There are a variety of physiologic responses to intubation or vocal cord stimulation. The two most discussed responses include an increase in intracranial pressure and a rise in systolic blood pressure (pressor response). No one has adequately studied the dynamics of intracranial pressure (ICP) in the acutely head-injured patient who is intubated in the ED. There are a few studies regarding intubated patients in the intensive care unit who have ICP monitors in place. Endotracheal suctioning can increase the ICP for up to two minutes in these patients.⁵ Increases in blood pressure generally range from 14 mmHg to 48 mmHg (average increase, approximately 30 mmHg).⁶

The literature regarding this rise in intracranial and systolic pressure is confusing and contradictory. Studies include a smorgasbord of human, pig, rat, and feline subjects using a variety of agents, often in dosages and combinations not used in clinical practice. Despite hundreds of papers on the topic, the bottom line remains: No researcher has clearly demonstrated the clinical importance of the intracranial or pressor response to intubation, much less the benefit of blocking them with drugs.

Other physiologic responses to intubation include dysrhythmias and tachycardia. Some of these are related to pharmacologic adjuvants, such as succinylcholineinduced bradycardia in children.