Haemodynamic effects of tracheally administered adrenaline in anaesthetised patients

Ten patients undergoing arterial surgery in the leg received a combined general anaesthetic, which included muscle relaxation and intubation of the trachea, and a regional anaesthetic using a lumbar extradural catheter. The radial arterial pressure was measured. Adrenaline 0.1 micrograms.kg-1 was administered intravenously and the heart rate, arterial pressure and oxygen saturation were recorded every 15 s for 10 min. Adrenaline in 5 ml of saline was given into the trachea at 10 min intervals. The first was saline only, and successive injections contained 0.5 micrograms.kg-1, 1 microgram.kg-1, 2 micrograms.kg-1, and 3 micrograms.kg-1 of adrenaline. The mean maximum rise in systolic arterial pressure after adrenaline given intravenously was 30 (SD 11) mmHg, and 15 (SD 16) mmHg after the maximum dose of adrenaline given into the trachea (p < 0.05). The mean systolic arterial pressure was significantly increased between 45 s and 4.5 min after the adrenaline given intravenously, and 2 min after adrenaline given into the trachea. Of seven patients who received adrenaline 3 micrograms.kg-1 into the trachea, six had no noticeable effect and in the other patient, the increase in arterial pressure was less than 90% of the maximum rise after the adrenaline. We conclude that adrenaline given into the trachea is unreliable in humans with very large doses necessary in some patients to produce a clinically useful haemodynamic effect.