Retrospective study comparing success rates of lumbar puncture positions in infants

a b s t r a c t

Background: A lumbar puncture is performed in the emergency room for diagnostic purposes; unsuccessful or traumatic LPs can complicate decision making. The sitting position has a larger interspinous process compared to lateral recumbent and is safer in sick neonates at risk for cardiac and respiratory instability.

Purpose: Our study aims to determine which position (lateral recumbent or sitting) is associated with a greater likelihood of successful lumbar puncture in infants <3 months when performed in the emergency room.

Basic procedures: This is a retrospective chart review in infants aged <3 months who had a LP performed in a pe- diatric emergency room. The primary outcome was the rate of successful LPs, defined as obtaining adequate CSF to send for all studies. The secondary outcome was the proportion of atraumatic LPs by position, defined as <500 RBCs or < 10,000 RBCs.

Main findings: A total of 557 charts were reviewed with 116 in the sitting position and 441 in the lateral recum- bent position. The primary outcome of adequate CSF fluid collection was not significantly different between groups (63% sitting position versus 58% lateral recumbent position; p = 0.22). In addition, the proportion of atraumatic LPs showed no significant difference regardless of RBC cutoff (<500 RBCs p = 0.83, <10,000 RBCs p = 0.60).

Principle conclusions: This study found no evidence that there is a difference in rate of LP success nor the propor- tion of traumatic LP in infants less than 3 months of age when positioned in the sitting position compared to the lateral recumbent position.

(C) 2022

  1. Introduction

A lumbar puncture is performed in the pediatric emergency de- partment, most frequently as part of a sepsis evaluation in infants [1-3]. LPs in which little or no cerebral spinal fluid (CSF) is obtained occur as frequently as 32% of pediatric patients [1]. The most commonly cited complication of Lumbar punctures is vascular bleeding peripheral to the Spinal canal during needle insertion, known as “traumatic taps”

[2]; yet the definition of a traumatic tap varies among studies from

>400 to >10,000 red blood cells [4-6]. Traumatic taps have been known to occur in 20% of lumbar punctures in children and 33% of lumbar punctures in neonates [4,5]. In traumatic taps, peripheral Blood components can contaminate CSF and obscure analysis [2]. While there are formulas to account for this error, studies have shown

* Corresponding author.

E-mail address: [email protected] (R.P. Bhagat).

limitations in these corrections leading to Prolonged hospitalization and unnecessary antibiotics [7,8]. Prolonged antibiotic use itself also carries risk not limited to drug-resistance, kidney failure, and diarrhea [9].

Positioning is one factor which may affect success of the procedure. LPs are typically performed in either the lateral decubitus position or in the seated position with flexion [2,10]. The choice of position has been reported to depend on the comfort of the proceduralist [10]. It has been demonstrated the interspinous process is significantly larger while sitting compared to lateral recumbent in children [11-13]. Fur- thermore, the sitting position has been shown to be safer in sick neo- nates at risk for cardiac and respiratory instability [14,15]. Few studies have attempted to assess LP procedure success and complication rate by position in the pediatric emergency department (PED). Although limited by a small sample size, Hanson et al. demonstrated that sitting flexed had a higher rate for obtaining CSF on a first attempt in children

<12 months but found no difference in atraumatic taps [16]. The same

0735-6757/(C) 2022

study group later performed a single randomized trial on positioning for infants <3 months which showed no difference in success rates in the two positions, but evaluated success based on RBC counts at a higher RBC threshold (<10,000 RBCs), without assessing the amount of CSF obtained [17].

The objective of our study was to determine which position (lateral recumbent or sitting) is associated with a greater likelihood of success- ful lumbar puncture in infants <3 months when performed in the PED. For the purposes of this study, a successful LP was defined as an atraumatic tap in which adequate CSF to perform requested studies is obtained. By identifying the optimal position for infant LP, we aim to de- crease consequences of unsuccessful LPs such as prolonged unnecessary hospitalization or unwarranted antibiotics.

  1. Methods

We conducted a retrospective cohort study of infants <92 days who had a lumbar puncture performed at a tertiary care PED in NYC from January 2017 – November 2019. We excluded patients with no proce- dure note documented in the electronic medical record (EMR). Eligible patients were identified from the procedure code for lumbar puncture linked to their EMR.

