Dear Editor,
The preprocedural ultrasound-assisted (PPUSa) technique has been a boon for achieving central neuraxial block (CNB) with improved first pass success and decreased needle puncture attempts.[1] Different PPUSa approaches have been described in literature; median, paramedian and paraspinous,[2,3] to reach the neuraxial space, enhancing success and patient satisfaction. We describe an innovative modification in the PPUSa CNB technique called the PPUSa parasagittal interlaminar (PSIL) approach.
In the PPUSa technique for CNB described by Kalagar et al.,[3] the spinal interlaminar (IL) spaces of desired level L4–L5/L3–L4 are marked in the sitting position, using a low frequency curvilinear probe with parasagittal oblique (PSO) orientation, after sequentially identifying the transverse, articular and laminar processes. The anterior complex (AC) and the posterior complex (PC) can be appreciated in the parasagittal oblique–interlaminar (PSO-IL) view [Figure 1]. The midpoint of the probe was used to mark line 1, using the M-mode (or the centre-line feature, available in newer machines). The PSO-IL view is also used to measure the skin-to-PC distance (depth). The probe is placed in the transverse view to identify the spinous process and mark the midline of the spine, as line 2 at the midpoint of the probe. The junction of lines 1 and 2, midline interlaminar (MIL), is the needle entry point for the median approach to PPUSa CNB.[3] With advancing age, obesity or during pregnancy, exaggerated lumbar lordosis and calcification of ligaments, CNB with the MIL approach becomes difficult. The paramedian interlaminar (PMIL) approach, with needle entry 1–2 cm away from the MIL, has been found to have higher first pass success, with evidence of fewer needle re-directions and lower incidence of post-dural puncture headache (PDPH).[4,5] However, the PMIL approach has a large arc of guesswork due to the large footprint of the probe and the angle of beam insinuation, which can lead to multiple angle redirections. Hence, we innovated a PPUSa–PSIL approach, where the needle is entered 0.5 cm lateral to the MIL needle entry point, an approach that overcomes the disadvantages of the PMIL with advantages of the MIL approach[2] [Figure 2].
Figure 1.
Para-sagittal and transverse scanning sequence with graphic depiction of the probe position and sonoanatomy. Graphical description of the needle directions in the MIL: Midline interlaminar, PSIL: Parasagittal interlaminar, PMIL: Paramedian interlaminar approaches.
Figure 2.
Sequence of markings to achieve the desired parasagittal interlaminar (PSIL) point of injection. PSO: Parasagittal oblique view, Transverse: Transverse view, MIL: Midline interlaminar, PSIL: Parasagittal Interlaminar, PMIL: Paramedial Interlaminar approaches entry point.
Earlier, Kumar et al.[6] reported the use of the PSIL approach for epidural steroid injections in chronic pain intervention; nevertheless, a PPUSa approach can be an objective guide to test its efficacy in CNB. After obtaining written informed consent, we performed CNB in 30 patients, belonging to American Society of Anesthesiologists (ASA) physical status class I–II, aged 55–75 years and of either gender, posted for unilateral total knee replacement (TKR) planned under spinal anaesthesia. Spinal anaesthesia using 0.5% bupivacaine heavy, with a 25-gauge Quincke–Babcock spinal (QBS) needle, at the L4–L5 interspace was performed by the same anaesthesiologist using the PPUSa–PSIL approach. The first pass success rate determined by reaching the subarachnoid space (free flow of cerebrospinal fluid) in a single attempt was achieved in 24 (80%) patients, one needle redirection was needed in 1 (3.33%) patient and two needle redirections were needed in 2 (6.67%) patients. Three or more needle redirections (considered as failure of the approach) were observed in 3 (10%) patients. The PPUSa–PSIL approach appears to be an easy, reproduceable and promising technique for ultrasound-assisted CNB, with potential to improve success rates and patient outcomes. Larger studies are needed to establish its efficacy.
Author contributions
RR, GA: Concept, design, literature search, conducting the study work, manuscript editing. ASS: Literature search, conducting the study work, manuscript preparation and editing. All the authors have participated in the review, drafting and final approval of the manuscript.
Disclosure of use of artificial intelligence (AI)-assistive or generative tools
No artificial intelligence was used for manuscript preparation except for Grammarly for academic language editing.
Declaration of use of permitted tools
Raster graphics editor, Paint 3D, application for Windows 11, version 24H2 (Microsoft) was used to create the figure.
Conflicts of interest
There are no conflicts of interest.
Acknowledgement
Nil.
Funding Statement
Nil.
REFERENCES
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