Nearly half of adult Americans are obese, putting them at higher risk for several health issues. Should they be admitted for treatment, this patient group is slightly more challenging to intubate than others (11% vs. 7%).
The process requires clinicians’ collaborative effort, and many cases call for a second skilled airway management expert. When managing their intubation airways, simulation training has proven to be incredibly valuable.
As a provider of continuing medical education, Hospital Procedures Consultants (HPC) shares techniques for intubating obese patients, so you get an idea of how to perform them safely and efficiently while reducing complications and improving patient outcomes.
Why Is Intubation More Difficult Among Obese Patients?
Obese people have higher grading of modified Mallampati classification (MMC) due to a larger neck circumference (>44 cm) and altered respiratory physiology. This leads to difficulty in intubation, which contributes to significant mortality and morbidity.
Obese patients have a higher susceptibility to obstructive sleep apnea and hypoxia. During apnea in the OR, it takes them an average of 2.7 minutes to hit arterial oxygen saturation (SaO2) of 90%, even with preoxygenation. The speed of desaturation despite preoxygenation is even faster if they present with hypoxia. This can impact intubation success.
Patients with significant desaturation have higher rates of oxygen consumption and lower functional residual capacity (FRC). However, if high-flow nasal cannula is used for both preoxygenation and apneic oxygenation during intubation, they generate a positive airway pressure and cardiogenic oscillation. This leads to longer safe apnea time and quicker restoration among the morbidly obese during anesthesia induction.
Procedure for Intubation in Obese Patients
Obese patients have excessive tissue in the upper airways, head, and neck, and thus develop anatomical changes, such as the narrowing of the airway, reduced FRC, reduced chest wall compliance and lung compliance (microatelectasis), and the risk of aspiration.
Combined, they make intubation a more stressful and dynamic process. By considering the following, clinicians can increase first-attempt intubation success.
Drug Dosing
Practitioners must be familiar with the influence or changes in body composition and how to calculate accurate drug doses. This is necessary because basing pre-anesthetic decisions on total body weight alone could result in high doses and toxicities.
Here’s a formula you can use for accurate weight-based dosing:
IBW (ideal body weight) + 0.25 x (actual weight – IBW) or IBW + 0.4 x actual weight
Based on calculations, clinicians can use the following drugs (if indicated):
- Opioids like morphine and fentanyl can be administered for anesthesia induction.
- Succinylcholine is a short-acting skeletal muscle relaxant. It is administered in higher doses in obese patients for predictable tracheal intubation.
- Propofol is a bi-phasic with rapid clearance. However, since its potency is higher among the morbidly obese, dosing should be based on lean body weight.
- Rocuronium is a non-depolarizing neuromuscular blocker. It is not readily distributed to the peripheral tissues. As such, its dosing should be based on IBW to prevent its prolonged duration of action.
- Vecuronium is a peripherally-acting drug. Doses should never be based on the real body weight of obese patients as it could result in relative overdosing. This increases the duration of action while slowing down spontaneous recovery.
- Etomidate is a hypnotic IV anesthetic agent indicated for patients experiencing hemodynamic instability. The dosage can be given based on ideal body weight, but proceed with caution as it has been linked to biochemical adrenal insufficiency.
Additionally, midazolam, lorazepam, or ketamine are options for intubation induction agents.
Intubating Methods
Some airway management techniques for obese patients include:
Awake Intubation
Awake intubation is indicated for Mallampati class 3 or 4 or difficult airway. It can be combined with a video laryngoscopy to shorten the time it takes to intubate with no notable difference in the success rate, complication rate, or even patient satisfaction.
Rapid Sequence Intubation
It is used on patients with full stomachs or those at risk for pulmonary aspiration. This intubation technique is typically followed by neuromuscular blocking agents.
Delayed Sequence Intubation
Delayed sequence is indicated for patients with altered mental states. or agitation
Patients are given a dissociative dose of ketamine before being preoxygenated with a nonrebreather mask and nasal cannula or high-flow nasal cannula. This is followed by apneic oxygenation to increase the safe apnea time and complete intubation.
