Teaching Neuraxial Analgesia

Abstract

To the Editor Among the most emotionally trying tasks for the anesthesiologist–instructor is teaching enthusiastic anesthesiology residents how to perform epidural anesthesia—more specifically, how to identify the ligamentum flavum and thus avoid inadvertent dural puncture and its consequences. The senior author recently (again) experienced this scenario when, assured by a confidant trainee that she was familiar with the “feeling” of loss of resistance (LOR) using normal saline, the dura was accidentally punctured on the first pass of the Tuohy needle. Disappointed at not having better guided the trainee, the supervising anesthesiologist retired to the staff room where he discovered a bag of lemons left by a staff member for others to share. Feeling “like a lemon” because of what had just occurred, the anesthesiologist was struck by the potential suitability of a lemon to facilitate teaching the sequential feelings when inserting a Tuohy-type epidural needle, of “skin puncture” (proximal lemon skin), “supraspinous and interspinous ligamentous resistances” (lemon flesh), the firm resistance of the “ligamentum flavum” (distal lemon skin), and ultimately of “loss of resistance” (penetration of the distal lemon skin) (Fig. 1).Figure 1: Lemon with opposed paracetamol bottle (“vertebral lamina”) preventing piercing of distal lemon skin (“ligamentum flavum”) by the Tuohy needle.Trials by the first author, 6 trainee anesthesiologists, 1 medical student, and 1 Director of Anesthesiology revealed that the size (5–8 cm) and resistances provided by a lemon quite satisfactorily mimicked the spatial relationships and feelings experienced when inserting and seeking LOR using a conventional Tuohy needle. By holding an IV (paracetamol) bottle firmly against the distal lemon skin (“ligamentum flavum”) of the lemon, recognition of the unique firmness of impaction of the epidural needle tip on bone is also demonstrable. Subsequent cephalad (or caudad) angulation of the epidural needle to avoid the bottle (“vertebral lamina”) results in successful identification of LOR. Furthermore, by holding a disposable surgical glove tautly filled with water (sealed with a knot) firmly against the distal lemon (“ligamentum flavum”) skin enables trainees to practice inserting a small-gauge spinal needle and develop an appreciation of the time required for backflow of cerebrospinal fluid through a fine-gauge spinal needle when performing spinal analgesia (Fig. 2).Figure 2: Lemon with opposed surgical glove distended with water to demonstrate “cerebrospinal fluid backflow” when penetrated by “needle through needle” spinal needle.The authors suggest that a lemon so used may assist both those teaching and learning epidural analgesia from “making lemons of themselves,” and regret that they cannot patent the lemon as a teaching aid. Anton A. van den Berg, MBChB, FRCA, ECFMG, OHU Department of Anaesthetics The Armadale Hospital Armadale Western Australia, Australia [email protected] Debra Liao University of New South Wales Medical School in Newcastle Newcastle New South Wales, Australia