The effect of body position on the 'hanging drop' method for identifying the extradural space in anaesthetized dogs.
OBJECTIVE
To assess the accuracy of the 'hanging drop method' for identifying the extradural space in anaesthetized dogs positioned in sternal or lateral recumbency.


METHODS
Prospective randomized-experimental study.


METHODS
Seventeen clinically healthy adult dogs, 10 females and seven males weighing 8.4-26.2 kg.


METHODS
Dogs were positioned in either sternal (n = 8) or lateral (n = 9) recumbency under general anaesthesia. A 20 SWG spinal needle pre-filled with 0.9% saline was advanced through the skin into the lumbosacral extradural space and the response of the saline drop recorded, i.e. whether it: 1) was aspirated from the hub into the needle; 2) remained within the hub, or 3) moved synchronously with i) spontaneous respiration, ii) heart beat or iii) manual lung inflation. The position of the needle tip was ultimately determined by positive contrast radiography.


RESULTS
One dog positioned in lateral recumbency was excluded from the study because bleeding occurred from the needle hub. Saline was aspirated into the needle in seven of eight dogs held in sternal recumbency but in none of the dogs positioned in lateral recumbency. Accurate needle tip placement in the extradural space was confirmed by positive contrast radiography in all dogs.


CONCLUSIONS
The 'hanging drop' method, when performed with a spinal needle, appears to be a useful technique for identifying the location of the extradural space in anaesthetized medium-sized dogs positioned in sternal, but not in lateral recumbency. The technique may yield 'false negative' results when performed in dogs positioned in sternal recumbency.
Naganobu
Kiyokazu
K
Faculty of Agriculture, Veterinary Teaching Hospital, University of Miyazaki, Miyazaki 889-2192, Japan. a0e303u@cc.miyazaki-u.ac.jp
Hagio
Mitsuyoshi
M
D000768:Anesthesia, General / Q000379:methods / Q000662:veterinary*; D000818:Animals; D004285:Dogs; D005260:Female; D007268:Injections, Epidural / Q000379:methods / Q000662:veterinary*; D008297:Male; D011187:Posture / Q000502:physiology*