The Rational Clinical Examination
David L. Simel, Drummond Rennie
Lumbar Puncture
Sharon E. Straus, Kevin E. Thorpe, Jayna Holroyd-Leduc
Bed Rest After the Procedure
Topics Discussed:
cerebrospinal fluid analysis, cerebrospinal fluid pressure, clinical competence, clinical prediction/decision rules, diagnostic spinal puncture, likelihood ratio, meningitis, bacterial, positioning patient, summarizing the evidence, teaching issues
Excerpt:
"We found 537 citations of potential interventions to optimize
LP technique. Review of these led to retrieval of 22 full-text articles
for assessment, 15 of which were subsequently identified for inclusion.
Reasons for excluding trials were lack of randomization (5 studies18-22),
repeat publication (1 study23), and inability to
obtain outcomes data (1 study24). Studies were
categorized by intervention including needle type, needle size,
reinsertion of stylet, mobilization after LP, and use of supplemental
fluids. No studies of other interventions—such as positioning
of the patient during LP, direction of bevel, volume of CSF removed,
or prophylactic use of an epidural blood patch—met the
inclusion criteria.Fifteen randomized trials were identified with sample sizes ranging
from 44 to 600 people. Eight studies had sample sizes of 100 patients
or fewer.We were unable to identify any randomized studies that evaluated
the impact of the experience of the clinician performing LPs on
clinical outcomes. Some studies we identified included experienced
neurologists,23 whereas others involved students
under the supervision of physicians.25 In a case
series of LPs performed at an urban university-affiliated hospital,
the incidence of traumatic LP was 15% using a definition
of more than 400 red blood cells per high-powered field and 10% using
a definition of more than 1000 red blood cells.26 However,
the level of training and specialty of all physicians were not recorded.
One retrospective study compared the incidence of traumatic LP at
the end of the resident academic year when housestaff are more experienced
with that at the start of the next year when new housestaff begin training.
Using a cutoff of 1000 red blood cells/
L, there was no
difference in risk of traumatic LP between experienced housestaff
(14%) and inexperienced housestaff (12%).27 In
a prospective cohort of 501 patients who underwent LP either by
a nurse, physician, resident, or medical student, there was no significant
difference in the risk of post-LP headache among the 3 groups.8 We
found no data on the number of LPs required to demonstrate or maintain
proficiency.Normal resting CSF pressure is assumed to be 60 to 180 mm of
H2O or 6 to 14 mm Hg.46,47 In the single identified
study, CSF pressure changed little (<1.1 mm of water) with flexion
of the lower extremities.48 Various maneuvers,
such as compressing the abdomen or the jugular vein (Queckenstedt's maneuver49),
can increase CSF pressure.50 An obstruction to
CSF flow prevents the normal rise and fall in pressure (positive
Queckenstedt), but we were unable to find any studies describing
the accuracy of this maneuver for detection of CSF outflow obstruction...."
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