Spinal catheter observer effect and surgical technique

The analgesic efficacy and pharmacokinetics of epidural oxycodone after gynaecological laparotomy: a randomized, double‐blind, double‐dummy comparison with intravenous administration

“…We assume that in the CSF aliquots in the present study, obtained in the spinal canal 10–15 cm caudal to the level of epidural injection, oxycodone should have been more diluted than in the previous study, where the aliquots were obtained adjacent to the epidural oxycodone injection site. Another explanation could be that in our previous study some of the oxycodone injected into the epidural space may have passed into the subarachnoid space via a dural hole around the spinal catheter .…”

“…In another study, epidural oxycodone 0.5 mg·kg −1 ·h −1 after a 4 mg bolus was as effective as epidural morphine 0.25 mg·kg −1 ·h −1 after a 2 mg bolus for the first 72 h after gynaecological surgery. Pain relief with a smaller dose of epidural oxycodone, 0.25 mg·kg −1 ·h −1 after a 2 mg bolus, was a little lower during the first 6 h, but thereafter was similar with a higher dose of oxycodone and with morphine . Inconsistent with our data on oxycodone, epidural fentanyl appeared to be superior to i.v.…”

“…In that study, all patients had both a spinal and epidural catheter. Thus, there was a theoretical potential for epidural oxycodone to diffuse into the subarachnoid space through the breach in the dura . The samples were collected at a random time after the injection of study compounds – no earlier than 1 h after the epidural injection, in order to allow the injection to spread and absorb from the epidural space, and at the latest 4 h after the study compound injection as epidural infusion was started.…”

Population pharmacokinetics of oxycodone in plasma and cerebrospinal fluid after epidural and intravenous administration

“…Second, it has been suggested that spinal catheters used by Kokki et al [5] may have produced some observer effect. Some of the oxycodone administered epidurally may have passed into subarachnoid space via the breachment of dura adjacent to the spinal catheter [33]. However, Piirainen et al [6] later confirmed the superior CSF penetration of epidural vs. IV administration of oxycodone in single lumbar puncture samples.…”