Lumbar epidural catheter insertion: the midline vs' the paramedian approach Leiden University Medica

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Lumbar epidural catheter insertion the midline
vs. the paramedian approach
Leiden University Medical Center,

Department of Anesthesiology,
Leiden, The
Netherlands

• European Journal of Anaesthesiology
• 200522839-842
• By ??? Apr. 28, 2006

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Introduction
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Continuous epidural anesthesia (CEA)

• technique frequently used to provide anesthesia
  for operative procedures
• Epidural catheter offers possibility to prolong
  anesthesia and postoperative analgesia

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• Most frequent side effect related to epidural
  catheter insertion is the occurrence of
  paresthesias
• 16 -89
• Usually mild, not associate with untoward
  sequela, may signal nerve root damage, unpleasant
  experience
• Lowering the incidence of paresthesias would be
  beneficial

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• Lumbar epidural space entering midline or
  paramedian
• Midline approach is used most widely
• Requires less 3-dimensional insight and the
  ligamentum flavum is at its widest, and easy to
  identify in majority of patients

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Paramedian appraoch

• Cases of narrow lumbar interspace
• Offers higher success rate
• Bypass most bony structures impeding the
  advancement of the epidural needle in midline
• Steeper angle facilitate epidural catheter
  insertion
• Incidence of accidental dural puncture is lower
• Associate with fewer technical problems

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Purpose of study

• Compare the characteristics of epidural catheter
  insertion via midline or paramedian
• Ease of catheter insertion
• Incidence of paresthesias
• Efficacy of sensory and motor blockade

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Methods
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• 30 patients
• Age 18-80 y/o, ASA I-III,
• non-pregnant
• Scheduled for lower limb surgery under lumbar
  epidural anesthesia
• Computer-generated randomization list, patients
  allocated to either midline or paramedian group

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• Premedicate midazolam 7.5-15 mg orally 1hr
  before regional anesthesia
• iv access, standard routine monitoring
• Additional midazolam iv 1-2mg immediately prior
  to lumbar puncture
• Patient in sitting position

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• All performed by one investigator experienced
  with both midline and paramedian approach
• Signal readiness to a blinded observer unable to
  see the procedure
• 17G Tuohy needle at third lumbar interspace, loss
  of resistance technique

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• 19G multi-orifice catheter inserted 5cm into the
  epidural space and remove epidural needle
• After catheter insertion, the observer ask the
  patient for any signs of pain or discomfort
• Negative aspiration, negative test dose of 3mL
  prilocaine 1
• Loading dose 15mL ropivacaine 1
• Patient turned to supine horizontal position

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• Maximum sensory blockade measured every 5 min by
  blinded observer using loss of temperature
  sensation in anterior axillary line with ice cube
  (until 20 min)
• Motor blockade scored using 12-point scale
• Maximum motor block score evaluate at 5 min
  intervals (until 30 min)
• Quality of surgical anesthesia judge by the need
  for analgesics and by patient on a 3-point scale
  (good/fair/poor)

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Following outcome variables

• Time needed to identify the epidural space
• Time needed to site the epidural catheter as a
  measure for ease of catheter insertion
• Incidence of paresthesias
• Block characteristics
• Need for intraoperative analgesics
• Verbal rating of the quality of analgesia after
  surgery

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Results
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• No significant differences among two groups
  regarding age, height, or weight

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Table 1. Patient characteristics
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• Time needed to identify the epidural space was
• midline 13.2 5.4 s
• paramedian 21.1 19.7 s
• Catheter insertion significantly faster in
  paramedian group
• (9.0 5.1 s vs. 18.2 6.2 s)

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• 5 patients in midline group experienced
  paresthesias during catheter insertion
• 1 patient in paramedian group

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• Epidural block characteristics (maximum level of
  sensory and motor block) were similar
• Median maximum levels of sensory blockade
• T4 (range C3-L1) in midline
• T4 (range T2-T12) in paramedian

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• Median maximum motor block score
• 4 (range 0-10) in midline
• 6 (range 0-12) in paramedian
• Quality of sensory and motor blockade is adequate
  in both group
• No patient require GA or iv opioid
  supplementation
• All patients had good quality of block except one
  fair in paramedian group
• No case of poor block

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Discussion
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• Higher incidence of paresthesias in midline group
  (33 vs 6.7)
• Type of approach was a significant independent
  predictor of paresthesias during epidural
  catheter insertion

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• Jaucot (1986) lower incidence of paresthesias
  (22 vs 42.5) and vascular puncture using
  paramedian approach
• Blomberg (1989) reported 4 paresthesias using
  paramedian and 36 using midline
• Jaucot vs Blomberg 22 vs 4

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• Jaucot found severe paresthesias in 5.6 of
  midline and 1.5 of paramedian catheter insertion
• No severe parethesias in our population
• Jaucots study 1981 to 1985
• Difference in catheter stiffness may play a
  significant role

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• Catheter insertion was significantly faster and
  easier using paramedian
• Blomberg found resistance to catheter insertion
  less common with paramedian approach
• Steeper angle of entry of the paramedian epidural
  needle into the epidural space, facilitate
  catheter insertion

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• Epiduroscopic cadaver study (1988) using midline
  approach, there is dural tenting, the catheter is
  unpredictable due to strands of connective tissue
  restricting movement of dura mater
• Paramedian advance in a cephalad direction
  without dural tenting

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• Paramedian 3-dimensional insight, more difficult
  for inexperienced anesthesiologist
• A study (1996) assessing epidural success rate of
  new residents, midline approach associated with
  fewer attempts and higher success rate
• Sprung (1999) found no differences in success
  rate between paramedian and midline approach

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• The presumably lower risk of accidental dural
  puncture using paramedian approach is based on
  cadaver study (1988), no substantiate by clinical
  studies to date

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• No differences in the quality and characteristics
  of sensory and motor blockade
• Motor block was not complete in the majority of
  patients
• Observation period was limited to 30 min after
  epidural injection and motor block may
  intensified beyond this point

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Summary

• Epidural catheter insertion was significantly
  faster when using the paramedian approach
• The type of approach was an independent
  significant predictor of the occurrence of
  paresthesias