Techniques and proceduresPreoxygenation, Reoxygenation, and Delayed Sequence Intubation in the Emergency Department
Introduction
Conventional preoxygenation techniques provide safe intubation conditions for a majority of emergency airways. However, in a subset of patients, these techniques will lead to inadequate preoxygenation and fail to prevent desaturation. To safely intubate this group, an understanding of the physiology of oxygenation is essential to allow for optimal intubating conditions. This knowledge can then be applied at the bedside in the care of high-risk patients. The goal of this work is to translate the tenets of physiology and the most recent literature to allow the safest possible intubation of critically ill patients.
Section snippets
The Pathophysiology of Hypoxemia
To understand oxygenation, it is essential to understand the causes of hypoxemia. These causes are inadequate alveolar oxygenation (low environmental oxygen pressure or alveolar hypoventilation), diffusion abnormalities, dead space (high ventilation, low perfusion [V/Q] mismatch), low V/Q mismatch, shunt, and low venous blood saturation. In the Emergency Department (ED) patient placed on ≥ 0.4 fraction-inspired oxygen (fiO2), all of these problems have inconsequential effects on oxygenation
Reoxygenation
If the first pass at intubation fails and the patient's oxygen saturation drops below 90–95%, reoxygenation is required before any further intubation attempts. The standard method for reoxygenation is to ventilate the patient with a BVM apparatus attached to high-flow O2. Skilled practitioners will also place an oropharyngeal airway and, if there is any difficulty, nasopharyngeal airways as well. Even in skilled hands, this method can be problematic; when performed by a novice, it can be deadly.
Delayed Sequence Intubation
In some circumstances, the patients who most desperately require preoxygenation impede its provision. Hypoxia and hypercapnia can lead to delirium, causing these patients to rip off their non-rebreather or NIV masks. This delirium, combined with the oxygen desaturation on the monitor, often leads to precipitous attempts at intubation without adequate preoxygenation. Thanks to the availability of novel pharmacologic agents, another pathway exists to manage these patients.
Standard RSI consists of
Conclusion
Conventional preoxygenation techniques provide safe intubation conditions for a majority of emergency airways. However, in a subset of high-risk patients, these techniques will lead to inadequate preoxygenation and fail to prevent desaturation. To safely intubate this group, meticulous attention must be paid to optimizing preoxygenation, preventing deoxygenation and, if necessary, providing reoxygenation in a controlled manner. Future research is needed to delineate optimal timing, dosing, and
References (33)
- et al.
Noninvasive positive-pressure ventilation vs. conventional oxygen supplementation in hypoxemic patients undergoing diagnostic bronchoscopy
Chest
(2002) - et al.
Inflation pressure, gastric insufflation and rapid sequence induction
Br J Anaesth
(1987) - et al.
Do we hyperventilate cardiac arrest patients?
Resuscitation
(2007) - et al.
Effects of face mask ventilation in apneic patients with a resuscitation ventilator in comparison with a bag-valve-mask
J Emerg Med
(2006) - et al.
Dexmedetomidine as sole sedative for awake intubation in management of the critical airway
J Clin Anesth
(2007) - et al.
Dexmedetomidine for conscious sedation in difficult awake fiberoptic intubation cases
J Clin Anesth
(2007) - et al.
Dexmedetomidine infusion for sedation during fiberoptic intubation: a report of three cases
J Clin Anesth
(2004) - et al.
The increase in total and unbound propofol concentrations during accidental hemorrhagic shock in patients undergoing liver transplantation
Anesth Analg
(2006) - et al.
Influence of hemorrhagic shock followed by crystalloid resuscitation on propofol: a pharmacokinetic and pharmacodynamic analysis
Anesthesiology
(2004) - et al.
Changes in onset time of rocuronium in patients pretreated with ephedrine and esmolol—the role of cardiac output
Acta Anaesthesiol Scand
(2003)