Comment on the published article: Accidental injection of succinylcholine into epidural space as a test dose.

Dear Editor,

We read with interest the article “Accidental injection of succinylcholine into epidural space as a test dose” by Toleska et al.[1] The author has reported an accidental injection of succinylcholine as an epidural test dose. Fortunately, the patient did not have any neurological symptoms and signs in the postoperative period. Accidents do happen in medical practice and especially drug error is most common. We can and must avoid such accidents by proper labelling and double-checking as mentioned by the author. However, we wish to add certain points regarding the practice of epidural practice and test dose.

Epidural test dose standard practice around the world is either 3 mL of 1.5% lignocaine with 5 mcg of adrenaline per mL which is most commonly used or 3 mL of 0.25% or 0.5% bupivacaine with 5 mcg adrenaline per mL contrary from the 2 mL 0.5% bupivacaine without adrenaline used in this case.[2] Purpose of test dose is to rule out the intravascular placement of catheter which can be detected by adrenaline by an increase in the heart rate >10% from baseline in case of an intravascular placement and to rule out the subdural placement of catheter which can be detected by lignocaine or bupivacaine. The epidural test dose should always be prepared freshly because 1) it can assure strict aseptic environment, 2) adrenaline is unstable in lignocaine and preparing test dose well in advance can cause disintegration of the compound; and using commercial preparation of lignocaine with adrenaline (1:200000) does not serve the purpose of test dose since pH of the solution is highly acidic (3.3–5.5, average 4.5) as compared to pH of plain lignocaine solution (5.0–7.0) and it will be in the ionized form in acidic pH and local anesthetics penetrate the nerve membrane in the unionized form and block the action potential from inside the membrane in the ionized form,[3] and 3) it can avoid the drug error if it is prepared freshly just before giving the injection, of course with double-checking the ampoules.

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