key: cord-331452-y5lhawqo
authors: Lentz, Skyler; Grossman, Alexandra; Koyfman, Alex; Long, Brit
title: High-Risk Airway Management in the Emergency Department: Diseases and Approaches Part I
date: 2020-05-12
journal: J Emerg Med
DOI: 10.1016/j.jemermed.2020.05.008
sha: 
doc_id: 331452
cord_uid: y5lhawqo

Abstract Background Successful airway management is critical to the practice of emergency medicine. Thus, emergency physicians must be ready to optimize and prepare for airway management in critically ill patients with a wide range of physiologic challenges. Challenges in airway management commonly encountered in the emergency department are discussed using a pearl and pitfall discussion in this first part of a two-part series. Objective This narrative review presents an evidence-based approach to airway and patient management during endotracheal intubation in challenging cases commonly encountered in the emergency department. Discussion Adverse events during emergent airway management are common with post-intubation cardiac arrest reported in as many as 1 in 25 intubations. Many of these adverse events can be avoided by proper identification and understanding the underlying physiology, preparation, and post intubation management. Those with high risk features including severe metabolic acidosis; shock and hypotension; obstructive lung disease; pulmonary hypertension, right ventricle failure, and pulmonary embolism; and severe hypoxemia must be managed with airway expertise. Conclusions This narrative review discusses the pearls and pitfalls of commonly encountered physiologic high-risk intubations with a focus on the emergency clinician.

Successful airway management is a critical skill in emergency medicine. 1, 2 The majority of 26 emergent and unplanned intubations in emergency departments (ED) are managed by emergency 27 physicians using rapid-sequence intubation, with success rates as high as 99%. 2-4 However, 28 emergency physicians must be able to prepare for and manage critically ill patients with a wide 29 range of physiologic challenges in the peri-intubation setting. 30 31 First pass success is a priority in any attempt at endotracheal intubation, but especially in 32 physiologically challenging airways, as multiple attempts are associated with an increase in 33 adverse events. 5,6 Difficult visualization and intubation, generally defined as 3 or more attempts, 34 occur as often as 6.6-12% in critically ill patients. [6] [7] [8] [9] This rate may be decreasing in the ED 35 population, potentially because of video laryngoscopy or improved techniques, as shown by a 36 decreased rate of multiple attempts of 1.5% in a more recent study of ED intubations. 4 Severe 37 complications occur as frequently as 24-28% of endotracheal intubation in critically ill patients, 38 most commonly hypoxemia and hypotension. 6, 8 Patients with high risk comorbid disease and 39

pre-intubation factors such as hypoxemia, hypotension, and severe acidosis are at high risk for 40 peri-intubation hemodynamic collapse and resultant worse outcomes. 8,10-13 The incidence of 41 peri-intubation cardiac arrest is as high as 1 in 25 emergency airways in one series. 10 Post-42 intubation hypotension is more common, occurring as frequently as 25% of emergency 43 intubations and is associated with increased mortality. 11 Many of the pre-intubation risks for 44 decompensation can be recognized and prevented with proper preparation and evaluation. 8,10,14-18 45 46 This first part of a two-part series will focus on the latest literature, recommendations, and 47 tidal volume of 8 mL/kg predicted body weight (PBW) or higher may be needed. A blood gas 120 should be assessed within 15 minutes of intubation to make sure the pH has not significantly 121 worsened. Continuous ETCO 2 may be used to follow PaCO 2 once intubated; in the patient with 122 normal lung function the ETCO 2 value is 2-5 mm Hg lower than PaCO 2 . 20,31 123 124 There are many different mechanical ventilator strategies post intubation. 12,24 When the sedation 125 and neuromuscular blockade medications are metabolized some advocate for spontaneous 126 ventilatory modes such as pressure support ventilation so the patient can set the respiratory rate, 127 tidal volume, and inspiratory time. 12 Alternatively, adequate sedation and assist control modes of 128 ventilation with a prescribed tidal volume (e.g. VC-AC) or pressure (PC-AC) and respiratory rate 129 may be used, but the patient should be monitored for patient-ventilator dyssynchrony with the 130 increased respiratory drive stimulated by the acidosis. 12,24 The recommended approach is to 131 deliver a guaranteed minute ventilation by setting the respiratory rate and a starting tidal volume 132 of 8 mL/kg PBW in an assist control type mode. 

