Increased cerebral and decreased femoral artery blood flow velocities during direct laryngoscopy and tracheal intubation.

Direct laryngoscopy and tracheal intubation may be associated with increased heart rate, arterial blood pressure, cardiac index, and systemic vascular resistance. These responses have been attributed to sympathoadrenal stimulation. However, the studies measuring distribution of blood flow to various organs are limited. We prospectively evaluated blood flow velocities in the common carotid, middle cerebral, and femoral arteries before induction of anesthesia, after induction but before direct laryngoscopy, at the conclusion of direct laryngoscopy and tracheal intubation, and 3 min after tracheal intubation in 13 adult patients. Direct laryngoscopy and tracheal intubation produced increases in the heart rate (from 76 +/- 13 to 91 +/- 10 bpm; chi +/- SD), systolic blood pressure (from 168 +/- 20 to 206 +/- 21 mmHg), common carotid and middle cerebral blood flow velocities, but produced decreases in femoral artery blood flow velocities. Common carotid artery blood flow velocity increased from 49.4 +/- 12.5 cm/s to 65.2 +/- 20.7 cm/s (P < 0.05) at the conclusion of tracheal intubation. Middle cerebral artery blood flow velocity, which could be measured only in seven patients due to technical difficulties secondary to movement during laryngoscopy, increased from 62.4 +/- 20.5 cm/s to 78.0 +/- 27.7 cm/s (P < 0.05). In contrast, femoral artery blood flow velocity decreased from 107.6 +/- 37.8 cm/s to 76.8 +/- 28.6 cm/s (P < 0.05). These responses suggest that the hypertensive response due to direct laryngoscopy and tracheal intubation is associated with redistribution of blood flow in the body.