Supraglottic Airway Use in the Adult Obese Population BY Chris Burford, RN, BSN Faculty Mentor: Debra Maloy, EdD, CRNA, Associate Professor Graduate Programs of Nurse Anesthesia Texas Wesleyan University Fort Worth, Texas May, 2018 With 36% of Americans being obese (BMI > 30 kg/m2) anesthesia practitioners increasingly care for patients in this population.1 Supraglottic airway (SGA) devices are considered safe alternatives to endotracheal tubes with their use expanding into more complicated procedures and their inclusion in difficult airway algorythms.2,3 SGA used as a stand-alone device in the obese population requires more research to demonstrate clinical safety. However, is it possible they can play a crucial role in this populations airway management?4,5 This case report will investigate the current recommendations for SGA use in the obese population. Case Report An 83-year-old, 104.5 kg, 1.55 m (body mass index 43 kg/m2) morbidly obese female presented for sentinel node biopsy of left breast. Medical history was significant for gastroesophageal reflux disease (GERD), active breast cancer, asthma, mild aortic stenosis, mild mitral valve regurgitation, mild tricuspid valve regurgitation, ejection fraction of 65%, hypertension, hyperlipidemia, diverticulitis, hypothyroidism, type 2 diabetes mellitus, and stage III kidney disease. Surgical history included hysterectomy, knee arthroscopy and previous bilateral breast biopsies. The patient’s medication regimen included atorvastatin, montelukast, fenofibrate, ASA, gabapentin, losartan, carvedilol, levothyroxine, albuterol HFA, esomeprazole, triamterene, HCTZ and regular insulin. The patient had allergies to penicillin, amoxicillin, metoclopramide and propoxyphene. Laboratory results were unremarkable. ECG revealed sinus bradycardia, left ventricular hypertrophy, ST deviation and moderate T-wave abnormality. Preoperative airway exam revealed a Mallampati 2 classification, thyromental distance greater than 3 fingerbreadths, full range of motion of the neck, and an incisor distance of greater than 3 cm. The patient was taken to the operating room and placed in the supine position. Noninvasive monitoring was initiated and initial vital signs were heart rate (HR) 61/min, blood pressure (BP) 155/80 mm Hg, SpO2 92% on room air, respiratory rate (RR) 12/min, and temperature 36.5 oC. Oxygen was administered via facemask at 10 L/min until expired oxygen concentration was greater than 85%. General anesthesia was induced with lidocaine 80 mg and propofol 180 mg. After loss of lid reflex a supraglottic airway was inserted and the patient was placed on pressure control ventilation until spontaneous respirations returned. Anesthesia was maintained with sevoflurane 0.8-2.5% expired concentration in a mixture of oxygen 1 L/min and air 1 L/min. Analgesia was accomplished with fentanyl 25 mcg and augmented by surgeons injecting local after induction. A total of lactated ringers 250 ml was used for maintenance IV fluid. Vital signs were stable throughout with the exception of a 5-7 minute period of post induction hypotension and bradycardia treated with ephedrine 15 mg and glycopyrrolate 0.4 mg respectively. During emergence the anesthetic gas and air were turned off and oxygen flows were increased to 10 L/min. The laryngeal airway was removed when the patient was following commands with adequate regular spontaneous ventilations. The patient was then transferred to the recovery room in stable condition. Discussion Dr. Larry Brain, the inventor of the Laryngeal Mask Airway (LMA, Teleflex Medical Europe Ltd., Athlone, Ireland), accomplished the first airway rescue with the LMA in a morbidly obese patient. The patient consequently underwent a successful three-hour abdominal procedure with respirations controlled by a mechanical ventilator through the relatively new device without anesthesia complications.6 Since then there have been many iterations of that original LMA. Each device can typically be defined by where they seal; base of the tongue or peri-laryngeal, how they seal; cuffed or non-cuffed, the incorporation of a gastric access tube to facilitate aspiration protection and whether or not they allow intubation thru the ventilation tube. They are more broadly referred to in the literature as supraglottic airways (SGA), extraglottic airway devices or supralaryngeal airways. The equipment used on this patient for the duration of the case was a cuffed, intubating, peri-laryngeal SGA without a gastric access tube.7 There is currently no uniform classification system for these devices so for this case study SGA will be used generically. Expanding SGA use in more complicated procedures was explored in an observational study of 200 non-obese patients undergoing off-pump coronary artery bypass grafting (CABG) comparing the endotracheal tube (ETT) to a cuffed SGA with a gastric tube. The investigation evaluated adverse effects such as hypoxemia, bronchospasm, secretion, airway trauma and soreness throughout the case. The authors concluded the SGA performed better than the ETT with lower hemodynamic responses, lower use of muscle relaxation and fewer adverse events relating to hypoxemia, bronchospasm and upper respiratory tract trauma ultimately declaring it a safe alternative to endotracheal tubes.2 Coincident with the expansion of SGA use are reservations about their limitations. A recent meta-analysis of 10 randomized controlled trials including 996 patients suggested that using certain types of SGAs in patients at high risk of aspiration could not be recommended. They also concluded problems could be encountered using SGAs in morbidly obese patients.8 However, the researchers in this meta-analysis reported the incidence of aspiration to be similar between the ETT and the SGA group and the sample size was too small to draw any definitive conclusions. The CABG study supported the use of SGAs as a safe alternative to the ETT but excluded patients who were obese.2 The meta-analysis did not exclude obese patients and did take a position discouraging SGA use in morbidly obese patients even though this position was not explicitly tied to the research.8 These positions only marginally inform decisions on using SGAs in the morbidly obese population. Morbidly obese patients often present with a variety of