Letter to the editor regarding ‘Use of intrathecal chloroprocaine for ambulatory perianal procedures in the prone jackknife position: a retrospective single-center experience’

Abstract

To the editor We read with considerable interest the article by Sanoja and colleagues concerning the use of intrathecal chloroprocaine for ambulatory perianal procedures in the prone jackknife position. We encourage the analysis of spinal chloroprocaine for short surgical procedures and therefore congratulate the authors on this publication. We would like to make a few comments regarding the methodology and conclusions. The authors described their experiences with intrathecal chloroprocaine for perianal procedures within a study population of 33 patients, divided in a subgroup of 14 patients receiving 50 mg and a subgroup receiving a lower dose (whereby 14 patients received 40 mg). They described that there appeared to be no clinical relevant differences in recovery discharge times between the higher and lower doses. We sincerely doubt whether such statements can be made on the basis of this retrospective analysis in a very small population without sample size calculations and power analysis. Furthermore, the authors considered a dose of 40 mg to be appropriate for surgeries lasting less than 30 min while also allowing for timely block regression and that discharge readiness did not decrease with a dose reduction. We recently conducted a doubleblind randomized prospective trial comparing 40 mg chloroprocaine with 40 mg prilocaine for spinal anesthesia in ambulatory knee arthroscopy. In the chloroprocaine arm of this cohort (75 patients), 97.3% had a sufficient block, and the peak sensory block of T9 would give some room for a dose reduction in our opinion. In a followup study, we analyzed the ED90 of intrathecal 2chloroprocaine 1% in ambulatory knee arthroscopy via a biased coin upanddown trial. The ED90 was estimated to be 27.8 mg, suggesting that a 28 mg dose is adequate for knee arthroscopy (40 patients, data presented at the American Society of Anesthesiologists Annual Meeting, October 2020, Abstract A3033). Both motor block and sensory block offset time, as the hospital discharge time, were substantially shorter compared with the 40 mg arm in the first mentioned study. Given the fact that the necessary sensory block height of spinal anesthesia for perianal procedures is far less than for knee arthroscopy, we expect that a dose reduction (ie, less than 40 mg) for perianal procedures would be appropriate and, based on our findings of both arthroscopy studies, probably will shorten the hospital discharge time. Finally, there was a substantial difference in vasopressor use between the <50 mg group (8/19) and the 50 mg group (2/14) in the study population of Sanoja et al. One would expect that a higher dose will result in an increased block height with more hemodynamic consequences requiring more vasopressor drugs, but this seems to be the opposite. It is very likely that this observation could be explained by other factors, like, for instance, interdoctor variation regarding the use of vasopressor drugs. We strongly agree with the authors that more randomized studies with defined discharge protocols are needed to establish the benefit of 1% chloroprocaine over lower doses of other commonly used local anesthetics.