Antireflux valves in intravenous opioid analgesia: are they necessary?

A study was conducted in patients receiving intravenous opioid analgesia to determine the incidence and degree of retrograde flow along the parallel gravity-driven infusion line. From 1187 hours of observations retrograde flow was found in 2.5% of the total time. In 70% of these cases this was equivalent to less than 1 mg of pethidine and in 96% this was equivalent to less than 5 mg of pethidine. The need for routine use of antireflux valves during intravenous opioid analgesia is therefore questioned.