We reviewed the patient’s charts and extracted the following data: date of birth, age, disposition time, primary discharge diagnosis, posi- tion of LP attempts, level of training of practitioners performing the LP, use of anesthetics, CSF white blood cell/Red blood cell count, results of a CSF culture, and results of a CSF Polymerase chain reaction . If there was more than one person annotated on the procedure note the lower level trainee was assumed to have performed the first attempt followed by the upper-level trainee. For positioning, there were 3 cate- gories: knee to chest, lateral decubitus and sitting. In this study we ag- gregated knee to chest and lateral decubitus into one category, as in our division it is used interchangeably although the EMR lists them as separate options.

Baseline descriptive information collected included admission/dis- charge rate, primary discharge diagnosis, age, length of stay, and anes- thetic use. For the purposes of our analysis, we defined atraumatic taps as <500 RBCs [18]. We included a secondary analysis with a more generous definition of <10,000 RBCs to compare to previous studies [4,6,17]. overall success rates and proportion of atraumatic taps in the seated and lateral positions were compared using either Fisher’s exact test or Chi-square test. We defined adequacy of CSF quantity as the abil- ity perform all standard commonly ordered tests – cell count, culture, and PCR with documented results. An unsuccessful LP was one with

no CSF studies sent while an inadequate LP was one in which only the CSF culture was sent and not ancillary tests such as CSF PCR. If an LP was performed without sufficient quantity for a test to result it was con- sidered unsuccessful.

Multiple attempts were classified by their final position documented in the chart as not all individual attempts were consistently docu- mented. Based on previous studies unsuccessful/traumatic LP rate in ne- onates was 33% [5,16]; therefore, using a two-group chi-squared test with a 5% two-sided significance level will have 80% power to detect 20% absolute difference with a sample size of 69 in each group. The Northwell Institutional Review approved this study.

  1. Results

A total of 557 charts were reviewed, with 116 in the sitting position and 441 in the lateral recumbent position (Fig. 1). Overall the mean age was 31.4 +- 18.7 days with the youngest patient being 2.8 days and oldest included patient 91.6 days. The admission rate for the population was 93.0% while discharge rate was 6.6% and transfer rate was 0.4%. The median (first quartile – third quartile) length of stay within the PED was

3.8 (2.8-5.3) hours. The most commonly indicated discharge diagnosis

was acute febrile illness (26.4%). Topical anesthesia was the most com- monly used anesthetic (62.8%) followed by injectable (10.1%). Both were used in 0.5% of the subjects and none/unspecified was indicated in 26.5% of the patients’ charts.

Complications of the lumbar puncture was noted in 2.9% of the charts and largely included bleeding (1.4%). The overall incidence of Bacterial meningitis was 0.9% and viral meningitis was 11.9% (con- firmed by CSF Culture or CSF PCR). Breakdown of baseline descriptive characteristics of each group are included in Table 1.

The primary outcome of adequate CSF fluid collection as determined by results of requested studies was not significantly different between the two positions as indicated in Table 2 (p = 0.22). Although there was a decreased number of LPs with no CSF collection in the sitting po- sition versus the lateral recumbent (0.9% vs. 3.9%), this was not statisti- cally significant. The secondary outcome of proportion of atraumatic LPs defined as RBCs <500 failed to show a significant difference between positions (p = 0.83). Our secondary analysis using RBCs <10,000 to de- fine atraumatic taps also yielded no significant difference between posi- tions (p = 0.6). It should be noted that 11% of the charts were not included in this secondary analysis as they did not have RBC data and were part of the unsuccessful LP group.

When analyzing the three primary outcome groups (adequate, inadequate and no CSF collection), those with adequate CSF underwent

557 LPs


116 Sitting

441 Lateral Recumbent

73 (63%)

adequate CSF

42 (36%)



1 (0%)

no CSF

255 (58%)

adequate CSF

169 (38%)



17 (4%)

no CSF

LP – Lumbar Puncture CSF – Cerebrospinal Fluid

Fig. 1. Flow chart of CSF collection.

Table 1

Descriptive characteristics of cohort (n = 557).


(N = 116)

Disposition Admission Rate

95.7% (111)

92.3% (407)


Transfer Rate

0.9% (1)

0.2% (1)

Discharge Rate

3.5% (4)

7.5% (33)

Mean Age (days) +- SD

34.2 +- 18.8

30.7 +- 18.6


Median Hours of Stay (q1-q3)

3.8 (2.6-5.1)

3.8 (2.9-5.3)




66.3% (77)

61.5% (271)



13.0% (15)

9.5% (42)


20.9% (24)

28.3% (125)

SD: Standard deviation.

q1-q3: first quartile to third quartile.

