Anaesthesia in

Obese Patients
 Obesity
The prevalence of obesity (BMI ≥ 30 Kg/m2) has increased in
the recent years, and this condition is one of a major risk
factors for other diseases such as cancer, metabolic
disturbances and heart disease.

The American Society of Anaesthesiologists Physical

Status Classification System has Classified:
Obesity Class II (BMI ≥ 35-39,9 Kg/m2) in ASA II ( a patient
with mild systemic disease)
Obesity Class III (BMI ≥ 40 Kg/m2) in ASA III ( a patient with
severe systemic disease).
Patients with Apple Body Obesity
type are more likely to suffer from
related obesity morbidities in
Obesity is a challenging problem in surgery, for it is related
anaesthesia than the Pear Body
Obesity type. to several side effects and complications before or during
surgery.
Challenges in Anaesthesia-Related Processes for
Obese Patients
Obesity is quite challenging during Anesthesia due to reasons like:

Difficulty in locating patients’ vein for

Obesity patients who have metabolic
delivering intravenous anaesthetics or
syndromes are at high risk of post-
other medications.
operative cardiopulmonary complications,
acute kidney injury and sepsis.
Difficulty in determining the right
medication dosage.
Challenge of ensuring enough oxygen
It may take longer time for patients to level and airflow, specially if patients
regain consciousness and to recover suffer from OSA.
after surgery.
Difficulty in airway management (bag-
mask ventilation and/or tracheal
Increase risk of breathing problems due
intubation).
to narcotics and pain medicines.
 Pre-Operative Evaluation

1. Comprehensive Medical Management 2. Airway Management

Mask ventilation or intubation

Physiological parameters such as : fat
must be considered in all obese
distribution, waist circumference, waist to
patients even though there will be
hip ratio, upper airway, OSAS.
difficulties regarding the
application.
Laboratory test: ECG, CBC,
Haemostasis, Fasting serum glucose, Lipid
profile, kidney function, and hepatic 3. Post Operative Care Planning
function.

The Obesity Surgery Mortality

Other test if indicated:
Risk Score (OS-MRS) was
Echocardiography, ergometry, chest
developed to predict the risk of
radiograph, spirometry, ABGs,
death in obese patients.
polysomnography, index of inflammation.
 Pre-Operative Evaluation

4. Pre-Anaesthesia Medications

• Post-operative infections Prophylaxis: Antibiotics

• Post-operative nausea and vomiting (PONV) prophylaxis: Dexamethasone,

Ondansetron, etc

• Post-operative pain prophylaxis: Pregabaline, Gabapentine

• Improving sleep postoperative: Melatonin

• Venous thromboembolism (VTE) prophylaxis: mechanical methods (thromboembolic

stockings, sequential alternating compressive devices), subcutaneous unfractionated
heparin or low molecular weight heparin (LMWH).

• Pre-operative anxiolysis: Benzodiazepines, Ketamine + clonidine or dexmedetomidine

 Pre-Operative Evaluation

5. Drug Dosing

Weight-based Anaesthetic Dosing Regimen

Anesthetic drug Dosing regimen
Induction: LBW; • Optimal drug dosing scalars is necessary
Propofol
maintenance: TBW for safe and effective anaesthesia. Dosing
Thiopental
Induction: IBW; scalars other than TBW must be
maintenance: LBW
considered when administering drugs in
Fentanyl TBW
obese patients
Remifentanil IBW
Succinylcholine TBW • Administering drugs based on TBW can
Vecuronium, Rocuronium IBW cause overdose, while administration
Atracurium IBW
based on IBW can result in a
Domi R et al. Anesthetic challenges in the obese patient. Journal of Anesthesia.
2012 total body weight; LBW: lean body weight, male:100 Kg,
subtherapeutic dose.
TBW:
female: 70 Kg; IBW: ideal body weight, male: height (cm)-100,
 
female: height(cm)-105.
 Pre-Operative Evaluation

6. Equipment and Monitoring

Appropriate operating tables and other

equipment are required for safe anaesthesia in
obese patients.

