[Heart rate response to intravenous atropine during cervical and lumbar epidural anesthesia]

The authors evaluated the effect of cervical and lumbar epidural anesthesia on the heart rate response to intravenous atropine 0.01 mg.kg-1 in conscious humans with cervical epidural anesthesia (n = 40), with lumbar epidural anesthesia (n = 15) and without epidural anesthesia (n = 25). During cervical and lumbar epidural anesthesia using 1.5% lidocaine, levels of loss of cold sensation were C3-T7 and T7-S1, respectively. Heart rate increased by 14 +/- 10% (mean +/- SD) and 20 +/- 14% after intravenous atropine 0.01 mg.kg-1 in the patients with cervical and lumbar epidural anesthesia, respectively. These magnitudes of positive chronotropic effects were significantly less as compared with those in the patients without epidural anesthesia (32 +/- 11%). Nine of 40 patients (23%) with cervical epidural anesthesia showed heart rate increases of less than 3 beats.min-1 following atropine 0.01 mg.kg-1. And 30 of 40 patients (75%) required supplementary atropine 0.01 mg.kg-1 to increase heart rate for more than 20 beats.min-1 from baseline values. The present study suggests that the heart rate response to intravenous atropine is blunted in patients during cervical and lumbar epidural anesthesia, and that a larger dose of intravenous atropine may be required to accelerate the heart rate in most patients during cervical epidural anesthesia.