airway management complications resulting in hypoxemia and low oxygen saturation much more quickly than in the non-obese population. Interventions to improve airway management in the obese community are; the use of positive end-expiratory pressure (PEEP), twenty-five degrees head up ramp positioning and continuous positive airway pressures (CPAP) during preoxygenation and emergence.1,5 The patient, in this case report, was a morbidly obese insulin dependent diabetic with GERD, all of which place her at an increased risk for aspiration. Current studies do not support the use of an SGA as a sole ventilation device with this type of patient because the sample sizes are too small to rule out the increased risks and more importantly the studies each focus on specific types of SGAs and these specific results cannot be generalized to all SGAs.1,8 However, SGA use is being studied as an adjunct in the anesthetic management of obese patients with some success. Specifically, incorporating the SGA into the preoxygenation phase of induction reduced the duration of hypoxemia in the obese patient.5 This information supports the use of SGAs in maintaining adequate oxygenation in the obese patient and is discussed below. One objective measure used to evaluate adequate preoxygenation is the concept of the safe apnea period (SAP). One study defined the SAP as the time lapse between cessation of a 5 minute period of ventilation with a fraction of inspired oxygen (FiO2) of 100% to the point the apneic patient reaches a SpO2 of 92%. In this study, 100 patients with BMI > 35 kg/m2 were preoxygenated with 100% oxygen for 5 minutes and then induced with midazolam, fentanyl, propofol and atracurium. Mechanical ventilation via face mask with oropharyngeal airway or SGA was instituted with volume control ventilation settings of: tidal volume of 8 ml/kg, RR of 12/minute, FiO2 of 1.0 and PEEP of 5 cm H2O. Ventilation ended at the end of 5 minutes and measurements were taken. These investigations revealed that the use of an SGA was superior to the traditional approach of mask ventilation with an oropharyngeal airway. Specifically, the mean SAP in the SGA group was 337 seconds compared to 205 seconds for the face mask group.5 Utilizing this approach allowed an additional 2 minutes with adequate oxygenation to establish a definitive airway. This study confirms superior SAP times with SGA devices and supports the use of the SGA in the morbidly obese population as a bridge to intubation. Research does support the SGA to manage a difficult airway and as a bridge to a more definitive airway.3,5 However, a sufficient body of research is needed to established evidence-based guidelines for SGA use in this population as a replacement for the ETT. Currently, the sample sizes are too small to develop credible conclusions.8 Additionally, many studies focus on specific types of SGAs, and this data does not apply to the many different designs of SGAs available.1 The case considered in this report did not result in any adverse outcomes as a result of the use of an SGA. However, a current review of evidence did not support the use of an SGA as the sole ventilation device for the duration of the case. References 1. Nguyen-Mason J, Rodriguez R. Laryngeal mask airway use in morbidly obese patients undergoing general anesthesia. AANA Journal . Apr2017, Vol. 85 Issue 2, p130-135. 6p. 2. Shah K. ProSeal laryngeal mask airway as an alternative to standard endotracheal tube in securing upper airway in the patients undergoing beating-heart coronary artery bypass grafting. Ann Card Anaesth. 2017;20(1):61-66. 3. Apfelbaum J, Hagberg C, Caplan R, et al. American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology. 2013;118(2):251-270. 4. Nicholson A, Cook TM, Smith AF, Lewis SR, Reed SS. Supraglottic airway devices versus tracheal intubation for airway management during general anaesthesia in obese patients. Cochrane Database Syst Rev. 2013;(9):CD010105. 5. Sinha A, Jayaraman L, Punhani D. ProSeal LMA increases safe apnea period in morbidly obese patients undergoing surgery under general anesthesia. Obes Surg. 2013;23(4):580-4. 6. Van Zundert TC, Brimacombe JR, Ferson DZ, Bacon DR, Wilkinson DJ. Archie Brain: celebrating 30 years of development in laryngeal mask airways. Anaesthesia. 2012;67(12):137585. 7. Michálek P, Miller D. Airway management evolution - in a search for an ideal extraglottic airway device. Prague Med Rep. 2014;115(3-4):87-103. 8. Xu R, Lian Y, Li WX. Airway Complications during and after General Anesthesia: A Comparison, Systematic Review and Meta-Analysis of Using Flexible Laryngeal Mask Airways and Endotracheal Tubes. PLoS ONE. 2016;11(7):e0158137. Mentor: Debra Maloy, EdD, CRNA, Associate Professor, Graduate Programs of Nurse Anesthesia dmaloy@txwes.edu Smart Learning Objectives: 1. At the conclusion of a careful reading of this case study, every phase II nurse anesthesia student will be able to identify 3 interventions to overcome airway complications commonly found in the obese population. 2. At the conclusion of a careful reading of this case study, every phase II nurse anesthesia student will be able to elucidate the results of the study involving the measurement of the safe apnea period in obese patients. 3. At the conclusion of a careful reading of this case study, every phase II nurse anesthesia student will be able to understand the significance of the results of the safe apnea study as it relates to the induction phase of anesthesia. Continuing Education Questions: 1. A patient with a body mass index of >40 kg/m2 falls into what American Society of Anesthesiologist classification? 2. Who invented the laryngeal mask airway? 3. What percentage of Americans have a body mass index > 30 kg/m2? 4. Is there a current codified classification system for supraglottic airway devices? 5. How does PEEP improve oxygen reserves? 6. What physiologic principle does a 25 degree head up ramp position for pre-oxygenation and induction of anesthesia address in the obese population? 7. How is functional residual capacity impacted in the obese population in the supine position? 8. How can insulin dependency place a patient at higher risk for aspiration? 10. How can the use of a SGA device in the pre-oxygenation phase of induction impact oxygen reserves in obese patients?