The use of an acoustic device to identify the epidural space in cattle
Division of Anaesthesiology and Perioperative Intensive Care, University of Veterinary Medicine, Vienna, Austria. The Veterinary Journal
(Impact Factor: 1.76).
02/2011; 187(2):267-8. DOI: 10.1016/j.tvjl.2010.01.012
Twelve healthy cattle (weighing 188-835 kg) were placed in stocks and sedated with xylazine. Caudal epidural puncture was performed using an acoustic device that indicated a decrease in resistance with a change in pitch. Lidocaine was injected to verify correct needle placement by assessing needle prick stimuli applied on the left and right side of the tail root and the perineal region, and the loss of tail and anal sphincter tone. Pressure measurements were recorded during penetration of the different tissue layers and in the epidural space. A clear and sudden decrease in the pitch of the acoustic signal was audible in all 12 cattle. All cows showed clinical effects indicating successful epidural anaesthesia. The pressure in the epidural space after puncture was -19±10 mm Hg. The device may be of assistance in identifying the epidural space in cattle.
Available from: Yves Moens
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ABSTRACT: The objective of this study was to compare an Acoustic Puncture Assist Device-Epidural Locator (APAD-EL) with the "pop sensation" (POP) and "lack of resistance" (LOR) commonly used to confirm penetration of the ligamentum flavum and to ensure correct epidural placement in dogs and cats. We recruited 38 dogs and cats undergoing surgery and receiving epidural analgesia. Two anesthetists performed epidural puncture using the POP and LOR signs. Simultaneously, APAD-EL was used to collect visual and acoustic confirmation during advancement and placement of the needle tip for post hoc evaluation. A positive APAD-EL sign consists of a sudden pressure drop at the needle tip visible on a display and a concomitant pitch change of an acoustic signal. Failure to record a sudden pressure drop is considered a negative APAD sign. Descriptive statistics were used. In 32 patients with positive POP and LOR, the APAD was also positive. In one patient, POP was positive with a negative LOR and APAD result. Five patients had negative POP but positive LOR. Four patients had APAD positive and one (dog) APAD negative. Study results showed that the APAD-EL information supports the subjective signs of correct needle placement suggested by positive POP and LOR experienced by trained anesthetists. The technique can be useful to assist difficult epidural puncture and as a training and teaching tool.
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