Obese Patient Positioning

 The correct ramped position involves elevation of

the upper body, neck and head so that an
imaginary horizontal line can be drawn from the
sternal notch to the external ear.
 This position is good for mask ventilation and
intubation.
Image source: Carron M et al. Perioperative care of obese
 The 30° reverse Trendelenburg position improves
patients. BJS. 2020. lung volumes and pulmonary compliance provide a
longer safe apnoea period.
 Intra-Operative Management

Intubation

Choosing The Best laryngoscope: video-laryngoscopes were superior, it can increase the
success rate, reducing intubation time and improving glottic visualization.

Mechanical Ventilation
Preoxygenation, to prevent desaturation, which is much faster in obese than in normal-weight
patients and to increase oxygen reserve. The preoxygenation effect is augmented by 25
head-up position or by applying continuous positive airway pressure (CPAP) and positive
end-expiratory pressure (PEEP).

Anaesthetic Management
Rapid sequence induction should be considered for symptomatic GERD or other conditions
which are prone to aspiration (such as diabetes mellitus, gastrointestinal disorders,
emergency surgery). Data suggest beneficial effects of volatile compared to intravenous
anesthetics. Desflurane is an example of inhalational anaesthetics,
 Intra-Operative Management

Analgesia
Considering non-opioid analgesics more than opioid, such as IV Paracetamol and NSAID,
ketamine, α-2 agonists (clonidine, dexmedetomidine), magnesium and local or regional
anaesthesia. Good analgesia care can prevent the use of opioid after surgery.

Neuromuscular Blockade
It is used to achieve better/favorable airway management. The example is by administering
of both succinylcholine and rocuronium.

Fluid and temperature management

Fewer post-operative complications are associated with restrictive fluid management. Perioperative
hypothermia can be avoided by using active forced-air warming and heated intravenous fluids in
obese patients.
 Post-Operative Management
Head elevated position
Should be in in a 30-45o up for recovery.
Monitor for the following PACU (post-
anaesthesia care unit) events at least 1
Starting CPAP after extubation hour:
- Recurrent desaturation (SpO2 < 90%, 3+
it has benefits such as: reduce hypoventilation episodes)
and atelectasis, improve gas exchange and - Recurrent bradypnea (respiratory rate <
respiratory function, relieve dyspnoea and 8 / min, 3+ episodes)
decrease breathing effort in obese patients after - Apnoea ( 10 s, 1+ episodes)
surgery. They may therefore lower the risk of - Pain-sedation mismatch
acute respiratory failure after surgery - Bleeding
- Intraoperative severe surgical lesions
Analgesia
When intravenous opioids are required after
operation, patient-controlled analgesia (such as
fentanyl or morphine) is recommended, instead of
a continuous infusion.
 Intra-Operative Management
Before discharge

Before discharge from recovery unit the patient should:

• Have unsupported stable vital signs with minimal inspired oxygen requirement;

• Show no evidence of hypoventilation;

• Be free from apnoea without stimulation;

• Be able to use a CPAP device if required.

Considering to lose weight under supervision when it is not urgent

before surgery is good, for it can reduce the risk of complications
and improve patients’ health before surgery.
Thank You !
 Resources

1. ASA. Obesity [Internet]. American Society of Anesthesiologists. 2021 [ cited 25 May

2021]. Available at:
https://www.asahq.org/madeforthismoment/preparing-for-surgery/risks/obesity/
2. ASA. ASA Physical Status Classification System [Internet]. American Society of
Anaesthesiologists. 2021 [ cited 25 May 2021]. Available at:
https://www.asahq.org/standards-and-guidelines/asa-physical-status-classification-
system
3. Domi R, Laho H. Anaesthetic challenges in the obese patient. J Anesth. 2012
Oct;26(5):758-65. doi: 10.1007/s00540-012-1408-4.
4. Wynn-Hebden A, Bouch DC. Anaesthesia for the obese patient. BJA Educ. 2020
Nov;20(11):388-395. doi: 10.1016/j.bjae.2020.07.003.
5. Carron M, Fakhr BS, Ieppariello G, Folleto M. Perioperative care of obese
patients. BJS. 2020;107(2):e39-e55.
6. Bazurro S, Ball L, Pelosi P. Perioperative management of obese patient. Curr
Opin Crit Care. 2018 Dec;24(6):560-567. doi: 10.1097/MCC.0000000000000555.