[Pressor responses to inhalation of isoflurane during induction of anesthesia and subsequent tracheal intubation].

BACKGROUND

Marked hypertension may occur during induction of isoflurane anesthesia. The hemodynamic responses to mask ventilation using isoflurane and subsequent tracheal intubation were evaluated.

METHODS

In 26 ASA physical status I patients, anesthesia was induced with thiamylal followed by mask ventilation with 0.5% isoflurane in oxygen. Isoflurane concentration was increased to 4% in 2 min, and the trachea was intubated after 3 min of ventilation with 4% isoflurane. Blood pressure (BP) and heart rate (HR) were recorded every minute from induction of anesthesia.

RESULTS

In 9 patients, systolic BP before intubation increased significantly to more than 10 mmHg (26 +/- 16%) compared before induction, but decreased (-7 +/- 7%) in the others after a transient slight increase. Tracheal intubation induced a marked increase in BP in all patients, but there was a negative correlation between the isoflurane-induced increase in BP and that induced by intubation. Tachycardia was seen in all patients regardless of the values of BP.

CONCLUSIONS

Inhalation of 4% isoflurane during induction of anesthesia induces lasting hypertension in some patients and this pressor response has no relation with the tachycardia. Tracheal intubation induced a larger increase in blood pressure in the isoflurane-induced hypertensive patients, but the increase is within the limits of that seen in patients without pressor response to isoflurane.