Sonographic evaluation of epidural and intrathecal injections in cats

Incidence of dural sac puncture during neuraxial anesthesia in cats: an observational, retrospective study

OBJECTIVES

The aim of this study was to determine the occurrence of dural puncture, indicated by cerebrospinal fluid (CSF) outflow, in cats receiving neuraxial anesthesia through a lumbosacral injection guided by a pop sensation method.

METHODS

This was an observational, retrospective study. Cats that were scheduled for lumbosacral neuraxial anesthesia were included. Medical records were analyzed to investigate: (1) demographic data; (2) neuraxial anesthesia performed (epidural/spinal); (3) type of needle used, including gauge and length; (4) presence of CSF (yes/no) and/or blood (yes/no) in the hub of the needle; and (5) flicking of the tail during needle advancement (yes/no).

RESULTS

A total of 94 medical records were analyzed. A 22 G 50 mm Tuohy needle was used in all cats scheduled for an epidural injection (n = 60), whereas a 22 G 40 mm Quincke needle was used in all cats scheduled for an intrathecal injection (n = 34). CSF outflow was detected in 55/60 (91.7%) cats in which a Tuohy needle was used, and 34/34 (100%) of the cats in which a Quincke needle was used (P = 0.15). Flicking of the tail was detected in 41/60 (68.3%) and in 24/34 (70.6%) injections with Tuohy and Quincke needles, respectively (P >0.99). Traces of blood, but not active blood outflow, were detected via staining of the first drops of CSF in 2/34 cats in which Quincke needles were used and in none of the cats in which Tuohy needles were used (P = 0.12).

CONCLUSIONS AND RELEVANCE

This study shows that the lumbosacral approach for neuraxial anesthesia in cats may result in a dural sac puncture when 22 G Quincke or Tuohy needles are used. The pop sensation method should be deemed effective in predicting intrathecal but not epidural needle placement.

Anatomical dimensions of the lumbar dural sac predict the sensory block level of continuous epidural analgesia during labor

BACKGROUND

The anatomical dimensions of the lumbar dural sac determine the sensory block level of spinal anesthesia; however, whether they show the same predictive value during continuous epidural anesthesia (CEA) remains undetermined. We designed the present study to verify the efficacy of the anatomical dimensions of the lumbar dural sac in predicting the sensory block level during labor analgesia.

METHODS

A total of 122 parturients with singleton pregnancies requesting labor analgesia were included in this study. The lumbar dural sac diameter (DSD), lumbar dural sac length (DSL), lumbar dural sac surface area (DSA), and lumbar dural sac volume (DSV) were measured with an ultrasound color Doppler diagnostic apparatus. CEA was performed at the L2-L3 interspace. After epidural cannulation, an electronic infusion pump containing 0.08% ropivacaine and sufentanil 0.4 μg/ml was connected. The sensory block level was determined with alcohol-soaked cotton, a cotton swab, and a pinprick. The analgesic efficacy of CEA was determined with a visual analog scale (VAS). The parturients were divided into two groups, "ideal analgesia" and "nonideal analgesia," and the groups were compared by t test. Pearson's correlation was performed to evaluate the association between the anatomical dimensions of the lumbar dural sac and sensory block level. Multiple linear regression analysis was used to create a model for predicting the sensory block level.

RESULTS

In the ideal analgesia group, the height, DSL, DSA, DSV and DSD were significantly smaller, and the body mass index (BMI) was significantly larger (P < 0.05). In addition, the DSL demonstrated the strongest correlation with the peak level of pain block (r = - 0.816, P < 0.0001; Fig. 2A), temperature block (r = - 0.874, P < 0.0001; Fig. 3A) and tactile block (r = - 0.727, P < 0.0001; Fig. 4A). Finally, the multiple linear regression analysis revealed that DSL and BMI contributed to predicting the peak sensory block level.

CONCLUSION

In conclusion, our study shows that the sensory block level of CEA is higher when the DSL, DSA, DSV and DSD of puerperae are lower. DSL and BMI can be treated as predictors of the peak sensory block level in CEA during labor analgesia.

A prospective randomized, double-blinded clinical study evaluating the efficacy and safety of bupivacaine versus morphine-bupivacaine in caudal epidurals in cats with urethral obstruction

OBJECTIVE

To investigate the efficacy and safety of the caudal epidural technique in cats with urethral obstruction (UO).

DESIGN

Prospective, double-blinded, randomized, sham-controlled study.

ANIMALS

Eighty-eight male cats with UO.

INTERVENTIONS

Thirty cats randomized to bupivacaine epidural (BUP), 28 cats to bupivacaine-morphine epidural (BUP/MOR), and 30 cats to sham epidural (SHAM).

MEASUREMENTS AND MAIN RESULTS

Time to perform the epidural and efficacy of the epidural was assessed by evaluation of tail and perineal responses. The amount of propofol for urinary catheterization and time to administration of rescue analgesia (buprenorphine) was recorded. Cats were monitored for epidural complications. The median time to perform the epidural was 2 min (range, 0.2-13 min and range, 0.5-13 min), with an epidural success rate of 70%. The median amount of propofol administered for urinary catheterization was significantly less in the BUP (2.1 mg/kg; range, 0-7.5 mg/kg) and MOR/BUP cats (1.85 mg/kg; range, 0-8.6 mg/kg) as compared to SHAM cats (4 mg/kg; range, 0-12.7 mg/kg) (P = 0.006, P = 0.0008, respectively). The median time to administration of rescue analgesia was also significantly longer in the BUP (10 h; range, 2-32 h) and MOR/BUP cats (10 h; range, 4-45 h) as compared to SHAM cats (4 h; range, 2-36 h) (P = 0.0026, P = 0.0004, respectively). There were no recognized complications related to the epidural.

CONCLUSION

Caudal epidural appears to be safe, may reduce the amount of IV anesthesia needed to facilitate urinary catheterization, and can be used to provide long-term analgesia in the hospital.

Identification of the sacrococcygeal epidural space using the nerve stimulation test or the running-drip method in dogs

OBJECTIVE

To compare the nerve stimulation test (group NS) with the running-drip method (group RUN) for successful identification of the sacrococcygeal (SCo) epidural space prior to drug administration in dogs.

ANIMALS

A total of 62 dogs.

STUDY DESIGN

A randomized clinical study.

METHODS

Dogs requiring an epidural anaesthetic as part of the multimodal anaesthetic plan were randomly allocated to one of the two study groups. In group NS, the epidural space was located using an insulated needle connected to a nerve stimulator; in group RUN, the epidural space was identified using a Tuohy needle connected to a fluid bag elevated 60 cm above the spine via an administration set. The success of the technique was assessed 5 minutes after epidural injection by the disappearance of the patella reflex. Data were checked for normality, nonparametric data was analysed using a Mann-Whitney U test and success rate was analysed using a Fisher's exact test. The significance level was set at p < 0.05, and the results are presented in absolute values, percentage (95% confident interval) and median (range).

RESULTS

The success in identification of the epidural space did not differ between groups NS and RUN [87.1% (70.2%-96.4%) versus 90.3% (74.2%-98%); p = 1.000]. The time required for identification of the epidural space was shorter in group RUN [26 (15-53) seconds] than in group NS [40 (19-137) seconds] (p = 0.0225). No other differences were found in any studied variables.

CONCLUSION

and clinical relevance In this study, both RUN and NS techniques were successful in identifying the epidural space at the SCo intervertebral space. RUN requires no specialised equipment, can be performed rapidly and offers an alternative to the NS for use in general veterinary practice.