Lateral Recumbent P

(N = 441)

antibiotics. We have a slightly older mean age of 31.4 days owing to our protocol on febrile infants aged 29-56 days of age. After an initial work up of blood and urine if a patient fails to meet low risk criteria, a lumbar puncture is recommended. Patients are admitted following and the decision to treat with antibiotics depends on the appearance of the infant.

Limitations to this study include a lack of appropriate documenta- tion in regards to number of attempts, skill level of those performing the attempt, and anesthetic use. It has been shown in literature that epidural hematomas are common after LP attempts and therefore can affect likelihood of subsequent traumatic taps [21]. It would have been helpful to know if position might affect the number of attempts conducted. Level of expertise of the practitioner who performed the LP could also have been helpful to know, to ensure one group did not

have practitioners with more experience affecting LP success. However,

* Note three subjects missing anesthetic use status were excluded from calculation.

2.4 +- 1.3 attempts. Those with inadequate CSF underwent 2.7 +- 1.2 attempts and those with no CSF underwent 4.3 +- 1.5. Of note only 10% of the charts reviewed indicated number of attempts (11 in sitting and 45 in lateral recumbent). To assess for potential bias, number of at- tempts performed was compared between the LP positions, which yielded a non-significant result (p = 0.82); thus, failing to provide enough evidence to suggest that number of attempts differed according to LP position.

  1. Discussion

This study found no statistical difference in the primary objective of adequate CSF collection between the sitting and lateral recumbent posi- tions. The secondary outcome of proportion of atraumatic LPs between the two positions was also was no different between the two positions. The current data on positioning and LP success in infants is limited and controversial. Prior studies have lacked adequate numbers of in- fants, especially in the sitting position, to conclusively identify a differ- ence [4,16,17,19]. One of the strengths of our study was attaining an adequate sample size of infants in both LP positions, but we still ob- served no significant difference among the two positions. Previous stud- ies claim physician familiarity with positioning as a limitation because more providers are biased toward success in the lateral recumbent po- sition. Hanson et al. conducted a randomized control study in regard to LP position showing no difference in success between the two posi- tions but acknowledged a lack of familiarity with sitting position among practitioners as a weakness [17]. Our study captured providers performing LPs in the position they are naturally most comfortable

eliminating this concern as a limitation.

Our study also captures a wide range of patients from 2.8 days to

91.6 days. This in part due to our institution’s policy on evaluation and management of a febrile neonates/infants. It is well accepted that those <29 days with a fever will receive a lumbar puncture and

Table 2

Success of lumbar puncture in sitting and Lateral recumbent positions.

our site is a tertiary training center where trainees, mostly senior resi- dents and first year fellows, perform the majority of procedures so a significant difference among skill level is unlikely. Unfortunately given this study was a retrospective study the level of expertise is im- possible to surmise with missing data. Finally, while we were able to determine anesthesia use in the majority of cases, about 20-30% of the charts in both groups did not indicate which or if any anesthetic used. While lack of anesthesia use has been shown to increase the risk of traumatic/unsuccessful LPs, both groups did not differ statisti- cally in anesthetic use in our study [8]. It is common practice to use Topical anesthetic at our institution so it is likely the lack of anesthesia is due to omission in documentation rather than practice. Given this is a retrospective chart review, missing or unreliable data likely intro- duced selection bias and unmeasured confounders that may have influ- enced our results.

Overall, this study failed to provide sufficient evidence that position- ing during a LP in infants <92 days has an effect on success rates or rates of atraumatic LP with an adequate sample size. Given this is a retrospec- tive study, future directives should focus on large population prospec- tive randomized controlled studies on neonates to further investigate these findings.

CRediT authorship contribution statement

Roshni Patel Bhagat: Writing – review & editing, Project adminis- tration, Methodology, Investigation, Data curation, Conceptualization, Writing – original draft. Maire Amlicke: Investigation, Project adminis- tration. Frances Steele: Project administration, Investigation. Joanna Fishbein: Data curation, Formal analysis. Matthew Kusulas: Writing – review & editing, Supervision, Methodology, Conceptualization.


William Krief, M.D. for his advice with revisions and editing of this manuscript.

Previously Presented at American College of Emergency Physicians October 2020.


