Spinal Anesthesia



Fig. 34.1
Lateral positioning of patient for spinal anesthesia




  • An alternative position for infants is to have an assistant hold the patient in a sitting position with the hips flexed and the head flexed forward. Cooperative adolescent patients can assume this sitting position themselves with a trained assistant facing them for support. The advantage of the sitting position is to increase the CSF pressure in the lumbar region and improve CSF flow through the spinal needle.






      34.3.3 Surface Anatomy


      Important surface anatomy landmarks that should be identified prior to sonographic assessment of the spine include:



      • Spinous processes to ascertain midline and to assess for abnormal spine curvature: Due to delayed fusion in neonates and infants, these may be palpable as two adjacent bony landmarks.


      • Iliac crests: An imaginary line between the anterior iliac crests, commonly known as the intercristal (or Truffier’s) line, will cross the L5–S1 interspace in neonates and infants less than 1 year old and L4–L5 in older children (Fig. 34.2).

        A158691_1_En_34_Fig2_HTML.jpg


        Fig. 34.2
        Surface anatomy for pediatric spinal anesthesia. White and black lines indicate positions of iliac crests and intercristal line for neonates and children over 1 year old, respectively


      • Shoulders: Ensure that the left shoulder is not rotated forward and that both shoulders remain square to the bed. This will help ensure effective upper trunk flexion and alignment of the thoracic and lumbar spine, which may help with eventual dural puncture success.

      Optimal positioning cannot be overemphasized and, once established, the Tegaderm® dressing should be removed and the residual gel wiped off. Prior to the spinal attempt, a sonographic assessment of the lumbar spine should be completed.


      34.3.4 Sonographic Assessment






      • Sonographic assessment for spinal anesthesia is similar to that for lumbar epidural anesthesia (see Fig.​ 33.​11). High-frequency (10–13 Hz) probes produce excellent resolution in small children and infants; however, in adolescents, the depth of neuraxial structures may necessitate a lower-frequency probe such as a curvilinear 2–6 MHz probe to gain adequate signal penetration.


      • A wider footprint linear-array transducer (10–13 MHz) allows for an excellent median or paramedian longitudinal view. Occasionally, a paramedian longitudinal view provides better detail, but this usually adds little to a median view in neonates and infants that are less than 6 months of age.


      • Expect the sonoanatomy to be excellent (>80 %) in children under 3 months of age, but it will gradually decline in quality to approximately 30–40 % by 9 months of age.


      • There are significant benefits to completing a transverse and median or paramedian view of the lumbar spine prior to performing the spinal anesthetic. This allows one to:





        • Identify the lumbar and sacral levels prior to dural puncture.


        • Delineate the spinous processes and ideal needle trajectory.


        • Identify the conus medullaris to be confident that dural puncture is below the termination of the cord.


        • Estimate the depth to the subarachnoid space; the distance between skin and the dura can be estimated, which in neonates and infants can be narrow (6–8 mm) [6]. If significant pressure is used with the probe during the sonographic assessment, the estimated depth may be erroneous.


      • Recently, it was demonstrated that real-time color flow Doppler ultrasound can be used to distinguish epidural injection from intrathecal injection (i.e., epidural injection produces a positive signal; intrathecal produces no signal) (see Fig.​ 33.​22) [14].


      Clinical Pearls





      • Ultrasound may be useful for pre-scanning.


      • Spinal anesthesia may be completed under real-time ultrasound guidance, but the merit of this approach is uncertain and may increase the risk of contamination due to the required extra equipment and personnel.


      34.3.5 Nerve Stimulation Technique


      The use of nerve stimulation to assist for spinal anesthesia in pediatric patients is not a common practice and therefore will not be described. However, the electrical epidural stimulation test can assist in distinguishing the epidural space (>1 mA) from the intrathecal space (<1 mA) when using an insulated needle (see Chap.​ 2) [15].



      34.4 Equipment and Spinal Needle






      • Similar to all regional anesthetic blocks, there should be strict adherence to aseptic technique.


      • An absorbent pad should be placed between the warming blanket and the patient prior to the spinal anesthetic. Following the successful injection of the spinal anesthetic, the patient will occasionally have a bowel movement; an absorbent pad may be used to soak up these liquids that may otherwise inadvertently cool the patient over the course of the procedure.


      • Once in position for the spinal, the skin should be prepped with a 2 % chlorhexidine gluconate and 70 % isopropyl alcohol solution and allowed to dry.


      • A sterile clear plastic drape should be used, and a spinal needle and syringe containing the spinal anesthetic should be readily available.


      • Ensure comfortable ergonomics for both the anesthesiologist and the assistant holding the patient. We suggest that the anesthesiologist sit for stability and improved dexterity when attempting a spinal on an awake younger pediatric patient in lateral decubitus position.


      • If no topical gel or cream is used, infiltrate the skin with lidocaine 1 % using a 27G–30G needle prior to using the spinal needle.


      34.4.1 Needles






      • The lumbar puncture is performed using a midline approach, preferably with a short 25G–27G styletted spinal needle. The type of needle has not been shown to have an effect on success or postspinal complications in the pediatric population [16, 17]. However, a smaller needle size could reduce the risk of post-dural puncture headache which is difficult to assess in this population.


      • Various types of spinal needles are available in pediatric sizes. Our approach is to use a 2.5 cm, 25G pencil-point needle (Pencan® Paed, B.Braun, Melsungen, Germany) and, if not successful, a 3.8 cm, 22G Quincke spinal needle. An introducer is not necessary in neonates and young infants.


      • In children, the ligamentum flavum is soft, and a distinctive “pop” may not be appreciated when the dura is punctured.


      • It is important to remove the stylet intermittently and examine for CSF flow. Initial CSF may be slightly blood tinged; ensure continued flow of clear fluid prior to injection of the anesthetic.


      • In neonates and young infants, use a 1 mL syringe (tuberculin syringe with clear gradations) to inject the drug slowly. A good rule of thumb is to inject over a 15–20 s period while avoiding the barbotage method as it may result in unacceptably high levels of motor blockade.


      • Once the subarachnoid block is performed, avoid elevating the legs or lower trunk. This will help to prevent cephalad spread of local anesthetic and is especially important during the application of the return pad which is typically fixed to the backs of neonates and young infants.


      34.5 Local Anesthetics




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      Sep 22, 2016 | Posted by in ANESTHESIA | Comments Off on Spinal Anesthesia

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