Whoosh test 2 and confirmation of lumbar epidural space

Loss-of-resistance [LOR] to injection of air or saline as the tip of the epidural needle penetrates the ligamentum flavum is a popular means of identifying the epidural space [1]. Operators use either a glass syringe or a disposable plastic syringe to elicit LOR. We have observed that the LOR syringe, especially a glass syringe, occasionally elicits a false positive LOR to air injection. This may be due to unrecognised air leak secondary to poor connection of the syringe to the hub of the needle, leak between the barrel and the piston, and at times leakage between the track made by the larger introducer and the epidural needle. Since the LOR syringe is usually attached after the epidural needle has been introduced to a depth of 2–3 cm, any false positive LOR raises the apprehension of proceeding any further. To overcome this dilemma, when suspicion of false positive LOR exists, we perform the Whoosh Test-2 originally suggested for identifying the caudal epidural space [2]. We now follow a protocol wherein an injection of 1 ml saline with 0.5 ml air is made through the epidural needle. An assistant auscultates for the Whoosh – 2 sound two dermatomes above the injection site. To elicit an audible Whoosh – 2 sound, this injection of saline and air should be made rapidly as the Tuohy needle is of a wide bore and its spread is in either direction unlike the small gauge needle used for caudal injection where the spread is predominantly upwards. A negative Whoosh – 2 sound clearly identifies the false positive LOR and the operator either proceeds afresh in an adjacent epidural space and/or with a new LOR syringe. To date, we have never had a failed epidural following a positive Whoosh Test − 2.