Positioning for Intubation
For successful intubation, studies recommend the use of a ramped position for morbidly obese patients. The head, upper body, and shoulders of the patient should be significantly elevated above the chest (you can place blankets or towels under the patient’s upper body), to place the external auditory canal at the same level as the sternal notch.
A study noted that this position contributed to the successful intubation of 99 out of 100 patients who underwent direct laryngoscopy. Since it maximizes the view, it leads to shorter intubation times and does not require significant lifting to expose the glottis during video laryngoscopy. This is because of the increased distance between the mentum and the cervical column which may provide a larger space for tube advancement.
However, it may not be sufficient for all morbidly obese patients. Patients with morbid obesity, for example, should adopt the reverse Trendelenberg position in addition to the ramp position. The reverse Trendelenberg position entails elevating the head 15 to 30 degrees higher than the feet. This reduces the transmission of intra-abdominal pressure on the diaphragm while lowering intragastric pressure and the risk of regurgitation.
It also increases the safe non-hypoxic apnea period by 41 seconds compared to the ramped position and decreases the recovery time compared to the supine position.
Improve Your Intubation Skills With HPC
Difficult intubation in obese patients, especially those who experience obstructive sleep apnea, can result in complications that range from cardiac arrhythmias and myocardial ischemia to cerebrovascular insufficiency and intracranial hypertension.
If unrecognized or inadequately treated, it can be nearly fatal.
Hospital Procedures Consultants can teach you how to minimize patient risks. Our courses can show you how to anticipate difficult intubations. You can also master techniques like endotracheal intubation and orotracheal intubation, increasing your first-pass intubation success while becoming a more confident healthcare practitioner.
Resources
Couture, E. J. Carrier-Boucher, A. Provencher, S. Tanoubi, I. Marceau, S. Bussières, J. S. Effect of reverse Trendelenburg position and positive pressure ventilation on safe non-hypoxic apnea period in obese, a randomized-control trial. BMC Anesthesiol. 2023; 23: 198. Published online 2023 Jun 8. doi: 10.1186
Liew, W. J. Negar, A. Singh, P. A. Airway management in patients suffering from morbid obesity. Saudi J Anaesth. 2022 Jul-Sep; 16(3): 314–321.
2022 Jun 20. doi: 10.4103
Wong, D. T. Dallaire, A. Singh, K. P. Madhusudan, P. Singh, M. Wong, J. Chung, F. Jackson, T. (2). High-Flow Nasal Oxygen Improves Safe Apnea Time in Morbidly Obese Patients Undergoing General Anesthesia: A Randomized Controlled Trial. Randomized Controlled Trial Anesth Analg. 2019 Oct;129(4):1130-1136. doi: 10.1213
Iyer, U. S. Koh, K. F. Chia, N. C. H. Macachor, J. Cheng, A. Perioperative risk factors in obese patients for bariatric surgery: a Singapore experience. Comparative Study Singapore Med J. 2011 Feb;52(2):94-9.
Uribe, A. A. Zvara, D. A. Puente, E. G. Otey, A. J. Zhang, J. Bergese, S. D. BMI as a Predictor for Potential Difficult Tracheal Intubation in Males. Front Med (Lausanne). 2015; 2: 38. 2015 Jun 4. doi: 10.3389
Danish. M. Preoxygenation and Anesthesia: A Detailed Review. Monitoring Editor: Alexander Muacevic and John R Adler. Cureus. 2021 Feb; 13(2): e13240. Published online 2021 Feb 9. doi: 10.7759/cureus.13240
Lyons, C. Callaghan, M. Uses and mechanisms of apnoeic oxygenation: a narrative review. Anaesthesia. 2019 Apr;74(4):497-507. doi: 10.1111/anae.14565. Epub 2019 Feb 19.
Seyni-Boureima, R. Zhang, Z. Antoine, M. M. L. K. Antoine-Frank, C. D. A review on the anesthetic management of obese patients undergoing surgery. BMC Anesthesiol. 2022; 22: 98. 2022 Apr 5. doi: 10.1186/s12871-022-01579-8
Hodzovic, I. Awake videolaryngoscope – guided intubation – well worth adding to your skill-mix. Rom J Anaesth Intensive Care. 2019 Apr; 26(1): 5–7.
doi: 10.2478/rjaic-2019-0001