  1. Procter C, Buys H, Carrara H, et al. Risk factors for unsuccessful lumbar puncture in


(N = 116)

Lateral Recumbent (N = 441)


children. S Afr Med J. 2016;106:1230-5.

  1. Bonadio W. Pediatric lumbar puncture and Cerebrospinal fluid analysis. J Emerg

LP Success


Med. 2014;46:141-50.

Adequate CSF

62.9% (73)

57.8% (255)

[3] Sahin SH, Colak A, Arar C, et al. Modified 45-degree head-up tilt increases success

Inadequate CSF

36.2% (42)

38.3% (169)

rate of lumbar puncture in patients undergoing Spinal anesthesia. J Anesth. 2014;

LP – Lumbar Puncture. CSF – Cerebrospinal Fluid. RBC – Red Blood Cell.


0.9% (1)

3.9% (17)

Atraumatic LP

<500 RBCs

72% (72)

73% (287)


<10,000 RBCs

86% (86)

87% (345)



  1. Nigrovic LE, Kuppermann N, Neuman MI. Risk factors for traumatic or unsuccessful lumbar punctures in children. Ann Emerg Med. 2007;49:762-71.
  2. Glatstein MM, Zucker-Toledano M, Arik A, et al. Incidence of traumatic lumbar punc- ture: experience of a large, tertiary care pediatric hospital. Clin Pediatr. 2011;50: 1005-9.
  3. Bonadio W. Interpreting the traumatic lumbar puncture. Contemp Pediatr. 1989;6: 109-16.
  4. Mayefsky JH, Roghmann KJ. Determination of leukocytosis in traumatic spinal tap specimens. Am J Med. 1987;82:1175-81.
  5. Mazor SS, McNulty JE, Roosevelt GE. Interpretation of traumatic lumbar punctures: who can go home? Pediatrics. 2003;111:525-8.
  6. Cunha BA. Antibiotic side effects. Med Clin North Am. 2001 Jan;85(1):149-85.
  7. Wang VJ. Pediatric procedures: Lumbar puncture in children. In: Tintinalli JE, Stephan J, editors. Tintinalli’s emergency medicine: A comprehensive study guide. McGraw-Hill Medical; 2011.
  8. Abo A, Chen L, Johnston P, et al. Positioning for lumbar puncture in children evalu- ated by bedside ultrasound. Pediatrics. 2010;125:1149-53.
  9. Sandoval M, Shestak W, Sturmann K, et al. Optimal patient position for lumbar punc- ture, measured by ultrasonography. Emerg Radiol. 2004;10:179-81.
  10. Fisher A, Lupu L, Gurevitz B, et al. Hip flexion and lumbar puncture: a radiological study. Anaesthesia. 2001;56:262-6.
  11. Oncel S, Gunlemez A, Anik Y, et al. Positioning of infants in the neonatal intensive care unit for lumbar puncture as determined by bedside ultrasonography. Arch Dis Child Fetal Neonatal Ed. 2013;98:133-5.
  12. Weisman LE, Merenstein GB, Steenbarger JR. The effect of lumbar puncture position in sick neonates. Am J Dis Child. 1983;137:1077-9.
  13. Hanson AL, Ros S, Soprano J. Analysis of infant lumbar puncture success rates: sitting

flexed versus lateral flexed positions. Pediatr Emerg Care. 2014;30:311-4.

  1. Hanson AL, Schunk JE, Corneli HM, et al. A randomized controlled trial of positioning for lumbar puncture in young infants. Pediatr Emerg Care. 2016;32:504-7.
  2. Greenberg RG, Smith PB, Cotten CM, et al. Traumatic lumbar punctures in neonates: test performance of the cerebrospinal fluid white blood cell count. Pediatr Infect Dis

J. 2008;27:1047-51.

  1. Baxter AL, Fisher RG, Burke BL, et al. Local anesthetic and stylet styles: factors asso- ciated with resident lumbar puncture success. Pediatrics. 2006;117:876-81.

[21] Kusulas MP, Eutsler EP, DePiero AD. Bedside ultrasound for the evaluation of epidu- ral hematoma after infant lumbar puncture. Pediatr Emerg Care. 2020;36:e508-12.

Further Reading

[20] Lo MD, Parisi MT, Brown JC, et al. Sitting or tilt position for infant lumbar puncture does not increase Ultrasound measurements of lumbar subarachnoid space width. Pediatr Emerg Care. 2013;29:588-91.