Superficial parasternal intercostal plane block: Anatomical landmark-guided technique

Dear Editor, The superficial parasternal intercostal plane block (SPIPB), formerly the pecto-intercostal fascial plane block, is a valuable addition to the anterior thoracic wall blocks. Ultrasound-guided SPIPB has proven highly effective for anteromedial chest wall analgesia, significantly reducing opioid consumption in breast surgery (as a supplementary block), cardiac surgery (midline sternotomy, sternotomy wound debridement) and anterior chest trauma (sternal fractures).[1] SPIPB offers a less-invasive, simpler and safer alternative to deeper blocks (deep parasternal intercostal plane, thoracic paravertebral or epidural blocks), minimising the risk of complications such as inadvertent injury to vessels, pleura or neuraxis.[2] SPIPB targets the anterior cutaneous branches of T2–T6 intercostal nerves, providing sensory innervation to the anteromedial chest wall, including the skin, soft tissue and sternum [Figure 1a]. In a cadaveric study, Douglas et al.[3] demonstrated that dye spread beyond the midclavicular line following SPIPB was performed 2 cm lateral to the sternal margin at the T3–4 intercostal space. Samerchua et al.[4] suggested triple injections at the second, fourth and fifth intercostal spaces to achieve a consistent dye spread over the second to sixth intercostal spaces. Song et al.[2] reported sensory loss at T1–T8 dermatomes beyond the midclavicular lines following bilateral administration of 40 ml of 0.3% ropivacaine at the third and fifth ribs. The ultrasound-guided method, refined by Fusco and colleagues from the initial description by Torre et al.,[1] involves administering local anaesthetic (LA) into the fascial plane between the pectoralis major muscle (PMM) and the external intercostal membrane or internal intercostal muscle (IIM), approximately 2–3 cm away from the lateral border of the sternum at the T3–4 intercostal space [Figure 1a]. Scimia et al.[5] suggested a modification targeting the rib to facilitate a more homogeneous and longitudinal spread into the desired fascial plane [Figure 1b]. However, limited access to ultrasound machines or trained regional anaesthesiologists could impede the widespread adoption of this innovative technique.Figure 1: SPIPB: (a) transverse cross-sectional anatomy at the T3–T4 intercostal space; (b) transverse cross-sectional anatomy at the level of third rib or costal cartilage; (c) needle entry point for landmark-guided SPIPB. Red asterisk is the needle entry point. ACN = anterior cutaneous nerve, CC = costal cartilage, IIM = internal intercostal muscle, LCN = lateral cutaneous nerve, PM = pectoralis major muscle, SPIPB = superficial parasternal intercostal plane block, TTM = transversus thoracis muscleWe propose a novel anatomical landmark-guided approach for SPIPB. The patient is positioned supine to facilitate the identification of the third rib through medial or lateral palpatory method. The lateral approach involves identifying the first intercostal space and the second rib immediately below the medial half of the clavicle. The medial approach begins by locating the manubriosternal joint or the sternal angle of Louis, corresponding to the articulation of the second costal cartilage or rib. In both approaches, subsequent counting locates the third costal cartilage or rib and traces to a point 5 cm lateral to the midline or 3 cm lateral to the lateral border of the sternum [Figure 1c]. The mobile skin, subcutaneous tissue and PMM are anchored against the underlying rib to prevent needle overshooting and potential injuries to internal thoracic vessels, pleura, lung or mediastinum. Under aseptic conditions, a nerve block needle (22 gauge, 25–50 mm, short bevelled) or a blunt-tipped hypodermic needle is inserted perpendicularly through PMM until it contacts the third rib [Figure 2a]. Upon hitting the bone, the needle is slightly (1–2 mm) withdrawn to prevent periosteal injection, positioning the needle tip between PMM and the third rib [Figure 1b]. After confirming negative aspiration for blood or air, LA in 3–5 ml aliquots is administered. Depending on the indications, 15–20 ml of LA can be administered unilaterally or bilaterally. The backflow of LA upon syringe disconnection may indicate proper drug deposition [Figure 2b]. Based on the injected volume, LA disperses over several intercostal levels in the craniocaudal and mediolateral directions.Figure 2: SPIPB: (a) Patient position and direction of needle insertion. (b) Post-block ultrasound image showing sonoanatomy and LA spread. (c) Schematic diagram of the anterior chest wall showing distribution of intercostal nerves, internal thoracic (mammary) vessels, and needle entry point. ACN = anterior cutaneous nerve, LA = local anaestheticWhile executing the block, it is crucial to exercise caution regarding the internal thoracic (mammary) vessels. They run bilaterally, parallel to the sternal margin within 2 cm, between IIM and the transversus thoracis muscle [Figure 2c]. From the second to sixth intercostal space, the vessels lie medial to the midpoint between the sternal border and the costochondral junction.[3] To minimise the risk of injury to the costal cartilage or internal thoracic vessels, select a needle entry point at least 3 cm lateral to the sternal margin and 5 cm from the midline. This precaution is crucial due to the progressive increase in the length of the costal cartilage towards the lower intercostal spaces. Landmark-guided SPIPB may not be suitable for obese patients, large breasts or excess parasternal fatty tissue, as precise needle positioning over the rib can be difficult. Further clinical studies are warranted to validate its efficacy, safety and reliability compared to the ultrasound-guided techniques. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.