Patients with shock and hypotension requiring intubation and mechanical ventilation are at high 144 risk for peri-intubation cardiovascular collapse. 7,8,10,17,32 Post intubation hypotension (PIH) is 145 common and occurs in up to 25% of emergently intubated patients, is associated with adverse 146 outcomes, and should be aggressively avoided and treated. 8,11,12,33 Studies suggest pre-intubation 147 hypotension and shock index >0.8-0.9 (heart rate/systolic blood pressure [BP] ) are the best 148 predictors of post-intubation cardiac arrest and PIH. 7,10,12,17,32 The shock index is associated with 149 severity of illness and suggests impending instability. 17 Post-intubation cardiac arrest occurs in 150 approximately 2%, though one series reported a higher rate of 4.2% in emergency intubations. 10 151

The reported incidence of cardiac arrest in those with pre-intubation hypotension is even higher 152 at 12-15% of emergency intubations. 7,10 Post intubation cardiac arrest is unsurprisingly 153 associated with increased mortality. 8 

In those with anticipated hemodynamic instability, the dosing and familiarity of the induction 

Respiratory failure from obstructive lung disease, such as asthma and chronic obstructive 214 and a respiratory acidosis with a pH of > 7.20 can be tolerated in most patients aside from those 264 with a potential contraindication to a respiratory acidosis such as those with pulmonary 265 hypertension, brain injuries at risk for increased intracranial pressure (ICP), severe right sided 266 heart failure, pregnancy, and certain toxic ingestions. 49 267 Table 3 obstructive lung disease likely indicates hyperinflation from auto-PEEP. 53 The peak pressure will be elevated due to airway resistance, but this pressure is less important, and can be tolerated, if 282 the plateau pressure remains < 30 cm H 2 O, since the peak pressure is not transmitted to the 283 alveoli of lung parenchyma. 24,28,53 An example of a pressure waveform in a mechanically 284 ventilated patient with high airway resistance is demonstrated in Figure 2 . requiring emergent intubation in the ICU, preoxygenation with NIPPV compared to non-408 rebreather mask resulted in an increased SpO 2 after preoxygenation as well as during and after 409 intubation. 67 Episodes of severe desaturation to SpO 2 < 80% were significantly less common in 410 the NIPPV group than the control group (2/27 compared to 12/26). 67 The FLORALI-2 trial 411 compared preoxygenation with HFNC to NIPPV in 322 ICU patients with acute hypoxemic 412 respiratory failure. 68 It found no significant difference in the incidence of severe hypoxemia or 413 serious adverse events between groups. However, in the subgroup of patients with pre-intubation 414 moderate-to-severe hypoxemia (Pa0 2 /FiO 2 < 200), NIPPV resulted in a statistically significant 415 decrease in incidence of severe hypoxemia. 68 Of note, the lack of difference may be confounded 416 by the fact that NIPPV ventilation group received no apneic oxygenation while the HFNC group 417 continued to receive apneic oxygenation via HFNC. NIPPV may be beneficial in those with 418 severe hypoxemia for preoxygenation, as this group had equivalent overall outcomes and 419 reduced hypoxemia despite not receiving apneic oxygenation. 68 The benefit of HFNC for preoxygenation and apneic oxygenation compared to conventional 428 oxygen therapy is unclear. Several small randomized controlled trials comparing HFNC to BVM 429 or face mask in hypoxemic patients found no statistically significant difference in mean lowest 430

SpO 2 between groups. [70] [71] [72] Recently, the OPTINIV trial compared the combination of HFNC 431 and NIPPV to NIPPV alone for preoxygenation in ICU patients requiring intubation for 432 hypoxemic respiratory failure. 73 The intervention group (HFNC + NIPPV) continued to receive 433 apneic oxygenation via HFNC while the NIPPV group alone received no further oxygenation 434 after the standardized 4-minute preoxygenation period. Authors found that the intervention 435 groups had higher minimum SpO 2 during intubation (100% vs 96%) and fewer episodes of 436 desaturation SpO 2 <80% (0% vs 21%) than the control group. 73 It is important to note that these preoxygenation strategies are effective in those requiring 443 intubation due to respiratory infections. In the study by Baillard et al, 65-70% of included 444 patients had a diagnosis of pneumonia. 67 Additionally, 35% of study participants in the 445 FLORALI-2 trial had primary respiratory failure due to infection. 68 Though discussion of airway 446 management for patients with novel COVID-19 is beyond the scope of this paper, in the midst of 447 a respiratory illness pandemic appropriate personal protective equipment (PPE) with airborne 448 precautions, careful donning and doffing of PPE, and use of negative pressure rooms should be 449 employed to reduce the risk of disease transmission. If a negative pressure room is not available, 450 a private room with a closed door is recommended. If COVID-19 is suspected, video 451 laryngoscopy is recommended. Viral filters must also be appropriately utilized. Emergency clinicians are experts in airway management and routinely encounter critically ill 457 patients with pre-and post-intubation physiologic challenges associated with adverse events.

