Does Induction Agent Choice Affect post intubation hypotension?

Post intubation hypotension was defined as any of the following within 15 min of intubation. These parameters were taken from the anaesthetic literature:

1. A systolic blood pressure (SBP) <100 mmHg, or

2. A mean arterial pressure of less than 70 mmHg, or

3. Reduction in mean arterial pressure of more than 20%.

 Secondary Outcomes

• Percentage reduction of SBP within 15 min of RSI,
• Fluid bolus requirement within 15 min of RSI,
• Vasopressor requirement within the first 15 min of RSI,
• Cardiac arrest within 15 min of RSI,
• Procedural success
• Patient mortality during the admission.

What They Found

• 87% of intubations were performed by emergency specialists, the rest being perfomed by intensivists and anaesthetists.
• 54% (63/117) of patients where Ketamine alone was used became hypotensive.
• 52% (69/132) of patients where Propofol alone was used became hypotensive.
• 58% (7/12) of patients where Ketamine and Propofol were both used became hypotensive.
• 0% (0/5) patients where Thiopentone was used became hypotensive.
• 35% required vasopressors within 15 minutes of induction.

In terms of secondary outcomes, below is a table from the study, which in summary showed that:

• Age > 60 and a Shock Index of > 1.0 were significantly associated with a need for vasopressors
• The doses of the induction agents were not predictive of the reduction in systolic blood pressure.
• Cardiac arrest occurred more frequently in patients with a pre-intubation Shock Index of > 1.0, although the absolute numbers were low.

My Take On This

• This is a retrospective study in a single centre and is thus potentially prone to selection bias eg.,  the sickest patients may have been given Ketamine, because they had a lower blood pressure.

• Patients receiving Ketamine did in fact have a lower pre-induction blood pressure than those receiving propofol (127 mmHg vs 141 mmHg).

• This study will not change my practice. I will still be using Ketamine, as this study didn't show that it was inferior to propofol, and there may be some indication that it was superior.

• The key will be to maximise the pre-intubation resuscitation of patients, especially focusing on those with a Shock Index of > 1.0. I will aim to treat hypotension and aim for a systolic blood pressure of 120-140mmHg, I will correct, as best I can, hypoxaemia, hypotension, metabolic acidosis and right ventricular failure.