Induction Challenges In Obese Patients - Overvægtig patient intuberes på operationsstuen.

Induction Challenges In Obese Patients

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As Your Specialist in Acute Care, we understand that obese patients present a set of challenges and require specific perioperative care compared with lean patients. They have a higher risk of complications. In addition, placing obese patients in a supine position further reduces respiratory compliance. Therefore, different methods in ventilation and positioning must be used to improve pre-oxygenation, induction and recovery.  Based on current literature, the following shows how to minimize the higher risk of complications in obese patients.

Why are obese patients a challenge during general anesthesia induction?

The number of obese patients undergoing surgery is steadily increasing1. There are different grades of obesity, from slight obesity to morbid obesity. A patient having a BMI of 40 or higher or being overweight by 100 pounds (see table) is considered morbidly obese. Obesity has become a major global health challenge and is expected to become even more widespread in the future. As an analysis of the Global Burden of Disease Study 2013 shows, between 1980 and 2013 the combined prevalence of overweight and obese persons worldwide rose by 27.5% in adults and 47.1% in children2. In all, the number of overweight and obese people worldwide increased from 857 million in 1980 to 2.1 billion in 20132. Obesity now appears not only to be a phenomenon of developed western countries; most other parts of the world also show a significant increase in obesity2.

World Health Organization classification of obesity

Body mass index (kg.m2)


< 18.5


18.5 – 24.9


25.0 – 29.9


30.0 – 34.9

Obese 1

35.0 – 39.9

Obese 2

> 40.0

Obese 3 (previously ‘morbid obesity’)

The Health and Social Care Information Centre (HSCIC) together with the NHS in the UK reported a 30% increase in bariatric surgical procedures over the past 10 years and a ten-fold increase in hospital episodes related to obesity. Obese patients in the UK account for approx. 25% of all patients admitted to the ICU3. As the prevalence of obesity increases worldwide, obese surgical patients will be a growing challenge for physicians in the OR.

Why do obese patients suffer a higher incidence of anesthetic complications?

Obesity, especially morbid obesity, results in reduced lung volumes, significant atelectasis in dependent lung regions and a ventilation/perfusion mismatch. At the same time oxygen consumption and the work of breathing are increased4. This combination means that, following the onset of apnea, arterial oxygen levels may decrease rapidly. The reason for this lies in specific changes in the anatomy and physiology of obese patients, amplifying the risks associated with general anesthesia compared to non-obese patients and making obese patients prone to perioperative complications4. An altered strategy to pre-oxygenation and induction for obese patients may be considered, as desaturation occurs quickly in the lung and airway management can be difficult.

Obesity during the induction phase: what we should keep in mind

Standard anesthesia induction for elective surgical patients includes a brief period of pre-oxygenation followed by the injection of anesthetic drugs, a test of manual ventilation and endotracheal intubation or placement of a supraglottic airway. This standard approach suffices for most patients. Obesity can complicate the perioperative oxygenation and ventilation of surgical patients and is a frequently mentioned risk factor for mask ventilation and/or tracheal intubation5. In addition to the technical challenges, the reduced lung volumes (i.e. FRC), increased ventilation-perfusion mismatch and respiratory comorbidities make anesthetic induction and airway management a high-risk period for hypoxemic events and other respiratory complications6.

Therefore, obese and morbidly obese patients may require adapted approaches to pre-oxygenation and induction. Apart from acute difficulties during induction, more complications may occur during the maintenance (e.g. increased atelectasis) phase and may persist during the postoperative phase if the approach for pre-oxygenation and induction is not adapted to the physiology of these patients.

Whitepaper: Effective pre-oxygenation and induction for obese patients

Pre-oxygenation and Induction in Obese Patients

Get an overview of recommendations for pre-oxygenation and induction in obese patients as provided in the literature.

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More suggested downloads

Technology insights: Induction in obese patients
Technology insights: induction in obese patients

This paper provides information on how technology can support in managing obese patients during general anesthesia.

