov MD
UT Dept. of Anesthesiology
Anesthesia for Bariatric Surgery
• Obesity affects millions of persons in the USA and around the world
• In 1990 $46 billion - 6.8% of all health care costs- was spent on
obesity related problems in the USA.
• Current estimates exceed $100 billion
• The precursors to obesity include
1.Genetic tendency
2.Environmental effect.
3.Education
4.Gender, ethnicity
5.Socioeconomic
Anesthesia for Bariatric Surgery
•
Medical co-morbidities associated with obesity
1. NIDDM
2. HTM
3. CV DISEASES
4. OSA
5. Liver & Gallbladder diseases
6. Arthritis
7. Colon and postmenopausal breast cancer
8. The risk of dying prematurely increases
9. Quality of life issues: depression, social incompetence,
etc.
Anesthesia for Bariatric Surgery
• Bariatrics is the field of medicine that specializes in treating obesity.
• Bariatric surgery is a surgical subspecialty that perform operations
to treat morbid obesity.
• Most of the patho-physiology & medical conditions associated with
extreme Obesity are reversible with sustained weight lose following
Bariatric surgery.
• Over 100,000 laparoscopic Bariatric procedures were performed in
the US in 2004.
• Mortality rate for Bariatric surgery is 0.5% - 1%!
Anesthesia for Bariatric Surgery
Definitions.
A person is considered obese when the
amount of body fat increases beyond the
point where health deteriorates and life
expectancy is shortened.
Two general types of obesity
1.Central-andriod Obesity associated with metabolic
syndrome
2.Periferal-gynecoid Obesity.
Anesthesia for Bariatric Surgery
Body Mass Index = weight/height x height
BMI = 25 – NORMAL
BMI>30 – OBESE
BMI>40 OR > with medical co-morbidity – Morbidly
obese
Ideal Weight = Height - 100
Anesthesia for Bariatric Surgery
PREOPERATIVE EVALUATION
1. CV & RESPIRATORY SYSTEMS
a) Tolerance of exercise and ability to lie flat.
b) Symptoms of sleep apnea should be sought.
2. Airways. Number of abnormalities may exist
a) Limitation of extension and flexion of the C-spine.
b) Restricted mouth opening from submental fat.
c) Large tongue.
d) Redundant intra oral tissue.
e) Thyromental distance should be assessed.
f) Infantile type anterior laryngeal opening.
3. Use of diet tablets (some of them cause valvular regurgitation or
pulmonary HT).
Anesthesia for Bariatric Surgery
PREOPERATIVE EVALUATION
4. Obesity Hypoventilation Syndrome. Pickwickian syndrome:
Obesity, excessive daytime sleepiness, snoring cor Pulmonale.
a) Hypercapnia
b) Severe hypoxemia
c) Periodic breathing
d) Biventricular enlargement (RT>LT)
e) Dependent edema.
f) Polycythemia. Pulmonary edema.
5. Metabolic Changes
Patient scheduled for surgery following previous Bariatric surgery may have chronic
metabolic changes.
Anesthesia for Bariatric Surgery
PREOPERATIVE EVALUATION
CV Systems.
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The degree of cardiac abnormality is correlated with the degree of
obesity.
LV dysfunction is often present in young asymptomatic patient
HTN
Increased Pre-load & After-load
Increased PAP (dyspnea, fatigue, syncope).
Pulmonary System.
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O2 consumption & CO2 production increased
WOB increased
Chest wall compliance & FRC are low.
Anesthesia for Bariatric Surgery
PREOPERATIVE EVALUATION
GI System.
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No difference in gastric volume or PH between lean and obese surgical
patient.
NIDDM and Gastroparesis.
Fatty Liver w or w/o liver dysfunction is common.
Gall bladder disease is also common.
Anesthesia for Bariatric Surgery
ANESTHETIC CONSIDERATIONS
PREMEDICATION
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Avoid heavy sedation.
Medication for chronic HTN
No diabetic medication on the morning of surgery
Antibiotics & heparine prophylaxis
H2 antagonist, metoclopramide?
Monitoring
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NIBP can be obtained from the wrist or ankle.
A-line highly recommended.
CVP or PA lines?
Nerve stimulator: needle electrodes are recommended (surface
electrode
Anesthesia for Bariatric Surgery
Pharmacological Considerations
1.
2.
3.
Drugs are often administered on the basis of
dose per unit body weight.
This assumes that clearances and
distribution volumes are proportional to
weight.
The assumptions 1&2 are not valid for obese
patients.
Anesthesia for Bariatric Surgery
Induction Agents
Larger than usual doses of Propofol or Thiopental are needed due to
increased blood volume & CO.
Muscle Relaxants
Higher doses of succinylcholine 1.5mg/kg IW are used.
Neuromuscular recovery time is similar in obese & non-obese patient with
CIS-ATRACURIUM (NIMBEX)
Complete paralysis is especially important during laparoscopy.
Neuromuscular blockade must be completely reversed before extubation.
OPIOIDS.
There is no evidence that lipophilic opioids last longer in morbidly obese
patient.
Anesthesia for Bariatric Surgery
TRACHEAL INTUBATION
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Increasing weight or BMI is not a risk factor for difficult
laryngoscopy.
FOB intubation is rarely necessary.
Rapid induction with Propofol &Succinylcholine is the best for
establishing an airway.
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Since mask ventilation can be difficult a second person
experienced with airway management should be present to
assist.
LMA should be available and can serve as abridge until an ETT
is placed.
Anesthesia for Bariatric Surgery
VENTILATION
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VT – 10-12ML/KG IW
FiO2 up to 1.0 may be needed
High PiP will be needed
PEEP = 5cm H2O
N2O is avoided
Pneumoperitoneum can displace diaphragm causing the ETT to
enter bronchus.
HEMODNAMIC CHANGES
The RTP may cause pooling of blood and hypotention.
Anesthesia for Bariatric Surgery
ANESTHETIC TECHNIQUE.
• OPIOIDS I>V> CONTINUOS INFUSION.
• CISATRACURIUM I.V. CONTINUOS INFUSION.
• INHALATION ANESTHETIC DEFLURANE.
POSTOPERATIVE CONSIDERATIONS.
Position: Upper body elevated 30-45 degree.
Oxygenation: Restoration of normal pulmonary function after abdominal
surgery may take several days.
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Nasal or mask O2.
Nasal CPAP
BiPAP
Analgesia:
An opioid PCA dosed on the basis of IW
NSAIDs