INCREASED CEREBRAL AND DECREASED FEMORAL-ARTERY BLOOD-FLOW VELOCITIESDURING DIRECT LARYNGOSCOPY AND TRACHEAL INTUBATION

Direct laryngoscopy and tracheal intubation may be associated with inc reased heart rate, arterial blood pressure, cardiac index, and systemi c vascular resistance. These responses have been attributed to sympath oadrenal stimulation. However, the studies measuring distribution of b lood flow to various organs are limited. We prospectively evaluated bl ood flow velocities in the common carotid, middle cerebral, and femora l arteries before induction of anesthesia, after induction but before direct laryngoscopy, at the conclusion of direct laryngoscopy and trac heal intubation, and 3 min after tracheal intubation in 13 adult patie nts. Direct laryngoscopy and tracheal intubation produced increases in the heart rate (from 76 +/- 13 to 91 +/- 10 bpm; X +/- SD), systolic blood pressure (from 168 +/- 20 to 206 +/- 21 mm Hg), common carotid a nd middle cerebral blood flow velocities, but produced decreases in fe moral artery blood flow velocities. Common carotid artery blood flow v elocity 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 du e 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). I n 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 bod y.