Those with a severe metabolic acidosis require maintenance of the minute ventilation to prevent 459 a sudden deterioration in pH. In the case of shock and hypotension, resuscitation prior to 460 induction is the goal, and a shock index of >0.8-0.9 predicts post intubation hypotension. 461

Preceding hypoxemia should be aggressively preoxygenated using NIPPV. Pulmonary 462 hypertension and right ventricle failure present complex physiologic challenges; the major goal 463 is to avoid systemic hypotension or a sudden increase in PVR from hypercapnia or hypoxemia. 464

Obstructive lung disease presents a risk of hemodynamic collapse from high intrathoracic 465 pressure caused by air-trapping, and patients require prolonged expiratory times with slow 466 respiratory rate while mechanically ventilated. These considerations can assist emergency 467 clinicians in optimizing the patient during and after intubation attempts. 468 469 470 Table 1 . Pearls and pitfalls in the management of high-risk airways.

High-Risk Airway

Airway Management by US and Canadian 472 Emergency Medicine Residents: A Multicenter Analysis of More Than 6,000 Endotracheal 473 Intubation Attempts

Emergency Airway Management: A Multi-476

Center Report of 8937 Emergency Department Intubations

Airway Management in the Emergency 479 Department: A One-Year Study of 610 Tracheal Intubations

Techniques, Success, and Adverse Events of 482 Emergency Department Adult Intubations

The Importance of First Pass Success When 485 Performing Orotracheal Intubation in the Emergency Department

Complications of endotracheal 488 intubation in the critically ill

Death and Other Complications of Emergency 491

Airway Management in Critically Ill Adults A Prospective Investigation of 297 Tracheal 492 Intubations

Clinical practice and risk factors for immediate 494 complications of endotracheal intubation in the intensive care unit: A prospective, multiple-495 center study*

The who, where, and what of rapid sequence intubation: 498 prospective observational study of emergency RSI outside the operating theatre

Incidence and factors associated with cardiac 501 arrest complicating emergency airway management

The frequency and significance of 504 postintubation hypotension during emergency airway management

The Physiologically 507 Difficult Airway

Cardiac Arrest and Mortality Related to Intubation 510 Procedure in Critically Ill Adult Patients: A Multicenter Cohort Study

Delayed Sequence 513 Intubation: A Prospective Observational Study

Preoxygenation, Reoxygenation, and Delayed Sequence Intubation in the 516 Emergency Department

Effectiveness of Apneic Oxygenation 519 During Intubation: A Systematic Review and Meta-Analysis

Predictors of the complication 522 of postintubation hypotension during emergency airway management

Physiologically difficult airway in critically ill patients: winning the race 525 between haemoglobin desaturation and tracheal intubation

Ventilatory Failure: Can You Sustain What You Need?

530 Comparison of end-tidal carbon dioxide and arterial blood bicarbonate levels in patients with 531 metabolic acidosis referred to emergency medicine

Treatment of metabolic acidosis

Sodium Bicarbonate Therapy in Patients with Metabolic Acidosis

Sodium bicarbonate therapy for patients with severe 540 metabolic acidaemia in the intensive care unit (BICAR-ICU): a multicentre, open-label, 541 randomised controlled, phase 3 trial

Avoiding circulatory complications during endotracheal intubation and 544 initiation of positive pressure ventilation

Alternatives to Rapid Sequence Intubation: 547 Contemporary Airway Management with Ketamine

Difficult Airway Society guidelines for awake 550 tracheal intubation (ATI) in adults. Anaesthesia

Bag-Mask Ventilation during Tracheal Intubation of 552

Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department

Lung-protective ventilation initiated in the 556 emergency department (LOV-ED): a quasi-experimental, before-after trial

Physiological approach to assessment of acid-base 559 disturbances

Capnography in the Emergency Department

Evaluation of the incidence, risk factors, and 563 impact on patient outcomes of postintubation hemodynamic instability

Postintubation hypotension in intensive care unit 566 patients: A multicenter cohort study

The incidence and risk factors for cardiac arrest during emergency tracheal 569 intubation: a justification for incorporating the ASA Guidelines in the remote location

Co-induction with a vasopressor "chaser" to mitigate propofol-572 induced hypotension when intubating critically ill/frail patients-A questionable practice

