Reviving older drugs to deal with anesthesia drug shortages.

Abstract

Anesthesiologists across Canada are still mourning the withdrawal of preservative-free chloroprocaine from the Canadian market in 2012. This withdrawal occurred due to a combination of corporate decisions by its manufacturer as well as a shortage of the raw materials required to produce chloroprocaine. Although not approved for intrathecal use in the United States, chloroprocaine is available for use in Europe (Sintetica S.A., Mendrisio, Switzerland; 10 mg mL and an ever-increasing number of studies have been undertaken to establish the optimal dose to provide a safe, reliable, and short-lived subarachnoid blockade. Nevertheless, difficulty in obtaining regulatory approval to study intrathecal chloroprocaine has made it very challenging to perform adequately powered randomized clinical trials in the USA and Canada. Without chloroprocaine, we must consider ‘‘revival of old local anesthetics for spinal anesthesia in ambulatory surgery’’ 6 in order to maximize efficiency for outpatient surgery. Prilocaine, an intermediate-acting local anesthetic, was first used in 1965, while ropivacaine, a long-acting agent, was released in 1996. Until now, there has been a lack of studies comparing the intrathecal administration of these two drugs in terms of time to motor block resolution, postanesthesia care unit (PACU) discharge time, speed of onset, time to voiding, or adverse effects. This lack of data has now been addressed. In this issue of the Journal, Aguirre et al. compare hyperbaric 2% prilocaine 60 mg with 0.4% plain ropivacaine 12 mg for same-day discharge arthroscopic knee surgery. The primary outcome, median time to motor block resolution, was significantly shorter in the 2% prilocaine group than in the 0.4% ropivacaine group (180 min vs 240 min, respectively; mean difference, 60 min; 95% confidence interval [CI] of difference, 23 to 97; P 0.036). Nevertheless, this did not translate to a difference in PACU discharge time (330 min for prilocaine vs 335 min for ropivacaine; mean difference, 5 min; 95% CI, -25 to 35; P = 0.330) as patients were required to void prior to discharge. No neurological sequelae were present in either group after follow-up for 48 hr. The question arises: If the average knee arthroscopy lasts 30-45 min, why would an anesthesiologist choose an anesthetic that lasts at least threefold longer than the duration of surgery? Is prilocaine a reasonable alternative to 35-40 mg of intrathecal chloroprocaine which has a reliable motor offset time of 60 min with an ambulation time of 104 min? 4 The answer is perhaps. With a high prevalence of obstructive sleep apnea and an aging population with many comorbidities, there are strong arguments to continue to provide subarachnoid anesthesia for our patients. The avoidance of airway manipulation, respiratory depression, and hemodynamic instability favours providing spinal over general anesthesia in a population who may well require prolonged PACU monitoring anyway (by virtue of their comorbidities). Many anesthesiologists would choose to sacrifice the desirability of a short PACU stay and utilize, for example, low-dose hyperbaric bupivacaine, accepting that there is a wide variation in motor offset time and tolerating J. J. Szerb, MD (&) Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Victoria General Site, 10 West Victoria, 1276 South Park St., Halifax, NS B3H 2Y9, Canada e-mail: szerbj@ns.sympatico.ca A http://www.ashp.org/menu/DrugShortages/CurrentShortages/ Bulletin.aspx?id=849.