Gb. Drummond et Nmm. Elfarhan, DO ANXIETY OR HYPOCAPNIA PREDISPOSE TO APNEA AFTER INDUCTION OF ANESTHESIA, British Journal of Anaesthesia, 78(2), 1997, pp. 153-156
We have studied the incidence of apnoea after induction of anaesthesia
in patients allocated randomly to receive a standardized dose of eith
er propofol or etomidate. We measured anxiety before operation with a
standard questionnaire and end-tidal carbon dioxide concentration from
a mask during breathing 35% oxygen, before induction of anaesthesia.
Respiration was measured by pneumotachograph and impedance pneumograph
. There was no significant relationship between anxiety score and end-
tidal carbon dioxide concentration before operation. Patients given pr
opofol (n=26) received a median dose of 157 mg over 70 s, and 17 becam
e apnoeic (median duration 24 s, quartile values 0, 76). Apnoea was mo
re severe in patients whose preoperative end-tidal carbon dioxide valu
e was less than the median value (median duration of apnoea 61 s compa
red with 10 s; P<0.05). Patients given etomidate (n=25) received 16.2
mg in 57 s, which was a significantly smaller fraction of the calculat
ed dose requirement, and had significantly less apnoea: eight became a
pnoeic (median duration 0 s, quartile values 0, 23 s). There was no re
lationship between apnoea and end-tidal carbon dioxide concentration i
n these patients. Anxiety did not relate to the incidence of apnoea wi
th either induction agent. We conclude that apnoea after induction of
anaesthesia with propofol is more likely if hypocapnia is present but
we could not relate apnoea or hypocapnia to anxiety in the ward before
operation.