Oxygen Dissociation Curve

 

Peri-intubation oxygenation and maintenance of adequate alveolar saturation is vital to patient safety.  Desaturation below 70% during intubation places patients at risk for hemodynamic decompensation, dysrhythmias, cerebral ischemia, and death.  The Emergency Physician must secure an endotracheal tube rapidly and prevent critical hypoxia.
Important considerations include:

1.  Choice of agent: Studies have shown Rocuronium prolongs time to desaturation when compared w/ Succinylcholine and should be used in patients at risk of immediate desaturation such as those w/ severe sepsis/obesity/hypoxia.

2.  Pre-oxygenation: Patients should be placed on face-mask (“non-rebreather”) with O2 at maximum, (i.e. past the 15L until you can no longer turn knob and you can actively hear the sound of oxygen from the wall).  This is because many emergency department “non-rebreather” masks lack one-way valves in all of their ports and therefore provide only 60-70% FIO2 at 15L.

3.  Preparation: For Apneic oxygenation w/ nasal cannula set at 15L which will remain on the patient until completion of procedure and the patient is on the vent and tube placement has been confirmed w/ capnography.  This has consistently been shown to prolong time to desaturation.

4.  Position: Patients should be sitting up >30 degrees during pre-oxygenation and up until the very last minute i.e. medications given to maximize alveolar oxygenation and decrease risk of aspiraton. Once placed in supine position patients should have head elevated forward until their ears are at the level of sternum.

5.  What if there is desaturation?: If the patient’s saturation drops <93% at any time during the procedure it is important to place an LMA, inflate the cuff, and bag the patient w/ vag balve (again set at maximum from wall >15L) until saturation returns to 100%.  The use of LMA will reduce (but not prevent) aspiration and make ventilation easier during this step. The reason for making this decision immediately once saturation reaches <93% is because of the hemoglobin dissociation curves.  It is known that once patient’s saturation drops below 90% they have a precipitous drop thereafter.

6.  Once saturation is back to 100%, repeat intubation attempt. Consider passing bougie through LMA feeling for tracheal rings and palpating sternal notch and then performing direct laryngoscopy while passing ET tube.

 

 

Jaber S et al., An Intervention to Decrease Complications Related to Endotracheal Intubation in the Intensive Care Unit: A Prospective, Multi-Center Study., Intensive Care Med., 2010: 36;248-255

Levitan, RM., NO DESAT! Nasal Oxygen During Efforts Securing a Tube., Emergency Physicians Monthly., 2010.

Tang Li et al., Desaturation Following Rapid Sequence Intubation using Succinylcholine versus Rocuronium in Overweight Patients., Acta Anaesthesiol Scand., 2011: 55;203-208

Weingart, SD and Levitan, RM., Preoxygenation and Prevention of Desaturation During Emergency Airway Management., Annals of Emergency Medicine., 2011

Davis, DP et al., Rate of Decline in Oxygen Saturation at Various Pulse Oximetry Values with Prehospital Rapid Sequence Intubation., Prehosp Emerg Care., 2008: 12;46-51