Delayed Sequence Intubation

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Author: Timothy Montrief, MD MPH
Jackson Memorial Hospital

Case
A 55-year-old man is brought in to the emergency department by ambulance with a chief complaint of shortness of breath with associated fevers, chills, and productive cough over the past three days. On arrival, he is agitated, anxious, and repeatedly takes off his non-rebreather, stating that he is becoming increasingly dyspneic. He has an oxygen saturation (SpO2) of 85%, is tachycardic to 115 beats per minute, tachypneic to 24 respirations per minute, and has a blood pressure of 145/90 mm Hg.

Questions

• What is the definition of delayed sequence intubation (DSI)?
• What are the indications for DSI?
• What are the medications used for DSI?
• How do you adequately pre-oxygenate a patient? What is the “Triple 15” rule for pre-oxygenation?
• What is the step-by-step algorithm for DSI?
• What are some complications associated with DSI?

Background

• Delayed sequence intubation is procedural sedation, with the procedure being pre-oxygenation, after which the patient can be paralyzed and intubated. The hallmark of DSI is separating the administration of the induction agent and paralytic to allow adequate pre-intubation preparation. This allows the induction agent to be given, followed by a period of pre-oxygenation lasting several minutes, after which the paralytic is administered [1,2]
• As with any procedural sedation, the patient should be calm, spontaneously breathing and protecting their airway.[3]
• DSI may be useful in a select subgroup of patients in whom rapid sequence intubation would likely result in significant hypoxemia because they cannot tolerate pre-oxygenation by other means.
  

Indications for DSI

• There are generally two indications for DSI:[3]
• Patients who are agitated, combative, or cannot tolerate pre-oxygenation (by nasal cannula, non-rebreather mask (NRB), bag-valve-mask (BVM), or non-invasive ventilation)
• The patient requires another procedure before intubation, but the patient is unable to tolerate it (e.g. nasogastric or orogastric tube placement).

DSI Medications

• When choosing an induction agent for DSI, keep in mind these goals:
• The patient must be calmed while spontaneously breathing and protecting their airway.
• Ketamine is the preferred agent for induction in DSI.[1,3]
• It preserves the patient’s airway reflexes and respiratory drive.
• Patients become dissociated at ketamine doses between 1 and 1.5 mg/kg intravenous (IV), but many undesirable side effects, such as hypersalivation, are dose dependent, and ketamine’s dissociative effects are near instantaneous.[2]
• Ketamine should be initially dosed at 1 mg/kg IV, given as a slow IV push over 15-30 seconds to prevent a self-limited, transient episode of apnea.
• An additional dose of 0.5mg/kg IV may be given to achieve complete dissociation if required.
• Other induction agents have been proposed for DSI, including droperidol, dexmedetomidine, and remifentanil. However, these agents lack ketamine’s reassuring safety profile, rapidity of onset, and preservation of both airway reflexes and respiratory drive.[4-6]
• Neuromuscular blockade is important during the intubation phase of DSI, and many agents can be used. Some experts recommend rocuronium (1.2 mg/kg IV) as the ideal neuromuscular blocker because it achieves rapid paralysis, and the absence of fasciculations decreases oxygen consumption.[3]
• Rarely, DSI relieves the need for intubation by alleviating agitation and improving oxygenation.
• In this instance, the neuromuscular blockade may be withheld, and the patient monitored, administering further boluses of induction agent as needed.
• It is important to note that in this instance, the patient is still dissociated, and may need emergent airway management.
• DSI should always be initiated with the end-goal of intubation and securing the airway.

Pre-oxygenation

• Pre-oxygenation during DSI and prior to intubation is required to de-nitrogenate the patient’s lungs, as well as to prevent desaturation during the apneic period after induction and paralysis and throughout intubation.[7]
• In traditional teaching, the patient is pre-oxygenated for three minutes of tidal volume or eight vital capacity breaths with a non-rebreather, supplying a fraction of inspired oxygen (FiO2) of approximately 60%.
• By pre-oxygenating with nasal cannula at 15 liters/minute and a non-rebreather at 15 liters/minute, the FiO2 delivered to the patient is closer to 100%.
• If the patient remains hypoxic (SpO2 ≤95%) on nasal cannula and non-rebreather as described above, add positive pressure ventilation either with:
• A bag-valve-mask with a positive end-expiratory pressure (PEEP) valve, ensuring a good mask seal over the nasal cannula, or
• Placing the patient on continuous positive airway pressure (CPAP), over the nasal cannula, using a maximum of 15 cm water to prevent opening the lower esophageal sphincter and increasing aspiration risk.
• The “Triple 15” rule is a memory aid coined by Dr. Helman and the Emergency Medicine Cases team, consisting of:
• 15 L/min O2 by nasal cannula, plus
• 15 L/min O2 by non-rebreather, and if oxygen saturation is ≤95% then
• 15 cm H2O of CPAP while maintaining nasal cannula.[8]

