We use succinylcholine in RSI is for the Cannot-Intubate cannot-ventilato scenarios, where we expect the patients’ spontaneous ventilation to recover before we get in serious trouble. A study by Heier from Anesthesiology 2001 demonstrates how that is not the case. This is an old study, but nevertheless a good reference to have.

The study
Twelve healthy volunteers were preoxygenated then given an intubating dose of 5mg/kg thiopenthal and 1mg/kg succinylcholine.

After giving the induction doses Heier et al started not ventilating the patients. The patients weren’t given chin-lift nor ventilated until the SaO2 hit 80%. The duration of apnea was measured.

Note that the face mask was removed after paralysis and the airway remained unsupported. This should realistically simulate the the worst case scenario of  upper airway obstruction, no ventilation and no apnoeic oxygenation.

In six volunteers SaO2 decreased below 95%.
Out of these six four SaO2 decreased below 80%
In three patients chin-lift and assisted ventilations was necessary.

All of the four patients who required intervention were aware at the time of the lowest SaO2. Succinylcholine duration, not thiopental, limits breathing.

Half of the patients suffered from myalgias the next day.

Take-home message
One third of the subjects had significant desaturation.

Remember, these were slim, healthy and preoxygenated volunteers. They were given no other drugs other than thio and sux.

A critically ill patient with other respiratory depressants circulating will not have the margins a healthy test subject has.

Succinylcholine doesn’t guarantee reliable recovery of spontaneous ventilation in a cannot-intubate-cannot-ventilate scenario.

Anesthesiology. 2001 May;94(5):754-9.
‘Hemoglobin desaturation after succinylcholine-induced apnea: a study of the recovery of spontaneous ventilation in healthy volunteers.’
Heier T, Feiner JR, Lin J, Brown R, Caldwell JE.

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