ABSTRACT
BACKGROUND: Clonidine, an alpha-agonist has been postulated to produce analgesia centrally by stimulating the post-synaptic activity of norepinephrine through receptors distinct from opioid receptors and peripherally through a mechanism similar to local anesthetics. It has been suggested that the use of a combination of local anesthetics and clonidine both at lower doses may be effective in providing adequate analgesia at the same time minimizing the deleterious side effects of each drug when used alone at higher doses. The objective of the study was the determination of the minimum dosage of clonidine in combination with bupivacaine necessary for epidural administration that would provide optimal intraoperative and postoperative analgesia with the least occurrence of side effects such as hypotension and bradycardia. METHODOLOGY: One hundred randomly selected, healthy ASA l and 2 gynecologic patients undergoing lower abdominal surgery under epidural anesthesia were given bupivacaine 0.5 percent epidurally compounded with either saline as placebo (Group 1), or clonidine in variable doses: 0.5 ug/kg (Group 2), 1.0 ug/kg (Group 3), and 1.5 ug/kg (Group 4) in a randomized, double-blind fashion. The vital signs were noted every 5 minutes. Analgesia was monitored and recorded using the Visual Analog Scale (VAS), Verbal Rate Scoring and the systemic indicators of pain perception (SBP 30 min Hg increase from baseline or heart rate 20 percent from baseline). A top-up dose of Lidocaine 2 percent was given with systemic indications of pain perception noted intraoperatively or rescue doses of opioids were given when the systemic indications of pain perception were noted at the post anesthesia care unit, upon which data collection was terminated Eighty two patients completed the course of data collection while eighteen were dropped out because of sacral sparing, retraction pain and extension of incision. The statistical tool utilized to test significant differences between the groups was the Kruskal-Wallis Analysis of Variance test and the Partitioned Chi-square test. RESULTS: There is prolongation in the duration of analgesia with incremental increase in clonidine dose. Hypotension occurred even without the addition of clonidine with higher incidence as the dose of clonidine increased. The least side effects occurred with doses of clonidine between 0.5 and 1.0 ug/kg. CONCLUSION: The optimal dosage of clonidine for intraoperative analgesia that would extend to the postoperative period in Filipino women would fall between 0.5 to 1.0 ug/kg. (Author)