Comparison between the hanging-drop technique and the running-drip method for
identification of the epidural space in dogs.
F Martinez-Taboada1 & JI Redondo2
1North Downs Specialist Referrals, The Friesian Building 3 & 4, Brewer Street,
Bletchingley, Surrey, UK. 2Departamento de Medicina y Cirugía Animal, Facultad de
Veterinaria, Instituto de Ciencias Biomédicas, Universidad CEU Cardenal Herrera,
The aim of this study was to compare the running-drip method (RDi) (Baraka 1972), a
simple technique never used in animals, with the hanging drop (HDo) technique in dogs in
sternal (S) and lateral (L) recumbency.
Forty-four healthy dogs requiring epidural blocks as part of a standardized balanced
anaesthetic plan were randomised into four groups. The same person performed all the
blocks using Tuohy needles with a fluid-prefilled hub when advancing through the
ligamentum flavum (HDo) or connecting a drip-set elevating 60 cm the drip fluid level from
the spinous or the tranverse processes (RDi). The number of attempts, the “pop”!
sensation, clear drop aspiration or fluid dripping, the time-to-locate-the-epidural-space
(TTLES) and the presence of CSF were recorded. When the identification was successful
a bupivacaine-morphine combination was injected. The success of the block was
assessed by experienced observers, unaware of the method used, based on usage of
rescue analgesia (intraoperative fentanyl in response to cardiovascular changes, and
postoperative methadone in response to pain scores). Data was checked for normality.
Binomial variables were analyzed with the Chi-square or Fisher’s exact test when
appropriated. The scores of ordinal variables were analyzed using the Kruskal-Wallis and
the Mann-Whitney tests (p<0.05).
There were no differences between groups except for LHDo which required more
attempts (6 of 11 dogs required >1 attempt) than SRDi (0/11) (p=0.0062) and the drop-
aspiration was more often observed in SHDo (9/11) than in LHDo (2/11) (p=0.045).
TTLES was lower (p=0.006) in SHDo (20 (14-79) sec) than in LHDo (47 (18-82) sec).
There were no differences between the other groups. No differences were found in rescue
analgesia or pain scores.
In conclusion, RDi is an easy, useful and fast technique to identify the epidural space in
dogs. The LHDo was the most difficult technique requiring more time and attempts.
Baraka A. (1972). Identification of the peridural space by a running infusion drip. British
Journal of Anaesthesia 44, 122 –!122.!