Intubating the critically ill patient presents a unique set of challenges. The process of intubation, including the induction-associated sympatholysis and the change from spontaneous, negative pressure ventilation (which increases venous return and preload) to placing someone on the ventilator and adding positive pressure ventilation (which decreases venous return and preload) can have drastic effects on the hemodynamics of patients already in shock.
Therefore, we must always remember to:
Resuscitate before you intubate
Who is at increased risk of decompensation and cardiac arrest?
We are able to predict who is at risk for peri-intubation decompensation by evaluating the shock index (SI). The shock index prior to RSI was found to be independently associated with cardiac arrest. The shock index is the heart rate divided by the systolic blood pressure. A pre-RSI shock index ≥ 0.9 has been associated with cardiac arrest.
Shock Index = HR/SBP
Shock Index ≥ 0.9 = associated with cardiac arrest
The Evidence
2013 article published in Resuscitation by Heffner et. al. looked at 410 patients who underwent endotracheal intubation in a large, urban emergency department over a one-year period. They excluded patients under the age of 18 and patients, patients who were already in cardiac arrest prior to arrival, and patients who were in cardiac arrest at the onset of intubation.
RSI coupled with direct laryngoscopy was the standard approach to patients not in CA during the study period. The study found that cardiac arrest was more common in patients experiencing pre-intubation hypotension (12% vs. 3%; p < 0.002). Pre-intubation shock index (SI) was independently associated with cardiac arrest.
The Debrief
Shock Index = HR/SBP
Shock Index ≥ 0.9 = associated with cardiac arrest
- Use the pre-RSI shock index to help identify critically ill patients who are at risk for cardiac arrest following endotracheal intubation.
Good and educative.