DSI Algorithm (Fig. 1)

Figure 1. Delayed Sequence Intubation (DSI) Algorithm.[3]

Complications of DSI

• Complications in DSI are divided into four main categories:
• Complications of non-invasive ventilation
• Facial/ocular abrasions
• Claustrophobia/anxiety
• Increased agitation
• Air swallowing with gastric/abdominal distension, potentially leading to vomiting and aspiration
• Hypotension
• Complications of intubation
• Damage to airway or teeth
• Esophageal intubation
• Aspiration
• Bronchospasm
• Hypotension
• Increased Intracranial pressure
• Medication side-effects (ketamine)
• Hyper salivation
• Transient apnea
• Hypertension
• Tachycardia
• Laryngospasm
• Emergence reaction
• Increased risk of aspiration
• DSI goes against the traditional teaching of rapid sequence intubation and may increase aspiration risk.
  

Case Conclusion
The patient was deemed to be an excellent candidate for DSI, and all necessary airway equipment was brought to the bedside. The patient was given 1 mg/kg ketamine IV, and became dissociated, allowing the placement of a non-rebreather mask and nasal cannula at 15 L/min each. The patient was positioned with the head of bed elevated to thirty degrees to facilitate adequate gas exchange, and his oxygen saturation improves to 97%. The patient is pre-oxygenated for three minutes, given rocuronium 1.2 mg/kg IV with the nasal cannula in place for apneic oxygenation, and successfully intubated.

Summary

• DSI is procedural sedation, with the procedure being pre-oxygenation, after which the patient can be paralyzed and intubated.
• DSI may be useful in a select subgroup of patients in whom rapid sequence intubation would inevitably result in significant hypoxemia because they cannot tolerate pre-oxygenation by any other means.
• Use the “Triple 15” rule of pre-oxygenation:
• 15 L/min O2 by nasal cannula, plus
• 15 L/min O2 by non-rebreather, and if oxygen saturation is ≤95% then
• 15 cm H2O of CPAP while maintaining nasal cannula.

References

1. Weingart SD, Trueger NS, Wong N, Scofi J, Singh N, Rudolph SS. Delayed sequence intubation: a prospective observational study. Ann Emerg Med. 2015; 65(4):349-55.

2. Gill S, Edmondson C. Re: preoxygenation, reoxygenation, and delayed sequence intubation in the Emergency Department. J Emerg Med. 2013; 44(5):992-3.

3. Nickson, C. (2016). Delayed sequence intubation. [online] LITFL. Life in the Fast Lane Medical Blog. Available at: https://lifeinthefastlane.com/ccc/delayed-sequence-intubation/ [Accessed 2 Mar. 2018].

4. Aroni F, Iacovidou N, Dontas I, Pourzitaki C, Xanthos T. Pharmacological aspects and potential new clinical applications of ketamine: reevaluation of an old drug. J Clin Pharmacol 2009; 49:957–64.

5. Carollo DS, Nossaman BD, Ramadhyani U. Dexmedetomidine: a review of clinical applications. Curr Opin Anaesthesiol 2008; 21:457–61.

6. Abdelmalak B, Makary L, Hoban J, Doyle DJ. Dexmedetomidine as sole sedative for awake intubation in management of the critical airway. J Clin Anesth 2007; 19:370–3.

7. Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med. 2012; 59(3):165-75.

8. Helman, A. “Episode 54: Preoxygenation and Delayed Sequence Intubation. Emergency Medicine Cases, 25 Nov. 2014, emergencymedicinecases.com/episode-54-weingart-himmel-sessions-preoxygenation-delayed-sequence-intubation/