There is some evidence which suggests that the use of Irish stick weapons may have evolved in a progression from a reliance on long spears and wattles, to shorter spears and wattles, to the shillelagh, alpeen, blackthorn (walking-stick) and short cudgel.
Moreover, most of the associated drugs fatalities including tramadol have been reported with other central nervous system (CNS) depressants, particularly benzodiazepine [9], [10], [11], [13] and [14]. In certain cases, benzodiazepine levels were in the therapeutic range or slightly higher.
Tramadol IS a synthetic opioid. It is considered an Opioid Analgesic and does work like some SNRI antidepressants, which can (very rarely!) lead to serotonin syndrome. You are taking so little of Tramadol that I wouldn't be the least bit worried.