The "woosh" test - evaluation of a new method for identification of the epidural space in dogs

Epidural anaesthesia (EA) is a widely used method for medical pain treatment. An important prerequisite for a successful EA procedure is the correct placement of the needle in the epidural space. The ‘whoosh’ test has been recommended as a guide for successful epidural needle placement in humans. The purpose of this study was to evaluate the ‘whoosh’ test and the epidural pressure waves measurement (EPWM) in dogs. The intraoperative need of analgesics served as a control. Eighty dogs undergoing elective surgery were included in the study. Epidural anaesthesia (EA) was performed under general anaesthesia with dogs in lateral recumbency. The epidural needle was placed in the lumbosacral space. After placing the epidural needle, two ml of air were injected whilst a stethoscope was placed immediately cranially to the needle. If a ‘whoosh’ sound was identified the ‘whoosh’ test was judged positive, if not negative. Thereafter the EPWM was performed. Depending if a wave was identifiable or not, the EPWM was recorded as positive or negative. The ‘whoosh’ test showed a sensitivity of 74% and a specifity of 50%. Sensitivity of the EPWM was 44%, specifity 100%. In laterally recumbent dogs, the ‘whoosh’ test was more sensitive but less specific in identifying the epidural space than EPWM. Nevertheless would the ‘whoosh’ test be a simple and quick method to add information to the clinical impression of correct epidural needle placement.