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 25-28 September, 2018 | Singapore
pelvic fractures.
Anatomic landmarks
· Lumbo-Sacral Epidural: The LS intervertebral space is located by palpation of the cranial border of the iliac crests using the the thumb and third finger of the non-dominant hand; an imaginary line between them runs over the L6-to-L7 space, which is palpated with the index finger. The index finger is placed on the patient’s midline and palpates the LS space as a de- pression on the midline. The index finger is also used to confirm the proper space by palpating cranially (the dorsal spinous process of L6 is larger than L7) and caudally (the sacrum does not have interverte- bral spaces).
· Caudal Epidural: Palpate the space between the sacrum - Cd1 or Cd1 - Cd2, which can be easily identi- fied by having a team member move the tail up and down
The injection site should be clipped to ensure hairless margins laterally to the aspects of the ilial wings, cranially to L3-4 and caudally to S3-Co1. The skin is prepared aseptically with in a standard pre-surgical fashion to avoid infection/abscess of the epidural space and discospondylitis.
In most instances the pre-emptive approach to pain management in surgical patients’ results in epidural injections performed after induction to general anaesthesia before the start of surgery. Epidural injections and catheter placement may under certain circumstances be performed on sedated patients (most commonly in the intensive care unit), with superficial infiltration of local anaesthetic to facilitate the procedure. Strict aseptic technique should be followed throughout the epidural injection or epidural catheter placement. Sterile gloves as well as a facemask and hair covering should be worn. A sterile fenestrated drape should
be placed over the intended needle insertion site. A sterile table drape can assist in maintaining a sterile field with which to place all required equipment and drugs. Under sterile conditions, the needle is introduced perpendicular to the skin (with the bevel of the needle directed cranially) while the index finger of the palpating hand remains in the L-S intervertebral space to ensure accurate positioning. Adjustments to the angle of insertion can be made as required to facilitate correct placement in the epidural space. Once the needle has traversed through the skin and subcutaneous tissue
the stylet is removed. The hub of the needle is then filled with sterile saline to facilitate the “hanging drop” confirmation technique. The needle is then advanced further. As the needle advances, a ‘‘pop’’ maybe felt when it pierces the ligamentum flavum, and the needle is introduced into the epidural space. Once the ligament is penetrated, the “hanging drop” solution is the fluid is
aspirated into the needle shaft by the sub-atmospheric epidural pressure. In dogs, I recommend advancing the needle all the way to the floor of the epidural space in and then withdrawing 1 to 2 mm; in this way, the position of the needle is ensured in the epidural space and being off midline can be ruled out. In cats, the presence of the spinal dura mater beyond L7 makes it likely that CSF is obtained if the needle is advanced to the floor; therefore, it is best avoided. Instead, flicking of the tail, movement of the hind limbs, or twitching of the skin in the area
of the L-S intervertebral space is commonly observed
in cats when the needle enters the epidural space
and pricks the spinal cord or cauda equina, without subsequent adverse effects; however, for this reason, smaller gauge spinal needles are recommended in cats. To verify correct placement of the needle, several tests can be performed. A plastic or glass syringe, specifically designed to offer minimal resistance, can be attached
to the needle, and air can be injected to detect “loss of resistance” on injection because of the sub-atmospheric pressure of the epidural space.
Advanced confirmation techniques
Epidural pulse wave measurement: For the epidural pressure waveform method, the epidural needle or catheter is connected to a pressure transducer, volume is injected into the space, and waveforms are observed on the monitor. The presence of the injected fluid in the epidural space facilitates transmission from CSF pressures and allows arterial pulsations to be visible.
Electro-location: A shielded nerve stimulator or
Tuohy needle is primed with 0.2 to 1 mL of saline, and connected to a peripheral nerve stimulator set to deliver a current at 1 Hz, with a pulse width of 0.2 m sec. Initially the current is set at 1.2 mA as the needle is advanced into position. Confirmation of epidural needle placement is confirmed when twitches were observed in the pelvic limbs and/or tail. The lowest mean (range) current reported to elicit pelvic limb twitches is 0.72 mA (0.4–1.0 mA); lowest mean (range) current reported to elicit tail twitches is 0.58 mA (0.4–1.0 mA).; tail twitches were reliably lost at a mean current of 0.37 mA (0.2–0.8).
Ultrasound: Ultrasound-guided epidural injection has been described in dogs.(1)
Prior to injection, the hub of the needle should be observed for the presence of CSF or blood. If CSF is obtained during epidural attempts, withdrawing the needle slowly may reposition the needle back into
the epidural space. It is not recommended to inject an epidural dose intrathecally. It is recommended to reduce the dose by 25% to 50%. If blood, is obtained during epidural attempts, withdraw the needle and redirect your approach or consider an alternative location (e.g. L6 – L7, between the sacrum - Cd1 or Cd1 - Cd2) using a

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