Abstract :
[en] SUMMARY
Percutaneous ultrasound guidance has become a routine procedure in veterinary medicine in domestic animals. It allows precise placement of the needle in the desired target. Punctures of the subarachnoid space in dogs are frequently carried out in veterinary practice for diagnostic purposes. In these procedures, the placement of the needle into the subarachnoid space (atlanto-occipital or lumbar) is commonly performed blindly by feeling the bony anatomical landmarks but this can be laborious or even impossible in some patients as reported in human medicine. The topic of this study is ultrasound guidance for the placement of the needle during puncture of the subarachnoid space.
The needle placement can be done under ultrasound guidance according to two methods. The "indirect guidance" is a method of deferred ultrasound guidance. The "direct guidance" is a real time procedure in which the operator holds the needle in one hand and the ultrasound probe in the other. It allows direct visualization of the needle (if direct guidance), the target structure, adjacent tissues (including vascular structures) and potential injectate while minimizing the risk of complications.
Punctures of the subarachnoid space are carried out by placing the needle in the cisterna magna or in the caudal lumbar subarachnoid space (between the fifth and sixth lumbar vertebrae). The cisternal puncture is most frequently used in practice but presents greater risk of iatrogenic lesions of the brain stem. The lumbar puncture is technically more difficult and is frequently contaminated by iatrogenic blood. Cerebrospinal fluid punctures have several clinical applications. They allow to collect cerebrospinal fluid for diagnostic testing, to realize myelograms or myeloscanners by injecting contrast medium and to perform spinal anesthesia or analgesia by injecting one or more substance(s) blocking the conduction of the spinal nerves.
Subarachnoid lumbar puncture is used commonly in the dog for cerebrospinal fluid collection and/or myelography. Percutaneous ultrasound anatomy of the lumbar region in the dog and a technique for ultrasound-guided lumbar puncture were described in the first study. Ultrasound images obtained ex- vivo and in-vivo were compared with anatomic sections and used to identify the landmarks for ultrasound-guided lumbar puncture. The ultrasound-guided procedure was established on cadavers and then applied in-vivo on eight dogs. The anatomic landmarks for the ultrasound-guided puncture, which should be identified using the parasagittal oblique ultrasound image, were the articular processes of the fifth and sixth lumbar vertebrae and the interarcuate space. The spinal needle was directed under direct ultrasound-guidance toward the triangular space located between the contiguous articular processes of the fifth and sixth lumbar vertebrae and then advanced to enter the vertebral canal. Using these precise ultrasound anatomic landmarks, an ultrasound-guided technique for lumbar puncture is applicable to dogs.
Cisternal puncture in dogs and cats is commonly carried out. Percutaneous ultrasound anatomy of the cisternal region in the dog and the cat and an indirect technique for ultrasound-guided cisternal puncture were described in the second study. Ultrasound images obtained ex-vivo and in-vivo were compared with anatomic sections and used to identify the landmarks for ultrasound-guided cisternal puncture. The ultrasound-guided procedure was established in cadavers and then applied in- vivo in seven dogs and two cats. The anatomic landmarks for the ultrasound-guided puncture were the cisterna magna, the spinal cord, the two occipital condyles on transverse images, the external occipital crest and the dorsal arch of the first cervical vertebra on longitudinal images. Using these ultrasound anatomic landmarks, an indirect ultrasound-guided technique for cisternal puncture is applicable to dogs and cats.
The standard technique for placing a needle into the canine lumbar subarachnoid space is primarily based on the palpation of anatomic landmarks and the use of probing movements of the needle. However, this technique can be challenging for novice operators. The aim of the third observational, prospective, ex vivo, feasibility study was to compare ultrasound-guided versus standard anatomic landmark approaches for novices performing needle placement into the lumbar subarachnoid space using dog cadavers. Eight experienced operators validated the canine cadaver model as usable for training landmark and ultrasound-guided needle placement into the lumbar subarachnoid space based on realistic anatomy and tissue consistency. With informed consent, 67 final year veterinary students were prospectively enrolled in the study. Students had no prior experience in needle placement into the lumbar subarachnoid space nor use of ultrasound. Each student received a short theoretical training about each technique before the trial and then attempted blind landmark-guided and ultrasound-guided techniques on randomized canine cadavers. After having performed both procedures, the operators completed a self-evaluation questionnaire about their performance and self-confidence. Total success rates for students were 48% and 77% for the landmark- and ultrasound-guided technique, respectively. Ultrasound guidance significantly increased total success rate when compared to the landmark-guided technique and significantly reduced the number of attempts. With ultrasound guidance self-confidence was improved, without bringing any significant change in duration of the needle placement procedure. Findings indicated that the use of ultrasound guidance and cadavers is a feasible method for training novice operators in needle placement into the canine lumbar subarachnoid space after short theoretical training.
Ultrasound-guided techniques for needle placement in the cisterna magna and in the lumbar subarachnoid space were described in the dog. The aim of the fourth observational, prospective, ex-vivo study was to compare the impact of ultrasound guidance for the cisternal versus lumbar needle placement using dog cadavers. With informed consent, 83 operators were prospectively enrolled in the study. They were divided in four groups depending on experience. Each operator received a short theoretical training about each technique before the trial and then attempted a cisternal and lumbar punctures with blind landmark-guided and ultrasound-guided techniques on randomized canine cadavers. The lumbar ultrasound-guidance was direct while the cisternal ultrasound-guidance was indirect. After having performed each procedure, the operators completed a self-evaluation questionnaire about their previous experience, their performance and their self-confidence. The ultrasound guidance significantly increased total success rate in both areas compared with the blind technique but more significantly in the lumbar region. The cisternal ultrasound guidance significantly improved the number of attempts, the time needed to perform the procedure and the self-confidence in inexperienced and experienced operators. The lumbar ultrasound guidance significantly increased the self-confidence in inexperienced and experienced operators and significantly decreased the number of attempts in inexperienced operators. The first cause of failure cited was different according to the location of the puncture and was related to the nature of ultrasound guidance. Findings indicated that the use of ultrasound guidance by novice and experienced operators improved different parameters according to the location of the needle placement. This study demonstrated that inexperienced operators are able to use ultrasound guidance after a short theoretical teaching session in an ex-vivo context and this supports the use of ultrasound-guidance for learning and teaching purposes.
The study of the impact of ultrasound guidance for needle placement procedures described in this work could be developed and studied for other technically difficult or risky procedures on dogs. If the benefits of ultrasound guidance demonstrated ex-vivo in this work are transferable to the clinical conditions, punctures of the subarachnoid injections would be less « scary » for novice operators and become routine procedures applicable by a large numbers of veterinarians.
