Effects of Oral Clonidine Premedication on Pattern of Heart Rate and Blood Pressure Changes after Neostigmine-Atropine Administration

Injection of Neostigmine-Atropine mixture (N-A) may cause tachycardia, cardiac dysrrythmia and ischemia. This study was designed to determine effects of oral clonidine premedication on pattern and desirability of heart rate (HR) and mean arterial blood pressure (MAP) changes after N-A injection.
In this double blind randomized clinical trial study, 80 adult patients without cardiovascular disorders who were scheduled for elective surgery of orthopedics, gynecology, and laparotomy were assigned to receive approximately 5 g/kg oral clonidine (clonidine group, n=40) 90 minutes before induction of general anaesthesia. At the completion of surgeries, Neostigmine-Atropine mixture was administered and HR and MAP values were measured noninvasively at 1 minute interval for 10 minutes and at the 20th minute after N-A injection. The control group was also compared of 40 patients and were delt exactly the same except clonidine administration.
In clonidine group, absolute values of HR changes after N-A injection were significantly less than that of the control group whereas absolute values of MAP changes were similar in two groups. Changes of HR and MAP after N-A injection were linear in both groups. In clonidine group, slope of HR changes 1 to 10 minutes after NA injection was less than the control group (-2.09 vs. –2.72).
It seems that preoperative clonidine preserves basal parasympathetic nervous activity at the time the study drugs are injected.