To the Editor:—
We read with much interest the article of Owen et al. 1These authors found a significant prolongation of labor analgesia when adding clonidine–neostigmine to a “standard” bupivacaine–fentanyl mixture or when adding clonidine alone. Unfortunately, the occurrence of nausea was a major drawback.
In the November 1999 issue of Anesthesiology, Nelson et al. 2from Wake Forest University reported that neostigmine may reduce the ED50value of sufentanil by 25%. A prolongation of analgesia was suggested by an equal duration of pain relief when administering twice the ED50dose of sufentanil (9 μg) alone or twice the ED50dose of sufentanil (6 μg) with 10 μg neostigmine.
However, during the annual Society for Obstetric Anesthesia and Perinatology meeting in Denver, Colorado (May 19–22, 1999), D’Angelo et al. 3(from the same study group) reported no benefit with a similar study design as used in the study from Owen et al. , 1comparing sufentanil–bupivacaine–clonidine with and without 10 μg neostigmine. Because of the high incidence of nausea, even the use of neostigmine was strongly dissuaded. Although we realize that Dr. Owen performed her study with a Turkish group, we are amazed that her findings are in contradiction with those of her colleagues at Wake Forest University.
Dr. Eisenach 4and Dr. D’Angelo, 5who are experts in the use of neuraxial adjuvant drugs, wrote two editorials commenting on two studies mixing clonidine with other epidural mixtures. 6,7Because they were critical about triple or quadruple combinations, it is surprising again to notice that they perform studies with an identical design, even while using the more vulnerable intrathecal route. In both our university hospitals (University Hospital Antwerp, Edegem, Belgium, and Catholic University Hospitals of Louvain, Leuven, Belgium), a standard epidural mixture is prepared by the pharmacist under laminary flow in vials containing 0.125% bupivacaine, 0.75 μg/ml sufentanil, and 1:800,000 epinephrine. This mixture does not contain preservatives and is used not only for epidural, but also for intrathecal analgesia. 8An intrathecal bolus of 2 ml corresponds with 2.5 mg bupivacaine, 1.5 μg sufentanil (less pruritus and limited rostral spread), and 2.5 μg epinephrine. Although this way of preparing drug mixtures may reduce the risk of contamination and mistakes, we do not wish to add other components with undeniable drawbacks. The publication of controversial results and confusing editorials by the same authors or group makes it difficult for the reader to find out what to believe.