Infographic: Obesity in general anesthesia
Infographic obesity in anesthesia

There is an increased recognition that obese patients require specific care during surgery. Take a look at our summary of pre- and postoperative management of obese patients.

Obese patients during recovery and in the postoperative phase

The post-operative phase may hold more respiratory challenges for obese patients when compared to non-obese patients. The effects of obesity described in our whitepaper persist in the post-operative phase. Obese patients suffering from obstructive sleep apnea (OSA) or from obesity hypoventilation syndrome (OHS) may be at a higher risk of postoperative pulmonary complications (PPCs) as opiate sensitivity adds to the severity of nocturnal hypoxia7.

Obese patients are more likely to develop post-operative acute respiratory failure and have higher rates of pneumonia7. Morbidly obese patients, known to have significantly more atelectasis preoperatively compared to non-obese patients, will develop more atelectasis after extubation. In non-obese patients, atelectasis developed during operation will return to normal within 24 hours postoperatively. In morbidly obese patients, atelectasis is more likely to persist8. This atelectasis increases the work of breathing further as the patient then breathes at lower lung volumes. This in turn is associated with early airway closure and expiratory flow limitations resulting in the development of intrinsic PEEP (PEEPi). These factors are worsened in the supine position – a potential challenge in the recovery room7.

Considering these factors, obese patients should be kept in an elevated position, such as the reversed Trendelenburg position or with elevated head and torso. Elevation mitigates intra-abdominal pressure effects on the lungs which in turn improves oxygenation and lung compliance. Continuous positive airway pressure (CPAP) and non-invasive ventilation (NIV) have been demonstrated to be beneficial since they can restore and maintain lung volumes and reduce the work of breathing. Particularly in morbidly obese patients, CPAP applied immediately after extubation improved spirometry 24 hours postoperatively as compared to deferring initiation of external CPAP to the recovery room. NIV has also been demonstrated to be feasible. One study demonstrated a 16% reduction in risk for post-extubation respiratory failure by the application of NIV immediately after extubation of patients with a BMI of >35. In addition, postoperative early mobilization and respiratory physiotherapy is recommended7.

In summary: Obese patients not only require adapted approaches during pre-oxygenation, induction and maintenance of general anesthesia, but modified respiratory care techniques in the immediate postoperative period have also been shown to be important in preventing postoperative pulmonary complications.

Technology insight: Recovery of obese patients

Technology insight: Recovery of obese patients

This paper provides further insights into how our technologies can support the transition of spontaneous breathing in obese patients during recovery.

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  1. Candiotti K, Sharma S, Shankar R. Obesity, obstructive sleep apnoea, and diabetes mellitus: anaesthetic implications. Br J Anaesth 2009;103 (Suppl. 1):i23–30.
  2. Ng M, Fleming T, Robinson M, et al: Global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 2014;384:766-781.
  3. Health and Social Care Information Centre. The Health Survey for England - 2012 trend tables. London: Health and Social Care Information Centre, 2013 Link
  4. Pelosi P, Croci M, Ravagnan I, et al. The effects of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia. Anesth Analg 1998;87:654–60.
  5. Pelosi P, Gregoretti C. Perioperative management of obese patients. Best Pract Res Clin Anesthesiol. 2010;24(2):211–225.
  6. Santesson J. Oxygen transport and venous admixture in the extremely obese. Influence of anesthesia and artificial ventilation with and without positive end-expiratory pressure. Acta Anesthesiologica Scandinavica 1976; 20: 387–94.
  7. Hodgson LE, Murphy PB, Hart N. Respiratory management of the obese patient undergoing surgery. J Thorac Dis. 2015 May;7(5):943-52.
  8. Eichenberger A, Proietti S, Wicky S, et al. Morbid obesity and postoperative pulmonary atelectasis: an underestimated problem. Anesth Analg. 2002 Dec;95(6):1788-92.