In children undergoing inhaled induction of anesthesia with halothane
who suffer bradycardia, submental glossal injection of atropine may re
sult in more rapid onset of vagolysis than traditional intramuscular s
ites. We compared the intervals between injection and onset of heart r
ate acceleration (t(HR) up arrow) after intramuscular injection of atr
opine into the deltoid, vastus lateralis, and glossa in children betwe
en 1 mo and 10 yr of age scheduled for elective surgery. The t(HR) up
arrow after intramuscular injection of atropine into the deltoid, vast
us lateralis, and glossa in children between 1 mo and 10 yr of age sch
eduled for elective surgery. The t(HR) up arrow was determined by meas
uring the interval between atropine injection and the time point at wh
ich the slope of the heart rate curve initially became positive. To en
sure that the drug had taken effect before surgical stimulation, heart
rate observation was continued until it increased at least 5% above b
aseline with evidence of continuing acceleration. Anesthesia was induc
ed in all subjects by mask with nitrous oxide and halothane. After tra
cheal intubation, constant inspired concentrations of the anesthetics
were administered for 3 min. While heart rate was monitored, atropine
(0.02 mg/kg) was injected into one of the three sites. Each patient's
end-tidal anesthetic concentrations were recorded, and minimum alveola
r anesthetic concentrations (MAC) were subsequently calculated and adj
usted for age. The t(HR) up arrow was recorded and averaged for each g
roup. The study groups did not differ by age, weight, end-tidal anesth
etic concentrations, age-adjusted MAC, or heart rate at the time atrop
ine was administered. After submental glossal injection (n = 11), t(HR
) up arrow increase was fastest (3.0 +/- 1.1 min) and was significantl
y faster than that found with deltoid injection (n = 16; 4.4 +/- 1.1 m
in) or vastus lateralis injection (n = 8; 6.4 +/- 2.4 min) (P < 0.05 c
ompared with both). The t(HR) up arrow also differed significantly bet
ween the deltoid and the vastus lateralis (P < 0.05). We conclude that
submental glossal injection of atropine results in a more rapid onset
of vagolysis than injection at traditional intramuscular sites.