Effects of oral premedication with tramadol, pregabalin or clonidine on shivering after spinal anaesthesia in patients undergoing hysteroscopic procedures.

Background: Shivering is a common complication of neuraxial anaesthesia. We compared the efficacy of tramadol, clonidine and pregabalin in preventing post-spinal anaes-thesia shivering in hysteroscopic procedures.
Methods: A prospective, randomized, triple-blind, controlled clinical trial involving 120 ASA I-II women, aged 18-60 years. The patients were randomly allocated to receive either oral clonidine 0.2 mg (group C), tramadol 100 mg (group T), pregabalin 150 mg (group P) or placebo (group O) 90 minutes before spinal anaesthesia. The body tempe-rature was monitored at the forehead and tympanic membrane. The primary outcome was the occurrence of perioperative shivering. The secondary outcomes were the side effects and meperidine requirements to treat shivering.
Results: All groups had comparable demographic data. Group C showed the lowest incidence, severity and number of intraoperative and postoperative shivering attacks. The time to the first shivering attack was significantly longer in group C than the other groups and in group T than groups P and O. The severity of shivering attacks was comparable among groups C, T and P while being significantly lower than group O. Meperidine requirements were significantly lower in group C. Groups C, T and P had a significantly higher sedation score than group O. The incidences of dizziness, nausea and vomiting were highest in group T.
Conclusions: Tramadol, pregabalin and clonidine seem to be effective oral premedications to reduce the incidence, frequency and severity of post-spinal shivering but clonidine proved to be more effective and tolerable.