Description

Video-assisted thoracoscopic surgeries (VATS) are currently the preferred technique for treating carcinoma lung. Despite being minimally invasive, VATS is associated with significant acute and chronic postoperative pain. Regional anesthetic techniques have the potential to block afferent nociception at the peripheral nerve level, the dorsal root ganglion (DRG), the thoracic sympathetic ganglion, or through a combination of these mechanisms. While the peripheral nerve block techniques such as the intercostal nerve block and serratus anterior plane block can provide analgesia for port related somatic pain, the visceral pain mediated via the thoracic sympathetic chain during VATS procedure are amenable only to epidural or paravertebral regional anaesthetic techniques. The thoracic paravertebral block (TPVB) provides ipsilateral, segmental, somatic, and sympathetic nerve blockade across multiple contiguous thoracic dermatomes and is currently the first choice for VATS. During a TPVB, the local anaesthetic (LA) is injected into the paravertebral space adjacent to the thoracic vertebra, near the intervertebral foramen.

Traditionally, TPVB is performed using either landmark or ultrasound guidance, with the LA deposited anterior to the superior costotransverse ligament (SCTL). This typically involves the block needle piercing the SCTL to reach the wedge-shaped TPVB space. While Thoracic Paravertebral Block (TPVB) is generally regarded as safe, the proximity of the needle tip to the pleura during injection poses a heightened risk of pleural puncture and pneumothorax, especially when administered by less experienced physicians. Consequently, the Erector Spinae Plane Block (ESPB) is gaining popularity as an alternative. However, it is important to note that ESPB also has its own limitations.

Recent advancements have redefined thoracic paravertebral anatomy, identifying a fat-filled retro-SCTL space located behind the SCTL. This space is farther from the pleura but remains in close proximity to anterior neural targets such as the thoracic spinal nerve, the DRG and thoracic sympathetic ganglion. It is hypothesised that an LA injection into the retro-SCTL space-referred to as the Intertransverse Process Block (ITPB) at the medial retro SCTL space-could produce a rapid onset of ipsilateral and/or bilateral segmental somatic and sympathetic nerve blockade of the thoracic dermatomes without the need to pierce the SCTL, thereby reducing the risk of pleural puncture and pneumothorax. Preliminary investigations on the ITPB for VATS is promising, however, there is a paucity of data on the effect of the number of injections following an ultrasound-guided (USG) ITPB on the analgesic efficacy, which this study aims to evaluate.