Timing Resuscitation Sequence Intubation for Critically Ill Patients

Effect of a fluid bolus on cardiovascular collapse 579 among critically ill adults undergoing tracheal intubation (PrePARE): a randomised 580 controlled trial

Pharmacotherapy Update on the Use of 583 Vasopressors and Inotropes in the Intensive Care Unit

Influence of 586 phenylephrine bolus administration on left ventricular filling dynamics in patients with 587 coronary artery disease and patients with valvular aortic stenosis

Safety Considerations and Guideline-Based 590

Safe Use Recommendations for "Bolus-Dose" Vasopressors in the Emergency Department

Hemodynamic Response After Rapid Sequence 593 Induction With Ketamine in Out-of-Hospital Patients at Risk of Shock as Defined by the 594 Shock Index

Assessment and Resuscitation in Trauma Management

Airway Management in Trauma

Airway Management in Critically Ill Patients

Rapid sequence induction in the emergency 603 department: induction drug and outcome of patients admitted to the intensive care unit

Increased incidence of clinical hypotension 606 with etomidate compared to ketamine for intubation in septic patients: A propensity matched 607 analysis

Etomidate versus ketamine for rapid sequence 609 intubation in acutely ill patients: a multicentre randomised controlled trial

Cardiovascular effects of anesthetic induction 612 with ketamine

Ventilator Strategies 614 and Rescue Therapies for Management of Acute Respiratory Failure in the Emergency 615

Non invasive ventilation for the management of acute hypercapnic respiratory failure due to 618 exacerbation of chronic obstructive pulmonary disease. Cochrane Database Syst Rev

Management of COPD exacerbations: 621 a

Outcomes of Noninvasive and Invasive Ventilation 624 in Patients Hospitalized with Asthma Exacerbation

Mechanical Ventilation for Severe Asthma

Inflation pressure, gastric insufflation and rapid sequence 629 induction

Ketamine in status asthmaticus: A review

Ketamine in the treatment of bronchospasm during 634 mechanical ventilation

Right Ventricular Function in Cardiovascular 637

Clinical Importance, and Management of Right 638 Ventricular Failure

Pulmonary Hypertension and Right Ventricular 641 Failure in Emergency Medicine

Right Ventricular Function in 644

Anatomy, Physiology, Aging, and Functional Assessment of 645 the Right Ventricle

Ventricular interdependence: significant left ventricular 648 contributions to right ventricular systolic function

Physiologic Approach to Mechanical 651 Ventilation in Right Ventricular Failure

Diagnosis, Treatment and Follow Up of 654

Acute Pulmonary Embolism: Consensus Practice from the PERT Consortium

Risk Factors for and Prediction of Hypoxemia 657 during Tracheal Intubation of Critically Ill Adults

Preoxygenation is more effective in the 25 degrees 660 head-up position than in the supine position in severely obese patients: a randomized 661 controlled study

Pre-oxygenation in the obese patient: 664 effects of position on tolerance to apnoea

Optimizing preoxygenation in adults

Noninvasive ventilation improves preoxygenation 669 before intubation of hypoxic patients

Non-invasive ventilation versus high-flow nasal 672 cannula oxygen therapy with apnoeic oxygenation for preoxygenation before intubation of 673 patients with acute hypoxaemic respiratory failure: a randomised, multicentre, open-label 674 trial

Preoxygenation before intubation in adult patients with acute 676 hypoxemic respiratory failure: a network meta-analysis of randomized trials

High-flow nasal cannula oxygen during endotracheal 679 intubation in hypoxemic patients: a randomized controlled clinical trial

High-Flow Nasal Cannula 682 Versus Bag-Valve-Mask for Preoxygenation Before Intubation in Subjects With Hypoxemic 683 Respiratory Failure

Apnoeic oxygenation via high-flow nasal cannula 688 oxygen combined with non-invasive ventilation preoxygenation for intubation in 689 hypoxaemic patients in the intensive care unit: the single-centre, blinded, randomised 690 controlled OPTINIV trial

Why is this topic important? Critically ill patients present several physiologic challenges 696 to emergency clinicians

What does this review attempt to show? This review provides an evidence-based approach 698 to management of the physiologically-challenging airway

What are the key findings? Peri-intubation complications can occur in emergent airways

High risk scenarios including severe metabolic acidosis; shock and hypotension; obstructive 701 lung disease; pulmonary hypertension, right ventricle failure, and pulmonary embolism; and 702 severe hypoxemia require consideration of several factors to optimize patient outcomes

How is patient care impacted? Knowledge of these scenarios can improve management of 704 challenging physiologic scenarios

Metabolic Acidosis